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arXiv 2022年

作者： Preston, Victoria Flaspohler, Genevieve Michel, Anna P.M. Fisher, John W. Roy, Nicholas MIT-WHOI Joint Program Massachusetts Institute of Technology CambridgeMA02139 United States Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution United States Computer Science and Artificial Intelligence Laboratory Massachusetts Institute of Technology CambridgeMA02139 United States

In the expeditionary sciences, spatiotemporally varying environments - hydrothermal plumes, algal blooms, lava flows, or animal migrations - are ubiquitous. Mobile robots are uniquely well-suited to study these dynamic, mesoscale natural environments. We formalize expeditionary science as a sequential decision-making problem, modeled using the language of partially-observable Markov decision processes (POMDPs). Solving the expeditionary science POMDP under real-world constraints requires efficient probabilistic modeling and decision-making in problems with complex dynamics and observational models. Previous work in informative path planning, adaptive sampling, and experimental design have shown compelling results, largely in static environments, using data-driven models and information-based rewards. However, these methodologies do not trivially extend to expeditionary science in spatiotemporal environments: they generally do not make use of scientific knowledge such as equations of state dynamics, they focus on information gathering as opposed to scientific task execution, and they make use of decision-making approaches that scale poorly to large, continuous problems with long planning horizons and real-time operational constraints. In this work, we discuss these and other challenges related to probabilistic modeling and decision-making in expeditionary science, and present some of our preliminary work that addresses these gaps. We ground our results in a real expeditionary science deployment of an autonomous underwater vehicle (AUV) in the deep ocean for hydrothermal vent discovery and characterization. Our concluding thoughts highlight remaining work to be done, and the challenges that merit consideration by the reinforcement learning and decision-making community. Copyright © 2022, The Authors. All rights reserved.

关键词： Decision making

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Quantifying air-sea gas exchange using noble gases in a coastal upwelling zone 7

Quantifying air-sea gas exchange using noble gases in a coas...

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7th International Symposium on Gas Transfer at Water Surfaces

作者： Manning, C.C. Stanley, R.H.R. Nicholson, D.P. Squibb, M.E. Massachusetts Institute of Technology Woods Hole Oceanogr. Institution Joint Program in Oceanography/Applied Ocean Science and Engineering Woods HoleMA02543 United States Department of Marine Chemistry and Geochemistry Woods Hole Oceanographic Institution Woods HoleMA02543 United States Department of Chemistry Wellesley College WellesleyMA02481 United States Center for Ocean Solutions Stanford University StanfordCA94305 United States

The diffusive and bubble-mediated components of air-sea gas exchange can be quantified separately using time-series measurements of a suite of dissolved inert gases. We have evaluated the performance of four published air-sea gas exchange parameterizations using a five-day time-series of dissolved He, Ne, Ar, Kr, and Xe concentration in Monterey Bay, CA. We constructed a vertical model including surface air-sea gas exchange and vertical diffusion. Diffusivity was measured throughout the cruise from profiles of turbulent microstructure. We corrected the mixed layer gas concentrations for an upwelling event that occurred partway through the cruise. All tested parameterizations gave similar results for Ar, Kr, and Xe;their air-sea fluxes were dominated by diffusive gas exchange during our study. For He and Ne, which are less soluble, and therefore more sensitive to differences in the treatment of bubble-mediated exchange, the parameterizations gave widely different results with respect to the net gas exchange flux and the bubble flux. This study demonstrates the value of using a suite of inert gases, especially the lower solubility ones, to parameterize air-sea gas exchange. © Published under licence by IOP Publishing Ltd.

关键词： Inert gases

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Symptomatic and asymptomatic domoic acid exposure in zebrafish (Danio rerio) revealed distinct non-overlapping gene expression patterns in the brain

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Aquatic Toxicology 2022年 252卷 106310页

作者： Hidayat, Alia S. Lefebvre, Kathi A. MacDonald, James Bammler, Theo Aluru, Neelakanteswar MIT-WHOI Joint Program in Oceanography/Applied Ocean Science & Engineering Cambridge and Woods Hole MA United States Biology Department and Woods Hole Center for Oceans and Human Health Woods Hole Oceanographic Institution Woods Hole MA United States Environmental and Fisheries Science Division Northwest Fisheries Science Center National Marine Fisheries Service NOAA Seattle WA United States Department of Environmental and Occupational Health University of Washington Seattle WA United States

