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Sr/Ca proxy sea-surface temperature reconstructions from modern and holocene Montastraea faveolata specimens from the Dry Tortugas National Park

Journal of Coastal Research

By:
and
DOI: 10.2112/SI63-003.1

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Abstract

Sr/Ca ratios from skeletal samples from two Montastraea faveolata corals (one modern, one Holocene, ~6 Ka) from the Dry Tortugas National Park were measured as a proxy for sea-surface temperature (SST). We sampled coral specimens with a computer-driven triaxial micromilling machine, which yielded an average of 15 homogenous samples per annual growth increment. We regressed Sr/Ca values from resulting powdered samples against a local SST record to obtain a calibration equation of Sr/Ca = -0.0392 SST + 10.205, R = -0.97. The resulting calibration was used to generate a 47-year modern (1961-2008) and a 7-year Holocene (~6 Ka) Sr/Ca subannually resolved proxy record of SST. The modern M. faveolata yields well-defined annual Sr/Ca cycles ranging in amplitude from ~0.3 and 0.5 mmol/mol. The amplitude of ~0.3 to 0.5 mmol/mol equates to a 10-15°C seasonal SST amplitude, which is consistent with available local instrumental records. Summer maxima proxy SSTs calculated from the modern coral Sr/ Ca tend to be fairly stable: most SST maxima from 1961–2008 are 29°C ± 1°C. In contrast, winter minimum SST calculated in the 47-year modern time-series are highly variable, with a cool interval in the early to mid-1970s. The Holocene (~6 Ka) Montastraea faveolata coral also yields distinct annual Sr/Ca cycles with amplitudes ranging from ~0.3 to 0.6 mmol/mol. Absolute Sr/Ca values and thus resulting SST estimates over the ~7-year long record are similar to those from the modern coral. We conclude that Sr/Ca from Montastraea faveolata has high potential for developing subannually resolved Holocene SST records.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Sr/Ca proxy sea-surface temperature reconstructions from modern and holocene Montastraea faveolata specimens from the Dry Tortugas National Park
Series title:
Journal of Coastal Research
DOI:
10.2112/SI63-003.1
Year Published:
2013
Language:
English
Publisher:
Coastal Education and Research Foundation
Contributing office(s):
St. Petersburg Coastal and Marine Science Center
Description:
12 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Coastal Research
First page:
20
Last page:
31
Country:
United States
City:
Florida
Other Geospatial:
Dry Tortugas