Abstract
Abstract. Lakes in permafrost regions are dynamic landscape components and play an important role for climate change feedbacks. Lake processes such as mineralization and flocculation of dissolved organic carbon (DOC), one of the main carbon fractions in lakes, contribute to the greenhouse effect and are part of the global carbon cycle. These processes are in the focus of climate research, but studies so far are limited to specific study regions. In our synthesis, we analyzed 2167 water samples from 1833 lakes across the Arctic in permafrost regions of Alaska, Canada, Greenland, and Siberia to provide first pan-Arctic insights for linkages between DOC concentrations and the environment. Using published data and unpublished datasets from the author team, we report regional DOC differences linked to latitude, permafrost zones, ecoregions, geology, near-surface soil organic carbon contents, and ground ice classification of each lake region. The lake DOC concentrations in our dataset range from 0 to 1130 mg L−1 (10.8 mg L−1 median DOC concentration). Regarding the permafrost regions of our synthesis, we found median lake DOC concentrations of 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 synthesis shows a significant relationship between lake DOC concentration and lake ecoregion. We found higher lake DOC concentrations at boreal permafrost sites compared to tundra sites. We found significantly higher DOC concentrations in lakes in regions with ice-rich syngenetic permafrost deposits (yedoma) compared to non-yedoma lakes and a weak but significant relationship between soil organic carbon content and lake DOC concentration as well as between ground ice content and lake DOC. Our pan-Arctic dataset shows that the DOC concentration of a lake depends on its environmental properties, especially on permafrost extent and ecoregion, as well as vegetation, 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 pool for estimations of the impact of lake DOC on the global carbon cycle and climate change.
Highlights
At northern high latitudes where mean annual ground temperatures are below 0 ◦C, permafrost has been an important carbon (C) sink for thousands of years since freezing is one of the most effective mechanisms for longterm C fixation in soils (Schuur et al, 2008; Grosse et al, 2011)
The objectives of this study are to synthesize existing datasets of lake dissolved organic carbon (DOC) in northern permafrost regions, to provide first insights into linkages between DOC concentration and environmental parameters, and to identify drivers for lake DOC concentration in this region affected by rapid climate change
While we showed that lake DOC concentration is influenced by permafrost extent and type of ecoregion, they do not explain all of the variability in the dataset
Summary
At northern high latitudes where mean annual ground temperatures are below 0 ◦C, permafrost has been an important carbon (C) sink for thousands of years since freezing is one of the most effective mechanisms for longterm C fixation in soils (Schuur et al, 2008; Grosse et al, 2011). Arctic permafrost regions have experienced an increase of permafrost temperatures by 0.5 to 2 ◦C and a local deepening of the active layer of up to 90 cm since the 1970s (Romanovsky et al, 2010; IPCC, 2013; Biskaborn et al, 2019). Permafrost warmed globally by an average of 0.29 ◦C ± 0.12 ◦C over the 2007– 2016 period due to higher air temperatures, with some of the strongest warming trends (about 0.9 ◦C per decade) measured in individual boreholes at the polar stations Marre Sale in northwest Siberia and Samoylov Island in northeast Siberia (Biskaborn et al, 2019). The impact of global climate change on permafrost regions and their C cycling has to be thoroughly investigated
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