The mystery of the expansion of sea ice around Antarctica, at the same time as global warming is melting swaths of Arctic sea ice, has been solved using data from US military satellites.
Two decades of measurements show that changing wind patterns around Antarctica have caused a small increase in sea ice, the result of cold winds off the continent blowing ice away from the coastline.
"Until now these changes in ice drift were only speculated upon using computer models," said Paul Holland at the British Antarctic Survey. "Our study of direct satellite observations shows the complexity of climate change.
"The Arctic is losing sea ice five times faster than the Antarctic is gaining it, so, on average, the Earth is losing sea ice very quickly. There is no inconsistency between our results and global warming."
The extent of sea ice is of global importance because the bright ice reflects sunlight far more than the ocean that melting uncovers, meaning temperature rises still further.