Journal articles: 'Glacial-Interglacial cycle'

1

Zeng, N. "Quasi-100 ky glacial-interglacial cycles triggered by subglacial burial carbon release." Climate of the Past 3, no. 1 (March 2, 2007): 135–53. http://dx.doi.org/10.5194/cp-3-135-2007.

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Abstract. A mechanism is proposed in which climate, carbon cycle and icesheets interact with each other to produce a feedback that can lead to quasi-100 ky glacial-interglacial cycles. A central process is the burial and preservation of organic carbon by icesheets which contributes to the observed glacial-interglacial CO2 change (the glacial burial hypothesis, Zeng, 2003). Allowing carbon cycle to interact with physical climate, here I further hypothesize that deglaciation can be triggered by the ejection of glacial burial carbon when a major icesheet grows to sufficiently large size after a prolonged glaciation so that subglacial transport becomes significant. Glacial inception may be initiated by CO2 drawdown due to a relaxation from a high but transient interglacial CO2 value as the land-originated CO2 invades into deep ocean via thermohaline circulation and CaCO3 compensation. Also important for glacial inception may be the CO2 uptake by vegetation and soil regrowth in the previously ice-covered regions. When tested in a fully coupled Earth system model with comprehensive carbon cycle components and semi-empirical physical climate components, it produced under certain parameter regimes self-sustaining glacial-interglacial cycles with durations of 93 ky, CO2 changes of 90 ppmv, temperature changes of 6°C. Since the 100 ky cycles can not be easily explained by the Milankovitch astronomical forcing alone, this carbon-climate-icesheet mechanism provides a strong feedback that could interact with external forcings to produce the major observed Quaternary climatic variations. It is speculated that some glacial terminations may be triggered by this internal feedback while others by orbital forcing. Some observable consequences are highlighted that may support or falsify the theory.

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Zeng, N. "Quasi-100 ky glacial-interglacial cycles triggered by subglacial burial carbon release." Climate of the Past Discussions 2, no. 4 (July 7, 2006): 371–97. http://dx.doi.org/10.5194/cpd-2-371-2006.

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Abstract. A new mechanism is proposed in which climate, carbon cycle and icesheets interact with each other to produce a feedback that can produce quasi-100 ky glacial-interglacial cycles. A key process is the burial and preservation of organic carbon by icesheets. The switch from glacial maximum to deglaciation is triggered by the ejection of glacial burial carbon when icesheets grow to sufficiently large size and subglacial transport becomes significant. Glacial inception is initiated by CO2 drawdown due to a ''rebound'' from a high but transient interglacial CO2 value as the land-originated CO2 invades into deep ocean via thermohaline circulation and CaCO3 compensation. Also important for glacial inception is the CO2 uptake by vegetation regrowth in the previously ice-covered boreal regions. When tested using a fully coupled Earth system model with comprehensive carbon cycle components and semi-empirical physical climate components, it produced self-sustaining glacial-interglacial cycles of duration about 93 ky, CO2 change of 90 ppmv, temperature change of 6°C under certain parameter regimes. Since the 100 ky cycles can not be easily explained by the weak Milankovitch astronomical forcing alone, this carbon-climate mechanism provides a strong feedback that could interact with external forcings to produce the major observed Quaternary climatic variations.

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Andersen, Bjørn G., and Jan Mangerud. "The last interglacial-glacial cycle in fennoscandia." Quaternary International 3-4 (January 1989): 21–29. http://dx.doi.org/10.1016/1040-6182(89)90070-0.

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4

Houmark-Nielsen, Michael. "The last interglacial-glacial cycle in Denmark." Quaternary International 3-4 (January 1989): 31–39. http://dx.doi.org/10.1016/1040-6182(89)90071-2.

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Brovkin, V., A. Ganopolski, D. Archer, and G. Munhoven. "Glacial CO2 cycle as a succession of key physical and biogeochemical processes." Climate of the Past 8, no. 1 (February 9, 2012): 251–64. http://dx.doi.org/10.5194/cp-8-251-2012.

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Abstract. During glacial-interglacial cycles, atmospheric CO2 concentration varied by about 100 ppmv in amplitude. While testing mechanisms that have led to the low glacial CO2 level could be done in equilibrium model experiments, an ultimate goal is to explain CO2 changes in transient simulations through the complete glacial-interglacial cycle. The computationally efficient Earth System model of intermediate complexity CLIMBER-2 is used to simulate global biogeochemistry over the last glacial cycle (126 kyr). The physical core of the model (atmosphere, ocean, land and ice sheets) is driven by orbital changes and reconstructed radiative forcing from greenhouses gases, ice, and aeolian dust. The carbon cycle model is able to reproduce the main features of the CO2 changes: a 50 ppmv CO2 drop during glacial inception, a minimum concentration at the last glacial maximum 80 ppmv lower than the Holocene value, and an abrupt 60 ppmv CO2 rise during the deglaciation. The model deep ocean δ13C also resembles reconstructions from deep-sea cores. The main drivers of atmospheric CO2 evolve in time: changes in sea surface temperatures and in the volume of bottom water of southern origin control atmospheric CO2 during the glacial inception and deglaciation; changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycle, respectively. These feedback mechanisms could also significantly impact the ultimate climate response to the anthropogenic perturbation.

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Willeit, M., A. Ganopolski, R. Calov, and V. Brovkin. "Mid-Pleistocene transition in glacial cycles explained by declining CO2and regolith removal." Science Advances 5, no. 4 (April 2019): eaav7337. http://dx.doi.org/10.1126/sciadv.aav7337.

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Variations in Earth’s orbit pace the glacial-interglacial cycles of the Quaternary, but the mechanisms that transform regional and seasonal variations in solar insolation into glacial-interglacial cycles are still elusive. Here, we present transient simulations of coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. We show that a gradual lowering of atmospheric CO2and regolith removal are essential to reproduce the evolution of climate variability over the Quaternary. The long-term CO2decrease leads to the initiation of Northern Hemisphere glaciation and an increase in the amplitude of glacial-interglacial variations, while the combined effect of CO2decline and regolith removal controls the timing of the transition from a 41,000- to 100,000-year world. Our results suggest that the current CO2concentration is unprecedented over the past 3 million years and that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary.

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Ganopolski, Andrey, and Victor Brovkin. "Simulation of climate, ice sheets and CO2 evolution during the last four glacial cycles with an Earth system model of intermediate complexity." Climate of the Past 13, no. 12 (November 29, 2017): 1695–716. http://dx.doi.org/10.5194/cp-13-1695-2017.

