“shows that the melting of sea ice has been unusually fast this year, with as much as 40,000 sq km now disappearing daily.

The melt season started almost a month later than normal at the end of March”

Shocker!

Melt starts late (presumably because it’s been colder than normal?) and then when it starts it goes very quickly.

I wonder, is there anything else that works like that? Umm, reversion to the mean sort of thing?

Tim: so how does “reversion to the mean” explain away the fact that the ice extent is “now at its lowest physical extent ever recorded for the time of year”?

Are you not keeping up with matters Arctic ice related?

http://www.guardian.co.uk/environment/2010/mar/22/wind-sea-ice-loss-arctic

The low levels of ice recently are to do with wind blowing it around, not melting.

Tim: interesting. Though as that article points out, the study only attributes 1/3 of the loss to increased winds (and, it seems, leaves open the question of why the winds themselves have increased, and/or why the wind should have more of an effect on ice levels than previously), and the lead scientist on the study states that “a number of other factors were also responsible for ice loss, including warming of the air and ocean”.

So Tim that would mean that ice volume is not declining that rapidly would, the wind would just be stacking the ice up on top of itself instead of the ice actually melting. So lets look at the latest results for arctic ice volume then.

http://psc.apl.washington.edu/ArcticSeaiceVolume/images/BPIOMASIceVolumeAnomalyCurrent.png

“So Tim that would mean that ice volume is not declining that rapidly would, the wind would just be stacking the ice up on top of itself instead of the ice actually melting.”

That is assuming that the wind just blows it around at the same latitudes. I have a feeling that there are several places up there where wind might blow ice south…..where it melts?

BTW, just to get this straight. No, I am not one of those who thinks that climate change isn’t happening. My arguments are all about what we do about it, not the existence of it.

And my first comment above was just snark about the original post not making the connection between two things. If the melt starts late then it’s really not all that surprising that the melt is happening quickly.

The ice that would have melted in March did not: so now, in May/June we have both the March ice melting and the May/June ice melting. Thus a higher daily rate of ice melting.

No difference from a late thaw of an ice bound river leading to a higher spate in that river.

Tim, what you say would make sense if the ice extent was only returning to the mean, but it hasn’t it has blown past the mean and continued to decline, what do you think NSIDC means by lowest physical extent ever recorded for this time of year. I would expect the rate of decline from this point onwards to slow to what is usual for the time of year.

Kevin

We have two entirely different things here.

1) Wind influenceing the extent of the ice cover. I agree that ice cover is lower than in the past (correction, lower than some times in the past and higher than others) and wind is part of the reason for that.

2) The melt rate this spring. Precisely because the melt was delayed we will see a higher melt rate now: this is the reference to reversion to the mean.

Don’t play “gotcha” with me by attempting to conflate the two.

I’m sorry Tim but the original article didn’t mention melt rate. It mentioned that:
“Artic sea ice – … – is now at its lowest physical extent ever recorded for the time of year”

I’m not the one conflating.

Kevin

Apologies Tim, I just noticed the second last paragraph.

That being said, the rapid melt rate did continue long after it passed the mean for the time of year. Whether the ice was blown somewhere else before it started melting or not.

Kevin

Of course, the fact that ice is thicker this year (and therefore takes longer to melt) than the previous two years is ignored in these predictions:

http://wattsupwiththat.com/2010/06/02/the-undeath-spiral/

I’m therefore putting this down as likely to be another one of the ‘global warming predictions that is reported then never mentioned again’.

Perhaps it would be worth discussing this when we know what 2010′s Artic ice cover was actually like, in say 2011 (or late 2010). After all, similiar predictions for 2008 and 2009, of increased ice loss, actually saw a gain in ice in both years. At the moment trying to have an intelligent discussion based on predictions with a variable recent record (to be fair it was right about a low extent in 2006) seems a bit pointless when we can wait six months and discuss the actual figures and weather patterns. My bet is that we won’t though, as I’m suggesting ice extent will remain quite high.

Watchman: but the volume of sea ice is still substantially down, even if the ice is thicker. See the chart linked earlier, but here is is again for reference:

http://psc.apl.washington.edu/ArcticSeaiceVolume/images/BPIOMASIceVolumeAnomalyCurrent.png

John,

As I say, I’m not disagreeing. But as Tim pointed out the rapid melt was expected, and my point is the thicker year-on-year ice is less likely to melt at anything like the last couple of year’s rate, thus reducing the rate of further melting.

The point is that we will know who is right and wrong on all of this in a few months. Science is not done by prediction (sorry IPCC) but on actual data, and the ice is reasonably measurable at least.

“Science is not done by prediction (sorry IPCC) but on actual data…”

Huh, tell that to all the people who go on about AGW not being a testable theory with falsifiable predictions. They seem to think that being able to predict things is a necessary feature of a ‘proper’ science (and use the alleged lack of said predictions as a rhetorical stick to beat climate scientists with).

WRT the factoids in the OP – ice extent numbers for any given melt season are a weather question now, not a climate question. And weather is, famously, hard to predict. As Tim W. notes your final results are conditioned by things like the wind patterns pertaining for a particular summer (which is what made 2007 such a record breaker).

Climate questions come into the frame when we start to think about why the arctic ice extent numbers have become subject to transient weather phenomena (they didn’t use to be) or what it means if the 2007 record (at the time an observation which really grabbed attention because it was so far below the norm) ends up getting broken within a few years.

Mostly what the last few melt seasons seem to be telling us (once you factor in the GRACE data plus the anecdotal stuff about the crappy, unstable nature of the remaining ice and successful transits of the NW passage) is that the IPCC was wrong about ice in AR4 and things are moving faster on the arctic icecap than they predicted.

I don’t expect this last point to get much airtime at places like WUWT however – despite their love for ‘IPCC was wrong’ stories.

Regards
Luke

@asquith

It does seem to suggest a certain desperation when the best that can be done is abuse.