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John Mickett

Senior Oceanographer

Email

jmickett@apl.washington.edu

Phone

206-897-1795

Department Affiliation

Ocean Physics

Projects

Submesoscale Mixed-Layer Dynamics at a Mid-Latitude Oceanic Front

SMILE: the Submesoscale MIxed-Layer Eddies experiment

More Info

1 Mar 2017

This experiment is aimed at increasing our understanding of the role of lateral processes in mixed-layer dynamics through a series of ship surveys and Lagrangian array deployments. Instrument deployments and surveys target the upper ocean's adjustment to winter atmospheric forcing events in the North Pacific subtropical front, roughly 800 km north of Hawaii.

This study will improve understanding of 1–10-km scale lateral processes in three-dimensional mixed-layer dynamics in a region of above-average atmospheric forcing, typical mid-ocean mesoscale advection and straining, and typical submesoscale activity. The results will improve the physical basis of mixed-layer parameterizations, leading to better model predictions of air-sea fluxes, gas transfer, and biological productivity.

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

Samoan Passage Abyssal Mixing

The Samoan Passage, 5500 m beneath the sea surface, is one of the "choke points" in the abyssal circulation. A veritable river of Antarctic Bottom water flows through it on its way into the North Pacific. As it enters the constriction, substantial turbulence, hydraulic processes and internal waves must occur, which modify the water. The overall goal is to understand these deep processes and the way they impact the flow, and to develop a strategy for eventually monitoring the flow through the Passage.

27 Sep 2011

More Projects

Videos

Environmental Sample Processor: A Sentry for Toxic Algal Blooms off the Washington Coast

An undersea robot that measures harmful algal species has been deployed by APL, UW, and NOAA researchers off the Washington coast near La Push. Algal bloom toxicity data are relayed to shore in near-real time and displayed through the NANOOS visualization system. The Environmental Sample Processor, or ESP, is taking measurements near the Juan de Fuca eddy, which is a known incubation site for toxic blooms that often travel toward coastal beaches, threatening fisheries and human health.

22 Jun 2016

ORCA Tracks the 'Blob'

A 'blob' of very warm surface water developed in the northeastern Pacific Ocean in 2014–2015 and its influence extended to the inland waters of Puget Sound throughout the summer of 2015. The unprecedented conditions were tracked by the ORCA (Oceanic Remote Chemical Analyzer) buoy network — an array of six heavily instrumented moored buoys in the Sound. ORCA data provided constant monitoring of evolving conditions and allowed scientists to warn of possible fish kill events in the oxygen-starved waters of Hood Canal well in advance.

The ORCA network is maintained by a partnership among APL-UW, the UW College of the Environment, and the UW School of Oceanography.

3 Nov 2015

ArcticMix 2015

APL-UW physical oceanographers John Mickett and Mike Gregg joined SIO colleagues during September 2015 in the Beaufort Sea aboard the R/V Sikuliaq to measure upper ocean mixing that billows heat from depth to the surface. These mixing dynamics may be an important factor in hastening sea ice melt during summer and delaying freeze-up in the fall.

14 Oct 2015

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NEMO Deployment off the Washington Coast 2015

NEMO is the Northwest Enhanced Moored Observatory. The two advanced moorings located in water about 100 m deep off the Washington coast and a repeating Seaglider transect over the continental shelf have been collecting atmospheric and oceanographic data for over five years.

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15 Jul 2015

In 2015 pH/CO2 sensors were placed on the moorning line. NOAA and other research teams have been measuring pCO2 and pH at the sea surface, but this is the first placement of sensors at depth in the region. These new data streams will increase the perspective of real time monitoring and inform ongoing research on ocean acidification.

NEMO Deployment and Shelf Science Cruise

The primary purpose of the cruise is to deploy the NEMO (Northwest Enhanced Moored Observatory) moorings off the Washington coast in water about 100 m deep. While at sea, the team will also conduct science experiments to detect and track non-linear internal waves (NLIWs) traveling across the continental shelf break. Surveys with an echo sounder and the towed body SWIMS will be run from the shelf break toward the mooring location as well as in the Juan de Fuca Canyon.

