AI Article Synopsis
- The Arctic's changing climate is causing increased thermokarst formation and erosion, which mobilizes terrestrial organic matter (OM) into nearshore zones.
- A study on Qikiqtaruk - Herschel Island found that disturbances in permafrost led to significant losses of total organic carbon (TOC) and nitrogen (TN), with a decline of up to 77% for TOC after thawing.
- The research suggests that this loss is due to initial dilution from melting ice and degradation processes, while nutrients are introduced into coastal environments, affecting their ecosystems.
Article Abstract
The changing climate in the Arctic has a profound impact on permafrost coasts, which are subject to intensified thermokarst formation and erosion. Consequently, terrestrial organic matter (OM) is mobilized and transported into the nearshore zone. Yet, little is known about the fate of mobilized OM before and after entering the ocean. In this study we investigated a retrogressive thaw slump (RTS) on Qikiqtaruk - Herschel Island (Yukon coast, Canada). The RTS was classified into an undisturbed, a disturbed (thermokarst-affected) and a nearshore zone and sampled systematically along transects. Samples were analyzed for total and dissolved organic carbon and nitrogen (TOC, DOC, TN, DN), stable carbon isotopes (δC-TOC, δC-DOC), and dissolved inorganic nitrogen (DIN), which were compared between the zones. C/N-ratios, δC signatures, and ammonium (NH-N) concentrations were used as indicators for OM degradation along with biomarkers (n-alkanes, n-fatty acids, n-alcohols). Our results show that OM significantly decreases after disturbance with a TOC and DOC loss of 77 and 55% and a TN and DN loss of 53 and 48%, respectively. C/N-ratios decrease significantly, whereas NH-N concentrations slightly increase in freshly thawed material. In the nearshore zone, OM contents are comparable to the disturbed zone. We suggest that the strong decrease in OM is caused by initial dilution with melted massive ice and immediate offshore transport via the thaw stream. In the mudpool and thaw stream, OM is subject to degradation, whereas in the slump floor the nitrogen decrease is caused by recolonizing vegetation. Within the nearshore zone of the ocean, heavier portions of OM are directly buried in marine sediments close to shore. We conclude that RTS have profound impacts on coastal environments in the Arctic. They mobilize nutrients from permafrost, substantially decrease OM contents and provide fresh water and nutrients at a point source.
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| http://dx.doi.org/10.1016/j.scitotenv.2016.12.152 | DOI Listing |
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