Previous research has suggested that both the thickness and extent of Arctic summer sea ice have dramatically declined over the past 30 years. The data includes measurements taken by the National Snow and Ice Data Center in Boulder, Colorado.
But now, some British scientists have found the volume of Arctic sea ice has actually increased by a third after 2013’s unusually cool summer. That’s the conclusion of a new study conducted by researchers at University College London and the University of Leeds, and published in the journal Nature.
Rachel Tilling, the study’s lead author from the Center for Polar Observation and Modelling at the University College London, said that the much cooler temperatures in the summer of 2013 were more like those recorded back in the late 1990s.
“This allowed thick sea ice to persist northwest of Greenland because there were fewer days when it could melt,” she said in a press release. “Although models have suggested that the volume of Arctic sea ice is in long-term decline, we know now that it can recover by a significant amount if the melting season is cut short.”
In an email to Science World, Julienne Stroeve, a research scientist at the National Snow and Ice Data Center, said she is “very cautious about these results (of the UK study)” because much of the processing used in the study was not well-described, which makes it difficult for others to fully reproduce their results. However, Stroeve said she doesn’t doubt that the overall Arctic ice thickness was larger in 2013 and 2014 than in 2012, because not as much ice melted.
According to the Nature study, the sudden increase in sea ice volume after just one cool summer suggests that Arctic sea ice may be more resilient than has been previously considered.
Stroeve doesn’t quite agree. “I think the statement that sea ice is more resilient is a bit premature as it’s based on only 5 years of data, and it does not take into account variable precipitation as they assume climatological snow depth,” she said.
To make their findings, the British researchers used measurements taken by the European Space Agency’s CryoSat satellite between 2010 and 2014, as well as maps of sea ice extent.
CryoSat’s primary instrument, according to ESA’s website, is the Synthetic Aperture Interferometric Radar Altimeter. It was designed to meet the measurement requirements for ice-sheet elevation and the height of sea ice protruding from the water.
Stroeve says that one does not measure ice thickness directly with radar or a laser altimeter. “You need to also know snow depth and density, both of which are not known over the Arctic Ocean,” she says.
Professor Andrew Shepherd, Director of Center for Polar Observation and Modelling said that while it is doubtful the Arctic region will be ice-free this summer, due to the jump in sea ice volume, temperatures are expected to rise again in the future. He likens the effects of the cool summer of 2013 as simply “winding the clock back a few years” on long-term Arctic sea ice decline.
“Understanding what controls the amount of Arctic sea ice takes us one step closer to making reliable predictions of how long it will last, which is important because it is a key component of Earth’s climate system,” he says.
The researchers said that they are planning to use CryoSat’s measurements of changing sea ice thickness not only to help improve models that are used to forecast future climate change, but also to help sailors steer their ships in the potentially dangerous Arctic region.