Journal articles on the topic 'Recent past and future sea-level changes'
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1
Timmermann, Axel, Shayne McGregor, and Fei-Fei Jin. "Wind Effects on Past and Future Regional Sea Level Trends in the Southern Indo-Pacific*." Journal of Climate 23, no. 16 (August 15, 2010): 4429–37. http://dx.doi.org/10.1175/2010jcli3519.1.
Abstract:
Abstract Global sea level rise due to the thermal expansion of the warming oceans and freshwater input from melting glaciers and ice sheets is threatening to inundate low-lying islands and coastlines worldwide. At present the global mean sea level rises at 3.1 ± 0.7 mm yr−1 with an accelerating tendency. However, the magnitude of recent decadal sea level trends varies greatly spatially, attaining values of up to 10 mm yr−1 in some areas of the western tropical Pacific. Identifying the causes of recent regional sea level trends and understanding the patterns of future projected sea level change is of crucial importance. Using a wind-forced simplified dynamical ocean model, the study shows that the regional features of recent decadal and multidecadal sea level trends in the tropical Indo-Pacific can be attributed to changes in the prevailing wind regimes. Furthermore, it is demonstrated that within an ensemble of 10 state-of-the-art coupled general circulation models, forced by increasing atmospheric CO2 concentrations over the next century, wind-induced redistributions of upper-ocean water play a key role in establishing the spatial characteristics of projected regional sea level rise. Wind-related changes in near-surface mass and heat convergence near the Solomon Islands, Tuvalu, Kiribati, the Cook Islands, and French Polynesia oppose—but cannot cancel—the regional signal of global mean sea level rise.
2
Zanchettin, Davide, Sara Bruni, Fabio Raicich, Piero Lionello, Fanny Adloff, Alexey Androsov, Fabrizio Antonioli, et al. "Sea-level rise in Venice: historic and future trends (review article)." Natural Hazards and Earth System Sciences 21, no. 8 (September 1, 2021): 2643–78. http://dx.doi.org/10.5194/nhess-21-2643-2021.
Abstract:
Abstract. The city of Venice and the surrounding lagoonal ecosystem are highly vulnerable to variations in relative sea level. In the past ∼150 years, this was characterized by an average rate of relative sea-level rise of about 2.5 mm/year resulting from the combined contributions of vertical land movement and sea-level rise. This literature review reassesses and synthesizes the progress achieved in quantification, understanding and prediction of the individual contributions to local relative sea level, with a focus on the most recent studies. Subsidence contributed to about half of the historical relative sea-level rise in Venice. The current best estimate of the average rate of sea-level rise during the observational period from 1872 to 2019 based on tide-gauge data after removal of subsidence effects is 1.23 ± 0.13 mm/year. A higher – but more uncertain – rate of sea-level rise is observed for more recent years. Between 1993 and 2019, an average change of about +2.76 ± 1.75 mm/year is estimated from tide-gauge data after removal of subsidence. Unfortunately, satellite altimetry does not provide reliable sea-level data within the Venice Lagoon. Local sea-level changes in Venice closely depend on sea-level variations in the Adriatic Sea, which in turn are linked to sea-level variations in the Mediterranean Sea. Water mass exchange through the Strait of Gibraltar and its drivers currently constitute a source of substantial uncertainty for estimating future deviations of the Mediterranean mean sea-level trend from the global-mean value. Regional atmospheric and oceanic processes will likely contribute significant interannual and interdecadal future variability in Venetian sea level with a magnitude comparable to that observed in the past. On the basis of regional projections of sea-level rise and an understanding of the local and regional processes affecting relative sea-level trends in Venice, the likely range of atmospherically corrected relative sea-level rise in Venice by 2100 ranges between 32 and 62 cm for the RCP2.6 scenario and between 58 and 110 cm for the RCP8.5 scenario, respectively. A plausible but unlikely high-end scenario linked to strong ice-sheet melting yields about 180 cm of relative sea-level rise in Venice by 2100. Projections of human-induced vertical land motions are currently not available, but historical evidence demonstrates that they have the potential to produce a significant contribution to the relative sea-level rise in Venice, exacerbating the hazard posed by climatically induced sea-level changes.
3
Aucelli, Pietro P. C., Giuseppe Mastronuzzi, and Gaia Mattei. "Relative Sea-Level Changes and Their Impact on Coastal Zones: Past and Future Scenarios from Cases Studies around the World." Water 14, no. 11 (June 6, 2022): 1822. http://dx.doi.org/10.3390/w14111822.
Abstract:
In recent decades, the study of sea-level changes as recorded along entire coastlines around the world has been a primary scientific focus in climate change studies; it allows the exploration of past landscape evolution, geomorphological processes, human impact, and system response to develop future perspectives [...]
4
Miles, Bertie W. J., Jim R. Jordan, Chris R. Stokes, Stewart S. R. Jamieson, G. Hilmar Gudmundsson, and Adrian Jenkins. "Recent acceleration of Denman Glacier (1972–2017), East Antarctica, driven by grounding line retreat and changes in ice tongue configuration." Cryosphere 15, no. 2 (February 11, 2021): 663–76. http://dx.doi.org/10.5194/tc-15-663-2021.
Abstract:
Abstract. After Totten, Denman Glacier is the largest contributor to sea level rise in East Antarctica. Denman's catchment contains an ice volume equivalent to 1.5 m of global sea level and sits in the Aurora Subglacial Basin (ASB). Geological evidence of this basin's sensitivity to past warm periods, combined with recent observations showing that Denman's ice speed is accelerating and its grounding line is retreating along a retrograde slope, has raised the prospect that its contributions to sea level rise could accelerate. In this study, we produce the first long-term (∼50 years) record of past glacier behaviour (ice flow speed, ice tongue structure and calving) and combine these observations with numerical modelling to explore the likely drivers of its recent change. We find a spatially widespread acceleration of the Denman system since the 1970s across both its grounded (17±4 % acceleration; 1972–2017) and floating portions (36±5 % acceleration; 1972–2017). Our numerical modelling experiments show that a combination of grounding line retreat, ice tongue thinning and the unpinning of Denman's ice tongue from a pinning point following its last major calving event are required to simulate an acceleration comparable with observations. Given its bed topography and the geological evidence that Denman Glacier has retreated substantially in the past, its recent grounding line retreat and ice flow acceleration suggest that it could be poised to make a significant contribution to sea level in the near future.
5
Kalaugher, P. G., and P. Grainger. "The influence of changes in sea level on coastal cliff instability in Devon." Geological Society, London, Engineering Geology Special Publications 7, no. 1 (1991): 361–67. http://dx.doi.org/10.1144/gsl.eng.1991.007.01.31.
Abstract:
AbstractMajor variations in sea level have resulted from climatic changes during the Quaternary. In addition, beyond the maximum limit of glaciation, periglacial climates in southern Britain have produced Quaternary deposits which can affect the nature of coastal slopes and their response to marine erosion. Examples are given of cliffs in head (solifluction) deposits which overlie raised shore platforms in Devon. The present styles and distribution of coastal landslide hazards, recorded in recent surveys, are directly related to past Quaternary sea levels and climatic fluctuations. Future trends in relative sea level are a significant factor in the determination of the hazards in the longer term, as there could be changes in the level at which marine erosion is effective. Rankings of the hazards, which should in any case be updated routinely by repeated monitoring of the landslide activity, ought to reflect expected changes in sea level.
6
Perisoratis, Constantinos. "Climate change in the recent geological past and the near future. Predicting its impacts: a Review." Bulletin of the Geological Society of Greece 55, no. 1 (December 18, 2019): 260. http://dx.doi.org/10.12681/bgsg.20684.
Abstract:
The climate changes are necessarily related to the increase of the Earth’s temperature, resulting in a sea level rise. Such continuous events, were taking place with minor and greater intensity, during the alternation of warm and cool periods in the Earth during the Late Quaternary and the Holocene periods. However, a particularly significant awareness has taken place in the scientific community, and consequently in the greater public, in the last decades: that a climatic change will take place soon, or it is on-going, and that therefore it is important to undertake drastic actions. However, such a climatic change has not been recorded yet, and hence the necessary actions are not required, for the time being.
7
Crosta, Xavier, Karen E. Kohfeld, Helen C. Bostock, Matthew Chadwick, Alice Du Vivier, Oliver Esper, Johan Etourneau, et al. "Antarctic sea ice over the past 130 000 years – Part 1: a review of what proxy records tell us." Climate of the Past 18, no. 8 (August 2, 2022): 1729–56. http://dx.doi.org/10.5194/cp-18-1729-2022.
Abstract:
Abstract. Antarctic sea ice plays a critical role in the Earth system, influencing energy, heat and freshwater fluxes, air–sea gas exchange, ice shelf dynamics, ocean circulation, nutrient cycling, marine productivity and global carbon cycling. However, accurate simulation of recent sea-ice changes remains challenging and, therefore, projecting future sea-ice changes and their influence on the global climate system is uncertain. Reconstructing past changes in sea-ice cover can provide additional insights into climate feedbacks within the Earth system at different timescales. This paper is the first of two review papers from the Cycles of Sea Ice Dynamics in the Earth system (C-SIDE) working group. In this first paper, we review marine- and ice core-based sea-ice proxies and reconstructions of sea-ice changes throughout the last glacial–interglacial cycle. Antarctic sea-ice reconstructions rely mainly on diatom fossil assemblages and highly branched isoprenoid (HBI) alkenes in marine sediments, supported by chemical proxies in Antarctic ice cores. Most reconstructions for the Last Glacial Maximum (LGM) suggest that winter sea ice expanded all around Antarctica and covered almost twice its modern surface extent. In contrast, LGM summer sea ice expanded mainly in the regions off the Weddell and Ross seas. The difference between winter and summer sea ice during the LGM led to a larger seasonal cycle than today. More recent efforts have focused on reconstructing Antarctic sea ice during warm periods, such as the Holocene and the Last Interglacial (LIG), which may serve as an analogue for the future. Notwithstanding regional heterogeneities, existing reconstructions suggest that sea-ice cover increased from the warm mid-Holocene to the colder Late Holocene with pervasive decadal- to millennial-scale variability throughout the Holocene. Studies, supported by proxy modelling experiments, suggest that sea-ice cover was halved during the warmer LIG when global average temperatures were ∼2 ∘C above the pre-industrial (PI). There are limited marine (14) and ice core (4) sea-ice proxy records covering the complete 130 000 year (130 ka) last glacial cycle. The glacial–interglacial pattern of sea-ice advance and retreat appears relatively similar in each basin of the Southern Ocean. Rapid retreat of sea ice occurred during Terminations II and I while the expansion of sea ice during the last glaciation appears more gradual especially in ice core data sets. Marine records suggest that the first prominent expansion occurred during Marine Isotope Stage (MIS) 4 and that sea ice reached maximum extent during MIS 2. We, however, note that additional sea-ice records and transient model simulations are required to better identify the underlying drivers and feedbacks of Antarctic sea-ice changes over the last 130 ka. This understanding is critical to improve future predictions.
