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| Titel |
Annual and eddy-induced variability of particle fluxes in the Mozambique Channel (SW Indian Ocean): Implications for (temperature) proxy reconstructions |
| VerfasserIn |
Ulrike Fallet, Jenny Ullgren, Isla Castañeda, Hendrik van Aken, Stefan Schouten, Geert-Jan Brummer, Herman Ridderinkhof |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039537
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| Zusammenfassung |
| The subtropical Mozambique Channel in the SW Indian Ocean displays a pronounced annual
sea surface temperature (SST) cycle ranging from 25 ºC to 30 ºC. This annual cycle is also
revealed in the remote sensing parameters surface-mixed-layer depth (SML depth),
chlorophyll a, and in surface water nutrient concentrations. Superimposed on this annual
cycle we find a ~70 day current cycle caused by the migration of warm, anticyclonic eddies
with surface velocities that frequently exceed 1.5 m/s. This ~70 day eddy cycle is especially
pronounced in SML depth, surface water nutrient and chlorophyll a concentration and less so
in SST. To assess the influence of both annual and eddy cycles on the sedimentary
depositional signal, we compare particle fluxes and proxy parameters from a 2.5
year sediment trap deployment with (sub-) surface current velocities and remote
sensing SST. We find that responses to the annual cycle propagate sequentially at lags
of three to six weeks to the deep channel sediment. However, only about 50 %
of the variance in e.g. opaline silica, δ15N and foraminiferal δ18O and Mg/Ca of
surface dwelling G. ruber and G. trilobus is related to the annual cycle with up to 30
% of the remaining signal demonstrating a clear ~70 day eddy periodicity. Both
the Branched and Isoprenoid Tetraether (BIT) Index and δ13Corg as indicators for
marine versus soil organic matter input correlate well with eddy migration through
the channel at an r2 of 0.55. We also observed a good correlation at an r2 of ~0.5
between (sub-) surface currents and the organic matter temperature proxy TEX86. By
finding a strong ~70 day eddy periodicity in a number of particle fluxes at the 2.5 km
deep ocean floor we demonstrate that eddies in the Mozambique Channel regularly
advect particles and transport them over long distances thereby potentially biasing
organic matter (temperature) proxy reconstructions. Foraminiferal temperature
proxies exhibit a smaller bias due to relatively fast sinking rates that significantly
shorten their transport time and distance as opposed to organic and lithogenic matter. |
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