16 Apr 2013

Wave Chasers: Deep Flows Through the Samoan Passage

The 'Wave Chasers' research team cruised the South Pacific Ocean to study the Samoan Passage — a 5500-m deep choke point that Antarctic bottom water must flow through on its way to the North Pacific. Three movies chronicle the expedition's motivations & methods, the fun of crushing objects under the pressures of the abyssal ocean, and the cultural exchanges with Samoans on Upolu Island.

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22 Feb 2012

"Instruments & Measurements," movie #1, explains the motivation and experimental design to study Antarctic bottom water as it flows through the constriction of the Samoan Passage. The flow is modified by substantial turbulence, hydraulic processes, and internal waves.

Movie #2, "Crush Cam," documents how Oceanographers Matthew Alford and John Mickett are always looking for better ways to share scientific research with the public. They came up with this "Crush Cam." It's a video camera mounted to the instrument package that is lower from the ship and the sea surface to varying depths in the Samoan Passage — it's a way to video objects under extreme pressure.

The third movie, "Cultural Exchanges," follows the Wave Chasers as they visit the village of LufiLufi on the north coast of Upolu Island.

Publications

2000-present and while at APL-UW

Warming and weakening of the abyssal flow through Samoan Passage

Voet, G., M.H. Alford, J.B. Girton, G.S. Carter, J.B. Mickett, and J.M. Klymak, "Warming and weakening of the abyssal flow through Samoan Passage," J. Phys. Oceanogr., 46, 2389–2401, doi:10.1175/JPO-D-16-0063.1, 2016.

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1 Aug 2016

The abyssal flow of water through the Samoan Passage accounts for the majority of the bottom water renewal in the North Pacific, thereby making it an important element of the meridional overturning circulation. Here the authors report recent measurements of the flow of dense waters of Antarctic and North Atlantic origin through the Samoan Passage. A 15-month long moored time series of velocity and temperature of the abyssal flow was recorded between 2012 and 2013. This allows for an update of the only prior volume transport time series from the Samoan Passage from WOCE moored measurements between 1992 and 1994. While highly variable on multiple time scales, the overall pattern of the abyssal flow through the Samoan Passage was remarkably steady. The time-mean northward volume transport of about 5.4 Sv (1 Sv = 106 m3 s−1) in 2012/13 was reduced compared to 6.0 Sv measured between 1992 and 1994. This volume transport reduction is significant within 68% confidence limits (±0.4 Sv) but not at 95% confidence limits (±0.6 Sv). In agreement with recent studies of the abyssal Pacific, the bottom flow through the Samoan Passage warmed significantly on average by 1 x 10−3°C yr−1 over the past two decades, as observed both in moored and shipboard hydrographic observations. While the warming reflects the recently observed increasing role of the deep oceans for heat uptake, decreasing flow through Samoan Passage may indicate a future weakening of this trend for the abyssal North Pacific.

A tale of two spicy seas

MacKinnon, J.A., and 18 others, including J.B. Mickett, "A tale of two spicy seas," Oceanography 29, 50–61, doi:10.5670/oceanog.2016.38, 2016.

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1 Jun 2016

Upper-ocean turbulent heat fluxes in the Bay of Bengal and the Arctic Ocean drive regional monsoons and sea ice melt, respectively, important issues of societal interest. In both cases, accurate prediction of these heat transports depends on proper representation of the small-scale structure of vertical stratification, which in turn is created by a host of complex submesoscale processes. Though half a world apart and having dramatically different temperatures, there are surprising similarities between the two: both have (1) very fresh surface layers that are largely decoupled from the ocean below by a sharp halocline barrier, (2) evidence of interleaving lateral and vertical gradients that set upper-ocean stratification, and (3) vertical turbulent heat fluxes within the upper ocean that respond sensitively to these structures. However, there are clear differences in each ocean’s horizontal scales of variability, suggesting that despite similar background states, the sharpening and evolution of mesoscale gradients at convergence zones plays out quite differently. Here, we conduct a qualitative and statistical comparison of these two seas, with the goal of bringing to light fundamental underlying dynamics that will hopefully improve the accuracy of forecast models in both parts of the world.

