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  • 1
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Es werden numerische Simulationen der Refraktion von Oberflächenwasserwellen (Dünungen), die zwischen Orkney- und Shetlandinseln bzw. Shetlandinseln und Norwegen in die Nordsee einlaufen, benutzt, um die Abweichungen der Laufzeit, Laufrichtung und die seitliche Verschiebung von sogenannten Strahlen, entlang denen die Wellen laufen, zu bestimmen, wenn man (1) Strahlen, bei denen keine Refraktion (Tiefwasser), wohl aber Shoaling berücksichtigt wurde mit Strahlen, bei denen beides berücksichtigt wurde, vergleicht, und wenn (2) zusätzlich die Einfallsrichtung und die Frequenz der Dünung variiert wird. Die Ergebnisse zeigen, daß die Refraktion von Dünungswellen wichtig ist und in numerischen Seegangsvorhersagemodellen berücksichtigt werden sollte. Für die betrachteten Fälle zeigt sich, daß die Unterschiede in der Laufzeit, Laufrichtung und der seitlichen Verschiebung größer sind als typische Werte von Zeitschritt, Gitterabstand und Richtungsauflösung, wie sie gegenwärtig in Seegangsvorhersagemodellen für Flachwasser benutzt werden.
    Abstract: Résumé Des simulations numériques de la réfraction de la houle qui entrent dans la mer du Nord par un passage entre les îles d'Orkney et les Shetlands et la Norwège permettent de determiner les erreurs sur le temps de parcours, la déflexion angulaire et le déplacement latéral des rayons (1) en tenant compte de la variation de la vitesse de groupe en fonction de la profondeur, mais en négligeant la réfraction des rayons en eau profonde et (2) en perturbant la fréquence initiale de la houle et sa direction incidente. Les résultats montrent que la réfraction en profondeur de la houle est importante et devrait être prise en compte correctement dans les modèles numériques de prédiction de houle. Les différences obtenues dans les cas considéres sur le temps de trajet, la déflexion angulaire et le déplacement latéral sont supérieures aux valeurs typiques des pas de temps et d'espace et de la résolution directionelle utilisés dans les modèles prédictifs de houle en eau peu profonde.
    Notes: Summary Numerical simulations of water wave refraction entering the North Sea between the Orkney-Shetland and Shetland-Norway are used to determine the expected errors in travel time, angular deflection and lateral displacement of ray paths when (1) accounting for shoaling but neglecting refraction effects in deep water ray characteristics and (2) perturbing the initial swell frequency and direction of incidence. The results show that depth refraction of swell waves is important and should properly be accounted for in numerical wave prediction models. It is shown that for the cases considered here, differences in travel time, angular deflection and lateral displacement exceed typical values for time step, grid spacing and directional resolution presently used in shallow water wave prediction models.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Ocean dynamics 44 (1991), S. 1-15 
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Es werden numerische Simulationen der Transformation von Meereswellen durch Shoaling und Refraktion benutzt, um die Verteilung der Energie, mittleren Frequenz und Richtung der Wellen entlang der Nordseeküste zu untersuchen. Es werden die Veränderungen der Richtungsverteilung im Fall von Dünungen, die in die Nordsee zwischen Orkney- und Shetlandinseln bzw. Shetlandinseln und Norwegen eintreten mit Hilfe einer rückwärtsgerichteten Strahlenprojektion berechnet. Die Ergebnisse zeigen, daß dieDeutsche Bucht die Nordsee bezüglich des Seegangsklimas an den Küsten und der Verteilung der Dünungsrichtungen in ein nördliches und ein südliches Gebiet teilt und dafür sorgt, daß das Elbe- und Weserästuar vor hohen Dünungswellen aus dem Nordatlantik geschützt wird, vorausgesetzt, daß keine zusätzlichen Wellen durch lokale Windfelder in der Nordsee erzeugt werden. Die hier benutzte Methode erlaubt eine wirklichkeitsnähere Beschreibung des Seegangsklimas an den Küsten, als es bisher mit den herkömmlichen Methoden möglich war. Ferner zeigt sich, daß die örtliche Variabilität der mittleren spektralen Parameter beträchtlich ist und von den topographischen Merkmalen des Meeresbodens sowohl in der Nah- als auch in der Fernzone abhängt.
