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Cluett, Allison A., and Elizabeth K. Thomas. "Summer warmth of the past six interglacials on Greenland." Proceedings of the National Academy of Sciences 118, no. 20 (May 10, 2021): e2022916118. http://dx.doi.org/10.1073/pnas.2022916118.
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The relative warmth of mid-to-late Pleistocene interglacials on Greenland has remained unknown, leading to debates about the regional climate forcing that caused past retreat of the Greenland Ice Sheet (GrIS). We analyze the hydrogen isotopic composition of terrestrial biomarkers in Labrador Sea sediments through interglacials of the past 600,000 y to infer millennial-scale summer warmth on southern Greenland. Here, we reconstruct exceptionally warm summers in Marine Isotope Stage (MIS) 5e, concurrent with strong Northern Hemisphere summer insolation. In contrast, “superinterglacial” MIS11 demonstrated only moderate warmth, sustained throughout a prolonged interval of elevated atmospheric carbon dioxide. Strong inferred GrIS retreat during MIS11 relative to MIS5e suggests an indirect relationship between maximum summer temperature and cumulative interglacial mass loss, indicating strong GrIS sensitivity to duration of regional warmth and elevated atmospheric carbon dioxide.
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Bridgland, David. "The Climate of Past Interglacials." Quaternary Science Reviews 29, no. 15-16 (July 2010): 1952–53. http://dx.doi.org/10.1016/j.quascirev.2010.04.008.
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Coletti, A. J., R. M. DeConto, J. Brigham-Grette, and M. Melles. "A GCM comparison of Pleistocene super-interglacial periods in relation to Lake El'gygytgyn, NE Arctic Russia." Climate of the Past 11, no. 7 (July 10, 2015): 979–89. http://dx.doi.org/10.5194/cp-11-979-2015.
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Abstract. Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stages (MISs) 1 (9 ka), 5e (127 ka), 11c (409 ka) and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the mean temperature of the warmest month (MTWM) indicate conditions up to 0.4, 2.1, 0.5 and 3.1 °C warmer than today during MIS 1, 5e, 11c and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer (JJA) orbital forcing, the extraordinary warmth of MIS 11c compared to the other interglacials in the Lake El'gygytgyn temperature proxy reconstructions remains difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice and circum-Arctic land ice feedbacks on the modeled climate of the Beringian interior. Simulations accounting for climate–vegetation–land-surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on northeast Asian temperature during the warmth of stages 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic Ocean does have some effect on Lake El'gygytgyn's regional climate, but the exceptional warmth of MIS l1c remains enigmatic compared to the modest orbital and greenhouse gas forcing during that interglacial.
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Schreve, Danielle. "All is flux: the predictive power of fluctuating Quaternary mammalian faunal-climate scenarios." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1788 (November 4, 2019): 20190213. http://dx.doi.org/10.1098/rstb.2019.0213.
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The long-term impact of Middle and Late Pleistocene glacial-interglacial change led to the major reorganization of mammalian faunal communities in northern Europe through species origination, extinction, evolutionary change and distributional shifts. A Bray–Curtis cluster analysis with single linkage to examine relative faunal similarity was performed on mammalian assemblages from five successively older interglacials (MIS 1, 5e, 7c-a, 9 and 11) in Britain, a region with an exceptionally well-resolved faunal record for this time period. The results indicate a degree of continuity in terms of common interglacial elements occurring across all periods but also reveal that the particular climatic and environmental parameters of each interglacial resulted in the generation of very different faunal assemblages, depending on the length, intensity and structure of the interglacial. Of particular note are the comparability of the mammalian assemblages from warm interglacials MIS 5e and 9, and the high species diversity seen in MIS 7c-a, linked to relatively cool temperate conditions and the spread of dry grasslands. Together, these results offer insight into the overall ‘predictability' of Quaternary mammalian interglacial community composition and what might be expected in the natural evolution of a Holocene interglacial freed of anthropogenic interference. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’
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McManus, Jerry, D. Raynaud, and PC Tzedakis. "The 3rd PAGES Past Interglacials workshop." PAGES news 19, no. 2 (July 2011): 80–81. http://dx.doi.org/10.22498/pages.19.2.80.
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Tzedakis, Polychronis C., JF McManus, D. Raynaud, DA Hodell, LC Skinner, and EW Wolff. "The 4th PAGES past interglacials workshop." PAGES news 21, no. 1 (March 2013): 42. http://dx.doi.org/10.22498/pages.21.1.42.
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Jiang, Zhiyi, Chris Brierley, David Thornalley, and Sophie Sax. "No changes in overall AMOC strength in interglacial PMIP4 time slices." Climate of the Past 19, no. 1 (January 12, 2023): 107–21. http://dx.doi.org/10.5194/cp-19-107-2023.
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Abstract. The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism of poleward heat transport and an important part of the global climate system. How it responded to past changes in forcing, such as those experienced during Quaternary interglacials, is an intriguing and open question. Previous modelling studies suggest an enhanced AMOC in the mid-Holocene compared to the preindustrial period. In earlier simulations from the Palaeoclimate Modelling Intercomparison Project (PMIP), this arose from feedbacks between sea ice and AMOC changes, which were dependent on resolution. Here we present an initial analysis of recently available PMIP4 simulations for three experiments representing different interglacial conditions – one 127 000 years ago within the Last Interglacial (127 ka, called lig127k), one in the middle of the Holocene (midHolocene, 6 ka), and a preindustrial control simulation (piControl, 1850 CE). Both lig127k and midHolocene have altered orbital configurations compared to piControl. The ensemble mean of the PMIP4 models shows the strength of the AMOC does not markedly change between the midHolocene and piControl experiments or between the lig127k and piControl experiments. Therefore, it appears orbital forcing itself does not alter the overall AMOC. We further investigate the coherency of the forced response in AMOC across the two interglacials, along with the strength of the signal, using eight PMIP4 models which performed both interglacial experiments. Only two models show a stronger change with the stronger forcing, but those models disagree on the direction of the change. We propose that the strong signals in these two models are caused by a combination of forcing and the internal variability. After investigating the AMOC changes in the interglacials, we further explored the impact of AMOC on the climate system, especially on the changes in the simulated surface temperature and precipitation. After identifying the AMOC's fingerprint on the surface temperature and rainfall, we demonstrate that only a small percentage of the simulated surface climate changes could be attributed to the AMOC. Proxy records of sedimentary Pa/Th ratio during the two interglacial periods both show a similar AMOC strength compared to the preindustrial, which fits nicely with the simulated results. Although the overall AMOC strength shows minimal changes, future work is required to explore whether this occurs through compensating variations in the different components of AMOC (such as Iceland–Scotland overflow water). This line of evidence cautions against interpreting reconstructions of past interglacial climate as being driven by AMOC, outside of abrupt events.
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Galaasen, Eirik Vinje, Ulysses S. Ninnemann, Augustin Kessler, Nil Irvalı, Yair Rosenthal, Jerry Tjiputra, Nathaëlle Bouttes, Didier M. Roche, Helga (Kikki) F. Kleiven, and David A. Hodell. "Interglacial instability of North Atlantic Deep Water ventilation." Science 367, no. 6485 (March 26, 2020): 1485–89. http://dx.doi.org/10.1126/science.aay6381.
