Development of a Seafloor Piston Pressure Gauge for Vertical Marine Geodesy

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The PIs request funding to develop and test a pressure gauge reference for use on the sea floor. This instrument will be based on commercially available piston gauge calibrations systems, modified for automated operation on the seafloor. A piston gauge calibration system uses a calibrated mass loaded onto a hydraulic piston to generate a pressure; the pressure can be accurately known in an absolute sense by determining the mass values, piston dimensions and the local acceleration of gravity. Such a system can be transformed into a pressure reference, a single-valued pressure source. By in-situ comparing a sea-floor pressure gauge with a pressure reference, the pressure gauge drift can be unambiguously determined and removed from the time series. The pressure reference need only be stable and highly reproducible, which presents significant metrological advantages. A reference based on commercially available instruments could achieve drift control with uncertainties of only a few parts per million, or 1 cm/year at depths of 2000 meters. Broader ImpactsThe proposed work could potentially lead to an important advance in bottom pressure instrumentation to measure crustal (ocean bottom) movement in at deep ocean depths. The drift issue of bottom ocean sensors depth sensors have been a limitation in these devices uses to measure accurately vertical movements. This approach if successful will help researchers in geodesy, tectonics, marine geology, physical oceanography, and climate studies. Increasing the absolute accuracy of long-term seafloor pressure gauge measurements by providing a reference pressure signal to calibrate and allow removal of gauge drift would allow for usage of easily deployed seafloor pressure gauges for long-term geodetic measurements and would also have other applications in seafloor and subseafloor observatories. The PIs have an excellent record of sharing the results of their research and instrument development with the oceanographic community through presentations at meeting and publication of peer-reviewed papers.