Long-term accumulation of organic carbon in West Antarctic deglaciating fjords

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Abstract
Despite increasing recognition of the importance of polar fjords as an emerging carbon sink, relatively few estimates of organic carbon stocks, deposition and accumulation potential exist for the West Antarctic Peninsula (WAP). We assessed the long-term accumulation of organic carbon in three deglaciating Antarctic fjords by combining total organic carbon (TOC) and 210Pb measurements. These data enabled calculations of carbon flux and sequestration (carbon remaining after 100 years), while the susceptibility of the carbon pool to further degradation was assessed by thermogravimetric analysis (TGA). Organic carbon surface deposition rates were highly variable (11.99 ± 8.27 g C m-2 yr-1), while organic carbon burial rates were more consistent (3.55 ± 1.75 g C m-2 yr-1). Burial efficiencies ranged from 30.59% to 54.44% (mean 39.84%). These results are comparable with previous predictions of carbon sequestration in WAP fjords, highlighting the role of fjords as global hotspots of long-term accumulation, and support the hypothesis that deglaciating polar fjords act as a significant negative (mitigating) feedback on global climate change.

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