THE world’s most inaccessible stretch of ocean, deep beneath the Arctic ice cap, is teeming with far more life than scientists had thought possible.

Dozens of unidentified species, many of which are thought to be new to science, have been found by the most comprehensive survey yet undertaken of the “Hidden Ocean”, at the top of the world.

The month-long expedition by 24 scientists has revealed a surprising density and diversity of life deep in the Arctic Ocean, much of which is capped by ice up to 20 metres thick.

Particularly remarkable finds include suspected new species of jellyfish and benthic bristle worms, the first examples of squid and octopus recorded in such northerly waters, and two species of crustacean similar to sand fleas that have never been found in an icy environment.

The discoveries will contribute to the Census of Marine Life (CoML), an international project to map the biodiversity of the oceans, which are the world’s most underexplored environment. The £500 million, ten-year census has charted the distribution of 38,000 marine species, and is identifying two new fish species a week.

The Hidden Ocean expedition began in late June, at the height of the Arctic summer when thinner ice allows icebreakers better access. Scientists from the United States, Russia, Canada and China sailed aboard the US Coast Guard cutter Healy to the Canada Basin, a huge and largely unexplored stretch of water, capped with ice, to the north of the Yukon Territory and Alaska. The survey also included the Chukchi and Beaufort Seas, in the same region.

“The Canada Basin is one of the world’s most isolated ocean areas,” said Rolf Gradinger, of the University of Alaska at Fairbanks, the head of the Arctic division of the CoML and chief scientist on the voyage. “Several creatures brought aboard the Healy are unfamiliar to expedition experts and may well prove new to science.”

Bodil Bluhm, his colleague, said: “Overall, the densities of animals are much higher than expected. It now appears possible to confirm that the rich biodiversity surprising deep-sea explorers worldwide exists as well in deep Arctic waters.”

Scientists believe that reliable data on the nature and abundance of life in one of the world’s most extreme environments will be critical to assessing the impact of climate change and shrinking ice caps.

The Healy returned to port on Tuesday with thousands of specimens and photographs, collected at depths of up to 3,300m (10,800ft) at 14 locations. Researchers used remotely operated submarines and underwater cameras to conduct the survey, as well as more traditional methods such as Scuba divers, nets and ice cores.

Russ Hopcroft, another expedition scientist, said: “Modern technology has opened a window on this amazing world. The imagery of the mid-water and seafloor shows many life forms, such as soft bodied zooplankton, deep sea cucumbers and soft corals. The few explorers in this area before us had no adequate tools to collect or see these creatures. What continues to fascinate and motivate us all is the chance to record species never known before.”

One of the next phases of the CoML will be a voyage to map the species of the Southern Ocean during the Antarctic summer of 2007-08.

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