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Ramsey Harcourt

Principal Oceanographer

Email

harcourt@apl.washington.edu

Phone

206-221-4662

Research Interests

Large Eddy Simulation (LES), Computational Fluid Dynamics, Deep Convection, Wave and Ice Boundary Layers, Response of Drifters to Convection

Department Affiliation

Ocean Physics

Publications

2000-present and while at APL-UW

Northern Arabian Sea Circulation-Autonomous Research (NASCar): A research initiative based on autonomous sensors

Centurioni, L.R., and 33 others, including R.R. Harcourt, C.M. Lee, L. Rainville, and A.Y. Shcherbina, "Northern Arabian Sea Circulation-Autonomous Research (NASCar): A research initiative based on autonomous sensors," Oceanography, 30, 74-87, doi:10.5670/oceanog.2017.224, 2017.

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1 Jun 2017

The Arabian Sea circulation is forced by strong monsoonal winds and is characterized by vigorous seasonally reversing currents, extreme differences in sea surface salinity, localized substantial upwelling, and widespread submesoscale thermohaline structures. Its complicated sea surface temperature patterns are important for the onset and evolution of the Asian monsoon. This article describes a program that aims to elucidate the role of upper-ocean processes and atmospheric feedbacks in setting the sea surface temperature properties of the region. The wide range of spatial and temporal scales and the difficulty of accessing much of the region with ships due to piracy motivated a novel approach based on state-of-the-art autonomous ocean sensors and platforms. The extensive data set that is being collected, combined with numerical models and remote sensing data, confirms the role of planetary waves in the reversal of the Somali Current system. These data also document the fast response of the upper equatorial ocean to monsoon winds through changes in temperature and salinity and the connectivity of the surface currents across the northern Indian Ocean. New observations of thermohaline interleaving structures and mixing in setting the surface temperature properties of the northern Arabian Sea are also discussed.

On the role of sea-state in bubble-mediated air-sea gas flux during a winter storm

Liang, J.-H., S.R. Emerson, E.A. D'Asaro, C.L. McNeil, R.R. Harcourt, P.P. Sullivan, B. Yang, and M.F. Cronin, "On the role of sea-state in bubble-mediated air-sea gas flux during a winter storm," J. Geophys. Res., 122, 2671-2685, doi:10.1002/2016JC012408, 2017.

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1 Apr 2017

Oceanic bubbles play an important role in the air-sea exchange of weakly soluble gases at moderate to high wind speeds. A Lagrangian bubble model embedded in a large eddy simulation model is developed to study bubbles and their influence on dissolved gases in the upper ocean. The transient evolution of mixed-layer dissolved oxygen and nitrogen gases at Ocean Station Papa (50°N, 145°W) during a winter storm is reproduced with the model. Among different physical processes, gas bubbles are the most important in elevating dissolved gas concentrations during the storm, while atmospheric pressure governs the variability of gas saturation anomaly (the relative departure of dissolved gas concentration from the saturation concentration). For the same wind speed, bubble-mediated gas fluxes are larger during rising wind with smaller wave age than during falling wind with larger wave age. Wave conditions are the primary cause for the bubble gas flux difference: when wind strengthens, waves are less-developed with respect to wind, resulting in more frequent large breaking waves. Bubble generation in large breaking waves is favorable for a large bubble-mediated gas flux. The wave-age dependence is not included in any existing bubble-mediated gas flux parameterizations.

Submesoscale streamers exchange water on the north wall of the Gulf Stream

Klymak, J.M., R.K. Shearman, J. Gula, C.M. Lee, E.A. D'Asaro, L.N. Thomas, R.R. Harcourt, A.Y. Shcherbina, M.A. Sundermeyer, J. Molemaker, and J.C. McWilliams, "Submesoscale streamers exchange water on the north wall of the Gulf Stream," Geophys. Res. Lett., 43, 1226-1233, doi:10.1002/2015GL067152, 2016.

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16 Feb 2016

The Gulf Stream is a major conduit of warm surface water from the tropics to the subpolar North Atlantic. Here we observe and simulate a submesoscale (<20 km) mechanism by which the Gulf Stream exchanges water with subpolar water to the north. Along isopycnals, the front has a sharp compensated temperature-salinity contrast, with distinct mixed water between the two water masses 2 and 4 km wide. This mixed water does not increase downstream despite substantial energy available for mixing. A series of streamers detrain this water at the crest of meanders. Subpolar water replaces the mixed water and resharpens the front. The water mass exchange accounts for a northward flux of salt of 0.5–2.5 psu m2 s-1, (large-scale diffusivity O (100 m2 s-1)). This is similar to bulk-scale flux estimates of 1.2 psu m2 s-1 and supplies fresher water to the Gulf Stream required for the production of 18° subtropical mode water.

More Publications

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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