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Abstract. In spite of significant progress in paleoclimate reconstructions and modelling of different aspects of the past glacial cycles, the mechanisms which transform regional and seasonal variations in solar insolation into long-term and global-scale glacial–interglacial cycles are still not fully understood – in particular, in relation to CO2 variability. Here using the Earth system model of intermediate complexity CLIMBER-2 we performed simulations of the co-evolution of climate, ice sheets, and carbon cycle over the last 400 000 years using the orbital forcing as the only external forcing. The model simulates temporal dynamics of CO2, global ice volume, and other climate system characteristics in good agreement with paleoclimate reconstructions. These results provide strong support for the idea that long and strongly asymmetric glacial cycles of the late Quaternary represent a direct but strongly nonlinear response of the Northern Hemisphere ice sheets to orbital forcing. This response is strongly amplified and globalised by the carbon cycle feedbacks. Using simulations performed with the model in different configurations, we also analyse the role of individual processes and sensitivity to the choice of model parameters. While many features of simulated glacial cycles are rather robust, some details of CO2 evolution, especially during glacial terminations, are sensitive to the choice of model parameters. Specifically, we found two major regimes of CO2 changes during terminations: in the first one, when the recovery of the Atlantic meridional overturning circulation (AMOC) occurs only at the end of the termination, a pronounced overshoot in CO2 concentration occurs at the beginning of the interglacial and CO2 remains almost constant during the interglacial or even declines towards the end, resembling Eemian CO2 dynamics. However, if the recovery of the AMOC occurs in the middle of the glacial termination, CO2 concentration continues to rise during the interglacial, similar to the Holocene. We also discuss the potential contribution of the brine rejection mechanism for the CO2 and carbon isotopes in the atmosphere and the ocean during the past glacial termination.

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8

Han, Yongming, Zhisheng An, Jennifer R. Marlon, Raymond S. Bradley, Changlin Zhan, Richard Arimoto, Youbin Sun, et al. "Asian inland wildfires driven by glacial–interglacial climate change." Proceedings of the National Academy of Sciences 117, no. 10 (February 24, 2020): 5184–89. http://dx.doi.org/10.1073/pnas.1822035117.

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Wildfire can influence climate directly and indirectly, but little is known about the relationships between wildfire and climate during the Quaternary, especially how wildfire patterns varied over glacial–interglacial cycles. Here, we present a high-resolution soot record from the Chinese Loess Plateau; this is a record of large-scale, high-intensity fires over the past 2.6 My. We observed a unique and distinct glacial–interglacial cyclicity of soot over the entire Quaternary Period synchronous with marine δ18O and dust records, which suggests that ice-volume-modulated aridity controlled wildfire occurrences, soot production, and dust fluxes in central Asia. The high-intensity fires were also found to be anticorrelated with global atmospheric CO2 records over the past eight glacial–interglacial cycles, implying a possible connection between the fires, dust, and climate mediated through the iron cycle. The significance of this hypothetical connection remains to be determined, but the relationships revealed in this study hint at the potential importance of wildfire for the global climate system.

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9

Brovkin, V., A. Ganopolski, D. Archer, and G. Munhoven. "Glacial CO2 cycle as a succession of key physical and biogeochemical processes." Climate of the Past Discussions 7, no. 3 (May 30, 2011): 1767–95. http://dx.doi.org/10.5194/cpd-7-1767-2011.

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Abstract. During glacial-interglacial cycles, atmospheric CO2 concentration varied by about 100 ppmv in amplitude. While testing mechanisms that had led to the low glacial CO2 level could be done in equilibrium model experiments, an ultimate goal is to explain CO2 changes in transient simulations through the complete glacial-interglacial cycle. A computationally efficient Earth System model of intermediate complexity CLIMBER-2 is used to simulate global biogeochemistry over the last glacial cycle (126 kyr). The physical core of the model (atmosphere, ocean, land and ice sheets) is driven by orbital changes and reconstructed radiative forcing from greenhouses gases, ice, and aeolian dust. The carbon cycle model is able to reproduce the main features of the CO2 changes: a 50 ppmv CO2 drop during glacial inception, a minimum concentration at the last glacial maximum by 80 ppmv lower than the Holocene value, and an abrupt 60 ppmv CO2 rise during the deglaciation. The model deep ocean δ13C also resembles reconstructions from deep-sea cores. The main drivers of atmospheric CO2 evolve with time: changes in sea surface temperatures and in the volume of bottom water of southern origin controls atmospheric CO2 during the glacial inception and deglaciation, while changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycle, respectively. These feedback mechanisms could also significantly impact the ultimate climate response to the anthropogenic perturbation.

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10

Kotlyakov, V. M., and K. Lorius. "Global changes during the latest glacial‐interglacial cycle." Polar Geography and Geology 16, no. 2 (April 1992): 89–113. http://dx.doi.org/10.1080/10889379209377479.

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11

Carson, Jake, Michel Crucifix, Simon Preston, and Richard D. Wilkinson. "Bayesian model selection for the glacial–interglacial cycle." Journal of the Royal Statistical Society: Series C (Applied Statistics) 67, no. 1 (March 17, 2017): 25–54. http://dx.doi.org/10.1111/rssc.12222.

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12

François, Louis, Hugues Faure, and Jean-Luc Probst. "The global carbon cycle and its changes over glacial–interglacial cycles." Global and Planetary Change 33, no. 1-2 (June 2002): vii—viii. http://dx.doi.org/10.1016/s0921-8181(02)00056-5.

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13

Naik, D. K., R. Saraswat, N. Khare, A. C. Pandey, and R. Nigam. "Hydrographic changes in the Agulhas Recirculation Region during the late Quaternary." Climate of the Past 10, no. 2 (April 15, 2014): 745–58. http://dx.doi.org/10.5194/cp-10-745-2014.

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Abstract. The strength of Southern Hemisphere westerlies, as well as the positions of the subtropical front (STF), Agulhas Current (AC) and Agulhas Return Current (ARC) control the hydrography of the southwestern Indian Ocean. Although equatorward migration of the STF and reduction in Agulhas leakage were reported during the last glacial period, the fate of ARC during the last glacial–interglacial cycle is not clear. Therefore, in order to understand changes in the position and strength of ARC during the last glacial–interglacial cycle, here we reconstruct hydrographic changes in the southwestern Indian Ocean from temporal variation in planktic foraminiferal abundance, stable isotopic ratio (δ18O) and trace elemental ratio (Mg/Ca) of planktic foraminifera Globigerina bulloides in a core collected from the Agulhas Recirculation Region (ARR) in the southwestern Indian Ocean. Increased abundance of G. bulloides suggests that the productivity in the southwestern Indian Ocean increased during the last glacial period which confirms previous reports of high glacial productivity in the Southern Ocean. The increased productivity was likely driven by the intensified Southern Hemisphere westerlies supported by an equatorward migration of the subtropical front. Increase in relative abundance of Neogloboquadrina incompta suggests seasonally strong thermocline and enhanced advection of southern source water in the southwestern Indian Ocean as a result of strengthened ARC, right through MIS 4 to MIS 2, during the last glacial period. Therefore, it is inferred that over the last glacial–interglacial cycle, the hydrography of the southwestern Indian Ocean was driven by strengthened westerlies, ARC as well as a migrating subtropical front.

