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1
Petersen, Nikolaj. "SAC at Thule: Greenland in U.S. Polar Strategy." Journal of Cold War Studies 13, no. 2 (April 2011): 90–115. http://dx.doi.org/10.1162/jcws_a_00138.
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This article discusses the so-called polar strategy of the U.S. Strategic Air Command (SAC) from 1958, when SAC decided to build Thule Air Force Base in Greenland, until 1968, when Airborne Alert flights over Greenland were abandoned after a fully armed B-52 crashed near Thule. The article traces the implementation of the polar strategy from a “bottom-up” perspective, concentrating on deployments and rotations to Thule and training missions and operations out of Thule. The analysis, based on U.S. Air Force unit histories and Danish military reports, shows that the early polar strategy operated under difficult conditions but gradually became more feasible. In 1957 the strategy was implemented at Thule, but paradoxically it did not come to full fruition until the introduction of the B-52, which was not dependent on support from Thule. By 1960, SAC had left Thule, the emblem of the early polar strategy, but SAC bombers continued to fly missions in Greenland's airspace until 1968.
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Reeves, Will K., Mark S. Breidenbaugh, Earl E. Thomas, and Meaghan N. Glowacki. "Mosquitoes of Thule Air Base, Greenland." Journal of the American Mosquito Control Association 29, no. 4 (December 2013): 383–84. http://dx.doi.org/10.2987/13-6341.1.
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Vinson, Rob, and Ken Garret. "Enzyme-enhanced bioremediation at Thule Air Base, Greenland." Federal Facilities Environmental Journal 10, no. 4 (2000): 39–49. http://dx.doi.org/10.1002/ffej.3330100406.
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Ackrén, Maria, and Uffe Jakobsen. "Greenland as a self-governing sub-national territory in international relations: past, current and future perspectives." Polar Record 51, no. 4 (September 9, 2014): 404–12. http://dx.doi.org/10.1017/s003224741400028x.
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ABSTRACTGreenland was used by the US as a platform and as an extended arm within its security and foreign policy during the World War II and the cold war. After this things changed, although Greenland remained important in Danish-US relations under the umbrella of NATO. Nowadays, the geostrategic position of Greenland between North America and Europe is gaining fresh prominence in the race for natural resources in the Arctic. Many issues arise from the prospective opening of the Arctic, all of which may have fateful impacts on future development in the region. Climate change, claims related to the extension of the continental shelf, exploitation and exploration of natural resources, together with the protection of indigenous peoples are all current issues that must be taken into consideration in the context of security and foreign policy formation in Greenland. The future of the Thule Air Base is also relevant. This article reviews developments from the World War II to the present regarding international relations from a Greenlandic perspective. As a self-governing sub-national territory within the realm of Denmark, Greenland does not have the ultimate decision-making power within foreign and security policy. The new Self-Government Act of 2009, however, gives Greenland some room for manoeuvre in this respect.
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Won, Y. I., R. J. Niciejewski, T. L. Killeen, R. M. Johnson, and B. Y. Lee. "Observations of high-latitude lower thermospheric winds from Thule Air Base and Søndre Strømfjord, Greenland." Journal of Geophysical Research: Space Physics 104, A1 (January 1, 1999): 25–32. http://dx.doi.org/10.1029/1998ja900059.
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Akers, Pete D., Ben G. Kopec, Kyle S. Mattingly, Eric S. Klein, Douglas Causey, and Jeffrey M. Welker. "Baffin Bay sea ice extent and synoptic moisture transport drive water vapor isotope (<i>δ</i><sup>18</sup>O, <i>δ</i><sup>2</sup>H, and deuterium excess) variability in coastal northwest Greenland." Atmospheric Chemistry and Physics 20, no. 22 (November 19, 2020): 13929–55. http://dx.doi.org/10.5194/acp-20-13929-2020.
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Abstract. At Thule Air Base on the coast of Baffin Bay (76.51∘ N, 68.74∘ W), we continuously measured water vapor isotopes (δ18O, δ2H) at a high frequency (1 s−1) from August 2017 through August 2019. Our resulting record, including derived deuterium excess (dxs) values, allows an analysis of isotopic–meteorological relationships at an unprecedented level of detail and duration for high Arctic Greenland. We examine isotopic variability across multiple temporal scales from daily to interannual, revealing that isotopic values at Thule are predominantly controlled by the sea ice extent in northern Baffin Bay and the synoptic flow pattern. This relationship can be identified through its expression in the following five interacting factors: (a) local air temperature, (b) local marine moisture availability, (c) the North Atlantic Oscillation (NAO), (d) surface wind regime, and (e) land-based evaporation and sublimation. Each factor's relative importance changes based on the temporal scale and in response to seasonal shifts in Thule's environment. Winter sea ice coverage forces distant sourcing of vapor that is isotopically light from fractionation during transport, while preventing isotopic exchange with local waters. Sea ice breakup in late spring triggers a rapid isotopic change at Thule as the newly open ocean supplies warmth and moisture that has ∼10 ‰ and ∼70 ‰ higher δ18O and δ2H values, respectively, and ∼10 ‰ lower dxs values. Sea ice retreat also leads to other environmental changes, such as sea breeze development, that radically alter the nature of relationships between isotopes and many meteorological variables in summer. On synoptic timescales, enhanced southerly flow promoted by negative NAO conditions produces higher δ18O and δ2H values and lower dxs values. Diel isotopic cycles are generally very small as a result of a moderated coastal climate and the counteracting isotopic effects of the sea breeze, local evaporation, and convection. Future losses in Baffin Bay's sea ice extent will likely shift mean annual isotopic compositions toward more summer-like values, and local glacial ice could potentially preserve isotopic evidence of past reductions. These findings highlight the influence that the local environment can have on isotope dynamics and the need for dedicated, multiseason monitoring to fully understand the controls on water vapor isotope variability.
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Mevi, Gabriele, Giovanni Muscari, Pietro Paolo Bertagnolio, Irene Fiorucci, and Giandomenico Pace. "VESPA-22: a ground-based microwave spectrometer for long-term measurements of polar stratospheric water vapor." Atmospheric Measurement Techniques 11, no. 2 (February 23, 2018): 1099–117. http://dx.doi.org/10.5194/amt-11-1099-2018.
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Abstract. The new ground-based 22 GHz spectrometer, VESPA-22 (water Vapor Emission Spectrometer for Polar Atmosphere at 22 GHz) measures the 22.23 GHz water vapor emission line with a bandwidth of 500 MHz and a frequency resolution of 31 kHz. The integration time for a measurement ranges from 6 to 24 h, depending on season and weather conditions. Water vapor spectra are collected using the beam-switching technique. VESPA-22 is designed to operate automatically with little maintenance; it employs an uncooled front-end characterized by a receiver temperature of about 180 K and its quasi-optical system presents a full width at half maximum of 3.5∘. Every 30 min VESPA-22 measures also the sky opacity using the tipping curve technique. The instrument calibration is performed automatically by a noise diode; the emission temperature of this element is estimated twice an hour by observing alternatively a black body at ambient temperature and the sky at an elevation of 60∘. The retrieved profiles obtained inverting 24 h integration spectra present a sensitivity larger than 0.8 from about 25 to 75 km of altitude during winter and from about 30 to 65 km during summer, a vertical resolution from about 12 to 23 km (depending on altitude), and an overall 1σ uncertainty lower than 7 % up to 60 km altitude and rapidly increasing to 20 % at 75 km. In July 2016, VESPA-22 was installed at the Thule High Arctic Atmospheric Observatory located at Thule Air Base (76.5∘ N, 68.8∘ W), Greenland, and it has been operating almost continuously since then. The VESPA-22 water vapor mixing ratio vertical profiles discussed in this work are obtained from 24 h averaged spectra and are compared with version 4.2 of concurrent Aura/Microwave Limb Sounder (MLS) water vapor vertical profiles. In the sensitivity range of VESPA-22 retrievals, the intercomparison from July 2016 to July 2017 between VESPA-22 dataset and Aura/MLS dataset convolved with VESPA-22 averaging kernels shows an average difference within 1.4 % up to 60 km altitude and increasing to about 6 % (0.2 ppmv) at 72 km.
