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A conclusion of the 4th International Polar Year

Filed under: — rasmus @ 13 June 2010 - (Español) (Italian)

This week, the “Oslo Science conference” the largest conference ever -it was claimed – was held on polar sciences at Lillestrøm, just outside Oslo. Some of the web-casts from that meeting are worth watching, and I found especially the talk by David Barber (“On Thin Ice: The Arctic and Climate Change”, video link here) both a bit alarming as well as fascinating.

Storms and snow affect sea-ice growth, since a layer of snow on top of the ice insulates against the cold atmosphere and prohibits ice growth. Winds and extra mass can lead to break-up, and the amount of multi-annual ice is lower than expected; it has decayed and ‘rotted’. A mission with the Canadian ice breaker apparently managed to break ice slabs much thicker than expected, due to weaker ice. Also more recent reversals of the Beaufort gyre, unexpected long swells, and new ice on top of clumps of old ice fooling the satellites to think there is more multi-year ice than really the case, are just part of the story. In the mean while, the sea-ice for this season from NSIDC is on a low note.

The main message that I took home from this was that the sea-ice is more important than I previously thought. It appears clearer now that it plays a role in the Arctic amplification – which clearly is really emerging.

Some claim that reduced sea-ice can explain cold winters in the northern hemisphere, but I’m not yet convinced. The cold winters are due to weak Arctic Oscillation, and hence a shift in the air masses bringing frigid polar southwards, and this air is replaced by milder air in the polar region. Hence, a shift in the wind system as well as milder temperatures may favour less Arctic sea-ice.

The Antarctic sea-ice cover has increased on average in the last 30 years, but not everywhere. Both the general increase around East Antarctica and the large decrease off West Antarctica are attributed to the ozone hole and corresponding changes in the Southern Annular Mode (SAM, or the ‘Antarctic Oscillation’), though this probably doesn’t explain what is happening in winter. There is no clear polar amplification observed over Antarctica, such as seen as in the Arctic, and one explanation for this may be that the Antarctic continent has large ice sheets with enormous thermal inertia. But ice core data suggest that there have been amplification there in the past too. Nevertheless, the Arctic is characterized by a polar ocean with retreating sea-ice in the northern hemisphere. In both cases, changing air masses and the winds are important for inter-annual to inter-decadal variations, both in explaining cold winters over Eurasia and sea-ice around Antarctica.


108 Responses to “A conclusion of the 4th International Polar Year”

  1. 101
    Andreas says:

    Sea ice is now below 2007 in both extent and area even within the Arctic Ocean (Bering Strait to Spitsbergen, Siberian coast to Ellesmere Island, without Kara Sea; calculated from NSIDC daily data).

    extent area / Mm²
    2005-06-24 6.729 6.016
    2006-06-24 7.019 6.068
    2007-06-24 6.675 5.348
    2008-06-24 6.866 5.725
    2009-06-24 6.828 6.019
    2010-06-24 6.626 5.313

    Sea ice area isn’t reliable at this time of the year, but low values indicate extensive melt ponds. They developed about a week earlier in 2007, but quickly catched up this year because of very clear skies in much of the Arctic in the last days. They are also clearly visible even beyond 80° N in recent MODIS images

    Current weather forcasts are good for the ice at the Atlatic side of the Arctic (and maybe the Laptev Sea), but may cause increased ice export. Much ice in the Chukchi and East Siberian Seas looks already very rotten and will cease soon (well ahead of schedule, but not as fast as in 2007). Particulary bad news for the very old ice off the Canadian Archipelago. It will not melt (completely) in place, but become more mobile, and much of it will melt later in the Beaufort Sea. Some of it may intrude into the archipelago and block the Northwest Passage the next years. The most extensive melt can be expected within the archipelago. Most fractures dates will occur ahead of schedule (which was already well ahead of climatology). The parts of M’Clure Strait / Melville Sound that did consolidate at all, seem alread to have some cracks that weren’t present last week.

    Decrease rates in extent and area aren’t likely to accelerate as much as in July 2007, because Hudson Bay has already little ice left, but if the ice volume estimates are correct, much less extreme weather conditions than in 2007 are necessary to yield a new record low in Arctic sea ice extent.

