PGS: sea level change

The May meeting of the Potomac Geophysical Society will be held May 20th at the Fort Myer Officers’ Club in Arlington, VA ( in the Campaign Room.  This month’s talk will be: Comparison of Sea Levels measured by Satellite Altimetry and by Tide Gages by Cyril Galvin (Coastal Engineer, Springfield, VA).


“Present-day sea level change: Observations and causes” appeared in Reviews of Geophysics (2004). Its authors claim “global mean sea level rise is now known to be very accurate, 2.8+/-0.4mm/yr”, a rate “significantly larger than the historical rate of sea level change measured by tide gages during the past decades (in the range of 1-2mm/yr)”. The 2004 paper has been cited in the literature at least 115 times (in Web of Science database, as of 14 April 2010), usually to support a very recent acceleration of sea level rise. Tide gages have operated for centuries; satellite altimetry has been around for two decades. Both gages attempt to measure the elevation of the sea surface. The tide gage is immersed in the sea surface, the satellite altimeter orbits 100 miles away. In April 2003, I selected 14 tide gages from US coasts whose data are collected by NOAA and archived by PSMSL. The 14 are located at or near ocean coasts and have data for quarter points of the 20th century (1925, 1950, 1975, 2000). The identity of these gages was published in The New York Review of Books, 14 August 2003, a year before publication of the 2004 article quoted above. Using their study decade, 1993-2003, seven of the 14 tide gages showed lower, and seven showed higher sea levels in 2003 than in 1993. Average changes in sea level at the 14 pre-selected gages were 0.36mm/yr. This is an order of magnitude less than 2.8mm/yr quoted above for the 2004 satellite data. Further, the 14-gage average sea level is actually less than the standard deviation of the satellite altimetry data. The rate of sea level change quoted for satellite altimetry in the opening sentences above is unlikely to be correct.

Biographical Information:

Cy Galvin operates Cyril Galvin, Coastal Engineer, est 1978. As far as he knows, he was the first to begin practice solely as a coastal engineer, and he remains the longest continuously operating consulting coastal engineer. He received a BS in Geological Engineering from St Louis University (thesis: Grover Gravel, 1957); a SM from MIT (thesis: Deformed Devonian Brachiopods from Maine, 1959); a PhD from MIT (Experiments on Longshore Currents, 1963). ASCE awarded him their Norman Medal and Huber Research Prize for his experiments on water waves. He has studied sea level problems for about 30 years and has interests in science and public policy, as represented by the controversy on global warming. Born: Jersey City, 1935; resident: Springfield, Virginia, since 1974.

Dinner Menu

Baked Salmon (House salad & vegetables, rolls and butter)


Coffee / tea

A vegetarian meal can be substituted by request.

Reception at 6:30.  Dinner at 7:30.  Talk at 8:30 PM.  Please note that the talk starts earlier than the usual time. Allow 15 minutes for security entering Ft. Myer as all civilian vehicles are searched.  To ensure access to and from Fort Myer use the Hatfield Gate, open 24 hours a day (  If you wish to attend dinner ($25), please make reservations with Joydeep Bhattacharyya at 571-269-8432 or via E-mail at If you wish, please feel free to attend the talk without dinner.  Non-members and guests are welcome.  Visit the PGS web site at for new meeting announcements, etc.  Please send changes of address or email to


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s