In what looks to be another sign the Arctic is heating up quickly, British explorers in Canada's Far North reported on Tuesday that they had been hit by a three-minute rain shower over the weekend.
The rain fell on the team's ice base off Ellef Rignes island, about 3,900 km (2,420 miles) north of the Canadian capital Ottawa.
"It's definitely a shocker ... the general feeling within the polar community is that rainfall in the high Canadian Arctic in April is a freak event," said Pen Hadow, the team's expedition director.
"Scientists would tell us that we can expect increasingly to experience these sorts of outcomes as the climate warms," he told Reuters in a telephone interview from London.
The Arctic is heating up three times more quickly than the rest of the Earth. Scientists link the higher temperatures to the greenhouse gas emissions blamed for global warming.
Hadow said a Canadian scientific camp about 145 km west of the ice base had been hit by rain at the same time.
"It is obviously quite worrying when you are camped out on ice. I felt distinctly nervous for a while because the consequences of getting wet here can be serious," ice base manager Paul Ramsden said in a statement.
The base is supplying a three-member team out on the ice another 1,100 km further north. The trio is studying the impact of increased carbon dioxide absorption by the sea, which could make the water more acidic.
Experts say the thick multiyear ice covering the Arctic Ocean has effectively vanished, which could make it easier to open up polar shipping routes. U.S. data shows the 2009 ice cover was the third-lowest on record, after 2007 and 2008.
Hadow said the team carrying out the carbon dioxide experiments had noticed that ice was abnormally thin and was moving around more than they expected. The winds were stronger than usual.
Earlier this month an ice floe the team's tent was moored on suddenly broke apart, although no one was injured. The team is due to leave the ice in the first half of next month and should release preliminary results later this year.