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Naik, D. K., R. Saraswat, N. Khare, A. C. Pandey, and R. Nigam. "Migrating subtropical front and Agulhas Return Current affect the southwestern Indian Ocean during the late Quaternary." Climate of the Past Discussions 9, no. 5 (September 30, 2013): 5521–51. http://dx.doi.org/10.5194/cpd-9-5521-2013.

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Abstract. The position of sub-tropical front (STF), Agulhas Current (AC) and Agulhas Return Current (ARC) controls the hydrography of southwestern Indian Ocean. Although, equator-ward migration of STF and reduction in Agulhas leakage has been reported during the last glacial period, the fate of ARC during the last glacial–interglacial cycle is not clear. Therefore, in order to understand changes in the position and strength of ARC during the last glacial–interglacial cycle, here we reconstruct hydrographic changes in the southwestern Indian Ocean from temporal variation in planktic foraminiferal abundance, stable isotopic ratio (δ18O) and trace metal ratio (Mg / Ca) of planktic foraminifera Globigerina bulloides in a core collected from the Agulhas Retroflection Region (ARR) in the southwestern Indian Ocean. Increased abundance of G. bulloides suggests that the productivity in the southwestern Indian Ocean increased during glacial period which confirms previous reports of high glacial productivity in the Southern Ocean. The increased productivity was likely driven by a combination of equator-ward migration of subtropical front and westerlies. Increase in relative abundance of Neogloboquadrina pachyderma Dextral suggests warming of ARR leading to strong thermocline in the southwestern Indian Ocean during the last glacial period. We suggest that the warming of Agulhas Retroflection Region was driven by strengthened ARC which shifted to the east of its present location, thus bringing warmer and saltier water to the southwestern Indian Ocean. Therefore, it is inferred that over the last glacial–interglacial cycle, the hydrography of southwestern Indian Ocean was driven by an eastward shift of retroflection region as well as migrating subtropical front.

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15

Kukla, George J., Amy C. Clement, Mark A. Cane, Joyce E. Gavin, and Stephen E. Zebiak. "Last Interglacial and Early Glacial ENSO." Quaternary Research 58, no. 1 (July 2002): 27–31. http://dx.doi.org/10.1006/qres.2002.2327.

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AbstractAlthough the link between insolation and climate is commonly thought to be in the high northern latitudes in summer, our results show that the start of the last glaciation in marine isotope stage (MIS) 5d was associated with a change of insolation during the transitional seasons in the low latitudes. A simplified coupled ocean-atmosphere model shows that changes in the seasonal cycle of insolation could have altered El Niño Southern Oscillation (ENSO) variability so that there were almost twice as many warm ENSO events in the early glacial than in the last interglacial. This indicates that ice buildup in the cooled high latitudes could have been accelerated by a warmed tropical Pacific.

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Jones, Jacob, Karen E. Kohfeld, Helen Bostock, Xavier Crosta, Melanie Liston, Gavin Dunbar, Zanna Chase, Amy Leventer, Harris Anderson, and Geraldine Jacobsen. "Sea ice changes in the southwest Pacific sector of the Southern Ocean during the last 140 000 years." Climate of the Past 18, no. 3 (March 14, 2022): 465–83. http://dx.doi.org/10.5194/cp-18-465-2022.

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Abstract. Sea ice expansion in the Southern Ocean is believed to have contributed to glacial–interglacial atmospheric CO2 variability by inhibiting air–sea gas exchange and influencing the ocean's meridional overturning circulation. However, limited data on past sea ice coverage over the last 140 ka (a complete glacial cycle) have hindered our ability to link sea ice expansion to oceanic processes that affect atmospheric CO2 concentration. Assessments of past sea ice coverage using diatom assemblages have primarily focused on the Last Glacial Maximum (∼21 ka) to Holocene, with few quantitative reconstructions extending to the onset of glacial Termination II (∼135 ka). Here we provide new estimates of winter sea ice concentrations (WSIC) and summer sea surface temperatures (SSST) for a full glacial–interglacial cycle from the southwestern Pacific sector of the Southern Ocean using the modern analog technique (MAT) on fossil diatom assemblages from deep-sea core TAN1302-96. We examine how the timing of changes in sea ice coverage relates to ocean circulation changes and previously proposed mechanisms of early glacial CO2 drawdown. We then place SSST estimates within the context of regional SSST records to better understand how these surface temperature changes may be influencing oceanic CO2 uptake. We find that winter sea ice was absent over the core site during the early glacial period until MIS 4 (∼65 ka), suggesting that sea ice may not have been a major contributor to early glacial CO2 drawdown. Sea ice expansion throughout the glacial–interglacial cycle, however, appears to coincide with observed regional reductions in Antarctic Intermediate Water production and subduction, suggesting that sea ice may have influenced intermediate ocean circulation changes. We observe an early glacial (MIS 5d) weakening of meridional SST gradients between 42 and 59∘ S throughout the region, which may have contributed to early reductions in atmospheric CO2 concentrations through its impact on air–sea gas exchange.

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Tziperman, Eli, and Hezi Gildor. "The Stabilization of the Thermohaline Circulation by the Temperature–Precipitation Feedback." Journal of Physical Oceanography 32, no. 9 (September 1, 2002): 2707–14. http://dx.doi.org/10.1175/1520-0485-32.9.2707.

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Abstract The meridional freshwater flux in the atmosphere, and hence the strength of the hydrological cycle, undergoes variations on glacial–interglacial as well as on some shorter timescales. A significant portion of these changes to the hydrological cycle are due to the temperature–precipitation feedback according to which there is more precipitation over the higher latitudes during warm periods when the moisture holding capacity of the atmosphere is higher. It is proposed here that this feedback may play an important role in determining the stability of the thermohaline circulation (THC). The THC stability to different parameterizations of the meridional atmospheric freshwater flux is therefore investigated using a simple box model of the ocean, atmosphere, and sea ice. It is demonstrated that parameterizations that are consistent with the temperature–precipitation feedback, and hence with the observed variations of the hydrological cycle during glacial–interglacial cycles, stabilize the THC for a wide range of forcing parameters.

