It says the problem right on the site
Special Sensor Microwave Imager and Sounder (SSMIS) on the Defense Meteorological Satellite Program (DMSP) F-17 satellite that provides passive microwave brightness temperatures (and derived Arctic and Antarctic sea ice products) has been providing spurious data since beginning of April. Working on resolving problem or replacing this data source.
Or in other words, the Satellite is broke
Must be polar orbit. One satellite for Arctic and Antarctic. Off in opposite directions at both poles. Strange. If it was a satellite problem, you would think it would be off the same direction at both poles. Perhaps a planetary wide phenomenon is occurring ? Need to see if other polar SATs are affected. Microwave wavelengths?
Thank you, FINALLY, at post 31, you told us what the “note in red” said. SHEESH!
Belated reply: I’m almost certain that the explanatory message wasn’t there the previous day, when I first saw the weird data, because I looked for such a message and didn’t see one. I didn’t look the second day because the site was still showing the (updated) weird data, and it didn’t occur to me that they’d continue to post bad data once a problem had been noticed. Still, it seemed likely that the data was messed up.