DID THE SOUTHERN MARGIN OF THE LAURENTIDE ICE SHEET RESPOND TO HEINRICH STADIAL COOLING?
We compiled all available chronologic data defining the advance and retreat patterns of the Laurentide Ice Sheet from samples collected within 50 kilometers of the southernmost extent. This analysis only considered ages that fall between 12.0 and 30.0 ka. We summarize the behavior of various sectors of the ice sheet during HS2 and HS1 in the table below.
|Ice Sheet Sector||HS2||Interstadial||HS1|
|New England||Reached maximum >HS2; Retreat||Retreat||Retreat|
|Lake Huron/Erie Lobe||Advance||Reached maximum extent||Retreat|
|Lake Michigan Lobe||Advance||Reached maximum early interstadial; Retreat||Retreat|
|Green Bay/Chippewa Lobes||Reached maximum >HS2; Retreat||Retreat||Retreat|
|Des Moines Lobe||Unknown||Unknown||Advance|
Based on our analysis, it appears that the lobes of the southern margin of the LIS did not advance and retreat synchronously. More important, the southern LIS margin did not respond to cooling in the North Atlantic during Heinrich Stadials 2 and 1. We put forth the suggestion that local climate conditions, or more specifically ablation rates, may have played a large role in the behavior of the individual lobes.