Journal articles on the topic 'Neoglaciation'
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1
Wiles, Gregory C., and Parker E. Calkin. "Neoglaciation in the Southern Kenai Mountains, Alaska." Annals of Glaciology 14 (1990): 319–22. http://dx.doi.org/10.3189/s0260305500008831.
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A preliminary late-Holocene glacial chronology from the west flank of the southern Kenai Mountains, Alaska, is characterized by two major episodes of advance. Outlet glaciers of both the Harding Icefield and the Grewingk-Yalik ice complex were expanding across their present positions at 545 A.D. and again during the Little Ice Age, about 1500 A.D. The earliest of these Neoglacial advances is dated by radiocarbon ages from the outer rings of tree trunks rooted near the margins of Grewingk and Dinglestadt glaciers. Subsequently, ice margins retreated some distance behind their present positions allowing marked soil development before the last readvance through mature forest. Wood preserved in lateral moraines at Grewingk Glacier and from an uprooted stump at Tustemena Glacier date this later ice advance. Tree-ring ages, correlated with lichen diameters, suggest that this last advance was widespread and culminated in its Neoglacial maximum about 1800 A.D.. Since this time, glacier retreat has dominated in the area, punctuated by at least two pauses. Historical accounts and photographs document a mean rate of retreat of 27 m a−1 for the past century with partial control exerted by calving of ice margins into proglacial lakes.
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Wiles, Gregory C., and Parker E. Calkin. "Neoglaciation in the Southern Kenai Mountains, Alaska." Annals of Glaciology 14 (1990): 319–22. http://dx.doi.org/10.1017/s0260305500008831.
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A preliminary late-Holocene glacial chronology from the west flank of the southern Kenai Mountains, Alaska, is characterized by two major episodes of advance. Outlet glaciers of both the Harding Icefield and the Grewingk-Yalik ice complex were expanding across their present positions at 545 A.D. and again during the Little Ice Age, about 1500 A.D. The earliest of these Neoglacial advances is dated by radiocarbon ages from the outer rings of tree trunks rooted near the margins of Grewingk and Dinglestadt glaciers. Subsequently, ice margins retreated some distance behind their present positions allowing marked soil development before the last readvance through mature forest. Wood preserved in lateral moraines at Grewingk Glacier and from an uprooted stump at Tustemena Glacier date this later ice advance. Tree-ring ages, correlated with lichen diameters, suggest that this last advance was widespread and culminated in its Neoglacial maximum about 1800 A.D.. Since this time, glacier retreat has dominated in the area, punctuated by at least two pauses. Historical accounts and photographs document a mean rate of retreat of 27 m a−1 for the past century with partial control exerted by calving of ice margins into proglacial lakes.
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Erikstad, Lars, and Johan Ludvig Sollid. "Neoglaciation in South Norway using lichenometric methods." Norsk Geografisk Tidsskrift - Norwegian Journal of Geography 40, no. 2 (January 1986): 85–105. http://dx.doi.org/10.1080/00291958608552159.
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Porter, Stephen C. "Onset of Neoglaciation in the Southern Hemisphere." Journal of Quaternary Science 15, no. 4 (2000): 395–408. http://dx.doi.org/10.1002/1099-1417(200005)15:4<395::aid-jqs535>3.0.co;2-h.
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Briner, Jason P., Lena Håkansson, and Ole Bennike. "The deglaciation and neoglaciation of Upernavik Isstrøm, Greenland." Quaternary Research 80, no. 3 (November 2013): 459–67. http://dx.doi.org/10.1016/j.yqres.2013.09.008.
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We constrain the history of the Greenland Ice Sheet margin during the Holocene at Upernavik Isstrøm, a major ice stream in northwestern Greenland. Radiocarbon-dated sediment sequences from proglacial-threshold lakes adjacent to the present ice margin constrain deglaciation of the sites to older than 9.6 ± 0.1 ka. This age of deglaciation is confirmed with10Be ages of 9.9 ± 0.1 ka from an island adjacent to the historical ice position. The lake sediment sequences also constrain the ice margin to have been less extensive than it is today for the remainder of the Holocene until ~ 1100 to ~ 700 yr ago, when it advanced into two lake catchments. The ice margin retreated back out of these lake catchments in the last decade. The early Holocene deglaciation in Melville Bugt, one of few locations around Greenland where a vast stretch of the current ice margin is marine-based, preceded deglaciation in most other parts of Greenland. Earlier deglaciation in this ice-sheet sector may have been caused by additional ablation mechanisms that apply to marine-based ice margins. Furthermore, despite ice-sheet models depicting this sector of Greenland as relatively stable throughout the Holocene, our data indicate a > 20 km advance-retreat cycle within the last millennium.
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García-Ruiz, José M., David Palacios, Nuria Andrés, and Juan I. López-Moreno. "Neoglaciation in the Spanish Pyrenees: a multiproxy challenge." Mediterranean Geoscience Reviews 2, no. 1 (April 2020): 21–36. http://dx.doi.org/10.1007/s42990-020-00022-9.
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Baroni, Carlo, and Giuseppe Orombelli. "The Alpine “Iceman” and Holocene Climatic Change." Quaternary Research 46, no. 1 (July 1996): 78–83. http://dx.doi.org/10.1006/qres.1996.0046.
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The finding of a prehistoric mummified corpse at the upper edge of the accumulation area of an alpine glacier, together with its unique set of artifacts, provided new information on glacier dimensions during the little-known phases of major glacier shrinkage that characterized the warmest parts of the Holocene. The sudden burial of the corpse in a permanent snow cover occurred 5300–5050 cal yr B.P., indicating a significant climatic change that induced glacier expansion at the beginning of Neoglaciation. New geomorphologic data and two AMS 14C ages from buried soils suggest that the present glacier size, following over 100 yr of shrinkage, is comparable to that immediately preceding Neoglaciation. Therefore, we can deduce that the current global climatic warming may have interrupted the environmental conditions prevailing in the Alps during Neoglacial time, restoring characteristics similar to those prevailing during the climatic optimum that were never achieved during the second half of the Holocene.
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Seltzer, Geoffrey O., and Donald T. Rodbell. "Delta progradation and Neoglaciation, Laguna Parón, Cordillera Blanca, Peru." Journal of Quaternary Science 20, no. 7-8 (2005): 715–22. http://dx.doi.org/10.1002/jqs.975.
