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Trina Litchendorf

Oceanographer IV





Department Affiliation

Ocean Engineering


2000-present and while at APL-UW

Statistics of surface divergence and their relation to air–water gas transfer velocity

Asher, W.E., H. Kiang, C.J. Zappa, M.R. Loewen, M.A. Mukto, T.M. Litchendorf, and A.T. Jessup,"Statistics of surface divergence and their relation to air–water gas transfer velocity," J. Geophys. Res., 117, doi:10.1029/2001JC007390, 2012.

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24 May 2012

Air-sea gas fluxes are generally defined in terms of the air/water concentration difference of the gas and the gas transfer velocity, kL. Because it is difficult to measure kL in the ocean, it is often parameterized using more easily measured physical properties. Surface divergence theory suggests that infrared (IR) images of the water surface, which contain information concerning the movement of water very near the air-water interface, might be used to estimate kL. Therefore, a series of experiments testing whether IR imagery could provide a convenient means for estimating the surface divergence applicable to air-sea exchange were conducted in a synthetic jet array tank embedded in a wind tunnel. Gas transfer velocities were measured as a function of wind stress and mechanically generated turbulence; laser-induced fluorescence was used to measure the concentration of carbon dioxide in the top 300 µm of the water surface; IR imagery was used to measure the spatial and temporal distribution of the aqueous skin temperature; and particle image velocimetry was used to measure turbulence at a depth of 1 cm below the air-water interface. It is shown that an estimate of the surface divergence for both wind-shear driven turbulence and mechanically generated turbulence can be derived from the surface skin temperature. The estimates derived from the IR images are compared to velocity field divergences measured by the PIV and to independent estimates of the divergence made using the laser-induced fluorescence data. Divergence is shown to scale with kL values measured using gaseous tracers as predicted by conceptual models for both wind-driven and mechanically generated turbulence.

Near-real-time acoustic monitoring of beaked whales and other cetaceans using a Seaglider

Klinck, H., D.K. Mellinger, K. Klinck, N.M. Bogue, J.C. Luby, W.A. Jump, G.B. Shilling, T. Litchendorf, A.S. Wood, G.S. Schorr, and R.W. Baird, "Near-real-time acoustic monitoring of beaked whales and other cetaceans using a Seaglider," Plos One, 7, e36128, doi:10.1371/journal.pone.0036128, 2012.

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18 May 2012

In most areas, estimating the presence and distribution of cryptic marine mammal species, such as beaked whales, is extremely difficult using traditional observational techniques such as ship-based visual line transect surveys. Because acoustic methods permit detection of animals underwater, at night, and in poor weather conditions, passive acoustic observation has been used increasingly often over the last decade to study marine mammal distribution, abundance, and movements, as well as for mitigation of potentially harmful anthropogenic effects. However, there is demand for new, cost-effective tools that allow scientists to monitor areas of interest autonomously with high temporal and spatial resolution in near-real time. Here we describe an autonomous underwater vehicle — a glider — equipped with an acoustic sensor and onboard data processing capabilities to passively scan an area for marine mammals in near-real time. The instrument developed here can be used to cost-effectively screen areas of interest for marine mammals for several months at a time. The near-real-time detection and reporting capabilities of the glider can help to protect marine mammals during potentially harmful anthropogenic activities such as seismic exploration for sub-sea fossil fuels or naval sonar exercises. Furthermore, the glider is capable of under-ice operation, allowing investigation of otherwise inaccessible polar environments that are critical habitats for many endangered marine mammal species.

Storm-induced upwelling of high pCO2 waters onto the continental shelf of the western Arctic Ocean and implications for carbonate mineral saturation states

Mathis, J.T., R.S. Pickart, R.H. Byrne, C.L. McNeil, G.W.K. Moore, L.W. Juranek, X. Liu, J. Ma, R.A. Easley, M.M. Elliot, J.N. Cross, S.C. Reisdorph, F. Bahr, J. Morison, T. Lichendorf, and R.A. Feely, "Storm-induced upwelling of high pCO2 waters onto the continental shelf of the western Arctic Ocean and implications for carbonate mineral saturation states," Geophys. Res. Lett., 39, doi:10.1029/2012GL051574, 2012.

