A beginner’s guide to the importance of Arctic sea ice

In this beginner’s guide Tom Wagner, NASA’s cryosphere programme manager, outlines why studying Arctic sea ice is important, illustrating his talk with some great graphics. Meanwhile, the NSIDC has announced the final figures for September’s sea ice minimum:

The average ice extent over the month of September, a reference comparison for climate studies, was 5.36 million square kilometers (2.07 million square miles). This was 1.06 million square kilometers (409,000 square miles) greater than the record low for the month in 2007, and 690,000 square kilometers (266,000 square miles) greater than the second-lowest extent in 2008. However, ice extent was still 1.68 million square kilometers (649,000 square miles) below the 1979 to 2000 September average.

NSIDC scientist Walt Meier thinks there may be some hope of “stabilising” the ice after recent heavy losses:

We’ve preserved a fair amount of first-year ice and second-year ice after this summer compared to the past couple of years. If this ice remains in the Arctic through the winter, it will thicken, which gives some hope of stabilizing the ice cover over the next few years. However, the ice is still much younger and thinner than it was in the 1980s, leaving it vulnerable to melt during the summer.

But will there be a longer term recovery back towards the sort of ice cover seen before 2000? The NSIDC team doesn’t think so.

NSIDC lead scientist Ted Scambos said, “A lot of people are going to look at that graph of ice extent and think that we’ve turned the corner on climate change. But the underlying conditions are still very worrisome.”

After a couple of cool summers, one wonders what impact another warm year might do to the ice. As ever, I shall be watching next year with great interest…

17 thoughts on “A beginner’s guide to the importance of Arctic sea ice”

    1. OK, but you’ll need to dig back a bit… there are lots of posts tagged Arctic, but Here come the warm jets from Jan 2008 is a good place to start.
      The crucial metric for the sea ice is not the area or extent (two slightly different measures), but the volume. Earlier this year, Ron Kwok’s team at NASA published data on ice volume up to 2008 (some of the imagery is in the video above, and Wagner confirms my point), showing that even though 2008’s minimum extent was above 2007’s record low, the volume of ice continued to decline.
      So… big question. Has the sea ice volume grown over the last year? If it has, then the buffer against warming in the Arctic heat budget will have increased. That would be good news, because it could mean that the onset of positive feedbacks from methane in hydrates and permafrost might be delayed. If it hasn’t, then the Arctic is managing to maintain a summer cap of thin ice in cool years, but could be vulnerable to another rapid ice loss episode if there’s another pulse of warm seawater into the ocean, or if the atmosphere delivers another summer when warm air is pumped up North. Some of this might become clearer as the teams working in the Arctic begin to process the data they’ve gathered over this summer, and I expect there will be some really interesting stuff on offer at the Fall American Geophysical Union meeting in ?December…

  3. So volume is more important… why open up the door to idiots like my self by reporting simple area figures and then obliquely talking about volume;

    If this ice remains in the Arctic through the winter, it will thicken, which gives some hope of stabilizing the ice cover over the next few years. However, the ice is still much younger and thinner than it was in the 1980s, leaving it vulnerable to melt during the summer.

    when the media will only see “area increase”. Haven’t read the full article – will do so tonight.

    thanks.

    1. To be fair to all the teams giving figures for area and extent, they can only operate with the tools they’re given — and from satellites it’s much easier to measure area than thickness. Kwok’s team now has access to a satellite that can measure thickness, and so the story is now beginning to be told… (more info and links here)

  4. So volume is more important… why open up the door to idiots like my self by reporting simple area figures and then obliquely talking about volume;

    I can empathise with that a bit…

    Great post.

  5. So thinking a little further…

    It’s not a simple vol vs area issue based on thermal mass and amount of water stored, as there’s the Al Bedo guy mixing things up as well eh? Probably also hydrodynamic effects on ocean flows?

    I think I’ll stand by my original point about the risks of apparently naive scientists making probably true but easily misconstrued statements of fact (especially if one is wanting to ‘re-purpose’ the findings).

  6. Good idea to divert attention to the Arctic, when latest research shows that Antarctic ice melt during last Southern Summer was the lowest ever recorded in the satellite history.

    Tedesco M., and A. J. Monaghan, 2009. An updated Antarctic melt record through 2009 and its linkages to high-latitude and tropical climate variability. Geophysical Research Letters, 36, L18502, doi:10.1029/2009GL039186.

    1. And funnily enough, we know why:

      Reporting in the journal Geophysical Research Letters, scientists from British Antarctic Survey (BAS) and NASA say that while there has been a dramatic loss of Arctic sea ice, Antarctic sea ice has increased by a small amount as a result of the ozone hole delaying the impact of greenhouse gas increases on the climate of the continent.

      Meanwhile, Greenland and Antarctica continue to lose large amounts of ice – thinning dramatically at the edges.

  7. Two points.

    First this is discussion. These are questions. I’m not an expert on these matters and don’t claim to be. But when I read/watch things like this I can’t help but question some of the logic

    On albedo loss. He mentions increased evaporation and atmospheric water vapour. Would the loss of albedo from sea ice melt not be out-weighted by the increase in albedo from increased cloudiness?

    Second, Gareth you mention the hole in the ozone layer over Antarctica. There is also a hole over the northern pole. Why would one hole create cooling and the other not?

    1. Would the loss of albedo from sea ice melt not be out-weighted by the increase in albedo from increased cloudiness?
      No. The Arctic is already a pretty cloudy place in summer (2007’s record loss was at least in part related to the clear sunny weather that prevailed over large parts of the ocean for much of the summer), and the period when reduced ice cover adds most water vapour to the atmosphere is during the autumn (because ice is at a minimum then), and albedo is not the most important factor at that time. Worth noting that albedo is also affected by the state of the ice – wet ice has a lower albedo than cold white snow.

      Second, Gareth you mention the hole in the ozone layer over Antarctica. There is also a hole over the northern pole. Why would one hole create cooling and the other not?

      There is an ozone hole over the Arctic during boreal spring, but it is much more diffuse than that over Antarctica (people were surprised when it was first discovered — it was not expected). The polar vortex — the round-the-pole circulation in the atmosphere — is not so “tight” up North, and so the hole is not so focussed. Geography also plays a part. Antarctica is a cold, high plateau surrounded by a cold, circumpolar ocean current. This creates an intense vortex that tends to “trap” air at the pole, allowing it to cool more than in the Arctic, which is pretty much the reverse of the Antarctic — an ocean surrounded by relatively low lands.

      An intensification of the polar vortex in the southern hemisphere has been observed for some time, and is having an impact on the distribution of sea ice (see my link above), and via the Southern Annular Mode/ENSO /PDO interactions, likely on NZ weather patterns as well (subject of active study).

      Hope that helps. If any of the Jims are reading, you might chip in too 😉

      1. Thanks.

        My question on albedo wasn’t only referring to albedo over the Arctic, I was meaning global. I often hear references to global warming increasing the water vapour in the air, this vid mentioned decreased albedo from the Arctic, I was wondering if this would be more than offset from any increased albedo from evaporation, .

        1. That would be what Roy Spencer calls a “negative cloud feedback”. The evidence for that is next to non-existent (only Spencer claims to able to find one in the data). There are good reasons to suspect that even if they exist on a regional or seasonal scale they cannot dominate the overall warming response. If they did it would be very difficult for the climate to warm up out of an ice age, for example.

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