Hurricane Isaac vs the Republicans is rising on the charts – but its really a footnote compared to the big story. How long before the major media turn cameras on the jaw-dropping drama that’s had scientists transfixed for the last 3 weeks?

Arctic Sea Ice Blog:

Basically, I’m at a loss for words, and not just because my jaw has dropped and won’t go back up as long as I’m looking at the graphs . I’m also at a loss – and I have already said it a couple of times this year – because I just don’t know what to expect any longer. I had a very steep learning curve in the past two years. We all did. But it feels as if everything I’ve learned has become obsolete. As if you’ve learned to play the guitar a bit in two years’ time, and then all of a sudden have to play a xylophone. Will trend lines go even lower, or will the remaining ice pack with its edges so close to the North Pole start to freeze up?

ClimateCodeRed:

UPDATE 27 AUGUST: Sunday’s data confirms that the previous sea-ice extent minimum of 24 September 2007 was broken last Friday, 24 August 2012. What is also stunning are sea-ice daily extent figures averaging ice loss of more than 100,000 square kilometres per day for the last four days. This suggest melt is accelerating very late in the melt season in a pattern that has never before been observed. The Arctic this year is heading into new territory and it looks like 2012 may in retrospect be seen as the year when a new melt regime took hold.

The ice extent is about to drop below 4 million square kilometres for the first time in the satellite record, and the Arctic has shed almost half a million square kilometres of sea-ice in last five days! With three weeks of the melt season still to go, it’s not hard to see extent dropping another half a million square kilometres (or more!) to 3.5 million square kilometres. (In previous big melt years of 2007 and 2011, around half a million square kilometres was lost after 26 August.)

This is starting to make the second graph (below) looking reasonable, and those scientists and models which have been suggesting an sea-ice-free summer Arctic within a decade to be on the money.

Climate change impacts are frequently happening more quickly and at lower levels of global warming than scientists expected, even a decade or two ago. And this week the Arctic has provided a dramatic and deeply disturbing example.

According to IARC/JAXA satellite data at Arctic Sea-ice Monitor from the Japan Aerospace Exploration Agency, the sea-ice extent of 24 August 2012 of 4,209,219 square kilometres broke the previous record in the satellite era of 4,254,531 square kilometres set on 24 August 2007. Back then the were scientific gasps that the sea ice was melting “100 years ahead of schedule”.

What is astounding is that the record has been broken with three to four weeks of the melt season to go, and that the rate of melting this month is unprecedented in the modern record. Check the chart above (click to enlarge), with the red line mapping 2012 sea-ice extent. The slope of the line is much steeper than in previous years for August.

Looking at the data, the daily rate of sea-ice loss for 1-24 August has been 99,029 square kilometres per day in 2012, compared to:

2007 62,976 square kilometres per day

2008 72,785 square kilometres per day

2009 53,859 square kilometres per day

2010 55,109 square kilometres per day

2011 63,342 square kilometres per day

2012 99,029 square kilometres per day

And last three days have been 119,219, 128,281 and 122,188 square kilometres per day (they use 2-day running average, so last figure subject to revision).

It is remarkable that rate of loss is so much greater than previous years this late in the melt season, and at present shows no sign of easing.

The ice is now much thinner on average than in the past, as the extent of multi-year icedeclines sharply. Thin ice is easily smashed up by storms and rough seas, and that’s what’s happened this year. In early August, a huge, long-lived Arctic ocean storm decimated the sea ice area which was melting out at a record rate, before the high waves and winds shattered the Siberian side of the ice cap. But there have been subsequent, less well-reported, cyclonic storms churning up the ice, which may explain why the melt rate has not eased off in the last 10 days.

What the minimum extent will be this year is anybody’s guess. It depends on weather conditions over the next three weeks, and how much ice is now just above the threshold (of 15 per cent sea-ice in a given area) and is currently counted as sea-ice, but likely to be below the threshold by the third week of September.

Even if the ice loss over the next 3-4 weeks was similar in magnitude to previous recent years, the season low could be around 3.5 million square kilometres. Maybe a good bit more, perhaps somewhat less. We will have to wait and see.

The next chart, amended, from NSIDC shows the 2007 fourth IPCC report projections for Arctic sea ice (blue line) and projections for RCP4.5 (representative concentration pathways) (red line) being used for the forthcoming fifth IPCC report in 2014. Actual observations are in black, and I have taken the liberty of sketching in grey what it will look like if the 2012 figure is around 3.5 million square kilometres.