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MATTHEWS, JOHN A. "A comment on ‘Neoglaciation in South Norway using lichenometric methods’." Norsk Geografisk Tidsskrift - Norwegian Journal of Geography 41, no. 1 (March 1987): 61–67. http://dx.doi.org/10.1080/00291958708552172.
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ERIKSTAD, L., and J. L. SOLLID. "Neoglaciation in south Norway using lichenometric methods: a reply to Matthews." Norsk Geografisk Tidsskrift - Norwegian Journal of Geography 42, no. 1 (January 1988): 62. http://dx.doi.org/10.1080/00291958808552184.
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Geirsdóttir, Áslaug, Gifford H. Miller, John T. Andrews, David J. Harning, Leif S. Anderson, Christopher Florian, Darren J. Larsen, and Thor Thordarson. "The onset of neoglaciation in Iceland and the 4.2 ka event." Climate of the Past 15, no. 1 (January 8, 2019): 25–40. http://dx.doi.org/10.5194/cp-15-25-2019.
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Abstract. Strong similarities in Holocene climate reconstructions derived from multiple proxies (BSi, TOC – total organic carbon, δ13C, C∕N, MS – magnetic susceptibility, δ15N) preserved in sediments from both glacial and non-glacial lakes across Iceland indicate a relatively warm early to mid Holocene from 10 to 6 ka, overprinted with cold excursions presumably related to meltwater impact on North Atlantic circulation until 7.9 ka. Sediment in lakes from glacial catchments indicates their catchments were ice-free during this interval. Statistical treatment of the high-resolution multi-proxy paleoclimate lake records shows that despite great variability in catchment characteristics, the sediment records document more or less synchronous abrupt, cold departures as opposed to the smoothly decreasing trend in Northern Hemisphere summer insolation. Although all lake records document a decline in summer temperature through the Holocene consistent with the regular decline in summer insolation, the onset of significant summer cooling occurs ∼5 ka at high-elevation interior sites but is variably later at sites closer to the coast, suggesting that proximity to the sea may modulate the impact from decreasing summer insolation. The timing of glacier inception during the mid Holocene is determined by the descent of the equilibrium line altitude (ELA), which is dominated by the evolution of summer temperature as summer insolation declined as well as changes in sea surface temperature for coastal glacial systems. The glacial response to the ELA decline is also highly dependent on the local topography. The initial ∼5 ka nucleation of Langjökull in the highlands of Iceland defines the onset of neoglaciation in Iceland. Subsequently, a stepwise expansion of both Langjökull and northeast Vatnajökull occurred between 4.5 and 4.0 ka, with a second abrupt expansion ∼3 ka. Due to its coastal setting and lower topographic threshold, the initial appearance of Drangajökull in the NW of Iceland was delayed until ∼2.3 ka. All lake records reflect abrupt summer temperature and catchment disturbance at ∼4.5 ka, statistically indistinguishable from the global 4.2 ka event, and a second widespread abrupt disturbance at 3.0 ka, similar to the stepwise expansion of Langjökull and northeast Vatnajökull. Both are intervals characterized by large explosive volcanism and tephra distribution in Iceland resulting in intensified local soil erosion. The most widespread increase in glacier advance, landscape instability, and soil erosion occurred shortly after 2 ka, likely due to a complex combination of increased impact from volcanic tephra deposition, cooling climate, and increased sea ice off the coast of Iceland. All lake records indicate a strong decline in temperature ∼1.5 ka, which culminated during the Little Ice Age (1250–1850 CE) when the glaciers reached their maximum Holocene dimensions.
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Clague, John J., and Rolf W. Mathewes. "Neoglaciation, Glacier-Dammed Lakes, and Vegetation Change in Northwestern British Columbia, Canada." Arctic and Alpine Research 28, no. 1 (February 1996): 10. http://dx.doi.org/10.2307/1552081.
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Matthews, John A., and Wibjörn Karlén. "Asynchronous neoglaciation and Holocene climatic change reconstructed from Norwegian glaciolacustrine sedimentary sequences." Geology 20, no. 11 (1992): 991. http://dx.doi.org/10.1130/0091-7613(1992)020<0991:anahcc>2.3.co;2.
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SUGUIO, KENITIRO. "Influence of the "Hypsithermal Age" and "Neoglaciation" climatic conditions on the Brazilian coast." Pesquisas em Geociências 28, no. 2 (December 31, 2001): 213. http://dx.doi.org/10.22456/1807-9806.20296.
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Meanwhile the highest relative sea-level is the present one in southeastern United States (Gulf of Mexico) or in Netherlands coast, most of the Brazilian coast exhibited Holocene sea-levels higher than the present in the past. The Brazilian curves, representing the relative sea-level changes during last 7.000 years, are outlined using sedimentological, biological and prehistorical past sea-level records. This paper shows that these relative sea-level records, during the Holocene, can be suitably used to demonstrate the influence of the worldwide known paleoclimatic events, like the “Hypsithermal Age” and “Neoglaciation” on the Brazilian coast.
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Vavrus, Stephen J., Feng He, John E. Kutzbach, and William F. Ruddiman. "Rapid neoglaciation on Ellesmere Island promoted by enhanced summer snowfall in a transient climate model simulation of the middle-late-Holocene." Holocene 30, no. 10 (June 12, 2020): 1474–80. http://dx.doi.org/10.1177/0959683620932967.
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Arctic neoglaciation following the Holocene Thermal Maximum is an important feature of late-Holocene climate. We investigated this phenomenon using a transient 6000-year simulation with the CESM-CAM5 climate model driven by orbital forcing, greenhouse gas concentrations, and a land use reconstruction. During the first three millennia analyzed here (6–3 ka), mean Arctic snow depth increases, despite enhanced greenhouse forcing. Superimposed on this secular trend is a very abrupt increase in snow depth between 5 and 4.9 ka on Ellesmere Island and the Greenland coasts, in rough agreement with the timing of observed neoglaciation in the region. This transition is especially extreme on Ellesmere Island, where end-of-summer snow coverage jumps from nearly 0 to virtually 100% in 1 year, and snow depth increases to the model’s imposed maximum within 15 years. This climatic shift involves more than the Milankovitch-based expectation of cooler summers causing less snow melt. Coincident with the onset of the cold regime are two consecutive summers with heavy snowfall on Ellesmere Island that help to short-circuit the normal seasonal melt cycle. These heavy snow seasons are caused by synoptic-scale, cyclonic circulation anomalies over the Arctic Ocean and Canadian Archipelago, including an extremely positive phase of the Arctic Oscillation. Our study reveals that a climate model can produce sudden climatic transitions in this region prone to glacial inception and exceptional variability, due to a dynamic mechanism (more summer snowfall induced by an extreme circulation anomaly) that augments the traditional Milankovitch thermodynamic explanation of orbitally induced glacier development.
