Greenlands contribution to sea level rise


The Greenland Ice Sheet is melting! Summers last longer and new temperature records trigger enhanced surface melt: huge pools filled with meltwater and raging rivers stand out on the white ice sheet. In addition, more and more ice masses are draining - faster and faster - via the outlet glaciers at the edge of the ice sheet. This means that larger amounts of freshwater from the Greenland Ice Sheet get into the ocean - which makes a decisive contribution to sea level rise ...

Figure 1: Global sea level rise and the contributions of individual components and regions (from Rietbroek et al, 2016). The dark green curve shows the contribution from Greenland.

Figure 2: Cumulative mass loss of the Greenland ice sheet over the past few decades and its sea level equivalent (from IPCC AR5 2013, Chapter 4).

Sea level rise

More than a quarter of the global rise in sea level is caused by the mass loss of the Greenland ice sheet  [1,2,3] (Figure 1). For the period between 1992 and 2011, the Greenland ice sheet's share of sea level rise is around 7.5 mm, with the mass loss of Greenland glaciers quadrupling between the 1990s and the 2000s [4]. During the last decade in particular, this loss of mass has accelerated sharply [5,6,7] (Figure 2).

Other effects of glacier melt

In addition to the increasing contribution of the Greenland ice sheet to sea level rise, the increased input of fresh water (i.e. "sweet" meltwater without salt content) into the ocean also has consequences for the climate-relevant basin-wide ocean currents [8,9,10,11]  In addition, the Greenland meltwater transports a significant amount of biologically relevant substances into the ocean due to the microbial activity at the boundary layer between the glacier and the rock. For example, micronutrients [12] or dissolved nitrogen [13] are increasingly being carried into the ocean - with consequences for biological productivity and thus the fish population on the coast of Greenland that have not yet been researched.

The reasons

So what is known about the causes of this accelerating mass loss of the Greenland Ice Sheet? The 5th assessment report of the International Panel on Climate Change, IPCC AR5, points out that the increasing contribution of the large ice caps to global sea level rise since the 1990s is linked to the warming of the surrounding oceans [14]. In fact, the largest increase of glacier mass loss is observed close to the ice-ocean interface, at those glaciers that are increasingly retreating, whose flow velocity is increasing rapidly, and those which are substantially thinning [15,16,17,18,19]. Here you can find more information on this topic.