Bahr, André, Nürnberg, Dirk , Schönfeld, Joachim and Garbe-Schönberg, Dieter (2011) Hydrological variability in Florida Straits during Marine Isotope Stage 5 cold events. Paleoceanography, 26 (2). PA2214. DOI 10.1029/2010PA002015.

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Abstract

Modeling and proxy studies indicate that a reduction of Atlantic Meridional
Overturning Circulation (AMOC) strength profoundly impacts temperatures and salinities
in the (sub)tropical Atlantic, especially on subsurface levels. While previous studies
focused on prominent periods of AMOC reduction during the last deglaciation, we aim to
test whether similar reconfigurations of the subtropical hydrography occurred during the
moderate climatic alterations punctuating the last interglacial Marine Isotope Stage (MIS) 5.
Here, we present temperature and salinity records from a Florida Straits core by combining
d18O and Mg/Ca analyses on surface (Globigerinoides ruber, white) and deep‐dwelling
(Globorotalia crassaformis) foraminifera covering MIS 5 in high resolution. The data
reveal increasing salinities at intermediate depths during interglacial cooling episodes,
decoupled from relatively stable surface conditions. This probably indicates the spatial
expansion of saline subtropical gyre waters due to enhanced Ekman downwelling
and might also point to a changed density structure and altered geostrophic balance in
Florida Straits. Notably, these oceanographic alterations are not consistently occurring
during periods of AMOC reduction. The data suggest that the expansion of gyre waters
into Florida Straits was impeded by the increasing influence of Antarctic Intermediate
Water (AAIW) from MIS 5.5 to ∼107 kyr BP. Afterward, increasingly positive benthic
d13C values imply a recession of AAIW, allowing the temporary expansion of gyre waters
into Florida Straits. We argue that the inferred transient subtropical salt accumulation
and warm pool expansion might have played a pivotal role in reinvigorating meridional
overturning and dampen the severity of interglacial cold phases.

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