Degradation of Lena Delta Ice Complex by thermokarst and thermal erosion

• Main Authors: Morgenstern, Anne, Fedorova, Irina, Bobrova, Olga, Boike, Julia, Chetverova, Antonina, Eulenburg, Antje, Günther, Frank, Heim, Birgit, Overduin, Paul, Rethemeyer, Janet, Skorospekhova, Tatyana, Ulrich, Mathias, Schirrmeister, Lutz
• Format: Conference Object
• Language: unknown
• Published: 2018
• Subjects: Ice; lena delta; lena river; permafrost; Thermokarst
• Online Access: https://epic.awi.de/id/eprint/49370/; https://hdl.handle.net/10013/epic.cd0ba8b5-cc3d-4943-b360-632720d8e2de

During the past decade, we have studied thermokarst and thermo-erosional processes and landforms in Ice Complex deposits of the Lena Delta. Ice Complex deposits are very ice-rich permafrost up to tens of meters thick. They are widespread in the Arctic and have attracted raising attention due to their vulnerability to thaw under climatic warming. In the Lena Delta they occur on the third geomorphological main terrace, which is distributed as several islands in the southern delta. Degradation processes throughout the Holocene have affected these late Pleistocene deposits. Rapid permafrost thaw underneath ponding water (thermokarst) has created thermokarst lakes; when these lakes drain, thermokarst basins remain that can be several kilometers wide and up to twenty meters deep. Rapid permafrost thaw by running water (thermal erosion) has created gullies, valleys and valley networks that are also deeply incised into the terrain surface. All these landforms and associated processes play an important role for the landscape’s hydrology, energy budget and carbon cycle. Our investigations have aimed at 1) understanding the evolution of thermokarst and thermal erosion in the Lena Delta Ice Complex throughout the Holocene, 2) quantifying current terrain changes (permafrost degradation and aggradation) as well as the contribution of different landform types to organic matter export from the Ice Complex to the Lena River, and 3) deducing potential future thermokarst and thermo-erosional activity. Our methodological approach has been a combination of geomorphological analyses in the field and based on satellite imagery and digital elevation models (DEM), sediment and water sampling. As main results we would like to highlight the following: - Thermokarst development started during the transition from Pleistocene to Holocene and has evolved throughout the Holocene. - Only a minor part of the third terrace in the Lena Delta provides the conditions for the future formation of thermokarst and thermo-erosional landforms, because a ...