Publication Date:
2024-02-21
Description:
〈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 (>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〉
Description:
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 (>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〉
Description:
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〉
Description:
Israel Science Foundation
http://dx.doi.org/10.13039/501100003977
Description:
Minerva PhD Fellowship Stipend
Description:
Advance School for Environmental Studies
Description:
https://doi.org/10.1594/PANGAEA.959629
Description:
https://doi.org/10.17617/3.EXFQC2
Keywords:
ddc:551.9
;
Gulf of Aqaba
;
Planktic Foraminifera shells
;
Mg/Ca
;
sea surface temperature reconstructions
Language:
English
Type:
doc-type:article
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