    Abstract: Résumé Des simulations numériques de la transformation des vagues liée à la variation de la vitesse de groupe en fonction de la profondeur permettent d'étudier le spectre d'énergie de la houle, sa fréquence et sa direction moyennes le long de la côte. Les distributions angulaires des houles typiques, qui entrent dans la mer du Nord par un passage entre les îles d'Orkney et les Shetlands et entre les Shetlands et la Norwège, sont calculées par rétroprojection des rayons. Les résultats montrent que leGerman Bight sépare dans une direction Nord-Sud deux domaines de houles côtières caractéristiques. Il permet de protéger les estuaires de l'Elbe et du Weser des hautes mers avec des houles de l'Atlantique Nord lorsque la géneration de la houle par les vents locaux est négligeable. Cette approche permet d'obtenir une description plus réaliste des caractéristiques des houles côtières que celle que l'on obtiendrait par des méthodes plus conventionnelles. Par ailleurs, on trouve que la distribution spectrale des différents paramètres varie considérablement avec la position et dépend de la topographie proche et lointaine.
    Notes: Summary Numerical simulations of surface wave transformation due to shoaling and refraction are used to examine the distribution of wave energy, mean frequency, and direction along the coastline of the north Sea. The variability in the directional distribution of typical swell events, entering the North Sea between the Orkney-Shetland and Shetland-Norway, are calculated from reverse ray projections. The results show that theGerman Bight divides the coastal wave climate and the directional characteristics of swell into a northern and southern domain and provides shelter to the Elbe and Weser estuaries from high sea states associated with swell from the North Atlantic when generation of waves from local winds in the North Sea is negligible. This approach provides a more realistic description of the costal were climate than has been possible with conventional techniques. Furthermore, it was found that the spatial variability in mean spectral parameters is considerable and depends on both near and far zone topographic features.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2022-05-25
    Description: Author Posting. © Oceanography Society, 2007. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 20, 4 (2007): 156-167.
    Description: Since the end of the Cold War, the US Navy has had an increasing interest in continental shelves and slopes as operational areas. To work in such areas requires a good understanding of ocean acoustics, coastal physical oceanography, and, in the modern era, autonomous underwater vehicle (AUV) operations.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 4
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 123(12), (2018): 8674-8687, doi:10.1002/2018JC013766.
    Description: A large collaborative program has studied the coupled air‐ice‐ocean‐wave processes occurring in the Arctic during the autumn ice advance. The program included a field campaign in the western Arctic during the autumn of 2015, with in situ data collection and both aerial and satellite remote sensing. Many of the analyses have focused on using and improving forecast models. Summarizing and synthesizing the results from a series of separate papers, the overall view is of an Arctic shifting to a more seasonal system. The dramatic increase in open water extent and duration in the autumn means that large surface waves and significant surface heat fluxes are now common. When refreezing finally does occur, it is a highly variable process in space and time. Wind and wave events drive episodic advances and retreats of the ice edge, with associated variations in sea ice formation types (e.g., pancakes, nilas). This variability becomes imprinted on the winter ice cover, which in turn affects the melt season the following year.
    Description: This program was supported by the Office of Naval Research, Code 32, under Program Managers Scott Harper and Martin Jeffries. The crew of R/V Sikuliaq provide outstanding support in collecting the field data, and the US National Ice Center, German Aerospace Center (DLR), and European Space Agency facilitated the remote sensing collections and daily analysis products. RADARSAT‐2 Data and Products are from MacDonald, Dettwiler, and Associates Ltd., courtesy of the U.S. National Ice Center. Data, supporting information, and a cruise report can be found at http://www.apl.uw.edu/arcticseastate
    Keywords: Arctic ; waves ; autumn ; sea ice ; Beaufort ; flux
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Elementa Science of the Anthropocene 5 (2017): 40, doi:10.1525/elementa.232.
    Description: Breakup of the near-continuous winter sea ice into discrete summer ice floes is an important transition that dictates the evolution and fate of the marginal ice zone (MIZ) of the Arctic Ocean. During the winter of 2014, more than 50 autonomous drifting buoys were deployed in four separate clusters on the sea ice in the Beaufort Sea, as part of the Office of Naval Research MIZ program. These systems measured the ocean-ice-atmosphere properties at their location whilst the sea ice parameters in the surrounding area of these buoy clusters were continuously monitored by satellite TerraSAR-X Synthetic Aperture Radar. This approach provided a unique Lagrangian view of the winter-to-summer transition of sea ice breakup and floe size distribution at each cluster between March and August. The results show the critical timings of a) temporary breakup of winter sea ice coinciding with strong wind events and b) spring breakup (during surface melt, melt ponding and drainage) leading to distinctive summer ice floes. Importantly our results suggest that summer sea ice floe distribution is potentially affected by the state of winter sea ice, including the composition and fracturing (caused by deformation events) of winter sea ice, and that substantial mid-summer breakup of sea ice floes is likely linked to the timing of thermodynamic melt of sea ice in the area. As the rate of deformation and thermodynamic melt of sea ice has been increasing in the MIZ in the Beaufort Sea, our results suggest that these elevated factors would promote faster and more enhanced breakup of sea ice, leading to a higher melt rate of sea ice and thus a more rapid advance of the summer MIZ.
