APL-UW Home

Jobs
About
Campus Map
Contact
Privacy
Intranet

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.

More Info

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

More Projects

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

More Videos

Publications

2000-present and while at APL-UW

High-resolution observations of the North Pacific transition layer from a Lagrangian float

Kaminski, A.K., E.A. D'Asaro, A.Y. Shcherbina, and R.R. Harcourt, "High-resolution observations of the North Pacific transition layer from a Lagrangian float," J. Phys. Oceanogr., 51, 3163-3181, doi:10.1175/JPO-D-21-0032.1, 2021.

More Info

1 Oct 2021

A crucial region of the ocean surface boundary layer (OSBL) is the strongly-sheared and -stratified transition layer (TL) separating the mixed layer from the upper pycnocline, where a diverse range of waves and instabilities are possible. Previous work suggests that these different waves and instabilities will lead to different OSBL behaviours. Therefore, understanding which physical processes occur is key for modelling the TL. Here we present observations of the TL from a Lagrangian float deployed for 73 days near Ocean Weather Station Papa (50°N, 145°W) during Fall 2018. The float followed the vertical motion of the TL, continuously measuring profiles across it using an ADCP, temperature chain and salinity sensors. The temperature chain made depth/time images of TL structures with a resolution of 6 cm and 3 seconds. These showed the frequent occurrence of very sharp interfaces, dominated by temperature jumps of O(1)°C over 6 cm or less. Temperature inversions were typically small (less than about 10 cm), frequent, and strongly-stratified; very few large overturns were observed. The corresponding velocity profiles varied over larger length scales than the temperature profiles. These structures are consistent with scouring behaviour rather than Kelvin–Helmholtz-type overturning. Their net effect, estimated via a Thorpe-scale analysis, suggests that these frequent small temperature inversions can account for the observed mixed layer deepening and entrainment flux. Corresponding estimates of dissipation, diffusivity, and heat fluxes also agree with previous TL studies, suggesting that the TL dynamics is dominated by these nearly continuous 10-cm scale mixing structures, rather than by less frequent larger overturns.

Thorpe turbulence scaling in night time convective surface layers in the North Indian Ocean

Praveen Kumar, B., E.A. D'Asaro, N. Sureshkumar, E. Pattabhi Rama Rao, and M. Ravichandran, "Thorpe turbulence scaling in night time convective surface layers in the North Indian Ocean," J. Phys. Oceanogr., 51, 3203-3216, doi:10.1175/JPO-D-21-0017.1, 2021.

More Info

19 Aug 2021

We use profiles from a Lagrangian Float in the North Indian Ocean to explore the usefulness of Thorpe analysis methods to measure vertical scales and dissipation rates in the ocean surface boundary layer. An rms Thorpe length scale LT and an energy dissipation rate εT were computed by resorting the measured density profiles. These are compared to the mixed layer depth (MLD) computed with different density thresholds, the Monin–Obukhov (MO) length LMO computed from the ERA5 reanalysis values of wind stress and buoyancy flux B0 and dissipation rates ε from historical microstructure data. LT is found to accurately match MLD for small (<0.005 kgm-3) density thresholds, but not for larger thresholds, because these do not detect the warm diurnal layers. We use ξ = LT/|LMO| to classify the boundary layer turbulence during night-time convection. In our data, 90% of points from the Bay of Bengal (Arabian Sea) satisfy ξ < 1 (1 < ξ < 10), indicating that wind forcing is (both wind forcing and convection are) driving the turbulence. Over the measured range of ξ, εT decreases with decreasing ξ, i.e. more wind forcing, while ε; increases, clearly showing that ε/εT decreases with increasing ξ. This is explained by a new scaling for ξ << 1, εT = 1.15 B 0 ξ0.5 compared to the historical scaling ε = 0.64 B 0 + 1.76ξ-1. For ξ >> 1 we expect ε = εT. Similar calculations may be possible using routine ARGO float and ship data, allowing more detailed global measurements of εT thereby providing large-scale tests of turbulence scaling in boundary layers.

The mixed layer salinity budget in the central equatorial Indian Ocean

Chi, N.-H., R.-C. Lien, and E.A. D'Asaro, "The mixed layer salinity budget in the central equatorial Indian Ocean," J. Geophys. Res., 126, doi:10.1029/2021JC017280, 2021.

More Info

1 Jun 2021

The oceanic surface mixed layer salinity (MLS) budget of the central and eastern equatorial Indian Ocean during boreal fall and winter is studied using in-situ and remote sensing measurements. Budgets on roughly 100 km scale were constructed using data from two DYNAMO and two RAMA moorings near 79°E during September 2011 to January 2012. The horizontal advective salinity flux plays a significant role in the seasonal variation of equatorial MLS. In boreal fall the equatorial and 1.5°S MLS increases due to horizontal advection and turbulent mixing, despite the freshening surface flux associated with MJOs. In boreal winter, with larger sub-monthly variation and uncertainties, the decreasing of equatorial MLS is accounted by freshening zonal advection and surface flux, abated by salty meridional advection; the 1.5°S MLS is explained by the combination of freshening meridional advection and surface flux, and salty zonal advection. Budgets between 2011 and 2015 are investigated using data products from TRMM, Aquarius, OSCAR, OAFlux and Argo mixed layers over a wider region. The eastward development of the equatorial salinity tongue in the central to eastern Indian Ocean in boreal fall and the westward retreat in boreal winter is largely determined by the equatorial zonal current. The meridional migration of ITCZ rainfall plays a secondary role. In order to improve model prediction skills of MLS changes in the equatorial Indian Ocean, both zonal and meridional salinity advective fluxes, at a spatial scale of 1° longitude and latitude and a time scale less than days, need to be properly simulated.

More Publications

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

More News Items

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
Close

 

Close