Global warming is changing the distribution, abundance and diversity of marine life in the polar seas with “profound” implications for creatures further up the food chain, according to scientists involved in the most comprehensive study of life in the oceans ever conducted.

Researchers from the Arctic Ocean Diversity (Arcod) project have documented rising numbers of warm-water crustaceans in the seas around Norway’s Svalbard Islands. Arcod is part of the Census of Marine Life, a huge 10-year project involving researchers in more than 80 nations that aims to chart the diversity, distribution and abundance of life in the oceans.

They say an increasing number of these species are extending their range towards the poles as previously cold waters between Norway and the North Pole become warmer and more hospitable.

The team, led by Dr Rolf Gradinger, from the University of Alaska, also collected evidence from the polar Chukchi Sea, between Russia and Alaska, which showed that at least three species have extended their range northwards by up to 500km. The most notable is the snow crab, which has crossed the Bering Strait and is occurring in the Chukchi Sea for the first time.

“This is an example of a general trend we are observing where water is warming further north and making this region more suitable for southerly species,” Gradinger said.

The team also found that smaller species are replacing larger ones in some Arctic waters, a shift which could have profound implications further up the food chain.

Gradinger added: “It’s extremely difficult to get information from polar seas because we don’t have good historical data. But we must collect data now to evaluate the impact of climate change and the use of the seas for tourism, fishing and shipping. With the warming of Arctic commercial exploitation might increase and therefore it’s important to document what species are occurring currently.”

Scientists say the discovery opens a host of future research questions over where they originated and how they ended up at opposite ends of the earth.