The Antarctic ice sheet and rising sea levels

A slight warming of water beneath the Antarctic ice shelves can speed the flow of ice to the ocean and accelerate rising sea levels, says a prominent geophysicist who will give a free public lecture on the topic on May 20.

To be delivered live by video-link on May 20, the annual S T Lee Lecture in Antarctic Studies will present recent scientific discoveries relating to the ways in which the Antarctic ice sheet is responding to global warming.

Pennsylvania State University Professor of Geosciences Richard Alley will speak live to an audience at the Ilott Theatre at the Wellington Town Hall at 12.30, after which will ensue a panel discussion between Victoria University climate change researchers.

Professor Alley's lecture, titled Through a Crevasse Darkly: An Update on the Future of the Antarctic Ice Sheet, will describe the recent and rapid changes to the ice sheet and how these have dispelled the comfortable view of a "coldly aloof Antarctic ice sheet largely ignoring changes in its surroundings."

Professor Alley says that scientific advances show the elements of Antarctic ice cover are surprisingly sensitive to warming and could accelerate sea-level rise. He says that even slight warming of water beneath ice shelves can speed ice flow to the ocean, as can puddling of melt-water on top of ice shelves to wedge open crevasses.

He says that in the "warmer distant past tens of millions of years ago the whole ice sheet was smaller and more dynamic, but even as recently as 3-5 million years ago new geological records indicate a notable reduction or disappearance of the smaller West Antarctic Ice Sheet when global average temperature was only 2-3ºC warmer than today.

"Yet, translating these new results into useful predictions remains difficult, with no consensus on whether future changes in the ice sheet will be fast enough to matter to modern policymakers."

Regarding a statement by the International Panel of Climate Change—"understanding...is too limited to...provide a best estimate or an upper bound for sea level rise,"—Professor Alley says that, "fortunately, that understanding is coming, and useful projections may become possible soon."

An interview with Professor Alley previewing the lecture can be heard at: http://www.radionz.co.nz/podcasts/ourchangingworld.rss