Domoic acid (DA) is a naturally produced neurotoxin synthesized by marine diatoms in the genus Pseudo-nitzschia. DA accumulates in filter-feeders such as shellfish, and can cause severe neurotoxicity when contaminated seafood is ingested, resulting in Amnesic Shellfish Poisoning (ASP) in humans. Overt clinical signs of neurotoxicity include seizures and disorientation. ASP is a significant public health concern, and though seafood regulations have effectively minimized the human risk of severe acute DA poisoning, the effects of exposure at asymptomatic levels are poorly understood. The objective of this study was to determine the effects of exposure to symptomatic and asymptomatic doses of DA on gene expression patterns in the zebrafish brain. We exposed adult zebrafish to either a symptomatic (1.1 ± 0.2 μg DA/g fish) or an asymptomatic (0.31 ± 0.03 µg DA/g fish) dose of DA by intracelomic injection and sampled at 24, 48 and 168 h post-injection. Transcriptional profiling was done using Agilent and Affymetrix microarrays. Our analysis revealed distinct, non-overlapping changes in gene expression between the two doses. We found that the majority of transcriptional changes were observed at 24 h post-injection with both doses. Interestingly, asymptomatic exposure produced more persistent transcriptional effects - in response to symptomatic dose exposure, we observed only one differentially expressed gene one week after exposure, compared to 26 in the asymptomatic dose at the same time (FDR <0.05). GO term analysis revealed that symptomatic DA exposure affected genes associated with peptidyl proline modification and retinoic acid metabolism. Asymptomatic exposure caused differential expression of genes that were associated with GO terms including circadian rhythms and visual system, and also the neuroactive ligand-receptor signaling KEGG pathway. Overall, these results suggest that transcriptional responses are specific to the DA dose and that asymptomatic exposure can

关键词： Domoic acid Excitotoxin Glutamate Harmful algal bloom toxin

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Corrigendum to “Lipid composition, caloric content, and novel oxidation products from microbial communities within seasonal pack ice cores” [Geochimica et Cosmochimica Acta 368 (2024) 12–23]

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Geochimica et Cosmochimica Acta 2024年 382卷 161-161页

作者： Henry C. Holm Helen F. Fredricks Shavonna M. Bent Daniel P. Lowenstein Kharis R. Schrage Benjamin A.S. Van Mooy Marine Chemistry and Geochemistry Department Woods Hole Oceanographic Institution Woods Hole MA 02543 USA MIT-WHOI Joint Program in Oceanography/Applied Ocean Science & Engineering Cambridge MA 02139 USA

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Characterization of range‐dependent shallow water waveguides

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The Journal of the Acoustical Society of America 2005年第S1期80卷 S52-S52页

作者： George V. Frisk Ferdinand J. Diemer Peter H. Dahl Department of Ocean Engineering Woods Hole Oceanographic Institution Woods Hole MA 02543 MIT/WHOI Joint Program in Oceanography/Oceanographic Engineering Woods Hole MA 02543

A technique for characterizing range‐dependent shallow water waveguides is described. The method consists of determining the beamformed output of a horizontal array over short apertures for signals due to a cw point source. By modeling the acoustic field locally as a sum of damped normal modes and using Prony's method to perform the beamforming, the local modal structure of the waveguide can be resolved. As a result, the modal composition of the waveguide as a function of range can be determined and interpreted in terms of range‐dependent mode theories (e.g., adiabatic mode theory). In addition to identifying important propagation characteristics such as mode cutoff, the method can be used to determine range‐dependent acoustic properties of the bottom. Examples of the application of the technique to the case of propagation in a wedge‐shaped ocean are presented. [Work supported by ONR.]

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A modal/WKB inversion method for determining sound‐speed profiles in the ocean and ocean bottom

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The Journal of the Acoustical Society of America 2005年第S1期84卷 S175-S175页

作者： Kevin D. Casey George V. Frisk MIT/WHOI Joint Program in Oceanography/Oceanographic Engineering Woods Hole MA 02543 Department of Ocean Engineering Woods Hole Oceanographic Institute Woods Hole MA 02543

Two approaches to determining sound‐speed profiles in the ocean and ocean bottom using measured acoustic modal eigenvalues are examined. Both methods use measured eigenvalues and mode‐dependent assumed values of the WKB phase integral as input data and use the WKB phase integral as a starting point for relating the index of refraction to depth. Inversion method 1 is restricted to monotonic or symmetric sound‐speed profiles and requires a measurement of the sound speed at one depth to convert the index of refraction profile to a sound‐speed profile. Inversion method 2 assumes that the sound speed at the ocean surface and the minimum sound speed in the profile are known and is applicable to monotonic profiles and to general single duct sound‐speed profiles. For asymmetric profiles, inversion method 2 gives the depth difference between two points of equal sound speed in the portion of the profile having two turning points, and in the remainder of the profile it gives sound speed versus depth directly. A numerical implementation of the methods is demonstrated using idealized ocean sound‐speed profiles. The two methods are used also to determine the sediment sound‐speed profiles in two shallow water waveguide models, and inversion method 1 is used to find the sediment sound‐speed profile using data from an experiment perfomed in the Gulf of Mexico. [Work supported by ONR.]

