Holocene oscillations in temperature and salinity of the surface subpolar North Atlantic.
The Atlantic meridional overturning circulation (AMOC) transports warm salty surface waters to high latitudes, where they cool, sink and return southwards at depth. Through its attendant meridional heat transport, the AMOC helps maintain a warm northwestern European climate, and acts as a control on the global climate. Past climate fluctuations during the Holocene epoch ( approximately 11,700 years ago to the present) have been linked with changes in North Atlantic Ocean circulation. The behaviour of the surface flowing salty water that helped drive overturning during past climatic changes is, however, not well known. Here we investigate the temperature and salinity changes of a substantial surface inflow to a region of deep-water formation throughout the Holocene. We find that the inflow has undergone millennial-scale variations in temperature and salinity ( approximately 3.5 degrees C and approximately 1.5 practical salinity units, respectively) most probably controlled by subpolar gyre dynamics. The temperature and salinity variations correlate with previously reported periods of rapid climate change. The inflow becomes more saline during enhanced freshwater flux to the subpolar North Atlantic. Model studies predict a weakening of AMOC in response to enhanced Arctic freshwater fluxes, although the inflow can compensate on decadal timescales by becoming more saline. Our data suggest that such a negative feedback mechanism may have operated during past intervals of climate change.
Thornalley
David J R
DJ
The Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK. d.thornalley@cantab.net
Elderfield
Harry
H
McCave
I Nick
IN
D001267:Atlantic Ocean; D002119:Calcium Carbonate / Q000032:analysis; D002980:Climate; D005246:Feedback; D005618:Fresh Water / Q000032:analysis / Q000737:chemistry; D049690:History, Ancient; D010103:Oxygen Isotopes; D010933:Plankton / Q000378:metabolism; D054712:Salinity; D012623:Seawater / Q000737:chemistry*; D013696:Temperature; D014872:Water Movements
D010103:Oxygen Isotopes; D002119:Calcium Carbonate