8
Holt, J., M. Butenschön, S. L. Wakelin, Y. Artioli, and J. I. Allen. "Oceanic controls on the primary production of the northwest European continental shelf under recent past and potential future conditions." Biogeosciences Discussions 8, no. 4 (August 19, 2011): 8383–422. http://dx.doi.org/10.5194/bgd-8-8383-2011.
Abstract:
Abstract. In this paper we clearly demonstrate that changes in oceanic nutrients are a first order factor in determining changes in the primary production of the northwest European continental shelf on time scales of 5–10 yr. We present a series of coupled hydrodynamic ecosystem modelling simulations, using the POLCOMS-ERSEM system. These are forced by both re-analysis data and a coupled ocean-atmosphere general circulation model (OA-GCM) representative of possible conditions in 2080–2100 under an SRES A1B emissions scenario, along with the corresponding present day control. The OA-GCM forced simulations show a substantial reduction in surface nutrients in the open-ocean regions of the model domain, comparing future and present day time-slices. This arises from a large increase in oceanic stratification. Tracer transport experiments identify a substantial fraction of on-shelf water originates from the open-ocean region in the south of the domain, where this increase is largest, and indeed the on-shelf nutrient and primary production are reduced as this water is transported on shelf. This relationship is confirmed quantitatively by comparing changes in winter nitrate with total annual nitrate uptake. The reduction in primary production by the reduced nutrient transport is mitigated by on-shelf processes relating to temperature, stratification (length of growing season) and recycling. Regions less exposed to ocean-shelf exchange in this model (Celtic Sea, Irish Sea, English Channel, and southern North Sea) show a modest increase in primary production (of 5–10 %) compared with a decrease of 0–20 % in the outer shelf, central and northern North Sea. These findings are backed up by a boundary condition perturbation experiment and a simple mixing model.
9
Paeth, Heiko, and Felix Pollinger. "Revisiting the spatiotemporal characteristics of past and future global warming." ERDKUNDE 74, no. 4 (December 31, 2020): 225–47. http://dx.doi.org/10.3112/erdkunde.2020.04.01.
Abstract:
It is still an open question, which processes lead to the spatiotemporal specifications of observed near-surface temperature changes over recent decades. Here, we contribute to this debate by investigating a large number of theory-based atmospheric fields referring to the radiation and energy budget and to atmospheric dynamics that may serve as predictors for local temperature changes. The predictors are linked to temperature trends from reanalysis and climate model data, using a sophisticated spatial and temporal statistical model. Temperature changes since the mid-20th century exhibit distinct regional and seasonal differences. After 1990, the near-surface warming rate is more enhanced over landmasses rather than oceans and roughly increases with latitude in both hemispheres. While none of the considered predictors solitarily accounts for the spatial heterogeneity of recent temperature trends, their linear combination largely reproduces the observed cooling pattern during the mid-20th century and the enhanced warming pattern after 1990. This excludes high-altitude areas, sea ice margins and upwelling regions where local feedbacks and nonlinear processes prevail. The leading predictors pertain to radiative processes, especially downward longwave radiation, and changes in sensible heat fluxes. In the low latitudes, dynamical processes such as temperature advection and energy flux divergence also play a role. Until the end of the 21st century, the warming rate and its ocean-land contrast steadily increase. The underlying mechanisms are the same as the ones already established in present-day climate, but near-surface temperature follows more straightly the imposed greenhouse gas scenario. Climate models have different skills in reproducing the observed trend pattern but exhibit more or less the same mechanisms of temperature control.
10
Holland, Paul R., Gemma K. O'Connor, Thomas J. Bracegirdle, Pierre Dutrieux, Kaitlin A. Naughten, Eric J. Steig, David P. Schneider, Adrian Jenkins, and James A. Smith. "Anthropogenic and internal drivers of wind changes over the Amundsen Sea, West Antarctica, during the 20th and 21st centuries." Cryosphere 16, no. 12 (December 22, 2022): 5085–105. http://dx.doi.org/10.5194/tc-16-5085-2022.
Abstract:
Abstract. Ocean-driven ice loss from the West Antarctic Ice Sheet is a significant contributor to sea-level rise. Recent ocean variability in the Amundsen Sea is controlled by near-surface winds. We combine palaeoclimate reconstructions and climate model simulations to understand past and future influences on Amundsen Sea winds from anthropogenic forcing and internal climate variability. The reconstructions show strong historical wind trends. External forcing from greenhouse gases and stratospheric ozone depletion drove zonally uniform westerly wind trends centred over the deep Southern Ocean. Internally generated trends resemble a South Pacific Rossby wave train and were highly influential over the Amundsen Sea continental shelf. There was strong interannual and interdecadal variability over the Amundsen Sea, with periods of anticyclonic wind anomalies in the 1940s and 1990s, when rapid ice-sheet loss was initiated. Similar anticyclonic anomalies probably occurred prior to the 20th century but without causing the present ice loss. This suggests that ice loss may have been triggered naturally in the 1940s but failed to recover subsequently due to the increasing importance of anthropogenic forcing from greenhouse gases (since the 1960s) and ozone depletion (since the 1980s). Future projections also feature strong wind trends. Emissions mitigation influences wind trends over the deep Southern Ocean but has less influence on winds over the Amundsen Sea shelf, where internal variability creates a large and irreducible uncertainty. This suggests that strong emissions mitigation is needed to minimise ice loss this century but that the uncontrollable future influence of internal climate variability could be equally important.
11
Ganea, Daniel, Elena Mereuta, and Liliana Rusu. "Estimation of the Near Future Wind Power Potential in the Black Sea." Energies 11, no. 11 (November 18, 2018): 3198. http://dx.doi.org/10.3390/en11113198.
Abstract:
The main objective of the present study is to quantify the recent past and explore the near future wind power potential in the Black Sea basin, evaluating the possible changes. Furthermore, an analysis of the wind climate in the target area was also performed. The wind resources have been assessed using the wind fields provided by various databases. Thus, the wind power potential from the recent past was assessed based two different sources covering each one the 30-year period (1981–2010). The first source is the ERA-Interim atmospheric reanalysis provided by the European Centre for Medium-Range Weather Forecasts (ECMWF), while the second source represents the hindcast wind fields simulated by a Regional Climate Model (RCM) and provided by EURO-CORDEX databases. The estimation of the near future wind power potential was made based on wind fields simulated by the same RCM under future climate projections, considering two Representative Concentration Pathways (RCPs) scenarios (RCP4.5 and RCP8.5) and they cover also a 30-year time interval (2021–2050). Information in various reference points were analyzed in detail. Several conclusions resulted from the present work. Thus, as regards the mean wind power potential in winter season, in 51% of the locations a significant increase is projected in the near future (both scenarios). Besides providing a detailed description of the wind conditions from the recent past over the Black Sea basin considering two major sources, the novelty of the present work consists in the fact that it gives an estimation of the expected wind climate in the target area for the near future period and at the same time an evaluation of the climate change impacts on the wind speed and wind power potential.
12
Sou, Tessa, and Gregory Flato. "Sea Ice in the Canadian Arctic Archipelago: Modeling the Past (1950–2004) and the Future (2041–60)." Journal of Climate 22, no. 8 (April 15, 2009): 2181–98. http://dx.doi.org/10.1175/2008jcli2335.1.
Abstract:
Abstract Considering the recent losses observed in Arctic sea ice and the anticipated future warming due to anthropogenic greenhouse gas emissions, sea ice retreat in the Canadian Arctic Archipelago (CAA) is expected and indeed is already being observed. As most global climate models do not resolve the CAA region, a fine-resolution ice–ocean regional model is developed and used to make a projection of future changes in the CAA sea ice. Results from a historical run (1950–2004) are used to evaluate the model. The model does well in representing observed sea ice spatial and seasonal variability, but tends to underestimate summertime ice cover. The model results for the future (2041–60) show little change in wintertime ice concentrations from the past, but summertime ice concentrations decrease by 45%. The ice thickness is projected to decrease by 17% in the winter and by 36% in summer. Based on this study, a completely ice-free CAA is unlikely by the year 2050, but the simulated ice retreat suggests that the region could support some commercial shipping.
13
Miles, Bertie W. J., Chris R. Stokes, and Stewart S. R. Jamieson. "Pan–ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes." Science Advances 2, no. 5 (May 2016): e1501350. http://dx.doi.org/10.1126/sciadv.1501350.
Abstract:
The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974–1990, before switching to advance in every drainage basin during the two most recent periods, 1990–2000 and 2000–2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica.
14
Aschwanden, A., G. Aðalgeirsdóttir, and C. Khroulev. "Hindcasting to measure ice sheet model sensitivity to initial states." Cryosphere Discussions 6, no. 6 (December 6, 2012): 5069–94. http://dx.doi.org/10.5194/tcd-6-5069-2012.
