(
2010-08)
Benway, Heather M.; McManus, Jerry F.; Oppo, Delia W.; Cullen, James L.
Millennial-scale climate fluctuations of the last deglaciation have been tied to abrupt
changes in the Atlantic Meridional Overturning Circulation (MOC). A key to
understanding mechanisms of MOC collapse and recovery is the documentation of upper
ocean hydrographic changes in the vicinity of North Atlantic deep convection sites. Here
we present new high-resolution ocean temperature and δ18Osw records spanning the last
deglaciation from an eastern subpolar North Atlantic site that lies along the flow path of
the North Atlantic Current, approaching deep convection sites in the Labrador and
Greenland-Iceland-Norwegian (GIN) Seas. High-resolution temperature and δ18Osw
records from subpolar Site 980 help track the movement of the subpolar/subtropical front
associated with temperature and Atlantic MOC changes throughout the last deglaciation.
Distinct δ18Osw minima during Heinrich-1 (H1) and the Younger Dryas (YD) correspond
with peaks in ice-rafted debris and periods of reduced Atlantic MOC, indicating the
presence of melt water in this region that could have contributed to MOC reductions
during these intervals. Increased tropical and subtropical δ18Osw during these periods of
apparent freshening in the subpolar North Atlantic suggest a buildup of salt at low
latitudes that served as a negative feedback on reduced Atlantic MOC.
