by Jennifer Coote
Introduction
A Ananathaswamy, New Scientist, 4 July 09, examines sea level rise and its relation to the melting polar regions. There is no doubt that as the planet warms sea levels will rise, but by how much? and how soon? Ice melt in any other parts of the world save the polar regions will only add about 33 centimetres to sea level. The thermal expansion of the oceans could continue to rise even if all emissions stopped at 450 parts per million, while if emissions continue, expansion could raise levels by 0.5 metres by 2100.The great ice sheets of Greenland and Antarctica hold enough water to add 70 metres to sea level but the speed of melt is uncertain, and data to improve predictions is now crucial. The West Antarctic ice is thinning faster than that of Greenland as melted water pours down crevasses to the base of glaciers, lubricating their descent to the sea. The ice shelves are threatened by upwelling of warmer currents in the Antarctic circumpolar current as climate change and the loss of ozone speeds the current and pushes surface water away from the coast. Another modest change in wind direction caused massive increase in ice breakup in western Greenland in 1997. Current conservative estimates of sea level rise could be 80 centimetres by 2100.(continue…)