Penultimate deglacial warming across the Mediterranean Sea revealed by clumped isotopes in foraminifera

• Published in: Scientific Reports
• Main Authors: Rodriguez-Sanz, Laura, Bernasconi, Stefano M., Marino, Gianluca, Heslop, David, Muller, I A, Fernandez, A, Grant, Katharine, Rohling, Eelco
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group
• Subjects: North Atlantic
• Online Access: http://hdl.handle.net/1885/245846; https://doi.org/10.1038/s41598-017-16528-6; https://openresearch-repository.anu.edu.au/bitstream/1885/245846/3/01_Rodriguez%2bSanz_Penultimate_deglacial_warming_2017.pdf.jpg

The variability of seawater temperature through time is a critical measure of climate change, yet its reconstruction remains problematic in many regions. Mg/Ca and oxygen isotope (δ^18 Oc) measurements in foraminiferal carbonate shells can be combined to reconstruct seawater temperature and δ^18 O (δ^18 OSW). The latter is a measure of changes in local hydrology (e.g., precipitation/evaporation, freshwater inputs) and global ice volume. But diagenetic processes may affect foraminiferal Mg/Ca. This restricts its potential in many places, including the Mediterranean Sea, a strategic region for deciphering global climate and sea-level changes. High alkalinity/salinity conditions especially bias Mg/Ca temperatures in the eastern Mediterranean (eMed). Here we advance the understanding of both western Mediterranean (wMed) and eMed hydrographic variability through the penultimate glacial termination (TII) and last interglacial, by applying the clumped isotope (Δ47) paleothermometer to planktic foraminifera with a novel data-processing approach. Results suggest that North Atlantic cooling during Heinrich stadial 11 (HS11) affected surface-water temperatures much more in the wMed (during winter/spring) than in the eMed (during summer). The method’s paired Δ47 and δ^18 Oc data also portray δ^18 OSW. These records reveal a clear HS11 freshwater signal, which attenuated toward the eMed, and also that last interglacial surface warming in the eMed was strongly amplified by water-column stratification during the deposition of the organic-rich (sapropel) interval known as S5. Tis study was supported by Swiss National Science Foundation projects SNSF 200020_160046 and IZK0Z2_160377, ETH project No. ETH-33 14-1, ANZIC-IODP project ARIES30735 (K.M.G. & L.R.-S.), and Australian Research Council Australian Laureate Fellowship FL120100050 (E.J.R).