Cryospheric and Polar Processes Seminar
Paleo-environmental studies on permafrost deposits in western Beringia - from field sampling to lab analysis to regional synthesis by Lutz Schirrmeister, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Potsdam
The Department of Periglacial Research of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research is studying permafrost deposits as paleo-environmental archives. We have been working on this topic successfully with collaborators from Russia and North America for more than 20 years: Starting in the 1990’s in Siberia on Taymyr Peninsula, we continued with field studies further east along the Laptev Sea and East Siberian coasts, in Central Yakutia, as well as on the Chukotka Peninsula. In addition, in the early 2000’s we started field investigations of permafrost deposits in Alaska and Northwest Canada.
In the beginning of my presentation I will provide a short introduction about our institute, especially the Periglacial Research unit, located in AWI’s Potsdam site near Berlin. Based on my almost 20 years’ experience in the periglacial department I will then focus on my own research field and projects. Starting with some visual impressions of field work in Siberia, I will show the conditions of sample collection and field measurements, and how these conditions have changed during the last two decades. Sampling of permafrost outcrops and cores as well as sampling of unfrozen active layer and lake sediments resulted in a broad range of sample materials from a diverse set of cryostratigraphies, which we used for different sedimentological, geochronological, hydrochemical, mineralogical, and paleoecolgoical studies in order to reconstruct periglacial paleoenvironments in our research area.
Using this multidisciplinary approach, we are able to reconstruct paleo-environmental conditions for the last 200.000 years at several Arctic sites. We use such windows into the past as an analogue to future warming, and reconstruction of the landscape for improved process understanding (e.g. soil, plants, geomorphology). Our focus is largely on the late Pleistocene and Holocene periods covering the last 50.000 years. During this period, large areas in northeastern Siberia, northern Alaska, and northwest Canada were not glaciated, including during the ice age. This region, including the Arctic shelf regions subaerially exposed during the late Pleistocene, is called Beringia.
I will present results from our studies covering old pre-Eemian (Sangamon) permafrost with large ice wedges, which were partially thawed during the interglacial warming ca. 125.000 years ago. I was able to study ice wedge casts including interglacial lake deposits and flood plain sediments deposited during the early Weichselian (Wisconsinan), as well as ice-rich permafrost, called Yedoma (mid and late Wisconsian). Finally there was a great change in the landscape geomorphology and environmental conditions induced by the warming period at the late Pleistocene Holocene transition. This period in Beringia was marked by
- the extinction of the mammoth fauna and the connected tundra-steppe flora
- the rise of the global sea level and the flooding of the Arctic shelves
- the restructuring of the hydrological networks because of thawing of large Yedoma Ice Complex areas, and
- the formation of the modern periglacial tundra landscapes with numerous thermokarst lakes and basins as well as thermo-erosional gullies.
Finally, I will give an outlook on current research and future work of our group at the Periglacial Research unit of AWI with a particular focus on permafrost organic carbon dynamics in the Yedoma region as well as modern ecological analogues to fossil bio-indicators.
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