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Moore, T., and G. W. Roberts. "Carrier Phase GPS Navigation to the North Pole." Journal of Navigation 52, no. 1 (January 1999): 80–89. http://dx.doi.org/10.1017/s037346339800808x.
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Over the last few years, on-the-fly integer ambiguity resolution for GPS has proven to be successful over short baselines (<20 km). However, the remaining challenge has been to extend the length of the baseline between the reference station and the mobile receiver, whilst still maintaining the capability of on-the-fly resolution and true carrier-based kinematic positioning. The goal has been to achieve centimetric level positioning at ranges of over 500 km. New techniques have been developed at the University of Nottingham to allow very long baseline integer ambiguity resolution, on-the-fly. A major problem with the use of carrier phase data is that posed by cycle slips. A technique for detecting and correcting cycle slips has been developed, and its use is discussed in this paper. The new technique has been proven through a series of trials, one of which included two flights to the North Pole, performing centimetric level positioning all the way to the pole. For many years, the GD Aero-Systems Course of the Air Warfare Centre based at RAF Cranwell executed a series of equipment flight trials to the North Pole, called the ARIES Flights. In May 1996, the authors were fortunate to take part in both flights, via Iceland and Greenland, to the North Pole. Based on reference stations at Thule Air Base, integer ambiguity resolution was accomplished, on-the-fly, and centimetric level navigation maintained throughout the flights. Earlier trials detailed in the paper demonstrate that the technique can resolve integer ambiguities on-the-fly within a few seconds over a baseline length of approximately 134 km, resulting in an accuracy of 12 cm. The majority of the residual error source for this being the ionosphere.
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Wespes, C., L. Emmons, D. P. Edwards, J. Hannigan, D. Hurtmans, M. Saunois, P. F. Coheur, et al. "Analysis of ozone and nitric acid in spring and summer Arctic pollution using aircraft, ground-based, satellite observations and MOZART-4 model: source attribution and partitioning." Atmospheric Chemistry and Physics Discussions 11, no. 8 (August 22, 2011): 23707–60. http://dx.doi.org/10.5194/acpd-11-23707-2011.
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Abstract. In this paper, we analyze tropospheric O3 together with HNO3 during the POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) program, combining observations and model results. Aircraft observations from the NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) and NOAA ARCPAC (Aerosol, Radiation and Cloud Processes affecting Arctic Climate) campaigns during spring and summer of 2008 are used together with the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) to assist in the interpretation of the observations in terms of the source attribution and transport of O3 and HNO3 into the Arctic. The MOZART-4 simulations reproduce the aircraft observations generally well (within 15 %), but some discrepancies in the model are identified and discussed. The observed correlation of O3 with HNO3 is exploited to evaluate the MOZART-4 model performance for different air mass types (fresh plumes, free troposphere and stratospheric-contaminated air masses). Based on model simulations of O3 and HNO3 tagged by source type and region, we find that the anthropogenic pollution from the Northern Hemisphere is the dominant source of O3 and HNO3 in the Arctic at pressure greater than 400 hPa, and that the stratospheric influence is the principal contribution at pressures less 400 hPa. During the summer, intense Russian fire emissions contribute some amount to the tropospheric columns of both gases over the American sector of the Arctic. North American fire emissions (California and Canada) also show an important impact on tropospheric ozone in the Arctic boundary layer. Additional analysis of tropospheric O3 measurements from ground-based FTIR and from the IASI satellite sounder made at the Eureka (Canada) and Thule (Greenland) polar sites during POLARCAT has been performed using the tagged contributions. It demonstrates the capability of these instruments for observing pollution at Northern high latitudes. Differences between contributions from the sources to the tropospheric columns as measured by FTIR and IASI are discussed in terms of vertical sensitivity associated with these instruments. The first analysis of O3 tropospheric columns observed by the IASI satellite instrument over the Arctic is also provided. Despite its limited vertical sensitivity in the lowermost atmospheric layers, we demonstrate that IASI is capable of detecting low-altitude pollution transported into the Arctic with some limitations.
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Wespes, C., L. Emmons, D. P. Edwards, J. Hannigan, D. Hurtmans, M. Saunois, P. F. Coheur, et al. "Analysis of ozone and nitric acid in spring and summer Arctic pollution using aircraft, ground-based, satellite observations and MOZART-4 model: source attribution and partitioning." Atmospheric Chemistry and Physics 12, no. 1 (January 4, 2012): 237–59. http://dx.doi.org/10.5194/acp-12-237-2012.
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Abstract. In this paper, we analyze tropospheric O3 together with HNO3 during the POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) program, combining observations and model results. Aircraft observations from the NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) and NOAA ARCPAC (Aerosol, Radiation and Cloud Processes affecting Arctic Climate) campaigns during spring and summer of 2008 are used together with the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) to assist in the interpretation of the observations in terms of the source attribution and transport of O3 and HNO3 into the Arctic (north of 60° N). The MOZART-4 simulations reproduce the aircraft observations generally well (within 15%), but some discrepancies in the model are identified and discussed. The observed correlation of O3 with HNO3 is exploited to evaluate the MOZART-4 model performance for different air mass types (fresh plumes, free troposphere and stratospheric-contaminated air masses). Based on model simulations of O3 and HNO3 tagged by source type and region, we find that the anthropogenic pollution from the Northern Hemisphere is the dominant source of O3 and HNO3 in the Arctic at pressures greater than 400 hPa, and that the stratospheric influence is the principal contribution at pressures less 400 hPa. During the summer, intense Russian fire emissions contribute some amount to the tropospheric columns of both gases over the American sector of the Arctic. North American fire emissions (California and Canada) also show an important impact on tropospheric ozone in the Arctic boundary layer. Additional analysis of tropospheric O3 measurements from ground-based FTIR and from the IASI satellite sounder made at the Eureka (Canada) and Thule (Greenland) polar sites during POLARCAT has been performed using the tagged contributions. It demonstrates the capability of these instruments for observing pollution at northern high latitudes. Differences between contributions from the sources to the tropospheric columns as measured by FTIR and IASI are discussed in terms of vertical sensitivity associated with these instruments. The first analysis of O3 tropospheric columns observed by the IASI satellite instrument over the Arctic is also provided. Despite its limited vertical sensitivity in the lowermost atmospheric layers, we demonstrate that IASI is capable of detecting low-altitude pollution transported into the Arctic with some limitations.
