Thursday, October 08, 2015

Arctic Sea Ice Has Lost Two-Thirds of Its Volume Since 1979


Animated visualization of the startling decline of Arctic sea ice, showing the minimum volume reached every September since 1979, set on a map of New York with a 10km grid to give an idea of scale. As it plays, note the sudden drops in 1992, 1995, 2006 and 2012. Collapses aren't linear (source).

by Gaius Publius

I've written before about Arctic sea ice and how the area encompassed by ice at the end of summer is shrinking. For example, in this piece, which contained this age-of-ice graphic:

Graphic showing that Arctic ice is getting younger and younger. Today there is much less ice in the Arctic that's older than five years. Note also the difference in total extent (click to enlarge).

Now comes information on Arctic ice volume, with a nice animation (see top) illustrating it. Greg Laden has more at his climate science blog. Fascinating reading (italics mine):
Every year the sea ice that covers the northern part of the Earth expands and contracts though the winter and the summer. The minimum extent of the sea ice is usually reached some time in September, after which it starts to reform.

Human caused greenhouse gas pollution has increased the surface temperatures of the earth, as measured on the land at about heat height with thermometers, and on the sea at the surface, mainly with satellites. Warming of the surface has continued apace for several decades, though with some expected squiggling up and down in how fast that is happening.

Greenhouse gas, mainly CO2, causes warming because of its heat trapping properties, and this warming (and the CO2 itself) set in motion a number of feedback systems that either push against warming or increase warming. Most of these feedback systems, unfortunately, are what we call “positive” feedbacks, though they are not “positive” in a good way. They are effects that increase the amount of warming beyond what would happen from just the CO2. One of the biggest global effects is an increase in the amount of water vapor carried by the atmosphere. Since water vapor is also a greenhouse gas, more CO2 -> more greenhouse effect -> more water vapor -> more greenhouse effect.

One of the bad effects of greenhouse warming is the melting of more ice in the Arctic during the summer. On average, less and less ice is left by the end of the melt season in September. Again, this amount squiggles up and down a bit, but it is a persistent downward trend. Since ice reflects sunlight away from the earth, a decrease in ice cover in the Arctic means more warming. This has both regional effects (such as an increase in melting of land-based Greenland glaciers) and a global effect. The regional effect is very important, because this has resulted in a phenomenon known as Arctic Amplification. This refers to the fact that of all the different regions of the earth, the Arctic is warming more than most other regions. The large scale systems of air movement that make up much of our climate, and thus control much of our weather, are shaped and driven in large part by the redistribution of heat form tropical areas (where the sun has a stronger warming effect) outward towards the poles. This redistribution shapes trade wind patterns and determines the location and strength of the jet streams. The relatively warmer Arctic has changed the basic shape and pattern of these major climatic features in ways that have caused significant changes in weather. The drought in California is caused in part by the persistence of a large jet stream meander caused, almost certainly, by Arctic Amplification and other changes in heat distribution in the northern latitudes. Another change is the increase in large scale precipitation events. Here in the twin cities, for example, the frequency of 3″ plus rainstorm over the year has changed from about one every two years to one every year, on average. Rainfall events of between 1 and 2 inches, and between 2 and 3 inches, have also increased.

There are two major properties of Arctic ice that should be considered. One, just discussed, is extent. Extent matters because of its direct effect on albedo, the reflection of sunlight back into space. Less ice extent, caused by warming, means even more warming. The other property is ice volume. Ice volume builds up over time. Thick ice includes ice from previous years that didn’t melt. The system is complex and dynamic, but a healthy Arctic ice ecosystem has a good amount of thick high-volume ice that persists through the melt season and forms the anchor against which annually re-freezing surface ice forms. The less ice volume, the less stable the Arctic Sea ice is, and the more difficult it becomes to reform. Exactly how this effect works depends on exactly which part of the Arctic one is in.

Over the last several decades, the volume of Arctic Sea ice has reduced by something like 80%. This is not good.
There's more, including charts like the stunner below. I'd like to send you there to read the rest.

Arctic sea ice extent, month by month, for the ten most recent years. September is always the summer low. The dark black line shows the average for the years 1981–2010. The dashed line is 2012. When the September low reaches 1 million square kilometers (left scale), the Arctic is ice-free. (Click to enlarge.)

Notice in the text quoted above the relationship between feedbacks, that they piggyback on each other. For example, this one about water vapor: "Since water vapor is also a greenhouse gas, more CO2 -> more greenhouse effect -> more water vapor -> more greenhouse effect." Reduction in "whiteness" also increases the greenhouse effect.

It's Coming, and It Won't Be Linear

By "it," of course, I mean the chaos caused by climate change, both physical chaos and social chaos. The maker of the video at the top puts complete loss of Arctic summer ice in the next few years:
Based on the rate of change of volume over the last 30 years, I expect the first ice-free summer day in the Arctic Ocean (defined as having less than 1 million km² of sea ice) to happen between 2016 and 2022, and thereafter occur more regularly with the trend of ice-free duration extending into August and October.
Meaning, if you live through the next two elections, you'll see it. So will everyone else.


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At 3:23 PM, Blogger Theodore Wirth said...

Thank you for your hard work and pointing this out. However, the bigger problem is that nobody gives a rats' ass until their own mobile home is literally floating down the river to oblivion. Gunz and cheap beer, chips, V8s and gas is all that matters in the "home of the brave and the land of the free."

At 4:19 PM, Blogger Gaius Publius said...

until their own mobile home is literally floating down the river to oblivion

We may not be that far away. When that day comes, I just want the one right answer on the table — Stop Now — not some half-baked delaying idea that keeps the carbon profits from floating down that river too. Thanks for the kind words, Theodore.


At 8:36 AM, Anonymous Anonymous said...

Thank you GP for continuing the drumbeat. Not that americans will ever figger it out, but the first step in solving a problem is understanding it.

I would like to augment, if I may.

One other aspect to the seasonal freezing of sea ice (both poles), is what I've seen called "the brine cycle" (you can google that). As seas freeze, they squeeze very dense, salty brine out of the water that freezes which then creates a very cold, dense flow along the sea bottom, the volume of which is compensated by warm flows at the top of the seas. This contributes to the warm flow, for instance, that keeps the UK and north europe temperate instead of seasonally arctic.

This cycle has just begun to be understood... and now it's being disrupted by warming. The resulting changes are conjectural because of our lack of good understanding. But be assured that stuff will just get weird somewhere. Already there has been observed a blob of record cold and less salty water in the north atlantic due to the melting of Greenland. This is projected to also disrupt the warm currents which temper Europe's climate.

If Europe is lucky, the cold blob will just offset the lack of a brine cycle... but nobody really knows... yet.

Also, and just as important, we should realize that this is NOT reversible at this point. It's over. Nothing humans could do (short of a massive die-off of 6B of us) will matter... not that we have the capacity to DO anything differently at all.

If you care, just don't have kids. Their world will be a fuster cluck and there's nothing we could possibly do to make it not so.


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