Pathways, volume transport, and mixing of abyssal water in the Samoan Passage

Voet, G., J.B. Girton, M.H. Alford, G.S. Carter, J.M. Klymak, and J.B. Mickett, "Pathways, volume transport, and mixing of abyssal water in the Samoan Passage," J. Phys. Oceanogr., 45, 562-588, doi:10.1175/JPO-D-14-0096.1, 2015.

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1 Feb 2015

The flow of dense water through the Samoan Passage accounts for the major part of the bottom water renewal in the North Pacific and is thus an important element of the Pacific meridional overturning circulation. A recent set of highly resolved measurements used CTD/LADCP, a microstructure profiler, and moorings to constrain the complex pathways and variability of the abyssal flow. Volume transport estimates for the dense northward current at several sections across the passage, calculated using direct velocity measurements from LADCPs, range from 3.9 x 106 to 6.0 x 106 ± 1 x 106 m3 s-1. The deep channel to the east and shallower pathways to the west carried about equal amounts of this volume transport, with the densest water flowing along the main eastern channel. Turbulent dissipation rates estimated from Thorpe scales and direct microstructure agree to within a factor of 2 and provide a region-averaged value of O(10-8) W kg-1 for layers colder than 0.8°C. Associated diapycnal diffusivities and downward turbulent heat fluxes are about 5 x 10-3 m2 s-1 and O(10) W m-2, respectively. However, heat budgets suggest heat fluxes 2–6 times greater. In the vicinity of one of the major sills of the passage, highly resolved Thorpe-inferred diffusivity and heat flux were over 10 times larger than the region-averaged values, suggesting the mismatch is likely due to undersampled mixing hotspots.

More Publications

Characteristics, generation and mass transport of nonlinear internal waves on the Washington continental shelf

Zhang, S., M.H. Alford, and J.B. Mickett, "Characteristics, generation and mass transport of nonlinear internal waves on the Washington continental shelf," J. Geophys. Res., 120, 741-758, do:10.1002/2014JC010393, 2015.

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1 Feb 2015

As a step toward better understanding the generation of nonlinear internal waves (NLIWs) on continental shelves and the factors determining their morphology, amplitude and propagation, we analyze more than 1500 NLIWs detected on the Washington (WA) continental shelf using four summer/fall time series of temperature and velocity measurements from a surface mooring deployed in 100 m of water. Propagating onshore toward the northeast, these NLIWs take a variety of forms, including internal solitary waves, solitary wave trains and bores. Nearly all are mode-1 depression waves that arrive semidiurnally along with the internal tide. The NLIW energy flux is correlated with the internal tide energy flux but not the local barotropic forcing, implying that the observed NLIWs arise primarily from shoaling remotely generated internal tides rather than local generation. Estimated onshore transport by the waves can equal or exceed offshore Ekman transport, suggesting the waves may play an important role in the mass balance on the continental shelf.

Turbulent mixing and hydraulic control of abyssal water in the Samoan Passage

Alford, M.H., J.B. Girton, G. Voet, G.S. Carter, J.B. Mickett, and J.M. Klymak, "Turbulent mixing and hydraulic control of abyssal water in the Samoan Passage," Geophys. Res. Lett., 40, 4668-4674, doi:10.1002/grl.50684, 2013.