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Reed, J. M., A. Cvetkoska, Z. Levkov, H. Vogel, and B. Wagner. "The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania): testing diatom response to climate." Biogeosciences Discussions 7, no. 3 (June 17, 2010): 4689–714. http://dx.doi.org/10.5194/bgd-7-4689-2010.

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Abstract. Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacial-interglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 15–7.4 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, following by a post-Medieval cooling trend. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom concentration data in future studies.

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Reed, J. M., A. Cvetkoska, Z. Levkov, H. Vogel, and B. Wagner. "The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania): testing diatom response to climate." Biogeosciences 7, no. 10 (October 13, 2010): 3083–94. http://dx.doi.org/10.5194/bg-7-3083-2010.

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Abstract. Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacial-interglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 14.7–6.9 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, followed by a post-Medieval loss of diversity which is consistent with cooling, but not definitive. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom accumulation data in future studies.

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Wood, David L., and Anthony D. Barnosky. "Middle Pleistocene Climate Change in the Colorado Rocky Mountains Indicated by Fossil Mammals from Porcupine Cave." Quaternary Research 41, no. 3 (May 1994): 366–75. http://dx.doi.org/10.1006/qres.1994.1041.

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AbstractFossiliferous sediments from The Pit Locality in Porcupine Cave, Park County, Colorado, span multiple glacial and interglacial cycles between ca. 800,000 and 400,000 yr B.P. at 2900 m elevation. The uppermost cycle probably represents oxygenisotope glacial Stage 12 (stratigraphic Levels 4 and 3) and interglacial Stage 11 (Levels 3, 2, and 1) as determined by arvicoline biostratigraphic data that place the sequence between 487,000 and 365,000 yr B.P. A no-analog assemblage comprising the bog lemming Mictomys meltoni (of the M. borealis lineage) and the sagebrush vole Lemmiscus curtatus (=Lagurus curtatus) characterizes both the glacial and the interglacial deposits. Climatographs for these two species suggest that, compared to present conditions, the following local climatic limits can be imposed on oxygenisotope Stages 12 and 11: (1) January effective moisture was greater, resulting from average temperatures of at least 5°C cooler and/or at least 15 mm more precipitation; (2) January solar radiation was lower by at least 75 Langleys; (3) effective July solar radiation might have been lower by at least 50 Langleys. Seasonal temperature extremes were not necessarily different from those of the present, but seasonal precipitation was more equable. Relative abundance of mammal taxa and sedimentological data indicate that aridity increased at the onset of the interglacial.

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Miller, Gifford H., Hans Petter Sejrup, Scott J. Lehman, and Steven L. Forman. "The last glacial-interglacial cycle, western Spitsbergen, Svalbard archipelago." Polar Research 5, no. 3 (January 12, 1987): 279–80. http://dx.doi.org/10.3402/polar.v5i3.6887.

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MILLER, GIFFORD H., HANS PETTER SEJRUP, SCOTT J. LEHMAN, and STEVEN L. FORMAN. "The last glacial-interglacial cycle, western Spitsbergen, Svalbard archipelago." Polar Research 5, no. 3 (December 1987): 279–80. http://dx.doi.org/10.1111/j.1751-8369.1987.tb00549.x.

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23

Bowen, D. Q. "The Last Interglacial-Glacial Cycle in the British Isles." Quaternary International 3-4 (January 1989): 41–47. http://dx.doi.org/10.1016/1040-6182(89)90072-4.

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Grüger, Eberhard. "Palynostratigraphy of the last interglacial/glacial cycle in Germany." Quaternary International 3-4 (January 1989): 69–79. http://dx.doi.org/10.1016/1040-6182(89)90075-x.

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van Husen, Dirk. "The last interglacial-glacial cycle in the eastern Alps." Quaternary International 3-4 (January 1989): 115–21. http://dx.doi.org/10.1016/1040-6182(89)90081-5.

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O'Neill, Cameron M., Andrew McC Hogg, Michael J. Ellwood, Bradley N. Opdyke, and Stephen M. Eggins. "Sequential changes in ocean circulation and biological export productivity during the last glacial–interglacial cycle: a model–data study." Climate of the Past 17, no. 1 (January 15, 2021): 171–201. http://dx.doi.org/10.5194/cp-17-171-2021.

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Abstract. We conduct a model–data analysis of the marine carbon cycle to understand and quantify the drivers of atmospheric CO2 concentration during the last glacial–interglacial cycle. We use a carbon cycle box model, “SCP-M”, combined with multiple proxy data for the atmosphere and ocean, to test for variations in ocean circulation and Southern Ocean biological export productivity across marine isotope stages spanning 130 000 years ago to the present. The model is constrained by proxy data associated with a range of environmental conditions including sea surface temperature, salinity, ocean volume, sea-ice cover and shallow-water carbonate production. Model parameters for global ocean circulation, Atlantic meridional overturning circulation and Southern Ocean biological export productivity are optimized in each marine isotope stage against proxy data for atmospheric CO2, δ13C and Δ14C and deep-ocean δ13C, Δ14C and CO32-. Our model–data results suggest that global overturning circulation weakened during Marine Isotope Stage 5d, coincident with a ∼ 25 ppm fall in atmospheric CO2 from the last interglacial period. There was a transient slowdown in Atlantic meridional overturning circulation during Marine Isotope Stage 5b, followed by a more pronounced slowdown and enhanced Southern Ocean biological export productivity during Marine Isotope Stage 4 (∼ −30 ppm). In this model, the Last Glacial Maximum was characterized by relatively weak global ocean and Atlantic meridional overturning circulation and increased Southern Ocean biological export productivity (∼ −20 ppm during MIS 3 and MIS 2). Ocean circulation and Southern Ocean biological export productivity returned to modern values by the Holocene period. The terrestrial biosphere decreased by 385 Pg C in the lead-up to the Last Glacial Maximum, followed by a period of intense regrowth during the last glacial termination and the Holocene (∼ 600 Pg C). Slowing ocean circulation, a colder ocean and to a lesser extent shallow carbonate dissolution contributed ∼ −70 ppm to atmospheric CO2 in the ∼ 100 000-year lead-up to the Last Glacial Maximum, with a further ∼ −15 ppm contributed during the glacial maximum. Our model results also suggest that an increase in Southern Ocean biological export productivity was one of the ingredients required to achieve the Last Glacial Maximum atmospheric CO2 level. We find that the incorporation of glacial–interglacial proxy data into a simple quantitative ocean transport model provides useful insights into the timing of past changes in ocean processes, enhancing our understanding of the carbon cycle during the last glacial–interglacial period.

