October 21, 2005 ice and snow cover is shown here.

October 21, 2006 ice and snow cover is shown here.

It looks like global warming is continuing to take a slight pause. Both snow cover and Arctic ice extent are up.

As always, I mention that this is weather, not climate, and is likely just part of the normal year-to-year variation. The Arctic ice cover long-term trend remains downward.

The thing that has impressed me about this years ice recovery is the aggressive ice growth in Atlantic waters. In a few isolated Atlantic spots, current ice extent appears to slightly exceed the long-term (1970-2000) average.

Sea ice extent this year was the fourth-lowest on record, which is greater than had been expected following 2005′s record low.

It looks like 2006 will not be a record low ice extent. In fact, it may end up third or fourth from the lowest. That is quite a change from 2005.

To me, the most interesting plot is the one of ice extent versus time (months of the year). Note how we were headed towards a record low as late as July, but then conditions shifted and the Arctic was able to “keep its cool”.

This is about the time that the hurricane season sort of collapsed and the weather charts started showing faster movement of systems in the mid-atmosphere.

I wish we knew why.

In fact, it may end up about 4′th lowest, assuming no late-season warm fronts.

Ice area (the area covered if all the ice was squished together) should also not set a record low this year.

This, of course, is weather, not climate, and is not a trend so far as I know.

What’s interesting is that a lot of ice was preserved this summer when Arctic weather patterns shifted to a cloudier, stormier pattern in late July. The power of clouds and water vapor!

This coincided with a strengthening of 500mb winds (the ones that help shove weather around). Here in the 30N western hemisphere we are still seeing stronger-than-normal upper winds, which have brought us our first real cool front of the season.

Looks like the Arctic sea ice is close to its September minimum. 2006 should not be a record low. September southern hemisphere (winter) sea ice is a few percent from its 30-year record high.

The NOAA Arctic watchers agree that Arctic cloud cover was heavier than normal in August, and actually cooled the Arctic a few degrees below (30-year mean) normal.

Forecasted upper-air patterns will make it tough for any major hurricane to threaten the US in the next 10 days. The historical peak of the season is September 10 (Sunday) and, historically, the season winds downs relatively fast thereafter. Steve M’s musings about persistence look to be on the mark.

I’d seem to me that after nightfall in the arctic, i.e. for six months, there will be little evaporation due to no energy (from the sun) to overcome the latent heat of evaporation, though there will be some from wind. This probably means there are few clouds except around the edges where there’s snowfall from “incoming” air. This would mean that mostly there will be clear skies. Where there is ice, the surface temperature will drop rapidly and then the ice will act as a barrier for passing heat through to the surface. Where there’s clear sea, huge amounts of energy will be lost to space, even with added CO2 to slow things a mite. So, the upper waters will quickly be reduced to the freezing temperature and then ice will form. I’d be nice to have a reference to heat loss from ice according to thickness if anyone knows of one. (I’ll go looking after I post this and report back if I find anything useful.) I suspect that even if all ice were melted in the arctic, the time to complete icing over of the arctic circle wouldn’t change too much.

To me, cloud cover plays a major role in whether ice melts or freezes. If the Arctic sun shines in summer, ice melts. If the sun is blocked by summer clouds, the ice melts only slowly. If Arctic skies are clear in the winter at night, temperatures drop. If wintertime night skies are cloudy, there’s less cooling.

I’d like to see some kind of Arctic cloud cover index, to see if there are patterns. I know there are weather oscillations, like the NAO, but I have not seen data on how things like that affect cloud cover.

I will make somewhat of a forecast here.

At present we are at, or very near, the Northern Hemisphere annual extent minimum. Depending on which measures you use, we are either equal to or slightly higher than last year in terms of extent on the same date. I predict that we will reach this year’s minimum at an earlier date than we did last year. I predict that 2006 will not be an “all time low sea ice extent” at the minimum.

There are some areas where barring a major reveral, extent is already clearly in “fall” mode.

The lower extent in the Eastern Arctic (as a result of the known positive SST anomaly in the NE Atlantic) is balanced by the extent in the Western Arctic. Beaufort Sea and Chuckchi Sea both currently have a zero anomaly according the Cryosphere Today.