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Mike Harrington

Director, EPS Department & Senior Principal Engineer

Email

mikeh@apl.washington.edu

Phone

206-543-6857

Department Affiliation

Electronic & Photonic Systems

Education

B.S. Electrical Engineering, Virginia Tech, 1990

M.S. Electrical Engineering, University of Washington - Seattle, 1992

Publications

2000-present and while at APL-UW

A thirty-month seafloor test of the A-o-A method for calibrating pressure gauges

Wilcock, W.S.D., D.A. Manalang, E.K. Fredrickson, M.J. Harrington, G. Cram, J. Tilley, J. Burnett, D. Martin, T. Kobayashi, and J.M. Paros, "A thirty-month seafloor test of the A-o-A method for calibrating pressure gauges," Front. Earth Sci., 8, doi:10.3389/feart.2020.600671, 2021.

More Info

15 Jan 2021

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 NiƱo 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.

Lessons learned from the United States ocean observatories initiative

Smith, L.M., and 16 others including G.S. Cram and M. Harrington, "Lessons learned from the United States ocean observatories initiative," Front. Mar. Sci., 5, 494, doi:10.3389/fmars.2018.00494, 2019.

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4 Jan 2019

The Ocean Observatories Initiative (OOI) is a United States National Science Foundation-funded major research facility that provides continuous observations of the ocean and seafloor from coastal and open ocean locations in the Atlantic and Pacific. Multiple cycles of OOI infrastructure deployment, recovery, and refurbishment have occurred since operations began in 2014. This heterogeneous ocean observing infrastructure with multidisciplinary sampling in important but challenging locations has provided new scientific and engineering insights into the operation of a sustained ocean observing system. This paper summarizes the challenges, successes, and failures experienced to date and shares recommendations on best practices that will be of benefit to the global ocean observing community.

Designing an offshore geophysical network in the Pacific Northwest for earthquake and tsunami early warning and hazard research

Wilcock, W.S.D., D.A. Schmidt, J.E. Vidale, M.J. Harrington, P. Bodin, G.S. Cram, J.R. Delaney, F.I. Gonzalez, D.S. Kelley, R.J. Leveque, D.A. Manalang, C. McGuire, E.C. Roland, M.W. Stoermer, J.W. Tilley, and C. Vogl, "Designing an offshore geophysical network in the Pacific Northwest for earthquake and tsunami early warning and hazard research," Proc., MTS/IEEE OCEANS Conference, 19-23 September, Monterey, CA, doi:10.1109/OCEANS.2016.7761291 (IEEE, 2016).

More Info

1 Dec 2016

Every few hundred years, the Cascadia subduction zone off the coast of the Pacific Northwest hosts devastating earthquakes, and there is a growing awareness of the need to be prepared for these events. An offshore cabled observatory extending the length of the Cascadia subduction zone would enhance the performance of the earthquake and tsunami early warning systems, would enable real time monitoring and predictions of the incoming tsunami, and would contribute substantially to scientific research aimed at mitigating the hazard. The University of Washington has recently initiated a study to develop a conceptual design for the U.S. portion of an offshore observatory for earthquake and tsunami early warning and research. This paper presents the motivation for this work and plans for the study.

Inventions

Self-calibrating Seafloor Pressure Measurement System with Increased Operational Life and Improved Reliability

Record of Invention Number: 48583

Geoff Cram, Mike Harrington, Dana Manalang, James Tilley

Disclosure

22 Mar 2019

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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