Heavy sea ice conditions near Mawson research station have resulted in further changes to the Australian Antarctic Division’s shipping schedule.

Voyage 4, the current voyage, was due to resupply Mawson. However, as happened in 2011, the sea ice in the area is unseasonably thick. This has prevented the ship from entering the harbour at Mawson and doing the resupply.

Sea ice is affected by such things as sea temperature, wind patterns, ocean currents, freshwater melt from the ice cap and snow fall, and so patterns vary each year and are inconsistent between areas.

The Australian Antarctic Division had hoped that the sea ice would have broken out by the time Aurora Australis had completed the summer changeover at Davis research station.

Aurora Australis is now expected to arrive back in Hobart on 1 March, having visited both Casey and Davis research stations.

The ship will return 43 passengers from Davis, as well as valuable ice cores from a successful five-week ice coring project at the deep-field camp, Aurora Basin.

The ship will be reconfigured for the next voyage, with the loading of essential cargo and dedicated fly-off equipment for a limited Mawson resupply operation.

On the ship’s return to Mawson, four helicopters with longer range flying capability will be used to deliver up to 50 000 litres of fuel, as well as 24 tonnes of food and essential cargo. Fifteen expeditioners will be transferred to the station for the winter, while 20 expeditioners, who have spent the past year at Mawson, will return home.