Publication Date:
2022-05-25
Description:
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography, 21 (2006): PA2009, doi:10.1029/2005PA001218.
Description:
The salinity and temperature of the Florida Current are key parameters affecting the
transport of heat into the North Atlantic, yet little is known about their variability on centennial time scales. Here we report replicated, high-resolution foraminiferal records of Florida Current surface hydrography for the last millennium from two coring sites, Dry
Tortugas and the Great Bahama Bank. The oxygen isotopic composition of Florida
Current surface water (δ18Ow) near Dry Tortugas increased 0.4‰ 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, δ18Ow increased by 0.3‰ during the last 200 years. Although a portion
(~0.1‰) of this shift may be an artifact of anthropogenically-driven changes in surface
water ΣCO2, the remaining δ18Ow signal implies a 0.4 to 1 psu increase in salinity after
200 yr BP. The simplest explanation of the δ18Ow data is southward migration of the
Atlantic Hadley circulation during the LIA. Scaling of the δ18Ow records to salinity using
the modern low-latitude δ18Ow-S slope produces an unrealistic reversal in the salinity
gradient between the two sites. Only if δ18Ow is scaled to salinity using a high-latitude
δ18Ow-S slope can the records be reconciled. Changes in atmospheric 14C paralleled
shifts in Dry Tortugas δ18Ow, suggesting that variable solar irradiance paced centennialscale
ITCZ migration and changes in Florida Current salinity during the last millennium.
Description:
This work was supported by NSF grant OCE-0096469.
Keywords:
Gulf Stream
;
Salinity
;
Little Ice Age
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
Permalink
