Sea-ice trackers - Picture1

A GPS sea-ice tracker placed on McMurdo Sound land-fast sea ice. The tracker sends information on its position via Iridium satellite, allowing the break-out of sea ice this summer to be followed in real time. Photo: Inga Smith.

Sea-ice trackers: Using GPS and Iridium satellites to follow sea ice break-out events

31 January 2024

In the 2023 spring, researchers travelled to Antarctica to place GPS trackers on the sea ice. For the first time, multiple sea ice trackers are allowing the break-out of sea ice in McMurdo Sound to be studied in real time.

Understanding how sea ice breaks out will help understand the vulnerability of sea ice in a warmer world with higher atmospheric CO2 levels.


Inga Smith (University of Otago) and one of the sea-ice trackers deployed closest to the land-fast sea ice edge in McMurdo Sound. The land-fast sea ice covers roughly 2500-3500 km2 of McMurdo Sound by the end of September each year. With its reflective snow cover, sea ice plays a crucial role in keeping the Earth cool. Photo: Andrew Hefford.

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Pauline Barras (University of Canterbury), Inga Smith (University of Otago) and Sean Chua (Australian Antarctic Division) during the deployment of one of the sea-ice trackers. The team measured snow thickness and other properties as part of a project led by Wolfgang Rack (University of Canterbury), involving Christian Haas (Alfred Wegener Institute, Germany), Adrian Tan (Lincoln University), and field assistance from Andrew Hefford, Catherine Kircher, Zoe Glimer, and Glenn Smith. Photo: Andrew Hefford.

Tracking the sea ice break out

Seven GPS sea-ice trackers were deployed in November 2023 as part of an Antarctic Science Platform-supported project looking at snow on sea ice and polynya processes in a changing climate. Polynyas are sea ice-free areas that open up during storms.

The trackers were strategically placed on satellite tracks and at a location where information on sea ice growth through the winter was gathered by the University of Otago sea ice monitoring station.

Six of the sea ice trackers were deployed at sites reached by helicopter and one was deployed by Hägglunds vehicle.

The data from the sea ice trackers will be archived at the Alfred Wegener Institute, the German Antarctic programme, which is supporting the project's Iridium data transmissions.


Location map identifying sea ice tracker initial deployment positions as part of the Platform's Sea Ice and Carbon Cycle Feedbacks Project. Satellite image from Landsat8, 5 December 2023, map created by Greg Leonard (University of Otago).

Using GPS sea ice trackers and satellite information

GPS trackers, combined with Iridium data transmission, allow sea-ice motion to be monitored and investigated in real-time. When combined with satellite information on sea-ice properties, information on how the sea ice breaks up can be obtained.

A University of Otago PhD student will start analysing this information in April 2024, in a collaboration between Inga Smith and Greg Leonard (University of Otago), Wolfgang Rack (University of Canterbury), Christian Haas (Alfred Wegener Institute, Germany), and Stefanie Arndt (Alfred Wegener Institute, Germany).

Andrea Foley (University of Otago) has been working with Sandy Morrison (University of Waikato) and Inga Smith to develop outreach and education opportunities around the trackers for schools.

Sea-ice trackers - Picture5

Sea ice trackers map showing how the sea ice moves when it breaks out. This started happening in late December 2023 and is expected to continue into March 2024. This satellite image shows the positions of the sea ice trackers on 13 January 2024, immediately after the breakout of a large sea ice floe with one of the trackers on it. [mage: Satellite image from MODIS 13 January 2024, map created by Greg Leonard (University of Otago).

  • This research is part of the Antarctic Science Platform’s Sea Ice and Carbon Cycle Feedbacks Project. It contributes to knowledge of the role of polynyas in Antarctic sea-ice dynamics by providing quantitative data about sea ice movement following break-out events.