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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

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.

Serendipitous internal wave signals in Deep Argo data

Johnson, G.C., C.B. Whalen, S.G. Purkey, and N. Zilberman, "Serendipitous internal wave signals in Deep Argo data," Geophys. Res. Lett., 49, doi:10.1029/2022GL097900, 2022.

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16 Apr 2022

Ocean density increases with increasing depth, supporting internal waves below the ocean surface. These internal waves are generated near the surface by varying wind forcing such as passing storms and near the bottom by interactions of currents (including tidal) with rough bathymetry (such as seamounts and ridges). They can travel for long distances in both the vertical and the horizontal. When they break, they play important roles in mixing temperature, salinity, and other water properties. Deep Argo is an observing system designed to measure temperature and salinity profiles from the surface to the bottom of the ocean. One model of Deep Argo float serendipitously observes internal wave signals as variations in descent rate data, which it collects primarily for navigation purposes, from the surface to the seafloor. These observations reveal patterns in the magnitudes of these internal wave signals, with stronger internal wave activity near continental rises and mid-ocean ridges and lower levels over smoother abyssal plains. Also, regions with strong deep flows, such as the Samoan Passage through which bottom water is funneled into the North Pacific, or the region south of the Campbell Plateau through which the Antarctic Circumpolar Current flows, exhibit stronger deep internal wave signatures.

Abyssal heat budget in the southwest Pacific basin

Lele, R., and 8 others including C.B. Whalen, "Abyssal heat budget in the southwest Pacific basin," J. Phys. Oceanogr., 51, doi:10.1175/JPO-D-21-0045.1, 2021.

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1 Nov 2021

The abyssal Southwest Pacific Basin has warmed significantly between 1992–2017, consistent with warming along the bottom limb of the meridional overturning circulation seen throughout the global oceans. Here we present a framework for assessing the abyssal heat budget that includes the time-dependent unsteady effects of decadal warming and direct and indirect estimates of diapycnal mixing from microscale temperature measurements and finescale parameterizations. The unsteady terms estimated from the decadalwarming rate are shown to be within a factor of 3 of the steady state terms in the abyssal heat budget for the coldest portion of the water column and therefore, cannot be ignored. We show that a reduction in the lateral heat flux for the coldest temperature classes compensated by an increase in warmer waters advected into the basin has important implications for the heat balance and diffusive heat fluxes in the basin. Finally, vertical diffusive heat fluxes are estimated in different ways: using the newly available CTD-mounted microscale temperature measurements, a finescale strain parameterization, and a vertical kinetic energy parameterization from data along the P06 transect along 32.5°S. The unsteady-state abyssal heat budget for the basin shows closure within error estimates, demonstrating that (i) unsteady terms have become consequential for the heat balance in the isotherms closest to the ocean bottom and (ii) direct and indirect estimates from full depth GO-SHIP hydrographic transects averaged over similarly large spatial and temporal scales can capture the basin-averaged abyssal mixing needed to close the deep overturning circulation.

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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