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Wenjing, Zhang. "Identification of glaciers with surge characteristics on the Tibetan Plateau." Annals of Glaciology 16 (1992): 168–72. http://dx.doi.org/10.3189/1992aog16-1-168-172.
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Investigations of Zelunglung and Midui Glaciers in southeast Tibet, China, indicate that they have some characteristics of surge-type glaciers. There have been two extraordinary movements of Zelunglung Glacier, one in 1950 and one in 1968. A collapse of the terminus area took place in 1984. Midui Glacier experienced extraordinary movements about 55 years ago and also in 1988. During these events, the glacier termini reached moraines formed during neoglaciation and the Little Ice Age. The advances of the two glaciers are not related to climate variation. The glaciers caused serious disasters with loss of life and property, and disruption of transportation corridors.
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Wenjing, Zhang. "Identification of glaciers with surge characteristics on the Tibetan Plateau." Annals of Glaciology 16 (1992): 168–72. http://dx.doi.org/10.1017/s0260305500005012.
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Investigations of Zelunglung and Midui Glaciers in southeast Tibet, China, indicate that they have some characteristics of surge-type glaciers. There have been two extraordinary movements of Zelunglung Glacier, one in 1950 and one in 1968. A collapse of the terminus area took place in 1984. Midui Glacier experienced extraordinary movements about 55 years ago and also in 1988. During these events, the glacier termini reached moraines formed during neoglaciation and the Little Ice Age. The advances of the two glaciers are not related to climate variation. The glaciers caused serious disasters with loss of life and property, and disruption of transportation corridors.
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Evans, David J. A., Craig Butcher, and Arjan V. Kirthisingha. "Neoglaciation and an early 'Little Ice Age' in western Norway: lichenometric evidence from the Sandane area." Holocene 4, no. 3 (September 1994): 278–89. http://dx.doi.org/10.1177/095968369400400307.
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Ryder, J. M., and B. Thomson. "Neoglaciation in the southern Coast Mountains of British Columbia: chronology prior to the late Neoglacial maximum." Canadian Journal of Earth Sciences 23, no. 3 (March 1, 1986): 273–87. http://dx.doi.org/10.1139/e86-031.
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Moraine stratigraphy and morphology, radiocarbon dates from Klinaklini, Franklin, Tiedemann, Gilbert, and Bridge glaciers, and related information from elsewhere in the Coast Mountains are used to construct a chronology for glacier fluctuations. The Garibaldi phase of glacier expansion, 6000–5000 14C years BP, at the end of the early Holocene xerothermic interval, is indicated by overridden tree stumps. The mid-Neoglacial Tiedemann advance, 3300–1900 14C years BP, is represented by moraines, till, and meltwater sediments at three glaciers, but only Tiedemann Glacier attained its greatest Holocene extent at this time. Late Neoglacial expansion commenced before 900 14C years BP and continued without notable interruption until glaciers achieved their maximum post-Pleistocene expansion during the eighteenth and nineteenth centuries. Evidence for the Garibaldi and Tiedemann events is scarce within the Coast Mountains because of the more extensive late Neoglacial advance. However, correlative advances have been recognized in adjacent mountains within British Columbia, Washington, and Alaska.
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Badding, Michael E., Jason P. Briner, and Darrell S. Kaufman. "10Be ages of late Pleistocene deglaciation and Neoglaciation in the north-central Brooks Range, Arctic Alaska." Journal of Quaternary Science 28, no. 1 (December 6, 2012): 95–102. http://dx.doi.org/10.1002/jqs.2596.
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Bradley, Raymond S., and Jostein Bakke. "Is there evidence for a 4.2 ka BP event in the northern North Atlantic region?" Climate of the Past 15, no. 5 (September 2, 2019): 1665–76. http://dx.doi.org/10.5194/cp-15-1665-2019.
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Abstract. We review paleoceanographic and paleoclimatic records from the northern North Atlantic to assess the nature of climatic conditions at 4.2 ka BP, which has been identified as a time of exceptional climatic anomalies in many parts of the world. The northern North Atlantic region experienced relatively warm conditions from 6 to 8 ka BP, followed by a general decline in temperatures after ∼5 ka BP, which led to the onset of neoglaciation. Over the last 5000 years, a series of multi-decadal- to century-scale fluctuations occurred, superimposed on an overall decline in temperature. Although a few records do show a glacial advance around 4.2 ka BP, because they are not widespread we interpret them as local events – simply one glacial advance of many that occurred in response to the overall climatic deterioration that characterized the late Holocene.
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Ljungqvist, Fredrik Charpentier. "The Spatio-Temporal Pattern of the Mid-Holocene Thermal Maximum." Geografie 116, no. 2 (2011): 91–110. http://dx.doi.org/10.37040/geografie2011116020091.
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This article presents a review of the spatio-temporal pattern of the mid-Holocene Thermal Maximum as it occurs in 60 different reconstructions of annual mean temperature from locations around the globe. The geographical coherency of multi-centennial periods with annual mean temperatures at least 1°C and 2°C above the pre-industrial (~1750 AD) equivalents are presented. Although the reconstructions show a heterogeneous temperature pattern for the period c. 10–8 ka BP, a rather coherent period of temperatures exceeding the pre-industrial ones are seen for c. 8–4 ka BP. The onset of the Neoglaciation takes place 4–3 ka BP and cumulates during the Little Ice Age (c. 1300–1900 AD). Overall, our review points towards a more homogeneous mid-Holocene Thermal Maximum than hitherto reported. However, the still limited data coverage, especially for the Southern Hemisphere, restricts the possibility to draw any firm conclusion regarding the amplitude and spatio-temporal pattern of the maximum mid- Holocene warming.
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MacDonald, Glen M., Andrei A. Velichko, Constantine V. Kremenetski, Olga K. Borisova, Aleksandra A. Goleva, Andrei A. Andreev, Les C. Cwynar, et al. "Holocene Treeline History and Climate Change Across Northern Eurasia." Quaternary Research 53, no. 3 (May 2000): 302–11. http://dx.doi.org/10.1006/qres.1999.2123.
