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West Antarctic Ice Sheet: Why worry? · PDF file West Antarctic Ice Sheet: Why worry? The WAIS...

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  • Recent Global Environmental Change

    Ice and climate: a view from spaceWest Antarctic Ice Sheet: Why worry?

  • Recent Global Environmental Change

    Ice and climate: a view from space

    • This lecture – Why worry? – Ice sheets and marine ice

    sheets – The southern ocean – The Amundsen Sea and

    Pine Island Glacier

    West Antarctic Ice Sheet: Why worry?

    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: a view from spaceIce sheet 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

    Ice and climate: a view from space

    East Antarctic Ice SheetWest Antarctic Ice Sheet

    West AntarcticaWest Antarctic Ice Sheet: Why worry?

    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 and destabilisation. This can be seen in this cross section of the two ice sheets

  • Recent Global Environmental Change

    Ice and climate: a view from space

    Continental

    Marine

    West Antarctic 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

  • Recent Global Environmental Change

    Ice and climate: a view from space

    Continental

    Marine

    West Antarctica

    Submarine sectors are unstable to retreat if ice

    shelves are eroded

    West Antarctic Ice Sheet: Why worry?

    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.

  • Recent Global Environmental Change

    Ice and climate: a view from space

    Joughin GRL 2003 Rignot, Science, 1998

    • Amundsen Sea sector drains 40 % of the WAIS and has deflated by 7 cm yr-1

    • Drained by the Pine Island, Thwaites, and Smith glaciers all of which has accelerated by up to 20%

    • 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

    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 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

    WAIS

    Weddell Sea

    Amundsen Sea

    Ross Sea

    Pine Island: The weak underbelly of The WAIS?

  • Recent Global Environmental Change

    Ice and climate: a view from space

    Melting triggered by Ocean currents BindschadlerBindschadler

    PostPost

    Sub-glacial geothermal heating

    Surging behaviour

    Huybrechts

    Long term deglaciation trend from the Last Glacial Maximum

    Internal

    ShepherdShepherd

    External

    West AntarcticaPine Island: The weak underbelly of The WAIS? Four potential hypotheses have been put forward to explain these observations. These can be classed as internal or external drivers of ice sheet change

  • Recent Global Environmental Change

    Ice and climate: a view from space

    Recent Global Environmental Change

    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 Embayment

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