Thursday, August 6, 2015

Meanwhile, In Greenland...

I have been discussing the Arctic sea ice a lot lately and haven't really mentioned land ice. The reason is pretty simple - there's lots of data on the Arctic sea ice and it is very dynamic up there. There isn't as much data on Greenland and Antarctica and it takes a long time to see a change in either. Having said that, let's take a look at Greenland and see what's going on there.

This is a plot, courtesy of the Polar Portal, showing this year's melt for the Greenland Ice Sheet (GIS):

Source: Polar Portal

The top panel shows the daily GIS mass change since September 2014. The grey line in the middle is the long term average seasonal mass change. The mass increases during the winter as the ice sheet accumulates snow. Then, as the melt season commences (late-May to early-June), there will be some melting and runoff, resulting in a loss of mass. This is to be expected and there is no controversy here. What we want to know is if there is any change in the seasonal process over a period of time. The bottom panel helps answer that question and we can see this year's melt season is significantly below the long-term average. The red line is the melt season for 2012, the disastrous year for ice melt.

So, 2015 is way below average, but you could argue it has 'rebounded' from 2012 and is increasing. Okay, fair enough. Let's take a look of the long term mass balance (again, courtesy of the Polar Portal):

Source: Polar Portal
This clearly shows the total mass balance (i.e., how much ice there is) is not only on a most definite downward trend, but we can see very easily that the rate of loss is increasing. Draw a tangent line for the period of 2003 through 2009. Then, draw another tangent line for the period of 2010 through 2014. The second line will have a much steep slope than the first, meaning the downward trend has been greater since 2010 than it was before that year.

Clearly, things are not going well. We don't need to go any further than this to understand the GIS is melting and it is melting at an ever increasing rate. This is very serious news for climate change and global sea levels. But, if you want more, read this article to see just how bad it truly is. Spoiler alert: It's much worse than we thought.

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