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Using spectrometry and photography to study color underwater

Using spectrometry and photography to study color underwater

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oceanS

作者： Derya Akkaynak Eric Chan Justine J. Allen Roger T. Hanlon Joint Program in Oceanography Applied Ocean Science & Engineering Massachusetts Institute of Technology and Woods Hole Oceanographic Institution Cambridge MA USA Massachusetts Institute of Technology Cambridge MA US The Brown-MBL Graduate Biological and Environmental Sciences Providence RI USA Marine Biological Laboratory Woods Hole MA USA

Most underwater images are post-processed to look pleasing to human viewers. This often results in unrealistically saturated colors. Images taken for the purpose of studying color-sensitive topics such as marine animal coloration, must represent colors as accurately as possible and should not be arbitrarily enhanced. This first requires a transformation of colors from the camera color space to a device independent space. In this paper we present a method for transforming raw camera-RGB colors to a device independent space, optimizing this transformation for a particular underwater habitat. We have conducted an extensive study of the variation of color appearance underwater at a dive site in the Aegean Sea by taking 21 sets of spectrometry and irradiance readings with corresponding photographs of four different color standards. Spectral and photographic data were collected in the presence of natural daylight at various depths and under different weather conditions. In addition to the color charts, we have built a “habitat chart” to optimize this camera-specific transformation for a given dive site.

关键词： Image color analysis Cameras Lighting Sensitivity Humans Optical surface waves Optical sensors

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Low‐frequency diffraction from a free surface coupled to a semi‐infinite elastic surface as modeled by sea ice properties

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The Journal of the Acoustical Society of America 2005年第S1期85卷 S50-S50页

作者： Peter H. Dahl George V. Frisk MIT/WHOI Joint Program in Oceanography/Oceanographic Engineering Department of Ocean Engineering Massachusetts Institute of Technology Cambridge MA 02139 Department of Ocean Engineering Woods Hole Oceanographic Institution Woods Hole MA 02543

This paper discusses the solution of a low‐frequency plane wave incident upon a semi‐infinite elastic plate, such as an Arctic ice lend or free edge, using the Wiener‐Hopf method. By low‐frequency it is meant that the elastic properties of the plate are adequately described by the thin plate equation. For example, in a floating ice sheet, this translates into frequency‐ice thickness products that are ≲ 150. A key issue here is the fluid loading pertaining to sea ice and low‐frequency acoustics, which cannot be characterized by simplifying heavy or light fluid loading limits. An approximation to the exact kernel of the Wiener‐Hopf functional equation is used here, which is valid in this midrange fluid loading regime. The farfield diffracted pressure is found, which includes a fluid‐loaded, sub‐sonic (relative to the water) flexural wave in the ice plate. Comparisons are also made with the locally reacting approximation to the input impedance of an ice plate. The combined effects of the ice lead diffraction process represent loss mechanisms that contribute to the transmission loss in long‐range Arctic acoustic propagation.

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A self‐consistent theory of wave propagation and scattering through weakly inhomogeneous media

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The Journal of the Acoustical Society of America 2005年第S1期85卷 S70-S70页

作者： Dajun Tang George V. Frisk MIT/WHOI Joint Program in Oceanography/Oceanographic Engineering Department of Ocean Engineering Massachusetts Institute of Technology Cambridge MA 02139 Department of Ocean Engineering Woods Hole Oceanographic Institution Woods Hole MA 02543

A unified perturbation approach to wave propagation and scattering in weakly inhomogeneous media is presented. By separating the total wave field into an averaged coherent propagation part and a random scattering part, a set of coupled wave equations is found. The problem of a wave propagating in a random medium is changed to a problem of a pair of coupled waves propagating in a deterministic medium with randomly distributed sources. This method not only improves upon the conventional Born approximation for the scattered field, but also gives the attenuation behavior of the coherent propagating field related to the statistics of the random media. Examples of underwater acoustic waves in an inhomogeneous water column and an inhomogeneous bottom are given.

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An integral equation approach to range‐dependent boundary value problems in ocean acoustics

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The Journal of the Acoustical Society of America 2005年第S1期83卷 S117-S117页

作者： Peter H. Dahl George V. Frisk MIT/WHOI Joint Program in Oceanography/Oceanographic Engineering Woods Hole Oceanographic Institution Woods Hole MA 02543 Department of Ocean Engineering Woods Hole Oceanographic Institution Woods Hole MA 02543

In ocean acoustics, the introduction of range discontinuities, for example, the water‐to‐ice canopy surface, creates a mixed boundary value problem. In this paper, an exact solution of certain mixed boundary value problems is discussed using the Wiener‐Hopf method. A key attribute of this approach is that it is not fundamentally numerical in nature and allows additional insight into the mathematical and physical structure of the acoustic field due to range discontinuities. The problem discussed here is a canonical one: A plane wave is incident upon a planar surface where the boundary condition changes from Dirichlet (free surface) to Neumann (hard). The boundary conditions addressed in this problem are highly idealized renditions of what happens, when, say, a plane wave is incident upon a water‐to‐ice canopy surface; nevertheless, important features of the diffraction process are produced here, and the solution gives considerable insight into the process. The solution of the diffracted potential is partitioned into two components: a field consisting of cylindrical waves weighted by a polar gain function, resulting from the artificial source created by the discontinuity in the boundary; and a field containing a residue contribution which restores field continuity along the line corresponding to specular reflection. Contour plots of equal pressure amplitude show how the component fields superimpose such that the boundary conditions are maintained, and how energy is redistributed across the angular spectrum in the diffraction process. The latter is related to mode coupling due to boundary changes in waveguide problems. [Work supported by ONR.]

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