SYNCHRONOUS ICE-DAM COLLAPSES AND OUTBURST FLOODING FROM NORTHERN HEMISPHERE PROGLACIAL LAKES AT YOUNGER DRYAS ONSET (12.8 KA) IMPLIES COSMIC IMPACT TRIGGER

The widely accepted hypothesis explaining the triggering of Younger Dryas (YD) cooling (12.8 ka) involves massive fresh water overflow from proglacial Lake Agassiz into the surrounding oceans, changing thermohaline circulation that in turn caused abrupt YD cooling. Recent evidence suggests much broader glacial processes were involved related to instability of the Northern Hemisphere ice sheet margins, proglacial lakes and outflow conduits. Crucially, F. Muschitiello and others demonstrated, using high resolution sediment chronology from SE Sweden, that the first catastrophic outburst flood from the Baltic Ice Lake (Fennoscandian Ice Sheet) occurred precisely at the YD onset as correlated with Greenland ice cores. Furthermore, L. Keigwin demonstrated, using his Arctic sediment oxygen isotopic record, that the first major outburst flooding and drawdown of Lake Agassiz occurred precisely at the YD onset, confirming the earlier interpretations of J. Teller, J. Murton and others.

These records alone, demonstrate that both the huge North American and European proglacial lakes catastrophically drained into the surrounding oceans through ice dam failure at exactly the same time. Furthermore, significant evidence now exists for more widespread ice sheet margin and glacial lake instability at the YD onset. This includes the Greenland Ice Sheet that demonstrates noticeable instability of the ice sheet margin at or close to the YD onset. Also, evidence exists for the establishment of eastward drainage through the St. Laurence Seaway at the YD onset, including the final drainage of proglacial Lake Vermont and the initial incursion of marine conditions there that mark the Champlain Sea, as shown by T. Cronin and colleagues. Other effects of such plumbing changes in the sediment record are from the St. Laurence estuary, Labrador Sea and Hudson Strait.

It is difficult to explain the triggering of such widespread synchronous changes at the margins of three relatively isolated Northern Hemisphere ice sheets; Laurentide, Fennoscandian and Greenland, and their related proglacial lakes by invoking conventional climatic and/or paleoceanographic processes. Instead, this broad range of evidence is more readily explained by catastrophic processes triggered by a cosmic impact with Earth; the YDB cosmic impact theory.