Sunday, 29 July 2012

Here we go again...

In 2007 the Arctic lost a quarter of it's September minimum area, leading to a new record minimum, this was matched last year. Looking at the state of the Arctic sea ice at present I think we're likely to have another massive loss and soundly break 2007's record. Any earlier in the year and I'd be very sceptical of claims that ice conditions could tell us anything about the state at minima, indeed I have stated my scepticism about the long term impact of thin ice over the Barents Sea during Spring. That thinning was connected to the Pethoukhov/Semenov pattern cold Winter snap in February this year, see here. Yet the ice edge is Barents is now no different from, for example, 2011. But large scale persistent patterns of low concentration this time of year do have an impact on the coming minimum ice state.

At present much of the area between Beaufort and the Siberian coast is showing very low concentrations. This image is from Bremen's SSMIS site for 27/7/12. This is not just a few days of fleeting low anomaly, it is persistent, and in my view very likely real.

To keep it over the relevant period, I've uploaded a copy of Bremen's last 31 days movie below.

This shows that the anomaly starts to be very apparent from around 20/7/12. However this is really just the penultimate phase of a process that's been ongoing for longer as seen in the false colour Bremen plots. e.g. 5/7/12 10/7/12 15/7/12 20/7/12.

How unusual is this? Cryosphere Today has a page allowing the comparison of pairs of dates of sea ice, however there is a gap around July for both 2009 and 2010. Here however are the available years 2012,11,08,07 - 2012 shows an abnormally low concentration from Beaufort to Siberia.

The detailed pattern of concentration varies from day to day, however the area from Beaufort to Siberia does show a consistently low concentration. Looking at the period since 2003 for 27 July using Bremen's archives (AMSR-E, SSMIS) supports the idea that this low concentration is very unusual.

Such regions of low concentration are likely to largely melted out by September, for example this happened in 2003.

Due to the failure of AMSR-E and the switch to SSMIS mean that we are seeing an artefact of SSMIS and that this is really something like widespread melt ponds? As Bremen's webpage warns, because of this change the SSMIS maps should be used carefully. So is the low concentration merely an artefact of the loss of AMSR-E and the change to SSMIS? The condition of the ice shown by SSMIS in the anomalous area seems to supported by Terra/Aqua, where breaks in the cloud allow.

Bands 1,4,3 (true colour)

Same shots but bands 7,2,1 (false colour which shows the ice/ocean better)

The 2007 record minimum stands for all indices but Cryopshere Today's area, which was broken at 2.90 M km^2 last year. My bet is that this year we'll see the 2.9 barrier broken, significantly. My guesstimate is from 2.85 to 2.5 M km^2 at the daily minimum for Cryosphere Today's area metric, depending on what the weather brings. I do not think a figure above or close to 2.9M km^2 is plausible.

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