Description: Previous studies showed that sea surface salinity (SSS) in the Florida Straits as well as Florida Current transport covaried with changes in North Atlantic climate over the past two millennia. However, little is known about earlier Holocene hydrographic variability in the Florida Straits. Here, we combine Mg/Ca-paleothermometry and stable oxygen isotope measurements on the planktonic foraminifera Globigerinoides ruber (white variety) from Florida Straits sediment core KNR166-2 JPC 51 (24° 24.70' N, 83° 13.14' W, 198 m deep) to reconstruct a high-resolution (~25 yr/sample) early to mid Holocene record of sea surface temperature and d18OSW (a proxy for SSS) variability. After removing the influence of global d18OSW change due to continental ice volume variability, we find that early Holocene SSS enrichments are associated with increased evaporation/precipitation ratios in the Florida Straits during periods of reduced solar forcing, increased ice rafted debris in the North Atlantic and the development of more permanent El Niño-like conditions in the eastern equatorial Pacific. When considered with previous high-resolution reconstructions of Holocene tropical atmospheric circulation changes, our results provide evidence that variations in solar forcing over the early Holocene had a significant impact on the global tropical hydrologic cycle.

Description: The prevailing paradigm of abrupt climate change holds that rapid shifts associated with the most extreme climate swings of the last glacial cycle were forced by changes in the strength and northward extension of Atlantic Meridional Overturning Circulation (AMOC), resulting in an abrupt reorganization of atmospheric circulation patterns with global teleconnections. To determine the timing of tropical Atlantic atmospheric circulation changes over the past 21 ka BP, we reconstruct high resolution sea surface temperature and d18OSW (a proxy for surface salinity) records based on Mg/Ca ratios and oxygen isotope measurements in the planktonic foraminifera Globigerinoides ruber from a sediment core located on the western margin of the Florida Straits. As a proxy for meltwater discharge influence on Florida Straits surface water salinity, we also measured Ba/Ca ratios in G. ruber from the same core. Results show that riverine influence on Florida Straits surface water started by 17.2 ka BP and ended by 13.6 ka BP, 600 years before the start of the Younger Dryas (YD) cold interval. The initiation of the YD is marked by an abrupt increase in Florida Straits d18OSW values, indicating a shift to elevated sea surface salinity occurring in 130 years, most likely resulting from increased regional aridity and/or reduced precipitation. In order to resolve the timing of tropical atmospheric circulation change relative to AMOC variability across this transition, we compare the timing of surface water changes to a recently published record of Florida Current variability in the same core reconstructed from benthic oxygen isotope measurements. We find synchronous changes in atmospheric and ocean circulation on the transition into the YD, consistent with an abrupt reduction in AMOC as the driver of tropical Atlantic atmospheric circulation change at this time.