High Atlantic native Goodkin

Core/Site name:

BB01

Country/Region:

Bermuda/Atlantic

Elevation:

-16

Archive:

corals

Species:

Diploria labyrinthiformis

Proxy measurement:

Sr/Ca, d18O, average coral growth over 3 years

Sampling resolution:

annual

Climate sensitivity:

SST, d18Oseawater (=salinity)

Dating resolution:

Annual bands, 1-yr resolution

Dating information:

Absolute

Startyear:

1781 AD

Endyear:

1998 AD

All uncertainties:

(3) Sr/Ca = ±0.0244 mmol/mol. d18O = ± 0.11 (5) growth corrected SST ~±0.4°C

Description:

We use geochemical and isotope measurements on a 225-year old brain coral (Diploria labyrinthiformis)from the south shore of Bermuda (64!W, 32!N) to construct a record of decadal-to-centennial-scale climatevariability. The coral was collected alive, and annual density bands visible in X radiographs delineate cold andwarm seasons allowing for precise dating. Coral skeletons incorporate strontium (Sr) and calcium (Ca) inrelative proportions inversely to the sea surface temperature (SST) in which the skeleton is secreted. Previousstudies on this and other coral colonies from this region document the ability to reconstruct mean annual andwintertime SST using Sr/Ca measurements (Goodkin et al., 2007, 2005). The coral-based records of SST for thepast 2 centuries show abrupt shifts at both decadal and centennial timescales and suggest that SST at the end ofthe Little Ice Age (between 1840 and 1860) was 1.5! ± 0.4!C colder than today (1990s). Coral-reconstructedSST has a greater magnitude change than does a gridded instrumental SST record from this region. This mayresult from several physical processes including high rates of mesoscale eddy propagation in this region. Oxygenisotope values (d18O) of the coral skeleton reflect changes in both temperature and the d18O of seawater (dOw),where dOw is proportional to sea surface salinity (SSS). We show in this study that mean annual and wintertimed18O of the carbonate (dOc) are correlated to both SST and SSS, but a robust, quantitative measure of SSS is notfound with present calibration data. In combination, however, the Sr/Ca and dOc qualitatively reconstruct lowersalinities at the end of the Little Ice Age relative to modern day. Temperature changes agree with other recordsfrom the Bermuda region. Radiative and atmospheric forcing may explain some of the SST variability, but thescales of implied changes in SST and SSS indicate large-scale ocean circulation impacts as well.

Data entered by name:

Delia Oppo

Data entered by email:

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Main reference(s):

Goodkin, N. F., K. A. Hughen, W. B. Curry, S. C. Doney, and D. R. Ostermann (2008), Sea surface temperature and salinity variability at Bermuda during the end of the Little Ice Age, Paleoceanography, 23, PA3203, doi:10.1029/2007PA001532.

Link to reference 1:

http://www.agu.org/pubs/crossref/2008/2007PA001532.shtml

Data storage link 1:

http://hurricane.ncdc.noaa.gov/pls/paleox/f?p=519:1:8477300981555373::::P1_STUDY_ID:6115

Current dating method:

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Annual snow acc rate:

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Category: Ocean2k