Monitoring lake ice

In northern Alaska, within the Arctic circle, the ice regimes of shallow lakes were documented using 79 radar images from the ERS-1 and -2 satellites. How the radar signals bounced back to the sensor indicated ‘floating ice’ versus ‘grounded ice’ (fully frozen lake) when radar energy was absorbed into the ground. The data showed that from 1992 to 2011 the lakes in this region experienced a 22% reduction in grounded ice – the equivalent of ice thinning by 21–38 cm.