Past, Current, and Projected Relative Sea-level Rise in Western Canada
Activity Rationale
Sea-level rise is a significant concern associated with global climate change. Although British Columbia has a predominantly rocky and high-relief coastline, certain areas are vulnerable to the impacts associated with sea-level rise. This activity evaluates the past, present, and projected changes in relative sea-level rise along the coast of British Columbia. A key element is to move from impact assessment to adaptation planning by working in collaboration with decision-makers at municipal and provincial levels.
Leader: Stephane Mazzotti
The Topic
The coast of British Columbia is characterized by a variety of geological settings, ecosystems, and human developments. The sandy beaches of the remote northern Queen Charlotte Islands contrast the rocky shores of western Vancouver Island and the highly urbanized Fraser River Delta. Relative sea-level rise (the level of ocean relative to the land) varies spatially along the coast, mostly due to variations in geological conditions and associated vertical land motion. For example, the west coast of Vancouver is being uplifted at about 2 millimeters per year (20 cm per century) relative to the region around Victoria.
In order to adapt to the impacts associated with relative sea-level rise, it is important to understand regional variations in projected sea-level changes. In this activity scientists used measurements of vertical land motion using geodetic techniques and measurements of sea-level change from tide gauges to estimate spatial variations in relative sea-level rise and fall during the 20th century. This analysis, combined with estimates of future regional sea-level rise, has been used to estimate future relative sea-level rise during the 21st century for regions along the coast of British Columbia.
Results
The Coast of British Columbia
The integration of Global Positioning System (GPS) data and tide gauge measurements show that sea level in the northeast Pacific rose by about 1.8 mm/yr during the 20th century. This rate is similar to the global average rate of sea-level rise, suggesting that projections of global average sea-level change may be appropriate for the northeast Pacific. Vertical land motions mapped along the coast of British Columbia show variations of up to 2 to 4 mm/yr over distances as short as 50 km.
Using this information, projections of relative sea-level rise by the end of the 21st century were determined for the coast of British Columbia with estimates varying between 10 and 140 cm. Due to the many uncertainties in predicting future sea levels, estimates were made for a wide range of possible outcomes. For example, a minimum rise of about 20 cm is projected for Victoria with a higher, more likely, projection of about 90 cm.
For more detailed information about this study, see the summary report for the BC Ministry of Environment “Projected Sea Level Changes for British Columbia in the 21st Century”. The report is a summary of the technical report "An Examination of the Factors Affecting Relative and Absolute Sea Level in Coastal British Columbia".
Fraser River Delta and Greater Vancouver
A high-resolution study of vertical land motion was carried out in the Fraser River Delta/Greater Vancouver region to estimate the impact of delta sediment subsidence on vertical land motion and relative sea-level rise. Using a combination of space radar interferometry data, GPS data, and conventional leveling data, scientists mapped the patterns and magnitude of subsidence due to natural and anthropogenic sediment consolidation in the Fraser River delta. Subsidence rates as high as 5 to 10 mm/yr have been mapped in regions of high urban and industrial development. On the basis of this study, projected relative sea-level rise could reach up to 1 to 2 meters in some areas of the Fraser delta.
Map of subsidence rates in the Fraser River delta. Areas in yellow are stable. Areas in light blue are subsiding at about 1 to 2 mm/yr. Areas in dark blue are subsiding at about 5-10 mm/yr.
[JPEG, 1.7 Mb, 1500 X 1159, notice]
Study Data
Data is available for Fraser Delta subsidence (methods and results of subsidence studies using satellite-based radar data that measured subsidence of buildings on the Fraser River Delta) from Geological Survey of Canada Open File #5698
Publications
Please note that subscriptions may be required to access some articles. To request a copy of publications, or for any more information, please contact Stephane Mazzotti.
- Check for more recent publications in GEOSCAN, the publications database of the Geological Survey of Canada and the Canada Centre for Remote Sensing.
Lambert, A., S. Mazzotti, M. Van der Kooij, A. Mainville, 2008, Subsidence and Relative Sea Level Rise in the Fraser River Delta, Greater Vancouver, British Columbia, from Combined Geodetic Data. Geological Survey of Canada Open File #5698.
Mazzotti, S., A. Lambert, N. Courtier, L. Nykolaishen, and H. Dragert, 2007, Crustal uplift and sea level rise in northern Cascadia from GPS, absolute gravity, and tide gauge data. Geophysical Research Letters, 34, L15306, doi:10.1029/2007GL030283.
Mazzotti, S., C. Jones, R. Thomson, 2008, Relative and Absolute Sea-Level Rise in Western Canada and North-western U.S. from a Combined Tide Gauge-GPS Analysis. Journal of Geophysical Research, 113, C11019 doi:10.1029/2008JC004835.
Mazzotti, S., A. Lambert, M. Van der Kooij, A. Mainville, 2009, Impact of Anthropogenic Subsidence on Relative Sea-Level Rise in the Fraser River Delta. Geology, in press (as of April 2009).
Thomson, R.E., B.D. Bornhold, and S. Mazzotti, 2008, An Examination of the Factors Affecting Relative and Absolute Sea Level in Coastal British Columbia. Canadian Technical Report of Hydrography and Ocean Sciences, 260, p.49.
Other Materials
Bornhold, B.D., 2008, Projected sea level changes for British Columbia in the 21st century, report for the BC Ministry of Environment, p. 11.