Meltwater pulse recorded in last interglacial mollusk shells from Bermuda

• Published in: Paleoceanography
• Main Authors: Winkelstern, Ian Z., Rowe, Mark P., Lohmann, Kyger C., Defliese, William F., Petersen, Sierra V., Brewer, Aaron W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2017
• Subjects: Bermuda; Clumped isotopes; Heinrich events; Last Interglacial; Paleoclimate; 1910 Oceanography; 1911 Palaeontology; Greenland; Rocky Bay; Ice Sheet; North Atlantic
• Online Access: https://espace.library.uq.edu.au/view/UQ:09c1a1c

The warm climate of Bermuda today is modulated by the nearby presence of the Gulf Stream current. However, iceberg scours in the Florida Strait and the presence of ice-rafted debris in Bermuda Rise sediments indicate that, during the last deglaciation, icebergs discharged from the Laurentide Ice Sheet traveled as far south as subtropical latitudes. We present evidence that an event of similar magnitude affected the subtropics during the Last Interglacial, potentially due to melting of the Greenland Ice Sheet. Using the clumped isotope paleothermometer, we found temperatures ~10°C colder and seawater δO values ~2‰ lower than modern in Last Interglacial Cittarium pica shells from Grape Bay, Bermuda. In contrast, Last Interglacial shells from Rocky Bay, Bermuda, record temperatures only slightly colder and seawater δO values similar to modern, likely representing more typical Last Interglacial conditions in Bermuda outside of a meltwater event. The significantly colder ocean temperatures observed in Grape Bay samples illustrate the extreme sensitivity of Bermudian climate to broad-scale ocean circulation changes. They indicate routine meltwater transport in the North Atlantic to near-equatorial latitudes, which would likely have resulted in disruption of the Atlantic Meridional Overturning Circulation. These data demonstrate that future melting of the Greenland Ice Sheet, a potential source of the Last Interglacial meltwater event, could have dramatic climate effects outside of the high latitudes.