Abstract:
Today, deep waters produced in the North Atlantic are exported through the
western South Atlantic. Antarctic intermediate water AAJW also enters the Atlantic in this
region. Circumpolar deep water (CDW) fills the depths below AAIW and above and below
northern source waters. A depth transect of cores from 1567-3909 m water depth in the
western South Atlantic are ideally located to monitor inter-ocean exchange of deep water,
and variations in the relative strength of northern versus southern source water production.
Last glacial maximum (LGM) Cd/Ca and δ13C data indicate a nutrient-depleted
intermediate-depth water mass. In the mid-depth western South Atlantic, a simple
conversion of LGM δ13C data suggests significantly less nutrient enrichment than LGM
Cd/Ca ratios, but Cd/Ca and δ13C data can be reconciled when plotted in CdW/δ13C
space. Paired LGM Cd/Ca and δ13C data from mid-depth cores suggest increasingly
nutrient rich waters below 2000 m, but do not require an increase in Southern Ocean water
contribution relative to today. Cd/Ca data suggest no glacial-interglacial change in the
hydrography of the deepest waters ofthe region. To maintain relatively low Cd/Ca ratios
low nutrients in the deepest western South Atlantic waters, and in CDW in general,
during the LGM requires an increased supply ofnutrient-depleted glacial North Atlantic
intermediate water (GNA1W) and/or nutrient-depleted glacial Subantarctic surface waters to
CDW to balance reduced NADW contribution to CDW. LGM Cd/Ca and δ13C data
suggest strong GNA1W influence in the western South Atlantic which in turn implies
export of GNAIW from the Atlantic, and entrainment of GNA1W into the Antarctic
Circumpolar current.
