HOLOCENE AND MIS 5E SEA-LEVEL HISTORY FROM BERMUDA AND THE BAHAMAS: A NEW LOOK AT OLD DATA

In Bermuda, a Holocene sea-level rise record has been derived from radiocarbon-dated short-root peat sampled at the peat/bedrock contact in deep interior depressions. The record extends to 32 m and 10 ka. No reversals or sudden jumps, such as one reported @ 7.6 ka, are obvious in the curve itself, but erosion intervals and charcoal horizons do however indicate sudden climate and/or sea-level changes occurring at or about 8 ka.

In the Bahamas (San Salvador, Eleuthera, Inagua) the evidence derived from 230Th dates on corals, unconformities, reef elevations, dune structures, mega-boulder and chevron emplacements viewed together indicate that sea level reached +2 m 132 ka, dipped @ ~ 125 ka, returned to +2.5 m, then suddenly rose to +6 m for a very brief time @ 118 ka before plummeting into a series of late Stage 5 oscillations ending at the maximum lowering in Stage 2 @ 18ka.

The interpretation is that the sudden rise of 4 m at 118 ka is due to ice cap collapsemainly in Antarctica (WAIS). The short peak @ +6 m, the rapid return to glacial conditions, and the subsequent draw-down of sea level is interpreted to be due to the rapid spread of snow cover associated with high sea levels and greater moisture availability to high northern latitudes which suddenly changed the albedo of northern latitudes. The concurrent storminess as evidenced by the mega-boulders, chevrons and rapid dune building is believed to be a result of the constriction of the westerlies into a narrower belt by the expansion of the snow-covered boreal with the attendant increase in pressure gradients, wind and storm intensity and frquency.

Between the “greenhouse” maximum of Stage 5e @ 118 ka and the “icehouse” minimum @ 18 ka there exists a series of downward oscillations dubbed, “the madhouse.” A recent data survey shows similar behavior of 5e sea-level at several other world locations. Significance of extreme short-term events is obvious in land-derived studies of Quaternary geology yet their often obscure or fleeting preservation in ice and ocean sequences cautions against over-generalizations resulting from numerical models derived from them alone. In regard to rapid climate change, the devil, it seems, is in the details.