Atmospheric contribution to Mediterranean and nearby Atlantic sea level variability under different climate change scenarios

The contribution of atmospheric pressure and wind to the XXI century sea level variability in Southern Europe is explored under different climate change scenarios. The barotropic version of the HAMSOM model is forced with the output of the atmospheric ARPEGE model run under scenarios B1, A1B and A2. Additionally, a control simulation forced by observed SST, GHGs and aerosols concentrations for the period 1950–2000 and a hindcast forced by a dynamical downscalling of ERA40 for the period 1958–2001 are also run using the same models. The hindcast results have been validated against tide gauge observations showing good agreement with correlations around 0.8 and root mean square error of 3.2 cm. A careful comparison between the control simulation and the hindcast shows a reasonably good agreement between both runs in statistical terms, which points towards the reliability of the modelling system when it is forced only by GHG and aerosols concentrations. The results for the XXI century indicate a sea level decrease that would be especially strong in winter, with trends of up to − 0.8 ± 0.1 mm/year in the central Mediterranean under the A2 scenario. Trends in summer are small but positive (~ 0.05 ± 0.04 mm/yr), then leading to an increase in the amplitude of the seasonal cycle. The interannual variability also shows some changes, the most important being a widespread standard deviation increase of up to 40%. An increase in the frequency of positive phases of the NAO explains part of the winter negative trends. Also, an increase in the NAO variability would be responsible for the projected increase of the interannual variability of the atmospheric component of sea level. Conversely, the intra-annual variability (1–12 months excluding the seasonal cycle) does not show significant changes.

► Future projections of atmospherically-induced sea level have been generated.
► The modelling system has been thoroughly validated.
► Results indicate a sea level decrease especially strong in winter for the XXI century.
► The interannual variability shows a widespread increase.
► Changes in NAO partially explain the projected changes.