We hear about Greenland and Antarctica losing XX gigatonnes of ice a year but how big is a gigatonne and what does this do to sea levels?
A gigatonne is a billion tonnes (1,000,000,000 ) and in volume it consists of one billion cubic metres of water. Its actually a cube with one kilometre sides ( 1000 metres x1000 x 1000 )
Even this large measurement is tiny compared to sea level rise and so a handy measurement is 100 gigatonnes will raise the sea level 0.27 millimetres . For Americans this would be a block 5/8 mile wide and 5/8 mile high and 62.5 miles long and your fingernail is about one millimetre thick so you would need four times 0.27 mm to make the millimetre.
Even this large measurement is tiny compared to sea level rise and so a handy measurement is 100 gigatonnes will raise the sea level 0.27 millimetres . For Americans this would be a block 5/8 mile wide and 5/8 mile high and 62.5 miles long and your fingernail is about one millimetre thick so you would need four times 0.27 mm to make the millimetre.
Sea level is increased by a number of different sources including thermal expansion, melting glaciers, and pumping aquifer wells. Up to now thermal expansion has been the largest contributor but it has just been overtaken by melting glaciers and here the major increase has been from Greenland with Antarctica a close second.
Melt rates vary from year to year in any location so the most reliable measurements come from satellites using both the NASA GRACE and the European Space Agency CryoSat and it is estimated that Antarctica now losing 310 gigatonnes a year and Greenland now about 370 gig tonnes a year. Put together these two make 680 gigatonnes and at 0.27 a gigatonne makes 1.8 mm a year and NASA say sea level is rising at the rate of 3.2 mm a year.
The worry is that both regions are accelerating and we only need one metre to bankrupt most economies.
The worry is that both regions are accelerating and we only need one metre to bankrupt most economies.
Using the UK as an example you can see how sea water has inundated the land right around Peterborough with massive loss of farmland and infrastructure plus of corse the devastation if Holland.
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