2011-06-25 03:52:42Wind driven sea ice export


Hi, a denier here in Iceland is highlighting an article by Smedsrud et al 2011 (Recent wind driven high sea ice export in the Fram Strait contributes to Arctic sea ice decline).

Has anybody heard of it and would you call it skeptical towards AGW?

It looks like it is still under review, am I right?

2011-06-25 04:50:28


Strong wind contributes to lower sea ice area according to NSIDC (may report)

- Arctic weather in the next few months will be a critical factor in how much ice remains at the end of the melt season. New research led by James Screen at the University of Melbourne shows that the storms that move northwards into the Arctic from the lower latitudes during summer strongly influence sea ice extent at the end of summer. Years with dramatic ice loss, such as 2007, have been associated with comparatively warm, calm, and clear conditions in summer that have encouraged ice melt. Summers with slow melt rates are opposite and tend to be stormier than average. The number of storms influences how warm, windy and cloudy the Arctic summer is.

- Screen, J., I. Simmonds, and K. Keay. 2011. Dramatic inter-annual changes of perennial Arctic sea ice linked to abnormal summer storm activity, J. Geophys. Res., doi:10.1029/2011JD015847, in press.

The research is a bit contradictory - ice transport leads to spreading of the ice which lead to more heat uptake (less reflectivity), so although winds contribute to ice spread, the primary driver for increase in ice loss is from below as a result of more heat uptake from the oceans as a result of less ice cover - a classic ice/albedo feedback.

See the following seminar:

Climate Change and the Arctic Ice Cover

UPDATE: Strong wind contributes to higher sea ice area according to NSIDC (may report)

2011-06-25 04:51:53
Julian Brimelow

Re still being in review-- that is my take Hoskibui.

This is nothing new really.  We know that wind patterns play an important role in modulating the ice are/extent.  But does this explain the loss in ice volume?  Is the increased transport part of a positive feedback, related to a tendency towards more positive AO as the Arctic warms rapidly?

They also conclude that:

"The positive trend is produced by a trend in the local pressure gradient, related to intensification of cyclones over the Nordic Seas."

My take on this is that this may , inpart, explain why the models are underestimating the loss of sea ice.

Worringly they postulate that:

"The sea ice area export in 2009 and 2010 was lower than for the previous years, 2005, 2006, 2007 and 2008, perhaps indicating that the sea ice export may return to more moderate levels again soon."Sadly the deniers will cling onto that.  And sadly, I suspect that the authors will be wrong....

They also say:"The dramatic loss of Arctic sea ice the last decades is thus only partly caused by in creased long-wave radiation related to ongoing atmospheric CO2 increase (Smedsrud et al., 2008).  A number of feedback effects have contributed once the ice thickness decreased (Perovich et al., 2008; Rampal et al., 2009; Screen and Simmonds, 2010), but as demonstrated by the General Circulation Models, additional forcing is needed to explain ongoing changes."

I would challange that assertion/conclusion.  Just b/c the wamring set in place by AGW has led to Arctic amplification, does not in anyway diminsih its importance. They could have worded that much better IMHO.

2011-06-25 05:07:26
Daniel Bailey
Daniel Bailey

Yes, still under review (most recent review comment dated 13 June).

Quite frankly, I fail to see how anyone reading this can take it as being skeptical towards AGW.

The main finding is that advection out the Fram (wind-driven ice export) has increased in the period 2004-2010; this is no surprise to anyone following the Arctic sea ice.  The main reason for the extremely low ice totals from 2007 was a very strong Arctic Dipole, which caused an extremely large amount of ice to be advected out the Fram.

Without that Dipole, 2005 and 2008 would have had greater melt volumes.

The underlying reason, other than winds, for increases in advection is that the ice is so much thinner than that of pre-1980 levels (where average ice thicknesses were in the 8-10 meter range with pressure ridges upwards of 25 meters thickness).  First year ice is now in the 1.4 to 1.8 meter range, with overall thicknesses in the 2.3-3.5 meter range (FY+MY ice).  A thinner pack is more easily fractured, with the rubble filling the leads to a greater extent.  This causes the Area and Extent metrics to remain almost anomalously high relative to the volumes being lost.

Increased winds over a solid pack from the 1970's could not advect the quantities of ice now commonly occurring in the Fram.

Bottom melt is also increasing due to greater penetration of warm currents into the Lincoln Sea from the East Greenland coast and through the Bering Straits from the Pacific.  This has pushed ice losses from melt from about 40% of all losses to nearly 60%.

This has also resulted in a thinning of the mixing layer under the ice, bringing the warmer waters from the deep towards the surface.  This is the mewchanism driving the increases in bottom melt.

To sum, what is left of the pack is a rubble-strewn slushie (a fruity drink available at many fast food outlets).  Superficially, it seems mostly like itself from days of yore, but a strong weather system can drive an obscene amount of advection & also serve to slosh around the slush even more, further thinning the mixing layer, driving increases in ice loss (smaller bits have a larger overall surface available for the warmer waters to then melt).

This study is a clear marker that the Arctic ice is doomed.  There will be no recovery in human timescales.

2011-06-25 05:08:29
Daniel Bailey
Daniel Bailey

Hey, no fair typing faster than me!

2011-06-25 07:12:34


Yup, under review but already misinterpreted - surprise ;)