Rapid degradation of permafrost underneath waterbodies in tundra landscapes-Toward a representation of thermokarst in land surface models

• Published in: Journal of Geophysical Research: Earth Surface
• Main Authors: Langer, M., Westermann, S., Boike, J., Kirillin, G., Grosse, G., Peng, S., Krinner, G.
• Other Authors: Langer, M (reprint author), Humboldt Univ, Dept Geog, Berlin, Germany.; Langer, M (reprint author), CNRS, LGGE, UMR5183, Grenoble, France.; Langer, M (reprint author), Alfred Wegener Inst, Helmholtz Zentrum Polar & Meeresforsch, Potsdam, Germany., Humboldt Univ, Dept Geog, Berlin, Germany., CNRS, LGGE, UMR5183, Grenoble, France., Alfred Wegener Inst, Helmholtz Zentrum Polar & Meeresforsch, Potsdam, Germany., Univ Oslo, Dept Geosci, Oslo, Norway., Leibniz Inst Freshwater Ecol & Inland Fisheries I, Berlin, Germany., Univ Potsdam, Inst Earth & Environm Sci, Potsdam, Germany., Peking Univ, Sinofrench Inst Earth Syst Sci, Coll Urban & Environm Sci, Beijing, Peoples R China., Langer, M (reprint author), CNRS, LGGE, UMR5183, Grenoble, France., Langer, M (reprint author), Alfred Wegener Inst, Helmholtz Zentrum Polar & Meeresforsch, Potsdam, Germany.
• Format: Journal/Newspaper
• Language: English
• Published: JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE 2016
• Subjects: LENA RIVER DELTA; ARCTIC COASTAL-PLAIN; ICE-RICH PERMAFROST; NORTHERN SIBERIA; THAW LAKES; CARBON-DIOXIDE; WATER TEMPERATURE; THERMAL REGIME; ENERGY BALANCE; SNOW COVER; Arctic; Norway; Ice; lena river; permafrost; Thermokarst; Tundra; Siberia
• Online Access: https://hdl.handle.net/20.500.11897/458165; https://doi.org/10.1002/2016JF003956

Waterbodies such as lakes and ponds are abundant in vast Arctic landscapes and strongly affect the thermal state of the surrounding permafrost. In order to gain a better understanding of the impact of small-and medium-sized waterbodies on permafrost and the formation of thermokarst, a land surface model was developed that can represent the vertical and lateral thermal interactions between waterbodies and permafrost. The model was validated using temperature measurements from two typical waterbodies located within the Lena River delta in northern Siberia. Impact simulations were performed under current climate conditions as well as under a moderate and a strong climate-warming scenario. The performed simulations demonstrate that small waterbodies can rise the sediment surface temperature by more than 10 degrees C and accelerate permafrost thaw by a factor of between 4 and 5. Up to 70% of this additional heat flux into the ground was found to be dissipated into the surrounding permafrost by lateral ground heat flux in the case of small, shallow, and isolated waterbodies. Under moderate climate warming, the lateral heat flux was found to reduce permafrost degradation underneath waterbodies by a factor of 2. Under stronger climatic warming, however, the lateral heat flux was too small to prevent rapid permafrost degradation. The lateral heat flux was also found to strongly impede the formation of thermokarst. Despite this stabilizing effect, our simulations have demonstrated that underneath shallow waterbodies (<1 m), thermokarst initiation happens 30 to 40 years earlier than in simulations without preexisting waterbody. Feodor Lynen Fellowship of the Alexander von Humboldt Foundation; European Union FP7-ENV project PAGE21 [GA282700]; COUP [244903/E10]; COUP (JPI Climate); COUP (Research Council of Norway); ERC [338335] SCI(E) ARTICLE [e-mail] 12 2446-2470 121