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Mike Gregg

Professor Emeritus, Oceanography

Professor, Oceanography






The idea that the cumulative action of centimeter-scale mixing affects the ocean's largest scales guides Mike Gregg's research. Evolving technology now enables the mixing to be put into the context of the meter-to-kilometer-scale processes directly producing it, such as internal waves, bottom and surface boundary layers, thermohaline staircases and intrusions, and hydraulic responses to flow constrictions. Because large-scale models, particularly coupled climate models, have grid scales vastly larger than those of the mixing and even of the intermediate-scale processes producing it, it is a goal to always try to work toward parameterizations that can be used in these models.

Department Affiliation

Ocean Physics


B.S. Physics, Yale University, 1961

Ph.D. Physical Oceanography, Scripps Institution of Oceanography, 1971


2000-present and while at APL-UW

Flow, Hydraulics, and Turbulent Mixing Over Kaena Ridge, Hawaii

Gregg, M.C., G.S. Carter, and M.H. Alford, "Flow, Hydraulics, and Turbulent Mixing Over Kaena Ridge, Hawaii," Technical Report, APL-UW TR 2308, Applied Physics Laboratory, University of Washington, Seattle, November 2023, 20 pp.

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5 Feb 2023

Measurements with a depth-cycling towed body and microstructure profilers address several important issues left unanswered by previous results from the Hawaii Ocean Mixing Experiment (HOME) in 2000 and 2002. HOME sought to understand the energetics of surface tides being converted to internal tides and turbulence in gaps along the Hawaiian Ridge. Measurements in 2002 focused on Keana Ridge in the Kauai Channel, the most accessible of the three major sites. Here, we demonstrate that horizontal kinetic energy (HKE) at the shallow end of the ridge was strongly concentrated close to the bottom, below previously reported observations. We also show where and when internal modes were hydraulically controlled and that dissipation measurements must include the thin bottom boundary layer to obtain accurate energy balances over the ridge.


Gregg, M.C., "Errata," for Ocean Mixing (Cambridge Univ. Press, 2021).

11 Aug 2022

Ocean Mixing

Gregg, M.C., "Ocean Mixing" (Cambridge University Press, 2021) 378 pp.

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1 Mar 2021

The stratified ocean mixes episodically in small patches where energy is dissipated and density smoothed over scales of centimeters. The net effect of these countless events effects the shape of the ocean's thermocline, how heat is transported from the sea surface to the interior, and how dense bottom water is lifted into the global overturning circulation. This book explores the primary factors affecting mixing, beginning with the thermodynamics of seawater, how they vary in the ocean and how they depend on the physical properties of seawater. Turbulence and double diffusion are then discussed, which determines how mixing evolves and the different impacts it has on velocity, temperature, and salinity. It reviews insights from both laboratory studies and numerical modelling, emphasising the assumptions and limitations of these methods. This is an excellent reference for researchers and graduate students working to advance our understanding of mixing, including oceanographers, atmospheric scientists and limnologists.

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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