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16 Sep 2013

We report the first direct turbulence observations in the Samoan Passage (SP), a 40-km wide notch in the South Pacific bathymetry through which flows most of the water supplying the North Pacific abyssal circulation. The observed turbulence is 1000 to 10,000 times typical abyssal levels — strong enough to completely mix away the densest water entering the passage — confirming inferences from previous coarser temperature and salinity sections. Accompanying towed measurements of velocity and temperature with horizontal resolution of about 250 m indicate the dominant processes responsible for the turbulence. Specifically, the flow accelerates substantially at the primary sill within the passage, reaching speeds as great as 0.55 m s-1. A strong hydraulic response is seen, with layers first rising to clear the sill and then plunging hundreds of meters downward. Turbulence results from high shear at the interface above the densest fluid as it descends and from hydraulic jumps that form downstream of the sill. In addition to the primary sill, other locations along the multiple interconnected channels through the Samoan Passage also have an effect on the mixing of the dense water. In fact, quite different hydraulic responses and turbulence levels are observed at seafloor features separated laterally by a few kilometers, suggesting that abyssal mixing depends sensitively on bathymetric details on small scales.

Internal waves on the Washington continental shelf

Alford, M.H., J.B. Mickett, S. Zhang, P. MacCready, Z. Zhao, and J. Newton, "Internal waves on the Washington continental shelf," Oceanography, 25, 66-79, doi:10.5670/oceanog.2012.43, 2012.

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1 Jun 2012

The low-frequency oceanography of the Washington continental shelf has been studied in great detail over the last several decades owing in part to its high productivity but relatively weak upwelling winds compared to other systems. Interestingly, though many internal wave-resolving measurements have been made, there have been no reports on the region's internal wave climate and the possible feedbacks between internal waves and lower-frequency processes. This paper reports observations over two summers obtained from a new observing system of two moorings and a glider on the Washington continental shelf, with a focus on internal waves and their relationships to lower-frequency currents, stratification, dissolved oxygen, and nutrient distributions. We observe a rich, variable internal wave field that appears to be modulated in part by a coastal jet and its response to the region's frequent wind reversals. The internal wave spectral level at intermediate frequencies is consistent with the model spectrum of Levine (2002) developed for continental shelves. Superimposed on this continuum are (1) a strong but highly temporally variable semidiurnal internal tide field and (2) an energetic field of high-frequency nonlinear internal waves (NLIWs). Mean semidiurnal energy flux is about 80 W m-1 to the north-northeast. The onshore direction of the flux and its lack of a strong spring/neap cycle suggest it is at least partly generated remotely. Nonlinear wave amplitudes reach 38 m in 100 m of water, making them among the strongest observed on continental shelves of similar depth. They often occur each 12.4 hours, clearly linking them to the tide. Like the internal tide energy flux, the NLIWs are also directed toward the north-northeast. However, their phasing is not constant with respect to either the baroclinic or barotropic currents, and their amplitude is uncorrelated with either internal-tide energy flux or barotropic tidal forcing, suggesting substantial modulation by the low-frequency currents and stratification.

The Northwest Association of Networked Ocean Observing Systems and opportunities for acoustical applications

Newton, J., M. Alford, J. Mickett, J. Payne, and F. Stahr, "The Northwest Association of Networked Ocean Observing Systems and opportunities for acoustical applications," J. Acoust. Soc. Am., 129, 2371, doi:10.1121/1.3587676, 2011.

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1 Apr 2011

The successful use of SOSUS to track broad-scale occurrence patterns in whale calls during the second half of the 20th century fostered the development of autonomous recorders that can be deployed virtually anywhere in the world ocean. Over the past decade, data from these recorders have provided dramatic insights to marine mammal ecology. Patterns of call reception have demonstrated the near year-round occurrence of some baleen whale species in Arctic and Antarctic waters, a discovery that challenges long-held assumptions about the phenology of seasonal migrations. Integration of year-long calling records with physical oceanographic measures at mooring-based ocean observatories provides a means to include large whales in ecosystem-based models. The reception of anthropogenic sounds on nearly all recorders, whether deployed in coastal or remote areas, emphasizes the need to develop regional "soundscapes" based upon integrative sampling and analytical protocols. Examples from several long-term research programs will be provided as the basis for the strong assertion that passive acoustic observation of marine mammals is a vital component of any ocean observing system. Opportunities for future collaborations and the challenges of data management and access will be discussed.

