SYNCHRONICITY AND SENSITIVITY OF ALPINE AND CONTINENTAL GLACIERS TO ABRUPT, GLOBAL, CLIMATIC CHANGES DURING THE YOUNGER DRYAS

Despite a large inventory of paleoclimate data recorded in glacial deposits, ice cores, marine and lake sediments, and pollen profiles, many issues concerning abrupt, late Pleistocene, climate changes remain unresolved. For example, (1) were fluctuations of late Pleistocene ice sheets and alpine glaciers synchronous globally, (2) did Younger Dryas (YD) Southern Hemisphere glacial advances precede those in the Northern Hemisphere, and (3) how sensitive were glaciers globally to abrupt, late Pleistocene, climatic changes?

Radiocarbon and cosmogenic dating now show that some ice sheets and alpine glaciers were synchronous, that the YD in both hemispheres was synchronous, and that glacial fluctuations within the YD seem to be synchronous in both hemispheres. Morphologic, stratigraphic, and chronologic evidence of multiple moraines associated with oscillations of the remnants of the Cordilleran Ice Sheet British Columbia and Washington have revealed four distinct phases of post-LGM oscillations. Four topographically distinct phases have been recognized, two of which fall within the YD. The CIS YD chronology, which closely matches that of ice cores from Greenland and sea surface temperatures in the north Pacific, also matches the chronology of YD alpine moraines in the Rocky Mts., Cascade Range, the European Alps, New Zealand Alps, and the Scandinavian Ice Sheet. In each of these areas, two or more YD moraines suggest that the YD was not only global, but that glaciers were sensitive enough to record at least two distinct phases within the YD. The Cordilleran and Scandinavian Ice Sheets seem to have been in phase with alpine glaciation in these areas, which has significant consequences for interpretation of the cause of sudden, late Pleistocene climatic changes and the interaction between glaciers, climate, and the oceans.