Sunday, June 29, 2014

Misconceptions About Antarctica Ice

Deniers keep citing evidence of increasing sea ice around Antarctica as evidence that global warming is not real. So, let's review the facts.

Antarctica sea ice is increasing. Take look at this plot:

Source: NSIDC

This shows the annual extent of sea ice in May every year up to this year (the last complete month). Keeping in mind the seasons are opposite in the south, this represent the ice extent as the region is approaching the heart of winter. You can see that there is a trend of increasing ice and this last May, (the last plus mark on the right) was the highest ice extent ever recorded.

At this point deniers are going, "See, we told you so!" and this would be just one more example of how deniers ignore anything they don't want to see.There are major differences between the Arctic and the Antarctic. See a discussion about this from NSIDC here.  Among those differences are the circumpolar currents in the atmosphere and the oceans that isolate Antarctica and make it a unique environment. Another difference is even bigger - land ice. Deniers conveniently ignore the fact that Antarctica is the largest reservoir of land ice in the world. What is going on with the land ice?

The reality is that Antarctica is losing ice in large amounts. One of the reasons sea ice is increasing is because it is coming from the land ice that is sliding into the ocean. Evidence indicates Antarctica is losing land ice at a rate of over 100 billion tons a year. That is enough to raise the sea level in excess of a millimeter per year. That may not sound like much, but in ten years that amounts to a one-centimeter rise in world sea levels and that does not include other sources of sea level rise.

A NASA/ESA study incorporating more satellite data than past studies confirmed that both Greenland and Antarctica are losing ice mass.

The loss of land ice is increasing and it was recently determined that the massive West Antarctica Ice Sheet has reached the point of no return. Even if we stopped emitting greenhouse gases today, the ice sheet will still melt.

The evidence is conclusive; the total amount of ice in the Antarctic region is decreasing, not increasing.

So, if deniers want to talk about ice in the Antarctic region, make sure they include the land ice. It's a very different story when you do.

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