Meltwater pulse recorded in Last Interglacial mollusk shells from Bermuda

Abstract

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 δ18O 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 δ18O 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.

Biogenic carbonate mercury and marine temperature records reveal global influence of Late Cretaceous Deccan Traps

“…2). We observed similarly low values ([Hg] = 0.2 to 1.0 ng g −1 ) for specimens retrieved from Rocky Bay, Bermuda 115–130 thousand years before present 40 , at the height of the previous interglacial interval (Fig. 2, labeled “Pleistocene MIS 5e”).…”

“…We also have collected modern bivalve specimens from: Sabin Point Park along the estuary of the Providence River in Providence, Rhode Island, with 4 specimens that included Crepidula fornicata (MOD-PRO-FORa), Crassostrea virginica (MOD-PRO-VIRa), Geukensia demissa (MOD-PRO-DEMa), and an unidentified bivalve (MOD-PRO-BIVa); Spectacle Island, Boston, Massachusetts, with four specimens of Crassostrea virginica (MOD-SPE-VIRa, MOD-SPE-VIRb, MOD-SPE-VIRc, MOD-SPE-VIRd); Lake Tahoe, California, with four specimens of Corbicula fluminea (MOD-TAH-CORa, MOD-TAH-CORc, MOD-TAH-CORd); and the South River, Virgina, with six specimens of Corbicula fluminea (MOD-SOU-CORa-1.1, MOD-SOU-CORb-1.1, MOD-SOU-CORa-6, MOD-SOU-CORb-6, MOD-SOU-CORa-14, MOD-SOU-CORb-14). Lastly, we analyzed 4 Pleistocene specimens collected from Rocky Bay, Bermuda, three of which were unidentified bivalves (PLE-RB-UNKa, PLE-RB-UNKb, PLE-RB-UNKc), and one specimen of Cittarium pica (PLE-RB-JAPa) collected in a previous study 40 .…”

Seasonally Variable Aquifer Discharge and Cooler Climate in Bermuda During the Last Interglacial Revealed by Subannual Clumped Isotope Analysis

“…A previous paleoclimate study reconstructed cooler‐than‐modern SSTs during MIS 5e at two sites in Bermuda using subannual stable isotopes and bulk clumped isotopes on gastropod fossils of the species C. pica (Winkelstern et al., 2017). Reconstructed paleotemperatures differed significantly between the two sites, despite their close proximity (∼2 km apart) and apparently equivalent geologic age (based on stratigraphic correlation and limited radiometric age dating).…”

“…Both the large apparent temperature difference between the two sites and the extreme level of cooling relative to today were difficult to explain. The authors proposed that cool, fresh, isotopically depleted waters from the melting Greenland Ice Sheet could have traveled southward and temporarily cooled and lowered the isotopic composition of coastal waters around Bermuda (Winkelstern et al., 2017).…”

“…Published clumped isotope data from Winkelstern et al. (2017) were recalculated using improved data processing techniques (IUPAC/Brand parameters; see Petersen et al., 2019) for more accuracy and to enable better comparison with new data. Finally, we present δ 18 O of modern waters (tap and marine) from 16 locations around the island and compare with reconstructed δ 18 O w based on clumped isotope measurements.…”