Search for: All records

The rapid climate warming is affecting the Arctic which is rich in aquatic systems. As a result of permafrost thaw, thermokarst lakes and ponds are either shrinking due to lake drainage or expanding due to lake shore erosion. This process in turn mobilizes organic carbon, which is released by permafrost deposits and active layer material that slips into the lake. In this study, we combine hydrochemical measurements and remote sensing data to analyze the influence of lake change processes, especially lake growth, on lake hydrochemical parameters such as DOC, EC, pH as well as stable oxygen and hydrogen isotopes in the Arctic Coastal Plain. For our entire dataset of 97 water samples from 82 water bodies, we found significantly higher CH4 concentrations in lakes with a floating-ice regime and significantly higher DOC concentrations in lakes with a bedfast-ice regime. We show significantly lower CH4 concentrations in lagoons compared to lakes as a result of an effective CH4 oxidation that increased with a seawater connection. For our detailed lake sampling of two thermokarst lakes, we found a significant positive correlation for lake shore erosion and DOC for one of the lakes. Our detailed lake sampling approach indicates that the generally shallow thermokarst lakes are overall well mixed and that single hydrochemical samples are representative for the entire lake. Finally, our study confirms that DOC concentrations correlates with lake size, ecoregion type and underlying deposits. 

Abstract. Lakes in permafrost regions are dynamic landscapecomponents and play an important role for climate change feedbacks. Lakeprocesses such as mineralization and flocculation of dissolved organiccarbon (DOC), one of the main carbon fractions in lakes, contribute to thegreenhouse effect and are part of the global carbon cycle. These processesare in the focus of climate research, but studies so far are limited to specificstudy regions. In our synthesis, we analyzed 2167 water samples from 1833lakes across the Arctic in permafrost regions of Alaska, Canada, Greenland,and Siberia to provide first pan-Arctic insights for linkages between DOCconcentrations and the environment. Using published data and unpublisheddatasets from the author team, we report regional DOC differences linked tolatitude, permafrost zones, ecoregions, geology, near-surface soil organiccarbon contents, and ground ice classification of each lake region. The lakeDOC concentrations in our dataset range from 0 to1130 mg L−1 (10.8 mg L−1 median DOC concentration). Regarding thepermafrost regions of our synthesis, we found median lake DOC concentrationsof 12.4 mg L−1 (Siberia), 12.3 mg L−1 (Alaska),10.3 mg L−1 (Greenland), and 4.5 mg L−1 (Canada). Our synthesisshows a significant relationship between lake DOC concentration and lakeecoregion. We found higher lake DOC concentrations at boreal permafrostsites compared to tundra sites. We found significantly higher DOCconcentrations in lakes in regions with ice-rich syngenetic permafrostdeposits (yedoma) compared to non-yedoma lakes and a weak but significantrelationship between soil organic carbon content and lake DOC concentrationas well as between ground ice content and lake DOC. Our pan-Arctic datasetshows that the DOC concentration of a lake depends on its environmentalproperties, especially on permafrost extent and ecoregion, as well asvegetation, which is the most important driver of lake DOC in this study.This new dataset will be fundamental to quantify a pan-Arctic lake DOC poolfor estimations of the impact of lake DOC on the global carbon cycle andclimate change.