Melting Ice - Part 3 - A reason why it is called Greenland?

I always found it confusing as a child that Greenland was called green. I had a big jigsaw with lots of animals on it and crucially lots of snow too. While my jigsaw wasn't entirely accurate - ice sheets don't cover the whole of Greenland, it did give me the impression that there was some ice. But for how much longer?

A little far from home? Possibly the iceberg that sank the Titanic (Wired)

As King of Denmark, Greenland is pretty much Canute's own country - so no doubt it's doing something to the sea level. Greenland is covered in glaciers and ice sheets which fluctuate in size naturally throughout the year. But satellite measurements since the 1990s show that the Greenland ice mass is decreasing - Greenland is losing more ice than it is accumulating (Sasgen et al, 2012). Research by Bates et al (2009) shows that since 1990, as the oceans and the atmosphere around Greenland warm up, the ice on Greenland is moving at increasing rates into the sea. Rather excitingly the iceberg that sank the Titanic originally came fro Greenland. Rignot et al (2005) found that while the ice sheet appears to be stable in the centre, increased run off and glacier flow into the ocean, at the edges of the ice sheet are causing the ice sheet to decrease in mass.  It's exactly the same problem as with the Western Antarctic Ice Sheet, and marine terminating glaciers all over the world - they are being warmed and melted by the relatively warm ocean water - still not warm enough for swimming though!

The NSIDC have produced this graph which shows really clearly that the extent of melting in Greenland this year is generally higher than the 1981 -2010 average. Check out their website for daily satellite images of the Greenland ice melt.

So how is the decreasing Greenland ice sheet affecting sea level? Well, to put it simply, quite a lot. The IPCC released some rather stark figures in their Assessment Report 5:

"Observations indicate that the Greenland contribution to GMSL has very likely increased from 0.09 [–0.02 to 0.20] mm/yr for 1992 - 2001 to 0.59 [0.43 to 0.76] mm/yr for 2002 - 2011."

 

So that's a huge increase in Greenland's contribution to sea level rise over the last twenty years. So what's going to happen in the future?


It has been estimated that the whole of Greenland melting could cause a ~7 metre sea level rise, but it's quite difficult to work out how quickly this could happen. Rignot et al (2005) point out that glacier dynamics are not usually included in the models used to estimate Greenland contribution. The exclusion of these important physical processes will result in an underestimation of how the melting of Greenland's ice sheets and glaciers could affect sea level in the future. Despite these modelling difficulties, Graversen et al(2011) suggest that melting on Greenland could cause global mean sea level to rise by up to 17cm by the end of this century. Price et al (2011) modelled the ice sheet dynamics for the three biggest Greenland glaciers, they then scaled this up for the whole of Greenland and forecast a 45mm sea level contribution by 2100 from dynamics alone.

So Greenland is definitely one to watch for the future, but Greenland melting could have further implications on sea level than just adding water, and icebergs, to the oceans. As the ice sheet and glaciers melt they are adding fresh water to the oceans which can impact on ocean circulation, which in turn can affect regional sea level. But I'll save that for another time.