by Liz Kalaugher
The larger the area of melt ponds on Arctic sea ice in May and early June, the smaller the sea ice coverage will be the following September, Daniella Flocco of Reading University, UK, reported at the European Geosciences Union (EGU) meeting in Vienna. In fact, the relationship is strong enough to make a skilful forecast of September sea ice cover, as Flocco, Reading colleague Daniel Feltham and other team members recently published in Nature Climate Change. It seems that melt ponds reduce the albedo of the ice surface, leading to greater heat absorption and more melting.
Now the team has moved onto the next problem, Flocco explained, namely trapping of melt ponds in the autumn as ice freezes above them. The phenomenon is invisible from the air but the latent heat released as the trapped melt pond freezes delays thickening of the ice layer into the ocean below.
Ignoring trapped melt ponds could cause models to overestimate ice growth in the autumn by around 265 cubic km [figure updated from sq. km, see comments below] over two months, roughly one-quarter of the total ice growth predicted, Flocco has calculated.
From satellite images the researchers estimate that around 20% of melt ponds become trapped as the freeze begins. Ultimately their studies will help them calculate this figure, Flocco and Feltham told environmentalresearchweb at the EGU meeting. Typically ponds remain trapped for a few months under thin lids of ice, becoming increasingly salty; the team plans to investigate this further.