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AbstractRadiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia). Boreal forest development in this region commenced by 10,000 yr B.P. Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P. Forest establishment and retreat was roughly synchronous across most of northern Russia. Treeline advance on the Kola Peninsula, however, appears to have occurred later than in other regions. During the period of maximum forest extension, the mean July temperatures along the northern coastline of Russia may have been 2.5° to 7.0°C warmer than modern. The development of forest and expansion of treeline likely reflects a number of complimentary environmental conditions, including heightened summer insolation, the demise of Eurasian ice sheets, reduced sea-ice cover, greater continentality with eustatically lower sea level, and extreme Arctic penetration of warm North Atlantic waters. The late Holocene retreat of Eurasian treeline coincides with declining summer insolation, cooling arctic waters, and neoglaciation.
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Herren, Pierre-Alain, Anja Eichler, Horst Machguth, Tatyana Papina, Leonhard Tobler, Alexander Zapf, and Margit Schwikowski. "The onset of Neoglaciation 6000 years ago in western Mongolia revealed by an ice core from the Tsambagarav mountain range." Quaternary Science Reviews 69 (June 2013): 59–68. http://dx.doi.org/10.1016/j.quascirev.2013.02.025.
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LaBelle, Jason M., and Kelton A, Meyer. "Paleoecological and Archaeological Investigation of the ROMO 9 Ice Patch, Rocky Mountain National Park, Colorado, USA." Journal of Glacial Archaeology 5 (August 15, 2021): 51–71. http://dx.doi.org/10.1558/jga.19957.
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Rocky Mountain National Park contains a dense record of prehistoric Native American archaeological locales and biological resources, but questions remain about the past use of the Park’s ice patches by ancient humans and animals. Our survey of 30 locations in the Park revealed that the majority of ice patches are small in size and contain limited evidence of past visitation by mobile peoples, but moderate use by game. In this paper, we present new radiocarbon dates for materials documented in the recently melted forefield of the ROMO 9 ice patch, a mid-sized ice body located in alpine tundra along the Continental Divide. Dated materials include timber-sized pine trees, keratin and bone collagen from large game (bighorn sheep, elk), and a possible wooden artifact made from Mountain mahogany. Results suggest most finds date to several periods of known neoglaciation, during the mid-Holocene (c. 4150 cal BP) and the Little Ice Age (c. 115 cal BP). Our results corroborate past findings on mid-Holocene timberline in the Colorado Front Range, as well as the paucity of archaeological evidence from small ice patches in Colorado.
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Abbott, Mark B., Geoffrey O. Seltzer, Kerry R. Kelts, and John Southon. "Holocene Paleohydrology of the Tropical Andes from Lake Records." Quaternary Research 47, no. 1 (January 1997): 70–80. http://dx.doi.org/10.1006/qres.1996.1874.
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AbstractTwo century-scale time series in northern Bolivia constrain the ages of abrupt changes in the physical, geochemical, and biological characteristics of sediments obtained from lakes that formed during deglaciation from the late Pleistocene glacial maximum. The watersheds of Laguna Viscachani (16°12′S, 68°07′W, 3780 m) and Lago Taypi Chaka Kkota (16°13′S, 68°21′W, 4300 m), located on the eastern and western slopes of the Cordillera Real, respectively, contain small cirque glaciers. A high-resolution chronology of the lake sediments is provided by 23 AMS14C dates of discrete macrofossils. Late Pleistocene glaciers retreated rapidly, exposing the lake basins between 10,700 and 970014C yr B.P. The sedimentary facies suggest that after 890014C yr B.P. glaciers were absent from the watersheds and remained so during the middle Holocene. An increase in the precipitation–evaporation balance is indicated above unconformities dated to ∼230014C yr B.P. in both Lago Taypi Chaka Kkota and Laguna Viscachani. An abrupt increase in sediment accumulation rates after 140014C yr B.P. signals the onset of Neoglaciation. A possible link exists between the observed millennial-scale shifts in the regional precipitation–evaporation balance and seasonal shifts in tropical insolation.
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Savoskul, Oxana S. "Holocene Glacier Advances in the Headwaters of Sredniaya Avacha, Kamchatka, Russia." Quaternary Research 52, no. 1 (July 1999): 14–26. http://dx.doi.org/10.1006/qres.1999.2051.
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Holocene glacial deposits in Sredniya Avacha headwaters are subdivided into three age groups (events A, B, and C) based upon geomorphic features, tephrochronology, and lichenometry. Tephras of Opala volcano (1400–1500 yr B.P.), Ksudach volcano (1700–1800 and 6000 yr B.P.), and Zavaritskiy volcano (2800 yr B.P.) are used as stratigraphic markers. Rhizocarpon geographicum (L.) DC and Rhizocarpon section Alpicola growth curves are established using tephrochronologically dated and historical surfaces. The age of event A (pre-Hypsitermal?) moraines is constrained by an age of 6000 yr B.P. for overlying Ksudach-2 tephra and an age of 7200 (?) lichenometric (L) yr B.P. Event B (Neoglaciation) had a multiple nature, with the most prominent advances at 4300–3500, 3300–2800, 2600–2100, 1800–1400, and 1300–1100 (L) yr B.P.; the culmination occurred before 2800 yr B.P., as suggested by a date for Zavaritskiy volcano tephra found on the glacial and outwash deposits. Less-extensive glacier advances of event C (“Little Ice Age”), occurred at 800–600, 500–200, 180–110, and 90–40 (L) yr B.P. The ELA depression was 200–250, 100–150, 30–70 m during the culmination of events A, B, and C, respectively.
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Davis, P. Thompson, Paul R. Bierman, Kimberly A. Marsella, Marc W. Caffee, and John R. Southon. "Cosmogenic analysis of glacial terrains in the eastern Canadian Arctic: a test for inherited nuclides and the effectiveness of glacial erosion." Annals of Glaciology 28 (1999): 181–88. http://dx.doi.org/10.3189/172756499781821805.
