HomeHome

The Influence of Salinity on Mg/Ca in Planktic Foraminifers – Evidence from Cultures, Core-top Sediments and Complementary δ18O

Baerbel Hoenisch; Katherine Ann Allen; David W. Lea; Howard J. Spero; Stephen M. Eggins; Jennifer Arbuszewski; Peter B. deMenocal; Yair Rosenthal; Ann D. Russell; Henry Elderfield

Title:
The Influence of Salinity on Mg/Ca in Planktic Foraminifers – Evidence from Cultures, Core-top Sediments and Complementary δ18O
Author(s):
Hoenisch, Baerbel
Allen, Katherine Ann
Lea, David W.
Spero, Howard J.
Eggins, Stephen M.
Arbuszewski, Jennifer
deMenocal, Peter B.
Rosenthal, Yair
Russell, Ann D.
Elderfield, Henry
Date:
Type:
Articles
Department(s):
Lamont-Doherty Earth Observatory
Earth and Environmental Sciences
Volume:
121
Persistent URL:
Book/Journal Title:
Geochimica et Cosmochimica Acta
Publisher:
Elsevier
Abstract:
The Mg/Ca ratio in foraminiferal calcite is one of the principal proxies used for paleoceanographic temperature reconstructions, but recent core-top sediment observations suggest that salinity may exert a significant secondary control on planktic foraminifers. This study compiles new and published laboratory culture experiment data from the planktic foraminifers Orbulina universa, Globigerinoides sacculifer and Globigerinoides ruber, in which salinity was varied but temperature, pH and light were held constant. Combining new data with results from previous culture studies yields a Mg/Ca-sensitivity to salinity of 4.4 ± 2.3%, 4.7 ± 1.2%, and 3.3 ± 1.7% per salinity unit (95% confidence), respectively, for the three foraminifer species studied here. Comparison of these sensitivities with core-top data suggests that the much larger sensitivity (27 ± 4% per salinity unit) derived from Atlantic core-top sediments in previous studies is not a direct effect of salinity. Rather, we suggest that the dissolution correction often applied to Mg/Ca data can lead to significant overestimation of temperatures. We are able to reconcile culture calibrations with core-top observations by combining evidence for seasonal occurrence and latitude-specific habitat depth preferences with corresponding variations in physico-chemical environmental parameters. Although both Mg/Ca and δ18O yield temperature estimates that fall within the bounds of hydrographic observations, discrepancies between the two proxies highlight unresolved challenges with the use of paired Mg/Ca and δ18O analyses to reconstruct paleo-salinity patterns across ocean basins. The first step towards resolving these challenges requires a better spatially and seasonally resolved δ18Osw archive than is currently available. Nonetheless, site-specific reconstructions of salinity change through time may be valid.
Subject(s):
Paleoclimatology
Chemical oceanography
Biogeochemistry
Publisher DOI:
https://doi.org/10.1016/j.gca.2013.07.028
Item views
319
Metadata:
text | xml
Suggested Citation:
Baerbel Hoenisch, Katherine Ann Allen, David W. Lea, Howard J. Spero, Stephen M. Eggins, Jennifer Arbuszewski, Peter B. deMenocal, Yair Rosenthal, Ann D. Russell, Henry Elderfield, , The Influence of Salinity on Mg/Ca in Planktic Foraminifers – Evidence from Cultures, Core-top Sediments and Complementary δ18O, Columbia University Academic Commons, .

Columbia University Libraries | Policies | FAQ