Online Marine & coastal projections 6 Changes in hydrography & circulation
This chapter describes model projections of changes to water temperature, salinity, the stability of the water column and currents around the UK. The results are obtained by using one member of the Met Office Hadley Centre regional model ensemble (known as the PPE) to provide the meteorological forcing for the Proudman Oceanographic Laboratory Coastal Ocean Modelling System. Results are presented for the time periods 1961–1990 and 2070–2098. Future projections are for the Medium emissions scenario.
As the techniques employed here are new, no attempt has yet been made to incorporate uncertainty into the future projections. Instead the single scenario provides a physically plausible illustration of one future that might be realised under the medium emissions scenario. Additional work is needed before we can estimate the range of uncertainty in future changes.
- The seas around the UK are projected to be 1.5–4 ºC warmer, depending on location, and ~0.2 p.s.u. fresher by the end of the 21st century. The change in salinity is particularly dependent on the projected change in the storm tracks owing to the latter’s effect on precipitation.
- Seasonal stratification strength is projected to increase but not by as much as in the open ocean.
- This stratification is projected to start ~5 days earlier and breakdown ~5–10 days later each year, hence extending the stratified period.
- Changes in the open ocean (especially the circulation) are particularly uncertain due to the proximity of the model boundary.