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.

PI: Prof. Sheldon Bacon 
Email: s.bacon at noc.ac.uk

Dates
–
Aim

Aims

  1. To improve understanding of contemporary Arctic ocean and sea ice variability & trends
  2. To reduce uncertainty of future (seasonal–decadal) predictions of Arctic climate

Objectives

  1. Identification and quantification of critical present-day Arctic ocean and sea ice processes, specifically issues related to momentum transfer, dense water formation, mixing, and heat and freshwater fluxes
  2. Diagnosis of present and prognosis of future Arctic ocean and sea ice circulation, fluxes, and dynamics, using a hierarchy of inverse, idealized, GCM and coupled climate models, tested with new observations
  3. Evaluation of future Arctic regional climate and wider consequences of change, using a coupled IPCC-class climate model, taking into account the improved knowledge and understanding of the consequences of sea ice reduction on Arctic ocean circulation and fluxes.

Methodology & approach

To achieve the project objectives, we propose a linked suite of studies employing new and existing measurements, process models and coupled climate models. To evaluate, improve and validate the representations of key processes in models related to momentum, energy and freshwater exchanges (Objective 1) requires a combination of new observations with the development of new inverse models and parameterisations. Our programme will employ new (and historical) satellite and in-situ observations to provide the quantitative constraints necessary to produce new and accurate parameterisations of surface momentum flux and turbulence.

To estimate seasonally-resolved boundary fluxes requires the integration of in-situ and remote-sensed measurements using an inverse model. The Arctic ocean and sea ice system is complex, and the result of interaction between mechanical and buoyancy fluxes, local and remote forcing, and topography.

To isolate the roles of individual processes in controlling Arctic ocean heat and freshwater fluxes, both in present and future (ice-free) conditions (Objective 2), we will conduct a series of idealized model experiments, incorporating new parameterisations.

To improve predictions of future climate using a coupled climate first requires evaluation of the climate model under present-day conditions. We will test an IPCC-class climate model (Objective 2) against both the new observations and the results of the idealized model experiments to determine the model’s skill in reproducing present-day Arctic ocean-ice system. We will then conduct a series of experiments to determine the future impact of the sea ice retreat and increases in momentum and freshwater fluxes on Arctic and regional climate (Objective 3).