Tag: sea ice

Ah, I see you have the Wishart that goes “ping”

n Ian Wishart’s lexicon, to “ping” someone seems to mean catching them out in a mistake or false claim. It’s a word he’s fond of using in his regular attacks on Hot Topic, most recently over my post on sea ice volume, and a comment thereunder by William “Stoat” Connolley. My post was “bad science” and I’m a “science illiterate” it seems. Unfortunately, all Ian does is demonstrate that his own science literacy is somewhat limited. His ping, like sonar, comes bouncing right back at him…

 

My post Feel floes (gone by 2016) was mainly concerned with looking at the issue of whether the Arctic sea ice was “recovering” from the record minimum of 2007. Wishart says it is “recovering strongly for the third year in a row”, but the volume data shows that to be nonsense. Wishart’s main bone of contention, however, seems to be about the impact of sea ice reduction on northern hemisphere climate. Here’s his first misdirection:

Gareth, incidentally, tries to argue in reply that volume is relevant because of the heat exchange to the atmosphere involved in re-freezing water.

My reply made no mention of volume versus area — I was just pointing out that albedo effects (though important) are not the only climate impact to be expected from a reduction in sea ice. The last three years have averaged around 2 million square kilometres below the average minimum over 79-00. That huge area of ice has to refreeze in autumn, and in so doing releases heat to the atmosphere. It seems Ian doesn’t have the foggiest how much is involved.

But here’s some news that evidently they missed over at HT: when ice grows in volume, it’s because sea water is converting to solid ice, with the same heat exchange taking place in regards to the first six inches of ice, the next six inches of ice, and all the ice thereafter. And sea ice grows because it is freakishly cold, and what little heat is liberated in the process is not strong enough to compensate for the cold.

Read that last sentence again: “what little heat is liberated in the process is not strong enough to compensate for the cold.” Time for today’s lesson. The heat required to warm 1 kg of water by 1ºC is a little over 4,000 Joules. The heat required to melt 1kg of ice is 333,550 Joules (aka the enthalpy of fusion) — about 80 times as much. The same applies in reverse — that is, when 1 kg of water turns to ice, it releases 333 kilojoules of energy. Now consider how much extra heat (compared with the long term average) is being liberated by the formation of 2 million km2 of new ice, which over winter will become about 1.5 metres thick. It’s a very big number indeed — my back of the envelope calculation (corrections and precisions welcome — William?) suggests it’s of the order of 11.5 x 1011 GJ (gigajoules). A big number. Let’s halve it, to allow for ice acting as an insulator. Still more than big enough to show up in the figures for Arctic climate. And it does.

Wishart dislikes Skeptical Science almost as much as Hot Topic (he describes John Cook as my alter ego, which is much more flattering to me than John). There’s a recent post there about a new paper describing the feedback loop between summer sea ice reductions and autumn and winter warming (also at Science News). But there’s an earlier paper to refer to, that I’ve written about before: The emergence of surface-based Arctic amplification by Serreze et al (The Cryosphere, 3, 11–19, 2009 – PDF) who examined Arctic climate data up to 2007 and found them to be “consistent with the emergence of surface-based Arctic amplification associated with declining sea ice extent”. There’s a good discussion of what this is and what it might mean for climate and weather in Mark Serreze’s chapter in last year’s WWF Arctic report, discussed at Hot Topic here. In any event, it’s not news. You might have expected someone as au fait with the literature as Wishart to have been keeping up. Or perhaps not…

Still, I did learn something interesting from his post. He’s finished his “Climategate” revision of Air Con, and apparently this “new edition also contains extensive new information on why ocean acidification is not being caused by CO2“. Oh really? That’ll be news to the oceanographers of the world. An excellent excuse for another look at his “work”, perhaps… ;-)

[The hospital sketch (bonus audio edit)]

Feel floes (gone by 2016)

The usual suspects have been making much of the fact that over the last few weeks Arctic sea ice extent (NSIDC daily graph here) has been bumping around the 30 year average for this time of year. John Cook at Skeptical Science posted on the subject last weekend, making the important point that what matters most is not extent or area, but the total volume of ice that’s present — and that’s showing no signs of “recovery”. John’s post is well worth reading, but it set me off on a very interesting trawl through the references he provided — and drew my attention to a most useful graph of ice volume and trend. It also pointed me to research that suggests the Arctic could be effectively ice-free in summer within ten years — possibly as soon as 2013.

Continue reading “Feel floes (gone by 2016)”

Wake of the flood

About 15,000 years ago the world began to warm out of the last ice age. The huge ice sheets that covered North America and Northwest Europe began to melt, and sea level began to rise. But 12,900 years before present, the climate of much of the northern hemisphere made a rapid return to full ice age conditions — cooling by as much as 10ºC. The Big Freeze, as it’s sometimes called, could have started in as little as one season. The cold snap lasted 1,300 years before warming resumed and the current interglacial began. This cooling episode is known as the Younger Dryas, because it was associated with an increase in pollen of the Arctic plant Dryas octopetala in Norwegian lake sediments.

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Arctic sea ice maximum reached, melt starts

Arcticseaice100306NASA.jpg

Arctic winter sea ice extent reached its maximum on March 31st, the latest date since satellite records began in 1979 according to the latest sea ice update from the National Snow and Ice Data Centre. The maximum extent was 15.25 million square kilometers. The NASA image above shows the ice extent on March 6th, before the late month growth spurt caused by a cold spell in the Bering and Barents seas. This late season ice is unlikely to have much impact on summer minimum, as it is thin and will melt rapidly as temperatures rise. Click on the image to get to a NASA animation of the winter ice season (not available on Youtube, or I would have posted it).

The NSIDC points out that a critical factor is the age and thickness of the ice as it heads into the summer melt season. The video below explains why, and how NASA is running a series of flights over the Arctic, the IceBridge campaign, to replace the thickness data lost with the ending of the first ICEsat mission. A new satellite won’t fly until 2013. The flights are already generating some fascinating imagery — I’ll be keeping an eye on their Twitter feed for more.

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It’s grim up North (but beautiful too)

Blogs, or to spell out the contraction, web logs, were originally just that: a log of interesting things found on the internet. Yesterday was a day when I rediscovered that tradition. Prompted by a comment from glaciologist Mauri Pelto on my recent Greenland post, I started off by making a visit to NASA’s MODIS Rapid Response System image site, which provides access to near real-time imagery from the Aqua and Terra satellites (click on Near-real-time production under “quick links” to be taken to the most recent images). The images aren’t fully processed (you can see “stripes” and slight distortions), but they give you a good look at what’s going on. I first went and had a look at what spring on the Petermann glacier in NW Greenland looked like:

Continue reading “It’s grim up North (but beautiful too)”