This indicator reports on sea-level projections at coastal communities in the Northwest Territories (NWT).
Sea-level projections are estimated in Arctic regions by combining data on global sea level changing due to a warming climate, postglacial rebound (“vertical land motion”), and sea-level fingerprinting - the contribution to global sea-level rise from each major ice-cap in the world. This indicator also presents evidence of the effects of sea-level rise on the Mackenzie Delta and on other coastal areas along the Beaufort Sea in the NWT.
Sea-level projections for NWT communities along the Beaufort Sea were estimated for this NWT State of Environment report by Thomas James, Geological Survey of Canada, Natural Resources Canada, based on the methods described in a study generated by the Nunavut Climate Change Partnership3. Estimates and uncertainties of vertical crustal motion were derived from information on past sea levels, as described in James et al. (2011)3.
This indicator is an output of the Earth Sciences Sector (ESS) Climate Change Geoscience Program of Natural Resources Canada. Text and calculations are by Thomas James, peer-reviewed by Don Forbes. This is ESS contribution number 20110177. The “NWT focus” and “looking forward” sections were drafted by ENR, GNWT.
Increases in sea levels are partly responsible for the observed and projected changes on the Mackenzie Delta ecosystem and other coastal areas in the NWT. Projected sea-level changes in the Beaufort Sea are an important component of future changes to NWT coasts and have the potential to affect infrastructure, ecosystems, and biodiversity (see Focal point Genetic Resources).
Global sea levels
Globally, sea level is projected to rise through the twenty-first century by at least a few tens of centimetres5, Table 10.7 and and possibly by more than one metre2,8,9. Sea-level rise greater than two metres by the year 2100 appears to be physically implausible.7
Vertical land motion
Locally, the amount of sea-level change is affected by two additional factors. First, vertical land motion affects the amount of sea-level change that is experienced locally. If the land is sinking, sea-level rise will be increased locally, and if the land is rising, sea-level rise will be decreased locally. In the Canadian Arctic, vertical land motion is occurring primarily as a delayed response to the surface unloading caused by the thinning and retreat of the continental ice sheets at the end of the last ice age. This delayed response is called postglacial rebound or glacial isostatic adjustment.
Unlike some parts of Nunavut, such as western Hudson Bay, where the land is rising quite rapidly at nearly one centimetre per year, coastal communities in the NWT are located near the periphery of the former ice sheet and vertical land motion is much slower.
Within the periphery of the former ice sheet, the land was pushed down during glaciation, and, deep within the Earth, material flowed horizontally away from the region of loading, causing uplift outside the ice sheet. Now that the ice sheet is gone, depressed regions are rising and regions that were uplifted are sinking. In the Northwest Territories, vertical land motion ranges from uplift of about 1 mm/year in the east at Ulukhaktok, to no motion at Paulatuk, to subsidence of 1 mm/year and 2.5 mm/year at Sachs Harbour and Tuktoyaktuk, respectively. The rates have an uncertainty of 2 mm/year. This is an estimate of the vertical motion of bedrock, and does not take into account subsidence due to compaction or thawing permafrost, nor does it take into account possible vertical motion due to tectonic activity. Continued and new monitoring with Global Positioning System (GPS) installations will, with time, provide direct observations of vertical crustal motion at sites of interest. Recent progress with new processing strategies and updated reference frames is very promising.
The second factor that affects projections of local sea-level change is the uneven redistribution of meltwater from glaciers, ice caps, and ice sheets. The effect is called sea-level fingerprinting. Owing to the reduced gravitational attraction of a shrinking ice mass, sea level falls close to a body of ice that is shrinking and providing meltwater to the oceans. In the Canadian Arctic, the effect is quite important. For example, if Greenland is contributing one millimetre per year to global sea-level rise, locally sea level will fall by 1.2 mm/yr at Iqaluit. Further away, the effect is smaller. In coastal communities in the Northwest Territories the local sea level rise ranges from +0.2 mm/yr (Tuktoyaktuk) to -0.1 mm/yr (Ulukhaktok) for a 1 mm/yr Greenland contribution to global sea-level rise. Paulatuk and Sachs Harbour have intermediate values. Because the Greenland ice sheet is an important contributor to global sea-level rise projections, sea-level fingerprinting reduces projections of local sea-level rise in the Canadian Arctic.
