The Yukon Coastal Plain facing the Southern Beaufort Sea was only partly glaciated during the last glacial maximum (LGM). Large areas remained ice-free and became part of the vast unglaciated land mass − Beringia − and are therefore an excellent study site to reconstruct paleoenvironmental dynamics where records since the Late Pleistocene are still sparse.Multi-proxy analyses on sediments and stable isotope analyses on ground ice samples have been performed to unravel periglacial processes towards sedimentary history, permafrost aggradation and degradation through time as well as to link these processes to distinct periods of climatic change. Sediments within the glacial limit generally consist of clayey diamicton and sandy silts with varying amounts of pebbles, cobbles and organic remains. Stratigraphic appraisals are difficult due to the deformed nature of the morainic ridge sediments. Nevertheless, a radiocarbon dated peat suggests that until 8.4 ka BP bioproductivity was inhibited due to continuous harsh climate conditions. During the Holocene Thermal Maximum (HTM) thaw lakes developed and a rapid accumulation of peat followed on polygonal ground. An extensive active layer thickening is recorded by a widespread thaw unconformity along the Yukon coast at depths between 1.2 to 2.0 m below surface.Different types of ground ice recovered range widely regarding their isotopic composition, thus reflecting different types of water and strongly variable climatic conditions during ground ice development. The oxygen isotopic signature of Holocene ice wedges varies between −20 to −24 , which generally agrees with the supposition that recent temperatures are supposed to produce δ18O values of about −20 in the study area. In contrast, relict ice wedges revealed oxygen isotopic values ranging from −27 to −30 . This leads to the assumption that the study area comprises ice wedges that formed likely prior to the HTM (probably during the Late Pleistocene) and afterwards.
Helmholtz Research Programs > PACES I (2009-2013) > TOPIC 1: The Changing Arctic and Antarctic > WP 1.5: The Role of degrading Permafrost and Carbon Turnover in the Coastal, Shelf and Deep-Sea Environment