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Hawley, Robert L., Zoe R. Courville, Laura M. Kehrl, Eric R. Lutz, Erich C. Osterberg, Thomas B. Overly, and Gifford J. Wong. "Recent accumulation variability in northwest Greenland from ground-penetrating radar and shallow cores along the Greenland Inland Traverse." Journal of Glaciology 60, no. 220 (2014): 375–82. http://dx.doi.org/10.3189/2014jog13j141.
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AbstractAccumulation is a key parameter governing the mass balance of the Greenland ice sheet. Several studies have documented the spatial variability of accumulation over wide spatial scales, primarily using point data, remote sensing or modeling. Direct measurements of spatially extensive, detailed profiles of accumulation in Greenland, however, are rare. We used 400 MHz ground-penetrating radar along the 1009 km route of the Greenland Inland Traverse from Thule to Summit during April and May of 2011, to image continuous internal reflecting horizons. We dated these horizons using ice-core chemistry at each end of the traverse. Using density profiles measured along the traverse, we determined the depth to the horizons and the corresponding water-equivalent accumulation rates. The measured accumulation rates vary from ~0.1 m w.e. a–1 in the interior to ~0.7 m w.e. a–1 near the coast, and correspond broadly with existing published model results, though there are some excursions. Comparison of our recent accumulation rates with those collected along a similar route in the 1950s shows a ~10% increase in accumulation rates over the past 52 years along most of the traverse route. This implies that the increased water vapor capacity of warmer air is increasing accumulation in the interior of Greenland.
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Box, Jason E., Lei Yang, David H. Bromwich, and Le-Sheng Bai. "Greenland Ice Sheet Surface Air Temperature Variability: 1840–2007*." Journal of Climate 22, no. 14 (July 15, 2009): 4029–49. http://dx.doi.org/10.1175/2009jcli2816.1.
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Abstract Meteorological station records and regional climate model output are combined to develop a continuous 168-yr (1840–2007) spatial reconstruction of monthly, seasonal, and annual mean Greenland ice sheet near-surface air temperatures. Independent observations are used to assess and compensate for systematic errors in the model output. Uncertainty is quantified using residual nonsystematic error. Spatial and temporal temperature variability is investigated on seasonal and annual time scales. It is found that volcanic cooling episodes are concentrated in winter and along the western ice sheet slope. Interdecadal warming trends coincide with an absence of major volcanic eruptions. Year 2003 was the only year of 1840–2007 with a warm anomaly that exceeds three standard deviations from the 1951–80 base period. The annual whole ice sheet 1919–32 warming trend is 33% greater in magnitude than the 1994–2007 warming. The recent warming was, however, stronger along western Greenland in autumn and southern Greenland in winter. Spring trends marked the 1920s warming onset, while autumn leads the 1994–2007 warming. In contrast to the 1920s warming, the 1994–2007 warming has not surpassed the Northern Hemisphere anomaly. An additional 1.0°–1.5°C of annual mean warming would be needed for Greenland to be in phase with the Northern Hemispheric pattern. Thus, it is expected that the ice sheet melt rates and mass deficit will continue to grow in the early twenty-first century as Greenland’s climate catches up with the Northern Hemisphere warming trend and the Arctic climate warms according to global climate model predictions.
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Dzik, Anthony J. "Kangerlussuaq: evolution and maturation of a cultural landscape in Greenland." Bulletin of Geography. Socio-economic Series 24, no. 24 (June 1, 2014): 57–69. http://dx.doi.org/10.2478/bog-2014-0014.
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Abstract The cultural landscape reflects the composite influences of the regional physical, cultural, and technological environments. It is a dynamic entity which evolves over time and the perceptions of its human inhabitants is influential in the process. This paper is a descriptive analysis of Kangerlussuaq, a young but maturing settlement located in west Greenland near the inland ice. The site’s natural resource base did not attract permanent settlement by the Inuit or Scandinavian colonists, but in the early days of the World War II, the American military took advantage of the exceptional flying conditions here and established an air base. In time, civilian functions developed as Kangerlussuaq became the hub for air travel in Greenland. A transitory utilitarian settlement was eventually transformed into a more permanent settlement. In recent years there seems to be a growing sense of community and place attachment as the cultural landscape begins to exhibit more of the components of a real ‘town’.
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Solomon, Amy, and Matthew D. Shupe. "A Case Study of Airmass Transformation and Cloud Formation at Summit, Greenland." Journal of the Atmospheric Sciences 76, no. 10 (September 19, 2019): 3095–113. http://dx.doi.org/10.1175/jas-d-19-0056.1.
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Abstract This study investigates cloud formation and transitions in cloud types at Summit, Greenland, during 16–22 September 2010, when a warm, moist air mass was advected to Greenland from lower latitudes. During this period there was a sharp transition between high ice clouds and the formation of a lower stratocumulus deck at Summit. A regional mesoscale model is used to investigate the air masses that form these cloud systems. It is found that the high ice clouds form in originally warm, moist air masses that radiatively cool while being transported to Summit. A sensitivity study removing high ice clouds demonstrates that the primary impact of these clouds at Summit is to reduce cloud liquid water embedded within the ice cloud and water vapor in the boundary layer due to vapor deposition on snow. The mixed-phase stratocumulus clouds form at the base of cold, dry air masses advected from the northwest above 4 km. The net surface radiative fluxes during the stratocumulus period are at least 20 W m−2 larger than during the ice cloud period, indicating that, in seasons other than summer, cold, dry air masses advected to Summit above the boundary layer may radiatively warm the top of the Greenland Ice Sheet more effectively than warm, moist air masses advected from lower latitudes.
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Hall, Dorothy K., Richard S. Williams, Scott B. Luthcke, and Nicolo E. Digirolamo. "Greenland ice sheet surface temperature, melt and mass loss: 2000–06." Journal of Glaciology 54, no. 184 (2008): 81–93. http://dx.doi.org/10.3189/002214308784409170.
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AbstractA daily time series of ‘clear-sky’ surface temperature has been compiled of the Greenland ice sheet (GIS) using 1 km resolution moderate-resolution imaging spectroradiometer (MODIS) land-surface temperature (LST) maps from 2000 to 2006. We also used mass-concentration data from the Gravity Recovery and Climate Experiment (GRACE) to study mass change in relationship to surface melt from 2003 to 2006. The mean LST of the GIS increased during the study period by ∼0.27°C a−1. The increase was especially notable in the northern half of the ice sheet during the winter months. Melt-season length and timing were also studied in each of the six major drainage basins. Rapid (<15 days) and sustained mass loss below 2000 m elevation was triggered in 2004 and 2005 as recorded by GRACE when surface melt begins. Initiation of large-scale surface melt was followed rapidly by mass loss. This indicates that surface meltwater is flowing rapidly to the base of the ice sheet, causing acceleration of outlet glaciers, thus highlighting the metastability of parts of the GIS and the vulnerability of the ice sheet to air-temperature increases. If air temperatures continue to rise over Greenland, increased surface melt will play a large role in ice-sheet mass loss.
