An unusually large cyclone has been buffeting the Antarctic coast this week, shifting sea ice that had already been tracking at record-low levels.

While the storm in the Ross Sea is unrelated to events formed in the tropics, the cyclone is being watched closely by experts trying to understand how developments in the far south affect the wider climate in the southern hemisphere and beyond.

"There is an unusually large, non-tropical cyclone spinning in the Ross Sea sector, with extensive warm air wrapping around its eastern flank onto the Ross Ice Shelf," said Kelly McNeill, a communication manager for Antarctica at the Bureau of Meteorology.

"A similar event a few years ago saw light rainfall over that area, so it's not unprecedented but is certainly unusual."