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Caitlin Whalen

Senior Oceanographer

Affiliate Assistant Professor, Oceanography

Email

cwhalen@apl.uw.edu

Phone

206-897-1739

Research Interests

Small-scale oceanic processes as viewed from global and regional scales including diapycnal mixing, internal waves, submesoscale dynamics, air–sea interactions, and mesoscale–internal wave interactions

Education

B.A. Physics, Reed College, 2008

Ph.D. Physical Oceanography, University of California at San Diego, 2015

Publications

2000-present and while at APL-UW

Global observations of rotary-with-depth shear spectra

Waterhouse, A.F., and 10 others including C.B. Whalen, "Global observations of rotary-with-depth shear spectra," J. Phys. Oceanogr., 52, 3241-3258, doi:10.1175/JPO-D-22-0015.1, 2022.

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1 Dec 2022

Internal waves are predominantly generated by winds, tide/topography interactions and balanced flow/topography interactions. Observations of vertical shear of horizontal velocity (uz, vz) from LADCP profiles conducted during GO-SHIP hydrographic surveys, as well as vessel-mounted sonars, are used to interpret these signals. Vertical directionality of intermediate-wavenumber internal waves is inferred in this study from rotary-with-depth shears. Total shear variance and vertical asymmetry ratio, i.e. the normalized difference between downward- and upward-propagating intermediate wavenumber shear variance, where Ω > 0 (< 0) indicates excess downgoing (upgoing) shear variance, are calculated for three depth ranges: 200–600 m, 600 m to 1000 mab (meters above bottom), and below 1000 mab. Globally, downgoing (clockwise-with-depth in the northern hemisphere) exceeds upgoing (counterclockwise-with-depth in the northern hemisphere) shear variance by 30% in the upper 600 m of the water column (corresponding to the globally averaged asymmetry ratio of Ω = 0.13), with a near-equal distribution below 600-m depth. Downgoing shear variance in the upper water column dominates at all latitudes. There is no statistically significant correlation between the global distribution of Ω and internal wave generation, pointing to an important role for processes that re-distribute energy within the internal wave continuum on wavelengths of Ο(100 m).

Island Arc Turbulent Eddy Regional Exchange (ARCTERX): Science and Experiment Plan

The ARCTERX Team, "Island Arc Turbulent Eddy Regional Exchange (ARCTERX): Science and Experiment Plan," Technical Report, APL-UW TR 2201. Applied Physics Laboratory, University of Washington, July 2022, 49 pp.

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15 Jul 2022

Submesoscale flows such as fronts, eddies, filaments, and instabilities with lateral dimensions between 100 m and 10 km are ubiquitous features of the ocean. They act as an intermediary between the mesoscale and small-scale turbulence and are thought to have a critical role in closing the ocean's kinetic budget by facilitating a forward energy cascade, where energy is transferred to small scales and dissipated.

The initiative uses a suite of measurements from autonomous platforms and ships combined with regional simulations to characterize the submesoscale flows in the western Pacific Ocean between Luzon and Mariana Island arcs &$151; the ARCTERX region.

Program goals are to characterize the strength and spectral properties of the turbulent cascade of kinetic energy on the submesoscales in the ARCTERX study region and understand the processes that control energy transfers across scales and their seasonal variability.

Tracer and observationally derived constraints on diapycnal diffusivities in an ocean state estimate

Trossman, D.S., C.B. Whalen, T.W.N. Haine, A.F. Waterhouse, A.T. Nguyen, A. Bigdeli, M. Mazloff, and P. Heimbach, "Tracer and observationally derived constraints on diapycnal diffusivities in an ocean state estimate," Ocean Sci., 18, 729-759, doi:10.5194/os-18-729-2022, 2022.

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30 May 2022

Use of an ocean parameter and state estimation framework — such as the Estimating the Circulation and Climate of the Ocean (ECCO) framework — could provide an opportunity to learn about the spatial distribution of the diapycnal diffusivity parameter (kρ) that observations alone cannot due to gaps in coverage. However, we show that the inclusion of misfits to observed physical variables — such as in situ temperature, salinity, and pressure — currently accounted for in ECCO is not sufficient, as kρ from ECCO does not agree closely with any observationally derived product. These observationally derived kρ products were inferred from microstructure measurements, derived from Argo and conductivity–temperature–depth (CTD) data using a strain-based parameterization of fine-scale hydrographic structure, or calculated from climatological and seafloor data using a parameterization of tidal mixing. The kρ products are in close agreement with one another but have both measurement and structural uncertainties, whereas tracers can have relatively small measurement uncertainties. With the ultimate goal being to jointly improve the ECCO state estimate and representation of kρ in ECCO, we investigate whether adjustments in kρ due to inclusion of misfits to a tracer — dissolved oxygen concentrations from an annual climatology — would be similar to those due to inclusion of misfits to observationally derived kρ products. We do this by performing sensitivity analyses with ECCO. We compare multiple adjoint sensitivity calculations: one configuration uses misfits to observationally derived kρ, and the other uses misfits to observed dissolved oxygen concentrations. We show that adjoint sensitivities of dissolved oxygen concentration misfits to the state estimate's control space typically direct kρ to improve relative to the observationally derived values. These results suggest that the inclusion of oxygen in ECCO's misfits will improve kρ in ECCO, particularly in (sub)tropical regions.

More Publications

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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