Centennial‐ to millennial‐scale ice‐ocean interactions in the subpolar northeast Atlantic 18–41 kyr ago

Abstract

In order to monitor the evolution of the British‐Irish Ice Sheet (BIIS) and its influence in surface ocean structure during marine isotopic stages (MIS) 2 and 3, we have analyzed the sediments recovered in core MD04‐2829CQ (Rosemary Bank, north Rockall Trough, northeast Atlantic) dated between ∼41 and ∼18 ka B.P. Ice‐rafted debris flux and composition,40Ar/39Ar ages of individual hornblende grains, multispecies planktonic stable isotope records, planktonic foraminifera assemblage data and faunal‐based sea surface temperatures (SSTs) demonstrate a close interaction between BIIS dynamics and surface ocean structure and water properties in this region. The core location lies beneath the North Atlantic Current (NAC) and is ideal for monitoring the shifts in the position of its associated oceanic fronts, as recorded by faunal changes. These data reveal a succession of BIIS‐sourced iceberg calving events related to low SST, usually synchronous with dramatic changes in the composition of the planktonic foraminifera assemblage and with variations in the stable isotope records of the taxaNeogloboquadrina pachyderma(sinistral coiling) andGlobigerina bulloides. The pacing of the calving events, from typically Dansgaard‐Oeschger millennial timescales during late MIS 3 to multicentennial cyclicity from ∼28 ka B.P., represents the build‐up of the BIIS and its growing instability toward Heinrich Event (HE) 2 and the Last Glacial Maximum. Our data confirm the strong coupling between BIIS instabilities and the temperature and salinity of surface waters in the adjacent northeast Atlantic and demonstrate the BIIS's ability to modify the NAC on its flow toward the Nordic Seas. In contrast, subsurface water masses were less affected except during the Greenland stadials that contain HEs, when most intense water column reorganizations occurred simultaneously with the deposition of cream‐colored carbonate sourced from the Laurentide Ice Sheet.