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Lake archives in Canada and Alaska: Do we see effects of polar climate change during the Early Holocene?

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Lenz, J. , Fritz, M. , Wetterich, S. , Schirrmeister, L. , Lantuit, H. and Pollard, W. (2012): Lake archives in Canada and Alaska: Do we see effects of polar climate change during the Early Holocene? , IPY2012 Conference - From Knowledge to Action, Montréal, Canada, 22 April 2012 - 27 April 2012 .
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Abstract:

Terrestrial deposits provide valuable information about past landscape development in the Arctic. Especially lake sediments as continuous records are highly important to comprehend the post-glacial dynamic of the periglacial environment in northern Canada and Alaska. It is crucial to evaluate already studied and published paleoenvironmental archives as well as to fill gaps of knowledge to gain a better understanding of the past, present and future polar climate change. Various literary sources were studied to get an overall picture of climate records in the North American Arctic. Since environmental archives are relatively rare in the western Canadian Arctic a lake sediment record from Herschel Island (Yukon Territory) was analyzed as a case study using radio carbon age determination and several sedimentological and geochemical methods. Many authors draw the conclusion that a progressive amelioration of climate conditions with warmer-than-modern levels of air temperatures was reached during the period of 11,000 to 8,500 cal. a BP in the western Canadian Arctic and Alaska (e.g. Szeicz and MacDonald 2001, Bigelow and Edwards 2001). Also Herschel Island’s lake archive demonstrate an early Holocene warming by about 10,300 to 8,800 cal. a BP: variations in nitrogen, total organic carbon content and stable carbon isotopes indicate the lake onset by pooling of water and thaw subsidence of the ice-rich permafrost. The Pleistocene-Holocene transition was a period of dramatic and rapid environmental changes, particularly at coastal sites. The formation of thermokarst lakes in permafrost regions was extremely intense during the Holocene Thermal Maximum (HTM). On the coastal plain in the western Canadian Arctic thermokarst lakes developed especially between 11,600 and 10,300 a BP (Rampton 1988) – so did the lake on Herschel Island in all likelihood. According to Kaufman et al. (2004) the HTM was time-transgressive, which means the western Canadian Arctic warmed earlier (11,300+/-1,500 a BP) than northern continental Canada (7,300+/-1,600 a BP). Also the duration of the HTM in eastern Canada was about 1,000 years shorter. Both can be explained due to the remnants of the Laurentide Ice Sheet and the cooling effect of the Greenland ice cap. The overall pattern of Holocene climate change is expressed in several records in the North American Arctic. We are recently noticing thermokarst processes and effects of permafrost degradation due to global climate change. Thus, understanding the past environmental effects on polar landscapes and especially on lake systems is extremely valuable to appraise present und future polar climate change. References: Bigelow, N.H.; Edwards, M.E. (2001). A 14000 yr paleoenvironmental record from Windmill Lake, Central Alaska: Lateglacial and Holocene vegetation in the Alaska range. Quaternary Science Reviews, 20: 203-215. Kaufman, D.S.; Ager, T.A.; Anderson, N.J. et al (2004). Holocene thermal maximum in the western Arctic (0-180°W). Quaternary Science Reviews, 23: 529-560. Rampton, V.N. (1988). Quaternary geology of the Tuktoyaktuk Coastlands, Northwest Territories. Geological Survey of Canada. Memoir, 423. Szeicz, J.M.; MacDonald, G.M. (2001). Montane climate and vegetation dynamics in easternmost Beringia during the Late Quaternary. Quaternary Science Reviews, 20: 247-257.

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