Loop Current Variability—Its Relation to Meridional Overturning Circulation and the Impact of Mississippi Discharge - Integrated Analysis of Interglacial Climate Dynamics (INTERDYNAMIC) - page 51

Loop Current Variability — Its Relation
to Meridional Overturning Circulation
and the Impact of Mississippi Discharge

Dirk N ü rnberg, Andr é Bahr, Tanja Mildner and Carsten Eden

Abstract The dynamics of the Loop Current (LC) in the Gulf of Mexico (GoM)
during transient climates and interglacials, and its interaction with changes in sea
level, atmospheric circulation, and Mississippi River (MR) discharge were studied.
Geochemical proxy records and numerical modeling indicate that LC eddy shed-
ding and its related heat transport into the GoM increased during the deglaciation.
The model simulations imply decreased LC eddy shedding at lowered sea levels,
while transports through Yucatan and Florida straits increased due to the southward
migration of the Intertropical Convergence Zone (ITCZ) and increased wind-driven
transport in the North Atlantic. Consistent with the model, (isotope) geochemical
proxy records from the northern GoM show glacial/interglacial amplitudes signif-
icantly larger than in the Caribbean and extreme cooling during the Last Glacial
Maximum (LGM) due to the vanishing LC eddy shedding. Prominent deglacial
melt water releases observed south and west of the MR delta are neither present in
the northeastern GoM, nor in sea-surface salinity-records in the subtropical North
Atlantic. The freshwater signals were either a regionally restricted phenomenon or
due to changes in the isotopic composition of the discharged water. Our results
question the impact of MR megadischarges on the large-scale overturning
circulation.

Keywords Loop current Eddy shedding Gulf of Mexico hydrography

Mississippi discharge Interglacials Florida straits Yucatan channel Caribbean