Intermediate water circulation changes in the Florida Straits from a 35 ka record of Mg/Li-derived temperature and Cd/Ca-derived seawater cadmium

Abstract

We generated a high-resolution ocean record of bottom water temperature and seawater Cd from 546 m in the Florida Straits. The record extends to ∼35,000 yr before present, including all of Marine Isotope Stages (MIS) 2 and part of MIS 3. Previously, seawater cadmium (Cdw) has been used as a proxy for the strength of the Atlantic Meridional Overturning Circulation (AMOC) during the last deglaciation. We now consider the temperature and oxygen isotopic composition of seawater reconstructed from the same core in order to provide a fuller picture of water mass properties and circulation at this location. During the Last Glacial Maximum (LGM), Cdw levels were generally low, and a novel Mg/Li-derived temperature record reveals persistently cold temperatures (∼3.6°C, two to three degrees colder than during the Holocene or Marine Isotope Stage 3). During the Younger Dryas and early Heinrich Stadial 1, Cdw was low and temperatures were elevated compared with periods of inferred stronger AMOC. By contrast, there is no indication of AMOC variability over Heinrich Stadials 2 and 3, consistent with previous studies that conclude the AMOC is less sensitive to freshwater forcing during glaciations than during the last deglaciation. While there is some inconsistency between proxies, Cdw increases over some MIS3 Dansgaard–Oeschger interstadials, providing qualified support for a strengthening in AMOC. This is similar to our previous finding that Cdw tracks AMOC variability during the deglaciation. This study highlights the distinct nature of water masses and circulation during the LGM, relative to the stadial (weak AMOC) periods of the deglaciation and Late MIS 3.