期刊
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
卷 124, 期 4, 页码 840-856出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2018JG004895
关键词
-
资金
- U.S. National Science Foundation [ARC-0909514, ARC-0909538]
Glacial runoff exports large amounts of carbon (C) to the oceans, but major uncertainty remains regarding sources, seasonality, and magnitude. We apportioned C exported by five rivers from glacial and periglacial sources in northwest Greenland by monitoring discharge, water sources (delta O-18), concentration and composition of dissolved organic carbon (DOC), and ages (C-14) of DOC and particulate organic C over three summers (2010-2012). We found that particulate organic C (F = 1.0366-0.2506) was generally older than DOC in glacial sourced rivers and likely sourced from the physical erosion of aged C pools. Most exported DOC showed strong seasonal variations in sources and discharge. In summer, mean DOC ages ranged from modern to 4,750 cal years BP (F = 1.0022-0.6291); however, the annual C flux from glacially sourced rivers was dominated by young, plant-derived DOC (F = 0.9667-1.002) exported during the spring freshet. The most aged DOC (F = 0.6891-0.8297) was exported in middle to late summer at lower concentrations and was glacial in origin. Scaled to the whole of Greenland using model-estimated runoff, we estimate a total riverine DOC flux of 0.29% to 0.45% +/- 20% Tg C/year. Our flux results indicate that the highest C fluxes occur during the time of year when the majority of C is modern in age. However, higher melt rates from the Greenland ice sheet and longer growing seasons could result in increasing amounts of ancient C from the Greenland ice sheet and from the periglacial landscape to the ocean.
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