Gulf Stream Salinity Variability during the Last Millennium

David C. Lund [dlund@whoi.edu] and William B. Curry, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography, Woods Hole, Massachusetts.

            The salinity of the Gulf Stream is a key parameter affecting the Atlantic overturning circulation and the transport of heat into the North Atlantic. Although the Gulf Stream is probably the best-studied feature in modern oceanography, almost nothing is known about its behavior on centennial time scales. We will present records of Gulf Stream surface hydrography during the last millennium based on two high-resolution sediment cores retrieved near Dry Tortugas. The oxygen isotopic composition of Gulf Stream surface water (d18Ow) near increased by 0.4‰ during the Little Ice Age (LIA: ~1300-1850 A.D.), which based on modern d18Ow–salinity relationships is equivalent to a salinity increase of 0.8 to 2 psu. Higher Gulf Stream surface salinity during the LIA most likely resulted from southward movement of the Inter-Tropical Convergence Zone (ITCZ). Changes in atmospheric 14C paralleled shifts in d18Ow, suggesting that variable solar irradiance paced centennial-scale ITCZ migration and changes in Gulf Stream salinity during the last millennium.