LONDON — Arctic ice cover has melted so much that a ship could have sailed unhindered from northern Europe to the North Pole itself a few weeks ago, according to images released this week by scientists.

Satellite images acquired between August 23 and 25 have shown for the first time dramatic openings — larger than the size of the British Isles — in the Arctic’s year-round sea ice pack, north of Svalbard and extending into the Russian Arctic all the way to the North Pole.

The images were acquired by instruments aboard Envisat and EOS Aqua, two satellites operated by the European Space Agency.

“This situation is unlike anything observed in previous record low-ice seasons,” Mark Drinkwater of ESA’s Oceans/Ice Unit said. “It is highly imaginable that a ship could have passed from Spitzbergen or northern Siberia through what is normally pack ice to reach the North Pole without difficulty.”

Mr. Drinkwater added: “If this anomaly continues, the Northeast Passage, or ‘Northern Sea Route’ between Europe and Asia will be open over longer intervals, and it is conceivable we might see attempts at sailing around the world directly across the summer Arctic Ocean within 10 to 20 years.”

Regular satellite monitoring over the past 25 years shows that the northern polar ice cover has shrunk and thinned as global temperatures have risen. But this year’s images are unprecedented, and fierce storms that fragmented and scattered already thin pack ice may be to blame, the scientists believe.

The data were gathered by Envisat’s Advanced Synthetic Aperture Radar instrument and the AMSR-E instrument aboard the EOS Aqua satellite and showed between 5% and 10% of the Arctic’s perennial sea ice, which had survived the summer melt season, has been fragmented by late summer storms.

Satellites have witnessed reductions in the minimum ice extent — the lowest amount of ice recorded in the area annually — at the end of summer to less than 2.1 million square miles in 2005 from around 3 million square miles in the early 1980s, changes widely viewed as a consequence of greenhouse warming.

Data gathered by NASA satellites and published in Nature this week show that Greenland continued to lose ice mass at a significant rate during April, and the rate is accelerating.

The University of Colorado study indicates that between April 2004 and April 2006, Greenland was shedding ice at about 2 1/2 times the rate of the previous two years.

Scientists believe that large amounts of fresh water purged from Greenland’s eastern coast could help to weaken the counter clockwise flow of the North Atlantic Current, lowering water and wind temperatures and potentially triggering abrupt cooling events in northern Europe.