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Luc Rainville

Principal Oceanographer

Affiliate Assistant Professor, Oceanography






Dr. Rainville's research interests reside primarily in observational physical oceanography and span the wide range of spatial and temporal scales in the ocean. From large-scale circulation to internal waves to turbulence, the projects he is involved in focus on the interactions between phenomena of different scales. He is motivated to find simple and innovative ways to study the ocean, primarily through sea-going oceanography but also using with remote sensing and modeling.

In particular, Luc Rainville is interested in how phenomena typically considered 'small-scale' impact the oceanic system as a whole.

* Propagation of internal waves through eddies and fronts.
* Water mass formation and transformation by episodic forcing events.
* Mixing and internal waves in the Arctic and in the Southern Ocean.

Dr. Rainville joined the Ocean Physics Department at APL-UW at the end of 2007.

Department Affiliation

Ocean Physics


B.Sc. Physics, McGill University, 1998

Ph.D. Oceanography, Scripps Institution of Oceanography, 2004


Stratified Ocean Dynamics of the Arctic — SODA

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31 Oct 2016

Vertical and lateral water properties and density structure with the Arctic Ocean are intimately related to the ocean circulation, and have profound consequences for sea ice growth and retreat as well as for prpagation of acoustic energy at all scales. Our current understanding of the dynamics governing arctic upper ocean stratification and circulation derives largely from a period when extensive ice cover modulated the oceanic response to atmospheric forcing. Recently, however, there has been significant arctic warming, accompanied by changes in the extent, thickness distribution, and properties of the arctic sea ice cover. The need to understand these changes and their impact on arctic stratification and circulation, sea ice evolution, and the acoustic environment motivate this initiative.

The Submesoscale Cascade in the South China Sea

This research program is investigating the evolution of submesoscale eddies and filaments in the Kuroshio-influenced region off the southwest coast of Taiwan.

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26 Aug 2015

Science questions:
1. What role does the Kuroshio play in generating mesoscale and submesoscale variability modeled/observed off the SW coast of Taiwan?
2. How does this vary with atmospheric forcing?
3. How do these features evolve in response to wintertime (strong) atmospheric forcing?
4. What role do these dynamics play in driving water mass evolution and interior stratification in the South China Sea?
5. What role do these dynamics/features have on the transition of water masses from northern SCS water into the Kuroshio branch water/current and local flow patterns?

Salinity Processes in the Upper Ocean Regional Study — SPURS

The NASA SPURS research effort is actively addressing the essential role of the ocean in the global water cycle by measuring salinity and accumulating other data to improve our basic understanding of the ocean's water cycle and its ties to climate.

15 Apr 2015

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Tasmania Internal Tide Experiment

The Tasmanian continental slope will be instrumented with a range of tools including moored profiler, chi-pods, CTDs, and gliders to understand the process, strength, and distribution of ocean mixing from breaking internal waves.

27 Nov 2011

Internal Waves in Straits Experiment (IWISE)

With field work in the summers of 2010 and 2011, this project focuses on understanding the mechanisms controlling the generation of internal tides in the two-ridge system of Luzon Strait, along with their propagation, contribution to mixing (dissipation) and interaction with the Kuroshio.

27 Sep 2011

Global Internal Tides from Altimetry

This collaborative project with Dr. Harper Simmons (U. Alaska), aims to construct a global map of low-mode internal tide energy flux and dissipation by application of state-of-the-art techniques to a combination of satellite altimetry, moorings, and a numerical model.

27 Sep 2011

Arctic Mixing: Changing Seasonality of Wind-driven Mixing

The Arctic Ocean, as we have come to know it over the last decades, is a quiescent, highly stratified ocean, with subsurface reservoirs and boundary sources of heat and nutrients that are often isolated from surface processes and the photic zone. The primary reason for this quiescence is believed to be the dominant presence of sea-ice, which acts to isolate the ocean from the mixing effects of wind. With the summer sea-ice reduction now exposing over 60% of the Arctic Ocean to the seasonal effects of wind forcing, it is urgent to consider the potential impacts of this available wind energy on the seasonality of the Arctic system. We suggest that the expanding extent and duration of seasonal open water in the Arctic has the potential to reshape the properties and stratification of the upper ocean, dramatically altering mixed layer depths, strengthening the internal wave field by at least an order of magnitude, thus enhancing turbulent mixing in the halo/pycnocline. If sufficiently strong, this enhanced mixing could bring nutrients and heat from the Pacific Waters into the surface and photic zone, with implications for Arctic ecosystems, surface fluxes, and feedbacks to sea-ice formation. In this collaborative proposal, we are using theory, observations and simple models to examine changes in Arctic mixed layer depths and internal wave energy and to predict impacts on Arctic ecosystems and the heat and freshwater balances of the Arctic.


Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES)

DIMES is a US/UK field program aimed at measuring diapycnal and isopycnal mixing in the Southern Ocean, along the tilting isopycnals of the Antarctic Circumpolar Current.


Changes in Seasonality in the Arctic Ocean

The Arctic sea ice cover impedes the generation and damps the propagation of surface and internal waves. As more and more of the deep Arctic Ocean becomes ice-free in the summer, wind-driven inertial waves and mixing are likely to become increasingly important. This project studies the consequences of the decreasing ice cover on the stratification of the upper ocean as well as its impacts on the geochemistry and biological productivity of the Arctic system.


Salinity Processes in the Upper-Ocean Regional Study (SPURS)

In conjunction with the new Aquarius satellite mission, which will measure sea surface salinity from space, this project aims to directly measure an annual cycle of upper ocean salinity in the North Atlantic using by high-resolution glider surveys.



