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The old man has been doing all sorts recently, but nobody else seems to have picked up on this, so:

A quick glance at the Cryosphere Today website Northern Hemisphere anomaly shows that this common metric of climate change is close to -2 million Km2. This is a first, by CT’s measure. Of some concern is that a proportion of this is attributed to losses in the Arctic Basin, which might normally be expected to be stable at this time of year. Earlier in the season, a noticeable thinning in the Basin area to the North of the Beaufort Sea was clearly visible on the CT site, the NSIDC near-real-time graphic and, most noticeably, on the excellent PolarView/Damocles site run from Denmark. This thinner ice is still clearly visible. It is not far distant from the area which, late last year, saw a large polynya, followed by an unusually large open body of water. There is now also an apparent thinning on the ‘Russian side’ of the North Pole, too. There also appear to be a relatively early retreat of the sea ice around the East Greenland Coast. The assumption then, must be that the current situation is a response of young and first-year ice to anomalously warm conditions. That there has been anomalous warmth can be verified by looking at the Canadian Ice Service’s page, or similar products from AARI or NOAA’s Alaska page.

In the meantime, the sea ice level in the Southern Hemisphere is nearly +1 million km2; this is also an unusually large figure. The total mass balance of global ice, therefore, has not reached extremely low levels, but as the reasons for such anomalies in both hemispheres is still somewhat unclear, this is not necessarily a cause to ignore what is going on in the NH.

Given the very recent discussions about the stability of the ice sheets, and their possible dynamic response to sea ice losses, in the NH in particular, two new papers seem to fit well here. The EGU has just instituted a new journal, The Cryosphere, in which there is a paper under discussion: Thresholds in the sliding resistance of simulated basal ice (open text and available for discussion). At the same in, in GRL, there is: Two modes of accelerated glacier sliding related to water (abstract only unless you subscribe). Both papers report what might be called a ‘dynamic’ response to changes in the flow of ice, which in turn, has implications for glacial outflow. If this is the case, we can expect further reports of accelerated glacial outflow, in East Greenland in particular, as has recently been reported.

This doesn’t mean that there’s going to be a rapid acceleration of sea level rise; the contribution of glaciers is still relatively small. It does, however, lead to two points. Earlier in the year, the Old Man gave his reasons why there might be a record low in NH sea ice this year. The recent shift suggests that the odds of this may have shortened in the past couple of weeks. It’ll still be a close run thing, but this might be a score for the old man; we have ten to twelve weeks to wait yet before the Summer minimum is reached this year. And a couple of weeks ago, a lot of discussion about Hansen et. al.’s ‘2 metre sea level rise’ followed Rasmus Benestad’s estimate on RC of a plausible 1 metre sea level rise this century; the old man nas gone somewhere in between.

By next Summer, we should have figures for glacial melt for the GIS, properly calibrated and adjusted, from on the ground and satellite measurement; it is reasonable to imagine that, if there is to be a dynamic response from the GIS to global temperature change, then this should show a continuing increase in glacial flow speeds. Alarmists might note the x5>x9 increases mentioned in the GRL paper, but these do not directly correlate to the expected rate of change.

In the meantime, the old man is grateful that cave isn’t in Pakistan, Texas, Yorkshire or any one of a number of places experiencing disastrous weather at the moment; the victims have his sympathy.

Be loved.


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July 2007