Wednesday, February 6, 2008

Heat Transport to the Arctic

This last year we saw a warm winter trigger some form of wind oscillation that carried a lot of heat from the lower latitudes into the Arctic, accelerating the melting of the sea ice. With the onset of winter, the clock got fully reset and we have been apparently treated to a cold winter not seen for at least a decade. These are hardly the conditions likely to trigger a movement of warm air into the Arctic this summer. The remaining question is whether or not the melting sea ice this summer will be able to eliminate all the sea ice grown this winter. This is not am exact science, but the wind does matter here in positioning the sea ice for best results and the 2007 season was historically unique in just that.

However. one season is a drop in the bucket against a twenty to forty year reduction in perennial sea ice whose actual history we know nothing. We have only just figured it out that we should have been measuring the changes in the last decade. We may be in for short cycle of ice accumulation lasting until the next solar cycle, upon which we will then get another cycle of major ice reduction.

As I have said yesterday, Solar variation is the major climate driver, small as it is, and it has been operating undisturbed for the last couple of hundred years. And if it were to continue undisturbed, we can expect the Northern climate to optimize around a temperature profile not unlike the middle ages when it was warmer.

Seeing the direct impact of a shift in the wind delivery system at work also reminds me that we have ignored the other great decadal cycle of the hurricane seasons. This weather regime is vastly more energetic than anything which hits the Arctic, yet it too fluctuates significantly over a cycle that may also be linked to solar output. Unfortunately, our data collection will need a whole century or two in order to draw any such conclusions. The necessary satellites went up, I think, in 1969.

In any event last years melt in the Arctic was sharp and dramatic, but as I have posted, does not necessarily mean that much extra heat was applied. As I have pointed out a constant and sufficient imbalance in heat delivery lasting decades will look exactly the same in the last stage of ice destruction. The wind merely shifted it around more than normal.

The question then remains about the source of this imbalance. Is it solar? Or do we have a larger input from the Gulf Stream? This too would be incredibly hard to quantify. Velocity changes have been noted. This was at first interpreted as a reduction of heat flow because the speed had slowed. But that could actually reflect a much larger volume and real heat content.

So the fact that the gulf stream velocity has slowed since 1959, may actually mean an increase in heat transport into the Arctic has occurred. Right now, I don't think we have enough data to trust any conclusions whatsoever. It is just that an apparent change took place over the same time scale as the perennial sea ice was reduced by sixty percent and they really have to be linked.

In any event, the hypothesis that atmospheric heat transport is the primary engine of sea ice removal will get a good test this summer, since we are now running a true cold winter in direct comparison to last year's warm winter and warm summer.

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