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Yau, Audrey M., Michael L. Bender, Alexander Robinson, and Edward J. Brook. "Reconstructing the last interglacial at Summit, Greenland: Insights from GISP2." Proceedings of the National Academy of Sciences 113, no. 35 (August 15, 2016): 9710–15. http://dx.doi.org/10.1073/pnas.1524766113.
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The Eemian (last interglacial, 130–115 ka) was likely the warmest of all interglacials of the last 800 ka, with summer Arctic temperatures 3–5 °C above present. Here, we present improved Eemian climate records from central Greenland, reconstructed from the base of the Greenland Ice Sheet Project 2 (GISP2) ice core. Our record comes from clean, stratigraphically disturbed, and isotopically warm ice from 2,750 to 3,040 m depth. The age of this ice is constrained by measuring CH4 and δ18O of O2, and comparing with the historical record of these properties from the North Greenland Ice Core Project (NGRIP) and North Greenland Eemian Ice Drilling (NEEM) ice cores. The δ18Oice, δ15N of N2, and total air content for samples dating discontinuously from 128 to 115 ka indicate a warming of ∼6 °C between 127–121 ka, and a similar elevation history between GISP2 and NEEM. The reconstructed climate and elevation histories are compared with an ensemble of coupled climate-ice-sheet model simulations of the Greenland ice sheet. Those most consistent with the reconstructed temperatures indicate that the Greenland ice sheet contributed 5.1 m (4.1–6.2 m, 95% credible interval) to global eustatic sea level toward the end of the Eemian. Greenland likely did not contribute to anomalously high sea levels at ∼127 ka, or to a rapid jump in sea level at ∼120 ka. However, several unexplained discrepancies remain between the inferred and simulated histories of temperature and accumulation rate at GISP2 and NEEM, as well as between the climatic reconstructions themselves.
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Reeves, C. E., W. T. Sturges, G. A. Sturrock, K. Preston, D. E. Oram, J. Schwander, R. Mulvaney, J. M. Barnola, and J. Chappellez. "Atmospheric trends of the halon gases from polar firn air." Atmospheric Chemistry and Physics Discussions 5, no. 1 (February 18, 2005): 937–60. http://dx.doi.org/10.5194/acpd-5-937-2005.
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Abstract. Four halons (H-1301, H-1211, H-2402 and H-1202) have been measured in air samples collected from polar firn from Dome Concordia (Dome C), Antarctica, from Devon Island, Canada and the North Greenland Ice Core Project (NGRIP) site, Greenland. H-2402 and H-1202 are reported for the first time in firn air. The depth profiles show the concentrations of all four halons to be zero at the base of the firn thus demonstrating their entirely anthropogenic origin. This is the first evidence of this for H-2402 and H-1202. A 2-D atmospheric model was run to produce historical trends in the atmospheric concentrations at the firn sites, which were then input into a firn diffusion model to produce concentration depth profiles for comparison with the measurements. The firn measurements provide constraints on the atmospheric concentrations in both hemispheres which allow the global emission rates and their latitudinal distribution in the atmospheric model to be evaluated. Global emission trends previously determined from measurements at Cape Grim are found to be consistent with the firn data. Further emissions of H-1202 in recent years (late 1980s onwards) are likely to have come from latitudes mostly south of 40° N, but emissions prior to that may have come from further north. Emissions of H-1211 may also have shifted to latitudes south of 40° N during the late 1980s. The firn data is used to derive atmospheric trends in total organic bromine in the form of halons for both polar regions.
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WASHAM, PETER, KEITH W. NICHOLLS, ANDREAS MÜNCHOW, and LAURIE PADMAN. "Summer surface melt thins Petermann Gletscher Ice Shelf by enhancing channelized basal melt." Journal of Glaciology 65, no. 252 (July 9, 2019): 662–74. http://dx.doi.org/10.1017/jog.2019.43.
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ABSTRACTIncreasing ocean and air temperatures have contributed to the removal of floating ice shelves from several Greenland outlet glaciers; however, the specific contribution of these external forcings remains poorly understood. Here we use atmospheric, oceanographic and glaciological time series data from the ice shelf of Petermann Gletscher, NW Greenland to quantify the forcing of the ocean and atmosphere on the ice shelf at a site ~16 km from the grounding line within a large sub-ice-shelf channel. Basal melt rates here indicate a strong seasonality, rising from a winter mean of 2 m a−1 to a maximum of 80 m a−1 during the summer melt season. This increase in basal melt rates confirms the direct link between summer atmospheric warming around Greenland and enhanced ocean-forced melting of its remaining ice shelves. We attribute this enhanced melting to increased discharge of subglacial runoff into the ocean at the grounding line, which strengthens under-ice currents and drives a greater ocean heat flux toward the ice base.
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Brooks, Kent. "The loss, discovery, and rediscovery of the crew of U.S. Navy LA-9 at Kronborg Glacier, east Greenland." Polar Record 47, no. 2 (December 2, 2010): 181–84. http://dx.doi.org/10.1017/s0032247410000288.
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ABSTRACTIn January 1962, a US Navy aircraft patroling the Denmark Stait mysteriously disappeared. In spite of an international search continuing over several weeks, the crash was first found accidentally 4.5 years later by geologists, but subsequently it was discovered that all the bodies had not been returned. It was not until 2009 that the story was brought to a close with a ceremony at the naval air base in Jacksonville, Florida.
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Reeves, C. E., W. T. Sturges, G. A. Sturrock, K. Preston, D. E. Oram, J. Schwander, R. Mulvaney, J. M. Barnola, and J. Chappellaz. "Trends of halon gases in polar firn air: implications for their emission distributions." Atmospheric Chemistry and Physics 5, no. 8 (August 8, 2005): 2055–64. http://dx.doi.org/10.5194/acp-5-2055-2005.
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Abstract. Four halons (H-1301, H-1211, H-2402 and H-1202) have been measured in air samples collected from polar firn from Dome Concordia (Dome C), Antarctica, from Devon Island, Canada and the North Greenland Ice Core Project (NGRIP) site, Greenland. H-2402 and H-1202 are reported for the first time in firn air. The depth profiles show the concentrations of all four halons to be close to zero (i.e. below the detection limit of 0.001 ppt) at the base of the firn thus demonstrating their entirely anthropogenic origin. This is the first evidence of this for H-2402 and H-1202. A 2-D atmospheric model was run with emissions previously derived using archive air measurements from the southern hemisphere mid-latitudes to produce historical trends in atmospheric concentrations at the firn sites, which were then input into a firn diffusion model to produce concentration depth profiles for comparison with the firn measurements. This comparison provides an evaluation of the model-derived atmospheric concentration histories in both hemispheres and thus an indirect evaluation of the emission rates and distributions used in the atmospheric model. Atmospheric concentration trends produced using global emissions previously determined from measurements at Cape Grim are found to be consistent with the firn data from the southern hemisphere. Further emissions of H-1202 in recent years (late 1980s onwards) are likely to have come from latitudes mostly south of 40° N, but emissions prior to that may have come from further north. Emissions of H-1211 may also have shifted to latitudes south of 40° N during the late 1980s. Following comparison of the atmospheric model output with the firn data, modelled atmospheric trends of total organic bromine in the form of halons were derived for both polar regions.
