stay with PIOMAS
With such poor grid resolution in the Arctic Ocean proper and mediocre agreement with amended CryoSat, SMOS, Ascat roughness age, snow contributions, ice provenance, icepack motion and commonsense, how is it able to determine these subtle daily and monthly variations to such incredible nominal precision? The trick lies in not posting a netCDF which discourages quantitative comparison, using a virtual averaging volume which is not subject to observational calibration or validation, and getting a free reset on the periphery when the ice is all melted out at the September minimum.
That last dip (in red) was probably due to the storm, I guess.
Right. This was a very unusual event completely attributable to strong persistent winds blowing up the Fram. Despite some nonsense on twitter, it had nothing whatsoever to do with melting ice, föhn winds coming down off Greenland, bizarre warmth at KMJ, upwelling (Kaffeeklub and beyond are far too shallow), or a stable new polynya (it froze over almost immediately as shown by WorldView VIIRS cracking).
There's also been serious confusion about "dynamic" ice thickening of Arctic Ocean ice. Rheological deformation of ice is real enough in thousand-meter thick Greenland and Antarctic ice sheets (eg previous discussions of deviatoric stress tensor invariants as supported by ice-penetrating radargrams) but it's only a
useful metaphor for the ice pack in
continuum mechanics-based modeling (eg CICE elasto-viscous-plastic deformation intended for fully coupled global climate models).
If you are standing out there on the ice, you won't experience any dynamic thickening. Instead, at the scale of large floes or along the all-important marginal ice zone,
solid mechanics fracturing is at work:
Formation of an aggregate scale in Arctic sea ice.
MA Hopkins, S Frankenstein, AS Thorndike
J. Geophys. Res. 109, C01032 (2004).
http://onlinelibrary.wiley.com/doi/10.1002/2015JC010909/fullIn this event, the southerly component of North Atlantic deformation was, unsurprisingly, taken up by the Kara tongue intrusion where it was sliced earlier passing around Ushakov Island. Contrary to climate-site tweeters, rifting and ridging flares are easily seen on Ascat despite its resolution -- it may have only 85,000 pixels for the Arctic Ocean proper but they're all grid cells. (Mostly we see heavily interpolated sparse grids; turning interpolation off is a Panoply option.)
Here the issue is a perceptual misunderstanding: a ragged line of contrasting values is reliably recognized (bottom 70º azsimuthal Ascat bump map contextual animation) even if only one pixel wide for one day of a time series whereas the same number scattered over the image would be seen, if at all, as noise. (Sentinel-1AB confirms this.)
The new ice is currently being compressively squashed against the coast, moving westward along the coast and heading out the door to the south under persistent northern winds associated with this week's meandering weak high. The East Greenland Current works as a rachet: ice leaves with the surface current and doesn't come back.
Here the current was temporarily overwhelmed by an opposing wind as far as drifting surface ice was concerned. However import of previously exported ice from the Fram has proven transitory in the past, under weather patterns of the satellite era.
Where exactly does the East Greenland Current begin to kick in? Ascat and VIIRS time series showed during this event that it's quite a ways farther north than the latitude line connecting Nord Station with Svalbard. On the bottom animation (which pushes very hard on Ascat using transient 32-bit grayscale to mitigate lumping), the dividing line on the newly formed ice shows up clearly: some is going west, the rest is going south.
Fram floe trajectories are very similar to kayaking down a river. At low gradients you have to paddle, be that with or against the wind, because the river pools up and resembles a lake. As the gradient steepens above the head of a rapid, your boat gets caught up in the current and downriver you go, regardless of wind. Except here the wind was strong enough long enough to blow your boat back upriver.