CHANGING OCEANS AND CHANGING CLIMATES: EXAMINING DEEP-WATER CIRCULATION CHANGES ON GARDAR DRIFT

The North Atlantic Ocean is a critical part of the Great Ocean Conveyor. Previous work has shown the strength of the deep-water circulation and Earth’s climate are closely related (Broecker et. al. 1991; Bond et.al. 1992), however, the exact link between the two is still the subject of much research. The accepted theory is that fresh water in pulses to the North Atlantic Ocean and weakens the production of deep-water (Broecker et. al. 1991). Core 13JPC (3082 m), from the Gardar Drift in the North Atlantic was chosen for this study due to the high sedimentation rates (~10 to 50+ cm/kyr), its down current proximity to Iceland-Scotland Overflow Water (ISOW), and its expanded record from the Last Glacial Maximum to today. These factors allow us to evaluate in high-resolution if the proposed freshwater flushes to the North Atlantic were accompanied by reductions in deep-water production.

Work is ongoing, but the goal is to reconstruct the history of deep-water production in this area by producing high-resolution downcore records of δO18, Mg/Ca ratios, sedimentation rates, and percent coarse fraction values. 10 AMS δC¹⁴ dates were obtained that provided age control for the Last Glacial Maximum and deglaciation section of the core. Downcore planktonic and benthic foraminifera stable isotopic records were previously obtained by Hodell et al., 2009, however, the records from the Holocene section of the core were missing. Work was done to prepare the Holocene samples to analyze them for δO¹⁸ and δC¹³ values, as well as downcore Mg/Ca ratios. These results would allow me to isolate temperature and salinity values from the δO¹⁸ and analyze the effect of any meltwater pulses to the circulation system. Preliminary work suggests that the Holocene was very warm at this site as we see very few of the polar species, Neogloboquadrina pachyderma (sinistral), in the samples. Therefore, further work must be done to identify a different species to use for the δO¹⁸ and Mg/Ca ratios for the Holocene samples. Initial work using Neogloboquadrina pachyderma (sinistral) to produce Mg/Ca ratios for the deglaciation section of the core shows that it can potentially be used to reconstruct the temperature signal for much of the core.