Interannual Prediction of the Arctic Sea-ice cover and its Impact on the European Climate (PICA-ICE),

Budget: 128000

The rapid decline of the Arctic sea ice extent and thickness along the recent decades have drawn an increasing attention toward the North pole region, raising the challenge of predicting the first ice-free summer. The potential socioeconomical consequences of the Arctic sea ice shrinking, locally as far as the exploitation of ressources is concerned, but also over the entire Northern Hemisphere, have made of the Arctic basin a key region of interest. The dominant signal of variability in the Arctic region has been shown to have a decadal timescale. Various feedback mechanisms have been suggested to explain such a peak in the sea ice spectrum either via a direct retroaction of the sea ice cover anomalies onto the atmosphere or via the Atlantic ocean meridional overturning circulation or the subpolar gyre heat transport.

One of our objectives will be to investigate the mechanisms driving the sea ice cover variability and its impact on the Northern Hemisphere climate by applying an original statistical method to the available observational datasets. The reduced observational sampling of the Arctic sea ice cover stands as an obstacle which will be overcomed by the production and validation of sea ice reanalyses of the 1958-2010 period that will constitute a physical extrapolation for the sparse available observations.

Those sea ice reanalyses will also provide optimal estimates of the observed sea ice cover as initial conditions for interannual climate predictions that will be produced with EC-Earth. With these predictions, the mechanisms suggested to explain the sea ice cover changes and their impact on the Northern Hemisphere climate will be further validated, the ability of the EC-Earth climate model to predict the Arctic sea ice cover will be assessed and the added value of refining the sea ice cover prediction on the forecast quality of the Northern Hemisphere seasonal-to-interannual climate predictions will be estimated. Diagnoses of the potential discrepancies between the sea ice cover changes as simulated or as extracted from observational datasets is an essential step toward pointing out the regions with a crucial need for more observations and the parametrisations that might need further development.

With those analyses we aim at reducing the uncertainties both on the rate of long- term melting and on the superimposed internally-generated changes in sea ice cover. Finally, since one major public concern is the overall climate impact of an Arctic sea ice shrinking, one of our objectives will be, through extreme sensitivity experiments, to assess the timescale for a recovery of the Artic sea ice cover after an ice-free summer and to assess the sensitivity of the extratropical circulation and the Northern Hemisphere climate to such a massive sea-ice loss as an upper-bound to its sensitivity to interannual sea ice cover changes.

One of the primary benefits derived from the project is the public release of the sea ice reanalyses and the development of an operational system of sea ice analyses that will provide initial conditions for seasonal to decadal predictions to the international community, and in particular to the EC-Earth community. The project will notably increase the capability of Spanish research groups on dynamical ensemble climate forecasting and global modelling.

The main objectives of this project will be to :
  • - Investigate the mechanisms driving the interannual variability of the Artic sea ice cover, to assess the extent of their predictability and to attempt refining the predictions of the externally forced sea ice loss and internally-generated variability of the sea ice cover.
  • - Investigate the mechanisms by which the Artic sea ice cover influence the Northern hemisphere climate and to assess the added value of the sea ice initial condition information in interannual climate predictions of the European climate.

Starting date: 01/01/2013
Final date: 31/12/2015

Nationally funded project: Ministry of Economy and Competitivity