2000-present and while at APL-UW

Autonomous multi-platform observations during the Salinity Processes in the Upper-ocean Regional Study

Lindstrom, E.J., A.Y. Shcherbina, L. Rainville, J.T. Farrar, L.R. Centurioni, S. Dong, E.A. D’Asaro, C. Eriksen, D.M. Fratantoni, B.A. Hodges, V. Hormann, W.S. Kessler, C.M. Lee, S.C. Riser, L. St. Laurent, and D.L. Volkov, "Autonomous multi-platform observations during the Salinity Processes in the Upper-ocean Regional Study," Oceanography, 38-48, doi:, 2017.

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1 Jun 2017

The Salinity Processes in the Upper-ocean Regional Study (SPURS) aims to understand the patterns and variability of sea surface salinity. In order to capture the wide range of spatial and temporal scales associated with processes controlling salinity in the upper ocean, research vessels delivered autonomous instruments to remote sites, one in the North Atlantic and one in the Eastern Pacific. Instruments sampled for one complete annual cycle at each of these two sites, which are subject to contrasting atmospheric forcing. The SPURS field programs coordinated sampling from many different platforms, using a mix of Lagrangian and Eulerian approaches. This article discusses the motivations, implementation, and first results of the SPURS-1 and SPURS-2 programs.

Multi-month dissipation estimates using microstructure from autonomous underwater gliders

Rainville, L., J.I. Gobat, C.M. Lee, and G.B. Shilling, "Multi-month dissipation estimates using microstructure from autonomous underwater gliders," Oceanography, 30, 49-50, doi:10.5670/oceanog.2017.219, 2017.

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1 Jun 2017

Ocean turbulence is inherently episodic and patchy. It is the primary mechanism that transforms water mass properties and drives the exchanges of heat, freshwater, and momentum across the water column. Given its episodic nature, capturing the net impact of turbulence via direct measurements requires sustained observations over extended temporal and/or broad spatial scales.

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.

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ASIRI: An ocean–atmosphere initiative for Bay of Bengal

Wijesekera, H.W., and 46 others, including C.M. Lee, L. Rainville, and K.M. Stafford, "ASIRI: An ocean–atmosphere initiative for Bay of Bengal," Bull. Am. Meteor., Soc., 97, 1859-1884, doi:10.1175/BAMS-D-14-00197.1, 2016.

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1 Oct 2016

Air–Sea Interactions in the Northern Indian Ocean (ASIRI) is an international research effort (2013–17) aimed at understanding and quantifying coupled atmosphere–ocean dynamics of the Bay of Bengal (BoB) with relevance to Indian Ocean monsoons. Working collaboratively, more than 20 research institutions are acquiring field observations coupled with operational and high-resolution models to address scientific issues that have stymied the monsoon predictability. ASIRI combines new and mature observational technologies to resolve submesoscale to regional-scale currents and hydrophysical fields. These data reveal BoB’s sharp frontal features, submesoscale variability, low-salinity lenses and filaments, and shallow mixed layers, with relatively weak turbulent mixing. Observed physical features include energetic high-frequency internal waves in the southern BoB, energetic mesoscale and submesoscale features including an intrathermocline eddy in the central BoB, and a high-resolution view of the exchange along the periphery of Sri Lanka, which includes the 100-km-wide East India Coastal Current (EICC) carrying low-salinity water out of the BoB and an adjacent, broad northward flow (~300 km wide) that carries high-salinity water into BoB during the northeast monsoon. Atmospheric boundary layer (ABL) observations during the decaying phase of the Madden–Julian oscillation (MJO) permit the study of multiscale atmospheric processes associated with non-MJO phenomena and their impacts on the marine boundary layer. Underway analyses that integrate observations and numerical simulations shed light on how air–sea interactions control the ABL and upper-ocean processes.

Stratified Ocean Dynamics in the Arctic: Science and Experiment Plan

Lee, C.M., et al., "Stratified Ocean Dynamics in the Arctic: Science and Experiment Plan," APL-UW TR 1601, Technical Report, Applied Physics Laboratory, University of Washington, Seattle, September 2016, 46pp.

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15 Sep 2016

Vertical and lateral water properties and density structure within the Arctic Ocean are intimately related to the ocean circulation, and have profound consequences for sea ice growth and retreat as well as for propagation of acoustic energy at all scales. Our current understanding of the dynamics governing arctic upper ocean stratification and circulation derives largely from a period when extensive ice cover modulated the oceanic response to atmospheric forcing. Recently, however, there has been significant arctic warming, accompanied by changes in the extent, thickness distribution, and properties of the arctic sea ice cover. The need to understand these changes and their impact on arctic stratification and circulation, sea ice evolution, and the acoustic environment motivate the Office of Naval Research (ONR) Stratified Ocean Dynamics of the Arctic Departmental Research Initiative.

Collaborative observations of boundary currents, water mass variability, and monsoon response in the southern Bay of Bengal

Lee, C.M., S.U.P. Jinadasa, A. Anutaliya, L.R. Centurioni, H.J.S. Fernando, V. Hormann, M. Lankhorst, L. Rainville, U. Send, and H.W. Wijesekera, "Collaborative observations of boundary currents, water mass variability, and monsoon response in the southern Bay of Bengal," Oceanography 29, 102–111, doi:10.5670/oceanog.2016.43, 2016.

