'Unusually large' cyclone hammers Antarctic coast

Thursday, 25 January 2018

An 'unusually large' cyclone is buffeting the Antarctic coast. Video published in 2018.

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 communications manager for Antarctica at Australia's Bureau of Meteorology.

A cyclone spins in the Ross Sea, off Antarctica.

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

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Dr Jan Lieser, a marine glaciologist from Australia's Antarctic Climate and Ecosystems Co-operative Research Centre, said the storm would most likely redistribute the sea ice, and could have implications for any shipping in the region.

The transient storm had been particularly active in the past couple of days 'and would probably decay in the next 24 to 36 hours', Dr Lieser said.

'We are tracking at a record low sea ice extent, but it's not broken new ground yet,' he said.

White sea ice and snow reflect sunlight back to space. When they melt - as they have been globally, from glaciers to floating ice - more of that solar radiation is absorbed in the dark oceans, such as those surrounding Antarctica.

RECORD LOWS

The extent of sea ice at both polar regions at the start of 2018 remains close to record low levels.

Antarctica posted both a record low sea ice extent in 2017 and its lowest average coverage of about 10.6 million square kilometres for any year, according to the US National Oceanic and Atmospheric Administration, citing satellite data beginning in 1979.

For the Arctic, 2017 had the second-lowest sea ice extent and second-lowest average coverage.

Air temperatures are currently well above average (>10°C) in the high #Arctic polar cap (80°N+)… blue lines [1958] to yellow lines [2017]

[Graphics/Data: https://t.co/kO5ufUWrKq] pic.twitter.com/q0KreyZWD0

— Zack Labe (@ZLabe) January 24, 2018

Dr Lieser is helping lead the southern version of the Sea Ice Prediction Network, aimed at forecasting sea ice changes, echoing a service that has been operating for the Arctic for the past decade.

The first co-ordinated forecasts for the summer retreat of Antarctic ice should be available next month, he said.

Improved sea ice forecasts will help scientists hone their seasonal and longer-term forecasts, with particular benefits for southern hemisphere nations.

Unlike the Arctic, where the trend of shrinking sea ice has been clear since the 1980s, Antarctica has had much greater volatility - such as recording large coverage in 2014 before diving to record lows within three years.

The sea ice is affected by both oceanic and atmospheric conditions, with the ice sometimes moving in the opposite direction to winds if currents are strong enough.

This week's storm may well have had the opposite effect, with winds sufficiently powerful to overcome any current beneath the ice, Dr Lieser said.