BERING GLACIER ANALOG FOR LAURENTIDE RETREAT IN NEW YORK STATE

An extensive ice-marginal drainage system developed along the retreating Laurentide Ice Sheet (LIS) as it pulled back from the Appalachian Plateau of central and western NYS. The Batavia Moraine was left draped across a valley, thus damming an ice-contact lake during retreat. Paradoxically, the moraine's kame and kettle expression contains ice-contact laminated sand, silt and clay. Challenged by the occurrence of an ice-cored landform consisting of lacustrine sediments (isn't ice supposed to float?), we set out to identify a modern ice-contact lake analog that might accommodate such an environment, and found it at Bering Piedmont Glacier, Alaska.

As a 20 km wide, warm-based piedmont lobe with peripheral drainage along a series of terminal ice-contact lakes, the Bering provided an opportunity to monitor processes that were once active along the similarly configured LIS. We monitored fluctuations in temperature and turbidity of meltwater discharge from a series of ice front, supercooled, fountaining vents, conducted sequential bathymetric surveys to measure annual rates of lacustrine sedimentation, and mapped progressive foreland retreat. A fortuitous ice-dam failure in 1989 caused a breakout that lowered lake level 14 m, thus exposing grounded ice islands in the process of burial on the lake floor. Our search was complete. Such conditions are surprisingly common in the Bering Glacier system.

Our research took on an entirely new direction with the onset of the 1993-95 surge and outburst floods, followed by more than a decade of retreat from overridden terrain. Minimal erosional and depositional effects of overriding ice are in contrast with the extensive topographic modification produced by pressurized subglacial water flow. Jokulhlaup deposits provide insight to similar Neoglacial events.