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1 Jun 2016

The region surrounding Sri Lanka modulates monsoon-driven exchange between the Bay of Bengal and the Arabian Sea. Here, local circulation impacts the pathways followed by the boundary currents that drive exchange, thereby modulating mixing and water mass transformation. From 2013 to 2016, an international partnership conducted sustained measurements around the periphery of Sri Lanka, with the goal of understanding how circulation and mixing in this critical region modulate exchange between the Bay of Bengal and the Arabian Sea. Observations from satellite remote sensing, surface drifters, gliders, current meter moorings, and Pressure Inverted Echo Sounders capture seasonally reversing monsoon currents off the southern tip of Sri Lanka, trace the wintertime freshwater export pathway of the East India Coastal Current, and document the deflection of currents running along the east coast of Sri Lanka by cyclonic and anticyclonic eddies. Measurements also reveal energetic interleaving, indicative of mixing and stirring associated with these flows. Circulation inferred from satellite remote sensing and drifter tracks sometimes differs from that indicated by in situ sections, pointing to the need for observing systems that employ complementary approaches toward understanding this region.

Global observations of open-ocean mode-1 M2 internal tides

Zhao, Z., M.H. Alford, J.B. Girton, L. Rainville, and H.L. Simmons, "Global observations of open-ocean mode-1 M2 internal tides," J. Phys. Oceanogr., 46, 1657-1684, doi:10.1175/JPO-D-15-0105.1, 2016.

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1 Jun 2016

A global map of open-ocean mode-1 M2 internal tides is constructed using sea-surface height (SSH) measurements from multiple satellite altimeters during 1992–2012, representing a 20-year coherent internal tide field. A two-dimensional plane wave fit method is employed to (1) suppress mesoscale contamination by extracting internal tides with both spatial and temporal coherence, and (2) separately resolve multiple internal tidal waves. Global maps of amplitude, phase, energy and flux of mode-1 M2 internal tides are presented. M2 internal tides are mainly generated over topographic features including continental slopes, mid-ocean ridges and seamounts. Internal tidal beams of 100–300 km width are observed to propagate hundreds to thousands of km. Multi-wave interference of some degree is widespread, due to the M2 internal tide's numerous generation sites and long-range propagation. The M2 internal tide propagates across the critical latitudes for parametric subharmonic instability (28.8°S/N) with little energy loss, consistent with field measurements by MacKinnon et al. (2013). In the eastern Pacific Ocean, the M2 internal tide loses significant energy in propagating across the Equator; in contrast, little energy loss is observed in the equatorial zones of the Atlantic, Indian, and western Pacific oceans. Global integration of the satellite observations yields a total energy of 36 PJ (1 PJ = 1015 J) for the coherent mode-1 M2 internal tide. The satellite observed M2 internal tides compare favorably with field mooring measurements and a global eddy-resolving numerical model.

The impact of multiple layering on internal wave transmission

Ghaemsaidi, S.J., H.V. Dosser, L. Rainville, and T. Peacock, "The impact of multiple layering on internal wave transmission," J. Fluid Mech., 789, 617-629, doi:10.1017/jfm.2015.682, 2016.

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1 Feb 2016

Given the ubiquity of layering in environmental stratifications, an interesting example being double-diffusive staircase structures in the Arctic Ocean, we present the results of a joint theoretical and laboratory experimental study investigating the impact of multiple layering on internal wave propagation. We first present results for a simplified model that demonstrates the non-trivial impact of multiple layering. Thereafter, utilizing a weakly viscous linear model that can handle arbitrary vertical stratifications, we perform a comparison of theory with experiments. We conclude by applying this model to a case study of a staircase stratification profile obtained from the Arctic Ocean, finding a rich landscape of transmission behaviour.

Dynamics of the changing near-inertial internal wave field in the Arctic Ocean

Dosser, H.V., and L. Rainville, "Dynamics of the changing near-inertial internal wave field in the Arctic Ocean," J. Phys. Oceanogr., 46, 395-415, doi:10.1175/JPO-D-15-0056.1, 2016.

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1 Feb 2016

The dynamics of the wind-generated near-inertial internal wave field in the Canada Basin of the Arctic Ocean are investigated using the drifting Ice-Tethered Profiler dataset for the years 2005 to 2014, during a decade when sea ice extent and thickness decreased dramatically. This time series, with nearly 10 years of measurements and broad spatial coverage, is used to quantify a seasonal cycle and interannual trend for internal waves in the Arctic, using estimates of the amplitude of near-inertial waves derived from isopycnal displacements. The internal wave field is found to be most energetic in summer when sea ice is at a minimum, with a second maximum in early winter during the period of maximum wind speed. Amplitude distributions for the near-inertial waves are quantifiably different during summer and winter, due primarily to seasonal changes in sea ice properties that affect how the ice responds to the wind, which can be expressed through the "wind factor" — the ratio of sea ice drift speed to wind speed. A small positive interannual trend in near-inertial wave energy is linked to pronounced sea ice decline during the last decade. Overall variability in the internal wave field increases significantly over the second half of the record, with an increased probability of larger-than-average waves in both summer and winter. This change is linked to an overall increase in variability in the wind factor and sea ice drift speeds, and reflects a shift in year-round sea ice characteristics in the Arctic, with potential implications for dissipation and mixing associated with internal waves.

Characterizing the semidiurnal internal tide off Tasmania using glider data

Boettger, D., R. Robertson, and L. Rainville, "Characterizing the semidiurnal internal tide off Tasmania using glider data," J. Geophys. Res., 120, 3730-3746, doi:10.1002/2015JC010711, 2015.