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Disrupting North Atlantic Deep Water (NADW) ventilation is a key concern in climate projections. We use (sub)centennially resolved bottom water δ13C records that span the interglacials of the last 0.5 million years to assess the frequency of and the climatic backgrounds capable of triggering large NADW reductions. Episodes of reduced NADW in the deep Atlantic, similar in magnitude to glacial events, have been relatively common and occasionally long-lasting features of interglacials. NADW reductions were triggered across the range of recent interglacial climate backgrounds, which demonstrates that catastrophic freshwater outburst floods were not a prerequisite for large perturbations. Our results argue that large NADW disruptions are more easily achieved than previously appreciated and that they occurred in past climate conditions similar to those we may soon face.
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Tzedakis, Chronis, D. Raynaud, and JF McManus. "The 2nd PAGES past interglacials (PIGS) workshop." PAGES news 18, no. 1 (April 2010): 38–39. http://dx.doi.org/10.22498/pages.18.1.38.
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Coletti, A. J., R. M. DeConto, J. Brigham-Grette, and M. Melles. "A GCM comparison of Plio–Pleistocene interglacial–glacial periods in relation to Lake El'gygytgyn, NE Arctic Russia." Climate of the Past Discussions 10, no. 4 (August 7, 2014): 3127–61. http://dx.doi.org/10.5194/cpd-10-3127-2014.
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Abstract. Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stage (MIS) 1 (9 ka), 5e (127 ka), 11c (409 ka), and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the Mean Temperature of the Warmest Month (MTWM) indicate conditions 2.1, 0.5 and 3.1 °C warmer than today during MIS 5e, 11c, and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer orbital forcing, the extraordinary warmth of MIS 11c relative to the other interglacials in the proxy records remain difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice, and circum-Arctic land ice feedbacks on the climate of the Beringian interior. Simulations accounting for climate-vegetation-land surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on Northeast Asian temperature during the warmth of stage 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic ocean has some effect on Beringian climate, suggesting intrahemispheric coupling seen in comparisons between Lake El'gygytgyn and Antarctic sediment records might be related to linkages between Antarctic ice volume and ocean circulation. The exceptional warmth of MIS 11c remains enigmatic however, relative to the modest orbital and greenhouse gas forcing during that interglacial. Large Northern Hemisphere ice sheets during Plio-Pleistocene glaciation causes a substantial decrease in Mean Temperature of the Coldest Month (MTCM) and Mean Annual Precipitation (PANN) causing significant Arctic aridification. Aridification and cooling can be linked to a combination of mechanical forcing from the Laurentide and Fennoscandian ice sheets on mid-tropospheric westerly flow and expanded sea ice cover causing albedo-enhanced feedback.
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Lacey, J. H., M. J. Leng, A. Francke, H. J. Sloane, A. Milodowski, H. Vogel, H. Baumgarten, and B. Wagner. "Mediterranean climate since the Middle Pleistocene: a 640 ka stable isotope record from Lake Ohrid (Albania/Macedonia)." Biogeosciences Discussions 12, no. 16 (August 20, 2015): 13427–81. http://dx.doi.org/10.5194/bgd-12-13427-2015.
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Abstract. Lake Ohrid (Macedonia/Albania) is an ancient lake with a unique biodiversity and a site of global significance for investigating the influence of climate, geological and tectonic events on the generation of endemic populations. Here, we present oxygen (δ18O) and carbon (δ13C) isotope data on carbonate from the upper ca. 248 m of sediment cores recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project, covering the past 640 ka. Previous studies on short cores from the lake (up to 15 m, < 140 ka) have indicated the Total Inorganic Carbon (TIC) content of sediments to be highly sensitive to climate change over the last glacial–interglacial cycle, comprising abundant endogenic calcite through interglacials and being almost absent in glacials, apart from discrete bands of early diagenetic authigenic siderite. Isotope measurements on endogenic calcite (δ18Oc and δ13Cc) reveal variations both between and within interglacials that suggest the lake has been subject to hydroclimate fluctuations on orbital and millennial timescales. We also measured isotopes on authigenic siderite (δ18Os and δ13Cs) and, with the δ18OCc and δ18Os, reconstruct δ18O of lakewater (δ18Olw) through the 640 ka. Overall, glacials have lower δ18Olw when compared to interglacials, most likely due to cooler summer temperatures, a higher proportion of winter precipitation (snowfall), and a reduced inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability through Marine Isotope Stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial, and was isotopically freshest during MIS 9. After MIS 9, the variability between glacial and interglacial δ18Olw is enhanced and the lake became increasingly evaporated through to present day with MIS 5 having the highest average δ18Olw. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within the lake.
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Tzedakis, P. C. "The MIS 11 – MIS 1 analogy, southern European vegetation, atmospheric methane and the "early anthropogenic hypothesis"." Climate of the Past 6, no. 2 (March 17, 2010): 131–44. http://dx.doi.org/10.5194/cp-6-131-2010.
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Abstract. Marine Isotope Stage (MIS) 11 has been considered a potential analogue for the Holocene and its future evolution. However, a dichotomy has emerged over the precise chronological alignment of the two intervals, with one solution favouring a synchronization of the precession signal and another of the obliquity signal. The two schemes lead to different implications over the natural length of the current interglacial and the underlying causes of the evolution of greenhouse gas concentrations. Here, the close coupling observed between changes in southern European tree populations and atmospheric methane concentrations in previous interglacials is used to evaluate the natural vs. anthropogenic contribution to Holocene methane emissions and assess the two alignment schemes. Comparison of the vegetation trends in MIS 1 and MIS 11 favours a precessional alignment, which would suggest that the Holocene is nearing the end of its natural course. This, combined with the divergence between methane concentrations and temperate tree populations after 5 kyr BP, provides some support for the notion that the Holocene methane trend may be anomalous compared to previous interglacials. In contrast, comparison of MIS 1 with MIS 19, which may represent a closer astronomical analogue than MIS 11, leads to substantially different conclusions on the projected natural duration of the current interglacial and the extent of the anthropogenic contribution to the Holocene methane budget. As answers vary with the choice of analogue, resolution of these issues using past interglacials remains elusive.
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McFarlin, Jamie M., Yarrow Axford, Magdalena R. Osburn, Meredith A. Kelly, Erich C. Osterberg, and Lauren B. Farnsworth. "Pronounced summer warming in northwest Greenland during the Holocene and Last Interglacial." Proceedings of the National Academy of Sciences 115, no. 25 (June 4, 2018): 6357–62. http://dx.doi.org/10.1073/pnas.1720420115.
