Sea ice gains in Antarctic do not cancel out losses in Arctic

13 02 2015

More on Climate Change from our resident climate scientist Mark Cochrane…….

Sea ice cover in the Arctic has now been clearly dropping for several decades now. This is why we have the recent rush for riches to drill the Arctic for oil. You can now sail a tanker across the top of Siberia to China in the summer and the window of time when the area is ice free is only expected to increase in coming years. Summers may be ice free before the decade is out.

Despite this phenomenal change in the planet’s ice cover (where do we tell kids Santa lives?), you will also hear that sea ice is increasing around Antarctica being mentioned as if it somehow made the Arctic losses unimportant. While it is true that winter gains in sea ice have been occurring in the Antarctic region, the causes are completely different and probably not comforting. The Arctic is a floating ice sheet surrounded by land. The Antarctic sea ice surrounds a continent of land covered in ice.

Why is this distinction important? The ice sheets covering Antarctica are melting, with the western Antarctic ice sheet now past the point of return. It will collapse into the sea and melt no matter what we do (link). Ice that melts off the continent pours fresh water into the oceans making the surface waters less dense than the existing sea water. Being less salty, it also freezes more easily. This, combined with changing wind patterns that move the ice out further from the continent, is likely causing the slight increase in sea ice cover (link). Though part of the increase might just be an artifact in how the satellite data are now being processed (link).

However, for those who are unconvinced by such arguments, we can simply compare the area of ice being lost in the Arctic to that being gained in the Antarctic to see just what the balance in total area of ice cover change has been. A recent paper (Parkinson 2014) shows these relative trends in the Arctic and Antarctic and their magnitudes for the 35 year period; 1979-2013.

All 12 months show negative trends over the 35-yr period, with the largest magnitude monthly trend being the September trend, at −68 200 ± 10 500 km2 yr−1 (−2.62% ± 0.40% decade−1), and the yearly average trend being −35 000 ± 5900 km2 yr−1 (−1.47% ± 0.25% decade−1).

That annual area of global sea ice cover being lost (35,000 km2) is larger than the state of Maryland  (or nearly Taiwan if you prefer). Clearly the increasing seasonal sea ice cover in Antarctica is not ‘canceling out’ the severe sea ice losses in the Arctic.

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7 responses

13 02 2015
davekimble3

“you will also hear that sea ice is increasing around Antarctica being mentioned as if it somehow made the Arctic losses unimportant.”

This needs some substantiation with quotes, otherwise it is just a straw man argument.

Sea ice is one thing, ice is another. How much sea ice loss per year, compared to the world total of ice? Would volume would be a better measure than area ?
Comparing it to Maryland or Taiwan is a bit pointless for us. It is less than a half of one percent of Australia.

13 02 2015
mikestasse

Make no mistake DK, climate deniers are quoting the Antarctic sea ice increase as proof nothing’s wrong…… you obviously lead a sheltered life up your way!!

18 02 2015
Firwik Howlo

The graph clearly shows that it is a steady decline in sea ice. This has absolutely nothing to do with land ice and that point is highly irrelevant. As stated in an article by Nasa, (http://www.nasa.gov/content/goddard/nasa-study-shows-global-sea-ice-diminishing-despite-antarctic-gains/#.VOQBxS6uS1t), Sea ice is highly reflective while water is absorbent. This causes more of the Suns rays to be kept here on Earth, which is not a good thing. They don’t cancel each other out. It’s simple math to figure that out.

13 02 2015
Dr Bob Rich

This is what I have been explaining to doubters for some time. Another aspect is that area of ice needs to be multiplied with average thickness. Much of the Antarctic ice spread, which is glacier runoff, is quite thin compared to old ice. It’s the total volume that indicates what’s happening.

14 02 2015
rabiddoomsayer

That Arctic Death Spiral is just a little scary. Give it thirty years and we may lack winter sea ice in the Arctic, then where will all the heat that currently melts the ice each year go?

14 02 2015
Dr Bob Rich

You don’t have to worry about 30 years. I’ve read predictions that the Arctic could be free or ice as soon as the northern summer of 2016.

And there is tremendous positive feedback with the methane release.

Mark, has there been any modelling on the likely effects of that interaction?

🙂
Bob

10 02 2016
rabiddoomsayer

2016 +/- 3, was Maslowski’s prediction for an effectively zero minimum. This still looks on the money. Looking at the trends we could be looking at a zero maximum in thirty years, ie no ice summer or winter, on most winters.

What will warm rain do to the Greenland ice sheet, that is if the warm oceans have left any of it?

The argument that the Arctic ocean has always vented methane is probably true. However, it does appear the venting has increased and the prior ice cover trapped the methane giving microbes time to consume the methane.

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