Middle Miocene-Pliocene ACE subcommittee

Rationale:

The middle-to-late Miocene period represents a time of significant ice sheet expansion in Antarctica. The sea stable isotope record shows a mid-Miocene “climatic optimum” centred at about 15 Ma, followed by strong enrichment of oceanic d 18 O over the next 6 Ma. It is during this interval that East Antarctic glacial ice is thought to have evolved into a major and permanent ice sheet. The Pliocene Epoch is a critical time for understanding the nature of the Antarctic ice sheet as IPCC projections of global temperature rise suggest that we will exceed Pliocene levels within the next hundred years. Of key importance in this time interval is the timing of the transition of the EAIS from a polythermal, dynamic condition to a predominantly cold stable state. Two opposing and vigorously defended views prevail. The long-standing view is that the EAIS became stable in mid-Miocene time, evidence of which is primarily from the longevity of the landscape and well-dated surfaces and ash deposits in the Dry Valleys region along the western border of the Ross Sea. Another controversial view is that terrestrial glacial deposits, known as the Sirius Group, scattered through the Transantarctic Mountains, indicate dynamic ice sheet conditions as recently as Pliocene time. The Mid Miocene and Pliocene ACE sub-committee will facilitate Antarctic and global environmental research investigating:

• The period of middle Miocene cooling
• The period of late Miocene cooling
• Pliocene warm periods
• The Pliocene - Pleistocene transition (working jointly with the Pleistocene sub-committee).

Focus:

In particular the committee will co-ordinate and input relevant research activities for the Neogene from the British Antarctic Survey core programme GEACEP (Greenhouse to Ice-house Evolution of the Antarctic Cryosphere & Palaeoenvironment). These efforts will include:

• New data acquisition from the Ross Sea region as well as the Antarctic Peninsula in general.
• Data synthesis of global proxy climate and environmental data for the Mid Miocene, Late Miocene, Pliocene and the Plio-Pleistocene transition.
• Earth System Modelling studies for the Mid and Late Miocene cooling, Pliocene warming and the Plio-Pleistocene transition.

Committee:

Alan Haywood (chair, UK); John Smellie (UK); Allan Ashworth (USA); Paul Valdes (UK); Sandra Passchier (USA); Carrie Lear (UK); David Cantrill (Sweden), Fabio Florindo (Italy), Roderik van de Wal (the Netherlands) .

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