Atmospheric and oceanic impacts of Antarctic glaciation across the Eocene–Oligocene transition

Kennedy, Alan, Farnsworth, Alexander, Lunt, Daniel, Lear, Caroline Helen ORCID: https://orcid.org/0000-0002-7533-4430 and Markwick, Paul 2015. Atmospheric and oceanic impacts of Antarctic glaciation across the Eocene–Oligocene transition. Philosophical Transactions of the Royal Society A: Mathematical Physical and Engineering Sciences 373 (2054) , 20140419. 10.1098/rsta.2014.0419

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Abstract

The glaciation of Antarctica at the Eocene–Oligocene transition (approx. 34 million years ago) was a major shift in the Earth’s climate system, but the mechanisms that caused the glaciation, and its effects, remain highly debated. A number of recent studies have used coupled atmosphere–ocean climate models to assess the climatic effects of Antarctic glacial inception, with often contrasting results. Here, using the HadCM3L model, we show that the global atmosphere and ocean response to growth of the Antarctic ice sheet is sensitive to subtle variations in palaeogeography, using two reconstructions representing Eocene and Oligocene geological stages. The earlier stage (Eocene; Priabonian), which has a relatively constricted Tasman Seaway, shows a major increase in sea surface temperature over the Pacific sector of the Southern Ocean in response to the ice sheet. This response does not occur for the later stage (Oligocene; Rupelian), which has a more open Tasman Seaway. This difference in temperature response is attributed to reorganization of ocean currents between the stages. Following ice sheet expansion in the earlier stage, the large Ross Sea gyre circulation decreases in size. Stronger zonal flow through the Tasman Seaway allows salinities to increase in the Ross Sea, deep-water formation initiates and multiple feedbacks then occur amplifying the temperature response. This is potentially a model-dependent result, but it highlights the sensitive nature of model simulations to subtle variations in palaeogeography, and highlights the need for coupled ice sheet–climate simulations to properly represent and investigate feedback processes acting on these time scales.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	Q Science > QE Geology
Publisher:	The Royal Society
ISSN:	1471-2962
Funders:	NERC, Getech
Date of First Compliant Deposit:	30 March 2016
Date of Acceptance:	4 August 2015
Last Modified:	30 Nov 2024 01:15
URI:	https://orca.cardiff.ac.uk/id/eprint/77806

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