    Description: Funding was provided by the Office of Naval Research (grants N00014-12-1-0359, N00014-12-1-0448) as part of the Marginal Ice Zone, Department Research Initiative, ONR MIZ, by the UK Natural Environment Research Council (grants NE/M00600X/1, NE/L012707/1).
    Keywords: Sea ice ; Breakup ; Floe size distribution ; Marginal ice zone ; Arctic
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 521 (2015): 65-69, doi:10.1038/nature14399.
    Description: Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and the turbulent mixing caused by their breaking, they impact a panoply of ocean processes, such as the supply of nutrients for photosynthesis1, sediment and pollutant transport2 and acoustic transmission3; they also pose hazards for manmade structures in the ocean4. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking5, posing severe challenges for their observation and their inclusion in numerical climate models, which are sensitive to their effects6-7. Over a decade of studies8-11 have targeted the South China Sea, where the oceans’ most powerful internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their generation mechanism, variability and energy budget, however, due to the lack of in-situ data from the Luzon Strait, where extreme flow conditions make measurements challenging. Here we employ new observations and numerical models to (i) show that the waves begin as sinusoidal disturbances rather than from sharp hydraulic phenomena, (ii) reveal the existence of 〉200-m-high breaking internal waves in the generation region that give rise to turbulence levels 〉10,000 times that in the open ocean, (iii) determine that the Kuroshio western boundary current significantly refracts the internal wave field emanating from the Luzon Strait, and (iv) demonstrate a factor-of-two agreement between modelled and observed energy fluxes that enables the first observationally-supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.
    Description: Our work was supported by the U.S. Office of Naval Research and the Taiwan National Science Council.
    Description: 2015-10-29
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 7
    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Elementa Science of the Anthropocene 5 (2017): 55, doi:10.1525/elementa.241.
    Description: The interplay between sea ice concentration, sea ice roughness, ocean stratification, and momentum transfer to the ice and ocean is subject to seasonal and decadal variations that are crucial to understanding the present and future air-ice-ocean system in the Arctic. In this study, continuous observations in the Canada Basin from March through December 2014 were used to investigate spatial differences and temporal changes in under-ice roughness and momentum transfer as the ice cover evolved seasonally. Observations of wind, ice, and ocean properties from four clusters of drifting instrument systems were complemented by direct drill-hole measurements and instrumented overhead flights by NASA operation IceBridge in March, as well as satellite remote sensing imagery about the instrument clusters. Spatially, directly estimated ice-ocean drag coefficients varied by a factor of three with rougher ice associated with smaller multi-year ice floe sizes embedded within the first-year-ice/multi-year-ice conglomerate. Temporal differences in the ice-ocean drag coefficient of 20–30% were observed prior to the mixed layer shoaling in summer and were associated with ice concentrations falling below 100%. The ice-ocean drag coefficient parameterization was found to be invalid in September with low ice concentrations and small ice floe sizes. Maximum momentum transfer to the ice occurred for moderate ice concentrations, and transfer to the ocean for the lowest ice concentrations and shallowest stratification. Wind work and ocean work on the ice were the dominant terms in the kinetic energy budget of the ice throughout the melt season, consistent with free drift conditions. Overall, ice topography, ice concentration, and the shallow summer mixed layer all influenced mixed layer currents and the transfer of momentum within the air-ice-ocean system. The observed changes in momentum transfer show that care must be taken to determine appropriate parameterizations of momentum transfer, and imply that the future Arctic system could become increasingly seasonal.
    Description: The deployment of the ITP-Vs and the subsequent analysis effort was supported by the Office of Naval Research under grants N00014-12-10140 and N00014-12-10799.
