Abstract
Abstract. In the face of ongoing global warming and glacier retreat, the composition and flux of organic matter in glacier–fjord systems are key variables for updating the carbon cycle and budget, whereas the role of Arctic valley glaciers seems unimportant when compared with the huge Greenland Ice Sheet. Our field observations of the glacier-fed Bayelva River, Svalbard, and the adjacent Kongsfjorden allowed us to determine the compositions of particulate organic matter from glacier to fjord and also to estimate the flux of organic carbon, both for the river and for Svalbard in general. Particulate organic carbon (POC) and dissolved organic carbon (DOC) in the Bayelva River averaged 56 and 73 µM, respectively, in August, 2012. Amino acids (AAs) and phytoplankton carbon accounted for ∼ 10 % of the bulk POC in the Bayelva River, while AAs represented > 90 % of particulate nitrogen (PN) in fjord surface water, suggesting the strong in situ assimilation of organic matter. Bacteria accounted for 13 and 19 % of the POC in the Bayelva River and the Kongsfjorden, respectively, while values for PN were much higher (i.e., 36 % in Kongsfjorden). The total discharge from the Bayelva River in 2012 was 29 × 106 m3. Furthermore, we calculated the annual POC, DOC, and PN fluxes for the river as 20 ± 1.6 tons, 25 ± 5.6 tons, and 4.7 ± 0.75 tons, respectively. Using the POC content and DOC concentration data, we then estimated the annual POC and DOC fluxes for Svalbard glaciers. Although the estimated POC (0.056 ± 0.02 × 106 tons year−1) and DOC (0.02 ± 0.01 × 106 tons year−1) fluxes of Svalbard glaciers are small in amount, its discharge-weighted flux of DOC was over twice higher than other pan-Arctic glacier systems, suggesting its important role as a terrestrial DOC source.
Highlights
The composition and flux of organic carbon are two key factors in the study of global climate change and material cycling
While trace amounts of several pigments were measured in the river, chlorophyll a (Chl a) was the dominant pigment, with a mean concentration at NVE station of 0.26 μg L−1 (Table 1)
In 2012, the annual water discharge of the Bayelva River was 29 × 106 m3 according to the hourly-averaged instrumental record
Summary
The composition and flux of organic carbon are two key factors in the study of global climate change and material cycling. Current retreat of Arctic glaciers, as a consequence of global warming, contributes to sea-level rise and serves to increase the input of terrigenous material to the ocean. This in turn impacts the composition of oceanic organic carbon and modifies the carbon flux, with potential ramifications for global climate variability and material cycles. Despite the depleted nature of 14C values of glacial DOM, which results in old apparent 14C ages, significant proteinaceous signals (Dubnick et al, 2010) and a high labile proportion (23–66 %; Hood et al, 2009) were identified in the glacier meltwater DOM.
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