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| Titel |
Dense Overflow from an Arctic Fjord: Mean Seasonal Cycle, Variability and Wind Influence |
| VerfasserIn |
F. Geyer, I. Fer, T. Eldevik |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029752
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| Zusammenfassung |
| Storfjorden, an Arctic fjord in Svalbard Archipelago, is separated by a submarine sill from
the adjacent shelf areas and produces one of the densest water masses in the Barents Sea. The
cold and dense brine-enriched shelf water is produced through ice formation in an
annually recurrent polynya in Storfjorden and overflows across the sill. We present
current profiles and bottom temperature measurements from the Storfjorden sill
from 2003 to 2007 and study the interannual variability of the overflow and the
influence of atmospheric forcing. The data set is the longest time series collected at this
site. The mean structure of the overflow averaged over four seasons shows that the
overflow is initially strong with high volume transports early in the overflow season,
about 50 m thick and bottom-enhanced, and then gradually diminishes, becoming
increasingly intermittent during the last third of the overflow season. The annual average
overflow flux across the sill is about 0.03 Sv (1 Sv -¡ 106 m3 s-1). Overflow was
observed 55% of a total record length of 958 days and cross-sill flow averaged in
the bottom 20 m was greater than 10 cms-1 for 49% of the overflow duration.
The overflow strength increased with decreasing near-bottom temperatures. The
comparison of four consecutive overflow seasons reveals annual variability within 0.01 Sv
whereas the variability within one season can be as large as 0.05 Sv. In spite of the
relatively constant annual overflow flux, the onset of the overflow can vary by as much
as 50 days. Variability on the scale of 1-2 weeks is strongly connected to wind
forcing, indicated by the significant coherence between the rotary components of
the current at the Storfjorden sill and wind measurements at two meteorological
stations on Edgeøya and Hopen Island. The physical connection is the surface Ekman
transport. Surface Ekman transport and the ice conditions in the Barents sea also
influence seasonal intra-development and interannual variability of the overflow. |
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