Enough of the elections already.  The big lecture of the week was visiting professor Rob DeConto talking about climate change and its effect on the Antarctic ice cap.  Looking ahead 500 years proved to be more important than looking ahead to the next election cycle.

Sea level rise is beginning to accelerate.  More melt-water is coming off the ice caps of Greenland and Antarctica  In the Southern Ocean relatively warm water is hitting the Antarctic ice cap.  A loss of the glacial ice from Greenland will lead to a rise of sea levels to 7 metres, the West Antarctic Ice sheet 4 metres, East Antarctica 50 metres.

There’s not much action on the East Antarctican front yet.  There was a week in July 2012 when the entire Greenlandic Ice sheet was above freezing point.  It was effectively raining in a dry land.  Greenland is a robust ice sheet that survived the last inter-glacial period.  The mass of the Greenland Ice sheet is dense enough to pull water to it.  The loss of water from Greenland won’t affect the surrounding North Atlantic coast line, from Newfoundland to Northern Ireland and Scotland.  Instead, further away, in the South Atlantic will be most affected.

Likewise the Antarctic melt-off won’t be felt in the Southern Ocean.  It will be felt in the mid-Pacific gyre.  The West Antarctica melt affects North America, centring on Washington DC.  Scientists call this the Karma effect!

Most of West Antarctica is sitting on bedrock below sea level.  It is sensitve to ocean temperature.  Ice flows down, off the ice cap, to the ocean.  Where it flows of the West Antarctica into the Ross Sea and the Weddell Sea the ice shelf is buttressed by the limits of the land that encloses it, and obstacles that it encounters, like sea mountains.  Warm water thins the buttressing and the ice flows faster into the ocean.  At the ice shelf’s edge it calves off into ice bergs and floating sea ice.

If the Ice sheet is not buttressed it loses mass.  The edge begins to float and the grounded ice sheet moves back.  The ice cap rests in a bowl of bedrock that is above sea level.  The slope of the ice sheet mirrors the slope it is grounded on the bed of the continental shelf.

The last time carbon emissions in the atmosphere is as high as they are now was during the Plyocene period three million years ago.  During that period there was no West Antarctic ice sheet and sea levels were 20 metres higher then the current Holocene period.  See I’m back to reporting on climate change again!

It turns out that as well as the underwater basin in the West Antarctic ice sheet that there are deep basins in East Antarctica, and these are the thickest parts of the East Antarctic ice sheet.  The grounded ice sheet cannot contain its own weight.  Floating at 100 metres above the sea the Ice cliff will break up under its own weight.  Ice cliff failure will retreat the ice sheet until its supporting weight will re-stabilise. 

We are beginning to see melt water on the Ross ice shelf, standing water above freezing point.  Eventually vulnerable basins in East Antarctica will show the same warning signs.  It will take 500 years for Antarctica to reveal its new coast-line.  However our ‘business-as-usual’ policy towards carbon emissions shows that we are on schedule.  By the end of the century we will see sea rises of 1-2 metres, and an encroachment on our coasts that will be measured in centimetres per year, not millimetres as it currently is.  Coastal properties may not be a good investment.

Warning: sea levels can rise quickly making the return trip difficult and dangerous.

Antarctica showing ice sheets sitting below sea level marked in blue

Antarctica showing ice sheets sitting below sea level marked in blue

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