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Projections of future rates of mass loss from the Greenland Ice Sheet are highly uncertain because its sensitivity to warming is unclear. Geologic reconstructions of Quaternary interglacials can illustrate how the ice sheet responded during past warm periods, providing insights into ice sheet behavior and important tests for data-model comparisons. However, paleoclimate records from Greenland are limited: Early Holocene peak warmth has been quantified at only a few sites, and terrestrial sedimentary records of prior interglacials are exceptionally rare due to glacial erosion during the last glacial period. Here, we discuss findings from a lacustrine archive that records both the Holocene and the Last Interglacial (LIG) from Greenland, allowing for direct comparison between two interglacials. Sedimentary chironomid assemblages indicate peak July temperatures 4.0 to 7.0 °C warmer than modern during the Early Holocene maximum in summer insolation. Chaoborus and chironomids in LIG sediments indicate July temperatures at least 5.5 to 8.5 °C warmer than modern. These estimates indicate pronounced warming in northwest Greenland during both interglacials. This helps explain dramatic ice sheet thinning at Camp Century in northwest Greenland during the Early Holocene and, for the LIG, aligns with controversial estimates of Eemian warming from ice core data retrieved in northern Greenland. Converging geologic evidence for strong LIG warming is challenging to reconcile with inferred Greenland Ice Sheet extent during the LIG, and the two appear incompatible in many models of ice sheet evolution. An increase in LIG snowfall could help resolve this problem, pointing to the need for hydroclimate reconstructions from the region.
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An, Z. S., J. J. Cao, K. K. Anderson, H. Kawahata, and R. Arimoto. "Biogeochemical records of past global iron connections." Climate of the Past Discussions 2, no. 3 (June 8, 2006): 233–65. http://dx.doi.org/10.5194/cpd-2-233-2006.
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Abstract. Paleorecords of dust deposition can be used to evaluate global iron connections under conditions different from those today. Dust production and deposition has co-varied with ocean paleoproductivity, pCO2, and climate over glacial-interglacial cycles, and in this paper we review the current understanding and highlight research needs with respect to paleorecords of global iron connections. These records, which include data from terrestrial (loess) deposits, marine sediments, and ice cores, suggest that average eolian deposition rates were approximately 2–20 times higher during glacial periods than during interglacials. Enhanced dust fluxes to the oceans during glacial times, particularly to the main high-nutrient/low-chlorophyll (HNLC) areas of the open ocean (i.e., the Pacific subarctic, the equatorial Pacific, and the Southern Ocean), may have "fertilized" marine biota, thereby enhancing ocean productivity (1–2 fold) and driving atmospheric CO2 lower. Current models yield variable results, however, with glacial-interglacial changes in dust fluxes changing atmospheric pCO2 by the equivalent of 5 to >50% of the total glacial-interglacial change of 80–100 ppm. Positive correlations among Asian dust, ocean productivity and atmospheric CO2 in last 130 kyr, 1200 yr and 50 yr indicate that eolian iron has played an important role in global biogeochemical cycles of the past. A simple calculation suggests that one-tenth to one-third of the global change in CO2 due to dust-supplied Fe could be ascribed to variations in the dust supply flux from Asia and its associated effects on productivity in the Pacific Ocean.
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Tzedakis, P. C. "The MIS 11 – MIS 1 analogy, southern European vegetation, atmospheric methane and the "early anthropogenic hypothesis"." Climate of the Past Discussions 5, no. 3 (May 13, 2009): 1337–65. http://dx.doi.org/10.5194/cpd-5-1337-2009.
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Abstract. Marine Isotope Stage (MIS) 11 has been considered a potential analogue for the Holocene and its future evolution. However, a dichotomy has emerged over the precise chronological alignment of the two intervals, with one solution favouring a synchronization of the precession signal and another of the obliquity signal. The two schemes lead to different implications over the natural length of the current interglacial and the underlying causes of the evolution of greenhouse gas concentrations. Here the strong coherence observed between changes in temperate tree populations in southern Europe and atmospheric methane concentrations is used to evaluate the two alignment schemes. Comparison of the vegetation trends in MIS 1 and MIS 11 favours a precessional alignment, which would suggest that the Holocene is nearing the end of its natural course. It also provides some support for the notion that the Holocene methane trend may be anomalous compared to previous interglacials. In contrast, comparison of MIS 1 with MIS 19, which may represent a closer astronomical analogue than MIS 11, leads to substantially different conclusions on the projected natural duration of the current interglacial and the extent of the anthropogenic contribution to the Holocene methane budget. As answers vary with the choice of analogue, resolution of these issues using past interglacials remains elusive.
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Schreve, Danielle, and Ian Candy. "Interglacial climates: Advances in our understanding of warm climate episodes." Progress in Physical Geography: Earth and Environment 34, no. 6 (December 2010): 845–56. http://dx.doi.org/10.1177/0309133310386869.
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The Quaternary is characterized by the alternation of relatively brief periods of temperate climate (interglacials) with episodes of extreme cold, often with the build-up of extensive continental ice sheets. Over the last decade, new research has revealed far greater complexity and diversity in the interglacial record than previously recognized, with temperate-climate episodes of markedly different duration, stability and intensity. These findings not only shed light on the climatic parameters behind changing floras and faunas during the Pleistocene but also aid our understanding of climatic evolution during the Holocene (the current interglacial), in particular the search for the most appropriate past analogues. In this progress report, we review the basis for interglacial complexity, drawing upon the evidence from long continuous terrestrial records in the Mediterranean, Antarctic ice cores and river terrace sequences in western Europe, before using the details of the British Quaternary interglacial record as an example of how marine and terrestrial records can be linked.
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Wolff, Eric, and Renato Spahni. "Methane and nitrous oxide in the ice core record." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1856 (May 18, 2007): 1775–92. http://dx.doi.org/10.1098/rsta.2007.2044.
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Polar ice cores contain, in trapped air bubbles, an archive of the concentrations of stable atmospheric gases. Of the major non-CO 2 greenhouse gases, methane is measured quite routinely, while nitrous oxide is more challenging, with some artefacts occurring in the ice and so far limited interpretation. In the recent past, the ice cores provide the only direct measure of the changes that have occurred during the industrial period; they show that the current concentration of methane in the atmosphere is far outside the range experienced in the last 650 000 years; nitrous oxide is also elevated above its natural levels. There is controversy about whether changes in the pre-industrial Holocene are natural or anthropogenic in origin. Changes in wetland emissions are generally cited as the main cause of the large glacial–interglacial change in methane. However, changing sinks must also be considered, and the impact of possible newly described sources evaluated. Recent isotopic data appear to finally rule out any major impact of clathrate releases on methane at these time-scales. Any explanation must take into account that, at the rapid Dansgaard–Oeschger warmings of the last glacial period, methane rose by around half its glacial–interglacial range in only a few decades. The recent EPICA Dome C (Antarctica) record shows that methane tracked climate over the last 650 000 years, with lower methane concentrations in glacials than interglacials, and lower concentrations in cooler interglacials than in warmer ones. Nitrous oxide also shows Dansgaard–Oeschger and glacial–interglacial periodicity, but the pattern is less clear.
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Lacey, Jack H., Melanie J. Leng, Alexander Francke, Hilary J. Sloane, Antoni Milodowski, Hendrik Vogel, Henrike Baumgarten, Giovanni Zanchetta, and Bernd Wagner. "Northern Mediterranean climate since the Middle Pleistocene: a 637 ka stable isotope record from Lake Ohrid (Albania/Macedonia)." Biogeosciences 13, no. 6 (March 24, 2016): 1801–20. http://dx.doi.org/10.5194/bg-13-1801-2016.
