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Eric D'Asaro

Senior Principal Oceanographer

Professor, Oceanography

Email

dasaro@apl.washington.edu

Phone

206-685-2982

Research Interests

Physical oceanography, internal waves, air-sea interaction, upper ocean dynamics, Arctic oceanography, ocean instrumentation

Biosketch

Dr. D'Asaro's research spans a wide number of environments from upper ocean mixed layers to nearshore coastal fronts to fjords to deep convection. It retains studies of turbulence and internal waves, but has increasingly moved toward understanding the role of these ocean mixing processes in controlling biochemical processes in the ocean, especially gas exchange and biological productivity. By measuring big signals, like hurricanes or major blooms, it is easier to unravel the underlying processes because the signal to noise is high.

For the past 20 years, D'Asaro has focused on exploiting the unique capabilities of "Lagrangian Floats", a class of instruments that try to accurately follow the three dimensional motion of water parcels particularly in regions of strong mixing. This turns out to be a novel but effective way to measure turbulence in regions of strong mixing.

Lagrangian techniques have not been used very much in measuring mixing and turbulence. Accordingly one of the more exciting aspects of this work is learning how to use Lagrangian floats in the ocean. This understanding draws both upon basic ideas in fluid mechanics and upon understanding of mixing in the ocean. It strongly influences float design, use, and the oceanographic problems studied. The work thus spans a wide range of topics, from fluid mechanics to oceanography to engineering. That makes it particularly fun and interesting.

Chemical species in the ocean and many microbial plants and animals drift with the ocean currents. Floats mimic this behavior, making them excellent platforms for studying aspects of ocean chemistry and biology. There is an ongoing revolution in these fields as electronic sensors become capable of making measurements formerly possible only in the laboratory. Floats equipped with such sensors are potentially very powerful tools. Dr. D'Asaro works to realize this potential, which is especially challenging and interesting as he collaborates with ocean biologists and chemists to design and operate multidisciplinary floats.

Department Affiliation

Ocean Physics

Education

B.A. Physics, Harvard University, 1976

M.S. Applied Physics, Harvard University, 1976

Ph.D. Oceanography, MIT/WHOI, 1980

Projects

Wave Measurements at Ocean Weather Station PAPA

As part of a larger project to understand the impact of surface waves on the ocean mixed layer, APL-UW is measuring waves at Ocean Weather Station Papa, a long-term observational site at N 50°, W 145°.

29 Aug 2019

Air–Sea Momentum Flux in Tropical Cyclones

The intensity of a tropical cyclone is influenced by two competing physical processes at the air–sea interface. It strengthens by drawing thermal energy from the underlying warm ocean but weakens due to the drag of rough ocean surface. These processes change dramatically as the wind speed increases above 30 m/s.

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30 Mar 2018

The project is driven by the following science questions: (1) How important are equilibrium-range waves in controlling the air-sea momentum flux in tropical cyclones? We hypothesize that for wind speeds higher than 30 m/s the stress on the ocean surface is larger than the equilibrium-range wave breaking stress. (2) How does the wave breaking rate vary with wind speed and the complex surface wave field? At moderate wind speeds the wave breaking rate increases with increasing speed. Does this continue at extreme high winds? (3) Can we detect acoustic signatures of sea spray at high winds? Measurements of sea spray in tropical cyclones are very rare. We will seek for the acoustic signatures of spray droplets impacting the ocean surface. (4) What are the processes controlling the air-sea momentum flux?

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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Videos

EXPORTS: Export Processes in the Ocean from RemoTe Sensing

The EXPORTS mission is to quantify how much of the atmospheric carbon dioxide fixed during primary production near the ocean surface is pumped to the deep twilight zone by biological processes, where it can be sequestered for months to millennia.

An integrated observation strategy leverages the precise, intense measurements made on ships, the persistent subsurface data collected by swimming and floating robots, and the global surface views provided by satellites.

18 Sep 2018

Lagrangian Submesoscale Experiment — LASER

A science team led by Eric D'Asaro conducted a unique mission to deploy over 1,000 ocean drifters in a small area of the Gulf of Mexico. The real-time data collected from the biodegradable drifters recalibrated understanding of ocean currents.

22 Jan 2018

Eddies Drive Particulate Carbon Deep in the Ocean During the North Atlantic Spring Bloom

The swirling eddies that create patches of stratification to hold phytoplankton near the sunlit surface during the North Atlantic spring bloom, also inject the floating organic carbon particles deep into the ocean. The finding, reported in Science, has important implications for the ocean's role in the carbon cycle on Earth: phytoplankton use carbon dioxide absorbed by the ocean from the atmosphere during the bloom and the resulting organic carbon near the sea surface is sequestered in the deep ocean.

27 Mar 2015

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Publications

2000-present and while at APL-UW

Suppression of CO2 outgassing by gas bubbles under a hurricane

Liang, J.-H., E.A. D'Asaro, C.L. McNeil, Y. Fan, R.R. Harcourt, S.R. Emerson, B. Yang, and P.P. Sullivan, "Suppression of CO2 outgassing by gas bubbles under a hurricane," Geophys. Res. Lett., 47, doi:10.1029/2020GL090249, 2020.

