A HIGH-RESOLUTION STUDY OF THE LAST DEGLACIATION AT EIRIK AND GARDAR DRIFTS: EVIDENCE OF CHANGING WATER MASSES FROM PLANKTONIC FORAMINIFERAL FAUNAL ANALYSIS AND GEOCHEMICAL PROXIES

The analysis of geochemical and sedimentological marine proxies research has shown that the deep-ocean circulation system during the last glacial interval was remarkably different than today (Broecker, 1991; Hunter et al., 2007; Channel et al., 2014, and others). In addition to the glacial-interglacial timescale, changes in circulation have also been observed during the abrupt millennial scale climate events that punctuated the last deglacial interval, such as Heinrich-1 (H1), the Younger Dryas (YD), and the Bølling-Allerød (BA; i.e., Hodell et al., 2009; Renssen et al., 2015; Muschitiello et al., 2019). The North Atlantic Ocean is a critical area of deep-water formation; therefore, understanding the perturbations to the surface and deep-water systems are key to evaluating the mechanisms that control and initiate abrupt climate changes.

This study conducted downcore planktonic foraminiferal species counts on core 15JPC (2240m) from Eirik Drift and 13JPC (3082m) from Gardar Drift to evaluate the rapid climate and water mass changes from the LGM to today. 15JPC and 13JPC were both selected for this study due to their high sedimentation rates, expanded sections from the last deglaciation, and their downstream proximity to the deep-water sources of Denmark-Scotland Overflow Water (DSOW) and Iceland-Scotland Overflow Water (ISOW), respectively. Additionally, 15JPC has excellent age control with 10 AMS 14C dates, benthic and planktonic δ18O and δ13C records, ice-rafted detritus counts, sedimentation rates, and percent coarse fraction records previously generated. The purpose of this study is to generate a record for 13JPC comparable to 15JPC so that a direct evaluation of how these two water mass contributions have varied from the Last Glacial Maximum (LGM) up to the present.

Research is ongoing but preliminary results show the expected trends with cold-water species like Neogloboquadrina pachyderma (sinistral) dominating the record at site 15JPC, and warm-water species like Neogloboquadrina pachyderma (dextral) and Globigerina bulloides peaking during warmer events in 15JPC and being present throughout in 13JPC. Initial results suggest that core 15JPC may have been located closer to the source of influx of fresh meltwater during H1 as observed by high IRD values. Low δ13C values are consistent with this hypothesis as they indicate a greater reduction of deepwater formation during this time than during the YD. Further work in comparing 15JPC to 13JPC will provide more insight into these trends as well as other future observations.