Resonant forcing of mixed layer inertial motions by atmospheric easterly waves in the northeast tropical Pacific

Mickett, J.B., Y.L. Serra, M.F. Cronin, and M.H. Alford, "Resonant forcing of mixed layer inertial motions by atmospheric easterly waves in the northeast tropical Pacific," J. Phys. Oceanogr., 40, 401-416, 2010.

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1 Feb 2010

Westward-propagating atmospheric easterly waves contribute to much of the variability of the low-level wind fields within the northeast tropical Pacific. With the dominant period of these waves (3–5 days) close to the local inertial period (2.4 days at 12 deg N to 5.7 days at 5 deg N), there is the expectation that the associated winds may resonantly force mixed layer inertial motions in this region. The authors test this hypothesis using a simple slab model and roughly 4 1/2 yr of wind data from four NOAA Tropical Atmosphere Ocean/Eastern Pacific Investigation of Climate Processes (TAO/EPIC) buoys along 95 deg W at 12, 10, 8, and 5 deg N. The degree of resonance is determined by comparing model simulations using observed wind stress with simulations forced with reversed-rotation wind stress.

Results strongly indicate that Pacific easterly waves (PEWs) resonantly force inertial motions in the region. This resonance shows both significant seasonality and latitudinal dependence that appears to be related to the meridional position and intensity of the PEWs. North of the zonal axis of the mean track of the PEWs, the low-level winds associated with the waves rotate predominantly clockwise with time and resonantly force mixed layer inertial motions. South of this axis, the winds rotate counterclockwise, resulting in dissonant (antiresonant) forcing. As this axis migrates annually from about 4 deg N during the boreal winter/spring to a maximum northerly position of about 8–10 deg N in the late boreal summer/early fall, the region of strongest resonance follows, consistently remaining to its north. Model output suggests that resonant forcing results in roughly 10–25% greater net annual flux of kinetic energy from the wind to mixed layer inertial motions than in neutral or nonresonant conditions. This finding has strong implications for mixed layer properties, air-sea coupling, and the generation of near-inertial internal waves.

Upper ocean heat and freshwater budgets in the eastern Pacific warm pool

Wijesekera, H.W., D.L. Rudnick, C.A. Paulson, S.D. Pierce, W.S. Pegau, J. Mickett, and M.C. Gregg, "Upper ocean heat and freshwater budgets in the eastern Pacific warm pool," J. Geophys. Res., 110, 10.1029/2004JC002511, 2005

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11 Aug 2005

This study focuses on upper ocean budgets of heat and freshwater, which yield estimates of net surface heat flux and rainfall minus evaporation. The budgets are based on a 19 day ship survey conducted as part of the Eastern Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System 2001 in September 2001. Underway measurements included temperature and salinity sections from an undulating platform, SeaSoar, and horizontal currents from an acoustic Doppler current profiler along a 146 x 146 km survey pattern centered near 10°N, 95°W in the eastern Pacific warm pool. Additional measurements from a second ship at the center of the survey pattern included radar backscatter from rainfall, air-sea fluxes, and vertical profiles of temperature, salinity, microstructure, and horizontal velocity. Satellite measurements of surface height, temperature, and rainfall were also analyzed. The heat budget of 20 and 25 m surface layers indicated that storage, advection, turbulent transport, and penetrative solar radiation were all significant components of the heat budget with a net surface cooling of 41 W m-2 estimated as a residual, which agreed with atmospheric measurements (30 W m-2). The precipitation rate from the freshwater budget was 29 mm d-1, which was in excellent agreement with in situ measurements on both ships and in good agreement with satellite estimates for the same period. Lateral transports of heat and salt were influenced by an anticyclonic eddy in the survey area, and it is suggested that anticyclonic eddies, which form near the Central American coast, may carry anomalously warm sea surface temperature toward the west and become preferential sites for heavy rainfall.

