UTILIZING DEEP-SEA SEDIMENT PROXIES IN THE HIGH LATITUDE NORTH ATLANTIC TO BETTER UNDERSTAND MERIDIONAL OVERTURNING CIRCULATION DURING HEINRICH STADIAL 1, THE BOLLINGALLEROD, AND THE YOUNGER DRYAS

The Meridional Overturning Circulation (MOC) is a crucial component of the worldwide climate system. Paleoclimate research has demonstrated that large changes in the MOC played a role in the abrupt climate changes that occurred during the last ice age. In particular, Heinrich Stadial 1 (HS1) (~17.8 ka) and the Younger Dryas (YD) (~12.0 ka) were events characterized by ice rafting, abrupt cooling across the Northern Hemisphere and weakening of the MOC. Whereas the warm BollingAllerod (BA) interval (~14.5 ka), saw a decrease in ice rafting and strengthening of MOC. The climatic drivers associated with these abrupt climate events are still not fully understood.

In order to better understand past dynamics of the MOC this study utilizes deep-sea sediment proxies, such as foraminifera δ¹⁸O concentrations, benthic foraminifera δ¹³C concentrations, and percent ice rafted debris (IRD) from core EW9302-25GGC (62°03’78 N, 21°28’33 W) located just south of Iceland in the pathway of the MOC. Our percent IRD record indicates highest ice rafting during HS1 and the YD, while ice rafting is low during the BA. The benthic δ¹³C concentrations decrease abruptly at the initiation of HS1 (17.8 ka) and remain relatively low through the BA and into the YD. The low δ¹³C concentrations may indicate a weakening in MOC strength around 17.8 ka, and at 12.47 ka, with a return to more vigorous overturning by 7 ka. When comparing the IRD and δ¹³C concentrations it is apparent that rapid declines in δ¹³C precede major ice rafting events (HS1 and the YD). This has been shown in other studies and may indicate a change in MOC strength prior to ice-rafting. Furthermore, the data may demonstrate that MOC strength is a potential trigger for ice rafting in the high latitude North Atlantic. This research improves upon our knowledge of MOC dynamics during abrupt climate change events and may offer clues about potential drivers associated with abrupt climate change in the high latitude North Atlantic.