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Abstract. Lake Ohrid (Macedonia/Albania) is an ancient lake with unique biodiversity and a site of global significance for investigating the influence of climate, geological, and tectonic events on the generation of endemic populations. Here, we present oxygen (δ18O) and carbon (δ13C) isotope data from carbonate over the upper 243 m of a composite core profile recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. The investigated sediment succession covers the past ca. 637 ka. Previous studies on short cores from the lake (up to 15 m, < 140 ka) have indicated the total inorganic carbon (TIC) content of sediments to be highly sensitive to climate change over the last glacial–interglacial cycle. Sediments corresponding to warmer periods contain abundant endogenic calcite; however, an overall low TIC content in glacial sediments is punctuated by discrete bands of early diagenetic authigenic siderite. Isotope measurements on endogenic calcite (δ18Oc and δ13Cc) reveal variations both between and within interglacials that suggest the lake has been subject to palaeoenvironmental change on orbital and millennial timescales. We also measured isotope ratios from authigenic siderite (δ18Os and δ13Cs) and, with the oxygen isotope composition of calcite and siderite, reconstruct δ18O of lake water (δ18Olw) over the last 637 ka. Interglacials have higher δ18Olw values when compared to glacial periods most likely due to changes in evaporation, summer temperature, the proportion of winter precipitation (snowfall), and inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability from marine isotope stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial. Climate conditions became progressively wetter during MIS 11 and MIS 9. Interglacial periods after MIS 9 are characterised by increasingly evaporated and drier conditions through MIS 7, MIS 5, and the Holocene. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within Lake Ohrid.
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Hahn, Annette, Enno Schefuß, Jeroen Groeneveld, Charlotte Miller, and Matthias Zabel. "Glacial to interglacial climate variability in the southeastern African subtropics (25–20° S)." Climate of the Past 17, no. 1 (January 29, 2021): 345–60. http://dx.doi.org/10.5194/cp-17-345-2021.
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Abstract. We present a continuous and well-resolved record of climatic variability for the past 100 000 years from a marine sediment core taken in Delagoa Bight, off southeastern Africa. In addition to providing a sea surface temperature reconstruction for the past ca. 100 000 years, this record also allows a high-resolution continental climatic reconstruction. Climate sensitive organic proxies, like the distribution and isotopic composition of plant-wax lipids as well as elemental indicators of fluvial input and weathering type provide information on climatic changes in the adjacent catchment areas (Incomati, Matola and Lusutfu rivers). At the transition between glacials and interglacials, shifts in vegetation correlate with changes in sea surface temperature in the Agulhas Current. The local hydrology, however, does not follow these orbitally paced shifts. Instead, precipitation patterns follow millennial-scale variations with different forcing mechanisms in glacial vs. interglacial climatic states. During glacials, southward displacement of the Intertropical Convergence Zone facilitates a transmission of northern hemispheric signals (e.g., Heinrich events) to the southern hemispheric subtropics. Furthermore, the southern hemispheric westerlies become a more direct source of precipitation as they shift northward over the study site, especially during Antarctic cold phases. During interglacials, the observed short-term hydrological variability is also a function of Antarctic climate variability; however, it is driven by the indirect influence of the southern hemispheric westerlies and the associated South African high-pressure cell blocking the South Indian Ocean Convergence Zone related precipitation. As a consequence of the interplay of these effects, small-scale climatic zones exist. We propose a conceptual model describing latitudinal shifts of these zones along the southeastern African coast as tropical and temperate climate systems shift over glacial and interglacial cycles. The proposed model explains some of the apparent contradictions between several paleoclimate records in the region.
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Frechen, Manfred. "Timing and vegetation history of past interglacials in northern Eurasia." Quaternary International 241, no. 1-2 (August 2011): 1–2. http://dx.doi.org/10.1016/j.quaint.2011.04.033.
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Rodrigues, Teresa. "Sea surface Temperature similarities during the Present and Past Interglacials." Quaternary International 279-280 (November 2012): 409–10. http://dx.doi.org/10.1016/j.quaint.2012.08.1307.
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Ridgwell, A. "Application of sediment core modelling to understanding climates of the past: An example from glacial-interglacial changes in Southern Ocean silica cycling." Climate of the Past Discussions 2, no. 6 (December 20, 2006): 1371–86. http://dx.doi.org/10.5194/cpd-2-1371-2006.
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Abstract. Paleoceanographic evidence from the Southern Ocean reveals an apparent stark meridional divide in biogeochemical dynamics associated with the glacial-interglacial cycles of the late Neogene. South of the present-day position of the Antarctic Polar Front biogenic opal is generally much more abundant in sediments during interglacials compared to glacials. To the north, an anti-phased relationship is observed, with maximum opal abundance instead occurring during glacials. This antagonistic response of sedimentary properties is an important model validation target for testing hypotheses of glacial-interglacial change, particularly with respect to understanding the causes of the variability in atmospheric CO2. Here, I illustrate a time-dependent modelling approach to helping understand past climatic change by means of the generation of synthetic sediment core records. I find a close match between model-predicted and observed down-core changes in sedimentary opal content is achieved when changes in seasonal sea-ice extent is imposed, suggesting that the cryosphere is probably the primary driver of the striking features exhibited by the paleoceanographic record of this region.
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Biller-Celander, Nicole, Jeremy D. Shakun, David McGee, Corinne I. Wong, Alberto V. Reyes, Ben Hardt, Irit Tal, Derek C. Ford, and Bernard Lauriol. "Increasing Pleistocene permafrost persistence and carbon cycle conundrums inferred from Canadian speleothems." Science Advances 7, no. 18 (April 2021): eabe5799. http://dx.doi.org/10.1126/sciadv.abe5799.
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Permafrost carbon represents a potentially powerful amplifier of climate change, but little is known about permafrost sensitivity and associated carbon cycling during past warm intervals. We reconstruct permafrost history in western Canada during Pleistocene interglacials from 130 uranium-thorium ages on 72 speleothems, cave deposits that only accumulate with deep ground thaw. We infer that permafrost thaw extended to the high Arctic during one or more periods between ~1.5 million and 0.5 million years ago but has been limited to the sub-Arctic since 400,000 years ago. Our Canadian speleothem growth history closely parallels an analogous reconstruction from Siberia, suggesting that this shift toward more stable permafrost across the Pleistocene may have been Arctic-wide. In contrast, interglacial greenhouse gas concentrations were relatively stable throughout the Pleistocene, suggesting that either permafrost thaw did not trigger substantial carbon release to the atmosphere or it was offset by carbon uptake elsewhere on glacial-interglacial time scales.
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Just, J., N. Nowaczyk, A. Francke, L. Sagnotti, and B. Wagner. "Climatic control on the occurrence of high-coercivity magnetic minerals and preservation of greigite in a 640 ka sediment sequence from Lake Ohrid (Balkans)." Biogeosciences Discussions 12, no. 16 (August 28, 2015): 14215–43. http://dx.doi.org/10.5194/bgd-12-14215-2015.
