We all know that there is so much water locked up in the ice of Greenland and Antarctica that if it melted it will cause serious flooding. In all the large figures of sea level rise it should be remembered that just one metre rise will bring massive economic losses for every country with a shoreline.
There are two big ice sheet regions, Antarctica and Greenland. Antarctica is split in two with East and West and we can ignore East Antarctica which is so high and cold it is not melting yet. This leaves West Antarctica which has enough ice to raise sea levels 4.8 meters and Greenland which has enough ice to raise 7.5 meters, they are both completely different and both of them have melted completely in the distant past.
There are two big ice sheet regions, Antarctica and Greenland. Antarctica is split in two with East and West and we can ignore East Antarctica which is so high and cold it is not melting yet. This leaves West Antarctica which has enough ice to raise sea levels 4.8 meters and Greenland which has enough ice to raise 7.5 meters, they are both completely different and both of them have melted completely in the distant past.
Greenland is a high rocky island which has ice on its surface that is two kilometres thick and has glacier tails that sit in the sea, Its vulnerability is that its surface melts in the summer and when it does so the dark blue water absorbs more of the sun’s heat than white ice and this warmer water melts into the ice and eventually makes a hole that will carry a whole lake of warm water into its interior.
Not much is known about where this warm water goes but the concern here is that the increasing number of holes in the ice and the amount of warm water in the interior are weakening the ice sheets core which will become rotten and vulnerable to catastrophic collapse. There are many elements to Greenland’s ill health, including the amount of soot on the surface that speeds melt and also the increasing speed of glaciers heading to the sea. All in all Greenland is not in good shape.
West Antarctica has a different set of problems in that it is a string of islands that are covered in a huge sheet of ice but much of this ice is sitting on the sea bed. The concern here is that the sea water is warming and washing around the bottom of the ice and melting it rapidly. Water has a thermal conductivity that is 24 times greater than air so it has a greater capacity to melt ice quickly and the ocean water is warming.
Two East Antarctica ice sheets have broken off and collapsed already but these were floating in the sea and did not add much to sea level rise but they did demonstrate the vulnerability of West Antarctica. The warmer water has been measured at melting 50 mm of ice a day which may not seem much if the ice is 1000 metres thick but it weakens the sheet and then storm waves can break the sheet which then collapses.
The problem in forecasting a sudden collapse is working out the mechanism of how it happens and then putting a timescale to it. There are precedents in the recent past when sea level rose at 10 mm a year compared with the current 3.6mm a year. At 10mm a year or 100 mm every ten years or one meter in 100 years we could see some serious consequences with inundation of major cities and infrastructure but a sudden ice sheet collapse could bring this foreword in an irregular timescale.
The problem in forecasting a sudden collapse is working out the mechanism of how it happens and then putting a timescale to it. There are precedents in the recent past when sea level rose at 10 mm a year compared with the current 3.6mm a year. At 10mm a year or 100 mm every ten years or one meter in 100 years we could see some serious consequences with inundation of major cities and infrastructure but a sudden ice sheet collapse could bring this foreword in an irregular timescale.
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