Abstract:
Abstract. Recent observations of the Greenland ice sheet indicate rapid mass loss at an accelerating rate with an increasing contribution to global mean sea level. Ice sheet models are used for projections of such future contributions of ice sheets to sea level, but the quality of projections is difficult to measure directly. Realistic initial states are crucial for accurate simulations. To test initial states we use hindcasting, i.e. forcing a model with known or closely-estimated inputs for past events to see how well the output matches observations. By simulating the recent past of Greenland, and comparing to observations of ice thickness, ice discharge, surface speeds, mass loss and surface elevation changes for validation, we find that the short term model response is strongly influenced by the initial state. We show that the dynamical state can be mis-represented despite a good agreement with some observations, stressing the importance of using multiple observations. Some initial states generate good agreement with measured mass time series in the hindcast period, and good agreement with present-day kinematic fields. We suggest hindcasting as a methodology for careful validation of initial states that can be done before making projections on decadal to century time-scales.
15
Holt, J., M. Butenschön, S. L. Wakelin, Y. Artioli, and J. I. Allen. "Oceanic controls on the primary production of the northwest European continental shelf: model experiments under recent past conditions and a potential future scenario." Biogeosciences 9, no. 1 (January 6, 2012): 97–117. http://dx.doi.org/10.5194/bg-9-97-2012.
Abstract:
Abstract. In this paper we clearly demonstrate that changes in oceanic nutrients are a first order factor in determining changes in the primary production of the northwest European continental shelf on time scales of 5–10 yr. We present a series of coupled hydrodynamic ecosystem modelling simulations, using the POLCOMS-ERSEM system. These are forced by both reanalysis data and a single example of a coupled ocean-atmosphere general circulation model (OA-GCM) representative of possible conditions in 2080–2100 under an SRES A1B emissions scenario, along with the corresponding present day control. The OA-GCM forced simulations show a substantial reduction in surface nutrients in the open-ocean regions of the model domain, comparing future and present day time-slices. This arises from a large increase in oceanic stratification. Tracer transport experiments identify a substantial fraction of on-shelf water originates from the open-ocean region to the south of the domain, where this increase is largest, and indeed the on-shelf nutrient and primary production are reduced as this water is transported on-shelf. This relationship is confirmed quantitatively by comparing changes in winter nitrate with total annual nitrate uptake. The reduction in primary production by the reduced nutrient transport is mitigated by on-shelf processes relating to temperature, stratification (length of growing season) and recycling. Regions less exposed to ocean-shelf exchange in this model (Celtic Sea, Irish Sea, English Channel, and Southern North Sea) show a modest increase in primary production (of 5–10%) compared with a decrease of 0–20% in the outer shelf, Central and Northern North Sea. These findings are backed up by a boundary condition perturbation experiment and a simple mixing model.
16
Mioduszewski, John, Stephen Vavrus, and Muyin Wang. "Diminishing Arctic Sea Ice Promotes Stronger Surface Winds." Journal of Climate 31, no. 19 (October 2018): 8101–19. http://dx.doi.org/10.1175/jcli-d-18-0109.1.
Abstract:
Projections of Arctic sea ice through the end of the twenty-first century indicate the likelihood of a strong reduction in ice area and thickness in all seasons, leading to a substantial thermodynamic influence on the overlying atmosphere. This is likely to have an effect on winds over the Arctic basin because of changes in atmospheric stability, surface roughness, and/or baroclinicity. Here we identify patterns of wind changes in all seasons across the Arctic and their likely causal mechanisms, particularly those associated with sea ice loss. Output from the Community Earth System Model Large Ensemble Project (CESM-LE) was analyzed for the recent past (primarily 1971–2000) and future (2071–2100). Mean near-surface wind speeds over the Arctic Ocean are projected to increase by late century in all seasons but especially during autumn and winter, when they strengthen by up to 50% locally. The most extreme wind speeds in the 95th percentile change even more, increasing in frequency by up to 100%. The strengthened winds are closely linked to decreasing surface roughness and lower-tropospheric stability resulting from the loss of sea ice cover and consequent surface warming (exceeding 20°C warmer in the central Arctic in autumn and winter), as well as local changes in the storm track. The implications of stronger future winds include increased coastal and navigational hazards. Our findings suggest that increasing winds, along with reduction of sea ice, rising sea level, and thawing permafrost, represent another important contributor to the growing problem of Arctic coastal erosion.
17
Zhang, Caiyun. "Responses of Summer Upwelling to Recent Climate Changes in the Taiwan Strait." Remote Sensing 13, no. 7 (April 3, 2021): 1386. http://dx.doi.org/10.3390/rs13071386.
Abstract:
The response of a summer upwelling system to recent climate change in the Taiwan Strait has been investigated using a time series of sea surface temperature and wind data over the period 1982–2019. Our results revealed that summer upwelling intensities of the Taiwan Strait decreased with a nonlinear fluctuation over the past four decades. The average upwelling intensity after 2000 was 35% lower than that before 2000. The long-term changes in upwelling intensities show strong correlations with offshore Ekman transport, which experienced a decreasing trend after 2000. Unlike the delay effect of canonical ENSO events on changes in summer upwelling, ENSO Modoki events had a significant negative influence on upwelling intensity. Strong El Niño Modoki events were not favorable for the development of upwelling. This study also suggested that decreased upwelling could not slow down the warming rate of the sea surface temperature and would probably cause the decline of chlorophyll a in the coastal upwelling system of the Taiwan Strait. These results will contribute to a better understanding of the dynamic process of summer upwelling in the Taiwan Strait, and provide a sound scientific basis for evaluating future trends in coastal upwelling and their potential ecological effects.
18
Lewis, Gabriel, Erich Osterberg, Robert Hawley, Hans Peter Marshall, Tate Meehan, Karina Graeter, Forrest McCarthy, Thomas Overly, Zayta Thundercloud, and David Ferris. "Recent precipitation decrease across the western Greenland ice sheet percolation zone." Cryosphere 13, no. 11 (November 4, 2019): 2797–815. http://dx.doi.org/10.5194/tc-13-2797-2019.
Abstract:
Abstract. The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest in the context of future sea level rise. Increased melting in the GrIS percolation zone due to atmospheric warming over the past several decades has led to increased mass loss at lower elevations. Previous studies have hypothesized that this warming is accompanied by a precipitation increase, as would be expected from the Clausius–Clapeyron relationship, compensating for some of the melt-induced mass loss throughout the western GrIS. This study tests that hypothesis by calculating snow accumulation rates and trends across the western GrIS percolation zone, providing new accumulation rate estimates in regions with sparse in situ data or data that do not span the recent accelerating surface melt. We present accumulation records from sixteen 22–32 m long firn cores and 4436 km of ground-penetrating radar, covering the past 20–60 years of accumulation, collected across the western GrIS percolation zone as part of the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) project. Trends from both radar and firn cores, as well as commonly used regional climate models, show decreasing accumulation rates of 2.4±1.5 % a−1 over the 1996–2016 period, which we attribute to shifting storm tracks related to stronger atmospheric summer blocking over Greenland. Changes in atmospheric circulation over the past 20 years, specifically anomalously strong summertime blocking, have reduced GrIS surface mass balance through both an increase in surface melting and a decrease in accumulation rates.
19
Chase-Dunn, Christopher. "Introduction to the Thematic Articles: Hegemonic Rivalry: Past and Future." Journal of World-Systems Research 1, no. 1 (August 25, 2015): 381. http://dx.doi.org/10.5195/jwsr.1995.41.
Abstract:
The international political economy has experienced a sequence of economic booms and busts, as well as periods of relative peace and world war, for the last 500 years. Capitalist industrialization has expanded productivity and integrated everlarger numbers of people into a single global economy in waves of industrialization and market expansion. These waves have been repeatedly punctuated by world wars. The current level of economic integration, and other factors, cause many students of the global system to argue that the periodic outbreak of world wars is over. This book focuses on both long run trends and recent developments in the modern world-system, and their implications for the future of humankind. Will the cycles of boom bust, peace and war continue? Or have long terms trends (or recent changes) altered the nature of thesystem sufficiently such that these oscillations will cease, or take a less destructive form?
20
Wall-Palmer, D., M. B. Hart, C. W. Smart, R. S. J. Sparks, A. Le Friant, G. Boudon, C. Deplus, and J. C. Komorowski. "Pteropods from the Caribbean Sea: dissolution as an indicator of past ocean acidification." Biogeosciences Discussions 8, no. 4 (July 13, 2011): 6901–17. http://dx.doi.org/10.5194/bgd-8-6901-2011.
Abstract:
Abstract. The aragonite shell–bearing thecosome pteropods are an important component of the oceanic plankton. However, with increasing pCO2 and the associated reduction in oceanic pH (ocean acidification), thecosome pteropods are thought to be particularly vulnerable to shell dissolution. The distribution and preservation of pteropods over the last 250,000 years have been investigated in marine sediment cores from the Caribbean Sea close to the island of Montserrat. Using the Limacina Dissolution Index (LDX), fluctuations in pteropod dissolution through the most recent glacial/interglacial cycles is documented. By comparison to the oxygen isotope record (global sea ice volume), we show that pteropod dissolution is closely linked to global changes in pCO2 and pH and is, therefore, a global signal. These data are in agreement with the findings of experiments upon living pteropods, which show that variations in pH can greatly affect aragonitic shells. The results of this study provide information which may be useful in the prediction of future changes to the pteropod assemblage caused by ocean acidification.
21
Josselyn, Sheena A., and Susumu Tonegawa. "Memory engrams: Recalling the past and imagining the future." Science 367, no. 6473 (January 2, 2020): eaaw4325. http://dx.doi.org/10.1126/science.aaw4325.