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Pacini, Astrid, Robert S. Pickart, Frank Bahr, Daniel J. Torres, Andrée L. Ramsey, James Holte, Johannes Karstensen, et al. "Mean Conditions and Seasonality of the West Greenland Boundary Current System near Cape Farewell." Journal of Physical Oceanography 50, no. 10 (October 1, 2020): 2849–71. http://dx.doi.org/10.1175/jpo-d-20-0086.1.
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AbstractThe structure, transport, and seasonal variability of the West Greenland boundary current system near Cape Farewell are investigated using a high-resolution mooring array deployed from 2014 to 2018. The boundary current system is comprised of three components: the West Greenland Coastal Current, which advects cold and fresh Upper Polar Water (UPW); the West Greenland Current, which transports warm and salty Irminger Water (IW) along the upper slope and UPW at the surface; and the Deep Western Boundary Current, which advects dense overflow waters. Labrador Sea Water (LSW) is prevalent at the seaward side of the array within an offshore recirculation gyre and at the base of the West Greenland Current. The 4-yr mean transport of the full boundary current system is 31.1 ± 7.4 Sv (1 Sv ≡ 106 m3 s−1), with no clear seasonal signal. However, the individual water mass components exhibit seasonal cycles in hydrographic properties and transport. LSW penetrates the boundary current locally, through entrainment/mixing from the adjacent recirculation gyre, and also enters the current upstream in the Irminger Sea. IW is modified through air–sea interaction during winter along the length of its trajectory around the Irminger Sea, which converts some of the water to LSW. This, together with the seasonal increase in LSW entering the current, results in an anticorrelation in transport between these two water masses. The seasonality in UPW transport can be explained by remote wind forcing and subsequent adjustment via coastal trapped waves. Our results provide the first quantitatively robust observational description of the boundary current in the eastern Labrador Sea.
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Fyke, Jeremy G., Lionel Carter, Andrew Mackintosh, Andrew J. Weaver, and Katrin J. Meissner. "Surface Melting over Ice Shelves and Ice Sheets as Assessed from Modeled Surface Air Temperatures." Journal of Climate 23, no. 7 (April 1, 2010): 1929–36. http://dx.doi.org/10.1175/2009jcli3122.1.
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Abstract Summer surface melting plays an important role in the evolution of ice shelves and their progenitor ice sheets. To explore the magnitude of surface melt occurring over modern ice shelves and ice sheets in a climate scenario forced by anthropogenic emissions of carbon dioxide (CO2), a coupled climate model was used to simulate the distribution of summer melt at high latitudes and project the future evolution of high-melt regions in both hemispheres. Forcing of the climate model with CO2 emissions resulting from combustion of the present-day fossil-fuel resource base resulted in expansion of high-melt regions, as defined by the contour marking 200 positive degree-days per year, in the Northern Hemisphere and the Antarctic Peninsula and the introduction of high summer melt over the Ross, Ronne-Filchner, and Amery ice shelves as well as a large portion of the West Antarctic Ice Sheet (WAIS) and most of the Greenland Ice Sheet (GIS) by the year 2500. Capping CO2 concentrations at present-day levels avoided significant summer melt over the large Antarctic shelves, the WAIS, and much of the GIS.
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Turton, Jenny V., Philipp Hochreuther, Nathalie Reimann, and Manuel T. Blau. "The distribution and evolution of supraglacial lakes on 79° N Glacier (north-eastern Greenland) and interannual climatic controls." Cryosphere 15, no. 8 (August 20, 2021): 3877–96. http://dx.doi.org/10.5194/tc-15-3877-2021.
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Abstract. The Nioghalvfjerdsfjorden glacier (also known as the 79∘ North Glacier) drains approximately 8 % of the Greenland Ice Sheet. Supraglacial lakes (SGLs), or surface melt ponds, are a persistent summertime feature and are thought to drain rapidly to the base of the glacier and influence seasonal ice velocity. However, seasonal development and spatial distribution of SGLs in the north-east of Greenland are poorly understood, leaving a substantial error in the estimate of meltwater and its impacts on ice velocity. Using results from an automated detection of melt ponds, atmospheric and surface mass balance modelling, and reanalysis products, we investigate the role of specific climatic conditions in melt onset, extent, and duration from 2016 to 2019. The summers of 2016 and 2019 were characterised by above-average air temperatures, particularly in June, as well as a number of rainfall events, which led to extensive melt ponds to elevations up to 1600 m. Conversely, 2018 was particularly cold, with a large accumulated snowpack, which limited the development of lakes to altitudes less than 800 m. There is evidence of inland expansion and increases in the total area of lakes compared to the early 2000s, as projected by future global warming scenarios.
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Skrydstrup, Martin. "Of spheres and squares: Can Sloterdijk help us rethink the architecture of climate science?" Social Studies of Science 46, no. 6 (July 8, 2016): 854–76. http://dx.doi.org/10.1177/0306312716647214.
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This article explores how different visions and values of science translate into different architectural shapes. I bring Peter Sloterdijk’s ‘spherology’ to bear on my ethnographic fieldwork at the NEEM ice core base in Greenland, a significant node in the global infrastructure of climate science. I argue that the visual form of the geodesic dome of the camp materializes specific values and visions of this branch of paleoclimate science, which I elaborate vis-a-vis the pragmatic claims of the scientists/designers and the particular architectural history of Danish ice core drilling in Greenland. I argue that this aesthetic history articulates with Buckminster Fuller’s ideas of a ‘new nature’ and ‘scalar connections’ encapsulated in his geodesic form. Second, I argue that the aesthetic production of space in the camp replicates the modern distinction between science and society, in so far as the lab space is rectangular and the recreational space is spherical. Third, I argue that NEEM scientists and Sloterdijk are essentially engaged in a common project: the scientists work hard to align air bubbles in the cores with atmospheric fluctuations in the hemisphere on the evidentiary terrain of ice, and Sloterdijk attempts to connect micro-uteri with macro-uteri in an attempt to fundamentally rethink space. Fuller’s notion of ‘Spaceship Earth’, appropriated by Sloterdijk in his thinking about anthropogenic climate change, lends itself well to capturing the scalar alignments and the isolated NEEM base – on a mission to save planet Earth. In conclusion, I argue that Sloterdijk’s spherology may serve as a point of departure for rethinking the aesthetic grammar of the architecture of science.
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Henriksen, N. "Completion of field work for the 1:500 000 mapping and regional geological studies in central and western North Greenland." Rapport Grønlands Geologiske Undersøgelse 130 (December 31, 1986): 9–17. http://dx.doi.org/10.34194/rapggu.v130.7935.
