Kiwis lead scrutiny of water below ice

Scientists in Antarctica have designed a device that can – quite literally – break new ground into how the planet’s systems operate.

The Kiwi-led project, working alongside scientists from Norway and the United States, has built a high precision supercooling measurement instrument to measure ‘‘supercooled’’ ocean water below the Antarctic sea ice.

Dr Inga Smith, of the University of Otago, said sea ice usually froze at minus 1.9 degrees Celsius but that was not the case when freshwater that flowed underneath an ice sheet mixed with salty seawater.

‘‘Then it becomes what is called supercooled, so it is still liquid but actually below the freezing point,’’ she said.

‘‘It then snap freezes into these crystals called frazil, they attach to the sea ice and form platelet ice.

‘‘That means the sea ice in this area is thicker and grows faster than it would otherwise, certainly thicker and faster than you would expect in the Arctic, for example, in a similar location.’’

The device was placed on an ice-fin – a small and remotely operated submersible robot – to analyse how cold this water got.

‘‘We are really pushing the edge of polar engineering here, operating in these really cold temperatures and making highprecision measurements of that supercooling,’’ Smith said.

Maren Richter, a PhD student from University of Otago, said oceans under ice shelves were a large black spot in scientists’ knowledge. ‘‘We know more about the dark side of the Moon than we know about what is going on underneath the Ross Ice Shelf.’’

Richter said the measurements were important as they helped inform understanding of how the ocean, the ice and the atmosphere all worked together and how they interconnected.

‘‘These are all calculated by large scale models and the more accurate we can make these models, even on really small scales like this, the more accurate it will be on larger scales like informing weather in the future in New Zealand,’’ she said.

The instrument was first tested when the team worked out of a containerised ice camp on McMurdo Sound, which connects to the Ross Sea to the north.

Antarctica New Zealand chief executive Sarah Williamson said the camp was key for the team’s success.

‘‘They managed to collect oceanographic and sea ice data for 17 of the 20 days at the ice camp, and [high precision supercooling measurement instrument] data on eight of those days.

‘‘It is always satisfying when we can support this world-leading science so successfully in Antarctica, particularly when it has such important ramifications for the rest of the planet.’’