TY  - JOUR
A1  - Levy, N.
A1  - Torfstein, A.
A1  - Schiebel, R.
A1  - Chernihovsky, N.
A1  - Jochum, K. P.
A1  - Weis, U.
A1  - Stoll, B.
A1  - Haug, G. H.
T1  - Temperature Calibration of Elevated Mg/Ca in Planktic Foraminifera Shells From the Hypersaline Gulf of Aqaba
Y1  - 2023-07-10
VL  - 24
IS  - 7
SP  - 
EP  - 
JF  - Geochemistry, Geophysics, Geosystems
DO  - 10.1029/2022GC010742
PB  - 
N2  - <title xmlns:mml="http://www.w3.org/1998/Math/MathML">Abstract</title><p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en">The Mg/Ca of marine calcareous Planktic Foraminifera (PF) shells is commonly used for sea surface temperature reconstructions. However, compared to open marine environments, hypersaline (&gt;40) oligotrophic seas have been shown to accommodate PF with higher Mg/Ca and divergent temperature to Mg/Ca relationships. To investigate influencing factors of PF Mg uptake in hypersaline regions, we measured the Mg/Ca of two flux‐dominating PF species, <italic>Globigerinoides ruber albus</italic> and <italic>Turborotalita clarkei</italic>, derived from a monthly resolved time series of sediment traps in the Gulf of Aqaba, northern Red Sea as well as the corresponding temperature, salinity, and <italic>p</italic>H values. The PF exhibit elevated Mg/Ca which cannot be explained by post‐deposition or interstitial sediment diagenetic processes. <italic>G. ruber albus</italic> displays Mg/Ca trends that strongly follow seasonal mixed layer temperature changes. Conversely, <italic>T</italic>. <italic>clarkei</italic> Mg/Ca trends do not follow temperature but rather show significant Mg/Ca enrichment following mixing of the surface water column. We present a framework for incorporating elevated Mg/Ca into global Mg/Ca‐T calibrations for <italic>G</italic>. <italic>ruber albus</italic> and present a new Mg/Ca‐T calibration suitable for hypersaline marine environments.</p>
N2  - Plain Language Summary: Past seawater temperature is reconstructed from the magnesium‐to‐calcium ratio (Mg/Ca) in the calcareous shells of a group of marine microplankton called foraminifera. Two foraminifer species, <italic>Globigerinoides ruber albus</italic> and <italic>Turborotalita clarkei</italic>, are abundant in the Gulf of Aqaba, northern Red Sea, at year‐round high temperatures and salinities. The shells of these foraminifera have elevated Mg/Ca relative to other marine regions, and here, we explore the factors causing this. The Mg/Ca values of both <italic>G</italic>. <italic>ruber albus</italic> and <italic>T</italic>. <italic>clarkei</italic> reflect the environmental conditions of the water column. For <italic>G</italic>. <italic>ruber albus</italic>, temperature and salinity appear to be factors responsible for the Mg/Ca trends and elevated values. We incorporate the new Mg/Ca data for <italic>G</italic>. <italic>ruber albus</italic> to calibrate elevated Mg/Ca with temperature for high‐salinity (&gt;40) marine environments. The Mg/Ca of the deeper dwelling <italic>T</italic>. <italic>clarkei</italic> show higher ratios following deep mixing of the surface water column and may indicate annually recurring phytoplankton blooms caused by nutrient input into the sunlit ocean surface.</p>
N2  - Key Points: <list list-type="bullet"> <list-item> <p xml:lang="en">A new Mg/Ca temperature calibration for high salinity environments is presented for <italic>Globigerinoides ruber albus</italic></p></list-item> <list-item> <p xml:lang="en">A framework for incorporating high salinity environments into global Mg/Ca‐T calibrations is provided</p></list-item> <list-item> <p xml:lang="en">Enhanced Mg/Ca in subsurface dwelling <italic>Turborotalita clarkei</italic> may indicate seasonal deep mixing of the upper water column</p></list-item> </list> </p>
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11447
ER  -