New Approaches to In Situ Calibration for Seafloor Geodetic Measurements

Wilcock, William S. D.; Manalang, Dana; Harrington, Michael; Fredrickson, Erik K.; Cram, G.; Tilley, J.; Burnett, Justin; Martin, Deborah; Kobayashi, Taro; Paros, Jerome M.

doi:10.1109/oceanskobe.2018.8559178

Cited by 4 publications

(2 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both are essential for global coverage and currently lack high temporal and spatial resolution. A new method for routine in situ calibration (better than 1 mm/year; Wilcock et al, 2018) promises transformative improvement in measurement of OBP that will greatly facilitate the separation of mass and steric/heat content effects on sea level (Ponte, 2012). Recent work demonstrates the importance of OBP measurements in resolving meridional overturning circulation transport, and the possibility of optical clocks that sense changes in gravity (Hughes et al, 2018).…”

Section: Sensors and Emerging Technologiesmentioning

confidence: 99%

Global Observing Needs in the Deep Ocean

et al. 2019

View full text Add to dashboard Cite

The deep ocean below 200 m water depth is the least observed, but largest habitat on our planet by volume and area. Over 150 years of exploration has revealed that this dynamic system provides critical climate regulation, houses a wealth of energy, mineral, and biological resources, and represents a vast repository of biological diversity. A long history of deep-ocean exploration and observation led to the initial concept for the Deep-Ocean Observing Strategy (DOOS), under the auspices of the Global Ocean Observing System (GOOS). Here we discuss the scientific need for globally

show abstract

Section: Sensors and Emerging Technologiesmentioning

confidence: 99%

Global Observing Needs in the Deep Ocean

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Sasagawa and Zumberge (2013) have developed a self‐calibrating pressure recorder (SCPR) that can determine its own drift rate with an uncertainty of 1 cm/year or less by periodically checking itself using a piston gauge. The ambient‐zero‐ambient (A‐0‐A) method for calibrating pressure observations was developed by Wilcock et al (2018). The A‐0‐A method utilizes an internal reference pressure of near‐ambient atmospheric pressure to calibrate pressure gauges and reduce relative drift between two pressure gauges to less than 1 mm.…”

Section: Introductionmentioning

confidence: 99%

Mobile Pressure Calibrator for the Development of Submarine Geodetic Monitoring Systems

et al. 2020

View full text Add to dashboard Cite

Monitoring long-term vertical seafloor displacements at the centimeter scale using a pressure gauge network in the seismogenic zone is key to understanding the real-time strength of interplate coupling. The mobile pressure calibrator (MPC) was developed for calibrating a seafloor pressure gauge network with a resolution of less than 1 hPa/year, equivalent to about 1 cm/year. Inherent drift of the seafloor pressure gauges is estimated by comparing the raw observations between the seafloor pressure gauges and the MPC and subsequently subtracting the long-term pressure data. In October 2018, three in situ pressure measurements were conducted to evaluate the measurement uncertainty of the MPC. The calibrator was placed adjacent to a seafloor pressure gauge, which is installed at a depth of about 1,750 m in the Nankai Trough offshore Japan, and measured the pressure differences between the calibrator and the seafloor pressure gauge. The drift component of the pressure gauge used inside the MPC was estimated and corrected based on calibrations performed in the laboratory before and after the in situ seafloor pressure measurements. The results indicated an uncertainty of 0.04 hPa for the in situ measurements and therefore the possibility of detecting small, long-term seafloor displacements. We continue to compare the MPC and seafloor pressure gauge deviations over intervals of several months to years and estimate the drift of the seafloor pressure gauge. Plain Language Summary In the Nankai Trough, Japan, large earthquakes have repeatedly occurred. The Dense Ocean floor Network system for Earthquakes and Tsunamis (DONET) consisting of 51 observatories, each equipped with a pressure gauge to study vertical deformation and tsunami signals, was installed spanning the region. Crustal deformation is a key parameter for estimating plate coupling strength in subduction zones. The DONET pressure gauge network could be useful for measuring long-term vertical deformation; however, pressure gauges inherently drift at rates up to 10 hPa/year, about 10 cm/year, which likely exceed seafloor displacement rates. It is necessary to correct gauge drift to reliably detect small seafloor displacements. The mobile pressure calibrator (MPC) was developed to correct drift within the DONET pressure gauge network and enable seafloor displacement measurements on the order of 1 cm. In October 2018, we conducted three pressure measurements at a DONET pressure gauge to evaluate the MPC accuracy. We determined an uncertainty of 0.04 hPa, 0.04 cm equivalent, which should enable seafloor vertical displacement measurements better than 1 cm. Continued DONET pressure gauge MPC calibrations could enable high-density and real-time vertical displacement measurements above the seismogenic zone and contribute to understanding plate coupling strength and earthquake and tsunami hazards.

show abstract

A Thirty-Month Seafloor Test of the A-0-A Method for Calibrating Pressure Gauges

et al. 2021

View full text Add to dashboard Cite

Geodetic observations in the oceans are important for understanding plate tectonics, earthquake cycles and volcanic processes. One approach to seafloor geodesy is the use of seafloor pressure gauges to sense vertical changes in the elevation of the seafloor after correcting for variations in the weight of the overlying oceans and atmosphere. A challenge of using pressure gauges is the tendency for the sensors to drift. The A-0-A method is a new approach for correcting drift. A valve is used to periodically switch, for a short time, the measured pressure from the external ocean to the inside of the instrument housing at atmospheric pressure. The internal pressure reading is compared to an accurate barometer to measure the drift which is assumed to be the same at low and high pressures. We describe a 30-months test of the A-0-A method at 900 m depth on the MARS cabled observatory in Monterey Bay using an instrument that includes two A-0-A calibrated pressure gauges and a three-component accelerometer. Prior to the calibrations, the two pressure sensors drift by 6 and 2 hPa, respectively. After the calibrations, the offsets of the corrected pressure sensors are consistent with each other to within 0.2 hPa. The drift corrected detided external pressure measurements show a 0.5 hPa/yr trend of increasing pressures during the experiment. The measurements are corrected for instrument subsidence based on the changes in tilt measured by the accelerometer, but the trend may include a component of subsidence that did not affect tilt. However, the observed trend of increasing pressure, closely matches that calculated from satellite altimetry and repeat conductivity, temperature and depth casts at a nearby location, and increasing pressures are consistent with the trend expected for the El Niño Southern Oscillation. We infer that the A-0-A drift corrections are accurate to better than one part in 105 per year. Additional long-term tests and comparisons with oceanographic observations and other methods for drift correction will be required to understand if the accuracy the A-0-A drift corrections matches the observed one part in 106 per year consistency between the two pressure sensors.

show abstract

New Approaches to In Situ Calibration for Seafloor Geodetic Measurements

Cited by 4 publications

References 17 publications

Global Observing Needs in the Deep Ocean

Global Observing Needs in the Deep Ocean

Mobile Pressure Calibrator for the Development of Submarine Geodetic Monitoring Systems

A Thirty-Month Seafloor Test of the A-0-A Method for Calibrating Pressure Gauges

Contact Info

Product

Resources

About