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Field activities comprising the second, and final season of the systematic field mapping programme in central and western North Greenland were carried out from June to August 1985. The field investigations were concluded for the 1:500000 map sheet of the area between J. P. Koch Fjord (c. 400 W), in the east, and north-easternmost Washington Land (65°W) in the west; the southern boundary of the map sheet is 81°N (fig. 1). General geological investigations forrned an integral part of the mapping programme. A special source rock project, financed by the Danish Ministry of Energy, was fully integrated with the mapping programme (Christiansen et al., this report). As in 1984 a tent base camp in south-eastern Warming Land served as an operation centre for the expedition. Two chartered Jet Ranger helicopters and a Twin Otter aircraft were based here, and served the expedition groups with transport facilities throughout the season. Mobilisation and demobilisation of the expedition from Denmark were carried out with help from the Royal Danish Air Force, who airlifted the expedition to and from the Canadian Forces Station (CFS) Alert in north-east Ellesmere Island, Canada. Personnel, equipment and fuel were flown into the base camp from Alert with the Twin Otter. The expedition group numbered 40, comprising 12 two-man geological parties, a fourman drilling team and 12 supporting personnel, including aircraft crew members. As in 1984, the operation area extended about 500 km from east to west, and 150-200 km from south to north. The 12 geological teams and the drilling team utilised about 130 camp sites. At the end of the 1985 season, the temporary huts and tents at base camp were dismantled and, together with all the equipment, were taken back to Denmark. Fuel depots and equipment in other parts of the working area, which is part of the North and East Greenland National Park, were also removed.
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Edwards-Opperman, Jonathan, Steven Cavallo, and David Turner. "The Occurrence and Properties of Long-Lived Liquid-Bearing Clouds over the Greenland Ice Sheet and Their Relationship to the North Atlantic Oscillation." Journal of Applied Meteorology and Climatology 57, no. 4 (April 2018): 921–35. http://dx.doi.org/10.1175/jamc-d-17-0230.1.
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AbstractStratiform liquid-bearing clouds (LBCs), defined herein as either pure liquid or mixed-phase clouds, have a large impact on the surface radiation budget across the Arctic. LBCs lasting at least 6 h are observed at Summit, Greenland, year-round with a maximum in occurrence during summer. Mean cloud-base height is below 1 km for 85% of LBC cases identified, 59% have mean liquid water path (LWP) values between 10 and 40 g m−2, and most produce sporadic light ice-phase precipitation. During their occurrence, the atmosphere above the ice sheet is anomalously warm and moist, with southerly winds observed over much of the ice sheet, including at Summit. LBCs that occur when the North Atlantic Oscillation (NAO) is in the negative phase correspond to strong ridging centered over the Greenland Ice Sheet (GIS), allowing for southwesterly flow over the GIS toward Summit. During the positive phase of the NAO, the occurrence of LBCs corresponds to a cyclone located off the southeastern coast of the ice sheet, which leads to easterly-to-southeasterly flow toward Summit. Furthermore, air parcels at Summit frequently originate from below the elevation of Summit, indicating that orographic lift along the ice sheet is a factor in the occurrence of LBCs at Summit. LBCs are more frequently observed during the negative NAO, and both the LWP and precipitation rate are larger in LBCs occurring during this phase. Mean LWP in LBCs occurring during the negative NAO is 15 g m−2 larger than in LBCs occurring during the positive phase.
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Mernild, Sebastian H., Glen E. Liston, and Christopher A. Hiemstra. "Northern Hemisphere Glacier and Ice Cap Surface Mass Balance and Contribution to Sea Level Rise." Journal of Climate 27, no. 15 (July 29, 2014): 6051–73. http://dx.doi.org/10.1175/jcli-d-13-00669.1.
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Abstract Mass changes and mass contribution to sea level rise from glaciers and ice caps (GIC) are key components of the earth’s changing sea level. GIC surface mass balance (SMB) magnitudes and individual and regional mean conditions and trends (1979–2009) were simulated for all GIC having areas greater or equal to 0.5 km2 in the Northern Hemisphere north of 25°N latitude (excluding the Greenland Ice Sheet). Recent datasets, including the Randolph Glacier Inventory (RGI; v. 2.0), the NOAA Global Land One-km Base Elevation Project (GLOBE), and the NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) products, together with recent SnowModel developments, allowed relatively high-resolution (1-km horizontal grid; 3-h time step) simulations of GIC surface air temperature, precipitation, sublimation, evaporation, surface runoff, and SMB. Simulated SMB outputs were calibrated against 1422 direct glaciological annual SMB observations of 78 GIC. The overall GIC mean annual and mean summer air temperature, runoff, and SMB loss increased during the simulation period. The cumulative GIC SMB was negative for all regions. The SMB contribution to sea level rise was largest from Alaska and smallest from the Caucasus. On average, the contribution to sea level rise was 0.51 ± 0.16 mm sea level equivalent (SLE) yr−1 for 1979–2009 and ~40% higher 0.71 ± 0.15 mm SLE yr−1 for the last decade, 1999–2009.
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Winfield, Emily C., Robin J. Rader, Alexander M. Zhivov, Anders Dyrelund, Craig Fredeen, Oddgeir Gudmundsson, and Brent Goering. "HVAC Best Practices in Arctic Climates." E3S Web of Conferences 246 (2021): 08004. http://dx.doi.org/10.1051/e3sconf/202124608004.
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Arctic climates provide unique challenges for designers of HVAC, plumbing, and thermal energy systems. The importance of considering the operation outside air temperatures, system reliability, and building resiliency cannot be understated. The paper describes best practice examples of robust and reliable systems with the emphasis on their redundancy, durability, and functionality. The paper also discusses the most common heating and ventilation system approaches used in arctic climate with the emphasis on the importance of a maintenance program that allows building operators to successfully troubleshoot and maintain buildings in the arctic. More detailed discussion of concepts presented in this paper can be found in the Guide [1] where these concepts are illustrated by best practice examples from U.S. military bases in Alaska and Søndre Strømfjord, the international airport of Greenland that previously was used as a U.S. military base. The paper results from experts’ discussions during the Consultation Forum “Thermal Energy Systems Resilience in Cold/Arctic Climates” [2] and research conducted under the IEA EBC Annex 73, the Environmental Security Technology Certification Program (ESTCP) Project “Technologies Integration to Achieve Resilient, Low-Energy Military Installations” and U.S. Army Program project 633734T1500 under Military Engineering Technology Demonstration. The paper is complementary to the ASHRAE Cold Climate Design Guide [3] with a focus on resilience of thermal energy systems.
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Dionne, Jean-Claude. "Frost-Heaved Bedrock Features: A Valuable Permafrost Indicator." Géographie physique et Quaternaire 37, no. 3 (November 29, 2007): 241–51. http://dx.doi.org/10.7202/032521ar.
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ABSTRACT Frost-heaved bedrock features are periglacial forms produced by the vertical displacement of bedrock fragments. Blocks, frost-wedged from bare bedrock along joints, are raised above the general surface by heave. Although mentioned in the literature of the late 19th century, they have been described and studied in detail only recently. They are widespread in the northern hemisphere, notably in Canada, Greenland and Spitsbergen, where they develop in lithologies with well-developed systems of joints. Commonly, heaved blocks exhibit weathered and lichen-covered surfaces except at their base where freshly exposed rock indicates recent heaving. They result from frost processes, particularly from wedging and heaving due to pressure of the freezing of free-water in joints. Active and most non-active features are located in permafrost regions. The southermost occurrence in the northern hemisphere is the Groulx Mountains, in Québec (51°45'N, alt. 1000 m). The mean annual air temperature for the area of best-developed features ranges from -4° to -100C, with the number of days of frost ranging from 178 to 300. A thin snow cover is common to most sites. Based on climatic data and on the geographical distribution of frost-heaved bedrock features, it is suggested that permafrost occurrence is obvious. Relict features found outside the present-day permafrost zones should indicate former permafrost conditions.
