Recent wave climate and expected future changes in the seasonally ice-infested waters of the Gulf of St. Lawrence, Canada

A new method is developed to evaluate the wave climate in the Gulf of St. Lawrence (GSL) with the consideration of wave attenuation by sea ice. Ice concentrations outputs from a regional oceanic model are used to attenuate, in post-processing, significant wave height (H-s) time-series simulated with a parametric wave model for ice-free conditions. Reanalysis data is used to compute GSL wave climate for the 1981-2010 period with and without wave attenuation by sea ice. Outputs from two simulations from the Canadian Regional Climate Model are also used to evaluate how GSL wave climate should evolve during the twenty first century according to the SRES-A2 greenhouse gases emission scenario. Results show that sea ice has reduced extreme H-s on the GSL by about 12 % on average over the 1981-2010 period but its impact on wave climate should become negligible by 2100 except in the St. Lawrence Estuary. Over the twenty first century, an increase of extreme H-s on the GSL should be expected mostly because of the reduction of sea ice. On the other hand, little changes in the extreme wave climate should be expected as a response to changes in the wind regime over the GSL. For future coastal engineering applications, the GSL wave climate could be evaluated by supposing an ice-free sea to integrate the likely impact of future climate change.