LAURENTIDE ICE SHEET BEHAVIOR DURING THE YOUNGER DRYAS: A WORKING HYPOTHESIS AND IMPLICATIONS
Surficial mapping with a 10 m digital elevation data set, combined with field investigations, show that ice margin features along the right lateral portion of the Green Bay Lobe are spatially compressed with the Two Creeks and Marquette intervals separated by only 35 km. Between these two limits, mapping revealed a series of four ice contact slopes, each at an interlobate position. This sequence indicates a series of temporary ice contact slope positions during LIS retreat.
Prior work suggests that the Younger Dryas caused the LIS to readvance a substantial distance. This would agree with Greenland ice core data which indicates near-full-glacial conditions. However, multiple ice margins between the YD limits allows for alternative possibilities, one of which is that the LIS retreated in steps during the YD. If so, this implies warmer summers during the Younger Dryas, as has been reported in Greenland and Scandinavia.