The science of monitoring sea ice

Winter science at Casey

As an expeditioner living on station, it can be easy to forget that our purpose for being here is to support the science projects that gather data from this environment to better understand it and also monitor changes that may assist with environmental predictions. There are a variety of science projects that are supported by the Australian Antarctic stations that observe anything from moss growth, to wildlife habits, to lake sediment.

The annual assessment of the fast ice around Casey’s station operating area went ahead this season with the help of Casey’s wintering population. Casey observations provide crucial information into the international Antarctic Fast-Ice Network. Ten selected sites were visited almost weekly to measure the ice thickness, the freeboard (how much the ice column is floating above the water level) and the snow depth.

Another part of the project was to deploy multiple motion and sound detection instruments onto the large area of fast ice just offshore from Jack’s Donga, an area known as the Swain Group of islands. Three different types of buoys were deployed, making nine units in total. These measure how sea ice modulates waves and if, when and where waves break the sea ice. Understanding these processes is critical to assess the changing impact of atmospheric forcing on the ocean and the sea ice in a warming climate. The project will also inform numerical weather prediction models, with a view to improving forecasts globally, including for Australia.

One of the buoys is designed to remain on the sea ice when it breaks out. It transmits its location via the Iridium network, the same one that we use for our satellite phones and satellite tracking. Since a recent breakout, the ice has travelled well over 100km from station – as seen in the graphic below.

Ice cores were also taken from some of the sites. These are stored in a freezer and sent back to Australia so the scientists can understand the makeup of the sea ice layers that relate to the rest of the data they receive. A hollow drill bit is used which captures a core inside (incredibly satisfying to pull out from the sea ice layer).

Thank you to all who helped with the field work and provided the required support from station.

Flynn Jackman | Field Training Officer

A man drilling into sea ice, leaning his weight onto a hollow drill bit over a metre long stuck perpendicularly into the ice. Another man is stretched out on his side beside the drilling hole, pretending to hold the bit steady and smiling at the camera
A man drilling into sea ice, legs braced wide as he leans onto the drill bit to drive it through the ice. He has turned his face up to smile at the camera. In the distance behind him, the tops of icebergs can be seen emerging from the sea ice, looking like dunes in a white desert
An ice motion buoy on a vast stretch of sea ice. The buoy is enclosed in a case that looks like a yellow lunchbox with a small antenna attached. In the distance, icebergs can be seen emerging from the sea ice, looking like rugged, blue-white cliffs rising from a white plain
A man in a thick winter jacket and gloves, kneeling on one knee beside an ice motion buoy on a vast stretch of sea ice. The buoy is enclosed in a case that looks like a yellow lunchbox with a small antenna attached. In the near distance to the left, part of an iceberg emerging from the sea ice can be seen, looking like a blue-white, steep-edged cliff rising from the flat, white ground
Three graphs showing data from the ice motion buoy. The first graph plots the buoy's trajectory on a map, showing its drift about 4 degrees of longitude to the west and 1 degree of latitude to the north of Casey Station. The second graph plots the buoy's drifting speed against the date. The speed generally varies from 0 to about 1 kilometre per hour day to day, with the exception of 16th-17th October, when it almost reached 4 kilometres per hour. The third graph plots the significant wave height measured by the buoy against the date. The wave height has stayed close to zero most days, excepting the 17th of October where it reached almost 1.2 metres
A man in a thick winter jacket and balaclava is lying on the sea ice connecting a cable to a hydrophone, a device enclosed in a case which looks like an orange lunchbox. The other end of the cable goes down through a hole drilled into the ice next to him
A hydrophone enclosed in an orange 'lunchbox' case lying on the sea ice. A black data cable plugged into the rear of the case unwinds down into a small, deep hole cut into the ice, into the water beneath
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