RAPID SEA-LEVEL CHANGE AND INTENSIFIED STORMS DURING THE LAST INTERGLACIAL: A HIGH RESOLUTION RECORD FROM THE BAHAMAS

Short-term events are often obscured in ocean and ice core records, whereas terrestrial sequences can provide a higher resolution picture of climate variability. Due to low subsidence rates, rapid cementation, and the sensitivity of shallow carbonate facies to climatic shifts, sequences on several islands of the Bahamas Platform (Eleuthera, San Salvador, Great Inagua, Providenciales) preserve a detailed record of extreme short-term events during the last interglacial (MIS 5e). Several lines of geologic evidence from the Bahamas indicate that climate destabilized toward the end of the last interglacial, resulting in rapid sea level fluctuations and an intensification of tropical storms.

Examined together, fossil reef elevations, U-Th dates on corals, emergent bio-erosional notches, and facies stacking patterns indicate that sea level during MIS 5e rose to +2 meters at 132ka, dropped mid-stage at ~125ka, rebounded to +2.5 meters, then rose rapidly to a brief maximum of +6 meters at 118ka, before falling into a series of late stage 5 oscillations. The rapid 4m rise of sea level toward the end of MIS 5e is interpreted to be due to ice sheet collapse in West Antarctica. Higher sea levels increased atmospheric moisture and albedo in the northern polar latitudes spurring a rapid deterioration to glacial conditions and the subsequent fall of sea level.

The rapid fall of sea-level at the end of MIS 5e was accompanied by an increase in wind and storm intensity, as indicated by voluminous eolian deposition, emplacement of mega-boulders, and fenestrae-rich storm deposits. In particular, the storm deposits range from lowland storm-beach ridges to thin fenestrae beds in eolian ridges, and form as storm waves run over, run up, and run out on coastal dunes. Such deposits are found on multiple islands across the platform and suggest that the onset of glaciation and concomitant compression of the Westerlies belt at the end of MIS 5e gave rise to more frequent and powerful tropical storms than today.