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1 May 2015

The spatial structure of the semidiurnal internal tide in the vicinity of Tasmania is characterized using temperature and salinity data from Seaglider and Slocum glider deployments. Wavelet analysis of isopycnal displacements measured by the gliders was used to isolate the semidiurnal internal tide, with a solid signal observed both to the east and to the south of Tasmania. The signal south of Tasmania was attributed to local forcing, while that to the east of Tasmania was found to have propagated from the south east to the north west — a result which supports previous studies indicating the presence of an internal tidal beam originating over the Macquarie Ridge, south of New Zealand. Displacement amplitudes were observed to be amplified in the vicinity of the continental slope, with the incoming tidal beam shown to be both reflected and scattered on the continental slope and shelf, and energy transferred to higher modes.

The formation and fate of internal waves in the South China Sea

Alford, M.H., et al., including R.-C. Lien and L. Rainville, "The formation and fate of internal waves in the South China Sea," Nature, 521, 65-69, doi:10.1038/nature14399, 2015.

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29 Apr 2015

Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis1, sediment and pollutant transport2 and acoustic transmission3; they also pose hazards for man-made structures in the ocean4. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking5, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects6, 7. For over a decade, studies8, 9, 10, 11 have targeted the South China Sea, where the oceans’ most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. Here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.

Salinity and temperature balances at the SPURS central mooring during fall and winter

Farrar, J.T., L. Rainville, A.J. Plueddemann, W.S. Kessler, C. Lee, B.A. Hodges, R.W. Schmitt, J.B. Edson, S.C. Riser, C.C. Eriksen, and D.M. Fratantoni, "Salinity and temperature balances at the SPURS central mooring during fall and winter," Oceanography, 28, 56-65, doi:10.5670/oceanog.2015.06, 2015.

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1 Mar 2015

One part of the Salinity Processes in the Upper-ocean Regional Study (SPURS) field campaign focused on understanding the physical processes affecting the evolution of upper-ocean salinity in the region of climatological maximum sea surface salinity in the subtropical North Atlantic (SPURS-1). An upper-ocean salinity budget provides a useful framework for increasing this understanding. The SPURS-1 program included a central heavily instrumented mooring for making accurate measurements of air-sea surface fluxes, as well as other moorings, Argo floats, and gliders that together formed a dense observational array. Data from this array are used to estimate terms in the upper-ocean salinity and heat budgets during the SPURS-1 campaign, with a focus on the first several months (October 2012 to February 2013) when the surface mixed layer was becoming deeper, fresher, and cooler. Specifically, we examine the salinity and temperature balances for an upper-ocean mixed layer, defined as the layer where the density is within 0.4 kg m-3 of its surface value. The gross features of the evolution of upper-ocean salinity and temperature during this fall/winter season are explained by a combination of evaporation and precipitation at the sea surface, horizontal transport of heat and salt by mixed-layer currents, and vertical entrainment of fresher, cooler fluid into the layer as it deepened. While all of these processes were important in the observed seasonal (fall) freshening at this location in the salinity-maximum region, the variability of salinity on monthly-to-intraseasonal time scales resulted primarily from horizontal advection.

Recent Arctic Ocean sea ice loss triggers novel fall phytoplankton blooms

Ardyna, M., M. Babin, M. Gosselin, E. Devred, L. Rainville, and J.-E. Tremblay, "Recent Arctic Ocean sea ice loss triggers novel fall phytoplankton blooms," Geophys. Res. Lett., 41, 6207-6212, doi:10.1002/2014GL061047, 2014.

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16 Sep 2014

Recent receding of the ice pack allows more sunlight to penetrate into the Arctic Ocean, enhancing productivity of a single annual phytoplankton bloom. Increasing river runoff may, however, enhance the yet pronounced upper ocean stratification and prevent any significant wind-driven vertical mixing and upward supply of nutrients, counteracting the additional light available to phytoplankton. Vertical mixing of the upper ocean is the key process that will determine the fate of marine Arctic ecosystems. Here we reveal an unexpected consequence of the Arctic ice loss: regions are now developing a second bloom in the fall, which coincides with delayed freezeup and increased exposure of the sea surface to wind stress. This implies that wind-driven vertical mixing during fall is indeed significant, at least enough to promote further primary production. The Arctic Ocean seems to be experiencing a fundamental shift from a polar to a temperate mode, which is likely to alter the marine ecosystem.

Response of upper ocean currents to Typhoon Fanapi

Hormann, V., L.R. Centurioni, L. Rainville, C.M. Lee, and L.J. Braasch, "Response of upper ocean currents to Typhoon Fanapi," Geophys. Res. Lett., 41, 3995-4003, doi:10.1002/2014GL060317, 2014.

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16 Jun 2014

The response of upper ocean currents to Typhoon Fanapi in fall 2010 was studied using an extensive air-deployed drifter array. Separation of the observations into near-inertial and sub-inertial motions quantified the importance of strong advection by the sub-inertial circulation for the evolution of the cold wake formed by Typhoon Fanapi. The near-inertial currents generated during the storm showed the expected rightward bias, with peak magnitudes of up to 0.6 m/s and an e-folding time of about 4 days for the strong currents within the cold wake. The shear of the near-inertial currents is crucial for the storm-induced cooling and deepening of the mixed layer and such instabilities were here directly observed across the base of th — a dominant process for the wake warming — was found to be noticeably reduced when the near-inertial motions were strongest.

Variations of the North Pacific subtropical mode water from direct observations

Rainville, L., S.R. Jayne, and M.F. Cronin, "Variations of the North Pacific subtropical mode water from direct observations," J. Clim., 27, 2842-2860, doi:10.1175/JCLI-D-13-00227.1, 2014.

