Bipolar Atlantic deepwater circulation in the middle-late Eocene: Effects of Southern Ocean gateway openings

Links between CO<sub>2</sub>, glaciation and water flow: reconciling the Cenozoic history of the Antarctic Circumpolar Current

“…In addition, the Antarctic glaciation cools the continent and the surrounding ocean, leading to an increase in sea ice formation (DeConto et al, 2007;Goldner et al, 2014;Houben et al, 2013). Our results support the development of a proto-ACC of moderate intensity following the buildup of the ice sheet, roughly coeval with the EO (Eocene-Oligocene) transition onset of the ACC suggested by, e.g., Latimer and Filippelli (2002), Diekmann et al (2004) and more recently Borrelli et al (2014).…”

Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic

“…From an oceanic viewpoint, this process would correspond to progressive latitudinal contraction of the subtropical gyre. Isotopic tracers provide evidence for major reorganization in the circulation of deep ocean waters in the late Middle Eocene (11,12). Meanwhile, the Northern Atlantic Ocean did not experience cooling, as coeval warming during the Late Eocene was reported from site ODP 913 at 70°N (4) (Fig.…”

“…In contrast, high-latitude sites are consistent in demonstrating appreciable cooling of austral subpolar regions during much of the Eocene (3,4,(6)(7)(8). This apparent lack of substantial temperature change in the intertropical belt during the Eocene and across the EOT remains an enigmatic feature that complicates our understanding of the interplay between seawater temperatures at a global scale, pCO 2 , and changes in global ocean circulations in the context of new Southern Ocean gateways (9)(10)(11)(12)(13)(14). The paucity of low-latitude data, especially in the Pacific Ocean, prevents the reconstruction of the latitudinal temperature gradient, much needed for the successful modeling of processes that drove the greenhouse to icehouse transition (10, 15, 16).…”

Climate sensitivity and meridional overturning circulation in the late Eocene using GFDL CM2.1

“…The cooling-induced weakening of the hydrological cycle does bring the North Atlantic closer to a regime of deep water formation, but these changes of 1-2 psu are not enough to trigger sinking. If we hypothesise that NADW did form at the EOT (Borrelli et al, 2014), then other mechanisms are needed to first raise the control state salinities in the North Atlantic. 20…”

“…This has been used to infer a predominance of southern hemisphere high-latitude 5 deep-water formation. Subsequent divergence of inter-basin benthic isotopic gradients creating oceanic heterogeneity has been linked to onset of North Atlantic intermediate water formation in the late Eocene, and the beginning of a more mature North Atlantic deep water formation in the early Oligocene (Borrelli et al, 2014). In those studies, the proposed forcing mechanism of North Atlantic deep water is the opening of Southern Ocean gateways.…”