    Keywords: Arctic ocean ; Ice-ocean boundary layer ; Momentum transfer 
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
    Publication Date: 2022-11-10
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in [citation], doi:[doi]. Gommenginger, C., Chapron, B., Hogg, A., Buckingham, C., Fox-Kemper, B., Eriksson, L., Soulat, F., Ubelmann, C., Ocampo-Torres, F., Nardelli, B. B., Griffin, D., Lopez-Dekker, P., Knudsen, P., Andersen, O., Stenseng, L., Stapleton, N., Perrie, W., Violante-Carvalho, N., Schulz-Stellenfleth, J., Woolf, D., Isern-Fontanet, J., Ardhuin, F., Klein, P., Mouche, A., Pascual, A., Capet, X., Hauser, D., Stoffelen, A., Morrow, R., Aouf, L., Breivik, O., Fu, L., Johannessen, J. A., Aksenov, Y., Bricheno, L., Hirschi, J., Martin, A. C. H., Martin, A. P., Nurser, G., Polton, J., Wolf, J., Johnsens, H., Soloviev, A., Jacobs, G. A., Collard, F., Groom, S., Kudryavtsev, V., Wilkin, J., Navarro, V., Babanin, A., Martin, M., Siddorn, J., Saulter, A., Rippeth, T., Emery, B., Maximenko, N., Romeiser, R., Graber, H., Azcarate, A. A., Hughes, C. W., Vandemark, D., da Silva, J., Van Leeuwen, P. J., Naveira-Garabato, A., Gemmrich, J., Mahadevan, A., Marquez, J., Munro, Y., Doody, S., & Burbidge, G. SEASTAR: A mission to study ocean submesoscale dynamics and small-scale atmosphere-ocean processes in coastal, shelf and polar seas. Frontiers in Marine Science, 6, (2019):457, doi:10.3389/fmars.2019.00457.
    Description: High-resolution satellite images of ocean color and sea surface temperature reveal an abundance of ocean fronts, vortices and filaments at scales below 10 km but measurements of ocean surface dynamics at these scales are rare. There is increasing recognition of the role played by small scale ocean processes in ocean-atmosphere coupling, upper-ocean mixing and ocean vertical transports, with advanced numerical models and in situ observations highlighting fundamental changes in dynamics when scales reach 1 km. Numerous scientific publications highlight the global impact of small oceanic scales on marine ecosystems, operational forecasts and long-term climate projections through strong ageostrophic circulations, large vertical ocean velocities and mixed layer re-stratification. Small-scale processes particularly dominate in coastal, shelf and polar seas where they mediate important exchanges between land, ocean, atmosphere and the cryosphere, e.g., freshwater, pollutants. As numerical models continue to evolve toward finer spatial resolution and increasingly complex coupled atmosphere-wave-ice-ocean systems, modern observing capability lags behind, unable to deliver the high-resolution synoptic measurements of total currents, wind vectors and waves needed to advance understanding, develop better parameterizations and improve model validations, forecasts and projections. SEASTAR is a satellite mission concept that proposes to directly address this critical observational gap with synoptic two-dimensional imaging of total ocean surface current vectors and wind vectors at 1 km resolution and coincident directional wave spectra. Based on major recent advances in squinted along-track Synthetic Aperture Radar interferometry, SEASTAR is an innovative, mature concept with unique demonstrated capabilities, seeking to proceed toward spaceborne implementation within Europe and beyond.
    Description: CG and AM received funding from the United Kingdom Centre for Earth Observation Instrumentation SEASTAR+ project (Contract No. RP10G0435A02). PVL was supported by the European Research Council (ERC) CUNDA project 694509 under the European Union Horizon 2020 Research and Innovation Program.
    Keywords: Satellite ; Air sea interactions ; Upper ocean dynamics ; Submesoscale ; Coastal ; Marginal ice zone ; Radar ; Along-track interferometry
    Repository Name: Woods Hole Open Access Server
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  • 9
    Publication Date: 2022-10-10
    Description: Unprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in MacKinnon, J. A., Simmons, H. L., Hargrove, J., Thomson, J., Peacock, T., Alford, M. H., Barton, B., Boury, S., Brenner, S. D., Couto, N., Danielson, S. L., Fine, E. C., Graber, H. C., Guthrie, J., Hopkins, J. E., Jayne, S. R., Jeon, C., Klenz, T., Lee, C. M., Lenn, Y-D., Lucas, A. J., Lund, B., Mahaffey, C., Norman, L., Rainville, L., Smith, M. M., Thomas, L. N., Torres-Valdés, S., & Wood, K. R. A warm jet in a cold ocean. Nature Communications, 12(1), (2021): 2418, https://doi.org/10.1038/s41467-021-22505-5.
    Description: Unprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.
    Description: Support for this work was provided by the US Office of Naval Research Stratified Ocean Dynamics of the Arctic program (grant numbers N000141512903, N000141612378, N000141612377, N000141612379, N0001416123450, N000141612360, N000141612349, N000141812007, N000141812475, and N000141912514). Additional support for biogeochemistry sampling was provided by UK (NERC) and Germany (BMBF) through the Changing Arctic Ocean Program’s ARISE (NE/P006035/1, NE/P006000/2), PEANUTS (NE/R01275X/1, NE/R012547/2, and BMBF 03F0804) projects and the UK-France PhD program DGA/Dstl. Float deployments and hydrographic data compilations were supported in part by North Pacific Research Board grants A91-99a and A91-00a. The deployment of autonomous ocean profilers was supported by ONR, NOAA Research, and the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement NA15OAR4320063.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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