期刊
GLOBAL BIOGEOCHEMICAL CYCLES
卷 34, 期 3, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2019GB006446
关键词
subglacial; organic matter; Antarctica; ice-shelf-cavity
资金
- National Science Foundation from the Division of Polar Programs [0838933, 0838896, 0838941, 0839142, 0839059, 0838885, 0838855, 0838763, 0839107, 0838947, 0838854, 0838764, 1142123]
- NSF-IGERT [0654336]
- Montana Space Grant Consortium
- NSF-CDEBI
- American Association of University Women, Montana Institute on Ecosystems
- Michigan Technological University
- NSF-GRFP
- Ser Cymru National Research Network for Low Carbon, Energy
- Welsh Government
- Higher Education Funding Council for Wales
- Directorate For Geosciences [0838947] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Polar Programs [0838854] Funding Source: National Science Foundation
- Directorate For Geosciences
- Office of Polar Programs (OPP) [0838763, 0839059, 0839142, 0839107, 0838764, 0838885, 1142123] Funding Source: National Science Foundation
- Directorate For Geosciences
- Office of Polar Programs (OPP) [0838896, 0838855] Funding Source: National Science Foundation
- Division Of Polar Programs
- Directorate For Geosciences [0838941, 838933] Funding Source: National Science Foundation
- Office of Polar Programs (OPP) [0838947] Funding Source: National Science Foundation
Although subglacial aquatic environments are widespread beneath the Antarctic ice sheet, subglacial biogeochemistry is not well understood, and the contribution of subglacial water to coastal ocean carbon and nutrient cycling remains poorly constrained. The Whillans Subglacial Lake (SLW) ecosystem is upstream from West Antarctica's Gould-Siple Coast 800 m beneath the surface of the Whillans Ice Stream. SLW hosts an active microbial ecosystem and is part of an active hydrological system that drains into the marine cavity beneath the adjacent Ross Ice Shelf. Here we examine sources and sinks for organic matter in the lake and estimate the freshwater carbon and nutrient delivery from discharges into the coastal embayment. Fluorescence-based characterization of dissolved organic matter revealed microbially driven differences between sediment pore waters and lake water, with an increasing contribution from relict humic-like dissolved organic matter with sediment depth. Mass balance calculations indicated that the pool of dissolved organic carbon in the SLW water column could be produced in 4.8 to 11.9 yr, which is a time frame similar to that of the lakes' fill-drain cycle. Based on these estimates, subglacial lake water discharged at the Siple Coast could supply an average of 5,400% more than the heterotrophic carbon demand within Siple Coast embayments (6.5% for the entire Ross Ice Shelf cavity). Our results suggest that subglacial discharge represents a heretofore unappreciated source of microbially processed dissolved organic carbon and other nutrients to the Southern Ocean. Plain Language Summary Antarctica's thick ice sheets cover a continent rich with liquid water. These subglacial aquatic environments are home to microbial ecosystems that process organic matter and nutrients important for all life. At the same time, subglacial water in Antarctica actively flows between basins and from subglacial basins to the edge of the continent where it mixes with seawater in coastal areas covered by ice shelves. The waters under these ice shelves are cold, dark, and contain low concentrations of organic carbon and nutrients. We used data from Whillans Subglacial Lake, which lies 800 m beneath the ice of West Antarctica, to understand the sources, sinks, and accumulation of organic matter in Antarctic subglacial aquatic environments. We then combined data from the same lake with data on subglacial hydrology in the region to determine whether inputs of subglacial organic matter and nutrients could be important in supporting life in the dark waters beneath the adjacent ice shelf. We found that the input of fresh water from the Antarctic continent to the surrounding ocean can meet the microbial demand for organic carbon and nutrients under the ice shelf. This work has implications for our understanding of Antarctica's influence on biology in the Southern Ocean.
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