Multi-decadal simulations

Oceans 2025 Theme 9, work package 9.4

Many shelf sea processes act on multi-year time scales, so investigations of variability arising from atmospheric, oceanic and terrestrial forcing, including distinguishing between climatic and anthropogenic effects, require substantially longer integrations than have generally been carried out. Processes of particular interest are cross shelf (advective and diffusive) transport of water, carbon, nutrients and pollutants, and biogeochemical cycling. It is now appropriate to extend the multi-decadal simulations with POLCOMS (eg. Young & Holt, 2007) in two ways: from physics-only to fully multi-disciplinary, and from hindcast to prediction. WP 9.4 will provide two key error-quantified data sets, for use in Themes 3 and 6, and that will also be made available for the wider community.

• 1950 to 2050 simulations of the NE Atlantic with the full POLCOMS-ERSEM-WAM-`GOTM model. The physics component of these simulations will be repeated with the NEMO model to provide a direct comparison (with Themes 3 and 6).
• 1960 to 2000 simulations of the global coastal-ocean focusing on the carbon cycle. The GCOM e-science project (2006-09) aims to develop the techniques for running multiple large scale shelf sea domains coupled to global ocean climate simulations. It uses POLCOMS and a reduced complexity (layer integrated) version of ERSEM.

In both cases the focus will be on large time/space scale model verification, an aspect largely missing from GCOM (sensitivity experiments, analysis and interpretation of the model data sets will primarily be carried out in Themes 3 and 6). We shall utilize the techniques of data mining developed by the e-science community to develop automated model verification procedures, for example by developing a direct interface to data centres and/or the NERC data grid. Our work will focus on verifying the physics models, while we shall collaborate directly with PML on the verification of the biogeochemical model.

References

Young, E. F. and Holt, J. T. 2007. Prediction and analysis of long-term variability of temperature and salinity in the Irish Sea. Journal Of Geophysical Research, 112, C01008, doi:10.1029/2005JC003386, 2007.

Figure 1: Linear trend 1955-2004 in April-June sea surface temperature. Units degrees/decade.