Deep Ocean Circulation at the Bermuda Rise during the Last 150ka: A New Centennial-Resolution Nd Isotope Record

Abstract:

Today the Deep Western Boundary Current in the NW Atlantic basin transports an average of 28.7 Sv (Toole et al., 2011), making it a crucial part of the Atlantic Meridional Overturning Circulation, and linking ocean heat transport and carbon storage with northern hemisphere climate. Greenland ice cores have provided high resolution archives for northern hemisphere climate change over the past glacial cycle. However, accurate comparison between changes in climate and ocean dynamics is hampered by generally low marine sedimentation rates relative to ice accumulation.

Here we present an ultra-high resolution Nd isotope record, with an average of 164 years between samples, reconstructing past changes in ocean circulation from MIS 6 to the present. The Nd isotope measurements were made on uncleaned planktonic foraminifera, recording bottom water composition changes (Roberts et al., 2010; Roberts et al., 2012), on a high sedimentation rate core (average 24 cm/kyr) taken from the Bermuda Rise (33°N, 57°W, 4500m) to the west of the Deep Western Boundary Current. Such high resolution allows for detailed reconstruction of millennial and centennial-scale deep ocean circulation events and statistical comparison with Greenland and Antarctic ice core records as well as other terrestrial climate records.