In:
Biogeosciences, Copernicus GmbH, Vol. 18, No. 2 ( 2021-01-19), p. 423-439
Abstract:
Abstract. Over the last decades, sea surface temperature (SST) reconstructions based
on the Mg∕Ca of foraminiferal calcite have frequently been used in
combination with the δ18O signal from the same material to
provide estimates of the δ18O of water (δ18Ow), a proxy for global ice volume and sea surface salinity
(SSS). However, because of error propagation from one step to the next,
better calibrations are required to increase the accuracy and robustness of
existing isotope and element to temperature proxy relationships. Towards
that goal, we determined Mg∕Ca, Sr∕Ca and the oxygen isotopic composition of
Trilobatus sacculifer (previously referenced as Globigerinoides sacculifer) collected from surface waters (0–10 m) along a
north–south transect in the eastern basin of the tropical and subtropical
Atlantic Ocean. We established a new paleotemperature calibration based on
Mg∕Ca and on the combination of Mg∕Ca and Sr∕Ca. Subsequently, a
sensitivity analysis was performed in which one, two or three different
equations were considered. Results indicate that foraminiferal Mg∕Ca allows
for an accurate reconstruction of surface water temperature. Combining
equations, δ18Ow can be reconstructed with a precision of about
± 0.5 ‰. However, the best possible salinity
reconstruction based on locally calibrated equations only allowed for a
reconstruction with an uncertainty of ± 2.49. This was confirmed by a
Monte Carlo simulation, applied to test successive reconstructions in an
“ideal case” in which explanatory variables are known. This simulation shows
that from a purely statistical point of view, successive reconstructions
involving Mg∕Ca and δ18Oc preclude salinity reconstructions with
a precision better than ± 1.69 and hardly better than ± 2.65
due to error propagation. Nevertheless, a direct linear fit to reconstruct
salinity based on the same measured variables (Mg∕Ca and δ18Oc)
was established. This direct reconstruction of salinity led to a much
better estimation of salinity (± 0.26) than the successive
reconstructions.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-18-423-2021
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2021
detail.hit.zdb_id:
2158181-2
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