News & Events

Noon seminar - Sea level during the last interglacial period in southern Florida: Implications

Monday, September 13, 2010, 12:00PM - 1:00PM


Daniel Muhs

U.S. Geological Survey and INSTAAR Affiliate


ARC 620

Full title: "Sea level during the last interglacial period in southern Florida: Implications for the history of the Greenland and West Antarctic ice sheets."

As a future warm-climate analog, much attention has been directed to studies of the last interglacial period or marine isotope stage (MIS) 5.5, which occurred ~120,000 years ago. Nevertheless, there are still uncertainties with respect to its duration, warmth and magnitude of sea level rise. Here we present new data from tectonically stable peninsular Florida and the Florida Keys that provide estimates of the timing and magnitude of sea-level rise during the last interglacial period. The last interglacial high sea stand in southern Florida is recorded by the Key Largo Limestone, a fossil reef complex, and the Miami Limestone, an oolitic marine sediment. Thirty-five new, high-precision, uranium-series ages of fossil corals from the Key Largo Limestone indicate that sea level was significantly above present for at least 9,000 years during the last interglacial period, and possibly longer. Ooids from the Miami Limestone show open-system histories with respect to U-series dating, but show a clear linear trend towards an age of ~120 ka, correlating this unit with the last interglacial corals of the Key Largo Limestone. Elevation measurements of both the Key Largo Limestone and the Miami Limestone indicate that local (relative) sea level was at least 6.6 m, and possibly as much as 8.5 higher than present during the last interglacial period. A sea-level rise of this magnitude, if it reflects global sea level, would require complete loss of either the Greenland or West Antarctic ice sheets, or some combination of loss from both. Should a sea-level rise of comparable magnitude occur in a future warm climate, many of the world’s coastal cities would be inundated, including all those of southern Florida.