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AbstractTo determine the effectiveness of glacial erosion and the magnitude of cosmogenic nuclide inheritance from prior periods of cosmic-ray exposure, we measured the abundance of 10Be and 26Al in nine samples collected from bedrock, boulders and cobbles exposed by the retreat of Tumbling Glacier, Baffin Island, Canada. Most samples had nuclide concentrations so low that we were only able to set upper limits for nuclide abundance. Three boulders, two on a Neoglacial moraine of Tumbling Glacier that impounds Crater Lake and one on a roche moutonnée within the Neoglacial moraine loop, had nuclide abundances indicating no more than 900 yr of exposure at the surface. Three bedrock samples, striated by Tumbling Glacier and exposed by ice retreat within the last 20 yr, have similarly low nuclide abundances. One bedrock sample, covered by Tumbling Glacier ice for some part of the Holocene but not eroded, allows us to estimate crudely the duration of Neoglaciation at our sample site (about 5450 yr) and to provide a lower limit on the erosion rate of Tumbling Glacier (0.10 ± 0.03 mm a–1). We analyzed two cobbles collected from the tops of roches moutonnées at Crater Lake; one cobble had the equivalent of 3000 yr of exposure, the other < 900 yr.
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Jones, Miriam C., Dorothy M. Peteet, Dorothy Kurdyla, and Thomas Guilderson. "Climate and vegetation history from a 14,000-year peatland record, Kenai Peninsula, Alaska." Quaternary Research 72, no. 2 (September 2009): 207–17. http://dx.doi.org/10.1016/j.yqres.2009.04.002.
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AbstractAnalysis of pollen, spores, macrofossils, and lithology of an AMS 14C-dated core from a subarctic fen on the Kenai Peninsula, Alaska reveals changes in vegetation and climate beginning 14,200 cal yr BP. Betula expansion and contraction of herb tundra vegetation characterize the Younger Dryas on the Kenai, suggesting increased winter snowfall concurrent with cool, sunny summers. Remarkable Polypodiaceae (fern) abundance between 11,500 and 8500 cal yr BP implies a significant change in climate. Enhanced peat preservation and the occurrence of wet meadow species suggest high moisture from 11,500 to 10,700 cal yr BP, in contrast to drier conditions in southeastern Alaska; this pattern may indicate an intensification and repositioning of the Aleutian Low (AL). Drier conditions on the Kenai Peninsula from 10,700 to 8500 cal yr BP may signify a weaker AL, but elevated fern abundance may have been sustained by high seasonality with substantial snowfall and enhanced glacial melt. Decreased insolation-induced seasonality resulted in climatic cooling after 8500 cal yr BP, with increased humidity from 8000 to 5000 cal yr BP. A dry interval punctuated by volcanic activity occurred between 5000 and 3500 cal yr BP, followed by cool, moist climate, coincident with Neoglaciation. Tsuga mertensiana expanded after ~ 1500 cal yr BP in response to the shift to cooler conditions.
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Benes, James V., Virginia Iglesias, and Cathy Whitlock. "Postglacial vegetation dynamics at high elevation from Fairy Lake in the northern Greater Yellowstone Ecosystem, Montana, USA." Quaternary Research 92, no. 2 (April 5, 2019): 365–80. http://dx.doi.org/10.1017/qua.2019.9.
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AbstractThe postglacial vegetation and fire history of the Greater Yellowstone Ecosystem is known from low and middle elevations, but little is known about high elevations. Paleoecologic data from Fairy Lake in the Bridger Range, southwestern Montana, provide a new high-elevation record that spans the last 15,000 yr. The records suggest a period of tundra-steppe vegetation prior to ca. 13,700 cal yr BP was followed by open Picea forest at ca. 11,200 cal yr BP. Pinus-Pseudotsuga parkland was present after ca. 9200 cal yr BP, when conditions were warmer/drier than present. It was replaced by mixed-conifer parkland at ca. 5000 cal yr BP. Present-day subalpine forest established at ca. 2800 cal yr BP. Increased avalanche or mass-wasting activity during the early late-glacial period, the Younger Dryas chronozone, and Neoglaciation suggest cool, wet periods. Sites at different elevations in the region show (1) synchronous vegetation responses to late-glacial warming; (2) widespread xerothermic forests and frequent fires in the early-to-middle Holocene; and (3) a trend to forest closure during late-Holocene cooling. Conditions in the Bridger Range were, however, wetter than other areas during the early Holocene. Across the Northern Rockies, postglacial warming progressed from west to east, reflecting range-specific responses to insolation-driven changes in climate.
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Mahaney, William C., and Volli Kalm. "Middle–late holocene paleoclimate and weathering history in the norra storfjället mountains, sweden: deglacial record and soil stratigraphy applied to neoglaciation in lower latitudes." Geografiska Annaler: Series A, Physical Geography 95, no. 2 (June 2013): 145–58. http://dx.doi.org/10.1111/geoa.12008.
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Clapperton, Chalmers M. "Glacial and volcanic geomorphology of the Chimborazo-Carihuairazo Massif, Ecuadorian Andes." Transactions of the Royal Society of Edinburgh: Earth Sciences 81, no. 2 (1990): 91–116. http://dx.doi.org/10.1017/s0263593300005174.
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ABSTRACTThe Chimborazo (6,310 m)–Carihuairazo (5,102 m) massif is one of the largest ice-capped central volcanic complexes in the northern Andes. Combined evidence from volcanic and glacial landforms and sediments suggests cyclical evolution during the Pleistocene. Effusive eruptions of mixed high-silica andesite (SiO2%wt c. 60) predominated and built the bulk of the edifice. Explosive activity developed as the parental magma evolved to dacite-rhyolite (SiO2%wt 64–74), culminating with cone collapse and large-scale debris avalanching. Post-collapse activity evolved from the production of high-silica andesite to terminate with monogenetic eruptions of basic andesite (SiO2%wt 54–56) from flank fissures. The last eruption occurred before 11,000 yBP.The interstratification of volcanic and glacial deposits shows that glaciers expanded and contracted several times during the later Pleistocene, while the volcanic edifices were evolving. Glaciers expanded to altitudinal limits of 3,400–3,600 m during the early last glaciation and reached similar limits sometime after 33,000 yBP; an intervening interstadial interval lasted for 10,000 y. By 20,000–18,000 yBP, glaciers receded slightly because of decreased precipitation, but later readvances culiminated at 12,000–10,000 yBP and during the last 5,000 y. Glacier reconstruction and estimation of former equilibrium line altitudes suggest that the mean annual temperatures during the full glacial, late-glacial and Neoglaciation intervals were lower than now by c. 5–6°C, 2–3°C and 1°C, respectively, but these may be underestimates because of the assumption that precipitation was constant.
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Magny, Michel, Urs Leuzinger, Sigmar Bortenschlager, and Jean Nicolas Haas. "Tripartite climate reversal in Central Europe 5600–5300 years ago." Quaternary Research 65, no. 1 (January 2006): 3–19. http://dx.doi.org/10.1016/j.yqres.2005.06.009.
