Scientists from the Arctic Monitoring and Assessment Programme (AMAP) have monitored widespread changes in ocean chemistry in the region, the BBC reported.
They say even if CO2 emissions stopped now, it would take tens of thousands of years for Arctic Ocean chemistry to revert to pre-industrial levels.
Many creatures, including commercially valuable fish, could be affected.
They forecast major changes in the marine ecosystem, but say there is huge uncertainty over what those changes will be.
It is well known that CO2 warms the planet, but less well-known that it also makes the alkaline seas more acidic when it is absorbed from the air.
Absorption is particularly fast in cold water so the Arctic is especially susceptible, and the recent decreases in summer sea ice have exposed more sea surface to atmospheric CO2.
The Arctic’s vulnerability is exacerbated by increasing flows of freshwater from rivers and melting land ice, as freshwater is less effective at chemically neutralising the acidifying effects of CO2.
The researchers say the Nordic Seas are acidifying over a wide range of depths - most quickly in surface waters and more slowly in deep waters.
Scientists estimate that the average acidity of surface ocean waters worldwide is now about 30 per cent higher than before the Industrial Revolution.