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Glennie, Kenneth, Steven Fryberger, Caroline Hern, Nicholas Lancaster, James Teller, Vachaspati Pandey, and Ashok Singhvi. "Geological importance of luminescence dates in Oman and the Emirates: An overview." Geochronometria 38, no. 3 (September 1, 2011): 259–71. http://dx.doi.org/10.2478/s13386-011-0037-2.

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AbstractIn the Wahiba Sands of eastern Oman, luminescence dating of sands enables us to relate wind activity to climatic variations and the monsoon cycle. These changes resulted from Polar glacial/interglacial cyclicity and changes in global sea levels and wind strengths. Luminescence dates show that development of the Sands began over 230 ka ago when the sand-driving winds were the locally arid, northward-blowing SW Monsoon.During late Quaternary low sea levels, the Tigris-Euphrates river system flowed across the floor of the Persian/Arabian Gulf to the Gulf of Oman SE of the Strait of Hormuz. OSL-dated sands containing calcareous bioclastic fragments deflated from the exposed Gulf floor during glacial low-water periods indicate that during the last glacial cycle, and at least one earlier cycle (∼120–200 ka and possibly as far back as 291 ka), the floor of the Arabian Gulf was exposed. This is deduced from the presence of aeolian dune sands containing bioclastic detritus on the coastal plain of the Emirates and south into Al Liwa (Abu Dhabi), which were built by northern “Shamal” winds. Those calcareous sands now locally overlie sabkhas formed during interglacial high sea levels. Within the present interglacial, marine flooding of the Gulf occurred between about 12 and 6 ka.

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Vega, Rodrigo M., Mauricio Mella, Sven N. Nielsen, and Mario Pino. "Stratigraphy and sedimentology of a late Pleistocene incised valley fill: a depositional and paleogeographic model for “Cancagua” deposits in north-western Patagonia, Chile." Andean Geology 45, no. 2 (March 5, 2018): 161. http://dx.doi.org/10.5027/andgeov45n2-3030.

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Late Pleistocene sedimentary deposits outcropping around Valdivia city, locally known as Cancagua, have been subject of contrasting interpretations, from glacial to interglacial sediments. Opposing views emerge from focusing on upstream or coastal sedimentary controls, within a zone were these potentially overlap through a full glacial cycle. Here we present the first detailed facies analysis and a broad chronological framework, reconciling previous interpretations in a single paleogeographic model that encompasses the last glacial cycle. Seven facies associations are described, interpreted as an estuarine complex developed primarily during the last glacial cycle’s highstand, yet accumulating sediments during a substantial part of the falling stage. These results offer the opportunity to extend paleoenvironmental records through a full glacial cycle in northern Patagonia.

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Dupont, Lydie M., Xueqin Zhao, Christopher Charles, John Tyler Faith, and David Braun. "Continuous vegetation record of the Greater Cape Floristic Region (South Africa) covering the past 300 000 years (IODP U1479)." Climate of the Past 18, no. 1 (January 6, 2022): 1–21. http://dx.doi.org/10.5194/cp-18-1-2022.

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Abstract. The Greater Cape Floristic Region (GCFR) of South Africa is a biodiversity hotspot of global significance, and its archeological record has substantially contributed to the understanding of modern human origins. For both reasons, the climate and vegetation history of southwestern South Africa is of interest to numerous fields. Currently known paleoenvironmental records cover the Holocene, the last glacial–interglacial transition and parts of the last glaciation but do not encompass a full glacial–interglacial cycle. To obtain a continuous vegetation record of the last Pleistocene glacial–interglacial cycles, we studied pollen, spores and micro-charcoal of deep-sea sediments from IODP Site U1479 retrieved from SW of Cape Town. We compare our palynological results of the Pleistocene with previously published results of Pliocene material from the same site. We find that the vegetation of the GCFR, in particular fynbos and afrotemperate forest, responds to precessional forcing of climate. The micro-charcoal record confirms the importance of fires in the fynbos vegetation. Ericaceae-rich and Asteraceae-rich types of fynbos could extend on the western part of the Paleo-Agulhas Plain (PAP), which emerged during periods of low sea level of the Pleistocene.

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Köhler, P., and H. Fischer. "Proposing a mechanistic understanding of changes in atmospheric CO2 during the last 740 000 years." Climate of the Past Discussions 2, no. 1 (February 14, 2006): 1–42. http://dx.doi.org/10.5194/cpd-2-1-2006.

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Abstract. Atmospheric carbon dioxide (CO2) measured in Antarctic ice cores shows a natural variability of 80 to 100 ppmv during the last four glacial cycles and variations of approximately 60 ppmv in the two cycles between 410 and 650 kyr BP. We here use dust and the isotopic temperature proxy deuterium (δD) from the EPICA Dome C Antarctic ice core covering the last 740 kyr together with other paleo-climatic records to force the ocean/atmosphere/biosphere box model of the global carbon cycle BICYCLE in a forward mode over this time in order to reconstruct the natural variability of pCO2. Our simulation results covered by our proposed scenario are based on process understanding gained previously for carbon cycle variations during Termination I. These results match the pCO2 measured in the Vostok ice core well (r2=0.80) and we predict prior to Termination V significantly smaller amplitudes in pCO2 variations mainly based on a reduced interglacial ocean circulation and reduced interglacial Southern Ocean sea surface temperature. These predictions for the pre-Vostok period match the new pCO2 data from the EPICA Dome C ice core for the time period 410 to 650 kyr BP equally well (r2=0.79). This is the first forward modelling approach which covers all major processes acting on the global carbon cycle on glacial/interglacial time scales. The contributions of different processes (terrestrial carbon storage, sea ice, sea level, ocean temperature, ocean circulation, CaCO3 chemistry, marine biota) are analysed.

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Tamburini, F., and K. B. Föllmi. "Phosphorus burial in the ocean over glacial-interglacial time scales." Biogeosciences 6, no. 4 (April 2, 2009): 501–13. http://dx.doi.org/10.5194/bg-6-501-2009.

