A centennial record of fluvial organic matter input from the discontinuous permafrost catchment of Lake Torneträsk

• Published in: Journal of Geophysical Research Vol. 117; no. G3; pp. 1 - n/a
• Main Authors: Vonk, Jorien E., Alling, Vanja, Rahm, Lars, Mörth, Carl-Magnus, Humborg, Christoph, Gustafsson, Örjan
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.09.2012; American Geophysical Union
• Subjects: Biogeochemistry; biomarkers; boreal lakes; Carbon; carbon cycling; Climate change; climate warming; Cryosphere; d13C; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geobiology; Global warming; Isotopes; Lakes; Mineralization; Mountain lakes; n-alkanes; Organic carbon; Organic matter; Peat; Permafrost; radiocarbon; sediment; Soil degradation; sub-Arctic; subarctic; Terrestrial environments; TOC; Water inflow; polar regions; Scandinavia; Europe; Arctic region; High latitude; active layer; reservoirs; degradation; remobilization; Earth; drainage basins; drill cores; lakes; soils; peat; Carbon 13; organic carbon; climate change; climate warming; concentration; climate; isotherms; baseline; Subpolar zone; C-14; mineralization; permafrost; erosion; organic materials
• ISSN: 0148-0227; 2169-8953; 2156-2202; 2156-2202; 2169-8961
• DOI: 10.1029/2011JG001887

High‐latitude regions are underlain by the most organic carbon (OC)‐rich soils on earth and currently subject to intense climate warming, potentially increasing remobilization and mineralization of soil OC. Sub‐Arctic Scandinavia is located on the 0°C mean annual isotherm and is therefore particularly vulnerable to climate change. This study aimed to establish a baseline for soil OC release over the past century into Lake Torneträsk, the largest lake in sub‐Arctic Scandinavia, through bulk geochemical and molecular radiocarbon analyses in chronologically constrained sediment cores. Our results suggest a dominance of peat‐derived terrestrial OC inflow. We show that the annual terrestrial OC inflow to the lake is ∼12 times higher than the in‐lake produced particulate OC, and consists for a large part (ca. 60%) of old OC from deep reservoirs in the catchment. The sedimentary record shows signs of increasing inflow of more degraded terrestrial matter since ∼1975, as indicated by increasing %TOC concentrations, a lowerδ13C value and lower TOC:TN ratios. Based on simultaneous changes in local climate and reported signs of permafrost degradation (e.g., active layer deepening, mire/peat erosion), the observed changes in the sedimentary record of Scandinavia's largest mountain lake likely reflect a climate warming‐induced change in terrestrial OC inflow. Key Points We observe an increase in degraded terrestrial OC from permafrost degradation Old OC plays a large role in sub‐Arctic contemporary OC cycling Ecosystems around the 0 degree isotherm may already be recording climate change