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Drewry, David J. "Children of the ‘Golden Age’ Gordon de Quetteville Robin." Polar Record 39, no. 1 (January 2003): 61–78. http://dx.doi.org/10.1017/s0032247402002814.
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This is the third in a series of biographies entitled ‘Children of the Golden Age,’ the purpose of which is to describe the background and contributions of significant living figures in polar research who began their scientific careers following World War II. Born on 17 January 1921 in Melbourne, Gordon de Quetteville Robin was educated at Wesley College and the University of Melbourne, graduating in physics with an MSc in 1942. Following submarine training in Scotland, he served in HMS Stygian in the Pacific. Soon after commencing as a research student in nuclear physics at Birmingham University, he joined the Falkland Islands Dependencies Survey and was the first base commander at Signy Station in the South Orkney Islands (1947–48). In 1949–52 he was third-in-command on the Norwegian–British–Swedish Antarctic Expedition responsible for the successful oversnow seismic ice thickness campaign. In 1958, following a brief sojourn in Canberra, he was appointed the first full-time director of the Scott Polar Research Institute in Cambridge. During the next 24 years he developed SPRI into a world-class research institute. In the austral summer 1959–60 he undertook research operating from RRS John Biscoe in the Weddell Sea into the penetration of ocean waves into pack ice. During the early 1960s he stimulated development of radio echo sounding (RES) with Dr Stan Evans, which remains the standard technique for ice-thickness measurement. He undertook experimental fieldwork in Northwest Greenland in 1964 and airborne sounding in Canada in 1966. He was responsible for organising international collaborative programmes of airborne RES in Antarctica with American air support, leading fieldwork in 1967–68, 1969–70, and 1974–75. He was elected secretary of the Scientific Committee on Antarctic Research in 1958, serving for 12 years, and was president between 1970 and 1974. In 1975 he developed with Dr Terence Armstrong a postgraduate course in Polar Studies at SPRI. He retired as director in 1982 and continues his interests in glaciology as a senior research associate at SPRI.
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Giovanni Muscari, Claudia Di Biagio, Alcide di Sarra, Marco Cacciani, Svend Erik Ascanius, Pietro Paolo Bertagnolio, Claudio Cesaroni, et al. "Observations of surface radiation and stratospheric processes at Thule Air Base, Greenland, during the IPY." Annals of Geophysics 57, no. 3 (June 18, 2014). http://dx.doi.org/10.4401/ag-6382.
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<p>Ground-based measurements of atmospheric parameters have been carried out for more than 20 years at the Network for the Detection of Atmospheric Composition Change (NDACC) station at Thule Air Base (76.5°N, 68.8°W), on the north-western coast of Greenland. Various instruments dedicated to the study of the lower and middle polar atmosphere are installed at Thule in the framework of a long standing collaboration among Danish, Italian, and US research institutes and universities. This effort aims at monitoring the composition, structure and dynamics of the polar stratosphere, and at studying the Arctic energy budget and the role played by different factors, such as aerosols, water vapour, and surface albedo. During the International Polar Year (IPY), in winter 2008-2009, an intensive measurement campaign was conducted at Thule within the framework of the IPY project “Ozone layer and UV radiation in a changing climate evaluated during IPY” (ORACLE-O3) which sought to improve our understanding of the complex mechanisms that lead to the Arctic stratospheric O<span><sub>3</sub></span> depletion. The campaign involved a lidar system, measuring aerosol backscatter and depolarization ratios up to 35 km and atmospheric temperature profiles from 25 to 70 km altitude, a ground-based millimeter-wave spectrometer (GBMS) used to derive stratospheric mixing ratio profiles of different chemical species involved in the stratospheric ozone depletion cycle, and then ground-based radiometers and a Cimel sunphotometer to study the Arctic radiative budget at the surface. The observations show that the surface radiation budget is mainly regulated by the longwave component throughout most of the year. Clouds have a significant impact contributing to enhance the role of longwave radiation. Besides clouds, water vapour seasonal changes produce the largest modification in the shortwave component at the surface, followed by changes in surface albedo and in aerosol amounts. For what concerns the middle atmosphere, during the first part of winter 2008-2009 the cold polar vortex allowed for the formation of polar stratospheric clouds (PSCs) which were observed above Thule by means of the lidar. This period was also characterized by GBMS measurements of low values of O<span><sub>3</sub></span> due to the catalytic reactions prompted by the PSCs. In mid-January, as the most intense Sudden Stratospheric Warming event ever observed in the Arctic occurred, GBMS and lidar measurements of O<span><sub>3</sub></span>, N<span><sub>2</sub></span>O, CO and temperature described its evolution as it propagated from the upper atmosphere to the lower stratosphere.</p>
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Rydell, Jens, Heikki Roininen, Kenelm Philip, and Ali Karhu. "Lepidoptera collected in the Canadian Arctic during the Tundra Northwest 99 expedition." Entomologica Fennica 12, no. 3 (September 1, 2001). http://dx.doi.org/10.33338/ef.84117.
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During the Swedish-Canadian icebreaker-based expedition to the Nearctic in summer 1999 (July and early August), moths and butterflies (Lepidoptera) were collected during short, helicopter-aided visits to eight sites in the Canadian archipelago, three sites on the Canadian mainland near the arctic coast and also at Thule Air Force Base in north Greenland. Some of the visited sites (notably those on Melville Peninsula, Somerset Island and King William Island) have not previously been investigated with respect to their insect faunas. Several records thus represent species range extensions. They generally corroborate an earlier hypothesis, based on a floristic zonation scheme, which has been used as a framework for understanding the distribution of Arctic butterflies.
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Thomassen, Bjørn, and Johan Ditlev Krebs. "Reconnaissance for noble metals in Precambrian and Palaeogene rocks, Amdrup Fjord, southern East Greenland." GEUS Bulletin, October 31, 2001, 76–80. http://dx.doi.org/10.34194/ggub.v189.5161.
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NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example:
Thomassen, B., & Krebs, J. D. (2001). Reconnaissance for noble metals in Precambrian and Palaeogene rocks, Amdrup Fjord, southern East Greenland. Geology of Greenland Survey Bulletin, 189, 76-80. https://doi.org/10.34194/ggub.v189.5161
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A zone of hydrothermal veins in the Kangerlussuaq region, southern East Greenland, is the focus of a oneyear project by the Geological Survey of Denmark and Greenland (GEUS). The project aims to localise, map, sample and analyse silver-gold-bearing veins in a selected area of Precambrian and Palaeogene rocks north of Amdrup Fjord (Figs 1, 2). This report describes the field work and presents some preliminary results. The study area comprises a c. 3 km wide and 10 km long ridge between Amdrup Fjord and Søndre Syenitgletscher, centred on the 938 m high mountain Flammefjeld (Figs 2, 3). The area is of alpine character with small glaciers and with extensive snow cover most of the year. The field programme was chosen to coincide with the time of minimum snow cover, from 25 July – 23 August. During this period, the major part of the area was investigated on daily foot traverses from four fly camps, helped by helicopter lifts on two occasions. Logistically, the work was part of a larger expedition to East Greenland – EG 2000 – organised by the Danish Lithosphere Centre and GEUS, which is reported on elsewhere (Nielsen et al. 2001, this volume). A temporary field base in Sødalen, some 50 km east of Amdrup Fjord, supported the expedition’s Ecureuil AS 350 helicopter and provided services for the field teams of the various activities attached to EG 2000. Air connections with Iceland were maintained by Twin Otter aircraft operating from a gravel landing strip in Sødalen (Fig. 1).