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28 Sep 2020

The role of gas bubbles on the air‐sea CO2 flux during Hurricane Frances (2004) is studied using a large‐eddy simulation model that couples ocean surface boundary layer turbulence, gas bubbles, and dissolved gases. In the subtropical surface ocean where gases are slightly supersaturated, gases in bubbles can still dissolve due to hydrostatic pressure and surface tension exerted on bubbles. Under the simulated conditions, the CO2 efflux with an explicit bubble effect is less than 2% of that calculated using a gas flux formula without explicit inclusion of bubble effect. The use of a gas flux parameterization without bubble‐induced supersaturation contributes to uncertainty in the global carbon budget. The results highlight the importance of bubbles under high winds even for soluble gases such as CO2 and demonstrate that gas flux parameterization derived from gases of certain solubility may not be accurate for gases of very different solubility.

Observations of cross-frontal exchange associated with submesoscale features along the North Wall of the Gulf Stream

Sanchez-Rios, A., R.K. Sherman, J. Klymak, E. D'Asaro, and C. Lee, "Observations of cross-frontal exchange associated with submesoscale features along the North Wall of the Gulf Stream," Deep Sea Res., 163, doi:10.1016/j.dsr.2020.103342, 2020.

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1 Sep 2020

Using high-resolution measurements of the Gulf Stream North Wall (GSNW), we investigated whether detachments from the warm current at the edge of the front, known as streamers, affect the overall heat and salt content of the region. Temperature, salinity, and velocity data were collected across the front from towed CTDs, shipboard ADCPs, and gliders following a Lagrangian drifter that was deployed at the GSNW during winter 2012. Four streamers were identified, all of which expanded laterally 10–15 km, with vertical salinity interleaving down to a 200 m depth. We observed that temperature and salinity (T/S) increased along the trajectory of the Lagrangian float. These trends were density compensated and ranged from the surface down to a 200 m depth and across a 5 km band. The heat and salt budget analysis showed that surface fluxes, advection due to large-scale circulation, and diapycnal mixing could not explain the observed increase in T/S in the mixed layer and in the subsurface area. The only possible source that could explained the increase in T/S was along-isopycnal mixing. Estimates of the Reynolds transport supported this conclusion, although the low number of realizations meant these estimates were not statistically significant. From the heat and salt budgets, we observed that an along-isopycnal diffusivity, ki, of 110 ± 30 m2s-1 accounted for the estimated residual and matched the Reynolds transport estimates. This value of is consistent with other studies that assert that lateral mixing is required for the production of Eighteen Degree Water (EDW) subtropical mode water.

Structure of the Bay of Bengal oxygen deficient zone

D'Asaro, E., M. Altabet, N.S. Kumar, and M. Ravichandran, "Structure of the Bay of Bengal oxygen deficient zone," Deep-Sea Res. II, 179, 104650, doi:10.1016/j.dsr2.2019.104650, 2020.

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1 Sep 2020

Oxygen levels within the oxygen deficient zone (ODZ) of the Bay of Bengal are mapped using 11 ARGO floats spanning 5 years. North of about 18°N in the ODZ 'core', minimum oxygen levels are uniformly below ~1 µmol kg-1. South of this, in the ODZ 'edge', oxygen levels increase toward an average of about 7 µmol kg-1 at 10°N, but with high variability so that values below ~1 µmol kg-1 occur at all latitudes. This variability is consistent with simple models of mesoscale eddy stirring which suggest an exchange time for the core of about 1 year. Existing measurements of microbial transformation of nitrate to N2 in the Bay of Bengal have only been made in the edge region and may underestimate rates in the core region with lowest O2 concentration and thus the overall N transformation rates in this ODZ.

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In The News

NASA, NSF expedition to study ocean carbon embarks in August from Seattle

UW News, Hannah Hickey

Dozens of scientists, as well as underwater drones and other high-tech ocean instruments, will set sail from Seattle in mid-August. Funded by NASA and the National Science Foundation, the team will study the life and death of the small organisms that play a critical role in removing carbon dioxide from the atmosphere, and in the ocean’s carbon cycle.

21 Jun 2018

Scientists watch ocean plastic hotspots form in real time

NewsDeeply, Erica Cirino

Researchers tracked hundreds of buoys deployed in the Gulf of Mexico. Not only did the buoys not spread out – many concentrated into an area the size of a football stadium. The findings may help scientists pinpoint areas for plastic or oil-spill cleanup.

6 Feb 2018

Temporary 'bathtub drains' in the ocean concentrate flotsam

UW News, Hannah Hickey

An experiment featuring the largest flotilla of sensors ever deployed in a single area provides new insights into how marine debris, or flotsam, moves on the surface of the ocean.

18 Jan 2018

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Inventions

Open Water Detection from Beneath Sea Ice

Record of Invention Number: 47655

Eric D'Asaro, Andrey Shcherbina

Disclosure

16 Mar 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
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