Linking Agulhas Leakage Variability and North Atlantic Climate MIS 1-5a

Tuesday, 16 December 2014
Kelsey A Dyez, San Francisco State University, San Francisco, CA, United States, Rainer Zahn, Univ Autanoma Barcelona, Bellaterra Cerdanyo, Spain and Ian R Hall, Cardiff University, Cardiff, United Kingdom
Agulhas leakage of warm, salty water from the Indian Ocean to the South Atlantic is suggested to have altered Atlantic meridional overturning and climate in the North Atlantic. One way to assess such linkages with North Atlantic climate variability is to examine the past Agulhas hydrography via high-resolution marine records from the Agulhas Bank slope. Here we present one such hydrographic estimate from the Agulhas Bank slope in the Atlantic sector of the Agulhas Corridor using planktic foraminiferal (Globigerinoides ruber) δ18O and Mg/Ca-derived SST to estimate surface salinity.

By focusing on the last 80,000 years this is the first quantitative fine-scale Agulhas leakage record that overlaps in time with the Greenland ice core record of abrupt climate changes in the North Atlantic region. Periods of enhanced Agulhas Corridor salinity occur at Northern Hemisphere cool periods (glacial termination and Heinrich meltwater events) and are followed by rapid northern hemisphere warming. We show that the timing of maximal salinity events in relation to periods of North Atlantic freshwater perturbation is consistent with the concept suggested by climate models that Agulhas salinity oscillations could provide buoyancy compensation for the Atlantic and potentially even trigger increased convective activity in the North Atlantic, thereby restoring Atlantic overturning circulation after relatively weak states.