Holocene carbon burial by lakes in SW Greenland

Abstract

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 late‐ to 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.

Land-use change, not climate, controls organic carbon burial in lakes

“…Lakes are an important part of the annual terrestrial C cycle in lake-rich landscapes [2], and compared with terrestrial soils, which respire most OC inputs, lake sediments are a longterm sink [5,9]. Although lakes are not normally included in regional terrestrial C budgets [37], they can have a large effect on net ecosystem storage if the rates of either aquatic production or respiration (loss rates) are substantially altered [39].…”

“…Land-cover and land-use change strongly influence both DOC export from terrestrial ecosystems as well as the primary productivity of lakes [8]. Although OC burial rates are relatively constant in the absence of significant land-cover change [5,9], the effect of changing land cover on burial/storage in lakes has only been examined at a limited number of sites [10].…”

Contribution of sediment focussing to heterogeneity of organic carbon and phosphorus burial in small lakes

“…As many carbon burial rate studies are explicitly sampled at the deepest point in the lake or areas where sediment accumulation is most rapid (e.g. Downing et al, 2008;Anderson et al, 2009;Finlay et al, 2010), these values should therefore be regarded as maximum burial rates and not necessarily representative of the whole lake. This qualification of organic carbon burial is important for comparing between lakes and especially when assessing the overall importance of lakes in global carbon burial (e.g.…”

“…While spatial heterogeneity in sediment is widely recognised, the estimation of burial rates or lake-wide fluxes of materials such as organic carbon do not often reflect this (e.g. Downing et al, 2008;Anderson, D'Andrea & Fritz, 2009;Finlay et al, 2010). Similarly, the general applicability of existing models used to explain this spatial heterogeneity still needs to be demonstrated, particularly in the case of small lakes.…”

Spatial distribution and sources of organic carbon in the surface sediment of Bosten Lake, China

“…The magnitude of TOC in surface sediment may depend on many factors, including column water productivity, terrestrial inputs of organic materials, properties of sediment, and rate of microbial activity (Burone et al, 2003;Gireeshkumar et al, 2013). Among them, contributions of autochthonous and allochthonous sources have direct impacts on the spatial dis-tribution, which varies largely across regions (Bechtel and Schubert, 2009;Anderson et al, 2009), partly due to differences in lake productivity and morphology (Barnes and Barnes, 1978). In general, lakes with high productivity have more autochthonous TOC, but lakes with low productivity mainly allochthonous TOC (Dean and Gorham, 1998).…”