Publikationsdatum:
2017-01-20
Beschreibung:
Mesoscale eddies may drive a significant component of cross-shelf transport important in the ecology of shelf
ecosystems and adjacent boundary currents. The Leeuwin Current in the eastern Indian Ocean becomes unstable
in the austral autumn triggering the formation of eddies. We hypothesized that eddy formation represented the
major driver of cross-shelf transport during the autumn. Acoustic Doppler Current Profiler profiles confirmed periodic
offshore movement of 2 Sv of shelf waters into the forming eddy from the shelf, carrying a load of
organic particles (〉0.06 mm). The gap between inflow and outflow then closed, such that the eddy became isolated
from further direct input of shelf waters. Drifter tracks supported an anticyclonic surface flow peaking at
the eddy perimeter and decreasing in velocity at the eddy center. Oxygen and nutrient profiles suggested rapid
remineralization of nitrate mid-depth in the isolated water mass as it rotated, with a total drawdown of oxygen
of 3.6 mol m22 to 350 m. Depletion of oxygen, and release of nitrate, occurred on the timescale of 1 week. We
suggest that N supply and N turnover are rapid in this system, such that nitrate is acting primarily as a regenerated
nutrient rather than as a source of new nitrogen. We hypothesize that sources of eddy particulate C and N
could include particles sourced from coastal primary producers within 500 km such as macrophytes and seagrasses
known to produce copious detritus, which is prone to resuspension and offshore transport.
Repository-Name:
EPIC Alfred Wegener Institut
Materialart:
Article
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isiRev