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AbstractThe history of variations in water level of Lake Constance, as reconstructed from sediment and pollen analysis of a sediment sequence from the archaeological site of Arbon-Bleiche 3, shows an abrupt rise in lake level dendrochronologically dated to 5375 yr ago (5320 yr relative to AD 1950). This event, paralleled by the destruction of the Neolithic village by fire, provoked the abandonment of this prehistoric lake-shore location established in the former shallow bay of Arbon-Bleiche, and was the last of a series of three episodes of successively higher lake level, the first occurring at 5600–5500 cal yr B.P. The dendrochronologically dated rise event was synchronous with an abrupt increase in atmospheric 14C. This supports the hypothesis of an abrupt climate change forced by varying solar activity. Moreover, the three successive episodes of higher lake level between 5600 and 5300 cal yr B.P. at Arbon-Bleiche 3 coincided with climatic cooling and/or changes in moisture conditions in various regions of both hemispheres. This period corresponds to the mid-Holocene climate transition (onset of the Neoglaciation) and suggests inter-hemispheric linkages for the climate variations recorded at Arbon-Bleiche 3. This mid-Holocene climate reversal may have resulted from complex interactions between changes in orbital forcing, ocean circulation and solar activity. Finally, despite different seasonal hydrological regimes, the similarities between lake-level records from Lake Constance and from Jurassian lakes over the mid-Holocene period point to time scale as a crucial factor in considering the possible impact of climate change on environments.
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Hansen, Katrine Elnegaard, Jacques Giraudeau, Lukas Wacker, Christof Pearce, and Marit-Solveig Seidenkrantz. "Reconstruction of Holocene oceanographic conditions in eastern Baffin Bay." Climate of the Past 16, no. 3 (June 22, 2020): 1075–95. http://dx.doi.org/10.5194/cp-16-1075-2020.
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Abstract. Baffin Bay is a semi-enclosed basin connecting the Arctic Ocean and the western North Atlantic, thus making out a significant pathway for heat exchange. Here we reconstruct the alternating advection of relatively warmer and saline Atlantic waters versus the incursion of colder Arctic water masses entering Baffin Bay through the multiple gateways in the Canadian Arctic Archipelago and the Nares Strait during the Holocene. We carried out benthic foraminiferal assemblage analyses, X-ray fluorescence scanning, and radiocarbon dating of a 738 cm long marine sediment core retrieved from eastern Baffin Bay near Upernavik, Greenland (Core AMD14-204C; 987 m water depth). Results reveal that eastern Baffin Bay was subjected to several oceanographic changes during the last 9.2 kyr. Waning deglacial conditions with enhanced meltwater influxes and an extensive sea-ice cover prevailed in eastern Baffin Bay from 9.2 to 7.9 ka. A transition towards bottom water amelioration is recorded at 7.9 ka by increased advection of Atlantic water masses, encompassing the Holocene Thermal Maximum. A cold period with growing sea-ice cover at 6.7 ka interrupts the overall warm subsurface water conditions, promoted by a weaker northward flow of Atlantic waters. The onset of the neoglaciation at ca. 2.9 ka is marked by an abrupt transition towards a benthic fauna dominated by agglutinated species, likely in part explained by a reduction of the influx of Atlantic Water, allowing an increased influx of the cold, corrosive Baffin Bay Deep Water originating from the Arctic Ocean to enter Baffin Bay through the Nares Strait. These cold subsurface water conditions persisted throughout the Late Holocene, only interrupted by short-lived warmings superimposed on this cooling trend.
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Bertrand, S., K. A. Hughen, F. Lamy, J. B. W. Stuut, F. Torrejón, and C. B. Lange. "Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield." Climate of the Past 8, no. 2 (March 15, 2012): 519–34. http://dx.doi.org/10.5194/cp-8-519-2012.
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Abstract. Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided into three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we suggest that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the North Patagonian Andes.
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Jin, Huijun, Jef Vandenberghe, Dongliang Luo, Stuart A. Harris, Ruixia He, Xuemei Chen, Xiaoying Jin, et al. "Quaternary Permafrost in China: Framework and Discussions." Quaternary 3, no. 4 (December 8, 2020): 32. http://dx.doi.org/10.3390/quat3040032.
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The framework of Quaternary permafrost in China was reconstructed for the first time on the basis of available periglacial, glacial, and other proxies. During the Early Pleistocene (2.68–0.80 Ma BP), permafrost advanced southwards to 47–50° N in northern China and possibly occurred in alpine regions in western China. During the Middle Pleistocene (800–130 ka BP), permafrost occurred extensively on the Qinghai-Tibet Plateau (QTP) and in alpine or mountainous regions of northern, western, central, and northeastern China. The Great Interglacial occurred afterward and before the Last Glaciation, but the evidence of permafrost for this period has been seldom found. Permafrost evolution of the Last Glaciation (72–19 ka BP) in China is divided into: Expansion (72~50 ka BP), degradation (50–26 ka BP), and intensive expansion during the Last Permafrost Maximum (LPMax, 26–19 ka BP) with a permafrost extent of 5.3 × 106~5.4 × 106 km2, and when major features of present permafrost took shape. Permafrost fluctuated during the Younger Dryas (12.9–11.7 ka BP). Since the Holocene, permafrost in China expanded and retreated to lesser extents, forming the current permafrost environment. The Holocene evolution of permafrost was divided into: Unstable climate but stable permafrost during the early Holocene (11.7~8.5–7.0 ka BP); permafrost degradation during the Last Permafrost Minimum (LPMin, or the Holocene Megathermal; 8.5–7.0~4.0–3.0 ka BP) and the Medieval Warm Period (MWP; 1.0~0.5 ka BP); permafrost expansion during the Neoglaciation (4.0–3.0~1.0 ka BP) and the Little Ice Age (LIA; 0.5~0.1 ka BP); and recent permafrost degradation (20th century to the present). However, this review paper only provides the framework of Quaternary permafrost in China and some preliminary discussions. Many key questions await further investigations.
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Bertrand, S., K. A. Hughen, F. Lamy, J. B. W. Stuut, F. Torrejón, and C. B. Lange. "Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield." Climate of the Past Discussions 7, no. 5 (September 19, 2011): 2937–80. http://dx.doi.org/10.5194/cpd-7-2937-2011.
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Abstract. Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided in three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we demonstrate that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the Andes.
