Landscape-Scale Variability of Organic Carbon Burial by SW Greenland Lakes

Lakes are a key feature of arctic landscapes and can be an important component of regional organic carbon (OC) budgets, but C burial rates are not well estimated. Pb-210-dated sediment cores and carbon and organic matter (as loss-on-ignition) content were used to estimate OC burial for 16 lakes in SW Greenland. Burial rates were corrected for sediment focusing using the Pb-210 flux method. The study lakes span a range of water chemistries (conductivity range 25-3400 mu S cm(-1)), areas (< 4-100 ha) and maximum depths (similar to 10-50 m). The regional average focusing-corrected OC accumulation rate was similar to 2 g C m(-2) y(-1) prior to 1950 and 3.6 g C m(-2) y(-1) after 1950. Among-lake variability in post-1950 OC AR was correlated with in-lake dissolved organic carbon concentration, conductivity, altitude and location along the fjord. Twelve lakes showed an increase in mean OC AR over the analyzed time period, similar to 1880-2000; as the study area was cooling until recently, this increase is probably attributable to other global change processes, for example, altered inputs of N or P. There are similar to 20,000 lakes in the study area ranging from similar to 1 ha to more than 130 km(2), although over 83% of lakes are less than 10 ha. Extrapolating the mean post-1950 OC AR (3.6 g C m(-2) y(-1)) to all lakes larger than 1000 ha and applying a lower rate of similar to 2 g C m(-2) y(-1) to large lakes (> 1000 ha) suggests a regional annual lake OC burial rate of similar to 10.14 x 10(9) g C y(-1) post 1950. Given the low C content of soils in this area, lakes represent a substantial regional C store.