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Abstract. The role of nutrients, such as phosphorus (P), and their impact on primary productivity and the fluctuations in atmospheric CO2 over glacial-interglacial periods are intensely debated. Suggestions as to the importance of P evolved from an earlier proposal that P actively participated in changing productivity rates and therefore climate change, to most recent ones that changes in the glacial ocean inventory of phosphorus were important but not influential if compared to other macronutrients, such as nitrate. Using new data coming from a selection of ODP sites, we analyzed the distribution of oceanic P sedimentary phases and calculate reactive P burial fluxes, and we show how P burial fluxes changed over the last glacial-interglacial period at these sites. Concentrations of reactive P are generally lower during glacial times, while mass accumulation rates (MAR) of reactive P show higher variability. If we extrapolate for the analyzed sites, we may assume that in general glacial burial fluxes of reactive P are lower than those during interglacial periods by about 8%, because the lack of burial of reactive P on the glacial shelf reduced in size, was apparently not compensated by burial in other regions of the ocean. Using the calculated changes in P burial, we evaluate their possible impact on the phosphate inventory in the world oceans. Using a simple mathematical approach, we find that these changes alone could have increased the phosphate inventory of glacial ocean waters by 17–40% compared to interglacial stages. Variations in the distribution of sedimentary P phases at the investigated sites seem to indicate that at the onset of interglacial stages, shallower sites experienced an increase in reactive P concentrations, which seems to point to P-richer waters at glacial terminations. All these findings would support the Shelf-Nutrient Hypothesis, which assumes that during glacial low stands nutrients are transferred from shallow sites to deep sea with possible feedback on the carbon cycle.

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Archer, D. "A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin." Biogeosciences Discussions 11, no. 6 (June 3, 2014): 7853–900. http://dx.doi.org/10.5194/bgd-11-7853-2014.

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Abstract. A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbon (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales, decreasing the efficiency of bubble transit through the water column. The methane cycle on the shelf responds to climate change on a long time constant of thousands of years, because hydrate is excluded thermodynamically from the permafrost zone by water limitation, leaving the hydrate stability zone at least 300 m below the sediment surface.

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Shoenfelt, Elizabeth M., Gisela Winckler, Frank Lamy, Robert F. Anderson, and Benjamin C. Bostick. "Highly bioavailable dust-borne iron delivered to the Southern Ocean during glacial periods." Proceedings of the National Academy of Sciences 115, no. 44 (October 15, 2018): 11180–85. http://dx.doi.org/10.1073/pnas.1809755115.

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Changes in bioavailable dust-borne iron (Fe) supply to the iron-limited Southern Ocean may influence climate by modulating phytoplankton growth and CO2 fixation into organic matter that is exported to the deep ocean. The chemical form (speciation) of Fe impacts its bioavailability, and glacial weathering produces highly labile and bioavailable Fe minerals in modern dust sources. However, the speciation of dust-borne Fe reaching the iron-limited Southern Ocean on glacial−interglacial timescales is unknown, and its impact on the bioavailable iron supply over geologic time has not been quantified. Here we use X-ray absorption spectroscopy on subantarctic South Atlantic and South Pacific marine sediments to reconstruct dust-borne Fe speciation over the last glacial cycle, and determine the impact of glacial activity and glaciogenic dust sources on bioavailable Fe supply. We show that the Fe(II) content, as a percentage of total dust-borne Fe, increases from ∼5 to 10% in interglacial periods to ∼25 to 45% in glacial periods. Consequently, the highly bioavailable Fe(II) flux increases by a factor of ∼15 to 20 in glacial periods compared with the current interglacial, whereas the total Fe flux increases only by a factor of ∼3 to 5. The change in Fe speciation is dominated by primary Fe(II) silicates characteristic of glaciogenic dust. Our results suggest that glacial physical weathering increases the proportion of highly bioavailable Fe(II) in dust that reaches the subantarctic Southern Ocean in glacial periods, which represents a positive feedback between glacial activity and cold glacial temperatures.

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Fischer, H., P. Köhler, J. Schmitt, and F. Fundel. "The Global Carbon Cycle During the Last Glacial/Interglacial Transition." PAGES news 12, no. 2 (October 2004): 29–30. http://dx.doi.org/10.22498/pages.12.2.29.

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SAKAGUCHI, Yutaka, and Shigehiro KATOH. "Paleoclimate in Northern Japan during the Last Interglacial-glacial Cycle." Journal of Geography (Chigaku Zasshi) 102, no. 3 (1993): 288–313. http://dx.doi.org/10.5026/jgeography.102.3_288.

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Brovkin, Victor, Matthias Hofmann, Jørgen Bendtsen, and Andrey Ganopolski. "Ocean biology could control atmospheric δ13C during glacial-interglacial cycle." Geochemistry, Geophysics, Geosystems 3, no. 5 (May 2002): 1–15. http://dx.doi.org/10.1029/2001gc000270.

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Letréguilly, Anne, Niels Reeh, and Philippe Huybrechts. "The Greenland ice sheet through the last glacial-interglacial cycle." Palaeogeography, Palaeoclimatology, Palaeoecology 90, no. 4 (October 1991): 385–94. http://dx.doi.org/10.1016/s0031-0182(12)80037-x.

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38

Løvlie, Reidar. "Palaeomagnetic excursions during the last interglacial/ glacial cycle: A synthesis." Quaternary International 3-4 (January 1989): 5–11. http://dx.doi.org/10.1016/1040-6182(89)90068-2.

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Letréguilly, Anne, Niels Reeh, and Philippe Huybrechts. "The Greenland ice sheet through the last glacial-interglacial cycle." Global and Planetary Change 4, no. 4 (October 1991): 385–94. http://dx.doi.org/10.1016/0921-8181(91)90004-g.

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Guo, Zhengtang, Xin Zhou, and Haibin Wu. "Glacial-interglacial water cycle, global monsoon and atmospheric methane changes." Climate Dynamics 39, no. 5 (July 29, 2011): 1073–92. http://dx.doi.org/10.1007/s00382-011-1147-5.

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41

Berger, A. L. "Astronomical theory of Paleoclimates and the last glacial-interglacial cycle☆." Quaternary Science Reviews 11, no. 5 (1992): 571–81. http://dx.doi.org/10.1016/0277-3791(92)90014-y.

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Pasquier, Virgil, Pierre Sansjofre, Marina Rabineau, Sidonie Revillon, Jennifer Houghton, and David A. Fike. "Pyrite sulfur isotopes reveal glacial−interglacial environmental changes." Proceedings of the National Academy of Sciences 114, no. 23 (May 22, 2017): 5941–45. http://dx.doi.org/10.1073/pnas.1618245114.

