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.

Here’s the graph that caught my eye. It’s produced by the Polar Science Center at the the University of Washington in the USA, and is regularly updated — this was generated on April 17th.


It shows the sea ice volume anomaly and its trend, as calculated by the Pan-Arctic Ice Ocean Modelling and Assimilation System (PIOMAS) developed Dr J Zhang and his colleagues at the PSC. It’s important to note that this is the anomaly that’s being shown — the difference between the ice volume on a given day and the average for that day over the full 79-09 satellite record (in other words, the seasonal cycle is removed). The blue line is the trend (- 3,300 km3 per decade) and the grey bars show one and two standard deviations from that trend. Two things are I think obvious: the ice volume has been steadily declining over the last 30 years, and the rate of loss looks to have increased markedly over the last ten years. We’ll come back to that point…

Now lets compare that graph to the sea ice area anomaly as calculated by the Polar Research Group at the University of Illinois, from their Cryosphere Today site.


I grabbed that graph a day or so ago, from here. It updates daily, so the end point will have changed, but the history won’t. Again, we’re looking at the difference from average for any given day in the record, with the seasonal cycle removed. There’s been a steady decline over the last 30 years, and a noticeable steepening over the last ten. So what’s the difference between area and volume? The thickness of the ice, of course. Estimates of extent or area give us only 2D information — but the amount of ice floating on the Arctic Ocean is the area times the thickness.

Now focus on the most recent three years on both graphs. You’ll recall that Arctic sea ice recorded a new record low summer minimum in 2007. Looking at the area anomaly, you can see that clearly as the lowest spike on the graph — the minimum was over 2.5 million km2 below average. The anomaly then gets smaller as the winter freeze-up continues, bigger again in summer, and so on. What’s striking is that the amplitude of the “cycle” between low and high anomalies has become much larger since that 2007 record melt. Why that might happen is an interesting question (for another day, perhaps).

The PIOMAS data provide a different perspective. The 2007 summer low is obvious on the graph, but it is no longer the lowest point. That was reached in 2009. In Feb-Mar 2009 the Arctic sea ice volume was 11,900 km3 — below the average minimum September volume over 79-09, and the current volume is only slightly above that. In other words, the sea ice hasn’t “recovered” by any stretch of the imagination — it’s two standard deviations below the trend, which is already showing decline of 3,300 km3 per decade. The PIOMAS numbers reflect the loss of thicker multi-year ice in recent years, replaced by thinner one and two year old ice.

What happens if you look at the recent sea ice volume trend and project it into the future? Here’s a graph from a presentation [pdf] by the US Naval Postgraduate School’s Prof Wieslaw Maslowski, given at the ARCUS State of the Arctic conference in Miami last month (anyone interested in Arctic research will find a treasure trove of material at the conference web site):


This shows the October-November ice volume over the last 30 years and five different estimates of the current rate of decline in those months. The most recent data (from Ron Kwok’s team at NASA) is consistent with a rate of decline of about 1,000 km3 per year. The green line on the graph shows the volume of ice left in the Arctic when there’s a bit clinging to the Canadian archipelago and Greenland (see the little map above). Maslowski therefore projects an “ice-free fall by 2016 (±3yrs uncertainty)”. Not having been present at his talk, I can’t tell you exactly how he put that in words, but the graph and quote come from his slides. Maslowski is well known for his aggressive projections for summer sea ice loss, but this is the first time I’ve seen his argument quantified.

I’m still mulling over the implications (not least for sea ice bets). On one level, it’s confirmation of a worrying projection — an ice-free Arctic Ocean in late summer within the next ten years. The consequences of that, for both the climate of the northern hemisphere and the geopolitics of the Arctic are huge. On the other hand, there are undoubtedly arguments as to why this might not happen — at least, not so soon. A run of cool summers could allow the ice volume to rebuild as it did in the early 1980s. First year ice could become second year ice, then third year and so on. That seems to be within the range of natural variation in the PIOMAS numbers, but it might only postpone the inevitable by what — five or ten years?

Here’s the context: the IPCC’s fourth report put Arctic summer sea ice loss out into the second half of the century. Current volume numbers are consistent with loss within ten years. Warmer Arctic autumns mean snowier northern hemisphere winters and significant changes in weather patterns. The sea ice is not recovering — instead it shows that rapid climate change is happening here and now. And that’s not alarmist, it’s truly alarming.

[Beach Boys: apologies for the appalling pun, but I’m running out of relevant song titles for ice posts. All suggestions gratefully received.]

18 thoughts on “Feel floes (gone by 2016)”

  1. Whether it's 3 years or 15, I guess the next question is, will the loss of the Arctic summer sea ice lead to a slowdown in the thermohaline circulation?. If so, it could mean some very harsh winters for North America & Europe whilst the rest of the planet heats up.