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Abstract. The bulk magnetic mineral record from Lake Ohrid, spanning the past ca. 640 ka, shows a strong relationship to environmental conditions on glacial–interglacial and millennial time scales. During extremely cold glacials, a lower accumulation of organic matter and likely enhanced mixing of the water-column coincides with the presence of greigite, whereas greigite is absent in sediments deposited during less severe glacials. Those "non-greigite" glacial sediments are characterized by high concentration of high-coercivity magnetic minerals, which relates to enhanced erosion of soils that had formed during the preceding interglacials. In contrast, magnetite dominated magnetic mineral assemblages characterize interglacial deposits and most likely originate from detrital particles of physically weathered rocks. Superimposed on the glacial–interglacial behavior are millennial scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Likewise to the process on glacial–interglacial time-scales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both, environmental conditions on land and intra-lacustrine processes.
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Thompson, William G., MB Andersen, A. Dutton, and M. Siddall. "Understanding future sea level rise: The challenges of dating past interglacials." PAGES news 18, no. 1 (April 2010): 39–40. http://dx.doi.org/10.22498/pages.18.1.39.
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Burn, C. R. "Permafrost, tectonics, and past and future regional climate change, Yukon and adjacent Northwest Territories." Canadian Journal of Earth Sciences 31, no. 1 (January 1, 1994): 182–91. http://dx.doi.org/10.1139/e94-015.
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Late Tertiary changes in the general circulation of the atmosphere, regionally enhanced by uplift of the Wrangell – Saint: Elias and Coast mountains, were sufficient to promote permafrost development in the western Arctic. Permafrost developed in Yukon Territory and adjacent Northwest Territories during early Pleistocene glacial periods, after continued tectonic activity led to further modification of regional climate, but degraded in the interglacials. Permafrost has been present in northern parts of the region since the Illinoian glaciation, but most ground ice in central Yukon formed in the Late Wisconsinan. The present interglacial is the only one with widespread evidence of permafrost, which is maintained in the valleys of central and southern Yukon by the Saint Elias Mountains blocking continental penetration of maritime air from the Gulf of Alaska. This reduces snow depth in winter, while cold-air drainage in the dissected terrain of the Yukon Plateaus enhances the near-surface inversion, leading to continental minimum temperatures. General circulation models used to simulate climate represent the physiography of northwest Canada crudely. As a result, the simulations are unable to reproduce conditions responsible for the development and preservation of permafrost in the region.
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Masson-Delmotte, V., D. Buiron, A. Ekaykin, M. Frezzotti, H. Gallée, J. Jouzel, G. Krinner, et al. "A comparison of the present and last interglacial periods in six Antarctic ice cores." Climate of the Past 7, no. 2 (April 28, 2011): 397–423. http://dx.doi.org/10.5194/cp-7-397-2011.
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Abstract. We compare the present and last interglacial periods as recorded in Antarctic water stable isotope records now available at various temporal resolutions from six East Antarctic ice cores: Vostok, Taylor Dome, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML), Dome Fuji and the recent TALDICE ice core from Talos Dome. We first review the different modern site characteristics in terms of ice flow, meteorological conditions, precipitation intermittency and moisture origin, as depicted by meteorological data, atmospheric reanalyses and Lagrangian moisture source diagnostics. These different factors can indeed alter the relationships between temperature and water stable isotopes. Using five records with sufficient resolution on the EDC3 age scale, common features are quantified through principal component analyses. Consistent with instrumental records and atmospheric model results, the ice core data depict rather coherent and homogenous patterns in East Antarctica during the last two interglacials. Across the East Antarctic plateau, regional differences, with respect to the common East Antarctic signal, appear to have similar patterns during the current and last interglacials. We identify two abrupt shifts in isotopic records during the glacial inception at TALDICE and EDML, likely caused by regional sea ice expansion. These regional differences are discussed in terms of moisture origin and in terms of past changes in local elevation histories, which are compared to ice sheet model results. Our results suggest that elevation changes may contribute significantly to inter-site differences. These elevation changes may be underestimated by current ice sheet models.
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Masson-Delmotte, V., D. Buiron, A. Ekaykin, M. Frezzotti, H. Gallée, J. Jouzel, G. Krinner, et al. "A comparison of the present and last interglacial periods in six Antarctic ice cores." Climate of the Past Discussions 6, no. 5 (October 26, 2010): 2267–333. http://dx.doi.org/10.5194/cpd-6-2267-2010.
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Abstract. We compare the present and last interglacial periods as recorded in Antarctic water stable isotope records now available at various temporal resolutions from six East Antarctic ice cores: Vostok, Taylor Dome, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML), Dome Fuji and the recent TALDICE ice core from Talos Dome. We first review the different modern site characteristics in terms of ice flow, meteorological conditions, precipitation intermittency and moisture origin, as depicted by meteorological data, atmospheric reanalyses and Lagrangian moisture source diagnostics. These different factors can indeed alter the relationships between temperature and water stable isotopes. Using five records with sufficient resolution on the EDC3 age scale, common features are quantified through principal component analyses. Consistent with instrumental records and atmospheric model results, the ice core data depict rather coherent and homogenous patterns in East Antarctica during the last two interglacials. Across the East Antarctic plateau, regional differences, with respect to the common East Antarctic signal, appear to have similar patterns during the current and last interglacials. We identify two abrupt shifts in isotopic records during glacial inception at TALDICE and EDML, likely caused by regional sea ice expansion. These regional differences are discussed in terms of moisture origin and in terms of past changes in local elevation histories which are compared to ice sheet model results. Our results suggest that, for coastal sites, elevation changes may contribute significantly to inter-site differences. These elevation changes may be underestimated by current ice sheet models.
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Just, Janna, Norbert R. Nowaczyk, Leonardo Sagnotti, Alexander Francke, Hendrik Vogel, Jack H. Lacey, and Bernd Wagner. "Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans)." Biogeosciences 13, no. 7 (April 8, 2016): 2093–109. http://dx.doi.org/10.5194/bg-13-2093-2016.
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Abstract. The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial–interglacial and millennial timescales. A shift in the formation of early diagenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before ∼ 320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe / Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high- to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial–interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial–interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes.
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Lambert, F., M. Bigler, J. P. Steffensen, M. Hutterli, and H. Fischer. "The calcium-dust relationship in high-resolution data from Dome C, Antarctica." Climate of the Past Discussions 7, no. 2 (April 4, 2011): 1113–37. http://dx.doi.org/10.5194/cpd-7-1113-2011.
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Abstract. Ice core data from Antarctica provide detailed insights into the characteristics of past climate, atmospheric circulation, as well as changes in the aerosol load of the atmosphere. We present high-resolution records of soluble calcium (Ca2+), non-sea-salt soluble calcium (nssCa2+), and insoluble mineral aerosol dust from the East Antarctic Plateau at a depth resolution of 1 cm, spanning the past 800 000 yr. The comparison shows that the ratio of ionic proxies such as CaCa2+ (or nssCa2+) to particulate dust aerosol is variable in time. Accordingly, the insoluble dust record is representative of large and small atmospheric particulate dust load changes and better suited to quantify the aerosol effect on the radiation balance in the past. In contrast soluble dust proxies such as Ca2+ and nssCa2+ will underestimate this effect but may be better suited to quantify the deposition of chemically active Ca2+ or other soluble dust derived nutrients into the Southern Ocean. The correlation between nssCa2+ and particulate dust is time dependent with high correlations during glacial and low correlation during interglacial times. The low correlation during warm times may be partly caused by changes in the soluble calcium content of dust particles, possibly due to a more acidic atmosphere during interglacials. The ratio of nssCa2+ to dust is dependent on the dust concentration itself. A simple mixing of two dust end members for glacial and interglacial conditions with nssCa2+ to dust ratios of 0.045 and approximately 0.3, respectively, can explain the overall temporal change in the nssCa2+ to dust ratio over time.
