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Nightvid Cole

The doubling of the current year from 2012 to 4024 on the volume anomaly plot date is a bug unlike any I have previously seen...

Neven

Welcome to the future, Nightvid Cole. Well spotted. :-)

Chris Reynolds

Wipneus's graph interests me in particular.

I've been going on about the volume loss in Spring 2010, and that it was as great an event as the Crash of 2007. Whereas 2007 was an area driven volume loss, Spring 2010 was a thickness driven volume loss - change in area/extent doesn't account for it. The graph from Wipneus shows that the observed volume for 2010 deviates from expected in April 2010, that's no surprise to me. 2011 is more interesting, while 2010 was probably caused by weather, like 2007, there weren't such weather conditions especially conducive to ice melt in Spring 2011. Wipneus's graph seems to support this as the deviation from expected throughout 2011 until the minima when volume growth takes it above the expected line.

This is going to be an exciting year, I can't wait until June's PIOMAS figures are out. Although we should have initial confirmation of any large Spring loss by June when May's figures are out.

Kevin O'Neill

Chris R has pointed to 2010 as another shift in the arctic comparable to 2007. This is borne out by the data:

PIOMAS Volume Loss Comparison
First Half of melt Season to 2nd Half
First Half = Spring Equinox to Summer Equinox
Second Half = Summer Equinox to Autumn Equinox
Day 81 to 173, Day, 173 to 264

Year Total 1st 1/2 2nd 1/2 1st % 2nd %
2000 16.34 -3.77 -11.58 23.1% 70.83%
2001 15.57 -4.30 -10.34 27.6% 66.38%
2002 16.75 -4.67 -11.48 27.9% 68.57%
2003 17.08 -5.14 -11.36 30.1% 66.49%
2004 15.93 -3.76 -11.37 23.6% 71.39%
2005 17.02 -5.11 -10.95 30.0% 64.34%
2006 16.20 -4.97 -10.49 30.7% 64.77%
2007 17.41 -6.04 -10.90 34.7% 62.60%
2008 18.09 -5.27 -12.05 29.1% 66.59%
2009 18.19 -5.98 -11.36 32.9% 62.44%
2010 18.97 -8.24 -09.96 43.4% 52.50%
2011 17.94 -7.15 -09.82 39.9% 54.74%

From this we can see a dramatic shift in volume losses to the first half of the melt season. This is not simply due to a shift in when the ice melts (moving late summer losses into early summer), but an overall increase accompanied by the shift to the first half.

Andrew Xnn

It maybe that something else has happened with 2010 and 2011. Both of these years show a dramatic late season loss followed by a later recovery.

Could it be that melt ponds are becoming much more common and in turn are not being measured by the satellites accurately?

Alternatively, the melt ponds may be occurring earlier in the season of 2010 and 11.

I'm suggesting this because it seems very odd that the amount of melting in the 2nd part of the season has fallen so much for 2010 & 2011.

Chris Reynolds

Andrew,

A commentor at my blog (Peter IIRC) pointed out why this reduction during the Summer was probably happening - areas moving from summer melt to an earlier melt in the Spring. That explanation does not however account for the massive Spring loss.

You can see the magnitude of the volume loss from a timeseries of PIOMAS volume.
http://farm8.staticflickr.com/7203/6801022094_7515a74805_o.jpg

On closer inspection of anomalies the volume loss is pinned down to Spring 2010.
http://farm8.staticflickr.com/7061/6947128835_ae7ec04429_o.jpg

The only part of the consideration that relies on satellite observation is the attribution to thickness loss as opposed to extent loss. This wouldn't be prone to melt pond effects because melt ponds alias as open water, and we're looking at a situation where there isn't enough area or extent change to account for the volume loss. Hence the volume loss has to be acounted for by a reduction in thickness.

Neven

Could it be that melt ponds are becoming much more common and in turn are not being measured by the satellites accurately?

Alternatively, the melt ponds may be occurring earlier in the season of 2010 and 11.

Andrew, I compared melt ponds in this post (check the large image). Based on that I don't think there were melt ponds forming earlier in 2010 and 2011, though your theory sounds plausible a priori.

Neven

Another small drop in CT SIA: 24K. The drops of the last three days could be easily wiped out in a single day.

FrankD

I'm working from my laughably bad memory here, and someone may want to actually confirm this by, you know, looking at achived copies of graphs and such, but...

IIRC, at the time PSC switched off PIOMAS v1.0, the linear slope through the anomaly data was -3.6 x 10^3 km^3 per decade. V2.0 initially had a much flatter slope, partly because recent volume was higher than in v1.0, but also because some older data was lower than in v1.0. The initial slope on the v2.0 anomaly was -2.8 x 10^3 km^3 per decade.

