It´s September and we have about two weeks to go till the annual Arctic sea ice minimum. As far as we can tell it´s going to be a close call – with a good chance that this year will beat all previous melting records.

That would then have to include the melting record of 16 September 2007, when the Arctic sea ice extent plummeted to 4.28 million square kilometers – 39% below average.

Arctic melting records of 2011

In the Far North there have already been silent melting records this year. In line with record-low sea ice during the autumn of 2010 in March 2011 the annual sea ice maximum turned out to be the lowest ever – and also in May, June and July there was less ice in the Arctic Ocean than ever before, including record year 2007.

At the end of July and in early August the melting slowed down somewhat – and the ice extent for August 2011 was larger than for August 2007. However in recent days the ice graph has kept a steady declining course and with just two weeks to go till the expected minimum, 2007 and 2011 are now in a neck and neck race, as the daily updates of the NSIDC show.

Arctic melting forecast

Much now will depend on the Arctic weather for the rest of the month, which means we can actually consult weather forecasts to get an idea of what might turn out.

Normally we can simply look at the Arctic Oscillation (AO) index, which describes the air pressure differences between the Arctic and lower latitudes. ‘A negative NAO’ implies high pressure over the Arctic and relatively warm air sinking down from adjacent regions, promoting further ice loss.

NOAA in its ensemble forecast expects the AO index has for the next two weeks about even chances of turning to a negative phase as it has to turn to a positive phase [although perhaps the latter would be slightly favoured].

Only the frozen water can melt

We can however also consult meteorological models to get to a more detailed forecast of the Arctic pressure chart. Because by now, as NSIDC imagery shows, much of the Arctic Ocean is already open water – and potential melting can only take place locally, at places where sea ice remains, as for instance around the geographical North Pole.

If we take a look at the air pressure forecast of the GFS weather model we see high likelihood of relatively high air pressure over most of the Arctic Ocean, with depressions [and possibly wind – another important factor] around its margins. With warm air sinking in on the eastern, the Russian, part of the Arctic, chances of further sea ice melting seem particularly high in the zone between Franz Josef Land and the geographical North Pole. The Canadian and Danish parts of the Arctic meanwhile may be better able to cling on to their cold air – keeping the water front at distance, for this year.

Expected surface temperatures for Saturday September 10 2011, according to GFS model. The thaw line runs right across the geographical North Pole, with warm air on Russian side, colder air in West.

Arctic pie challenge

So, wanna place a bet on what will happen this year? Will the 2007 record be broken? We’re not decided, but we’ll take the challenge. Loser gets to send a pie to the NSIDC. Let us know.

© Rolf Schuttenhelm | www.bitsofscience.org