  2. It was interesting to note the high snowcover extent at the end of February, ranked second in the last 40 years. However, the most remarkable aspect is the extent of snow melt loss during March. By the end of the 14th week of the year, we were in a dead heat for the lowest snowpack extent at that point of the year for any of the last 40 years according to data at the the Rutgers Global Snow Lab. http://climate.rutgers.edu/snowcover/ . How will the sea ice season play out?
    Forecasting of sea ice or glacier mass balance is a skill that is important to develop but which is in its infancy.
    Glaciers http://glacierchange.wordpress.com/2010/04/15/nor
    Arctic sea ice http://psc.apl.washington.edu/zhang/IDAO/seasonal

    1. I have two predictions:

      1) The summer Arctic ice minimum extent will set a new record low.

      2) Skeptics will lose all interest in talking about Arctic ice around about September.

      I give 1) 50% chance, and 2) a 100% chance if 1) turns out true.

  3. Watts to be done?
    Hell will freeze over before the "sceptics" see any sense. And that ain't happening anytime soon coz the summer Arctic isn't – despite the assurances of Mr Watts.
    I was reading the same last night – we must have been visiting the same sites. 🙂
    My Canadian friends in Toronto wrote to say they shoveled snow just once this year – it seems the snow went further south.

  4. This is all very well, but can the blame for any of thisbe pinned to manufactured CO2 emissions? Or are there other factors at work, after all we are just coming out of a mini ice age and ice volumes should be expected to reduce.

  5. "pointed me to research that suggests the Arctic could be effectively ice-free in summer within ten years — possibly as soon as 2013." – that stuff is twaddle. Ignore it. I'm sure I blogged that a while back (here perhaps:http://scienceblogs.com/stoat/2008/11/another_tra

    I'm not sure I buy the volume-is-more-important argument either. In terms of climate impact, what counts is a layer of ice cover: insulates the ocean, reflects sunlight. Doesn't much matter how thick it is past 0.5 m.

    But then I'm not a pro any more :-).


    My recent post I make the big time!

  6. A few things make me think it's not twaddle. First, the multi year ice (ie the volume of ice left at summer minimum) represents a buffer against short term change. In a stationary climate, the buffer was large enough to more than compensate for a run of warm years, and would be replenished by cooler years. It is now greatly reduced. The failure of ice volume to \”recover\” in the same way as the area or extent since 2007 suggests to me that the primary forcing is different (oceanic rather than atmospheric). There's more heat coming into the system than it can lose over winter — enough to melt about 1,000 km3 per year, it would seem.

    The climate impact is not just from the ice cover itself, but from the regrowth of that ice cover. The greater the area of ocean that has to freeze up in autumn, the greater the heat output to the atmosphere over the early winter (see recent stuff on amplification). That is already changing the NH climate, and will continue to do so.

  7. Good to see William Stoat down here.

    Yes, I've been following those discussions with Curry in the centre – it's a strange world we're living in (said with a deeply philosphical sigh..)

    But back on topic, John Cook's just featured the recent Screen and Simmonds paper that points to the positive feedback of less ice cover being the main driver of the greater temperature increases in the Arctic, the "Artic Amplification": http://skepticalscience.com/What-causes-Arctic-am

  8. "I'm not sure I buy the volume-is-more-important argument either"

    w/r/t the albedo/reflectivity effects this may be true but the really important thing to remember (just watch an ice cube melt under a hot tap dripping if you want to see it with your own eyes) the rate of melt increases as the surface area/volume ratio increases*.

    if the imbalance of heat energy is not addressed there will be an accelerated rate of melt until the polar cap is gone (unless some forcing eventuates to arrest this).

    and then the reflectivity effects start to kick in…

    (*because a greater proportion of the ice is exposed to heat energy and there is less ice to absorb said energy)

  9. > A few things make me think it's not twaddle…

    By twaddle, I mean the all-ice-gone by 2013 stuff. That I think clearly is nonsense; extrapolating to zero volume just isn't plausible. Of course, if you disagree, I've got money to put where my mouth is, unlike Maslowski…

    That ice volume is important isn't twaddle. However, I'm a teensy bit cautious about estimates of ice volume and how reliable they are. Ice area is far easier to measure from space.
    My recent post Wallingford

  10. Thanks. It's worth pointing out that Maslowski doesn't appear to be extrapolating to zero volume in the graph above — the green line is the volume left when you've got that rump of ice clinging to the Canadian archipelago. Presumably he thinks that will hang around for a while — it's roughly what the AR4 modelling suggests the summer minima might be by the second half of the century.

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