This is complex, but the following explanation deals with some factors in an easy-to-read form….
The Antarctic sea ice melts almost to the coast each summer.
The winter sea ice has increased by around 1 % over the last few decades.
This is not difficult to explain.
All linked to melting of the land ice on Antarctica…..
Seawater will not freeze until it is around minus 2 degrees C, due to the salt content.
This effect of salt, of course, is used to help defrost roads.
The meltwater off Antarctica’s ice sheets is freshwater.
Freshwater has a low density, so it forms a layer on the sea.
Freshwater freezes (of course) at zero degrees C, so a layer of ice can form more easily on top of the sea.
Also windchill helps to freeze that top layer.
A useful comparison of Antarctic and Arctic sea ice ……
See especially the comparison chart at the end.