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Pados-Dibattista, Teodora, Christof Pearce, Henrieka Detlef, Jørgen Bendtsen, and Marit-Solveig Seidenkrantz. "Holocene palaeoceanography of the Northeast Greenland shelf." Climate of the Past 18, no. 1 (January 20, 2022): 103–27. http://dx.doi.org/10.5194/cp-18-103-2022.
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Abstract. The Northeast Greenland shelf is highly sensitive to climate and ocean variability because it is swept by the East Greenland Current, which, through the western Fram Strait, forms the main pathway of export of sea ice and cold water masses from the Arctic Ocean into the North Atlantic Ocean. In order to reconstruct the variability of the East Greenland Current and general palaeoceanographic conditions in the area during the Holocene, we carried out benthic foraminiferal assemblage, stable isotope, and sedimentological analyses of a marine sediment core retrieved from the Northeast Greenland shelf (core DA17-NG-ST07-73G). The results reveal significant variations in the water masses and thus in the strength of the East Greenland Current over the last ca. 9.4 kyr. Between 9.4 and 8.2 ka the water column off Northeast Greenland was highly stratified, with cold, sea-ice-loaded surface waters and a strong influx of warm Atlantic Water in the subsurface. At ∼ 8.4 ka a short-lived peak in terrestrial elements may be linked to an influx of iceberg-transported sediments and thus to the so-called 8.2 ka event. Conditions similar to those of the Holocene Thermal Maximum prevailed from 8.2 to 6.2 ka, with a strong influence of the Return Atlantic Current and a weakened transport of Polar Water in the upper East Greenland Current. After 6.2 ka we recorded a return to a more stratified water column with sea-ice-loaded surface waters and still Atlantic-sourced subsurface waters. After 4.2 ka increased Polar Water at the surface of the East Greenland Current and a reduction in the Return Atlantic Water at subsurface levels signifies freshening and reduced stratification of the water column and (near) perennial sea-ice cover. The neoglaciation started at 3.2 ka at our location, characterized by a strengthened East Greenland Current. Cold subsurface-water conditions with possible sea-ice cover and minimum surface-water productivity persisted here throughout the last ∼ 3 kyr.
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Ning, Liang, Jian Liu, Raymond S. Bradley, and Mi Yan. "Comparing the spatial patterns of climate change in the 9th and 5th millennia BP from TRACE-21 model simulations." Climate of the Past 15, no. 1 (January 10, 2019): 41–52. http://dx.doi.org/10.5194/cp-15-41-2019.
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Abstract. The spatial patterns of global temperature and precipitation changes, as well as corresponding large-scale circulation patterns during the latter part of the 9th and 5th millennia BP (4800–4500 versus 4500–4000 BP and 9200–8800 versus 8800–8000 BP) are compared through a group of transient simulations using the Community Climate System Model version 3 (CCSM3). Both periods are characterized by significant sea surface temperature (SST) decreases over the North Atlantic, south of Iceland. Temperatures were also colder across the Northern Hemisphere but warmer in the Southern Hemisphere. Significant precipitation decreases are seen over most of the Northern Hemisphere, especially over Eurasia and the Asian monsoon regions, indicating a weaker summer monsoon. Large precipitation anomalies over northern South America and adjacent ocean regions are related to a southward displacement of the Intertropical Convergence Zone (ITCZ) in that region. Climate changes in the late 9th millennium BP (the “8.2 ka event”) are widely considered to have been caused by a large freshwater discharge into the northern Atlantic, which is confirmed in a meltwater forcing sensitivity experiment, but this was not the cause of changes occurring between the early and latter halves of the 5th millennium BP. Model simulations suggest that a combination of factors, led by long-term changes in insolation, drove a steady decline in SSTs across the North Atlantic and a reduction in the North Atlantic Meridional Overturning Circulation (AMOC), over the past 4500 years, with associated teleconnections across the globe, leading to drought in some areas. Multi-century-scale fluctuations in SSTs and AMOC strength were superimposed on this decline. This helps explain the onset of neoglaciation around 5000–4500 BP, followed by a series of neoglacial advances and retreats during recent millennia. The “4.2 ka BP Event” appears to have been one of several late Holocene multi-century fluctuations that were embedded in the long-term, low-frequency change in climate that occurred after ∼4.8 ka. Whether these multi-century fluctuations were a response to internal centennial-scale ocean–atmosphere variability or external forcing (such as explosive volcanic eruptions and associated feedbacks) or a combination of such conditions is not known and requires further study.
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Lochte, Annalena A., Ralph Schneider, Markus Kienast, Janne Repschläger, Thomas Blanz, Dieter Garbe-Schönberg, and Nils Andersen. "Surface and subsurface Labrador Shelf water mass conditions during the last 6000 years." Climate of the Past 16, no. 4 (July 3, 2020): 1127–43. http://dx.doi.org/10.5194/cp-16-1127-2020.
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Abstract. The Labrador Sea is important for the modern global thermohaline circulation system through the formation of intermediate Labrador Sea Water (LSW) that has been hypothesized to stabilize the modern mode of North Atlantic deep-water circulation. The rate of LSW formation is controlled by the amount of winter heat loss to the atmosphere, the expanse of freshwater in the convection region and the inflow of saline waters from the Atlantic. The Labrador Sea, today, receives freshwater through the East and West Greenland currents (EGC, WGC) and the Labrador Current (LC). Several studies have suggested the WGC to be the main supplier of freshwater to the Labrador Sea, but the role of the southward flowing LC in Labrador Sea convection is still debated. At the same time, many paleoceanographic reconstructions from the Labrador Shelf focussed on late deglacial to early Holocene meltwater run-off from the Laurentide Ice Sheet (LIS), whereas little information exists about LC variability since the final melting of the LIS about 7000 years ago. In order to enable better assessment of the role of the LC in deep-water formation and its importance for Holocene climate variability in Atlantic Canada, this study presents high-resolution middle to late Holocene records of sea surface and bottom water temperatures, freshening, and sea ice cover on the Labrador Shelf during the last 6000 years. Our records reveal that the LC underwent three major oceanographic phases from the mid- to late Holocene. From 6.2 to 5.6 ka, the LC experienced a cold episode that was followed by warmer conditions between 5.6 and 2.1 ka, possibly associated with the late Holocene thermal maximum. While surface waters on the Labrador Shelf cooled gradually after 3 ka in response to the neoglaciation, Labrador Shelf subsurface or bottom waters show a shift to warmer temperatures after 2.1 ka. Although such an inverse stratification by cooling of surface and warming of subsurface waters on the Labrador Shelf would suggest a diminished convection during the last 2 millennia compared to the mid-Holocene, it remains difficult to assess whether hydrographic conditions in the LC have had a significant impact on Labrador Sea deep-water formation.