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1 Apr 2014

Mooring measurements from the Kuroshio Extension System Study (June 2004–June 2006) and from the ongoing Kuroshio Extension Observatory (June 2004–present) are combined with float measurements of the Argo network to study the variability of the North Pacific Subtropical Mode Water (STMW) across the entire gyre, on time scales from days, to seasons, to a decade. The top of the STMW follows a seasonal cycle, although observations reveal that it primarily varies in discrete steps associated with episodic wind events. The variations of the STMW bottom depth are tightly related to the sea surface height (SSH), reflecting mesoscale eddies and large-scale variations of the Kuroshio Extension and recirculation gyre systems. Using the observed relationship between SSH and STMW, gridded SSH products and in situ estimates from floats are used to construct weekly maps of STMW thickness, providing nonbiased estimates of STMW total volume, annual formation and erosion volumes, and seasonal and interannual variability for the past decade. Year-to-year variations are detected, particularly a significant decrease of STMW volume in 2007–10 primarily attributable to a smaller volume formed. Variability of the heat content in the mode water region is dominated by the seasonal cycle and mesoscale eddies; there is only a weak link to STMW on interannual time scales, and no long-term trends in heat content and STMW thickness between 2002 and 2011 are detected. Weak lagged correlations among air–sea fluxes, oceanic heat content, and STMW thickness are found when averaged over the northwestern Pacific recirculation gyre region.

Near-inertial internal wave field in the Canada basin from ice-tethered profilers

Dosser, H.V., L. Rainville, and J.M. Toole, "Near-inertial internal wave field in the Canada basin from ice-tethered profilers," J. Phys. Oceanogr., 44, 413-426, doi:10.1175/JPO-D-13-0117.1, 2014.

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1 Feb 2014

Salinity and temperature profiles from drifting ice-tethered profilers in the Beaufort gyre region of the Canada Basin are used to characterize and quantify the regional near-inertial internal wave field over one year. Vertical displacements of potential density surfaces from the surface to 750-m depth are tracked from fall 2006 to fall 2007. Because of the time resolution and irregular sampling of the ice-tethered profilers, near-inertial frequency signals are marginally resolved. Complex demodulation is used to determine variations with a time scale of several days in the amplitude and phase of waves at a specified near-inertial frequency. Characteristics and variability of the wave field over the course of the year are investigated quantitatively and related to changes in surface wind forcing and sea ice cover.

Propagation of internal tides generated near Luzon Strait: Observations from autonomous gliders

Rainville, L., C.M. Lee, D.L. Rudnick, and K.-C. Yang, "Propagation of internal tides generated near Luzon Strait: Observations from autonomous gliders," J. Geophys. Res., 118, 4125-4138, doi:10.1002/jgrc.20293, 2013.

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1 Sep 2013

The vertical isopycnal displacements associated with internal waves generated by the barotropic tidal currents in the vicinity of Luzon Strait are estimated using measurements collected by autonomous underwater gliders. Nearly 23,000 profiles from Seagliders and Spray gliders, collected during 29 different missions since 2007, are used to estimate the amplitude and phase of the linear semidiurnal and diurnal internal waves in this energetic region, particularly in the previously poorly sampled area near the eastern ridge and on the Pacific side of Luzon Strait. The mean and variability of the internal wave field in the upper 1000 m of the water column are described. The phase progression of internal waves as they propagate away from their generation sites is captured directly. The glider-based observations are used to map the mode-1 semidiurnal and diurnal internal wave fields, providing the baroclinic energy flux over a roughly 600 km x 800 km region based strictly on in situ observations.

Observations of the cold wake of Typhoon Fanapi (2010)

Mrvaljevic, R.K., P.G. Black, L.R. Centurioni, Y.-T. Chang, E.A. D'Asaro, S.R. Jayne, C.M. Lee, R.-C. Lien, I.-I. Lin, J. Morzel, P.P. Niiler, L. Rainville, and T.B. Sanford, "Observations of the cold wake of Typhoon Fanapi (2010)," Geophys. Res. Lett., 40, 316-321, doi:10.1002/grl.50096, 2013.

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28 Jan 2013

Several tens of thousands of temperature profiles are used to investigate the thermal evolution of the cold wake of Typhoon Fanapi, 2010. Typhoon Fanapi formed a cold wake in the Western North Pacific Ocean on 18 September characterized by a mixed layer that was >2.5°C cooler than surrounding water, and extending to >80 m, twice as deep as the pre-existing mixed layer. The initial cold wake became capped after 4 days as a warm, thin surface layer formed. The thickness of the capped wake, defined as the 26°C to 27°C layer, decreased, approaching the background thickness of this layer with an e-folding time of 23 days, almost twice the e-folding lifetime of the Sea Surface Temperature (SST) cold wake (12 days). The wake was advected several hundreds of kilometers from the storm track by a pre-existing mesoscale eddy. The observations reveal new intricacies of cold wake evolution and demonstrate the challenges of describing the thermal structure of the upper ocean using sea surface information alone.

Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation Gyre

Cronin, M.F., N.A. Bond, J.T. Farrar, H. Ichikawa, S.R. Jayne, Y. Kawai, M. Konda, B. Qiu, L. Rainville, and H. Tomita, "Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation Gyre," Deep-Sea Res. II, 85, 62-74, doi:10.1016/j.dsr2.2012.07.018, 2013.

