Rapid sea-ice drift during MOSAiC in 2020
15 May 2020
The Norwegian Meteorological Institute continuously monitors the Arctic Ocean with the help of satellites that orbit the Earth. Every single day, information products that describe the Arctic sea-ice environment are prepared. For example: information on where the sea-ice edge is, how thick the ice is, and how fast it’s moving (also known as sea-ice drift). The data prepared for the Ocean and Sea Ice Satellite Application Facility (OSI SAF) is freely available (see and access date here). It also includes how the data is prepared. The following analysis concerns the MOSAiC expedition in the last four months. A team of scientists at the Norwegian Meteorological Institute and Norwegian Polar Institute used satellite-derived sea-ice motion information to track the MOSAiC floe. They wanted to check if MOSAiC really drifted faster than it would have in recent years. A first version of this story was published as a joint post by the Norwegian Meteorological Institute and the Norwegian Polar Institute.
Drift analysis of MOSAiC January – April 2020
Following in the footsteps of Fridtjof Nansen and his Fram expedition more than one hundred years ago, the research vessel RV Polarstern has been frozen in the Arctic ice pack since October 2019, and is drifting across the Arctic Ocean toward Svalbard and the Fram Strait. In 1893-1896 it took Nansen’s vessel Fram nearly three years to cross the Arctic Ocean; for MOSAiC the journey has taken less than a year.
Since 1 January, RV Polarstern has drifted much faster than the ice drifted in the previous ten years. In the same four-month period (Jan-April) in 1896, Nansen’s Fram drifted only about half the distance. “This is likely the result of weaker ice pack. The ice in the Arctic Ocean has become significantly thinner, but also much younger, than only a few decades ago. This means that it can be more easily moved around by winds and ocean currents,” says Thomas Lavergne from the NMI, explaining the analysis.
The animation shows the trajectory of the MOSAiC drift campaign (red) from its beginning in October 2019 and 10 simulated trajectories (other colours) from recent years (see Figure 1). The drift of Nansen’s Fram from January to April 1896 is also shown. The simulated trajectories begin at the position of MOSAiC on 1 January 2020 and continue until 1 May. They are based on the EUMETSAT OSI SAF sea-ice drift product (OSI-405).
Figure 2 and 3 show the daily averaged speed and cumulative distance for the simulated MOSAiC trajectories. We can see that the 2020 drift trajectory was often faster than the trajectories for the other years, especially from mid-March to early April. In this period, the average drift speed exceeded 15 cm/s (~0.5 km/h) on several occasions, which was not common in earlier years.
Technical information on the analysis:
The simulated trajectories are prepared from the archive of operational sea-ice drift products at EUMETSAT OSI SAF (Ocean and Sea Ice Satellite Application Facility). They are constructed using forward Lagrangian sea-ice tracking. In practice, the trajectories begin at the position of the MOSAiC site on 1 January 2020, and are calculated one step at a time by combining the drift vectors from the OSI SAF products until the last days of April.
In Figure 4 below, we show the simulated trajectory for year 2020 (blue) and the actual drift of the MOSAiC floe (red). The simulated trajectory begins on 1 January. There is very good agreement between the actual and simulated trajectories, which attests to the accuracy of the results presented above. The OSI SAF sea-ice drift product is regularly validated against in-situ buoy data (including buoy data provided at the meereisportal.de data portal).
The OSI SAF sea-ice drift vectors are processed every day on the basis of satellite imagery and using a custom motion-tracking algorithm described in Lavergne et al. (2010). Satellite images from JAXA’s Advanced Microwave Scanning Radiometer 2 (AMSR2), the US Special Sensor Microwave Imager Sensor (SSMIS) and the European Advanced SCATterometer (ASCAT) are currently processed. The OSI SAF product files (and associated user documentation and validation reports) can be accessed here. You can also browse new sea-ice drift vector maps here every day.
The OSI SAF sea-ice processing is jointly run by the Norwegian Meteorological Institute and Danish Meteorological Institute.
Lavergne, T., S. Eastwood, Z. Teffah, H. Schyberg, and L.-A. Breivik (2010), Sea ice motion from low-resolution satellite sensors: An alternative method and its validation in the Arctic. J. Geophys. Res., 115, C10032, doi:10.1029/2009JC005958.
Contact for the analysis above:
Dr Thomas Lavergne (Norwegian Meteorological Institute (firstname.lastname@example.org)
Dr Mari Anne Killie (Norwegian Meteorological Institute) (email@example.com)
Dr Mats Granskog (Norwegian Polar Institute) (firstname.lastname@example.org)
Drift expertise at the AWI:
Dr Helge Gössling (AWI)
Dr Thomas Krumpen (AWI)