Estimating Sea-Level Allowances for Atlantic Canada using the Fifth Assessment Report of the IPCC

Abstract

Sea-level allowances at 22 tide-gauge sites along the east coast of Canada are determined based on projections of regional sea-level rise for the Representative Concentration Pathway 8.5 (RCP8.5) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) and on the statistics of historical tides and storm surges (storm tides). The allowances, which may be used for coastal infrastructure planning, increase with time during the twenty-first century through a combination of mean sea-level rise and the increased uncertainty of future projections with time. The allowances show significant spatial variation, mainly a consequence of strong regionally varying relative sea-level change as a result of glacial isostatic adjustment (GIA). A methodology is described for replacement of the GIA component of the AR5 projection with global positioning system (GPS) measurements of vertical crustal motion; this significantly decreases allowances in regions where the uncertainty of the GIA models is large. For RCP8.5 with GPS data incorporated and for the 1995-2100 period, the sea-level allowances range from about 0.5 m along the north shore of the Gulf of St. Lawrence to more than 1 m along the coast of Nova Scotia and southern Newfoundland.RÉSUMÉ [Traduit par la rédaction] Nous déterminons la tolérance à l'élévation du niveau de la mer à 22 stations marégraphiques le long de la côte est du Canada, à l'aide de statistiques de marées et d'ondes de tempête (marées de tempête), ainsi que de projections de hausses régionales du niveau marin, tirées du Cinquième rapport du Groupe d'experts intergouvernemental sur l'évolution du climat (GIEC) et suivant le profil représentatif d'évolution des concentrations 8.5 (RCP 8.5). Les marges de tolérance, qui peuvent servir à la planification d'infrastructures côtières, augmentent avec le temps au cours du 21e siècle, en raison de la combinaison de l'élévation du niveau moyen de la mer et de l'augmentation, avec le temps, de l'incertitude sur les valeurs projetées. Les marges de tolérance présentent une variation spatiale considérable, principalement due aux fortes variations régionales des changements relatifs des niveaux marins résultant de l'ajustement isostatique glaciaire. Nous décrivons une méthode permettant de remplacer cette composante de la projection, utilisée pour le Cinquième rapport, par des mesures de mouvement terrestre vertical prises par le système de localisation GPS. Cette méthode diminue de façon significative les marges de tolérance dans les régions où l'incertitude sur l'ajustement isostatique glaciaire est importante. Selon le RCP 8.5 incluant les données de GPS, pour la période de 1995 à 2100, la tolérance à l'élévation du niveau marin va d'environ 0,5 m le long de la rive nord du golfe du Saint-Laurent à plus de 1 m le long des côtes de la Nouvelle-Écosse et de la côte sud de Terre-Neuve.

Projected 21st Century Sea-Level Changes, Observed Sea Level Extremes, and Sea Level Allowances for Norway

“…Allowances are calculated in two alternative ways using a normal distribution: (1) assuming that the model spread does in fact correspond to the 5% and 95% probability bounds (e.g., [62,63]) and (2) assuming that the model spread being defined as the likely range in IPCC AR5 (p > 66%) corresponds to the 17% and 83% probability bounds. Note that the latter is one interpretation of the likely range.…”

Projected changes to air temperature, sea-level rise, and storms for the Gulf of Maine region in 2050

“…Table 3 summarizes projected mean relative sea-level change by 2050 (relative to 1995) for a selection of tide gauge station locations within the GOM region. These values are based on projections of sea-level change from the IPCC's Fifth Assessment Report (IPCC, 2014) for the medium and high emissions scenarios, with the addition of contributions from vertical land motion, variation in meltwater distribution, and dynamic oceanographic factors (James et al, 2014;Zhai et al, 2014Zhai et al, , 2015.…”

“…Their work suggests that along the New Hampshire coast for the medium emission scenario, there is a 1-in-100 chance that relative sea-level rise will exceed 61 cm (2.0 ft) by 2050, and a 1-in-1000 chance that relative sea-level rise will exceed 88 cm (2.9 ft) by 2050. For a selection of tide gauge station locations within the GOM region (James et al, 2014;Zhai et al, 2014Zhai et al, , 2015.…”

One Dimensional, Two Dimensional and Three Dimensional Hydrodynamic Modeling of a Dyked Coastal River in the Bay of Fundy

“…The upper 95% confidence limit storm surge residual values for Burntcoat Head were therefore used for this study and were added to the peak of the HHWLT tide time series used for the downstream boundary in the PCSWMM model. Sea level rise for the Bay of Fundy was estimated using values published by DFO (Zhai et al 2014), which are based on predictions from the IPCC Fifth Assessment Report (IPCC 2013) and local crustal subsidence estimations from James et al (2014). According to DFO (Zhai et al 2014), sea level rise was projected to increase by 1.11 m (95th percentile) from 2000 to 2100 for the high emissions scenario RCP 8.5.…”

“…Sea level rise for the Bay of Fundy was estimated using values published by DFO (Zhai et al 2014), which are based on predictions from the IPCC Fifth Assessment Report (IPCC 2013) and local crustal subsidence estimations from James et al (2014). According to DFO (Zhai et al 2014), sea level rise was projected to increase by 1.11 m (95th percentile) from 2000 to 2100 for the high emissions scenario RCP 8.5. This increase in sea level at Saint John was therefore assumed to be the same as at Truro, and was added to the HHWLT and storm surge time series to produce tide boundary conditions for the PCSWMM model under climate change conditions.…”