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Pan, Linda, Evelyn M. Powell, Konstantin Latychev, Jerry X. Mitrovica, Jessica R. Creveling, Natalya Gomez, Mark J. Hoggard, and Peter U. Clark. "Rapid postglacial rebound amplifies global sea level rise following West Antarctic Ice Sheet collapse." Science Advances 7, no. 18 (April 2021): eabf7787. http://dx.doi.org/10.1126/sciadv.abf7787.
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Geodetic, seismic, and geological evidence indicates that West Antarctica is underlain by low-viscosity shallow mantle. Thus, as marine-based sectors of the West Antarctic Ice Sheet (WAIS) retreated during past interglacials, or will retreat in the future, exposed bedrock will rebound rapidly and flux meltwater out into the open ocean. Previous studies have suggested that this contribution to global mean sea level (GMSL) rise is small and occurs slowly. We challenge this notion using sea level predictions that incorporate both the outflux mechanism and complex three-dimensional viscoelastic mantle structure. In the case of the last interglacial, where the GMSL contribution from WAIS collapse is often cited as ~3 to 4 meters, the outflux mechanism contributes ~1 meter of additional GMSL change within ~1 thousand years of the collapse. Using a projection of future WAIS collapse, we also demonstrate that the outflux can substantially amplify GMSL rise estimates over the next century.
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Lovejoy, Shaun, and Fabrice Lambert. "Spiky fluctuations and scaling in high-resolution EPICA ice core dust fluxes." Climate of the Past 15, no. 6 (December 17, 2019): 1999–2017. http://dx.doi.org/10.5194/cp-15-1999-2019.
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Abstract. Atmospheric variability as a function of scale has been divided in various dynamical regimes with alternating increasing and decreasing fluctuations: weather, macroweather, climate, macroclimate, and megaclimate. Although a vast amount of data are available at small scales, the larger picture is not well constrained due to the scarcity and low resolution of long paleoclimatic time series. Using statistical techniques originally developed for the study of turbulence, we analyse the fluctuations of a centimetric-resolution dust flux time series from the EPICA Dome C ice core in Antarctica that spans the past 800 000 years. The temporal resolution ranges from annual at the top of the core to 25 years at the bottom, enabling the detailed statistical analysis and comparison of eight glaciation cycles and the subdivision of each cycle into eight consecutive phases. The unique span and resolution of the dataset allows us to analyse the macroweather and climate scales in detail. We find that the interglacial and glacial maximum phases of each cycle showed particularly large macroweather to climate transition scale τc (around 2 kyr), whereas mid-glacial phases feature centennial transition scales (average of 300 years). This suggests that interglacials and glacial maxima are exceptionally stable when compared with the rest of a glacial cycle. The Holocene (with τc≈7.9 kyr) had a particularly large τc, but it was not an outlier when compared with the phases 1 and 2 of other cycles. We hypothesize that dust variability at larger (climate) scales appears to be predominantly driven by slow changes in glaciers and vegetation cover, whereas at small (macroweather) scales atmospheric processes and changes in the hydrological cycles are the main drivers. For each phase, we quantified the drift, intermittency, amplitude, and extremeness of the variability. Phases close to the interglacials (1, 2, 8) show low drift, moderate intermittency, and strong extremes, while the “glacial” middle phases 3–7 display strong drift, weak intermittency, and weaker extremes. In other words, our results suggest that glacial maxima, interglacials, and glacial inceptions were characterized by relatively stable atmospheric conditions but punctuated by frequent and severe droughts, whereas the mid-glacial climate was inherently more unstable.
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Menviel, Laurie, Emilie Capron, Aline Govin, Andrea Dutton, Lev Tarasov, Ayako Abe-Ouchi, Russell N. Drysdale, et al. "The penultimate deglaciation: protocol for Paleoclimate Modelling Intercomparison Project (PMIP) phase 4 transient numerical simulations between 140 and 127 ka, version 1.0." Geoscientific Model Development 12, no. 8 (August 22, 2019): 3649–85. http://dx.doi.org/10.5194/gmd-12-3649-2019.
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Abstract. The penultimate deglaciation (PDG, ∼138–128 thousand years before present, hereafter ka) is the transition from the penultimate glacial maximum (PGM) to the Last Interglacial (LIG, ∼129–116 ka). The LIG stands out as one of the warmest interglacials of the last 800 000 years (hereafter kyr), with high-latitude temperature warmer than today and global sea level likely higher by at least 6 m. Considering the transient nature of the Earth system, the LIG climate and ice-sheet evolution were certainly influenced by the changes occurring during the penultimate deglaciation. It is thus important to investigate, with coupled atmosphere–ocean general circulation models (AOGCMs), the climate and environmental response to the large changes in boundary conditions (i.e. orbital configuration, atmospheric greenhouse gas concentrations, ice-sheet geometry and associated meltwater fluxes) occurring during the penultimate deglaciation. A deglaciation working group has recently been set up as part of the Paleoclimate Modelling Intercomparison Project (PMIP) phase 4, with a protocol to perform transient simulations of the last deglaciation (19–11 ka; although the protocol covers 26–0 ka). Similar to the last deglaciation, the disintegration of continental ice sheets during the penultimate deglaciation led to significant changes in the oceanic circulation during Heinrich Stadial 11 (∼136–129 ka). However, the two deglaciations bear significant differences in magnitude and temporal evolution of climate and environmental changes. Here, as part of the Past Global Changes (PAGES)-PMIP working group on Quaternary interglacials (QUIGS), we propose a protocol to perform transient simulations of the penultimate deglaciation under the auspices of PMIP4. This design includes time-varying changes in orbital forcing, greenhouse gas concentrations, continental ice sheets as well as freshwater input from the disintegration of continental ice sheets. This experiment is designed for AOGCMs to assess the coupled response of the climate system to all forcings. Additional sensitivity experiments are proposed to evaluate the response to each forcing. Finally, a selection of paleo-records representing different parts of the climate system is presented, providing an appropriate benchmark for upcoming model–data comparisons across the penultimate deglaciation.
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Axford, Y., J. P. Briner, D. R. Francis, G. H. Miller, I. R. Walker, and A. P. Wolfe. "Chironomids record terrestrial temperature changes throughout Arctic interglacials of the past 200,000 yr." Geological Society of America Bulletin 123, no. 7-8 (January 28, 2011): 1275–87. http://dx.doi.org/10.1130/b30329.1.
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Dixit, Yama, Samuel Toucanne, Christophe Fontanier, Virgil Pasquier, Juan M. Lora, Gwenael Jouet, and Aradhna Tripati. "Enhanced western mediterranean rainfall during past interglacials driven by North Atlantic pressure changes." Quaternary International 553 (July 2020): 1–13. http://dx.doi.org/10.1016/j.quaint.2020.08.017.