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1 Jan 2013

Data from the Kuroshio Extension Observatory (KEO) surface mooring are used to analyze the balance of processes affecting the upper ocean heat content and surface mixed layer temperature variations in the Recirculation Gyre (RG) south of the Kuroshio Extension (KE). Cold and dry air blowing across the KE and its warm RG during winter cause very large heat fluxes out of the ocean that result in the erosion of the seasonal thermocline in the RG. Some of this heat is replenished through horizontal heat advection, which may enable the seasonal thermocline to begin restratifying while the net surface heat flux is still acting to cool the upper ocean. Once the surface heat flux begins warming the ocean, restratification occurs rapidly due to the low thermal inertia of the shallow mixed layer depth. Enhanced diffusive mixing below the mixed layer tends to transfer some of the mixed layer heat downward, eroding and potentially modifying sequestered subtropical mode water and even the deeper waters of the main thermocline during winter. Diffusivity at the base of the mixed layer, estimated from the residual of the mixed layer temperature balance, is roughly 3x10-4 m2/s during the summer and up to two orders of magnitude larger during winter. The enhanced diffusivities appear to be due to large inertial shear generated by wind events associated with winter storms and summer tropical cyclones. The diffusivity's seasonality is likely due to seasonal variations in stratification just below the mixed layer depth, which is large during the summer when the seasonal thermocline is fully developed and low during the winter when the mixed layer extends to the top of the thermocline.

Marginal Ice Zone (MIZ) Program: Science and Experiment Plan

Lee, C.M., et al., "Marginal Ice Zone (MIZ) Program: Science and Experiment Plan," APL-UW TR 1201, Technical Report, Applied Physics Laboratory, University of Washington, Seattle, October 2012, 48 pp.

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9 Oct 2012

The Marginal Ice Zone (MIZ) intensive field program will employ an array of cutting-edge autonomous platforms to characterize the processes that govern Beaufort Sea MIZ evolution from initial breakup and MIZ formation though the course of the summertime sea ice retreat. Instruments will be deployed on and under the ice prior to initial formation of the MIZ along the Alaska coast, and will continue sampling from open water, across the MIZ, and into full ice cover, as the ice edge retreats northward through the summer. The flexible nature of ice-mounted and mobile, autonomous oceanographic platforms (e.g., gliders and floats) facilitates access to regions of both full ice cover and riskier MIZ regions. This approach exploits the extended endurance of modern autonomous platforms to maintain a persistent presence throughout the entire northward retreat. It also takes advantage of the inherent scalability of these instruments to sample over a broad range of spatial and temporal scales.

Mesoscale bio-physical interactions between the Agulhas Current and the Agulhas Bank, South Africa

Jackson, J.M., L. Rainville, M.J. Roberts, C.D. McQuaid, and J.R.E. Lutjeharms, "Mesoscale bio-physical interactions between the Agulhas Current and the Agulhas Bank, South Africa," Cont. Shelf. Res., 49, 10-24, doi:10.1016/j.csr.2012.09.005, 2012.

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1 Oct 2012

The Agulhas Current on the east coast of South Africa is a major western boundary current that exchanges heat and salt between the Indian and South Atlantic Oceans. The current retroflects as it deflects away from the African continent at the southern tip of the Agulhas Bank, a biologically productive extension of the continental shelf south of the South African coast. The less energetic Benguela Current borders the Agulhas Bank to the west. Little is known about mesoscale interactions between the Agulhas Current and the shelf waters of the Agulhas Bank or how these processes influence the biology of the bank. In this study, physical and biological data collected during a dedicated cruise in September 2010 allowed the identification of several mesoscale features that indicate a strong effect of the current on the bank, including a Natal Pulse that forced the Agulhas Current onto the Agulhas Bank. While on the bank itself, the current entrained particles that were then transported offshore. We also found evidence of upwelling on the southeast edge of the Agulhas Bank, which is thought to be a source of water for a cold ridge that characterizes the eastern region of the bank. Large fluctuations of the thermocline, consistent with internal waves, were observed inshore of the Agulhas Current, with high phytoplankton concentrations at their crests. We suggest that this is a physical effect, with doming of the waves concentrating plankton at their crests, thereby creating episodic biological hotspots.

Semi-diurnal baroclinic wave momentum fluxes at Kaena Ridge, Hawaii

Pinkel, R., L. Rainville, and J. Klymak, "Semi-diurnal baroclinic wave momentum fluxes at Kaena Ridge, Hawaii," J. Phys. Ocean., 42, 1249-1269, doi: 10.1175/JPO-D-11-0124.1, 2012.

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27 Apr 2012

Kaena Ridge, Hawaii is a site of energetic conversion of the semi-diurnal barotropic tide. Diffuse baroclinic wave beams emanate from the critical-slope regions near the ridge crest, directed upward and southward from the north flank of the ridge, upward and northward from the south flank. Here we attempt to quantify the momentum fluxes associated with generation at the Ridge. Continuous vertical profiles of density and velocity from 80–800 m were obtained from the Research Platform FLIP over the southern edge of the ridge, as an aspect of the Hawaii Ocean Mixing Experiment. Data are used to estimate the Reynolds stress, Eulerian buoyancy flux, and the combined Eliassen-Palm Flux in the semi-diurnal band. An upward-southward stress maximum of ~ 0.5 10-4 m2 s-2 appears at depths 300–500 m, generally consistent with beam-like behavior. A strong off-ridge buoyancy flux (~ 0.3 10-4 m2 s-3) combines with large along-ridge Reynolds stresses to form an Eliassen Palm flux whose along-ridge and across-ridge magnitudes are comparable. The stress azimuth rotates clockwise with increasing altitude above the ridge crest. The principal upward-southward beam is found to be at depths 100–300 m shallower than are predicted by an analytic 2-dimensional model and a 3-D numerical simulation. This discrepancy is consistent with previous observations of the baroclinic energy flux. If these observed tidal momentum fluxes were to diverge in a 100-m thick near-surface layer, the forcing would be comparable to a moderate wind stress. Pronounced lateral gradients of baroclinic tidal stresses can be expected offshore of Hawaiian topography.

