Methodology:

Ice trackers were manufactured by Pacific Gyre (www.pacificgyre.com). The trackers are designed to survive harsh environments and ice conditions and are air-deployable at ~40 m or less. The trackers record GPS positioning and are equipped with Iridium 2-way satellite telemetry (the specification of the ice tracker can be found on the Pacific Gyre website, www.pacificgyre.com/ice-tracker.aspx). A total of 20 ice trackers were air-deployed during the Leg 5 of the MOSAiC expedition. The trackers were deployed near the North Pole and drifted to the south through the Fram Strait. The buoy array formed by the trackers ranges from sub-kilometre scale to tens of kilometres and can be used to calculate the strain rates (and the deformation), as well as general ice drift parameters.

Data collection:

The Ice Trackers were manufactured by Pacific Gyre (www.pacificgyre.com). The data collected in the trackers were transmitted to Pacific Gyre where they stored the data. The raw data files were downloaded from the web interface maintained by Pacific Gyre. The raw files contain the data before the deployment, so the data before the deployment were removed.

Data quality:

The data quality from the ice trackers can be affected by ice conditions and the position of the trackers. The trackers should be positioned upright to have a clear sky view for satellite reception for GPS and telemetry. Dynamic ice conditions can also affect the data quality and the failure of the trackers, e.g., ridging or deformation events can damage the ice trackers. In this case, the ice trackers stop transmitting the data. Therefore, some trackers were short-lived, while other trackers lasted longer. Some erroneous GPS positioning data can occur due to environmental factors mentioned above. These erroneous GPS positioning data have been removed through manual inspection of latitude and longitude coordinates. The ice trackers use a standard GPS receiver, so the typical positioning error is ~1-3 m.