The Arctic Ocean is predicted to be seasonally ice-free by the end of the century, and it will change radically as a consequence. Changes in the Arctic have the potential to affect remote climates, including the UK, by changing the nature of the thermohaline circulation, offering the risk of regional cooling against a background of global warming.
As the Arctic warms and sea ice retreats, not only will new Arctic sea routes open at least seasonally to regular shipping, but offshore hydrocarbon reserves will become more accessible. Ecosystem changes in response to ocean warming will see new commercial fisheries opening as species migrate northwards. The economic consequences for the UK of Arctic change are substantial, and depend on whether we can expect either continued warming, or regional cooling, with differing impacts on energy supply, health, water, and food.
The key is to quantify (for the present) and understand (for the future) the Arctic ocean’s import of heat, export of freshwater, and storage of both. Direct exposure of the ocean surface to wind forcing will increase the efficiency of momentum transfer, so the ocean will spin up on seasonal, and possibly longer, timescales. The ocean’s turbulent mixing will strengthen, and dense water formation rates will change.
We do not know enough about the role of these processes in the present-day ocean and sea ice system to be able to predict with confidence what the future holds.