[Bolincentret-at-su.se] Zhonghui Liu seminar 7th May 15:00

[David Hutchinson]

A reminder of the Brøgger seminar by Zhonghui Liu on Monday, 15:00 in DeGeersalen.

On 18 Apr 2018, at 14:54, David Hutchinson <david.hutchinson at geo.su.se<mailto:david.hutchinson at geo.su.se>> wrote:

Dear all,

The next Brøgger seminar for the IGV marine geology group will be on Monday 7th May 15:00, in DeGeersalen. The speaker will be Zhonghui Liu, from Hong Kong University. He will present on:

Interhemispheric thermal asymmetry across the Eocene-Oligocene Transition: Implications for the onset of modern-like AMOC

We will go out for dinner on the Monday following the talk. Please let me know by Monday (23th April) if you’d like to join. Zhonghui will be visiting from 7-9 May (Monday to Wednesday). Please contact me if you’d like to chat with him while he’s here.

Regards,
David


Abstract
The Eocene-Oligocene Transition (EOT) around 33.7 million years ago (Ma) is arguably one of the most puzzling climate events during the Cenozoic. The EOT is marked by substantial climatic and oceanic reorganizations as demonstrated in numerous studies, yet the chain of processes or associated driving mechanisms remain controversial. Recent studies have focused on the early Atlantic Meridional Overturning Circulation (AMOC) development and a potential role it played for the EOT. Here we present some new results that are generated from IODP Expedition 342 Sites U1404 and 1411. A long time-series sea surface temperature (SST) record from U1404, from 43 Ma to 18 Ma, demonstrates a much warmer climate in the mid-latitude North Atlantic than today and an overall pattern of change similar to the global benthic d18O record. However, an important anomaly is observed across the EOT, where we see no substantial cooling associated with the earliest Oligocene glacial maximum (EOGM), in contrast to published data from the mid- to high latitudes of the southern hemisphere. The distinct interhemispheric thermal asymmetry documented may signal the onset of strong AMOC. Our preliminary work from Site U1411 shows pCO2 decline since ~34 Ma, perhaps in two steps as shown in benthic d18O (Coxall et al., 2005, Nature) but not resembling SST changes in the mid-latitude North Atlantic across the EOT. Based on our present data, the role of early AMOC development, i.e. during the Late Eocene, for the EOT remains uncertain. We surmise that pCO2 drawdown, as previously proposed, might be the ultimate cause for the EOT, while the transient nature of interhemispheric thermal asymmetry since the EOGM may have resulted from combined effects of Antarctic glaciation and Southern Ocean gateway opening.

<Brogger2018_Zhonghui_Liu_A4.pdf>




Dr David Hutchinson
Postdoctoral Researcher
Bolin Centre for Climate Research
Stockholm University
10691 Stockholm, Sweden
david.hutchinson at geo.su.se<mailto:david.hutchinson at geo.su.se>
dkhutch.github.io<http://dkhutch.github.io/>



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