The influence of salinity on Mg/Ca in planktic foraminifers - evidence from cultures, core-top sediments and complementary δ18O
Allen, Katherine A.
Lea, David W.
Spero, Howard J.
Eggins, Stephen M.
deMenocal, Peter B.
Russell, Ann D.
MetadataShow full item record
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.
Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 121 (2013):196-213, doi:10.1016/j.gca.2013.07.028.
Suggested CitationPreprint: Honisch, Barbel, Allen, Katherine A., Lea, David W., Spero, Howard J., Eggins, Stephen M., Arbuszewski, Jennifer, deMenocal, Peter B., Rosenthal, Yair, Russell, Ann D., Elderfield, Henry, "The influence of salinity on Mg/Ca in planktic foraminifers - evidence from cultures, core-top sediments and complementary δ18O", 2013-06, https://doi.org/10.1016/j.gca.2013.07.028, https://hdl.handle.net/1912/6150
Showing items related by title, author, creator and subject.
Planktic foraminifer tissue and shell d15N from net tows on R/V S.A. Agulhas II cruises VOY016 and VOY019 in the Southern Ocean south of Africa during 2015-2016 Sigman, Daniel M. (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: firstname.lastname@example.org, 2020-03-13)This dataset synthesizes net-tow data (foraminifera and zooplankton measurements) with tow-depth seawater measurements (physical and chemical properties) and surface measurements of bulk suspended particulate organic ...
Sigman, Daniel (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: email@example.com, 2020-01-10)Planktic foraminifer shell d15N from net tows in the Sargasso Sea (off Bermuda) in the western subtropical North Atlantic. Net tow samples from 0-200 m at BATS (31°40’N, 64°10’W) and Hydro Station S (32°10’N, 64°34’W), ...
Sigman, Daniel (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: firstname.lastname@example.org, 2020-01-10)Planktic foraminifer tissue d15N from net tows in the Sargasso Sea (off Bermuda) in the western subtropical North Atlantic. Net tow samples from 0-200 m at BATS (31°40’N, 64°10’W) and Hydro Station S (32°10’N, 64°34’W), ...