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Bauch, Henning. "Variations in the Polar-Directed Oceanic Heat During Past Interglacials: Causes and Consequences." Quaternary International 279-280 (November 2012): 42–43. http://dx.doi.org/10.1016/j.quaint.2012.07.185.
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Ridgwell, A. "Application of sediment core modelling to interpreting the glacial-interglacial record of Southern Ocean silica cycling." Climate of the Past 3, no. 3 (July 10, 2007): 387–96. http://dx.doi.org/10.5194/cp-3-387-2007.
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Abstract. Sediments from the Southern Ocean reveal a meridional divide in biogeochemical cycling response to the glacial-interglacial cycles of the late Neogene. South of the present-day position of the Antarctic Polar Front in the Atlantic sector of the Southern Ocean, biogenic opal is generally much more abundant in sediments during interglacials compared to glacials. To the north, an anti-phased relationship is observed, with maximum opal abundance instead occurring during glacials. This antagonistic response of sedimentary properties provides an important model validation target for testing hypotheses of glacial-interglacial change against, particularly for understanding the causes of the concurrent variability in atmospheric CO2. Here, I illustrate a time-dependent modelling approach to helping understand climates of the past by means of the mechanistic simulation of marine sediment core records. I find that a close match between model-predicted and observed down-core changes in sedimentary opal content can be achieved when changes in seasonal sea-ice extent are imposed, whereas the predicted sedimentary response to iron fertilization on its own is not consistent with sedimentary observations. The results of this sediment record model-data comparison supports previous inferences that the changing cryosphere is the primary driver of the striking features exhibited by the paleoceanographic record of this region.
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Dupont, L. M., T. Caley, J. H. Kim, I. Castañeda, B. Malaizé, and J. Giraudeau. "Glacial-interglacial vegetation dynamics in South Eastern Africa coupled to sea surface temperature variations in the Western Indian Ocean." Climate of the Past 7, no. 4 (November 9, 2011): 1209–24. http://dx.doi.org/10.5194/cp-7-1209-2011.
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Abstract. Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ∼120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka.
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Li, Qianyu, Fan Zheng, Muhong Chen, Rong Xiang, Peijun Qiao, Lei Shao, and Xinrong Cheng. "Glacial Paleoceanography off the Mouth of the Mekong River, Southern South China Sea, During the last 500 ka." Quaternary Research 73, no. 3 (May 2010): 563–72. http://dx.doi.org/10.1016/j.yqres.2010.03.003.
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We have analyzed core MD01-2392, ∽360 km east of the Mekong River mouth in the South China Sea (SCS). Over the past 500 ka, planktonic foraminiferal oxygen-isotopic values are consistently lighter than northern SCS and open-ocean records by up to 0.5‰, indicating the influence of run-off from the Mekong River during both glacial and interglacial periods. Carbonate content is higher during interglacials; sedimentation rates were higher during glacials. Increased sedimentation rates since 30 ka imply increased run-off during the last glacial maximum and Holocene Period. Contrary to general experience, in which it is classed as a warm species for temperature estimates, the thermocline-dwelling species Pulleniatina obliquiloculata increased its numbers during glacial periods. This implies an estuarine circulation and even brackish-water caps during glacial periods, reinforcing the sense of strong run-off. In an overall decline of warm water, the thermocline shoaled stepwise, with rapid rises across the glacial terminations. We infer that the southern SCS was opened to an influx of Indian Ocean waters through southern passages at those times of rising sea levels.
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Stewart, John R., Adrian M. Lister, Ian Barnes, and Love Dalén. "Refugia revisited: individualistic responses of species in space and time." Proceedings of the Royal Society B: Biological Sciences 277, no. 1682 (October 28, 2009): 661–71. http://dx.doi.org/10.1098/rspb.2009.1272.
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Climate change in the past has led to significant changes in species' distributions. However, how individual species respond to climate change depends largely on their adaptations and environmental tolerances. In the Quaternary, temperate-adapted taxa are in general confined to refugia during glacials while cold-adapted taxa are in refugia during interglacials. In the Northern Hemisphere, evidence appears to be mounting that in addition to traditional southern refugia for temperate species, cryptic refugia existed in the North during glacials. Equivalent cryptic southern refugia, to the south of the more conventional high-latitude polar refugia, exist in montane areas during periods of warm climate, such as the current interglacial. There is also a continental/oceanic longitudinal gradient, which should be included in a more complete consideration of the interaction between species ranges and climates. Overall, it seems clear that there is large variation in both the size of refugia and the duration during which species are confined to them. This has implications for the role of refugia in the evolution of species and their genetic diversity.
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Thibodeau, Benoit, Henning A. Bauch, and Thomas F. Pedersen. "Stratification-induced variations in nutrient utilization in the Polar North Atlantic during past interglacials." Earth and Planetary Science Letters 457 (January 2017): 127–35. http://dx.doi.org/10.1016/j.epsl.2016.09.060.
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Riethdorf, J. R., D. Nürnberg, L. Max, R. Tiedemann, S. A. Gorbarenko, and M. I. Malakhov. "Millennial-scale variability of marine productivity and terrigenous matter supply in the western Bering Sea over the past 180 kyr." Climate of the Past 9, no. 3 (June 26, 2013): 1345–73. http://dx.doi.org/10.5194/cp-9-1345-2013.
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Abstract. We used piston cores recovered in the western Bering Sea to reconstruct millennial-scale changes in marine productivity and terrigenous matter supply over the past ~180 kyr. Based on a geochemical multi-proxy approach, our results indicate closely interacting processes controlling marine productivity and terrigenous matter supply comparable to the situation in the Okhotsk Sea. Overall, terrigenous inputs were high, whereas export production was low. Minor increases in marine productivity occurred during intervals of Marine Isotope Stage 5 and interstadials, but pronounced maxima were recorded during interglacials and Termination I. The terrigenous material is suggested to be derived from continental sources on the eastern Bering Sea shelf and to be subsequently transported via sea ice, which is likely to drive changes in surface productivity, terrigenous inputs, and upper-ocean stratification. From our results we propose glacial, deglacial, and interglacial scenarios for environmental change in the Bering Sea. These changes seem to be primarily controlled by insolation and sea-level forcing which affect the strength of atmospheric pressure systems and sea-ice growth. The opening history of the Bering Strait is considered to have had an additional impact. High-resolution core logging data (color b*, XRF scans) strongly correspond to the Dansgaard–Oeschger climate variability registered in the NGRIP ice core and support an atmospheric coupling mechanism of Northern Hemisphere climates.
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Riethdorf, J. R., D. Nürnberg, L. Max, R. Tiedemann, S. A. Gorbarenko, and M. I. Malakhov. "Millennial-scale variability of marine productivity and terrigenous matter supply in the western Bering Sea over the past 180 kyr." Climate of the Past Discussions 8, no. 6 (December 12, 2012): 6135–98. http://dx.doi.org/10.5194/cpd-8-6135-2012.
