Climate Feedback

High Altitude

6a00d8341bf7f753ef01157142a653970c.jpgA new study in Geophysical Research Letters [subscription] adds to the evidence that glaciers in high mountain regions are under threat from climate change.

The research, by Ray Bradley at the University of Massachusetts in Amherst and colleagues, looks at changes in the altitude at which temperature reaches 0 degrees Celsius – known as the freezing level height – in the tropical Andes.

They find that, over the past three decades, freezing level height has increased over most of the region, which is a good indicator that high elevation glaciers are losing mass due to surface melting. Their finding is consistent with observed changes in surface temperature and upper air data in the region, which has experienced a 0.1 degree Celsius increase in temperature per decade over the past half century.

Strikingly, they find that the summit of the Quelccaya ice cap in Peru – the largest body of ice in the Tropics – frequently experiences daily maximum temperatures above freezing between October and May. At the ice cap margin at 5200m, temperatures rise well above freezing for much of the year.

Bradley and co-authors say this phenomenon is likely to be affecting other high elevation glaciers in Ecuador, Peru and Bolivia, with potentially serious implications for the region’s water supply.

Olive Heffernan

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