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The sulfur biogeochemical cycle plays a key role in regulating Earth’s surface redox through diverse abiotic and biological reactions that have distinctive stable isotopic fractionations. As such, variations in the sulfur isotopic composition (δ34S) of sedimentary sulfate and sulfide phases over Earth history can be used to infer substantive changes to the Earth’s surface environment, including the rise of atmospheric oxygen. Such inferences assume that individual δ34S records reflect temporal changes in the global sulfur cycle; this assumption may be well grounded for sulfate-bearing minerals but is less well established for pyrite-based records. Here, we investigate alternative controls on the sedimentary sulfur isotopic composition of marine pyrite by examining a 300-m drill core of Mediterranean sediments deposited over the past 500,000 y and spanning the last five glacial−interglacial periods. Because this interval is far shorter than the residence time of marine sulfate, any change in the sulfur isotopic record preserved in pyrite (δ34Spyr) necessarily corresponds to local environmental changes. The stratigraphic variations (>76‰) in the isotopic data reported here are among the largest ever observed in pyrite, and are in phase with glacial−interglacial sea level and temperature changes. In this case, the dominant control appears to be glacial−interglacial variations in sedimentation rates. These results suggest that there exist important but previously overlooked depositional controls on sedimentary sulfur isotope records, especially associated with intervals of substantial sea level change. This work provides an important perspective on the origin of variability in such records and suggests meaningful paleoenvironmental information can be derived from pyrite δ34S records.

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Montañez, Isabel P., Jennifer C. McElwain, Christopher J. Poulsen, Joseph D. White, William A. DiMichele, Jonathan P. Wilson, Galen Griggs, and Michael T. Hren. "Climate, pCO2 and terrestrial carbon cycle linkages during late Palaeozoic glacial–interglacial cycles." Nature Geoscience 9, no. 11 (October 24, 2016): 824–28. http://dx.doi.org/10.1038/ngeo2822.

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Broecker, Wallace S., and Tsung-Hung Peng. "Carbon Cycle: 1985 Glacial to Interglacial Changes in the Operation of the Global Carbon Cycle." Radiocarbon 28, no. 2A (1986): 309–27. http://dx.doi.org/10.1017/s0033822200007414.

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The hottest topic for those interested in the earth's carbon cycles is the change in atmospheric CO2 content between glacial and interglacial time. What caused it? What is its role in glacial cycles? We evaluate here the hypotheses that have been put forward to explain the CO2 change with evidence from deep sea sediments. We conclude that all the hypotheses have serious drawbacks and that much effort will have to be expended in gathering more data from ice cores and ocean sediments before we will be pointed toward the correct scenario. Also, thoughtful modeling aimed at depicting the ties between pCO2, O2,13C/12C, 14C/12C, and nutrient constituents in the sea for various modes of circulation will have to be done before the evidence from ocean cores can be properly interpreted.

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Donders, Timme, Konstantinos Panagiotopoulos, Andreas Koutsodendris, Adele Bertini, Anna Maria Mercuri, Alessia Masi, Nathalie Combourieu-Nebout, et al. "1.36 million years of Mediterranean forest refugium dynamics in response to glacial–interglacial cycle strength." Proceedings of the National Academy of Sciences 118, no. 34 (August 16, 2021): e2026111118. http://dx.doi.org/10.1073/pnas.2026111118.

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The sediment record from Lake Ohrid (Southwestern Balkans) represents the longest continuous lake archive in Europe, extending back to 1.36 Ma. We reconstruct the vegetation history based on pollen analysis of the DEEP core to reveal changes in vegetation cover and forest diversity during glacial–interglacial (G–IG) cycles and early basin development. The earliest lake phase saw a significantly different composition rich in relict tree taxa and few herbs. Subsequent establishment of a permanent steppic herb association around 1.2 Ma implies a threshold response to changes in moisture availability and temperature and gradual adjustment of the basin morphology. A change in the character of G–IG cycles during the Early–Middle Pleistocene Transition is reflected in the record by reorganization of the vegetation from obliquity- to eccentricity-paced cycles. Based on a quantitative analysis of tree taxa richness, the first large-scale decline in tree diversity occurred around 0.94 Ma. Subsequent variations in tree richness were largely driven by the amplitude and duration of G–IG cycles. Significant tree richness declines occurred in periods with abundant dry herb associations, pointing to aridity affecting tree population survival. Assessment of long-term legacy effects between global climate and regional vegetation change reveals a significant influence of cool interglacial conditions on subsequent glacial vegetation composition and diversity. This effect is contrary to observations at high latitudes, where glacial intensity is known to control subsequent interglacial vegetation, and the evidence demonstrates that the Lake Ohrid catchment functioned as a refugium for both thermophilous and temperate tree species.

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He, Yuxin, Cheng Zhao, Zhuo Zheng, Zhonghui Liu, Ning Wang, Jie Li, and Rachid Cheddadi. "Peatland evolution and associated environmental changes in central China over the past 40,000 years." Quaternary Research 84, no. 2 (September 2015): 255–61. http://dx.doi.org/10.1016/j.yqres.2015.06.004.

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Central China has experienced stronger summer monsoon during warm periods such as Marine Isotope Stages (MIS) 1 and 3, and weaker summer monsoon during cool periods such as MIS 2. The evolution history of Dajiuhu subalpine peatland in central China can help investigate how the expansion and shrinkage of peatland were associated with monsoonal strength over the last glacial–interglacial cycle. Here we apply bulk organic carbon and molecular biomarkers (hopane and n-alkane) to reconstruct the evolution history for the Dajiuhu peatland over the past 40,000 yr. The results indicate fluctuations between lacustrine and peat-like deposition during MIS 3, steady lacustrine deposition during MIS 2, and peatland initiation and expansion during MIS 1 in the Dajiuhu peatland. Therefore, at the glacial–interglacial scale, warmer summer and cooler winter conditions in interglacial periods are crucial to trigger peat deposition, whereas reduced evaporation in glacial period instead of decreased monsoonal-driven precipitation would have played a predominant role in the regional effective moisture balance. However, within the Holocene (MIS 1), monsoonal precipitation changes appear to be the main controller on millennial-scale variations of water-table level of the Dajiuhu peatland.

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Rodbell, D. T., R. G. Hatfield, M. B. Abbott, C. Y. Chen, A. Woods, J. S. Stoner, D. McGee, et al. "700,000 years of tropical Andean glaciation." Nature 607, no. 7918 (July 13, 2022): 301–6. http://dx.doi.org/10.1038/s41586-022-04873-0.

