Abstract
Caribbean sea surface temperatures (SSTs) have increased at a rate of
0.2°C per decade since 1971, a rate double that of the mean global
change. Recent investigations of the coral Siderastrea siderea
on the Belize Mesoamerican Barrier Reef System (MBRS) have demonstrated
that warming over the last 30 years has had a detrimental impact on
calcification. Instrumental temperature records in this region are
sparse, making it necessary to reconstruct longer SST records indirectly
through geochemical temperature proxies. Here we investigate the
skeletal Sr/Ca and Li/Mg ratios of S. siderea from two distinct reef zones (forereef and backreef) of the MBRS. Our field calibrations of S. siderea
show that Li/Mg and Sr/Ca ratios are well correlated with temperature,
although both ratios are 3 times more sensitive to temperature change in
the forereef than in the backreef. These differences suggest that a
secondary parameter also influences these SST proxies, highlighting the
importance for site- and species-specific SST calibrations. Application
of these paleothermometers to downcore samples reveals highly uncertain
reconstructed temperatures in backreef coral, but well-matched
reconstructed temperatures in forereef coral, both between Sr/Ca-SSTs
and Li/Mg-SSTs, and in comparison to the Hadley Centre Sea Ice and Sea
Surface Temperature record. Reconstructions generated from a combined
Sr/Ca and Li/Mg multiproxy calibration improve the precision of these
SST reconstructions. This result confirms that there are circumstances
in which both Li/Mg and Sr/Ca are reliable as stand-alone and combined
proxies of sea surface temperature. However, the results also highlight
that high-precision, site-specific calibrations remain critical for
reconstructing accurate SSTs from coral-based elemental proxies.
Original language | English |
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Pages (from-to) | 1315-1329 |
Number of pages | 15 |
Journal | Paleoceanography |
Volume | 31 |
Issue number | 10 |
Early online date | 5 Oct 2016 |
DOIs | |
Publication status | Published - 11 Nov 2016 |
Keywords
- Li/Mg
- Sr/Ca
- SST proxies
- Siderastrea siderea