Typhoon-ocean interaction in the western North Pacific: Part 1

D'Asaro, E., P. Black, L. Centurioni, P. Harr, S. Jayne, I.-I Lin, C. Lee, J. Morzel, R. Mrvaljevic, P.P. Niiler, L. Rainville, T. Sanford, and T.Y. Tang, "Typhoon-ocean interaction in the western North Pacific: Part 1," Oceanography, 24, 24-31, doi:10.5670/oceanog.2011.91, 2011

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5 Dec 2011

The application of new technologies has allowed oceanographers and meteorologists to study the ocean beneath typhoons in detail. Recent studies in the western Pacific Ocean reveal new insights into the influence of the ocean on typhoon intensity.

Energy flux and dissipation in Luzon Strait: Two tales of two ridges

Alford, M.H., J.A. MacKinnon, J.D. Nash, H. Simmons, A. Pickering, J.M. Klymak, R. Pinkel, O. Sun, L. Rainville, R. Musgrave, T. Beitzel, K.-H. Fu, and C.-W. Lu, "Energy flux and dissipation in Luzon Strait: Two tales of two ridges," J. Phys. Oceanogr., 41, 2211-2222, 2011.

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1 Nov 2011

Internal tide generation, propagation, and dissipation are investigated in Luzon Strait, a system of two quasi-parallel ridges situated between Taiwan and the Philippines. Two profiling moorings deployed for about 20 days and a set of nineteen 36-h lowered ADCP–CTD time series stations allowed separate measurement of diurnal and semidiurnal internal tide signals. Measurements were concentrated on a northern line, where the ridge spacing was approximately equal to the mode-1 wavelength for semidiurnal motions, and a southern line, where the spacing was approximately two-thirds that. The authors contrast the two sites to emphasize the potential importance of resonance between generation sites. Throughout Luzon Strait, baroclinic energy, energy fluxes, and turbulent dissipation were some of the strongest ever measured. Peak-to-peak baroclinic velocity and vertical displacements often exceeded 2 m s-1 and 300 m, respectively. Energy fluxes exceeding 60 kW m-1 were measured at spring tide at the western end of the southern line. On the northern line, where the western ridge generates appreciable eastward-moving signals, net energy flux between the ridges was much smaller, exhibiting a nearly standing wave pattern. Overturns tens to hundreds of meters high were observed at almost all stations. Associated dissipation was elevated in the bottom 500—1000 m but was strongest by far atop the western ridge on the northern line, where >500-m overturns resulted in dissipation exceeding 2 x 10-6 W kg-1 (implying diapycnal diffusivity K%u03C1 > 0.2 m2 s%u22121). Integrated dissipation at this location is comparable to conversion and flux divergence terms in the energy budget. The authors speculate that resonance between the two ridges may partly explain the energetic motions and heightened dissipation.

Impact of wind-driven mixing in the Arctic Ocean

Rainville, L., C.M. Lee, and R.A. Woodgate, "Impact of wind-driven mixing in the Arctic Ocean," Oceanography 24, 136-145, doi:10.5670/oceanog.2011.65, 2011.

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1 Sep 2011

The Arctic Ocean traditionally has been described as an ocean with low variability and weak turbulence levels. Many years of observations from ice camps and ice-based instruments have shown that the sea ice cover effectively isolates the water column from direct wind forcing and damps existing motions, resulting in relatively small upper-ocean variability and an internal wave field that is much weaker than at lower latitudes. Under the ice, direct and indirect estimates across the Arctic basins suggest that turbulent mixing does not play a significant role in the general distribution of oceanic properties and the evolution of Arctic water masses. However, during ice-free periods, the wind generates inertial motions and internal waves, and contributes to deepening of the mixed layer both on the shelves and over the deep basins - as at lower latitudes. Through their associated vertical mixing, these motions can alter the distribution of properties in the water column. With an increasing fraction of the Arctic Ocean becoming ice-free in summer and in fall, there is a crucial need for a better understanding of the impact of direct wind forcing on the Arctic Ocean.

Enhanced turbulence and energy dissipation at ocean fronts

D'Asaro, E., C. Lee, L. Rainville, L. Thomas, and R. Harcourt, "Enhanced turbulence and energy dissipation at ocean fronts," Science, 332, 318-322, doi:0.1126/science.1201515, 2011.

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15 Apr 2011

The ocean surface boundary layer mediates air-sea exchange. In the classical paradigm and in current climate models, its turbulence is driven by atmospheric forcing. Observations at a 1-km-wide front within the Kuroshio found the rate of energy dissipation within the boundary layer to be enhanced by 10 to 20 times, suggesting that the front not the atmospheric forcing supplied the energy for the turbulence. The data quantitatively support the hypothesis that winds aligned with the frontal velocity catalyzed a release of energy from the front to the turbulence. The resulting boundary layer is stratified, in contrast to the classically well-mixed layer. These effects will be strongest at the intense fronts found in the Kuroshio, Gulf Stream, and Antarctic Circumpolar Current, key players in the climate system.

Distribution of deep near-inertial waves observed in the Kuroshio Extension

Park, J.-H., K.A. Donohue, D.R. Watts, and L. Rainville, "Distribution of deep near-inertial waves observed in the Kuroshio Extension," J. Oceanogr., 66, 709-717, doi:10.1007/s10872-010-0058-0, 2010.

