20th Century δ 18 O Seawater and Salinity Variations Reconstructed From Paired δ 18 O and Sr/Ca Measurements of a La Reunion Coral

Pfeiffer, Miriam, Reuning, L., Zinke, J., Garbe-Schönberg, Dieter, Leupold, M. and Dullo, Wolf-Christian (2019) 20th Century δ 18 O Seawater and Salinity Variations Reconstructed From Paired δ 18 O and Sr/Ca Measurements of a La Reunion Coral Paleoceanography and Paleoclimatology, 34 . pp. 2183-2200. DOI 10.1029/2019PA003770.

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Supplementary data:

Abstract

Sea surface salinity (SSS) is an important variable in the global ocean circulation. However, decadal to interdecadal changes in SSS are not well understood due to the lack of instrumental data. Here we reconstruct SSS from a paired, bimonthly resolved coral δ18O and Sr/Ca record from La Reunion Island that extends from 1913 to 1995. Coral Sr/Ca correlates with regional sea surface temperature (SST) back to 1966, when instrumental coverage is good, while coral δ18O does not. The slope of the monthly (annual mean) coral Sr/Ca-SST regression is −0.040 mmol/mol per 1 °C (−0.068 mmol/mol per 1 °C) consistent with published estimates of the Sr/Ca-SST relationship. Coral Sr/Ca suggest a warming of 0.39 °C since 1913. δ18O seawater is calculated by subtracting the temperature component from measured coral δ18O, using coral Sr/Ca as well as historical SST products. The derived δ18O seawater reconstructions are correlated (r > 0.6), and all show a significant shift in the midtwentieth century (−0.17‰ to −0.19‰), indicating a freshening of SSS by 0.7 psu. However, the timing of this shift depends on the temperature component and varies from 1947 (δ18O seawater calculated with historical SST) to the late 1950s (δ18O seawater calculated with coral Sr/Ca). Coral Sr/Ca shows warm temperature anomalies in the mid-1950s, while historical SST products show warm anomalies from 1940 to 1945 followed by cooling in the 1950s, a pattern typical for the World War II bias. This suggests that historical SST may bias reconstructions of δ18O seawater and SSS from corals.

Document Type: Article
Keywords: coral Sr/Ca, delta 18O seawater, Indian Ocean, Porites
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Kiel University
Refereed: Yes
DOI etc.: 10.1029/2019PA003770
ISSN: 2572-4517
Related URLs:
Projects: TESTREEF
Date Deposited: 10 Jan 2020 11:59
Last Modified: 23 Jan 2020 07:52
URI: http://eprints.uni-kiel.de/id/eprint/48718

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