My Problem with Sea Ice Extent

Since 1979 there is a sea ice extent record for the Arctic with mostly daily measurements. The trend is clear and down, so what is the problem?

Imagine a single idealized ice floe: 1 kilometer long and 1 kilometer wide with a thickness of 2 meter drifting in the Arctic Ocean - a pretty flat cuboid. Roughly 20 centimeter are visible above sea surface as freeboard. NASA’s Arctic Mosaic at highest resolution would represent the floe with 16 white pixels arranged as square.

Let’s further assume bottom- and top melting are equal and and there is enough energy available to melt 1 meter of ice from each of the six sides within a month (30 days). How much ice is left after this period? Exactly, zero.

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New CryoSat Data: 3,000km³ loss between latest Winters

Good timing: Between a storm that took one million km² within one week from extent and the next record low the UCL finally releases long awaited concrete numbers from the CryoSat 2 Mission. The take away message is the trend strongly indicates an ice free Arctic around 2020. That fits nicely to the PIOMAS trend in this chart. The broader picture is within one generation (30y) we will have removed more than 6 million km² from Earth's reflecting September ice shield.

Here's an interesting BBC Radio interview with Seymour Laxon of the Centre for Polar Observation and Modelling:

And here an excerpt from the Guardian:

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Sea Ice Thickness Forecast by TOPAZ 4

The Operational TOPAZ4 Arctic Ocean system uses the HYCOM model and runs every week to provide 10 days of forecast (one single member) and 7 days of analysis (ensemble average) for the 3D physical ocean, including sea ice. More Arctic related scientific products are available at the MyOcean website. Registration is free.

The MyOcean project is funded under a European Commission 7th Framework Programme and is planned to continue at least until end of September 2014

Now is the time with most top and bottom melting. Recognize the upcoming Swiss Cheese effect after the break. The colors range from 0 to 3 meters, black is above.

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Hudson Bay Break Up

In May 2005 NASA's Earth Observatory reported:

With the coming of spring, the ice on Canada’s Hudson Bay has begun to break up. Large chunks of ice float near the eastern shore of the bay, while to the west, the center of the bay remains frozen.

Earlier this month a similar photo was taken by the Aqua satellite. I leave it as an exercise to visitors to decide which of the above megapixel zooms was taken 2005-05-21 or 2012-04-06. It seems the thin ice can not withstand usual April weather any longer. At least the Chukchi Sea tells ...

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Sea Ice Thickness Forecast

Just out of curiosity I wanted to know what the average sea ice thickness in the Arctic actually is. So I took the available GSFC Dataset, filled the holes and used the overlapping time range with the IJIS/JAXA data set to perform a least error approach and gained a table starting 1979-01-01 and ending 2010-12-31. This range is also covered by the PIOMAS sea ice volume data set and calculating daily thickness was easy then.

But average thickness is a value which works only within a certain range. Having an average of zero, does no way mean there are any floes with negative thickness. Also, it turns out yearly thickness minimum is not in September, but rather in December when the Arctic is covered with a lot of fresh and thin ice.

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