The impact of climate change on the wave climate in the Gulf of St. Lawrence

The purpose of this study is to investigate possible local changes in the wave climate for the coastal waters off eastern Canada, particularly in the Gulf of St. Lawrence (GSL) related to changes in marine winds, storm and the sea ice climate, due to climate change. These analyses are based on application of a dynamical downscaling approach whereby a regional climate model is driven by climate change estimates from the Canadian Global Climate Model (CGCM3) to provide relatively high resolution winds to drive a wave model. The CGCM3 simulation follows the A1B climate change scenario of the Special Report on Emission Scenarios from the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC AR4, 2007). The analyses of the wave climate are based on simulations of the waves from a third-generation wave model, WAVEWATCHIII™, and the downscaled winds obtained from the Canadian Regional (atmospheric) Climate Model (CRCM). We show that the significant wave heights in the Gulf of St. Lawrence (hereafter GSL) and neighboring coastal waters will slightly increase in the winter and decrease in the summer, in response to changes in storms and sea ice in the future climate (2040-2069) compared to the present wave climate, represented as 1970-1999. This time period is denoted as the “historical” wave climate in this study. In summer, the changes in significant wave heights (Hs) are associated with estimated decreases in the frequency of the occurrence of the cyclones. Projected changes in return values for summer extremes in the wave climate are consistent with the associated changes in the maximum Hs values. In winter, the projected increases in return values are mostly concentrated in the St. Lawrence Estuary, the northern and southwestern GSL, consistent with changes in the maximum waves in these regions. An important factor related to change in the winter wave climate is change in the sea ice.