Arctic dips as global waters rise (BBC)

By Jonathan Amos
Science reporter, BBC News

Arctic sea level has been falling by a little over 2mm a year - a movement that sets the region against the global trend of rising waters.
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It is well known that the world's oceans do not share a uniform height; but even so, the scientists are somewhat puzzled by their results.
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To find the Arctic out of step, even temporarily, emphasises the great need for more research in the region, the team says.

"We have high confidence in the results; it's now down to the geophysics community to explain them," said Dr Remko Scharroo, from consultants Altimetrics LLC, who led the study.

Next year has been designated International Polar Year, and major oceanographic expeditions are planned to take research vessels into the northern region to sample its icy waters.
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more: http://news.bbc.co.uk/2/hi/science/nature/5076322.stm

The ice melting, so the land rebounds because of less weight. This is geology 101 stuff.

That would explain changes found using the the yard-stick-in-the-habour method, but this is satellite data: Unless they're calibrating the data against "known" points on land, there could be something else going on. You'd certainly hope they would be smart enough to rule out rebound before hitting the press release...

If they're not calibrating against a 'known' land height, how would isostatic rebound explain a drop?

Sorry, I might just be being dim. It's been a long day :)

Isostatic rebound would only come into it if the ice that has
now melted was over a landlocked stretch of water (i.e., one
that would have transmitted the weight of the ice rather than
just being driven outside of the region.

(Or, as you said, if the measurements were being referenced
against a landmass suffering the same ... which defeats the
point of satellite measurements really ...).

(Now go to bed!)

and takes several tens of thousands of years.

several millions of tons of ice had been sitting on land which is now coastal areas in the Arctic. When this ice melted, the land beneath it rebounded, and is still rebounding, and will continue to rebound for several tens of thousands of years. Although geologically rapid, it's far from instantaneous.

A prime example is Hudson Bay, which had subsided due to continental glaciation, and is now rebounding. Hudson Bay will eventually disappear (unless of course there is another glaciation) and there will be a rather continuous plain from Nunavut to northern Quebec. Global sea levels may rise (and certainly are rising) in areas that are not experiencing rebound, but those regions that had subsided due to glaciation will appear to have sea levels that go down.

...what I don't get is how this would affect the level of the sea measured from orbit. This isn't sea-level appearing to go down compared to someone on a landmass undergoing rebound, it's sea-level actually going down...

I think the /. solution Skids posted is reasonable, but I'm still open to ideas. :)

They're full of it. Their satelite has been measuring for just 10 years, and they claim they've detected a change of 2.2 cm with respect the radius of the earth? A difference of 0.000000033%? That's simply immeasurable and could be due to any number of things from minor wave crests to their satelite's orbit decaying. I have no doubt that sea levels are dropping in the Arctic Ocean due to the reasons expressed earlier, but IMHO their data are effectively garbage.

It's been niggling the back of my mind, how they manage the accuracy they're claiming: For the moment I'm just taking it on trust, since they probably know more about it that I do. :)

Less ice, more water. Water is more mobile than ice and the cetrifugal force of the spinning earth throws it toward the equator, thus draining it away from the poles.

Since polar ice IS melting, that means that the water nearest the pole is less saline, and not had time to mix with warmer, more saline water?
It seems a very "logical" answer and is not based on any great knowledge on polar megageography, by any means.

= bulges at the equators.

Not my prognosis. Some /.er came up with it.

Damn, the collected genius of DU E/E outwitted by /. We live in strange and disturbing times... :D

AbE: How does salinity affect viscosity? Any takers?