Deglacial Meltwater Pulse Recorded in Last Interglacial Mollusk Shells from Bermuda

Iceberg scours as far south as the Florida Strait and the presence of ice rafted debris in sediments from the Bermuda Rise indicate that during the last glacial phase icebergs traveled quite far south during episodes of excessive iceberg discharge from the Laurentide Ice Sheet (Heinrich Events). We present evidence that the effects of these events extended southward into the subtropics during the previous deglaciation (Termination-II), potentially aligned with Heinrich Event 11, and that meltwater reached Bermuda. Temperatures 10° C colder and seawater δ18O values 2 ‰ more negative than modern are derived from Last Interglacial Cittarium pica shells from Grape Bay, Bermuda using the clumped isotope paleothermometer. In contrast, Last Interglacial shells from Rocky Bay record temperatures only slightly colder and seawater δ18O values similar to modern, potentially representing more typical Last Interglacial conditions in Bermuda outside of a meltwater event. The cold ocean conditions observed illustrate extreme sensitivity of Bermudian climate to rapid climate and ocean circulation changes. They also provide further evidence for routine meltwater transport in the North Atlantic to near-equatorial latitudes during deglaciation.