Using an underwater robot, scientists have pieced together the most detailed 3D map of Antarctic sea ice so far, which revealed it to be considerably thicker and more deformed in some areas than previous estimates had indicated. Because this technology is allowing researchers to probe areas that were previously inaccessible, the team hopes that these new measurements will help further our understanding of the complex interplay between climate change and sea ice dynamics.
As global temperatures continue to steadily rise, you might expect the halo of ice encircling the frozen continent of Antarctica to recede. But unlike the Arctic, which is progressively losing ice as predicted by climate models, the Antarctic has gained ice in recent years, contrary to models. This, alongside the erratic patterns of ice in different regions of the continent, has been difficult for scientists to explain.
In order for scientists to understand how it is changing in the face of a warming planet, they need to not only gauge the spatial extent of the ice, but its thickness too. To do this, scientists have generally relied on two techniques: satellite observations and drilling. Unfortunately, both methodologies have their limitations. Deep snow can obscure the ice, making satellite images difficult to interpret, and drilling comes with a risk of sampling bias toward thinner ice as research vessels tend to steer clear of areas with the thickest packs to avoid getting stuck.
To overcome this, scientists from the UK, USA and Australia decided to approach the ice from a different angle—from underneath. This was made possible by the Woods Hole Oceanographic Institution’s (WHOI) new robot, or Autonomous Underwater Vehicle (AUV), known as SeaBED, which was fitted with the upward-facing sonar designed to measure and map the underside of the ice floats. The robot cruised at a depth of between 20 to 30 meters in three near-coastal regions, covering an area of 500,000 square meters. This kind of operation is not without risks, as robots have been lost beneath the ice before. However, the project was worth the effort as they managed to gather a considerable amount of interesting data.
As described in Nature Geoscience, the mean draught (the depth between the waterline and the bottom of the ice) was found to be over three meters, which is more than two meters thicker than previous observations had suggested. Furthermore, they also recorded a maximum depth of 16 meters, while previous work indicated maximum depths of 10 meters. They also found that the ice was more deformed than previously believed, which results from ice floats smashing into each other and piling into thicker sections.
Overall, the researchers conclude, this work suggests that the Antarctic sea ice may be thicker than previously believed. However, they warn that we should not be making generalizations from small sample sizes. 500,000 square meters may be a large area, but it’s dwarfed by the overall size of the Antarctic sea ice, which can cover over 20 million square kilometers at its peak. However, the WHOI is already developing a new vehicle, and plans to deploy a torpedo-like robot that can cover larger areas in the near future.
[Via Nature Geoscience, Nature, Science, BBC News, British Antarctic Survey and New Scientist]