Scenarios of Twenty-First Century Mean Sea Level Rise at Tide-Gauge Stations Across Canada

Abstract

ABSTRACT Existing scientific literature and international assessments, such as those by the Intergovernmental Panel on Climate Change, provide a wide range of projections for global mean sea level rise (SLR) in the twenty-first century. At the local scale, the ranges or uncertainties of projections are even larger. There is a pressing need to compile plausible local SLR scenarios to aid coastal communities with adaptation. Here we develop three local SLR scenarios for Canadian tide-gauge stations for the twenty-first century (Low, Intermediate, and High). Our Low Scenario is based on projections under the Representative Concentration Pathway 4.5 (RCP4.5) scaled down to the present global SLR rate. Our Intermediate Scenario is based on projections under the Representative Concentration Pathway 8.5 (RCP8.5), and our High Scenario is based on the RCP8.5 projections with an adjusted contribution from the Antarctic ice sheet. For all three scenarios, we use vertical land motion (VLM) from global positioning systems (GPS) data corrected for the present-day melt of glaciers and ice sheets instead of the commonly used VLM from a glacial isostatic adjustment (GIA) model. The GPS data include not only GIA but also other processes affecting VLM. For each scenario, larger SLR is projected along the southeastern Atlantic coast, the Pacific coast, and the Beaufort Sea coast than along other Canadian coasts in the twenty-first century. Under the Low, Intermediate, and High Scenarios, the median relative sea level along the southeastern Atlantic coast may rise by as much as 0.39, 0.82, and 0.96 m, respectively, over 2010–2100. The proposed scenarios allow coastal engineers and managers to consider multiple future conditions and develop multiple response options, as well as choose the most suitable option according to the risk tolerance of infrastructure.