FDDs and Sea Ice Loss

At the end of my last blog post of the Slow Transition series I tagged on a comment and graph about Freezing Degree Days and CO2, I said I would need to think about it. Having been rather distracted by other matters it's taken some time for me to look at it. However I have now done so and in short I don't think CO2 is directly driving winter warming.

Mid November Status

Rather than just do a PIOMAS post, this post presents a few reflections on ice state in October as the refreeze progresses using various sources.

April 2014 - Start of the new season

If PIOMAS Gridded data is published I will be posting thickness distributions based on grid box effective thickness, and any other resulting comments. However as the main series PIOMAS data is now out it's worth going over some points I want to raise. It's also worth reading Neven's summary of the past winter, and the May PIOMAS update.

Siberian and Greenland geopotential height anomalies

Early last year I wrote a post on Eurasian snow cover, link, I've revisited this as part of my continuing attempt to explain the Greenland centred summer pattern.

Francis/Vavrus and the slower jetstream.

I've previously mentioned the Francis/Vavrus paper linking mid latitude persistent weather to Arctic Amplification, copy here, but haven't properly blogged on it. However I have drawn the paper in as a possible factor in the behaviour of blocking activity in a previous post. But the conclusions drawn there are not central to that post, merely an aside.

I say this because I'm pretty sure that the Francis/Vavrus paper is wrong in doubt. EDIT - amended in light of reading Dr Francis's response in the WP - see comments. 

Summer Acceleration

I have recently outlined the changes in the Cryosphere Today Area index (CT Area), using anomalies to examine the changes from the long term average seasonal cycle. I've shown the changes in the CT Area anomalies, link, the autumn response to increasing open water in the summer season, link, and the recent June anomaly crashes, link. I have also covered research showing the majority of surface based Arctic Amplification is a response to summer ice loss, link, and that this amplification is probably being understated by the GISS dataset, link. However I have not addressed a substantial issue, that of the summer acceleration loss of area when compared to the loss of winter area.

GISS LOTI and NCEP/NCAR Reanalysis.

In my last blog post (link) I outlined a recent paper that reveals some detail about the structure and cause of Arctic warming, in it I touched upon some concerns with reanalysis. It is notable that NCEP/NCAR doesn't tend to be used in studies of the Arctic, newer reanalysis products such as JRA-25 and ERA seem to be preferred by most researchers. However the reasons for this seem to be in details in literature I've not yet read, I'm not aware of any one paper throwing NCEP/NCAR temperature or pressure outputs into doubt in the Arctic. It would seem that whatever issues there are have not been enough to persuade the PIOMAS team not to use NCEP/NCAR.

But there is one issue I'm aware of; a growing mismatch between NCEP/NCAR reanalysis and GISS Land/Ocean Temperature Index (GISS LOTI).