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On the Seasonal Signal of the Filchner Overflow, Weddell Sea, Antarctica

Darelius, E.; Strand, K. O.; Østerhus, S.; Gammeslrød, T.; Arthun, M.; Fer, I.. 2014 On the Seasonal Signal of the Filchner Overflow, Weddell Sea, Antarctica. Journal of Physical Oceanography, 44 (4). 1230-1243. 10.1175/JPO-D-13-0180.1

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Abstract/Summary

The cold ice shelf water (ISW) that formed below the Filchner–Ronne Ice Shelf in the southwestern Weddell Sea, Antarctica, escapes the ice shelf cavity through the Filchner Depression and spills over its sill at a rate of 1.6 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1), thus contributing significantly to the production of Weddell Sea Bottom Water. Here, the authors examine all available observational data from the region—including five year-long time series of mooring data from the Filchner sill—to examine the seasonal variability of the outflow. The temperature of the ISW outflow is found to vary seasonally by 0.07°C with a maximum in April. The accompanying signal in salinity causes a seasonal signal in density of 0.03–0.04 kg m−3, potentially changing the penetration depth of the ISW plume by more than 500 m. Contrary to recent modeling, the observations show no seasonal variability in outflow velocity. The seasonality observed at the sill is, at least partly, due to the admixture of high-salinity shelf water from the Berkner Bank. Observations and numerical modeling suggest, however, seasonal signals in the circulation upstream (i.e., in the ice shelf cavity and in the Filchner Depression) that—although processes and linkages are unclear—are likely to contribute to the seasonal signal observed at the sill. In the plume region downstream of the sill, the source variability is apparent only within the very densest portions of the ISW plume. In the more diluted part of the plume, the source variability is overcome by the seasonality in the properties of the water entrained at the shelf break. This will have implications for the properties of the generated bottom waters.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1175/JPO-D-13-0180.1
Programmes: BAS Programmes > Polar Science for Planet Earth (2009 - ) > Polar Oceans
ISSN: 0022-3670
Date made live: 12 May 2014 10:44 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/507212

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