Tide gauges and applications

Coastal tide gauges supply sea level water height measurements. In some cases they have been doing so for almost four centuries. Originally deployed for navigation and tidal prediction, their fields of application have widened considerably, from coastal engineering and littoral development to precise knowledge of variations in sea level linked to extreme events (storms, tsunamis etc.) and to climate change. For each of the applications listed, the sea level is a key parameter.

 

Some applications based on tide gauging

The poster below gives some applications of sea level measurements:

 

Comprehensive inventory of sea level measurements and related applications

 

The potential uses of tide gauge sea level measurements include:

• hydrography (tidal prediction and bathymetric sounding reduction);
• environmental studies (calibration and validation of coastal hydrodynamic models, statistical study of positive and negative surges and calculation of extreme levels for foreseeable natural risk prevention plans (PPR) etc.); 
• storm surge and tsunami alert systems;
• study of secular changes in mean sea level.
• understanding the physical processes that cause variations in mean sea level at a given location (tectonic, artificial subsidence, hydrodynamics, etc.);
• validation of climate models by comparing their results with the sea level trends observed;
• "calibration" of measurements made by radar altimeters carried by satellites (Topex/Poseidon, Envisat, Jason etc.);
• study of the transfer function between the signal observed out at sea using satellite altimetry and that observed on the coast by a tide gauge;
• evaluation and validation of the results of satellite altimetry. The drift introduced by the algorithm error, identified in 1996, demonstrated the importance of constantly comparing the results with those obtained using independent measurement techniques;
• unification of levelling networks. The reference surfaces of national altitude systems are consistent only to one metre, because each surface is fixed at mean sea level at one point on the coast;
• improvement of tidal models, in particular in complex coastal areas (bathymetry, coastline, non-linear waves etc.);
• influence of the tide on littoral ecosystems: fauna, marine farming, etc.
• study of vertical references and their relations (geoid; ellipsoid; chart datum; mean sea level etc.);

 

National programs - International Programs - construction of sea level series based on tide gauge measurements

 

National and international programs use sea level measurements to study various problems.

These include the French program SONEL (Long-term sea level variation observation system) and the international programs GLOSS (Global Sea Level Observing System) and  PSMSL (Permanent Service for Mean Sea Level). Clearly, this list is far from exhaustive.

While the GLOSS tide gauges are important to establish an indicator of climate change globally, Woodworth et Blackman (2004) point out that the scientific, economic and social value lies mainly in local variations in sea level that may deviate significantly from the global mean sea level. Constructions and analyses of consistent sea level series from historical data is one way to study these local variations. However, observation systems at all levels are needed in this turbulent environment that is inherently difficult to predict.

 

References

• La Marée - La marée océanique et côtière - Bernard Simon. Editeur Institut océanographique, 2008, 434pp.
• Woodworth P. L., D. L. Blackman (2004). Evidence for systematic changes in extreme high waters since the Mid-1970s. Journal of Climate, vol. 17, n°6, pp. 1190-1197.

 

 

Last updated: 12/12/2012