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Geoff Cram

Senior Principal Engineer





Department Affiliation

Electronic & Photonic Systems


B.S. Mechanical Engineering, Rutgers University, 1981

M.S. Mechanical Engineering, University of Washington, 1987


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.

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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.

Inductive power mooring lines for OOI's shallow and deep profilers

McGinnis, T., G. Cram, and E. Boget, "Inductive power mooring lines for OOI's shallow and deep profilers," Sea Techol., 61, 14-18, 2020.

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1 Apr 2020

As oceanographers seek to deploy their field sensors for longer subsea campaigns, advances in mooring line construction and technology are enabling new approaches to moorings. No longer is the mooring line a passive element; instead, the development of the first inductive power mooring line by high-performance fiber-rope maker Pillystran allow it to function as an integral part of the oceanographic monitoring system.

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.

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In The News

New lab to give scientists underwater access

KIRO TV, Donna Gordon Blankinship

Scientists are eager for access to information from a quarter-billion dollar lab at the bottom of the Pacific Ocean that they hope will teach them about climate change, earthquakes and even the origins of life on Earth and other planets.

19 May 2013

Getting ready for the world's largest underwater observatory

KUOW Radio, Ashley Ahearn

The Regional Cabled Observatory is a $239 million project funded by the National Science Foundation. The goal: to better understand and monitor the depths of the Pacific Ocean — from volcanic eruptions to deep-sea earthquakes that could lead to tsunamis.

17 Apr 2013

Preparing to install the world's largest underwater observatory

UW News and Information, Hannah Hickey

The National Science Foundation in 2009 launched the $239 million effort led by John Delaney, UW professor of oceanography, to create a cabled observatory that will bring power and Internet to the ocean floor. This new concept will use remote-controlled instruments and high-bandwidth video to create an enduring, real-time presence in the deep ocean.

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15 Apr 2013

Researchers in the UW's Applied Physics Laboratory were tasked by Delaney to build and test the equipment that will make up the observatory. Much of that equipment will be installed this summer. This is the biggest project the 70-year-old marine engineering institute has ever undertaken, said project lead Gary Harkins, a principal engineer with the lab.

"This concept of a real-time observatory will change what we do as ocean engineers, what we will learn how to do, and what ocean scientists can do with these systems now and in the future," Harkins said.

The cabled observatory, known as the Regional Scale Nodes project, is part of the national Ocean Observatories Initiative, an effort to integrate U.S. measurements of the ocean and seafloor. Other partners will build coastal and global observing networks, manage the data and conduct educational outreach. The Pacific Northwest observatory will span the Juan de Fuca tectonic plate off the Washington and Oregon coasts, the likely source of the next large regional earthquake.

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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