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Bohleber, Pascal, Margit Schwikowski, Martin Stocker-Waldhuber, Ling Fang, and Andrea Fischer. "New glacier evidence for ice-free summits during the life of the Tyrolean Iceman." Scientific Reports 10, no. 1 (December 2020). http://dx.doi.org/10.1038/s41598-020-77518-9.
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AbstractDetailed knowledge of Holocene climate and glaciers dynamics is essential for sustainable development in warming mountain regions. Yet information about Holocene glacier coverage in the Alps before the Little Ice Age stems mostly from studying advances of glacier tongues at lower elevations. Here we present a new approach to reconstructing past glacier low stands and ice-free conditions by assessing and dating the oldest ice preserved at high elevations. A previously unexplored ice dome at Weißseespitze summit (3500 m), near where the “Tyrolean Iceman” was found, offers almost ideal conditions for preserving the original ice formed at the site. The glaciological settings and state-of-the-art micro-radiocarbon age constraints indicate that the summit has been glaciated for about 5900 years. In combination with known maximum ages of other high Alpine glaciers, we present evidence for an elevation gradient of neoglaciation onset. It reveals that in the Alps only the highest elevation sites remained ice-covered throughout the Holocene. Just before the life of the Iceman, high Alpine summits were emerging from nearly ice-free conditions, during the start of a Mid-Holocene neoglaciation. We demonstrate that, under specific circumstances, the old ice at the base of high Alpine glaciers is a sensitive archive of glacier change. However, under current melt rates the archive at Weißseespitze and at similar locations will be lost within the next two decades.
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Price, Brittany N., Nathan D. Stansell, Alfonso Fernández, Joseph M. Licciardi, Alia J. Lesnek, Ariel Muñoz, Mary K. Sorensen, et al. "Chlorine-36 Surface Exposure Dating of Late Holocene Moraines and Glacial Mass Balance Modeling, Monte Sierra Nevada, South-Central Chilean Andes (38°S)." Frontiers in Earth Science 10 (July 5, 2022). http://dx.doi.org/10.3389/feart.2022.848652.
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The development of robust chronologies of Neoglaciation from individual glaciers throughout the high-altitude Andes can provide fundamental knowledge of influences such as regional temperature and precipitation variability, and aid in predicting future changes in the Andean climate system. However, records of Late Holocene glaciation from the Central Chilean Andes are sparse, and often poorly constrained. Here, we present 36Cl surface exposure ages, dendrochronologic constraints, and glacial mass balance modeling simulations of Late Holocene glacier fluctuations in the Central-South Chilean Andes. A series of concentric moraine ridges were identified on Monte Sierra Nevada (38°S), where exposure dating of basaltic boulders was used to establish a chronology of ice recession. We infer that moraine abandonment of the most distal ridge in the valley commenced by ∼4.2 ka, and was followed by glacier margin retreat to an up-valley position. Exposure ages of the oldest Late Holocene boulders (∼2.5–0.8 ka) along the marginal extents of the moraine complex indicate fluctuations of the glacier terminus prior to ∼0.65 ka. A final expansion of the ice margin reoccupied the position of the 4.2 ka moraine, with abatement from the outermost composite moraine occurring by ∼0.70 ka, as constrained by tree-ring data from live Araucaria araucana trees. Finally, a series of nested moraines dating to ∼0.45–0.30 ka, formed from a pulsed ice recession during the latest Holocene when the lower reaches of the glacial snout was most likely debris mantled. A distributed temperature index model combined with a glacier flow model was used to quantify an envelope of possible climatic conditions of Late Holocene glaciation. The glacial modeling results suggest conditions were ∼1.5°C colder and 20% wetter during peak Neoglaciation relative to modern conditions. These records also suggest a near-coeval record of Late Holocene climate variability between the middle and high southern latitudes. Furthermore, this study presents some of the youngest 36Cl exposure ages reported for moraines in the Andes, further supporting this method as a valuable geochronologic tool for assessing Late Holocene landscape development.
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Wang, Jiao, Peng Cui, Hao Wang, Guotao Zhang, Qiang Zou, and Xiaoqing Chen. "Novel Approach to Estimating Glacial Moraine Reserves in the Parlung Tsangpo Basin." Frontiers in Earth Science 10 (April 5, 2022). http://dx.doi.org/10.3389/feart.2022.853089.
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The Sichuan–Tibet Railway crosses through the largest maritime glacier region in China. A large number of moraines formed after the rapid glacial retreat caused by climate warming. Moraines could induce frequent geological hazards that seriously threatened the safe construction and operation of the railway. Accordingly, moraines in this maritime glacier region have become a new challenging research topic with respect to the formation of geological hazards. Using remote-sensing image interpretations, field investigations, and dating tests, moraines and their topographic information were systematically obtained. After analyzing the geometrical distribution characteristics of the moraine accumulations, the geometrical characteristics of three typical moraine accumulation forms were generalized into corresponding mathematical models. Consequently, a method to quickly and quantitatively estimate the moraine reserves is proposed. The moraine distribution is primarily affected by the elevation, slope, river–valley morphology, and climate conditions. Old moraines that formed in the Pleistocene epoch (the Guxiang and Baiyu glacial periods) are primarily distributed below 3,500 m above sea level, while most of the new moraines that formed in the Holocene epoch (Neoglaciation and Little Ice Age) are primarily distributed above 4,000 m above sea level. Both the new and old moraines are primarily distributed within a slope range of 10–30°. Furthermore, the main river–valley morphology has a significant impact on the distribution of the old moraines, which are primarily distributed in the Zhongba–Guxiang section of the river valley where the longitudinal slope is relatively gentle. The difference in glaciation is the main reason why the new moraines distributed on the south banks in the study area are different from those on the north banks and why those distributed upstream are different from those distributed downstream. In addition, moraines are the main source of glacial debris flows. According to the presented method, the loose moraine reserves can be accurately calculated by analyzing the position, consolidation, and supply capability of the new and old moraines in each debris flow gully. It is anticipated that the presented results can be used to better understand the formation mechanisms of glacier-related hazards and improve risk assessments.