Abstract:
In 1904, Richard Semon introduced the term “engram” to describe the neural substrate for storing memories. An experience, Semon proposed, activates a subset of cells that undergo off-line, persistent chemical and/or physical changes to become an engram. Subsequent reactivation of this engram induces memory retrieval. Although Semon’s contributions were largely ignored in his lifetime, new technologies that allow researchers to image and manipulate the brain at the level of individual neurons has reinvigorated engram research. We review recent progress in studying engrams, including an evaluation of evidence for the existence of engrams, the importance of intrinsic excitability and synaptic plasticity in engrams, and the lifetime of an engram. Together, these findings are beginning to define an engram as the basic unit of memory.
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Stramska, Malgorzata, and Paulina Aniskiewicz. "Recent Large Scale Environmental Changes in the Mediterranean Sea and Their Potential Impacts on Posidonia Oceanica." Remote Sensing 11, no. 2 (January 9, 2019): 110. http://dx.doi.org/10.3390/rs11020110.
Abstract:
Climate related changes can have significant effects on Posidonia oceanica, an endemic seagrass species of the Mediterranean Sea (MEDIT). This seagrass is very important for many aspects of functioning of the sea but there is an increasing number of reports about the ongoing loss of its biomass and area coverage. We analysed multiyear data of the sea surface temperature (SST), sea level anomalies, ocean colour MODIS-A and ERA-Interim reanalysis. The results provide a description of current environmental conditions in the MEDIT and their spatial and temporal variability, including long-term trends. We defined regions where the extent of the P. oceanica meadows may be limited by specific environmental conditions. Light limitation is more severe near the northern and western coasts of the MEDIT, where the vertical diffuse attenuation coefficient is large. In the zone extending from the Gulf of Lion towards the south, significant wave heights reach large values. Wave action may destroy the plants and as a result the shallow water depth limit of P. oceanica meadows is most likely deeper here than in other regions. The highest SST values are documented in the south-eastern part of the Mediterranean Sea. In this area P. oceanica meadows are more endangered by the climate warming than in other regions where SSTs are lower. The absence of P. oceanica meadows in the south-eastern edge of the Mediterranean Sea can be attributed to high temperatures. Our conclusions are partly confirmed by the information about P. oceanica from the literature but more monitoring efforts are needed to fully describe current extent of the meadows and their shifts. Results presented in this paper can help with designing special programs to confirm the role of environmental conditions on the spatial distribution of P. oceanica and their future trends in the Mediterranean Sea.
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Raphael, M. N., G. J. Marshall, J. Turner, R. L. Fogt, D. Schneider, D. A. Dixon, J. S. Hosking, J. M. Jones, and W. R. Hobbs. "The Amundsen Sea Low: Variability, Change, and Impact on Antarctic Climate." Bulletin of the American Meteorological Society 97, no. 1 (January 1, 2016): 111–21. http://dx.doi.org/10.1175/bams-d-14-00018.1.
Abstract:
Abstract The Amundsen Sea low (ASL) is a climatological low pressure center that exerts considerable influence on the climate of West Antarctica. Its potential to explain important recent changes in Antarctic climate, for example, in temperature and sea ice extent, means that it has become the focus of an increasing number of studies. Here, the authors summarize the current understanding of the ASL, using reanalysis datasets to analyze recent variability and trends, as well as ice-core chemistry and climate model projections, to examine past and future changes in the ASL, respectively. The ASL has deepened in recent decades, affecting the climate through its influence on the regional meridional wind field, which controls the advection of moisture and heat into the continent. Deepening of the ASL in spring is consistent with observed West Antarctic warming and greater sea ice extent in the Ross Sea. Climate model simulations for recent decades indicate that this deepening is mediated by tropical variability while climate model projections through the twenty-first century suggest that the ASL will deepen in some seasons in response to greenhouse gas concentration increases.
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Guillod, Benoit P., Richard G. Jones, Simon J. Dadson, Gemma Coxon, Gianbattista Bussi, James Freer, Alison L. Kay, et al. "A large set of potential past, present and future hydro-meteorological time series for the UK." Hydrology and Earth System Sciences 22, no. 1 (January 25, 2018): 611–34. http://dx.doi.org/10.5194/hess-22-611-2018.
Abstract:
Abstract. Hydro-meteorological extremes such as drought and heavy precipitation can have large impacts on society and the economy. With potentially increasing risks associated with such events due to climate change, properly assessing the associated impacts and uncertainties is critical for adequate adaptation. However, the application of risk-based approaches often requires large sets of extreme events, which are not commonly available. Here, we present such a large set of hydro-meteorological time series for recent past and future conditions for the United Kingdom based on weather@home 2, a modelling framework consisting of a global climate model (GCM) driven by observed or projected sea surface temperature (SST) and sea ice which is downscaled to 25 km over the European domain by a regional climate model (RCM). Sets of 100 time series are generated for each of (i) a historical baseline (1900–2006), (ii) five near-future scenarios (2020–2049) and (iii) five far-future scenarios (2070–2099). The five scenarios in each future time slice all follow the Representative Concentration Pathway 8.5 (RCP8.5) and sample the range of sea surface temperature and sea ice changes from CMIP5 (Coupled Model Intercomparison Project Phase 5) models. Validation of the historical baseline highlights good performance for temperature and potential evaporation, but substantial seasonal biases in mean precipitation, which are corrected using a linear approach. For extremes in low precipitation over a long accumulation period (>3 months) and shorter-duration high precipitation (1–30 days), the time series generally represents past statistics well. Future projections show small precipitation increases in winter but large decreases in summer on average, leading to an overall drying, consistently with the most recent UK Climate Projections (UKCP09) but larger in magnitude than the latter. Both drought and high-precipitation events are projected to increase in frequency and intensity in most regions, highlighting the need for appropriate adaptation measures. Overall, the presented dataset is a useful tool for assessing the risk associated with drought and more generally with hydro-meteorological extremes in the UK.
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Rovere, Alessio, Elisa Casella, Daniel L. Harris, Thomas Lorscheid, Napayalage A. K. Nandasena, Blake Dyer, Michael R. Sandstrom, Paolo Stocchi, William J. D’Andrea, and Maureen E. Raymo. "Giant boulders and Last Interglacial storm intensity in the North Atlantic." Proceedings of the National Academy of Sciences 114, no. 46 (October 30, 2017): 12144–49. http://dx.doi.org/10.1073/pnas.1712433114.
Abstract:
As global climate warms and sea level rises, coastal areas will be subject to more frequent extreme flooding and hurricanes. Geologic evidence for extreme coastal storms during past warm periods has the potential to provide fundamental insights into their future intensity. Recent studies argue that during the Last Interglacial (MIS 5e, ∼128–116 ka) tropical and extratropical North Atlantic cyclones may have been more intense than at present, and may have produced waves larger than those observed historically. Such strong swells are inferred to have created a number of geologic features that can be observed today along the coastlines of Bermuda and the Bahamas. In this paper, we investigate the most iconic among these features: massive boulders atop a cliff in North Eleuthera, Bahamas. We combine geologic field surveys, wave models, and boulder transport equations to test the hypothesis that such boulders must have been emplaced by storms of greater-than-historical intensity. By contrast, our results suggest that with the higher relative sea level (RSL) estimated for the Bahamas during MIS 5e, boulders of this size could have been transported by waves generated by storms of historical intensity. Thus, while the megaboulders of Eleuthera cannot be used as geologic proof for past “superstorms,” they do show that with rising sea levels, cliffs and coastal barriers will be subject to significantly greater erosional energy, even without changes in storm intensity.
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Nguyen, Mai Thi, and Phu Le Vo. "IMPACT OF CLIMATE CHANGE ON THE TREND OF CHANGES IN TEMPERATURE, RAINFALL AND WATER LEVEL OF THE SAI GON RIVER IN HO CHI MINH CITY." Science and Technology Development Journal 14, no. 2 (June 30, 2011): 83–96. http://dx.doi.org/10.32508/stdj.v14i2.1920.
Abstract:
In a recent World Bank report showed that Viet Nam was one of the five (5) countries that are most affected by sea level rise, a consequence of climate change. Ho Chi Minh City (HCMC), a Vietnam’s biggest city, is accordingly identified as a most area significantly impacted by climate change in the Mekong Delta region. For those countries affected by climate change, future studies on extent and degree of impacts as well as setting out the national strategy and measures adapting to climate change is urgently and a vital of concern. This paper will present surveyed and analyzed results of possible impacts of climate change in Ho Chi Minh City, including: changes of mean temperature over the past 30 years (1979-2008); changes of rainfall (and density) and water level at the Sai Gon River in the period of 1978-2008. In addition, some specific measures for climate change adaptation are also addressed and proposed in the context of Ho Chi Minh City.
27
Townhill, Bryony L., Jonathan Tinker, Miranda Jones, Sophie Pitois, Veronique Creach, Stephen D. Simpson, Stephen Dye, Elizabeth Bear, and John K. Pinnegar. "Harmful algal blooms and climate change: exploring future distribution changes." ICES Journal of Marine Science 75, no. 6 (September 11, 2018): 1882–93. http://dx.doi.org/10.1093/icesjms/fsy113.
Abstract:
Abstract Harmful algae can cause death in fish, shellfish, marine mammals, and humans, via their toxins or from effects associated with their sheer quantity. There are many species, which cause a variety of problems around north-west Europe, and the frequency and distribution of algal blooms have altered in the recent past. Species distribution modelling was used to understand how harmful algal species may respond in the future to climate change, by considering environmental preferences and how these may shift. Most distribution studies to date use low resolution global model outputs. In this study, high resolution, downscaled shelf seas climate projections for the north-west European shelf were nested within lower resolution global projections, to understand how the distribution of harmful algae may change by the mid to end of century. Projections suggest that the habitat of most species (defined by temperature, salinity, depth, and stratification) will shift north this century, with suitability increasing in the central and northern North Sea. An increase in occurrence here might lead to more frequent detrimental blooms if wind, irradiance and nutrient levels are also suitable. Prioritizing monitoring of species in these susceptible areas could help in establishing early-warning systems for aquaculture and health protection schemes.