PSC recalculate the linear trend for the whole data set with each new monthly update. Attentive viewers will note that in the last nine months, the linear slope through that data has now increased to -3.0 x 10^3 km^3 per decade.

The recent anomaly minimum just missed squeaking back within -1SD of the trend before turning down again. My bet is that three or four more months of data dragging it down will see the recalculated slope / SD shift lower again. As a result this result, despite being unchanged, will now fall within -SD of the trend. Further, I'd bet a shiny penny that someone on the other side of the mirror will conclude that because the anomaly is back within -1SD (of a downsloping trend), ice loss must be slowing / stopping.

We pointed out here a year ago that the PIOMAS data is pretty clearly not linear (though exactly what curve it is following is debateable). The fact that PSC increase the slope of their trend line ~every four months only underscores that point. OTOH, Wipneus' quadratic curves appear to need far less tweaking to keep up with reality, so...go us!

Wipneus

I'm working from my laughably bad memory here, and someone may want to actually confirm this by, you know, looking at achived copies of graphs and such, but...

Impressive memory. I put my copies of last V1.0 and first V2.0 here:
https://sites.google.com/site/arctischepinguin/home/piomas/archive


Wipneus

Found on the arctic sea ice news bar:
http://www.guardian.co.uk/environment/2012/mar/14/met-office-arctic-sea-ice-loss-winter

Speaking to MPs on the influential environmental audit committee about the state of the warming Arctic, Julia Slingo, the chief scientist at the Met Office, said that decreasing amounts of ice in the far north was contributing to colder winters in the UK and northern Europe as well as to drought.

Without mentioning PIOMAS, she expresses serious skepticism about current volume estimates:

Slingo also dismissed fears that the Arctic could be entirely free of sea ice in summer as soon as 2015. Between 2025 and 2030 would be the earliest date she would consider it possible, she said, and the Met Office's latest models suggested 2040-60 as most likely. "Our expectation is certainly not in the next few years as you've heard from some evidence," she said.

She also said that suggestions the volume of sea ice had already declined by 75% already were not credible. "We know there is something [happening on the thinning of sea ice] but it's not as dramatic as those numbers suggest."

The problem, she explained, was that researchers did not know the thickness of Arctic sea ice with any confidence. She hoped a new ice-monitoring satellite launched in 2010, Cryosat2, would help with more accurate measurements.

Hmm, I would be surprised if PIOMAS would turn out to be that bad.

AmbiValent

I think she's trying to cover all the bases. She's rejecting a claim of a fast melting, but gets to say the Arctic Ocean would become ice free in less than 50 years.

And icebreakers passing through the North Pole region almost unhindered in the summer have already shown how much the ice cover has been weakened.

idunno

Hi Wipneus,

It's difficult to remember sometimes, as the opoosite is so often screamed out as being self-evident fact, but most senior scientists have consistently erred way on the side of caution.

The exception being Maslowski, who was not as far as I know, using PIOMAS to come up with his predicted date of 2016 =/-3 years for the Arctic to be essentially ice-free. IIRC that was based on calculations of the heat budget.

PIOMAS and Maslowski seem to me to agree quite nicely.

Daniel Bailey

Maslowski uses a proprietary model run on a US Navy high-speed super-computer. It has a much-greater resolution (and thus less granularity) than existing GCM's, enabling it to better model and reproduce the eddy processes in the Arctic Ocean.

He made his prediction in 2006. The actual decline in ice volume has never wavered in adhering to it.

Kevin McKinney

Again, I agree with Daniel. Dr. Peter Wadhams of Cambridge has been studying the Arctic sea ice about as long as anybody--his resume includes submarine trips courtesy of the Royal Navy. He calls Maslowski the best modeler around (in the context of Arctic ice) and just last summer expressed the opinion that it was rather looking as if Maslowski was turning out to be right.

We'll see, of course, but it's far from self-evident that Dr. Slingo is correct. That said, I'd like to add that she is no scientific lightweight, either:

http://www.metoffice.gov.uk/research/our-scientists/senior-scientists/julia-slingo

L. Hamilton

"The problem, she explained, was that researchers did not know the thickness of Arctic sea ice with any confidence. She hoped a new ice-monitoring satellite launched in 2010, Cryosat2, would help with more accurate measurements."

It's my understanding that the CryoSat-2 thickness estimates have not been well verified, and remain a challenge to interpret.

Bob Wallace

" did not know the thickness of Arctic sea ice with any confidence"

Ice thickness is a matter of sampling, is it not? How many samples are taken each year by teams on the ice and from underneath?

If you look at political polls we are able to tell much about the attitudes of 300 million people by talking to a couple hundred on the telephone.

Measurement of ice thickness is much more objective than attitudes.

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