Direct measurements of diapycnal mixing in a fjord reach - Puget Sound's Main Basin

Mickett, J.B., M.C. Gregg, and H.E. Seim, "Direct measurements of diapycnal mixing in a fjord reach - Puget Sound's Main Basin," Estuar. Coast. Shelf Sci., 59, 539-558, doi:10.1016/j.ecss.2003.10.009, 2004.

1 Apr 2004

In The News

UW, NOAA deploy ocean robot to monitor harmful algal blooms off Washington coast

UW News and Information, Hannah Hickey

John Mickett, an oceanographer at the UW Applied Physics Laboratory, led the deployment of the new instrument with Stephanie Moore, a scientist at NOAA’s Northwest Fisheries Science Center, as part of a larger collaborative project.

25 May 2016

Buoy deployed in Bellingham Bay to chart health of Puget Sound

KING 5 News, Alison Morrow

Oceanographers deployed a buoy in Bellingham Bay on Thursday that will chart the health of Puget Sound. It joins a half-dozen other buoys, but this is the only one in the north Puget Sound. It is equipped with several pieces of advanced technology that will monitor everything from salinity, temperature and weather changes.

11 Feb 2016

Arctic research ship probes frigid depths and 4th-lowest sea ice extent on record

Mashable, Andrew Freedman

One of the mysteries of the sea ice loss of the past few decades, particularly this year, is how the heat distribution is changing in various regions of the Arctic. Right now, the National Science Foundation's R/V Sikuliaq is sailing in the Beaufort Sea, north of Alaska, to investigate the distribution of heat throughout the water column, as well as how layers of water are interacting with one another.

17 Sep 2015

More News Items

Take a Virtual Voyage to the Arctic Ocean

UW News and Information, Hannah Hickey

If you%u2019ve ever wanted to travel north of the Arctic Circle in early fall, when the expanse of iceberg-filled water reaches its greatest extent, this is your chance.

A University of Washington oceanographer is one of three principal investigators on a monthlong research cruise to the Beaufort Gyre. The researchers are posting updates, photos and videos of their study of Arctic Ocean mixing through Sept. 26.

14 Sep 2015

Dot Earth: Deep-ocean waves

The New York Times, Andrew Revkin

Scientists at the University of Washington have found skyscraper-height waves in deep ocean layers in the South Pacific — in some cases breaking in slow motion like surf on a beach. The finding sheds light on processes that allow heat in shallower ocean waters to mix with abyssal currents.

11 Sep 2013

Breaking deep-sea waves reveal mechanism for global ocean mixing

UW News & Information, Hannah Hickey

A University of Washington study for the first time recorded wave breaking in a key bottleneck for circulation in the world%u2019s largest ocean — the Samoan Passage, a narrow channel in the South Pacific Ocean that funnels water flowing from Antarctica.

9 Sep 2013

Tracking skyscraper-high waves across the globe

OceanCurrents Magazine

Internal-wave-driven mixing turns out to be a vital aspect of the ocean's circulation. We currently believe that without breaking internal waves, the deep sea would be a stagnant, homogenous deep pool of cold water with a very thin warm layer atop it. Since we instead observe a much more gradual decrease in temperature, we conclude that there is mixing in the abyss and that breaking internal waves lead to much of it. Therefore, internal wave mixing is part of the "bloodstream" of the ocean, enabling the upward part of the "conveyor belt" circulation by moving cold water upward. And that means that our predictions of climate change have significant uncertainty because we do not fully understand the sources, travel pathways and eventual breaking locations of the internal waves in the sea.

14 Apr 2013

Wavechasers condemn gummy bears to crushing ocean depths

UW Today, Sandra Hines

Follow the serious science - and the development of novel "Will it crush?" segments inspired by the YouTube hit "Will it blend?" - as University of Washington Wavechasers work in the South Pacific near Samoa. The expedition Oct. 24 to Nov. 5 is led by the UW Applied Physics Laboratory's Matthew Alford, with scientists trying to learn more about waves as tall as skyscrapers that roll along unseen thousands of feet below the ocean surface.

2 Nov 2011

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