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Fraga, Helder, Nathalie Guimarães, and João A. Santos. "Future Changes in Rice Bioclimatic Growing Conditions in Portugal." Agronomy 9, no. 11 (October 24, 2019): 674. http://dx.doi.org/10.3390/agronomy9110674.
Abstract:
Rice is a historically important crop in Portugal. This crop development and production strongly depend on atmospheric conditions in the growing season. Given the strong dependence of climatic conditions, climate change may pose a significant risk for future rice production. In the present study, a high spatial resolution bioclimatic characterization over the main rice producing region in Portugal was performed for the recent past (1950–2000) and for the future (2041–2060) under four different anthropogenic forcing scenarios (RCP2.6, RCP4.5, RCP6.0, and RCP8.5). This zoning is performed by using eight bioclimatic indices, based on temperature and precipitation, using a very high resolution gridded dataset (Worldclim). For the future period, an 11-member global climate model ensemble was used, also taking into account model/scenario uncertainties and bias. Additionally, a new index was developed to incorporate the main features of temperature and precipitation at each rice field level. Under recent past climates, a clear north–south gradient in temperature and precipitation is apparent, with the regions of Tejo and Sado presenting higher temperatures and lower precipitation than the Mondego and Vouga regions. Additionally, there is a coastal–inland effect due to the Atlantic Ocean influence. Under anthropogenic climate change, all indices point to annual higher temperatures and lower precipitations across all rice producing regions, accompanied by increased seasonality. Furthermore, the rise of summertime temperatures may substantially increase water demands, which, when unmitigated, may bring physiological problems in the crop development. We conclude that climate change may negatively impact the viability of rice production in Portugal, particularly taking into account the national grown varieties. Thus, adequate and timely planning of suitable adaptation measures are needed to ensure the sustainability of this historically important food sector.
29
Meier, H. E. Markus, Madline Kniebusch, Christian Dieterich, Matthias Gröger, Eduardo Zorita, Ragnar Elmgren, Kai Myrberg, et al. "Climate change in the Baltic Sea region: a summary." Earth System Dynamics 13, no. 1 (March 15, 2022): 457–593. http://dx.doi.org/10.5194/esd-13-457-2022.
Abstract:
Abstract. Based on the Baltic Earth Assessment Reports of this thematic issue in Earth System Dynamics and recent peer-reviewed literature, current knowledge of the effects of global warming on past and future changes in climate of the Baltic Sea region is summarised and assessed. The study is an update of the Second Assessment of Climate Change (BACC II) published in 2015 and focuses on the atmosphere, land, cryosphere, ocean, sediments, and the terrestrial and marine biosphere. Based on the summaries of the recent knowledge gained in palaeo-, historical, and future regional climate research, we find that the main conclusions from earlier assessments still remain valid. However, new long-term, homogenous observational records, for example, for Scandinavian glacier inventories, sea-level-driven saltwater inflows, so-called Major Baltic Inflows, and phytoplankton species distribution, and new scenario simulations with improved models, for example, for glaciers, lake ice, and marine food web, have become available. In many cases, uncertainties can now be better estimated than before because more models were included in the ensembles, especially for the Baltic Sea. With the help of coupled models, feedbacks between several components of the Earth system have been studied, and multiple driver studies were performed, e.g. projections of the food web that include fisheries, eutrophication, and climate change. New datasets and projections have led to a revised understanding of changes in some variables such as salinity. Furthermore, it has become evident that natural variability, in particular for the ocean on multidecadal timescales, is greater than previously estimated, challenging our ability to detect observed and projected changes in climate. In this context, the first palaeoclimate simulations regionalised for the Baltic Sea region are instructive. Hence, estimated uncertainties for the projections of many variables increased. In addition to the well-known influence of the North Atlantic Oscillation, it was found that also other low-frequency modes of internal variability, such as the Atlantic Multidecadal Variability, have profound effects on the climate of the Baltic Sea region. Challenges were also identified, such as the systematic discrepancy between future cloudiness trends in global and regional models and the difficulty of confidently attributing large observed changes in marine ecosystems to climate change. Finally, we compare our results with other coastal sea assessments, such as the North Sea Region Climate Change Assessment (NOSCCA), and find that the effects of climate change on the Baltic Sea differ from those on the North Sea, since Baltic Sea oceanography and ecosystems are very different from other coastal seas such as the North Sea. While the North Sea dynamics are dominated by tides, the Baltic Sea is characterised by brackish water, a perennial vertical stratification in the southern subbasins, and a seasonal sea ice cover in the northern subbasins.
30
Blanden, Jo, and Stephen Machin. "Up and Down the Generational Income Ladder in Britain: Past Changes and Future Prospects." National Institute Economic Review 205 (July 2008): 101–16. http://dx.doi.org/10.1177/0027950108096594.
Abstract:
This article seeks evidence on trends in intergenerational income for cohorts born after 1970. As many of these cohorts have not yet joined the labour market, we must look at relationships between intermediate outcomes (degree attainment, test scores and non-cognitive abilities) and parental income to forecast forward from these to estimates of intergenerational earnings correlations. We find no evidence that the relationship between these intermediate outcomes and parental income have changed for more recent cohorts. Evidence from the earlier 1958 and 1970 cohorts shows that as mobility declined in the past the relationship between intermediate outcomes and parental income strengthened. We therefore conclude that, under realistic assumptions and in the absence of any significant unanticipated changes, the decline in intergenerational mobility that occurred between 1958 and 1970 birth cohorts is unlikely to continue for cohorts born from 1970 to 2000. Mobility is therefore likely to remain at or near the relatively low level observed for the 1970 birth cohort.
31
Mardones, Piero, and René D. Garreaud. "Future Changes in the Free Tropospheric Freezing Level and Rain–Snow Limit: The Case of Central Chile." Atmosphere 11, no. 11 (November 23, 2020): 1259. http://dx.doi.org/10.3390/atmos11111259.
Abstract:
The freezing level in the free troposphere often intercepts the terrain of the world’s major mountain ranges, creating a rain–snow limit. In this work, we use the free tropospheric height of the 0 °C isotherm (H0) as a proxy of both levels and study its distribution along the western slope of the subtropical Andes (30°–38° S) in present climate and during the rest of the 21st century. This portion of the Andes corresponds to central Chile, a highly populated region where warm winter storms have produced devastating landslides and widespread flooding in the recent past. Our analysis is based on the frequency distribution of H0 derived from radiosonde and surface observations, atmospheric reanalysis and climate simulations. The future projections primarily employ a scenario of heavy greenhouse gasses emissions (RCP8.5), but we also examine the more benign RCP4.5 scenario. The current H0 distribution along the central Chile coast shows a gradual decrease southward, with mean heights close to 2600 m ASL (above sea level) at 30 °C S to 2000 m ASL at 38° S for days with precipitation, about 800 m lower than during dry days. The mean value under wet conditions toward the end of the century (under RCP8.5) is close to, or higher than, the upper quartile of the H0 distribution in the current climate. More worrisome, H0 values that currently occur only 5% of the time will be exceeded in about a quarter of the rainy days by the end of the century. Under RCP8.5, even moderate daily precipitation can increase river flow to levels that are considered hazardous for central Chile.
32
Thomas, Elizabeth R., Claire S. Allen, Johan Etourneau, Amy C. F. King, Mirko Severi, V. Holly L. Winton, Juliane Mueller, Xavier Crosta, and Victoria L. Peck. "Antarctic Sea Ice Proxies from Marine and Ice Core Archives Suitable for Reconstructing Sea Ice over the Past 2000 Years." Geosciences 9, no. 12 (December 4, 2019): 506. http://dx.doi.org/10.3390/geosciences9120506.
Abstract:
Dramatic changes in sea ice have been observed in both poles in recent decades. However, the observational period for sea ice is short, and the climate models tasked with predicting future change in sea ice struggle to capture the current Antarctic trends. Paleoclimate archives, from marine sedimentary records and coastal Antarctic ice cores, provide a means of understanding sea ice variability and its drivers over decadal to centennial timescales. In this study, we collate published records of Antarctic sea ice over the past 2000 years (2 ka). We evaluate the current proxies and explore the potential of combining marine and ice core records to produce multi-archive reconstructions. Despite identifying 92 sea ice reconstructions, the spatial and temporal resolution is only sufficient to reconstruct circum-Antarctic sea ice during the 20th century, not the full 2 ka. Our synthesis reveals a 90 year trend of increasing sea ice in the Ross Sea and declining sea ice in the Bellingshausen, comparable with observed trends since 1979. Reconstructions in the Weddell Sea, the Western Pacific and the Indian Ocean reveal small negative trends in sea ice during the 20th century (1900–1990), in contrast to the observed sea ice expansion in these regions since 1979.
33
Quiquet, Aurélien, and Christophe Dumas. "The GRISLI-LSCE contribution to the Ice Sheet Model Intercomparison Project for phase 6 of the Coupled Model Intercomparison Project (ISMIP6) – Part 2: Projections of the Antarctic ice sheet evolution by the end of the 21st century." Cryosphere 15, no. 2 (February 26, 2021): 1031–52. http://dx.doi.org/10.5194/tc-15-1031-2021.
