A new study has found that the water flowing into the Arctic from the North Atlantic is at its warmest level for more than 2,000 years.
This could endanger polar bears, which need the ice in order to survive.
Scientists at the University of Colorado in Boulder examined tiny plankton-like organisms on the seabed of the Fram strait, which is the main carrier of ocean heat to the Arctic.
They found that back then the temperature in the Arctic water was on average 3.4C (38F), but that has now gone up to 5.2C (41F).
Higher temperatures 'are presumably linked to the Arctic amplification of global warming', the study concluded, adding that global warming 'is most likely another key element in the transition to a future ice-free Arctic Ocean'.
Thomas Marchitto said that cold seawater “is critical for the formation of sea ice, which helps to cool the planet by reflecting sunlight back to space.
"Sea ice also allows Arctic air temperatures to be very cold by forming an insulating blanket over the ocean. Warmer waters could lead to major sea ice loss and drastic changes for the Arctic," reports the Daily Mail.
"On a scale of 2,000 years, it stands out dramatically as something that does not look natural," he added.
