I noticed yesterday that a polynya had formed in front of the Ronne Ice Shelf over the last 2 weeks.
In that image it is about 27,000 km2 in area.
I mapped the opening of the polynya from MODIS imagery over the last two weeks. There is cloud in the images but the opening of the polynya is fairly clear.
On 31 January 2017 there is no open water, but then over the 16 day period it opens to the ~27,000 km2 in area. If you're eagle eyed you can see that there is thin frazil ice forming in the open water in front of the ice shelf at the end of the sequence.
So what caused it?
Most likely off ice shelf winds. As the image from nullschool.net shows.
So I believe a sustained period of off ice shelf winds has pushed the pack ice north and away from the ice shelf.
If you look at my sea ice extent gif from my previous post The Amundsen Sea is practically sea ice free, you can see the polynya opening up at the end of the sequence.
Here it is in the data from 16 February 2017.
The Ronne polynya is common and there was an experiment a long time ago called ROPEX (RONNE POLYNYA EXPERIMENT) that was designed to study it. From that experiment there are a couple of lovely papers from Dr Emma Fiedler (University of East Anglia) on the heat flux. She published data showing heat fluxes over the polynya were ~150 Wm-2 for the fetches of ~100 km seen in the images above (Fiedler, Emma K. "Ocean‐atmosphere heat fluxes at the Ronne Polynya, Antarctica." Weather 65.1 (2010): 16-21, also her PhD thesis - Air-sea-ice interactions at the Ronne Polynya - is online as well.
So 150 Wm-2 x 27,000 km2 is ~4 Mega watts of heat being lost from the ocean.
In her thesis Emma works out ice growth rates and salt rejection contribution too. I may look at that over the weekend.