Experienced rowers Roz Savage, 44, and Andrew Morris, 48, had joined forces to cross the Atlantic Ocean in a bid to raise environmental awareness.
But local experts say the waters off Newfoundland and Labrador are brimming with fragmented shards of ice from icebergs, greatly increasing the risk of damaging their boat.
Experts say a large chunk of ice that broke away from a glacier in Greenland two years ago is bringing the ice to the region in droves.
Morris said cancelling the voyage was a difficult choice, but safety is paramount.
"We want to do something inspiring... but it was bordering on irresponsible," said Morris, adding the expedition took more than 18 months to plan.
Rowers face backwards, making it very difficult to see oncoming ice, he said.
"We row pretty much blind. So, you can image how risky it is," said Morris from St. John's, where the team had been preparing to depart in their seven-metre boat named Bojangles.
Savage said in a statement that given the circumstances, it would have been "foolish" to proceed with the expedition.
"I weighed up the pros and cons of going. ...But when one of the cons is ‘risk of death significantly greater than anticipated’, you have to take that one pretty seriously," said Savage.
"You can't fight Mother Nature, especially on the ocean. This year, the odds were stacked against us, and I suspect I know who would have won."
Savage added that one expert suggested the team had a 100 per cent chance of hitting a chunk of ice.
Morris said he hopes the cancellation of their voyage still draws attention to global warming and the melting of the polar ice caps.
He said the team plans to monitor ice conditions in the hopes of making the expedition next year.
It would have taken Savage and Morris at least two months to make the 3,200-kilometre journey to England.
The pair would have been the first male-female team to cross the North Atlantic.
Savage, a former management consultant turned environmental campaigner, and Morris, an entrepreneur, have both crossed oceans before.
Savage is one of the most experienced ocean rowers in the world, with 24,150 kilometres logged at sea over 520 days, while Morris has made three solo ocean rows.
Morris said the boat will be shipped back to England so the team can row from Bristol to London in time for the 2012 Olympic Games. The two-week, 200-kilometre row would have been the last leg of their Atlantic voyage.
Five people have been lost at sea since 1966 trying to row the same icy and stormy route, according to the Ocean Rowing Society International.