Published data were used to analyse the long-term mean sea level trends at eight locations located in the Atlantic Ocean. Stations were located in Canada, USA, Panama and Argentina. Other “Atlantic” stations located in Europe were not included as these have been included in a seperate analysis of “Europe Sea Levels”.
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). These data are relative to the local land levels.
The span of records of the data ranged from 53 years to 160 years; the earliest record (at new York) commencing in 1856. There are records for Halifax for 1896 and 1897 but these were inconsistent with data from other stations and were not used in this analysis.
The plots shown below are of the annual means at each of the eight locations. On each plot a linear “best fit” trendline has been added. The “slope” of the trendline, expressed in cm / century, are included in the table above.
ANNUAL MEAN SEA LEVEL TRENDS FOR INDIVIDUAL STATIONS
Halifax (Canada) 1920-2012
Portland (USA) 1912-2015
New York (USA) 1856-2015
Fernandina Beach (USA) 1898-2015
Key West (USA) 1913-2015
Galveston (USA) 1958-2010
Cristobal (Panama) 1909-1979
Buenos Aires (Argentina) 1905-1987
DISCUSSION AND COMMENTS
- The annual mean sea level trend-lines for all eight stations are remarkably linear with no indication of inceasing or decreasing trend in recent decades (excluding Cristobal and Buenos Aires which had no recent data).
- The values of the trendline slopes (which do not allow for changes in local land levels) are less important than the changes (acceleration or decceleration) in the trendline slopes.
- There is a wide range in the slopes of the trendlines (+14.4 to +67.3 cm/century) at different locations, with seven of the stations within the +14.4 to +33.6 cm / century range.
- The records for Galveston have an extremely high positive trendline slope (+67.3 cm / century) which probably reflects the reported subsidence of the land level at that location.
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.