Relative and absolute sea level rise in western Canada and northwestern United States from a combined tide gauge‐GPS analysis

Abstract

[1] Empirical studies and climate models suggest large variations of absolute sea level (ASL) changes between oceanic basins. Such potential variations raise concern on the applicability of global mean ASL predictions to specific regions and on estimates of relative sea level (RSL) hazards. We address this issue for the western Canada and northwestern United States coastline by estimating the 20th century ASL rate using a combination of 34 colocated tide gauge and Global Positioning System (GPS) stations. The tide gauge data are quality controlled and corrected for spatially and temporally correlated sea level transients in order to derive robust RSL trends and standard errors. Reference frame and other GPS-specific issues are considered as part of the error budget in absolute GPS vertical velocities. Our combined tide gauge-GPS analysis, aligned to the International Terrestrial Reference Frame 2000, indicates a northeast Pacific ASL rise of 1.8 ± 0.2 mm/a through the 20th century, which is similar to accepted rates for the global eustatic mean. For the period 1993-2003, we find a regional ASL rate of À4.4 ± 0.5 mm/a consistent with satellite altimetry. On the basis of the Intergovernment Panel on Climate Change Assessment Report 4 mean scenario and our assessment of coastal motions from GPS and tide gauge data, we derive a map of predicted 21st century RSL rise in western Canada and the northwestern United States. Variations in coastal uplift strongly affect spatial RSL patterns. Subsidence of southern Puget Sound may significantly increase RSL rise in the Seattle-Tacoma metropolitan area. Conversely, tectonic uplift along parts of the outer west coast may reduce future RSL rise by up to 50-100%.Citation: Mazzotti, S., C. Jones, and R. E. Thomson (2008), Relative and absolute sea level rise in western Canada and northwestern United States from a combined tide gauge-GPS analysis,

Carbon Stocks and Accumulation Rates in Salt Marshes of the Pacific Coast of Canada

“…We suggest two factors that may have contributed to this result. a consequence of tectonic uplift in the region (Mazzotti et al 2008). Therefore, the mechanism of vertical accretion may be different from that observed in marshes experiencing rising sea level.…”

Post-glacial sea-level change along the Pacific coast of North America

“…These results are independent of the eustatic or regional sea-level changes. Similarly, Mazzotti et al (2008) reported upward vertical velocities of between 1 and 3 mm a À1 for coastal sites throughout the Cascadian region, but did not attempt to partition the signal into interseismic strain and isostatic rebound. Inland sites tended towards lower vertical velocities, with slight subsidence in some cases (to À1 mm a À1 ).…”

Quantifying spatial and temporal trends in beach–dune volumetric changes using spatial statistics

“…The dune complex is located toward the southern end of a 10 km-long embayed beach within Wickaninnish Bay, which has a southwest aspect to the Pacific Ocean, a mesotidal range (spring tide rangẽ 4.2 m), and is exposed to energetic wave conditions (average winter significant wave height of 2.47 m and period 12.07 s). Beaches in the area are wide, dissipative and backed by 1 to 5 m high vegetated foredunes that are prograding at a rate of approximately 0.2 m a −1 (Heathfield and Walker, 2011) in response to regression of relative sea level in response to crustal uplift along the Cascadia subduction zone (Mazzotti et al, 2008). The foredunes are backed by one of the largest active transgressive dune complexes on Vancouver Island.…”