Projections of Relative Sea-Level Change (developed by Natural Resources Canada)
To help Canadians plan, prepare for, and remain resilient to projected sea-level changes, Natural Resources Canada (NRCan) has developed a new dataset of present and future relative sea-levels (James et al., 2021). The dataset provides projections for relative sea-level change, which is the change in ocean height relative to land and is the apparent sea-level change experienced by coastal communities and ecosystems. It is a combined measure of both changes to ocean levels due to climate change and vertical land movements, as described below.
Projections are available at a resolution of 0.1° (approximately 11 km latitude, 2-8 km longitude), and for 2006 and every decade from 2010-2100, relative to 1986-2005 conditions. The data is available for the three Representative Concentration Pathways (RCP) emissions scenarios (RCP 2.6, RCP 4.5, RCP 8.5) and an enhanced scenario.
Use relative sea-level rise data together with other types of data
When combined with other types of data such as estimates of storm surge, waves, tides, and additional local-scale vertical land motion, such as subsidence on river deltas, this relative sea-level data is expected to contribute significantly to coastal flood risk assessments and adaptation decision-making.
Relative sea-level change varies greatly based on where you live in Canada
Relative sea-level change along Canada’s coastlines varies greatly from location to location, and can differ substantially from the projected global average sea-level change. Some Canadian coastlines in Atlantic Canada can expect relative sea-level rise that is larger than the projected global sea-level rise. Conversely, other Canadian coastlines, where the land is rising faster than the ocean, such as Hudson Bay and much of the Canadian Arctic Archipelago, can expect a relative sea-level fall.
Guidance on emissions scenarios
Data estimates are available for three RCP scenarios: RCP 2.6 (low), RCP 4.5 (medium), and RCP 8.5 (high) – as reported in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5; Church et al, 2013a,b). For each scenario, lower, median and upper estimates of projected relative sea-level change are provided, corresponding to the 5th, 50th and 95th percentiles of the full ensemble of Global Climate Models. An additional Enhanced Scenario is also available, described below. All projections are based on open ocean basin changes that are extrapolated to the coastline (which does not include explicit modelling of shallow water effects).
For long-term decisions that may be influenced by sea-level changes, the precautionary principle would indicate using the 95th percentile values of the high-emission (RCP 8.5) scenario. In the case of low tolerance to risk and for project time frames extending past 2100, it would be prudent to consider the enhanced scenario described below. The enhanced scenario adds a further 65 cm of global sea-level rise to the median projection of the highest (RCP8.5) climate scenario at 2100. This 65 cm reflects a potential additional contribution from the Antarctic Ice Sheet. In other situations, use of higher or lower sea-level values, or a range of projected sea-level change, may be more appropriate. For detailed technical guidance on the use of sea-level projections see Relative sea-level projections for Canada based on the IPCC Fifth Assessment Report and the NAD83v70VG national crustal velocity model (James et al, 2021) and GEOSCAN for the full publication and data.
More about this dataset
Projected sea-level changes in this dataset include the effects of changes in glacier and ice-sheet mass loss, thermal expansion of the oceans, changing ocean circulation conditions, and human-caused changes in land water storage, as summarized in IPCC AR5. A new land motion model developed by the Canadian Geodetic Survey (Robin et al., 2020; Canadian Geodetic Survey, 2019) was incorporated into the data to replace less-accurate land motion values utilized by the IPCC AR5.
Vertical land movements in Canada largely result from loading and unloading of the Earth’s surface by ice sheets. During the last ice age that ended about seven thousand years ago, much of Canada was covered with thick ice sheets that weighed down the surface of the Earth. Deep within the Earth, rock yielded and flowed and the land under the ice was pushed down. At the edges of the ice sheets, the land was pushed up. Following the thinning and retreat of those ice sheets, land that was pushed down started to rise, while land that was uplifted began to sink, a process that continues to the present day. Tectonic effects causing earthquakes and land subsidence caused by sediment compaction on coastal deltas can also generate vertical movements that contribute to relative sea-level change, but these are not accounted for in these projections.
- Canadian Geodetic Survey. (2019). NAD83(CSRS) v7. https://webapp.geod.nrcan.gc.ca/geod/tools-outils/nad83-docs.php
- Church, J.A., P.U. Clark, A. Cazenave, J.M. Gregory, S. Jevrejeva, A. Levermann, M.A. Merrifield, G.A. Milne, R.S. Nerem, P.D. Nunn, A.J. Payne, W.T. Pfeffer, D. Stammer and A.S. Unnikrishnan, 2013a. Sea Level Change. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
- Church, J.A., P.U. Clark, A. Cazenave, J.M. Gregory, S. Jevrejeva, A. Levermann, M.A. Merrifield, G.A. Milne, R.S. Nerem, P.D. Nunn, A.J. Payne, W.T. Pfeffer, D. Stammer and A.S. Unnikrishnan, 2013b. Sea Level Change Supplementary Material. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]
- James, T.S., Robin, C., Henton, J.A., and Craymer, M., 2021. Relative Sea-level Projections for Canada based on the IPCC Fifth Asssessment Report and the NAD83v70VG National Crustal Velocity Model; Geological Survey of Canada, Open File 8764, 1 .zip file, https://doi.org/10.4095/327878
- Robin, C.M.I., Craymer, M., Ferland, R., James, T.S., Lapelle, E., Piraszewski, M., and Zhao, Y., 2020. NAD83v70VG: A new national crustal velocity model for Canada; Geomatics Canada, Open File 0062, 1 .zip file, https://doi.org/10.4095/327592