Surface lakes on Greenland will spread further inland as the climate warms

Abstract

Each summer, a rash of lakes forms from ponded meltwater on top of the Greenland ice sheet. These 'supraglacial' (on top of ice) lakes can drain through the ice sheet, delivering their contents to its base. The ice sheet slides on a thin film of water, and when extra water is added to this film (for example from a draining supraglacial lake) the sliding (‘flow’) happens a bit faster. At present, under-ice pipe-like features enable excess water to drain out from under the ice sheet quickly and efficiently. However, in recent years supraglacial lakes have begun to form further inland, potentially supplying water to the base beyond the reach of these features. Here, we use a computer simulation of lake initiation and growth to show that the inland spread of supraglacial lakes will continue as the climate warms; by 2060, 100% more of South West Greenland and 50% more of the whole ice sheet will be populated by supraglacial lakes. Of these ‘new’ lakes, up to half will be large enough to drain, delivering the water they contain to the base of the ice sheet and all of these new lakes will form at locations where we would expect to see an ice sheet speed-up with the addition of more water at the base. If the ice sheet flows faster, it can thin out and melt quicker, thus contributing to global sea level rise. Supraglacial lakes and their impacts are not currently considered in our best predictions of future ice sheet change. Given that they possess significant leverage to affect ice sheet flow, and that they are likely to form (and drain) at locations more sensitive to their impact in future years, it is clear that they need to be accounted for in these predictions as a matter of priority.