NOAA/WDS Paleoclimatology - Lund and Curry 2006 High Resolution Florida Current Foraminferal SST Data

STUDY NOTES: Florida Current foraminiferal oxygen isotope and Mg/Ca records for the last millennium from two cores in the Dry Tortugas and two cores on the Great Bahama Bank. The d18Ocalcite values are in per mil units, the Mg/Ca values mmol/mol. This file updated 6/2012 with the addition of SST reconstructions, data series 2. and 3. below (Original receipt by WDC Paleo 10/2007). Core locations: Dry Tortugas sites 62MC 24°19.60N, 83°15.40W, 547 m depth 79GGC 24°21.50N, 83°20.90W, 530 m depth The Great Bahama Bank sites 118MC 24°35.40N, 79°16.10W, 531 m depth 125MC 24°45.50N, 79°17.50W, 694 m depth
ABSTRACT SUPPLIED BY ORIGINATOR: 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 timescales. 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 (d18Ow) 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. On the Great Bahama Bank, where surface waters are influenced by the North Atlantic subtropical gyre, d18Ow 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 ECO2, the remaining d18Ow signal implies a 0.4–1 increase in salinity after 200 years B.P. The simplest explanation of the d18Ow data is southward migration of the Atlantic Hadley circulation during the LIA. Scaling of the d18Ow records to salinity using the modern low-latitude d18Ow-S slope produces an unrealistic reversal in the salinity gradient between the two sites. Only if d18Ow is scaled to salinity using a high-latitude d18Ow-S slope can the records be reconciled. Variable atmospheric 14C paralleled Dry Tortugas d18Ow, suggesting that solar irradiance paced centennial-scale migration of the Inter-Tropical Convergence Zone and changes in Florida Current salinity during the last millennium.