So I think Gerantocrat has made a mistake, today's gain of 7k is probably some 13k lower than average daily gain for this day (as is made clear from the graph, with the red line ending at least 10k below the blue line.
Having just been reading about selective blindness I'm not all that surprised to notice (after several good looks) that there are two blue lines - a smooth "Av. daily change" and a very jumpy "Polynomial (av. daily change)". And the red line does end up at a possible 1k above the second, polynomial, line - whatever that means.
Me? Make a mistake? I can feel a Trump response coming on. Damn. I do not Tweet.
Instead, I have adjusted the graph layout a bit (not the data). See attached.
Read this very carefully, I will write it only once
The wobbly blue line is for each day the average of the last 10 years. And yes, it is very wobbly or wavy. Hence the x2 polynomial smoothing line, was blue, now dark violet to show the direction of travel.
(We had a discussion last year sometime about whether there was any chance of linking waves of above and below average extent gains and losses to movements of wind, waves, currents, warmth and cold around the Arctic - without any conclusion.)
So on the 17th February, the average of the previous 10 years was a gain of just 885 km2. That is the reality of the JAXA data.
The smoothed line is an artefact, i.e. does not actually exist.
___________________________________________________________
artefact - definition
something observed in a scientific investigation or experiment that is not naturally present but occurs as a result of the preparative or investigative procedure.
"the curvature of the surface is an artefact of the wide-angle view"
____________________________________________________________