WestIce and climate: Antarctic a view from space Ice Sheet: Why worry? Recent Global Environmental Change Ice and climate: a view from space West Antarctic Ice Sheet: Why worry? • This lecture – Why worry? – Ice sheets and marine ice sheets – The southern ocean – The Amundsen Sea and Pine Island Glacier Mountains close to the grounding line of The West Antarctic Ice Sheet, at the edge of the Ronne Ice Shelf Recent Global Environmental Change Ice and climate:Ice a view sheet from space components • Ice sheet are complex, ice flow is highly variable over the surface, with the fastest flow regions being confined to relatively narrow ice streams that drain the interior ice sheet. Using the internet try and find examples of the following components of the Antarctic Ice Sheets • Slow-flowing interior (circa 10 m/yr) • Fast fowing ice streams (>500 m/yr) • Floating ice shelves • Grounding line Recent Global Environmental Change WestIce and climate: Antarctic a view from space Ice Sheet: WhyWest worry? Antarctica West Antarctic Ice Sheet East Antarctic Ice Sheet Although The East Antarctic Ice Sheet (EAIS) locks up a vast amount of water, The West Antarctic Ice Sheet (WAIS) is grounded well below mean sea level making it far more vulnerable to melting andRecent destabilisation. Global Environmental This Change can be seen in this cross section of the two ice sheets WestIce and climate: Antarctic a view from space Ice Sheet: Why worry? The WAIS is an example of a marine based ice sheet in that although some of it is grounded above modern mean sea level, the bulk of it is grounded well below mean sea level. Estimates vary, but if The WAIS did melt it would contribute between 3-5-5m of SLE Continental Marine Recent Global Environmental Change WestIce and climate: Antarctic a view from space Ice Sheet: WhyWest worry? Antarctica Continental The WAIS is vunerable to destruction due to rapid retreat of the grounding line, especially in areas where due to topography sea water can undercut the ice sheet leading to rapid down draw of the ice sheet. Marine Submarine sectors are unstable to retreat if ice shelves are eroded Recent Global Environmental Change PineIce and Island: climate: The a view weak from space underbelly of The WAIS? Ice shelves flank most of Antarctica: Where warm oceans have access, ice shelves are vulnerable to erosion & collapse as seen recently on the Antarctic Peninsula However; The Amundsen Sea sector has no ice Weddell Sea shelf barrier and is grounded below sea level. Therefore the ocean can get right up to the grounded ice front potentially destabilising the WAIS in this sector • Amundsen Sea sector drains 40 % of the WAIS WAIS and has deflated by 7 cm yr-1 Amundsen Sea • Drained by the Pine Island, Thwaites, and Smith glaciers all of which has accelerated by up to 20% Ross Sea • Ice volume sufficient to raise sea levels by 1.1 m •Recent rapid changes have been noted from satellite imagery over the since the early 1990’s Joughin GRL 2003 Recent Global Environmental Change Rignot, Science, 1998 PineIce and Island: climate: The a view weak from space underbelly of The WAIS?West Antarctica Four potential hypotheses have been put forward to explain these observations. These can be classed as internal or external drivers of ice sheet change Sub-glacial geothermal heating ShepherdShepherd Melting triggered by Ocean currents BindschadlerBindschadler Long term deglaciation trend from the Last Glacial Maximum Huybrechts Surging behaviour PostPost External Internal Recent Global Environmental Change Ice and climate: a view from space Presently the most likely candidate is Circumpolar Deep Water that has been shown to be present in Pine Island Bay. This is potentially warm enough to trigger the rapid response recorded in Pine Island and The Amundsen Sea RecentEmbayment Global Environmental Change.