Abstract:
Abstract. The Antarctic ice sheet's contribution to global sea level rise over the 21st century is of primary societal importance and remains largely uncertain as of yet. In particular, in the recent literature, the contribution of the Antarctic ice sheet by 2100 can be negative (sea level fall) by a few centimetres or positive (sea level rise), with some estimates above 1 m. The Ice Sheet Model Intercomparison Project for the Coupled Model Intercomparison Project – phase 6 (ISMIP6) aimed at reducing the uncertainties in the fate of the ice sheets in the future by gathering various ice sheet models in a common framework. Here, we present the GRISLI-LSCE (Grenoble Ice Sheet and Land Ice model of the Laboratoire des Sciences du Climat et de l'Environnement) contribution to ISMIP6-Antarctica. We show that our model is strongly sensitive to the climate forcing used, with a contribution of the Antarctic ice sheet to global sea level rise by 2100 that ranges from −50 to +150 mm sea level equivalent (SLE). Future oceanic warming leads to a decrease in thickness of the ice shelves, resulting in grounding-line retreat, while increased surface mass balance partially mitigates or even overcompensates the dynamic ice sheet contribution to global sea level rise. Most of the ice sheet changes over the next century are dampened under low-greenhouse-gas-emission scenarios. Uncertainties related to sub-ice-shelf melt rates induce large differences in simulated grounding-line retreat, confirming the importance of this process and its representation in ice sheet models for projections of the Antarctic ice sheet's evolution.
34
Wall-Palmer, D., M. B. Hart, C. W. Smart, R. S. J. Sparks, A. Le Friant, G. Boudon, C. Deplus, and J. C. Komorowski. "Pteropods from the Caribbean Sea: variations in calcification as an indicator of past ocean carbonate saturation." Biogeosciences 9, no. 1 (January 16, 2012): 309–15. http://dx.doi.org/10.5194/bg-9-309-2012.
Abstract:
Abstract. The aragonite shell-bearing thecosome pteropods are an important component of the oceanic plankton. However, with increasing pCO2 and the associated reduction in oceanic pH (ocean acidification), thecosome pteropods are thought to be particularly vulnerable to shell dissolution. The distribution and preservation of pteropods over the last 250 000 years have been investigated in marine sediment cores from the Caribbean Sea close to the island of Montserrat. Using the Limacina Dissolution Index (LDX), fluctuations in pteropod calcification through the most recent glacial/interglacial cycles are documented. By comparison to the oxygen isotope record (global ice volume), we show that pteropod calcification is closely linked to global changes in pCO2 and pH and is, therefore, a global signal. These data are in agreement with the findings of experiments upon living pteropods, which show that variations in pH can greatly affect aragonitic shells. The results of this study provide information which may be useful in the prediction of future changes to the pteropod assemblage caused by ocean acidification.
35
Mölg, Thomas, and Carolyne Pickler. "A mid-troposphere perspective on the East African climate paradox." Environmental Research Letters 17, no. 8 (August 1, 2022): 084041. http://dx.doi.org/10.1088/1748-9326/ac8565.
Abstract:
Abstract The East African climate paradox—a term framing the observed precipitation decline in the March–May (MAM) wet season of East Africa from roughly 1980–2010, yet an increase in future climates simulated by global climate models (GCMs)—mostly relies on data representing sea level. Here we add a mid-troposphere perspective by combining in-situ meteorological measurements at ∼6000 m a.s.l. from Africa’s highest mountain summit and a carefully selected subset of GCMs through a machine-learning link. Temporal trends of the resultant six weather types do support a drier mountain climate in the recent past and a moister one in the course of the 21st century, and a key to understanding these contrasting trends materializes from the new dominance of changes in weather type frequency in the future climate. Importantly, however, the results also suggest that the trend reversal requires a strong external climate forcing. Hence, the forcing strength should be considered more systematically in forthcoming studies, to challenge the question whether equatorial East Africa’s MAM climate will indeed become wetter in all plausible future scenarios.
36
Berends, Constantijn J., Bas de Boer, and Roderik S. W. van de Wal. "Reconstructing the evolution of ice sheets, sea level, and atmospheric CO<sub>2</sub> during the past 3.6 million years." Climate of the Past 17, no. 1 (February 1, 2021): 361–77. http://dx.doi.org/10.5194/cp-17-361-2021.
Abstract:
Abstract. Understanding the evolution of, and the interactions between, ice sheets and the global climate over geological timescales is important for being able to project their future evolution. However, direct observational evidence of past CO2 concentrations, and the implied radiative forcing, only exists for the past 800 000 years. Records of benthic δ18O date back millions of years but contain signals from both land ice volume and ocean temperature. In recent years, inverse forward modelling has been developed as a method to disentangle these two signals, resulting in mutually consistent reconstructions of ice volume, temperature, and CO2. We use this approach to force a hybrid ice-sheet–climate model with a benthic δ18O stack, reconstructing the evolution of the ice sheets, global mean sea level, and atmospheric CO2 during the late Pliocene and the Pleistocene, from 3.6 million years (Myr) ago to the present day. During the warmer-than-present climates of the late Pliocene, reconstructed CO2 varies widely, from 320–440 ppmv for warm periods to 235–250 ppmv for the early glacial excursion ∼3.3 million years ago. Sea level is relatively stable during this period, with maxima of 6–14 m and minima of 12–26 m during glacial episodes. Both CO2 and sea level are within the wide ranges of values covered by available proxy data for this period. Our results for the Pleistocene agree well with the ice-core CO2 record, as well as with different available sea-level proxy data. For the Early Pleistocene, 2.6–1.2 Myr ago, we simulate 40 kyr glacial cycles, with interglacial CO2 decreasing from 280–300 ppmv at the beginning of the Pleistocene to 250–280 ppmv just before the Mid-Pleistocene Transition (MPT). Peak glacial CO2 decreases from 220–250 to 205–225 ppmv during this period. After the MPT, when the glacial cycles change from 40 to 80 120 kyr cyclicity, the glacial–interglacial contrast increases, with interglacial CO2 varying between 250–320 ppmv and peak glacial values decreasing to 170–210 ppmv.
37
Williams, Ross H., David McGee, Christopher W. Kinsley, David A. Ridley, Shineng Hu, Alexey Fedorov, Irit Tal, Richard W. Murray, and Peter B. deMenocal. "Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks." Science Advances 2, no. 11 (November 2016): e1600445. http://dx.doi.org/10.1126/sciadv.1600445.
Abstract:
Saharan mineral dust exported over the tropical North Atlantic is thought to have significant impacts on regional climate and ecosystems, but limited data exist documenting past changes in long-range dust transport. This data gap limits investigations of the role of Saharan dust in past climate change, in particular during the mid-Holocene, when climate models consistently underestimate the intensification of the West African monsoon documented by paleorecords. We present reconstructions of African dust deposition in sediments from the Bahamas and the tropical North Atlantic spanning the last 23,000 years. Both sites show early and mid-Holocene dust fluxes 40 to 50% lower than recent values and maximum dust fluxes during the deglaciation, demonstrating agreement with records from the northwest African margin. These quantitative estimates of trans-Atlantic dust transport offer important constraints on past changes in dust-related radiative and biogeochemical impacts. Using idealized climate model experiments to investigate the response to reductions in Saharan dust’s radiative forcing over the tropical North Atlantic, we find that small (0.15°C) dust-related increases in regional sea surface temperatures are sufficient to cause significant northward shifts in the Atlantic Intertropical Convergence Zone, increased precipitation in the western Sahel and Sahara, and reductions in easterly and northeasterly winds over dust source regions. Our results suggest that the amplifying feedback of dust on sea surface temperatures and regional climate may be significant and that accurate simulation of dust’s radiative effects is likely essential to improving model representations of past and future precipitation variations in North Africa.
38
Yang, Hu, Uta Krebs-Kanzow, Thomas Kleiner, Dmitry Sidorenko, Christian Bernd Rodehacke, Xiaoxu Shi, Paul Gierz, et al. "Impact of paleoclimate on present and future evolution of the Greenland Ice Sheet." PLOS ONE 17, no. 1 (January 20, 2022): e0259816. http://dx.doi.org/10.1371/journal.pone.0259816.
Abstract:
Using transient climate forcing based on simulations from the Alfred Wegener Institute Earth System Model (AWI-ESM), we simulate the evolution of the Greenland Ice Sheet (GrIS) from the last interglacial (125 ka, kiloyear before present) to 2100 AD with the Parallel Ice Sheet Model (PISM). The impact of paleoclimate, especially Holocene climate, on the present and future evolution of the GrIS is explored. Our simulations of the past show close agreement with reconstructions with respect to the recent timing of the peaks in ice volume and the climate of Greenland. The maximum and minimum ice volume at around 18–17 ka and 6–5 ka lag the respective extremes in climate by several thousand years, implying that the ice volume response of the GrIS strongly lags climatic changes. Given that Greenland’s climate was getting colder from the Holocene Thermal Maximum (i.e., 8 ka) to the Pre-Industrial era, our simulation implies that the GrIS experienced growth from the mid-Holocene to the industrial era. Due to this background trend, the GrIS still gains mass until the second half of the 20th century, even though anthropogenic warming begins around 1850 AD. This is also in agreement with observational evidence showing mass loss of the GrIS does not begin earlier than the late 20th century. Our results highlight that the present evolution of the GrIS is not only controlled by the recent climate changes, but is also affected by paleoclimate, especially the relatively warm Holocene climate. We propose that the GrIS was not in equilibrium throughout the entire Holocene and that the slow response to Holocene climate needs to be represented in ice sheet simulations in order to predict ice mass loss, and therefore sea level rise, accurately.
39
Pitskhelauri, Konstantine (Kiazo), and Mikheil Elashvili. "Traces of Early State formations in South East Georgia, Caucasus - response and impact on changes in the climate and environment Shiraqi Plane, South East Georgia, Caucasus." South Caucasus – Archaeological Context, no. 1 (November 25, 2021): 60–68. http://dx.doi.org/10.52147/2667-9353/2021-1-60-68.