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1 Oct 2010

The distribution of deep near-inertial waves (NIWs) is investigated using data mainly from an array of 46 near-bottom acoustic current meter sensors spanning a 600 km x 600 km region as part of the Kuroshio Extension System Study during 2004–2006. The deep NIW distribution is interpreted in the context of both upper-layer and near-bottom mapped circulations. The wintertime-mean mixed-layer NIW energy input, modeled from observed wind stress, has the same range of values north and south of the Kuroshio Extension in this region. Yet, the wintertime-mean deep NIW energy distribution reveals a sharp factor-of-5 decrease from north to south of the Kuroshio jet. This direct observational evidence shows that the Kuroshio Extension blocks the equatorward propagation of NIWs. The NIW energy that does reach the sea floor within the subset of wintertime observations in the subtropical gyre arrives with patchy spatial and temporal distribution. Elevated NIW energy in deep water is associated with anticyclones in the deep barotropic flow and unassociated with upper layer eddies.

Interference pattern and propagation of the M2 internal tide south of the Hawaiian Ridge

Rainville, L., T.M.S. Johnston, G.S. Carter, M.A. Merrifield, R. Pinkel, P.F. Worcester, and B.D. Dushaw, "Interference pattern and propagation of the M2 internal tide south of the Hawaiian Ridge," J. Phys. Oceanogr., 40, 311-325, 2010.

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1 Feb 2010

Most of the M2 internal tide energy generated at the Hawaiian Ridge radiates away in modes 1 and 2, but direct observation of these propagating waves is complicated by the complexity of the bathymetry at the generation region and by the presence of interference patterns.

Observations from satellite altimetry, a tomographic array, and the R/P FLIP taken during the Farfield Program of the Hawaiian Ocean Mixing Experiment (HOME) are found to be in good agreement with the output of a high-resolution primitive equation model, simulating the generation and propagation of internal tides. The model shows that different modes are generated with different amplitudes along complex topography. Multiple sources produce internal tides that sum constructively and destructively as they propagate. The major generation sites can be identified using a simplified 2D idealized knife-edge ridge model. Four line sources located on the Hawaiian Ridge reproduce the interference pattern of sea surface height and energy flux density fields from the numerical model for modes 1 and 2. Waves from multiple sources and their interference pattern have to be taken into account to correctly interpret in situ observations and satellite altimetry.

Observations of internal wave generation in the seasonally ice-free Arctic

Rainville, L., and R.A. Woodgate, "Observations of internal wave generation in the seasonally ice-free Arctic," Geophys. Res. Lett., 36, 10.1029/2009GL041291, 2009.

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2 Dec 2009

The Arctic is generally considered a low energy ocean. Using mooring data from the northern Chukchi Sea, we confirm that this is mainly because of sea-ice impeding input of wind energy into the ocean. When sea-ice is present, even strong storms do not induce significant oceanic response. However, during ice-free seasons, local storms drive strong inertial currents (>20 cm/s) that propagate throughout the water column and significantly deepen the surface mixed layer. The large vertical shear associated with summer inertial motions suggests a dominant role for localized and seasonal vertical mixing in Arctic Ocean dynamics. Our results imply that recent extensive summer sea-ice retreat will lead to significantly increased internal wave generation especially over the shelves and also possibly over deep waters. This internal wave activity will likely dramatically increase upper-layer mixing in large areas of the previously quiescent Arctic, with important ramifications for ecosystems and ocean dynamics.

The Kuroshio Extension and its recirculation gyre

Jayne, S.R. et al., including L. Rainville, "The Kuroshio Extension and its recirculation gyre," Deep-Sea Res. I, 56, 2088-2099, doi:10.1016/j.dsr.2009.08.006, 2009.

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1 Dec 2009

This paper reports on the strength and structure of the Kuroshio Extension and its recirculation gyres. In the time average, quasi-permanent recirculation gyres are found to the north and south of the Kuroshio Extension jet. The characteristics of these recirculations gyres are determined from the combined observations from the Kuroshio Extension System Study (KESS) field program (June 2004–June 2006) and include current meters, pressure and current recording inverted echo sounders, and subsurface floats. The position and strength of the recirculation gyres simulated by a high-resolution numerical model are found to be consistent with the observations. The circulation pattern that is revealed is of a complex system of multiple recirculation gyres that are embedded in the crests and troughs of the quasi-permanent meanders of the Kuroshio Extension. At the location of the KESS array, the Kuroshio Extension jet and its recirculation gyres transport of about 114 Sv. This represents a 2.7-fold increase in the transport of the current compared to the Kuroshio's transport at Cape Ashizuri before it separates from the coast and flows eastward into the open ocean. This enhancement in the current's transport comes from the development of the flanking recirculation gyres. Estimates from an array of inverted echo sounders and a high-resolution ocean general circulation model are of similar magnitude.

Mixing across the Arctic Ocean: Microstructure observations during the Beringia 2005 Expedition

Rainville, L., and P. Winsor, "Mixing across the Arctic Ocean: Microstructure observations during the Beringia 2005 Expedition," Geophys. Res. Lett., 35, doi:10.1029/2008GL033532, 2008.

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30 Apr 2008

Turbulent-scale temperature and conductivity were measured during the pan-arctic Beringia 2005 Expedition. The rates of dissipation of thermal variance and diapycnal diffusivities are calculated along a section from Alaska to the North Pole, across deep flat basins (Canada and Makarov Basins) and steep ridges (Alpha-Mendeleev and Lomonosov Ridges). The mixing rates are observed to be small relative to lower latitudes but also remarkably non-uniform. Relatively elevated turbulence is found over deep topography, confirming the dominant role of bottom-generated internal waves. Measured patterns of mixing in the Arctic are also associated with other mechanisms, such as double-diffusive structures and deep overflows. A better knowledge of the distribution of mixing is essential to understand the dynamics of the changing Arctic environment.


Temperature Microstructure Instrument Controller Logger

Record of Invention Number: 47906

Luc Rainville, Jason Gobat, Adam Huxtable, Geoff Shilling


6 Dec 2016

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