Organic carbon flux and particulate organic matter composition in Arctic valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden

　　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 M and 73 M, 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).
Table 5. Estimated organic carbon flux from Svalbard and its comparison with other pan-Arctic glacier systems（Zhu et al., 2016）
　　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 t/yr) and DOC (0.02 ± 0.01 × 106 t/yr) 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.
 
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