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Vandecrux, Baptiste, William Colgan, Anne M. Solgaard, Jørgen Peder Steffensen, and Nanna B. Karlsson. "Firn Evolution at Camp Century, Greenland: 1966–2100." Frontiers in Earth Science 9 (March 22, 2021). http://dx.doi.org/10.3389/feart.2021.578978.
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Camp Century is an American military base built in 1959 under the surface of the Greenland ice sheet and decommissioned in 1967. Here, we use outputs from RACMO2.3p2 and CanESM2 climate models, adjusted to meteorological observations, and a firn model to simulate the firn density and temperature at Camp Century between 1966 and 2100. The model output is evaluated against an extensive set of firn 3observations and three Representative Concentration Pathways (RCP2.6, 4.5 and 8.5) are considered as future scenarios. Our model suggests that the upper horizon of the Camp Century debris field – observed at a depth of 32 m in 2017 – will continue to be buried by persistent net accumulation over the next eighty years under all RCP scenarios. This horizon depth will be between 58 and 64 m in 2100, depending on the RCP scenario. We estimate a maximum meltwater percolation depth of 1.1 m under all RCP scenarios. We therefore find it extremely unlikely that surface meltwater interacts with the subsurface debris field at Camp Century before 2100 under all RCP scenarios. Camp Century’s future is representative of the firn area in northwestern Greenland, bound to shift from dry snow to a percolation regime. Our model suggests that 10 m firn temperatures at Camp Century will increase from −24.0°C in 1966 to −21.3, −20.0 and −18.6°C in 2100 under the RCP2.6, 4.5 and 8.5 scenarios, respectively. We reveal a previously unknown warm bias in air temperatures simulated at Camp Century by both RACMO2.3p2 and CanESM2 climate models which needs to be accounted for when using these models to predict melt, firn evolution and sea-level contribution of the Greenland ice sheet. We also present novel in situ measurements of firn compaction rates, which indicate that about 25% of firn compaction of the top 62 m of firn occurs below 20 m depth. This highlights the importance of deep-firn compaction measurements for model evaluation and correction of altimetry products.
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Henriksen, Niels. "North-East Greenland 1997–1998: a new 1:500 000 mapping project in the Caledonian fold belt (72°–75°N)." GEUS Bulletin, December 31, 1998, 119–27. http://dx.doi.org/10.34194/ggub.v180.5095.
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NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example:
Henriksen, N. (1998). North-East Greenland 1997–1998: a new 1:500 000 mapping project in the Caledonian fold belt (72°–75°N). Geology of Greenland Survey Bulletin, 180, 119-127. https://doi.org/10.34194/ggub.v180.5095
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The Geological Survey of Denmark and Greenland (GEUS) continued in 1997 the systematic geological mapping programme for the 1:500 000 regional map series, with initiation of field work on sheet no. 11, which covers part of North-East Greenland. Of the 14 planned map sheets at 1:500 000 which will cover all of Greenland, 11 have been published, and one additional sheet for which field work has been completed is under compilation. Only two areas of Greenland are not yet covered by map sheets of this series: part of North-West Greenland (sheet no 6) and the target for the present project in North-East Greenland (sheet no. 11). The field work for the latter sheet is planned for two seasons, with the first season completed in 1997 and the second and final season to follow in 1998. The map sheet (no. 11) covers the region between Kong Oscar Fjord and the Stauning Alper in the south (72°N) and Kuhn Ø and Grandjean Fjord in the north (75°N, Fig. 1). The western part of this region is dominated by crystalline complexes of the East Greenland Caledonian fold belt. A post-Caledonian sequence of Upper Palaeozoic and Mesozoic sediments and Tertiary plateau basalts and intrusions covers the eastern part of the region. This article focuses on the Caledonian geology, whereas results from the work in the post-Caledonian sediments are described in the article by Stemmerik et al. (1998, this volume). The new Survey work for map sheet 11 represents a reinvestigation of areas extensively studied by geologists of Lauge Koch’s expeditions to East Greenland (1926–58), the principal results of which were compiled by John Haller for the 1:250 000 map sheets covering the region 72°–76°N (Koch & Haller 1971) and incorporated into an impressive regional description of the East Greenland Caledonides (Haller 1971). The Scoresby Sund region to the south of latitude 72°N and the Dove Bugt region to the north of latitude 75°N have already been investigated by the Geological Survey of Greenland (Henriksen 1986, 1997; Higgins 1994) as part of the present ongoing 1:500 000 regional mapping programme. The 1997–1998 mapping project will fill the last remaining gap in the Survey’s 1:500 000 coverage of North-East Greenland. All of North-East Greenland is covered by a set of wide angle black and white vertical aerial photographs taken in the period 1978–87 from an altitude of c. 14 km. On the basis of these aerial photographs and ground control points established by Kort- og Matrikelstyrelsen (National Survey and Cadastre – formerly the Geodetic Institute), new topographical maps of the entire region 72°–75°N, at a scale of 1:100 000, with 100 m contours, are being drawn at the Survey and will serve as a basis for the field investigations and the subsequent geological map compilations. Drawing of the topographic maps in the Survey´s photogrammetric laboratory is combined with photogeological interpretation both prior to and following the field investigations. In addition to establishing a general overview of the regional geology, the project includes activities aimed at supplementing knowledge of the economic potential of the region, in respect to both minerals (Harpøth et al. 1986) and hydrocarbons (Christiansen et al. 1992; Stemmerik et al. 1997). The field work co-ordinated by the Survey included co-operation with a geophysicist from the Alfred Wegener Institute for Polar and Marine Research (AWI), Bremerhaven, who undertook rock magnetic investigations to facilitate interpretation of an AWI aeromagnetic survey, and four Norwegian sedimentologists from Saga Petroleum whose work was integrated with a Survey group working with Mesozoic sediments (Stemmerik et al. 1998, this volume). Logistic support was also given to three groups of geologists from the University of Oslo and three geologists from Massachussetts Institute of Technology, with whom agreements on scientific co-operation had been arranged in advance. Some aspects of the project are based on funding from the Danish National Science Foundation and Carlsberg Foundation, with support for special research topics concerning the pre-Caledonian basement terrain, Caledonian metamorphism, and studies of Upper Proterozoic carbonate sediments. The field investigations in 1997 were carried out during a seven week field season between early July and late August with participation of a total of 38 persons, including 32 geologists (Henriksen 1998). The work was supported by two helicopters and a small, fixed wing, Twin Otter aircraft, which operated from Mestersvig, a former airport which is kept open for limited special operations by the military sledge patrol Sirius. The GEUS group benefitted substantially from base facilities at Mestersvig, organised and manned by the Danish Polar Center (DPC). Transport between Mestersvig and Denmark was carried out by the Royal Danish Air Force (RDAF) using a C-130 Hercules aircraft.