Holocene carbon burial by lakes in SW Greenland

The role of the Arctic in future global change processes is predicted to be important because of the large carbon (C) stocks contained in frozen soils and peatlands. Lakes are an important component of arctic landscapes although their role in storing C is not well prescribed. The area around Kangerlussuaq, SW Greenland (66–68°N, 49–54°W) has extremely high lake density, with ~20 000 lakes that cover about 14% of the land area. C accumulation rates and standing stock (kg C m−2), representing lateto mid-Holocene C burial, were calculated from AMS 14C-dated sediment cores from 11 lakes. Lake ages range from ~10 000 cal yr bp to ~5400 cal yr bp, and reflect the withdrawal of the ice sheet from west to east. Total standing stock of C accumulated in the studied lakes for the last ~8000 years ranged from 28 to 71 kg C m−2, (mean: ~42 kg C m−2). These standing stock determinations yield organic C accumulation rates of 3.5–11.5 g C m−2 yr−1 (mean: ~6 g C m−2 yr−1) for the last 4500 years. Mean C accumulation rates are not different for the periods 8–4.5 and 4.5– 0 ka, despite cooling trends associated with the neoglacial period after 4.5 ka. We used the mean C standing stock to estimate the total C pool in small lakes (<100 ha) of the Kangerlussuaq region to be ~4.9 × 1013 g C. This C stock is about half of that estimated for the soil pool in this region (but in 5% of the land area) and indicates the importance of incorporating lakes into models of regional C balance at high latitudes.