  2. 102

    I have been looking at the satellite photos of the edges of GrIS for years, and I have seen what appears to be water vapor rising in enormous quantities from the edges that are deteriorating most rapidly, certainly when the melt lakes drain out all at once in a particular area. I have never seen this mentioned anywhere. Why doesn’t this get talked about? For a recent like event, look upstream of the Petermann Glacier, June 28, 2010, on this site: http://ice-map.appspot.com/

  3. 103
  4. 104

    These things are not always “clouds” — they generally occur when the melt lakes drain en masse. I have observed this many times. Well, they become “clouds,” yes.

    They also rise up out of the upstream portion of the Jakobshavn Glacier.

    Or, do you think that massive melt lakes draining out all on the same day have no such effect?

  5. 105

    Dear Andreas,

    You obviously know how to get the images from these locations on GrIS. In future, pay close attention to the areas where the melt lakes build up and drain out most rapidly. A particular satellite has gone offline, but it used to be possible to see the changes in the water temperature around the coast of Greenland when the melt water rushed out. You will absolutely see that there are unusual clouds just above the upstream areas of the large glaciers and also now along the rapidly melting edges on mid to north western Greenland.

  6. 106

    This is an old comment from 2008:

    6 Pat Neuman says: 8 October 2008 at 6:21 PM

    Phillip,

    Yes, heat released by condensation of water vapor weakens ice. Foggy periods turn lake and
    river ice black in spring.

    The significance of latent heat for snowmelt has been described by Dunne and Leopold (1978):

    “If water from moist air condenses on a snowpack, 590 calories of heat are released by each gram of condensate. This is enough energy to melt approximately 7.5 gm of ice, which when added to the condensate yields a total of 8.5 gm of potential runoff”.

    Dunne, T., Leopold, L.B. (1978) Water in Environmental Planning; pp. 477‑499.

    OK, so if numerous enormous melt lakes drain out whoosh! in a day, doesn’t this mean that a huge amount of heat exchange is going on, sufficient to create clouds above the general area?

  7. 107
    Hank Roberts says:

    > a huge amount of heat exchange is going on, sufficient
    > to create clouds above the general area

    Just guessing, but a volume of water going down into the glacier would displace a comparable volume of air, that would be pushed back out the upper opening; that could condense and make a visible cloud under some conditions. I don’t know if anyone’s measured airflow around those openings. I wonder if there’s any air path through the glacier.

    I’ve seen clouds form during wintertime dry cold weather, where a limestone cave has two openings, one high and one low — air inside the cave is relatively warm and humid, and the warmer air rising out the upper opening can make a noticeable cloud, drawing in air from below. (During hot summer weather the flow is reversed, and a wind of relatively cool air flows out the lower opening.)

    Just speculating.

  8. 108

    I have read somewhere that when the melt lakes drain out, the water eventually gushes out with great force from the bottom, and flows into the sea. One can see on the satellite photos great streams of greyish sediment coming out of the edges of the ice sheet. Last year, where the sediment could be seen flowing out to sea, other satellite graphics (not available this year) showed changes in the sea surface temperatures. I’m not trained in physics, so it is hard for me to imagine all the ways that heat can be exchanged while the lakes (which these days are staggering in their sizes) drain down in such short time frames. Certainly, the effect is not insignificant.

    Not so long ago, it was thought that the outflow from GrIS’s glaciers was the main source of mass balance loss, but more recent work shows that the melt runoff now comprises about half of the loss.

    If it is true that the mass balance loss is no longer linear but more exponential, while at the same time the proportion of melt run off to glacier outflow is increasing, then is not rate of increase in the melt run off growing more than the rate of glacier outflow?

    I shouldn’t be trying to write this at 1 a.m., but it seems to me, at least, to be one of the more important aspects of what is occurring on Greenland right now.

    On another thread there was also some mention of how the moisture hanging in the air over the ice affected the amount of melt. If the melt lakes running out created large enough clouds, wouldn’t this be a positive feedback?


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