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Abstract. We used piston cores recovered in the western Bering Sea to reconstruct millennial-scale changes in marine productivity and terrigenous matter supply over the past ~180 kyr. Based on a geochemical multi-proxy approach our results indicate closely interacting processes controlling marine productivity and terrigenous matter supply comparable to the situation in the Okhotsk Sea. Overall, terrigenous inputs were high, whereas primary production was low. Minor increases in marine productivity occurred during warm intervals of stage 5 and interstadials, but pronounced maxima were recorded during interglacials and Termination I. Seasonal sea-ice is suggested to act as the dominant transport agent for terrigenous material. From our results we propose glacial, deglacial, and interglacial scenarios for environmental change in the Bering Sea. These changes seem to be primarily controlled by insolation and sea-level forcing which affect the strength of atmospheric pressure systems and sea-ice growth. The opening history of the Bering Strait and the Aleutian passes is considered to have had an additional impact. Sea-ice dynamics are thought to drive changes in surface productivity, terrigenous inputs, and upper-ocean stratification. High-resolution core logging data (color b*, XRF scans) strongly correspond to the Dansgaard–Oeschger climate variability registered in the NGRIP ice core and support an atmospheric coupling mechanism of Northern Hemisphere climates.
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Smart, C. C. "Some Observations on Subglacial Ground-Water flow." Journal of Glaciology 32, no. 111 (1986): 232–34. http://dx.doi.org/10.1017/s0022143000015550.
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AbstractConduit and regelation water are inferred to drain as ground water from up to 130 km2of Columbia Icefield. Subglacial conduits appear to be generally occupied by free surface streams. Ground-water flow will allow exchange between the regelation film and conduits. Present-day discharge from beneath the accumulation zone carries little sediment, and past injections of sediment appear to correspond to ancient interglacials. Transport of sediment through cave passages may be analogous to transport through basal conduits.
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Smart, C. C. "Some Observations on Subglacial Ground-Water flow." Journal of Glaciology 32, no. 111 (1986): 232–34. http://dx.doi.org/10.3189/s0022143000015550.
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AbstractConduit and regelation water are inferred to drain as ground water from up to 130 km2 of Columbia Icefield. Subglacial conduits appear to be generally occupied by free surface streams. Ground-water flow will allow exchange between the regelation film and conduits. Present-day discharge from beneath the accumulation zone carries little sediment, and past injections of sediment appear to correspond to ancient interglacials. Transport of sediment through cave passages may be analogous to transport through basal conduits.
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Dupont, L. M., T. Caley, J. H. Kim, I. Castaneda, B. Malaizé, and J. Giraudeau. "Glacial-interglacial vegetation dynamics in south eastern Africa depend on sea surface temperature variations in the west Indian Ocean." Climate of the Past Discussions 7, no. 4 (July 6, 2011): 2261–96. http://dx.doi.org/10.5194/cpd-7-2261-2011.
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Abstract. Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between Indian and Atlantic Ocean. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ~120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (down till 342 ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including elements with affinity to the Cape Flora) for the last glacial as well as for other glacial periods of the past 300 ka.
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Waldmann, Nicolas, Adi Torfstein, and Mordechai Stein. "Northward intrusions of low- and mid-latitude storms across the Saharo-Arabian belt during past interglacials." Geology 38, no. 6 (June 2010): 567–70. http://dx.doi.org/10.1130/g30654.1.
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Irvalı, Nil, Eirik V. Galaasen, Ulysses S. Ninnemann, Yair Rosenthal, Andreas Born, and Helga (Kikki) F. Kleiven. "A low climate threshold for south Greenland Ice Sheet demise during the Late Pleistocene." Proceedings of the National Academy of Sciences 117, no. 1 (December 23, 2019): 190–95. http://dx.doi.org/10.1073/pnas.1911902116.
Full textAbstract:
The Greenland Ice Sheet (GIS) has been losing mass at an accelerating rate over the recent decades. Models suggest a possible temperature threshold between 0.8 and 3.2 °C, beyond which GIS decline becomes irreversible. The duration of warmth above a given threshold is also a critical determinant for GIS survival, underlining the role of ocean warming, as its inertia prolongs warmth and triggers longer-term feedbacks. The exact point at which these feedbacks are triggered remains equivocal. Late Pleistocene interglacials provide potential case examples for constraining the past response of the GIS to a range of climate states, including conditions warmer than present. However, little is known about the magnitude and duration of warming near Greenland during these periods. Using high-resolution multiproxy surface ocean climate records off southern Greenland, we show that the previous 4 interglacials over the last ∼450 ka all reached warmer than present climate conditions and exceeded the modeled temperature threshold for GIS collapse but by different magnitudes and durations. Complete deglaciation of the southern GIS in Marine Isotope Stage 11c (MIS 11c; 394.7 to 424.2 ka) occurred under climates only slightly warmer than present (∼0.5 ± 1.6 °C), placing the temperature threshold for major GIS retreat in the lower end of model estimates and within projections for this century.
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Crump, Sarah E., Bianca Fréchette, Matthew Power, Sam Cutler, Gregory de Wet, Martha K. Raynolds, Jonathan H. Raberg, et al. "Ancient plant DNA reveals High Arctic greening during the Last Interglacial." Proceedings of the National Academy of Sciences 118, no. 13 (March 15, 2021): e2019069118. http://dx.doi.org/10.1073/pnas.2019069118.
Full textAbstract:
Summer warming is driving a greening trend across the Arctic, with the potential for large-scale amplification of climate change due to vegetation-related feedbacks [Pearson et al., Nat. Clim. Chang. (3), 673–677 (2013)]. Because observational records are sparse and temporally limited, past episodes of Arctic warming can help elucidate the magnitude of vegetation response to temperature change. The Last Interglacial ([LIG], 129,000 to 116,000 y ago) was the most recent episode of Arctic warming on par with predicted 21st century temperature change [Otto-Bliesner et al., Philos. Trans. A Math. Phys. Eng. Sci. (371), 20130097 (2013) and Post et al., Sci. Adv. (5), eaaw9883 (2019)]. However, high-latitude terrestrial records from this period are rare, so LIG vegetation distributions are incompletely known. Pollen-based vegetation reconstructions can be biased by long-distance pollen transport, further obscuring the paleoenvironmental record. Here, we present a LIG vegetation record based on ancient DNA in lake sediment and compare it with fossil pollen. Comprehensive plant community reconstructions through the last and current interglacial (the Holocene) on Baffin Island, Arctic Canada, reveal coherent climate-driven community shifts across both interglacials. Peak LIG warmth featured a ∼400-km northward range shift of dwarf birch, a key woody shrub that is again expanding northward. Greening of the High Arctic—documented here by multiple proxies—likely represented a strong positive feedback on high-latitude LIG warming. Authenticated ancient DNA from this lake sediment also extends the useful preservation window for the technique and highlights the utility of combining traditional and molecular approaches for gleaning paleoenvironmental insights to better anticipate a warmer future.
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Bock, Michael, Jochen Schmitt, Jonas Beck, Barbara Seth, Jérôme Chappellaz, and Hubertus Fischer. "Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4ice core records." Proceedings of the National Academy of Sciences 114, no. 29 (July 3, 2017): E5778—E5786. http://dx.doi.org/10.1073/pnas.1613883114.
Full textAbstract:
Atmospheric methane (CH4) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [δ13CH4and δD(CH4)] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our δD(CH4) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH4changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial.