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Eric D'Asaro

Senior Principal Oceanographer

Professor, Oceanography





Research Interests

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


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. Starting from a core interest in turbulence and internaI waves, it has expanded to include new aspects of small-scale oceanography, including submesoscale processes, and the role of all of these mixing processes in controlling biochemical processes in the ocean, including the distribution and fluxes of ocean gases 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 30 years, D'Asaro’s experimental work 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


B.A. Physics, Harvard University, 1976

M.S. Applied Physics, Harvard University, 1976

Ph.D. Oceanography, MIT/WHOI, 1980


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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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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2000-present and while at APL-UW

Diagnosing frontal dynamics from observations using a variational approach

Cutolo, E., and 11 others including A. Shcherbina and E. D'Asaro, "Diagnosing frontal dynamics from observations using a variational approach," J. Geophys. Res., 127, doi:10.1029/2021JC018336, 2022.

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1 Nov 2022

Intensive hydrographic and horizontal velocity measurements collected in the Alboran Sea enabled us to diagnose the three-dimensional dynamics of a frontal system. The sampled domain was characterized by a 40 km diameter anticyclonic eddy, with an intense front on its eastern side, separating the Atlantic and Mediterranean waters. Here, we implemented a multi-variate variational analysis (VA) to reconstruct the hydrographic fields, combining the 1-km horizontal resolution of the Underway Conductivity-Temperature-Depth (CTD) system with information on the flow shape from the Acoustic Doppler Current Profiler velocities. One advantage of the VA is given by the physical constraint, which preserves fine-scale gradients better than the classical optimal interpolation (OI). A comparison between real drifter trajectories and virtual particles advected in the mapping quantified the improvements in the VA over the OI, with a 15% larger skill score. Quasi-geostrophic (QG) and semi-geostrophic (SG) omega equations enabled us to estimate the vertical velocity (w) which reached 40 m/day on the dense side of the front. How nutrients and other passive tracers leave the mixed-layer and subduct is estimated with 3D advection from the VA, which agreed with biological sampling from traditional CTD casts at two eddy locations. Downwelling warm filaments are further evidence of subduction, in line with the w from SG, but not with QG. SG better accounted for the along-isopycnal component of w in agreement with another analysis made on isopycnal coordinates. The multi-platform approach of this work and the use of variational methods improved the characterization and understanding of (sub)-mesoscale frontal dynamics.

Drag coefficient and its sea state dependence under tropical cyclones

Zhou, X., T. Hara, I. Ginis, E. D'Asaro, J.-Y. Hsu, and B.G. Reichl, "Drag coefficient and its sea state dependence under tropical cyclones," J. Phys. Oceanogr., 52, 1447-1470, doi:10.1175/JPO-D-21-0246.1, 2022.

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1 Jul 2022

The drag coefficient under tropical cyclones and its dependence on sea states are investigated by combining upper ocean current observations (using EM-APEX floats deployed under five tropical cyclones) and a coupled ocean-wave (Modular Ocean Model 6 - WAVEWATCH III) model. The estimated drag coefficient averaged over all storms is around 2–3 x 10−3 for wind speeds 25–55 m/s. While the drag coefficient weakly depends on wind speed in this wind speed range, it shows stronger dependence on sea states. In particular, it is significantly reduced when the misalignment angle between the dominant wave direction and the wind direction exceeds about 45°, a feature which is underestimated by current models of sea state dependent drag coefficient. Since the misaligned swell is more common in the far front and in the left front quadrant of the storm (in the Northern Hemisphere), the drag coefficient also tends to be lower in these areas and shows a distinct spatial distribution. Our results therefore support ongoing efforts to develop and implement sea state dependent parameterizations of the drag coefficient in tropical cyclone conditions.

Double diffusion in the Arabian Sea during winter and spring

Ashin, K., and 9 others including E. D'Asaro, "Double diffusion in the Arabian Sea during winter and spring," J. Phys. Oceanogr., 52, 1205-1231, doi:10.1175/JPO-D-21-0186.1, 2022.

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1 Jun 2022

Microstructure measurements from two cruises during winter and spring 2019 documented the importance of double diffusion processes for small-scale mixing in the upper 400 m of the open ocean region of the eastern Arabian Sea (EAS) below the mixed layer. The data indicated that shear-driven mixing rates are weak, contributing diapycnal diffusivity (Kρ) of not more than 5.4x106 m2 s1 in the EAS. Instead, signatures of double diffusion were strong, with the water column favourable for salt fingers in 70% of the region and favourable for diffusive convection in 2–3% of the region. Well-defined thermohaline staircases were present in all the profiles in these regions that occupied 20% of the water column. Strong diffusive convection favourable regime occurred in ∼ 45% of data in the barrier layer region of the southern EAS (SEAS). Comparison of different parameterizations of double diffusion with the measurements of vertical heat diffusivity (KT) found that the Radko and Smith (2012) salt fingering scheme and the Kelley (1984) diffusive convection schemes best match with the observations. The estimates based on flux law show that the combination of downward heat flux of approximately –3 Wm2 associated with salt fingering in the thermocline region of the EAS and the upward heat flux of ~5 Wm2 due to diffusive convection in the barrier layer region of the SEAS cools the thermocline.

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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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