A Review of Abrupt Climate Change Events in the Northeastern Atlantic Ocean (Iberian Margin): Latitudinal, Longitudinal, and Vertical Gradients

Abrupt Climate C Geophysical Mon Copyright 2011 b 10.1029/2010GM The Iberian margin is a key location to study abrupt glacial climate change, and regional variability is studied combining published and new records. Looking at the trend from marine isotope stage (MIS) 10 to 2, the planktic foraminifer data, conforming to Martrat et al. [2007], show that abrupt events, especially Heinrich events, became more frequent and their impacts stronger during the last glacial cycle. However, there were two older periods with strong impacts on the Atlantic meridional overturning circulation: the Heinrich-type event associated with termination IV and the one occurring during MIS 8 (269 to 265 ka). During Heinrich stadials, the Polar Front reached the northern Iberian margin (approximately 41°N), while the Arctic Front was located in the vicinity of 39°N. During all glacial periods, there existed a boundary at the latter latitude, either the Arctic Front during extreme cold events or the Subarctic Front during less strong coolings or warmer glacials. Along with the fronts, sea surface temperature (SST) increased southward by about 1°C per 1° latitude leading to steep SST gradients. Glacial hydrographic conditions were similar during MIS 2 and 4 but much different during MIS 6. MIS 6 was a warmer glacial with subtropical waters reaching as far north as 40.6°N. In the vertical structure, Greenland-type oscillations were recorded down to 2465 m during Heinrich stadials, i.e., deeper than in the western basin, due to the admixing of Mediterranean Outflow Water. It is evident that latitudinal, longitudinal, and