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Physics Seminar - Andrew Pauling

Tuesday, 22 August 2017

Physics Department

Andrew Pauling

Fulbright Scholar

Department of Physics

"Antarctica, Sea Ice and Ice Shelves in Climate Models"

Sea ice is a thin layer of frozen seawater that covers large areas of the ocean at both poles. Sea ice plays an important role in the global climate system, reflecting large amounts of incoming solar energy. The area of ocean covered by sea ice has large seasonal variability, reaching a maximum, in winter, and a minimum in summer. Averaged over the entire year, Antarctic sea ice area has slightly increased over recent decades, in contrast to the rapid decrease seen in the Arctic. Climate models, our best tools for making predictions about the future of the climate, have been unable to reproduce the trend in Antarctic sea ice. One of the proposed reasons for this discrepancy between models and observations is the unrealistic representation of the Antarctic continent in these models. An important factor that influences Antarctic sea ice is the fresh water entering the ocean due to the melting of ice shelves around the continent. Ice shelves are the floating extension of the freshwater ice sheet that covers Antarctica. Ice shelves melt when relatively warm water enters the cavity beneath them, resulting in large amounts of fresh water entering the ocean. This fresh water then causes sea ice growth by inhibiting the upwelling of warmer water from deeper in the ocean. Climate models do not currently have ice shelves in their representation of Antarctica, and as such this freshwater input is not realistically represented. I will give an overview of Antarctica and sea ice in climate models, and present results of simulations we have run using a state-of-the-art climate model to investigate the effect of adding a freshwater flux around the Antarctic continent to simulate the input from ice shelves. We found that freshwater introduced at a constant annual mean rate has no effect on the trend in Antarctic sea ice area, while linearly increasing freshwater input does cause a reversal of modelled decrease in Antarctic sea ice area over time.

A.G.Pauling¹, I.J.Smith¹, P.J.Langhorne¹ and C.M.Bitz²
¹Department of Physics, University of Otago, Dunedin, NZ
²Department of Atmospheric Sciences, University of Washington, Seattle, USA

WHEN: Tuesday 22 August 2017
WHERE: Room G400, Science 3 Building
TIME: 3.00 pm–4.00 pm

All interested are welcome to attend

Light refreshments to follow in Common Room