Friday, 4 March 2016

Extreme Arctic Warmth Continued into February

NCEP/NCAR temperature data is now out for February 2015, it shows January's staggering warmth in the Arctic continuing.

Using the simplest model of sea ice growth, outlined here, it is possible to create scenarios to see what the effect of this anomalous warm is on sea ice growth.

Let's assume that thickness for a given chunk of ice is 1.00m on 31 December. We then apply the average temperatures for 2016 Jan and Feb, and the period 2007 to 2015 for the same months, to the model for 31 days (Jan) and 29 days (Feb).

Sea ice thickens to 1.49m using the 2016 temperatures and 1.60m for the 2007 to 2015 average temperature. In other words this winter's warmth would only result in 11cm less thickening, not a crash in thickness. This is simply because although this January and February have been staggeringly warm compared to what one would expect, at -19degC it is still damned cold, easily cold enough to thicken ice of 1m thick.

PIOMAS data will be out sometime over the next few (working) days. I have clarified with Cryosat 2 (Thanks to Alan Muir), the last volume/thickness point there is for Feb 2015, they will be updating to 2016 'shortly' once ESA have released a reprocessed data set which is not comparable to the existing volume series. It would be good to compare Cryosat for March/April with last year as a check on PIOMAS given the highly anomalous weather this year.


DrTskoul said...

7% less ice is 7% more energy to go elsewhere in the system...

Chris Reynolds said...

Dr Tskoul,

Quote right. And the simple calculation above doesn't take into account snow, if the current warmth is due to influx from lower latitudes then the ice may not have thickened as much due to increased snow thickness.

But, if I take April volume for Beaufort/Chukchi/ESS/Laptev, and calculate the difference from the 2007 to 2015 average volume I get:

2007 -4%
2008 -1%
2009 -1%
2010 23%
2011 -13%
2012 7%
2013 8%
2014 -12%
2015 -7%

The biggest factor in all the post 2007 melt season minimae has been how active the Arctic Dipole (AD) anomaly has been. I don't know how active it will be this year. Presumably there is some sort of role in the current weather for the El Nino, and it may be present through the summer. Given that current conditions are so abnormal, will we see a super enhanced AD, or will the AD be suppressed this summer? I don't know, the answer to this.

I will rely on PIOMAS, and when it's available Cryosat, to gauge the impact of this weather. So close to the release of PIOMAS data there is little point guessing what effect February will have had. My point is just that the warmth does not mean a crash is certain.

Anonymous said...

Is this reanalysis for a surface (2 m air) temperature or the temperature of the sea/land/ice surface?

I think it's the former, though I can't find specific documentation.

If it's the air temp., then your simplified analysis assigning it as equivalent to the ice surface temp is missing a big factor; the surface of the ice, or snow, is likely colder than the 2 m air during the winter darkness due to the heat flux via radiation to the dark sky being so much greater than the expected convection flux to the air. The overall influence of the elevated air temp is thus somewhat less than this quickie analysis. The overall conclusion remains though, there is no indication of a precipitous crash of the ice thickness.

I would also note that any return to average, or below average, temps during the same season would prompt the thinner ice to close the gap because of the expected growth rate vs thickness effects.

Nightvid said...

PIOMAS for the month is out!!!

Chris Reynolds said...

I'm on it Nightvid.