Regional modelling of the 21st century climate changes in the Irish Sea

An assessment of the complex evolution of climate change signals in the Irish Sea over the 21st century is presented in this paper. Potential impacts of climate change on the local hydrography are explored and interrelationships between fundamental oceanographic shelf sea phenomena investigated. A regional ECOMSED ocean model is used to downscale a 120-year period (1980–2099) of the SRES A1B scenario experiment from a global ocean model. A detailed regional analysis shows that local climate changes may be significantly different from the expected global changes.This research suggests that in the future the Irish Sea will be warmer with sea surface temperature increase of around 1.9 °C. Maxima and minima annual temperatures will occur around 2 weeks later each year relative to the present climate. Geographically, shallow waters along the coastline and in the eastern Irish Sea will exhibit strongest warming due to increased heat uptake during summer and autumn and reduced heat loss in spring and winter. Warming in the deep channel in the western Irish Sea will be generally weaker with seasonal variability subdued due to a large heat storage capacity. The warming will be largely stored in the surface layer of the water column leading to strengthening of stratification and a considerable decrease in the thickness of the mixed layer. The western Irish Sea gyre will become stronger and result in substantial reinforcement (>30%) of southward currents along the east coast of Ireland. Net northward flow in future predicted climate conditions will be maintained at the current annual rate. Steric sea level is projected to rise by 0.31 m during the 21st century, leading to an overall projected sea level rise of approximately of 0.47 m.Future changes to oceanographic parameters, flushing times and hydrodynamics of the Irish Sea are likely to alter the habitat and distribution of marine species; the finding of this research are therefore of great interest to ecologists and the fishery industry.

► Future climate of the Irish Sea will be warmer with projected SST trend of 1.9 °C.
► Stratification will strengthen and thickness of the mixed layer decrease.
► Stronger WISG will result in reinforcement of summer southward current.
► Future annual net northward flow will be at rate equal to that of current climate.
► Steric sea level is projected to rise by 0.31 m during the 21st century.