Abstract:
Study of past changes in environment and, its effect on human society delivers key information to reconstruct the hystorical past but also to project future changes and their effects. Study focus on South-East Georgia, Caucasus region, which represents natural polygon of long term changes in the environment. Study area represents semi-arid Shiraqi plain in South-East Georgia (see the map below). It is characterized with annual precipitation <600mm and shows open dry steppic landscape today. However, recent data collected using remote sensing and archaeological studies, deliver evidences of early human inhabitation of this area, starting from the Paleolithic and forming a constant chain of active settlement through the time, until sudden abrupt at the end of the Bronze Age. Geomorphologically Shiraqi plane represents 800 sqr. km of almost flat area with average height of 600 m above Sea level, surrounded by chains of mountains creating a natural walls surrounding the plane. There are almost no settlements in the area, devoid of water resources today. Archaeo-Botanic and soil studies assume that the region was covered by forests, Hydro modelling shows possibility of existence of well developed water network with a shallow lake in the center of plane. Remote sensing data and resent archaeological excavations at Didnauri site provides clear evidences of early state formation, with favorable paleo-environmental conditions. The goal of current study is to shed light on historic changes in the environment of the region, its natural and anthropogenic factors and consequently response of human society on these changes.
40
Regan, Heather, Camille Lique, Claude Talandier, and Gianluca Meneghello. "Response of Total and Eddy Kinetic Energy to the Recent Spinup of the Beaufort Gyre." Journal of Physical Oceanography 50, no. 3 (March 2020): 575–94. http://dx.doi.org/10.1175/jpo-d-19-0234.1.
Abstract:
AbstractThe Beaufort Gyre in the Arctic Ocean has spun up over the past two decades in response to changes of the wind forcing and sea ice conditions, accumulating a significant amount of freshwater. Here a simulation performed with a high-resolution, eddy-resolving model is analyzed in order to provide a detailed description of the total and eddy kinetic energy and their response to this spinup of the gyre. On average, and in contrast to the typical open ocean conditions, the levels of mean and eddy kinetic energy are of the same order of magnitude, and the eddy kinetic energy is only intensified along the boundary and in the subsurface. In response to the strong anomalous atmospheric conditions in 2007, the gyre spins up and the mean kinetic energy almost doubles, while the eddy kinetic energy does not increase significantly for a long time period. This is because the isopycnals are able to flatten and the gyre expands outwards, reducing the potential for baroclinic instability. These results have implications for understanding the mechanisms at play for equilibrating the Beaufort Gyre and the variability and future changes of the Arctic freshwater system.
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Yeo, In-Sung Luke. "Modifications of Dental Implant Surfaces at the Micro- and Nano-Level for Enhanced Osseointegration." Materials 13, no. 1 (December 23, 2019): 89. http://dx.doi.org/10.3390/ma13010089.
Abstract:
This review paper describes several recent modification methods for biocompatible titanium dental implant surfaces. The micro-roughened surfaces reviewed in the literature are sandblasted, large-grit, acid-etched, and anodically oxidized. These globally-used surfaces have been clinically investigated, showing survival rates higher than 95%. In the past, dental clinicians believed that eukaryotic cells for osteogenesis did not recognize the changes of the nanostructures of dental implant surfaces. However, research findings have recently shown that osteogenic cells respond to chemical and morphological changes at a nanoscale on the surfaces, including titanium dioxide nanotube arrangements, functional peptide coatings, fluoride treatments, calcium–phosphorus applications, and ultraviolet photofunctionalization. Some of the nano-level modifications have not yet been clinically evaluated. However, these modified dental implant surfaces at the nanoscale have shown excellent in vitro and in vivo results, and thus promising potential future clinical use.
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De Rydt, Jan, Ronja Reese, Fernando S. Paolo, and G. Hilmar Gudmundsson. "Drivers of Pine Island Glacier speed-up between 1996 and 2016." Cryosphere 15, no. 1 (January 7, 2021): 113–32. http://dx.doi.org/10.5194/tc-15-113-2021.
Abstract:
Abstract. Pine Island Glacier in West Antarctica is among the fastest changing glaciers worldwide. Over the last 2 decades, the glacier has lost in excess of a trillion tons of ice, or the equivalent of 3 mm of sea level rise. The ongoing changes are thought to have been triggered by ocean-induced thinning of its floating ice shelf, grounding line retreat, and the associated reduction in buttressing forces. However, other drivers of change, such as large-scale calving and changes in ice rheology and basal slipperiness, could play a vital, yet unquantified, role in controlling the ongoing and future evolution of the glacier. In addition, recent studies have shown that mechanical properties of the bed are key to explaining the observed speed-up. Here we used a combination of the latest remote sensing datasets between 1996 and 2016, data assimilation tools, and numerical perturbation experiments to quantify the relative importance of all processes in driving the recent changes in Pine Island Glacier dynamics. We show that (1) calving and ice shelf thinning have caused a comparable reduction in ice shelf buttressing over the past 2 decades; that (2) simulated changes in ice flow over a viscously deforming bed are only compatible with observations if large and widespread changes in ice viscosity and/or basal slipperiness are taken into account; and that (3) a spatially varying, predominantly plastic bed rheology can closely reproduce observed changes in flow without marked variations in ice-internal and basal properties. Our results demonstrate that, in addition to its evolving ice thickness, calving processes and a heterogeneous bed rheology play a key role in the contemporary evolution of Pine Island Glacier.
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Zhao, Chen, Rupert M. Gladstone, Roland C. Warner, Matt A. King, Thomas Zwinger, and Mathieu Morlighem. "Basal friction of Fleming Glacier, Antarctica – Part 2: Evolution from 2008 to 2015." Cryosphere 12, no. 8 (August 15, 2018): 2653–66. http://dx.doi.org/10.5194/tc-12-2653-2018.
Abstract:
Abstract. The Wordie Ice Shelf–Fleming Glacier system in the southern Antarctic Peninsula has experienced a long-term retreat and disintegration of its ice shelf in the past 50 years. Increases in the glacier velocity and dynamic thinning have been observed over the past two decades, especially after 2008 when only a small ice shelf remained at the Fleming Glacier front. It is important to know whether the substantial further speed-up and greater surface draw-down of the glacier since 2008 is a direct response to ocean forcing, or driven by feedbacks within the grounded marine-based glacier system, or both. Recent observational studies have suggested the 2008–2015 velocity change was due to the ungrounding of the Fleming Glacier front. To explore the mechanisms underlying the recent changes, we use a full-Stokes ice sheet model to simulate the basal shear stress distribution of the Fleming system in 2008 and 2015. This study is part of the first high resolution modelling campaign of this system. Comparison of inversions for basal shear stresses for 2008 and 2015 suggests the migration of the grounding line ∼9 km upstream by 2015 from the 2008 ice front/grounding line positions, which virtually coincided with the 1996 grounding line position. This migration is consistent with the change in floating area deduced from the calculated height above buoyancy in 2015. The retrograde submarine bed underneath the lowest part of the Fleming Glacier may have promoted retreat of the grounding line. Grounding line retreat may also be enhanced by a feedback mechanism upstream of the grounding line by which increased basal lubrication due to increasing frictional heating enhances sliding and thinning. Improved knowledge of bed topography near the grounding line and further transient simulations with oceanic forcing are required to accurately predict the future movement of the Fleming Glacier system grounding line and better understand its ice dynamics and future contribution to sea level.
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Jorgenson, M., Gerald Frost, and Dorte Dissing. "Drivers of Landscape Changes in Coastal Ecosystems on the Yukon-Kuskokwim Delta, Alaska." Remote Sensing 10, no. 8 (August 14, 2018): 1280. http://dx.doi.org/10.3390/rs10081280.
Abstract:
The Yukon-Kuskokwim Delta (YKD) is the largest delta in western North America and its productive coastal ecosystems support globally significant populations of breeding birds and a large indigenous population. To quantify past landscape changes as a guide to assessing future climate impacts to the YKD and how indigenous society may adapt to change, we photo-interpreted ecotypes at 600 points within 12 grids in a 2118 km2 area along the central YKD coast using a time-series of air photos from 1948–1955 and 1980 and satellite images from 2007–2008 (IKONOS) and 2013–2016 (WorldView). We found that ecotype classes changed 16.2% (342 km2) overall during the ~62 years. Ecotypes changed 6.0% during 1953–1980, 7.2% during 1980–2007 and 3.8% during 2007–2015. Lowland Moist Birch-Ericaceous Low Scrub (−5.0%) and Coastal Saline Flat Barrens (−2.3%) showed the greatest decreases in area, while Lowland Water Sedge Meadow (+1.7%) and Lacustrine Marestail Marsh (+1.3%) showed the largest increases. Dominant processes affecting change were permafrost degradation (5.3%), channel erosion (3.0%), channel deposition (2.2%), vegetation colonization (2.3%) and lake drainage (1.5%), while sedimentation, water-level fluctuations, permafrost aggradation and shoreline paludification each affected <0.5% of the area. Rates of change increased dramatically in the late interval for permafrost degradation (from 0.06 to 0.26%/year) and vegetation colonization (from 0.03 to 0.16%/year), while there was a small decrease in channel deposition (from 0.05 to 0.0%/year) due largely to barren mudflats being colonized by vegetation. In contrast, rates of channel erosion remained fairly constant. The increased permafrost degradation coincided with increasing storm frequency and air temperatures. We attribute increased permafrost degradation and vegetation colonization during the recent interval mostly to the effects of a large storm in 2005, which caused extensive salt-kill of vegetation along the margins of permafrost plateaus and burial of vegetation on active tidal flats by mud that was later recolonized. Due to the combination of extremely flat terrain, sea-level rise, sea-ice reduction that facilitates more storm flooding and accelerating permafrost degradation, we believe the YKD is the most vulnerable region in the Arctic to climate warming.
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Steneck, Robert S., Michael H. Graham, Bruce J. Bourque, Debbie Corbett, Jon M. Erlandson, James A. Estes, and Mia J. Tegner. "Kelp forest ecosystems: biodiversity, stability, resilience and future." Environmental Conservation 29, no. 4 (December 2002): 436–59. http://dx.doi.org/10.1017/s0376892902000322.
