Published data were used to analyse the long-term mean sea level trends at eleven locations located in the Pacific Ocean. Stations were located in Japan, USA, Canada, Panama, Chile, Australia and New Zealand.
The data used were all from the website of PSMSL (the Permanent Service for Mean Sea Level) which maintains a huge, worldwide database of sea level data. Only raw data were used (ie as originally recorded, without any adjustments).
The span of records of the data ranged from 69 years to 161 years (the earliest record, at San Francisco, commencing in 1855).
The plots shown below are of the annual means at each of the eleven locations. On each plot a linear “best fit” trendline has been added.
ANNUAL MEAN SEA LEVEL TRENDS FOR INDIVIDUAL STATIONS
Hosojima (Japan) 1930-2015
Ketchikan (USA) 1919-2015
Victoria (Canada) 1910-2015
Seattle (USA) 1899-2015
San Francisco (USA) 1897-2015
La Jolla (USA) 1925-2015
Honolulu (USA) 1905-2015
Balboa (Panama) 1908-2015
Antofagasta (Chile) 1946-2014
Sydney (Australia) 1886-2015
Dunedin (New Zealand) 1900-2015
DISCUSSION AND COMMENTS
- The annual mean sea level trend-lines for all eleven stations are remarkably linear with no indication of inceasing or decreasing trend in recent decades.
- There is a wide range in the slope of the trendlines (-7.5 to +22.3 cm/century) at different locations reflecting the different isostatic rebound at different locations. Hosojima, Ketchikan and Antofagasta have negative long-term trends (ie the local sea level is falling relative to the land).
This article was written by Brian Gunter of Narooma, NSW. In his previous life Brian was an engineering hydrologist involved over many years in the analysis of rainfall and river flow data for the planning of water resources projects in Australia, Asia and Africa. In recent years he has been one of the Marine Rescue NSW (previously Royal Volunteer Coastal Patrol) volunteer weather observers who operate the Narooma station for the Bureau of Meteorology.