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AbstractOur understanding of the climatic teleconnections that drove ice-age cycles has been limited by a paucity of well-dated tropical records of glaciation that span several glacial–interglacial intervals. Glacial deposits offer discrete snapshots of glacier extent but cannot provide the continuous records required for detailed interhemispheric comparisons. By contrast, lakes located within glaciated catchments can provide continuous archives of upstream glacial activity, but few such records extend beyond the last glacial cycle. Here a piston core from Lake Junín in the uppermost Amazon basin provides the first, to our knowledge, continuous, independently dated archive of tropical glaciation spanning 700,000 years. We find that tropical glaciers tracked changes in global ice volume and followed a clear approximately 100,000-year periodicity. An enhancement in the extent of tropical Andean glaciers relative to global ice volume occurred between 200,000 and 400,000 years ago, during sustained intervals of regionally elevated hydrologic balance that modified the regular approximately 23,000-year pacing of monsoon-driven precipitation. Millennial-scale variations in the extent of tropical Andean glaciers during the last glacial cycle were driven by variations in regional monsoon strength that were linked to temperature perturbations in Greenland ice cores1; these interhemispheric connections may have existed during previous glacial cycles.

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Liu, Yuming, Xingxing Liu, Long Ma, Shugang Kang, Xiaoke Qiang, Fei Guo, and Youbin Sun. "Temporal–spatial variations in aeolian flux on the Chinese Loess Plateau during the last 150 ka." Geological Magazine 157, no. 5 (November 14, 2019): 757–67. http://dx.doi.org/10.1017/s0016756819001067.

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AbstractAeolian dust deposits from continent and ocean have been extensively investigated to reflect past changes in source aridity and atmospheric circulations. Aeolian flux (AF) as a quantitative dust proxy has been widely used in both palaeoenvironmental reconstruction and numerical simulation. However, available AF data on the Chinese Loess Plateau (CLP) is too limited to assess the temporal–spatial variations at glacial–interglacial timescales, and therefore cannot be used as robust input parameters in palaeoclimate models. Here we investigate eight loess profiles along two N–S-aligned transects on the CLP to quantitatively estimate the AF variations over the last glacial–interglacial cycle. We first establish a refined chronological framework based on optically stimulated luminescence chronology and pedostratigraphic correlation. AF was then estimated by multiplying the sedimentation rate and bulk density. The results show that the AF increases from 2–18 g cm−2 ka−1 in the southeastern CLP to 14–105 g cm−2 ka−1 in the northwestern CLP. At glacial–interglacial scales, the AF varies from 2–20 g cm−2 ka−1 during the last interglacial to 8–105 g cm−2 ka−1 in the last glaciation. Due to more spatial coverage and better age constraints, our AF data can be used to refine other AF datasets and to improve the proxy–model comparison.

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Heinze, Christoph, Babette A. A. Hoogakker, and Arne Winguth. "Ocean carbon cycling during the past 130 000 years – a pilot study on inverse palaeoclimate record modelling." Climate of the Past 12, no. 10 (October 12, 2016): 1949–78. http://dx.doi.org/10.5194/cp-12-1949-2016.

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Abstract. What role did changes in marine carbon cycle processes and calcareous organisms play in glacial–interglacial variation in atmospheric pCO2? In order to answer this question, we explore results from an ocean biogeochemical general circulation model. We attempt to systematically reconcile model results with time-dependent sediment core data from the observations. For this purpose, we fit simulated sensitivities of oceanic tracer concentrations to changes in governing carbon cycle parameters to measured sediment core data. We assume that the time variation in the governing carbon cycle parameters follows the general pattern of the glacial–interglacial deuterium anomaly. Our analysis provides an independent estimate of a maximum mean sea surface temperature drawdown of about 5 °C and a maximum outgassing of the land biosphere by about 430 Pg C at the Last Glacial Maximum as compared to pre-industrial times. The overall fit of modelled palaeoclimate tracers to observations, however, remains quite weak, indicating the potential of more detailed modelling studies to fully exploit the information stored in the palaeoclimatic archive. This study confirms the hypothesis that a decline in ocean temperature and a more efficient biological carbon pump in combination with changes in ocean circulation are the key factors for explaining the glacial CO2 drawdown. The analysis suggests that potential changes in the export rain ratio POC : CaCO3 may not have a substantial imprint on the palaeoclimatic archive. The use of the last glacial as an inverted analogue to potential ocean acidification impacts thus may be quite limited. A strong decrease in CaCO3 export production could potentially contribute to the glacial CO2 decline in the atmosphere, but this remains hypothetical.

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Blattmann, Thomas M. "Ideas and perspectives: Emerging contours of a dynamic exogenous kerogen cycle." Biogeosciences 19, no. 2 (January 24, 2022): 359–73. http://dx.doi.org/10.5194/bg-19-359-2022.

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Abstract. Growing evidence points to the dynamic role that kerogen is playing on Earth's surface in controlling atmospheric chemistry over geologic time. Although quantitative constraints on the weathering of kerogen remain loose, its changing weathering behavior modulated by the activity of glaciers suggests that this largest pool of reduced carbon on Earth may have played a key part in atmospheric CO2 variability across recent glacial–interglacial cycles and beyond. This work enunciates the possibility of kerogen oxidation as a major driver of atmospheric CO2 increase in the wake of glacial episodes. This hypothesis of centennial- and millennial-timescale relevance for this chemical weathering pathway is substantiated by several lines of independent evidence synthesized in this contribution, including the timing of atmospheric CO2 increase, atmospheric CO2 isotope composition (13C and 14C), kerogen oxidation kinetics, observations of kerogen reburial, and modeling results. The author hypothesizes that the deglaciation of kerogen-rich lithologies in western Canada contributed to the characteristic deglacial increase in atmospheric CO2, which reached an inflection point ≤ 300 years after the Laurentide Ice Sheet retreated into the kerogen-poor Canadian Shield. To reconcile the release of isotopically light carbon via kerogen oxidation with Earth surface carbon pool constraints, major oceanic degassing and biospheric regrowth must have acted in concert across glacial–interglacial transitions. Additionally, a process such as a strong shift in the ratio of C3 to C4-derived organic matter must be invoked to maintain isotope mass balance, a point key for reconciling the hypothesis with the carbon isotope record of marine dissolved inorganic carbon. In order to test this hypothesis, quantitative constraints on the contribution of kerogen oxidation to CO2 rise at glacial terminations are needed through systematic studies on (1) CO2 fluxes emanating from the weathering of different lithologies, (2) oxidation kinetics of kerogen along glacial chronosequences, and (3) high-resolution temporal changes in the aerial extent of glacially exposed lithological units and glacial flour.

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Journal articles on the topic 'Glacial-Interglacial cycle'

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