Before you read on, a few things to note. No, this research is not “proof” that global warming isn’t happening. It’s not proof that humans aren’t damaging the environment by pumping out greenhouse gases. And it certainly isn’t proof that things aren’t as bad as we thought they would be.
No, what this latest research published in Nature Geoscience shows is that Arctic sea ice is far more susceptible to changes in seasonal temperature than we thought – and the overall trend is still that sea ice is decreasing, possibly already to the point of no return.
The study by University College London (UCL) and the University of Leeds used data from the European Space Agency’s (ESA) CryoSat-2 satellite to study Arctic sea ice thickness. They found that an unusually cooler summer in 2013 allowed it to increase by a remarkable 41% on the same period the year before. During 2010 to 2012, there was a 14% reduction in the volume of summertime Arctic sea ice.
“This work was the first to look at sea ice thickness across the whole Northern Hemisphere,” lead author on the study and Ph.D. student Rachel Tilling from UCL told IFLScience. The resilience was not an expected result, and the cause of the cooler summer in 2013 is not entirely understood. However, Tilling noted that this increase only “wound the clock back” a few years, and the “long term trend in Arctic sea ice volume is downwards.”
Temperature trends in the Arctic in the last 30 to 40 years continue to go up, and the sea ice volume continues to go down. “So those two do appear to be correlated, which is something we’ve found in this paper,” said Tilling.
CryoSat-2, artist's impression shown, will remain in operation until 2017. ESA/P. Carril.
While previous research has shown that Arctic sea ice extent has declined by about 40% since the 1970s, it has been more difficult to measure volume, something done by this study. But while the ice volume increased in 2013, the results highlight how easily it can be changed.
As summers get warmer in the future, it is likely to lead to more and more sea ice melt. This study also indicates that sea ice is more affected by summer warming than winter cooling.
“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,” co-author Professor Andy Shepherd of UCL and the University of Leeds said in a statement.
“Although the jump in volume means that the region is unlikely to be ice free this summer, we still expect temperatures to rise in the future, and so the events of 2013 will have simply wound the clock back a few years on the long-term pattern of decline."
The CryoSat-2 mission is due to end in 2017, and there is currently no replacement planned. This means that it will be difficult to work out if this increase was an unusual occurrence, or something that occurs regularly. "Our goal is to make sure we do not lose this unique capability to monitor Arctic sea ice when the [CryoSat-2] mission ends,” added Shepherd.
Data from the satellite's mission will still be useful in predicting future climate change. But scientists will be keen to work out just how resilient sea ice can be to warming global temperatures.