Projected sea-level NWT communities along the Beaufort Sea
Sea-level projections are given in the figure above. The projections show that all four communities are expected to experience sea-level rise in the 21st century, with the exception of Ulukhaktok and Paulatuk, which may experience a few centimeters of sea-level fall at the low end of the range of projections. At the upper end of the projections, Sachs Harbour and tuktoyaktuk may be subjected to nearly one metre of sea-level rise. For Ulukhaktok, sea level is not expected to fall by more than 10 cm or rise by more than 70 cm. For Sachs Harbour, sea-level is expected to rise at least 7 cm and to probably not rise by more than 90 cm.
These projections presented here are for the change in mean sea level. For the permafrost-rich sediments that comprise much of the Beaufort coastline of the NWT, changes in storminess, sea ice, wave energy, and water and air temperatures, among other facotrs, may have a greater impact than changes in mean sea level. These factors are not considered here. The projections are based on current information. It is anticipated that advances in the understanding of projected global sea levels and in the understanding and observation of local effected, such as vertical land motion, will lead to future revisions in projected sea levels.
For the Beaufort Sea coast, all information point to some increase in sea levels at most NWT communities. The Beaufort Sea coastline, on the mainland and elsewhere, is rich in ice and unconsolidated, and has been eroding quickly4.
It is predicted that sea level rise, working in concert with autumn storms4 and reduced sea ice, will result in increasing exposure of the Mackenzie Delta to extensive storm surges6. In 1999, an exceptionally high surge moved salt water far above the normal surge lines, transforming the outer delta ecosystem, killing shrubs and changing the ecology of some delta lakes from freshwater systems to brackish ones6. Evidence from traditional knowledge, shrub growth (dendrochronology) and lake diatoms show that this type of large scale storm surge had never occurred in the Mackenzie Delta in the past 1,000 years. This type of event may become the new norm6.
NWT projections of sea-level rise, for 90 years to the year 2100, were generated for this report using the methods and assumptions of James et al. (2011)3. In their study, sea-level projections were generated for five Nunavut communities, taking into account vertical land motion and sea-level fingerprinting, as described above. Their assessment of the likely amount of global sea-level change, based on the available scientific literature, ranged from 28 cm to 115 cm from 2010 to the year 2100 (a range of 87 cm).
Iqaluit is projected to experience a sea level rise of up to 70 cm by 21003. Not all Arctic coastal areas have projected sea level rise. Sea levels could decrease along the western coast of Hudson Bay – by as much as 70 cm at Arviat and 75 cm at Whale Cove in the next 90 years (from 2010 to 2100)3.
For more information
- Presentation on projected sea level rises in Nunavut.
- For more information on global climate change go to the Intergovernmental Panel on Climate Change.
Other focal points
Found an error or have a question? Contact the team at NWTSOER@gov.nt.ca.
Ref. 1. Dyke. A.S. 1996. Preliminary Paleogeographic maps of glaciated North America. Geological Survey of Canada, Open File 3296.
Ref. 2. Grinsted, A., J.C. Moore, and S. Jevrejeva. 2009. Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD. Climate Dynamics (34) 4610472.
Ref. 3. James, T.S., K.M. Simon, D.L. Forbes, A.S. Dyke, and D.J. Mate. 2011. Sea-level Projections for Five Pilot Communities of the Nunavut Climate Change Partnership; Geological Survey of Canada. Open File 6715. 23pp.
Ref. 4. Krupnik I., and D. Jolly (eds). 2002. The Earth is faster now; Indigenous observations of Arctic environmental change. Fairbank, AK.
Ref. 5. Meehl, G.A., et al. 2007. Global Climate Projections. In: Climate Change 2007: The Physical Science Basis, contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, ed. S. Soloman and others. Cambridge University Press. Cambridge, United Kingdon and New York, NY.
Ref. 6. Pisaric M.F.J., J.R.K.S.V. Thienpont, H.L.T.C. Nesbitt, S. Solomon, and J.P. Smol. 2011. Impacts of a recent storm surge on an Arctic delta ecosystem examined in teh context of hte last millennium. Proceedings of hte National Academy of Sciences 108:8960-8965
Ref. 7. Pfeffer, W.T., J.T. Harper, and S. O'Neel. 2008. Kinematic constraints on glacier contributions to the 21st century sea-level rise. Science (321) 1340-1343.
Ref. 8. Rahmstorf, S. 2007. A semi-empirical approach to projecting future sea-level rise. Science (315) 368-370.
Ref. 9. Vermeer, M. and S. Rahmstorf. 2009. Global sea level linked to global temperature. Proceedings of the National Academy of Sciences (106) 21527-21532.