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11 Apr 2012

The carbon system of the western Arctic Ocean is undergoing a rapid transition as sea ice extent and thickness decline. These processes are dynamically forcing the region, with unknown consequences for CO2 fluxes and carbonate mineral saturation states, particularly in the coastal regions where sensitive ecosystems are already under threat from multiple stressors. In October 2011, persistent wind-driven upwelling occurred in open water along the continental shelf of the Beaufort Sea in the western Arctic Ocean. During this time, cold (<–1.2°C), salty (>32.4) halocline water — supersaturated with respect to atmospheric CO2 (pCO2 > 550 µatm) and undersaturated in aragonite (< 1.0) was transported onto the Beaufort shelf. A single 10-day event led to the outgassing of 0.18–0.54 Tg-C and caused aragonite undersaturations throughout the water column over the shelf. If we assume a conservative estimate of four such upwelling events each year, then the annual flux to the atmosphere would be 0.72–2.16 Tg-C, which is approximately the total annual sink of CO2 in the Beaufort Sea from primary production. Although a natural process, these upwelling events have likely been exacerbated in recent years by declining sea ice cover and changing atmospheric conditions in the region, and could have significant impacts on regional carbon budgets. As sea ice retreat continues and storms increase in frequency and intensity, further outgassing events and the expansion of waters that are undersaturated in carbonate minerals over the shelf are probable.

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Passive-acoustic monitoring of odontocetes using a Seaglider: First results of a field test in Hawaiian waters.

Klink, H., D.K. Mellniger, M.A. Roch, K. Klinck, N.M. Bogue, J.C. Luby, W.A. Jump, J.M. Pyle, G.B. Shilling, T. Litchendorf, and A.S. Wood, "Passive-acoustic monitoring of odontocetes using a Seaglider: First results of a field test in Hawaiian waters." J. Acoust. Soc. Am., 129, 2536, doi:10.1121/1.3588409, 2011.

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1 Apr 2011

In fall 2009 the University of Washington, Applied Physics Laboratory conducted in collaboration with the Oregon State University, a comprehensive field test of a passive-acoustic Seaglider along the western shelf-break of the island of Hawaii. During the 3 week mission, a total of approximately 170 h of broadband acoustic data [194 kHz sampling rate] were collected. The recordings were manually analyzed by an experienced analyst for beaked whale (Ziphiidae), dolphin (Delphinidae), and sperm whale (Physeter macrocephalus) echolocation clicks as well as echo sounder pings emitted by boats in the area. Here we present and discuss first results of these data analysis, which revealed that more than 50% of the recorded files (each of 1-minute duration) contain bioacoustic signals. Furthermore the recorded data and the results of the manual analysis are used to validate and optimize an automated classifier for odontocete echolocation clicks, which was developed in a collaborative effort with San Diego State University. The algorithm is intended to be implemented on the Seaglider to enable species identification by classifying detected echolocation clicks in (near) real-time during sea trials.

Visualizing near-surface concentration fluctuations using laser-induced fluorescence

Asher, W.E., and T.M. Litchendorf, "Visualizing near-surface concentration fluctuations using laser-induced fluorescence," Exp. Fluids, 46, 243-253, doi:10.1007/s00348-008-0554-9, 2009.

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1 Feb 2009

A method for observing near-surface fluctuations in pH caused by a water–air flux of carbon dioxide under conditions of ambient atmospheric carbon dioxide levels is developed and tested. Peaks in fluorescence intensity measured as a function of pH and turbulence are shown to be consistent with predictions from a chemical kinetics model of CO2 exchange. The square root of the frequency of the pH fluctuations scale linearly with independently measured bulk air–water gas transfer velocities in agreement with surface divergence models for air–water gas transfer. These data indicate that the method proposed here is tracking changes in near-surface CO2 concentrations. This laser-induced fluorescence method can be used to study the air–water exchange of CO2 in wind-wave tunnels without the need for elevated CO2 concentrations in the gas phase.

Fractional area whitecap coverage and air-sea gas transfer during GasEx-98

Asher, W.E., J.B. Edson, W.R. McGillis, R. Wanninkhof, D.T. Ho, and T. Litchendorf, "Fractional area whitecap coverage and air-sea gas transfer during GasEx-98," in Gas Transfer at Water Surfaces, edited by M.A. Donelan, W.M. Drennan, E.S. Saltzman, and R. Wanninkhof, 199-204 (American Geophysical Union, Washington, D.C., 2002).

15 Jan 2002

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