Gulf Stream Temperature, Salinity and Transport During the Last Millennium
MASSACHUSETTS INST OF TECH CAMBRIDGE JOINT PROGRAM IN APPLIED OCEAN SCIENCE AND ENGINEERING
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Benthic and planktonic foraminiferal delta exp 18 oxygen deltaexp 18Oxygensub c from a suite of well-dated, high-resolution cores spanning the depth and width of the Straits of Florida indicate Gulf Stream vertical current shear was anomalously low during the Little Ice Age LIA 1200-1850 A.D.. Assuming a constant level of no motion, the foraminiferal data imply transport was 2-3 Sv lower during the LIA than today. The timing of reduced flow is consistent with cold conditions in Northern Hemisphere paleoclimate archives, implicating Gulf Stream heat transport in centennial-scale climate variability of the last 1,000 years. The oxygen isotopic composition of Florida Current surface water deltaexp 18Oxygen sub w near Dry Tortugas increased 0.4o during the course of the Little Ice Age LIA -1200-1850 A.D., equivalent to a salinity increase of 0.8-1.5 psu. On the Great Bahama Bank, where surface waters are influenced by the North Atlantic subtropical gyre, deltaexp 18 oxygensub w increased by 0.3o during the last 200 years, a 0.4 to 1 psu increase in salinity. The simplest explanation of the deltaexp 18 Oxygensub w data is southward migration of the Atlantic Hadley circulation during the LIA. Changes in atmospheric 14C paralleled shifts in Dry Tortugas deltaexp 18 Oxygensub w, suggesting that variable solar irradiance paced centennial-scale Hadley cell migration and changes in Florida Current salinity.
- Geology, Geochemistry and Mineralogy
- Physical and Dynamic Oceanography