A Tale of Two Drifts: A High-Resolution Study of North Atlantic Deepwater Using Marine Proxies at Eirik and Gardar Drifts

Abstract:

The North Atlantic Ocean is a crucial area of deep-water formation; therefore, understanding the perturbations to the surface and deep-water systems in this area is imperative to understanding the mechanisms that control abrupt climate changes. Geochemical and sedimentological marine proxies have recorded these changes in circulation during abrupt millennial-scale climate events that punctuated the last deglacial interval (Hodell et al., 2009; 2015; Muschitiello et al., 2019). This study conducted downcore planktonic foraminiferal species counts on core 13JPC (3082 m) from Gardar Drift and15JPC (2240m) from Eirik Drift to further investigate the rapid climate and water mass changes since the Last Glacial Maximum (LGM).

The leading theory for the mechanism of abrupt climate events during the deglacial is the input of freshwater to the surface ocean by melting ice sheets. However, recent work done on Eirik Drift (15JPC) shows that deep-water was still in the “conveyor on” mode during the largest meltwater pulses, contradicting this theory. The purpose of this study is to generate a geochemical and sedimentological record as well as an age model for core 13JPC so that the two cores can be directly compared to evaluate how these two water mass contributions have varied since the LGM.

Newly obtained AMS 14C dates better constrain the millennial-scale climatic events of the deglacial record in core 13JPC and revise the age model previously published by Hodell et al. (2010). Overall species counts at 15JPC indicate that it was a colder site and counts at 13JPC indicate it was warmer. Core 15JPC may have been located closer to the meltwater source during the deglacial period, as evidenced by spikes in Globigerinoides bulloides (G. bulloides) species counts and low δ18O values. On the other hand, the peaks of G. bulloides species counts in 13JPC are attributed to it being a warmer site, not as a result of meltwater pulses, as suggested by the higher values of δ18O and stable % species per gram values. While research is ongoing, additional AMS 14C dates are needed to further refine the age model for 13JPC before the site to site comparison of the deepwater circulation changes can be made.