Thursday, March 6, 2014

The Mulaka

Start slow and continue tapering down” - John “The Penguin” Bingham

Many aspects of climate change are complex. One which is not is the annual melting of the sea ice in the arctic. When the vernal equinox (March 20th this year) turns on the 24hour sunlight at the north pole the sea starts to heat, and the ice slowly starts to melt. If the atmosphere holds in more of the sun’s heat then more of the sea ice melts. Shortly before the equinox the warming breath of the coming dawn slows the accumulation of sea ice. The autumnal equinox in September will turn off the sun, and the maximum extent of ice melt will occur within a few days of this event.

Even the generation of a record arctic sea ice melt is not too difficult to describe. Start with a smaller amount of ice, and then melt it fast.

Today the arctic sea ice may be at its maximum extent for 2014. If not today then the maximum will most likely occur in a couple days time. It will be very near to today’s value of 14.627 million square kilometers of sea ice. The arctic sea ice coverage kind of slumps into the maximum; it is not a sudden freezing spike.

Minimum and Maximum Arctic Sea Ice by year.  2014 minimum (circled) is speculative.

One of the reasons that the arctic sea ice is such a nice data set for examining the effects of climate change is that the arrangement of ice floating on water buffers the impact of transient weather events. The arctic is known for its wild and crazy storms, but the Arctic Ocean is voluminous and patient. The transient storms blow over and the constant warming by sunlight and infra-red reflection steadily warms the ocean until the ice melts away.

Another reason why the maximum extent of sea ice in the Arctic Ocean occurs at a time of minimal variation is that the geography of the arctic limits how much ice can be formed. The Arctic Ocean can be viewed as a bottle with two spouts; one for the outlet to the Atlantic, and the other at the Bering Strait. Sea ice buildup ends at the shore. Late in the sea ice buildup season the margin available for expansion is constrained, and even significant expansion of that margin results in only small increases in overall sea ice. Similarly major deviations in the diameter of sea ice extent would only show up in the data as relatively small differences in overall sea ice.

Daily variation in Arctic Sea Ice extent in millions of square kilometers per day.   

Here is a very random example to illustrate the effects of geographic constraint on maximum sea ice extent data. Picture a Yamaka maker who decides, for the sake of fashion, to increase the size of his Yamakas every year. The arctic sea ice is like a giant ice yamaka for the planet. At first he has to buy significantly more material for each fashionably larger yamaka; the amount of material in a circular yamaka is proportional to the square of the diameter of the yamaka. Early on in the freezing season the Arctic ice can expand without constraint. Then the yamaka maker finds he needs to make the yamakas with cutouts for the face and ears. The arctic ice expansion is limited by the northern shores of Russia and Canada. Eventually each new year’s more fashionable yamakas are mullet shaped, with only slightly longer strips running down the neck or framing the face like fabric sideburns. The amount of new material required per yamaka each year is now only linearly proportional to the length of the mullet and sideburn strips; even large increases in overall diameter of yamaka only requires small amounts of material.

I don’t know if the preceding description was actually illustrative or if I just wanted to introduce the concept of a mullet-shaped yamaka. I think I will call it “The Mulaka”. I am not sure, however, how well this will work with alternative definitions for the word “Mulaka”

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