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Offshore Sea Levels Measured With an Anchored Spar‐Buoy System Using GPS Interferometric Reflectometry
Ist Teil von
Journal of geophysical research. Oceans, 2021-11, Vol.126 (11), p.n/a
Ort / Verlag
Washington: Blackwell Publishing Ltd
Erscheinungsjahr
2021
Link zum Volltext
Quelle
Wiley Online Library - AutoHoldings Journals
Beschreibungen/Notizen
Conventional tide gauges are usually housed along the coast. Satellite altimetry works well in the open ocean but poorly near the coast due to signal contamination by land returns. These limitations lead to an observational gap in the transition zone between the coast and open ocean. Using data collected by a GPS installed on top of an anchored spar‐buoy in Tampa Bay, we retrieved water levels through a combination of precise positioning and interferometric reflectometry. Individual water level retrievals agree with a nearby acoustic tide gauge (19.5 km distance) at ∼15 cm level. Amplitude and phase of the major tidal constituents are well recovered by the GPS spar‐buoy measurements. Over a 2.9‐year period, agreement of de‐tided daily mean sea levels measured by the GPS spar‐buoy and the nearby acoustic tide gauge is 4.4 cm. When sea level data measured by the GPS spar‐buoy are included in the local coastal ocean circulation model, low‐frequency error propagated from the open boundary is significantly reduced.
Plain Language Summary
GPS receivers record direct signals from satellites as well as reflected signals from local objects. The reflected signal can interfere with the direct signal, enhancing or reducing overall signal strength. This characteristic can be used to measure the height difference between the GPS antenna and the reflecting surface. We used GPS data collected by a spar‐buoy anchored in Tampa Bay to calculate water levels at different times. The calculated water levels can be used to study sea level change, ocean circulation, and tidal height predictions.
Key Points
An anchored spar‐buoy seafloor geodetic system is used to measure offshore sea levels based on Global Positioning System interferometric reflectometry (GPS‐IR)
Agreement of de‐tided daily mean sea levels measured by the GPS spar‐buoy and the closest acoustic tide gauge (19.5 km away) is 4.4 cm
Sea levels measured with the GPS spar‐buoy can help improve coastal ocean circulation models