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| Titel |
Nutrient and carbonate ion change at intermediate depth North West Atlantic: a record from a 15.4ky D. dianthus fossil coral |
| VerfasserIn |
Eleni Anagnostou, Robert Sherrell, Jess Adkins |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053824
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| Zusammenfassung |
| Recovery from ice age conditions during the last deglaciation is known to have occurred
discontinuously, with step-wise increases in sea-level, and uncertain, possibly short-term
reorganizations of circulation in the Atlantic Ocean. We applied recently calibrated P/Ca and
U/Ca proxies (Anagnostou et al., in review) to a fossil D. dianthus coral from the
northwest Atlantic (1800m), U-Th dated to 15.4ky calendar age. This specimen
captured a radiocarbon age reversal, with the biologically younger end of the skeleton
being older in radiocarbon age than the base of the coral (Adkins et al., 1998),
attributed to an abrupt event leading to change in the ventilation age of the ambient
seawater. Our results allow for the first time an estimate of seawater phosphate
concentrations; phosphate increased within one century from concentrations near modern
values for this location (1.1 μmol/kg) to substantially higher concentrations after
the event (1.7 μmol/kg), a relative change consistent with previously determined
gradients of Cd/Ca in the same coral. In addition, our modern calibration of U/Ca
against seawater carbonate ion concentration indicates that [CO32-] decreased by
30% following this event. We conclude that P enriched, CO32- depleted Southern
Source Water (SSW) flooded the coral location at 15.4ky, displacing a mixture
of glacial North Atlantic Intermediate (GNAIW) and SSW. Such an increase was
not observed in a slightly older and deeper coral, suggesting the rapid nature of
the event. Four corals from the same location with preliminary dates matching
Heinrich Event 1 (Â 16.8ky) show similar P/Ca to the post-15.4ky coral, suggesting
that the 15.4ky and Heinrich 1 events share similar intermediate depth water mass
composition.
Adkins et al. (1998). Deep-sea coral evidence for rapid change in ventilation of the deep
North Atlantic 15,400 years ago. Science 280, 725-728.
Anagnostou et al. (in review). Seawater nutrient and carbonate ion concentrations
recorded as P/Ca, Ba/Ca, and U/Ca in the deep-sea coral D. dianthus. Geochim. Cosmochim.
Acta. |
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