Abstract:
Kelp forests are phyletically diverse, structurally complex and highly productive components of coldwater rocky marine coastlines. This paper reviews the conditions in which kelp forests develop globally and where, why and at what rate they become deforested. The ecology and long archaeological history of kelp forests are examined through case studies from southern California, the Aleutian Islands and the western North Atlantic, well-studied locations that represent the widest possible range in kelp forest biodiversity. Global distribution of kelp forests is physiologically constrained by light at high latitudes and by nutrients, warm temperatures and other macrophytes at low latitudes. Within mid-latitude belts (roughly 40–60° latitude in both hemispheres) well-developed kelp forests are most threatened by herbivory, usually from sea urchins. Overfishing and extirpation of highly valued vertebrate apex predators often triggered herbivore population increases, leading to widespread kelp deforestation. Such deforestations have the most profound and lasting impacts on species-depauperate systems, such as those in Alaska and the western North Atlantic. Globally urchin-induced deforestation has been increasing over the past 2–3 decades. Continued fishing down of coastal food webs has resulted in shifting harvesting targets from apex predators to their invertebrate prey, including kelp-grazing herbivores. The recent global expansion of sea urchin harvesting has led to the widespread extirpation of this herbivore, and kelp forests have returned in some locations but, for the first time, these forests are devoid of vertebrate apex predators. In the western North Atlantic, large predatory crabs have recently filled this void and they have become the new apex predator in this system. Similar shifts from fish- to crab-dominance may have occurred in coastal zones of the United Kingdom and Japan, where large predatory finfish were extirpated long ago. Three North American case studies of kelp forests were examined to determine their long history with humans and project the status of future kelp forests to the year 2025. Fishing impacts on kelp forest systems have been both profound and much longer in duration than previously thought. Archaeological data suggest that coastal peoples exploited kelp forest organisms for thousands of years, occasionally resulting in localized losses of apex predators, outbreaks of sea urchin populations and probably small-scale deforestation. Over the past two centuries, commercial exploitation for export led to the extirpation of sea urchin predators, such as the sea otter in the North Pacific and predatory fishes like the cod in the North Atlantic. The large-scale removal of predators for export markets increased sea urchin abundances and promoted the decline of kelp forests over vast areas. Despite southern California having one of the longest known associations with coastal kelp forests, widespread deforestation is rare. It is possible that functional redundancies among predators and herbivores make this most diverse system most stable. Such biodiverse kelp forests may also resist invasion from non-native species. In the species-depauperate western North Atlantic, introduced algal competitors carpet the benthos and threaten future kelp dominance. There, other non-native herbivores and predators have become established and dominant components of this system. Climate changes have had measurable impacts on kelp forest ecosystems and efforts to control the emission of greenhouse gasses should be a global priority. However, overfishing appears to be the greatest manageable threat to kelp forest ecosystems over the 2025 time horizon. Management should focus on minimizing fishing impacts and restoring populations of functionally important species in these systems.
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Carter, Timothy R. "Developing scenarios of atmosphere, weather and climate for northern regions." Agricultural and Food Science 5, no. 3 (May 1, 1996): 235–49. http://dx.doi.org/10.23986/afsci.72743.
Abstract:
Future changes in atmospheric composition and consequent global and regional climate change are of increasing concern to policy makers, planners and the public. However, predictions of these changes are uncertain. In the absence of single, firm predictions, the next best approach is to identify sets of plausible future conditions termed scenarios. This paper focuses on the development of climate change scenarios for northern high latitude regions. Three methods of scenario development can be identified; use of analogues having conditions similar to those expected in the study region, application of general circulation model results, and composite methods that combine information from different sources. A composite approach has been used to produce scenarios of temperature, precipitation, carbon dioxide and sea-level change for Finland up to 2100, as part of the Finnish Research Programme on Climate Change (SILMU). Tools for applying these scenarios in impact assessment studies, including stochastic weather generators and spatial downscaling techniques, are also examined. The SILMU scenarios attempt to capture uncertainties both in future emissions of greenhouse gases and aerosols into the atmosphere and in the global climate response to these emissions. Two types of scenario were developed: (i) simple “policy-oriented” scenarios and (ii) detailed “scientific” scenarios. These are compared with new model estimates of future climate and recent observed changes in climate over certain high latitude regions.
47
Barnston, Anthony G., Bradfield Lyon, Ethan D. Coffel, and Radley M. Horton. "Daily Autocorrelation and Mean Temperature/Moisture Rise as Determining Factors for Future Heat-Wave Patterns in the United States." Journal of Applied Meteorology and Climatology 59, no. 10 (October 1, 2020): 1735–54. http://dx.doi.org/10.1175/jamc-d-19-0291.1.
Abstract:
AbstractThe frequency of heat waves (defined as daily temperature exceeding the local 90th percentile for at least three consecutive days) during summer in the United States is examined for daily maximum and minimum temperature and maximum apparent temperature, in recent observations and in 10 CMIP5 models for recent past and future. The annual average percentage of days participating in a heat wave varied between approximately 2% and 10% in observations and in the model’s historical simulations during 1979–2005. Applying today’s temperature thresholds to future projections, heat-wave frequencies rise to more than 20% by 2035–40. However, given the models’ slight overestimation of frequencies and positive trend rates during 1979–2005, these projected heat-wave frequencies should be regarded cautiously. The models’ overestimations may be associated with their higher daily autocorrelation than is found in observations. Heat-wave frequencies defined using apparent temperature, reflecting both temperature and atmospheric moisture, are projected to increase at a slightly (and statistically significantly) faster rate than for temperature alone. Analyses show little or no changes in the day-to-day variability or persistence (autocorrelation) of extreme temperature between recent past and future, indicating that the future heat-wave frequency will be due predominantly to increases in standardized (using historical period statistics) mean temperature and moisture content, adjusted by the local climatological daily autocorrelation. Using nonparametric methods, the average level and spatial pattern of future heat-wave frequency is shown to be approximately predictable on the basis of only projected mean temperature increases and local autocorrelation. These model-projected changes, even if only approximate, would impact infrastructure, ecology, and human well-being.
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Abrahamsen, E. P. "Sustaining observations in the polar oceans." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2025 (September 28, 2014): 20130337. http://dx.doi.org/10.1098/rsta.2013.0337.
Abstract:
Polar oceans present a unique set of challenges to sustained observations. Sea ice cover restricts navigation for ships and autonomous measurement platforms alike, and icebergs present a hazard to instruments deployed in the upper ocean and in shelf seas. However, the important role of the poles in the global ocean circulation provides ample justification for sustained observations in these regions, both to monitor the rapid changes taking place, and to better understand climate processes in these traditionally poorly sampled areas. In the past, the vast majority of polar measurements took place in the summer. In recent years, novel techniques such as miniature CTD (conductivity–temperature–depth) tags carried by seals have provided an explosion in year-round measurements in areas largely inaccessible to ships, and, as ice avoidance is added to autonomous profiling floats and gliders, these promise to provide further enhancements to observing systems. In addition, remote sensing provides vital information about changes taking place in sea ice cover at both poles. To make these observations sustainable into the future, improved international coordination and collaboration is necessary to gain optimum utilization of observing networks.
49
Andrews, O. D., N. L. Bindoff, P. R. Halloran, T. Ilyina, and C. Le Quéré. "Detecting an external influence on recent changes in oceanic oxygen using an optimal fingerprinting method." Biogeosciences Discussions 9, no. 9 (September 13, 2012): 12469–504. http://dx.doi.org/10.5194/bgd-9-12469-2012.
Abstract:
Abstract. Ocean deoxygenation has been observed in all major ocean basins over the past 50 yr. Although this signal is largely consistent with oxygen changes expected from anthropogenic climate change, the contribution of external forcing to recent deoxygenation trends relative to natural internal variability is yet to be established. Here we conduct a formal optimal fingerprinting analysis to investigate if external forcing has had a detectable influence on observed dissolved oxygen concentration ([O2]) changes between ~ 1970 and ~ 1992 using simulations from two Earth System Models (MPI-ESM-LR and HadGEM2-ES). We detect a response to external forcing at a 90% confidence level and find that observed [O2] changes are inconsistent with internal variability as simulated by models. This result is robust in the global ocean for depth-averaged (1-D) zonal mean patterns of [O2] change in both models. Further analysis with the MPI-ESM-LR model shows similar positive detection results for depth-resolved (2-D) zonal mean [O2] changes globally and for the Pacific Ocean individually. Observed oxygen changes in the Atlantic Ocean are indistinguishable from natural internal variability. Simulations from both models consistently underestimate the amplitude of historical [O2] changes in response to external forcing, suggesting that model projections for future ocean deoxygenation may also be underestimated.
50
Andrews, O. D., N. L. Bindoff, P. R. Halloran, T. Ilyina, and C. Le Quéré. "Detecting an external influence on recent changes in oceanic oxygen using an optimal fingerprinting method." Biogeosciences 10, no. 3 (March 19, 2013): 1799–813. http://dx.doi.org/10.5194/bg-10-1799-2013.
Abstract:
Abstract. Ocean deoxygenation has been observed in all major ocean basins over the past 50 yr. Although this signal is largely consistent with oxygen changes expected from anthropogenic climate change, the contribution of external forcing to recent deoxygenation trends relative to natural internal variability is yet to be established. Here we conduct a formal optimal fingerprinting analysis to investigate if external forcing has had a detectable influence on observed dissolved oxygen concentration ([O2]) changes between ∼1970 and ∼1992 using simulations from two Earth System Models (MPI-ESM-LR and HadGEM2-ES). We detect a response to external forcing at a 90% confidence level and find that observed [O2] changes are inconsistent with internal variability as simulated by models. This result is robust in the global ocean for depth-averaged (1-D) zonal mean patterns of [O2] change in both models. Further analysis with the MPI-ESM-LR model shows similar positive detection results for depth-resolved (2-D) zonal mean [O2] changes globally and for the Pacific Ocean individually. Observed oxygen changes in the Atlantic Ocean are indistinguishable from natural internal variability. Simulations from both models consistently underestimate the amplitude of historical [O2] changes in response to external forcing, suggesting that model projections for future ocean deoxygenation may also be underestimated.