Pliocene-Pleistocene evolution of sea surface and intermediate water temperatures from the southwest Pacific
McClymont, EL; Elmore, AC; Kender, S; et al.Leng, MJ; Greaves, M; Elderfield, H
Date: 1 June 2016
Journal
Paleoceanography
Publisher
Wiley & American Geophysical Union (AGU)
Publisher DOI
Abstract
Over the last 5 million years, the global climate system has evolved toward a colder mean state,
marked by large-amplitude oscillations in continental ice volume. Equatorward expansion of polar waters
and strengthening temperature gradients have been detected. However, the response of the mid latitudes
and high latitudes of the ...
Over the last 5 million years, the global climate system has evolved toward a colder mean state,
marked by large-amplitude oscillations in continental ice volume. Equatorward expansion of polar waters
and strengthening temperature gradients have been detected. However, the response of the mid latitudes
and high latitudes of the Southern Hemisphere is not well documented, despite the potential importance for
climate feedbacks including sea ice distribution and low-high latitude heat transport. Here we reconstruct the
Pliocene-Pleistocene history of both sea surface and Antarctic Intermediate Water (AAIW) temperatures on
orbital time scales from Deep Sea Drilling Project Site 593 in the Tasman Sea, southwest Pacific. We confirm
overall Pliocene-Pleistocene cooling trends in both the surface ocean and AAIW, although the patterns are
complex. The Pliocene is warmer than modern, but our data suggest an equatorward displacement of the
subtropical front relative to present and a poleward displacement of the subantarctic front of the Antarctic
Circumpolar Current (ACC). Two main intervals of cooling, from ~3 Ma and ~1.5 Ma, are coeval with cooling
and ice sheet expansion noted elsewhere and suggest that equatorward expansion of polar water masses
also characterized the southwest Pacific through the Pliocene-Pleistocene. However, the observed trends in
sea surface temperature and AAIW temperature are not identical despite an underlying link to the ACC, and
intervals of unusual surface ocean warmth (~2 Ma) and large-amplitude variability in AAIW temperatures
(from ~1 Ma) highlight complex interactions between equatorward displacements of fronts associated with
the ACC and/or varying poleward heat transport from the subtropics.
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