The margin of the Greenland ice sheet moves back and forth depending on the climate. During cold times, like the ice ages, the ice margin advances and covers the land and may even form ice shelves extending into the ocean. In a warming climate, the ice margin retreats, revealing freshly exposed land, which is darker than the ice, therefore absorbing more heat from the Sun.
The quantity of meltwater is not directly affecting the mass balance but is rather a product of it. However, it is still of interest to PROMICE, since it can possibly alter the ocean dynamics around Greenland. Furthermore, it’s an important energy source in Greenland, providing hydropower to remote societies. For instance, the Watson River at Kangerlussuaq, southwest Greenland, has been monitored by pressure transducers at the local bridge since 2006. The Watson River drains an ice sheet area of about 12,000 km2 (Lindbäck et al., 2015) and a 590 km2 proglacial area (Hasholt et al., 2013). During the peak of the melt season, large amounts of water and sediment are transported by the river, but during the cold season the river falls dry.