The European Space Agency’s CryoSat mission has returned its latest map of Arctic sea ice volumes, recording a slight decrease in thickness over previous measurements. The data flies in the face of the previous downward trend, which was much greater, but is unlikely to indicate a shift in the accepted pattern of degradation.
Long-term satellite records show that Arctic ice volume fluctuates from season to season, but details a consistent downward trend throughout the year. The new CryoSat measurements, which were recorded in October and November 2014, show a 6.4 percent decrease in the volume of arctic sea ice, with 10,200 cubic km (6,338 cubic miles) now remaining.
However, despite the drop, the figure is actually the second-highest recorded since the satellite started collecting data in 2010. The team is keen to point out that this likely doesn’t indicate a shift away from the long-term downward trend, recommending that the new data be viewed in the context of more established climate records.
CryoSat orbits at 700 km (435 miles), and was launched in 2010 with a planned 3-year life span. However, the mission has been extended far beyond its original timeframe, and is still going strong today. The project is designed to monitor polar sea ice across the entire Arctic ocean, observing changes in thickness, with the goal of contributing to our understanding of the long-term downward trend in volume.
To do so, it carries a radar altimeter designed specifically for the detection of ice. Known as the Synthetic Aperture Interferometric Radar Altimeter (SIRAL), the instrument is able to observe tiny variations in the heights of ice and sea level.
"For reliable predictions, we should try other approaches, like considering what is forcing the changes, incorporating the CryoSat data into predictive models based on solid physics, or simple waiting until more measurements have been collected," said Professor Andrew Shepherd of University College London.
With the project now officially extended to 2017, the team has begun looking into other uses for the satellite. For example, there are plans to use data collected over the last month to help vessels navigate the tricky waters north of Alaska and eastern Russia.