1. Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography, Woods Hole, Massachusetts 02543, USA
2. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
3. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
4. Present address: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA.

Correspondence to: David C. Lund^1,4 Correspondence and requests for materials should be addressed to D.C.L. (Email: dlund@gps.caltech.edu).

Abstract

The Gulf Stream transports approximately 31 Sv (1 Sv = 10⁶ m³ s^-1) of water^{1, 2} and 1.3  10¹⁵ W of heat³ into the North Atlantic ocean. The possibility of abrupt changes in Gulf Stream heat transport is one of the key uncertainties in predictions of climate change for the coming centuries. Given the limited length of the instrumental record, our knowledge of Gulf Stream behaviour on long timescales must rely heavily on information from geologic archives. Here we use foraminifera from a suite of high-resolution sediment cores in the Florida Straits to show that the cross-current density gradient and vertical current shear of the Gulf Stream were systematically lower during the Little Ice Age (ad  1200 to 1850). We also estimate that Little Ice Age volume transport was ten per cent weaker than today's. The timing of reduced flow is consistent with temperature minima in several palaeoclimate records^{4, 5, 6, 7, 8, 9}, implying that diminished oceanic heat transport may have contributed to Little Ice Age cooling in the North Atlantic. The interval of low flow also coincides with anomalously high Gulf Stream surface salinity¹⁰, suggesting a tight linkage between the Atlantic Ocean circulation and hydrologic cycle during the past millennium.

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.