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  • 1
    Online Resource
    Online Resource
    Submesoscale dispersion in the vicinity of the Deepwater Horizon spill
    Proceedings of the National Academy of Sciences ; 2014
    In:  Proceedings of the National Academy of Sciences Vol. 111, No. 35 ( 2014-09-02), p. 12693-12698
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 111, No. 35 ( 2014-09-02), p. 12693-12698
    Abstract: Reliable forecasts for the dispersion of oceanic contamination are important for coastal ecosystems, society, and the economy as evidenced by the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 and the Fukushima nuclear plant incident in the Pacific Ocean in 2011. Accurate prediction of pollutant pathways and concentrations at the ocean surface requires understanding ocean dynamics over a broad range of spatial scales. Fundamental questions concerning the structure of the velocity field at the submesoscales (100 m to tens of kilometers, hours to days) remain unresolved due to a lack of synoptic measurements at these scales. Using high-frequency position data provided by the near-simultaneous release of hundreds of accurately tracked surface drifters, we study the structure of submesoscale surface velocity fluctuations in the Northern Gulf of Mexico. Observed two-point statistics confirm the accuracy of classic turbulence scaling laws at 200-m to 50-km scales and clearly indicate that dispersion at the submesoscales is local, driven predominantly by energetic submesoscale fluctuations. The results demonstrate the feasibility and utility of deploying large clusters of drifting instruments to provide synoptic observations of spatial variability of the ocean surface velocity field. Our findings allow quantification of the submesoscale-driven dispersion missing in current operational circulation models and satellite altimeter-derived velocity fields.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1402452111
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2014
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 2
    Online Resource
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    Data assimilation considerations for improved ocean predictability during the Gulf of Mexico Grand Lagrangian Deployment (GLAD)
    Elsevier BV ; 2014
    In:  Ocean Modelling Vol. 83 ( 2014-11), p. 98-117
    Details
    In: Ocean Modelling, Elsevier BV, Vol. 83 ( 2014-11), p. 98-117
    Type of Medium: Online Resource
    ISSN: 1463-5003
    URL: Article
    DOI: 10.1016/j.ocemod.2014.09.003
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2014
    detail.hit.zdb_id: 1126496-2
    detail.hit.zdb_id: 1498544-5
    SSG: 14
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  • 3
    Online Resource
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    Surface Ocean Mixing Inferred from Different Multisatellite Altimetry Measurements
    American Meteorological Society ; 2010
    In:  Journal of Physical Oceanography Vol. 40, No. 11 ( 2010-11-01), p. 2466-2480
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 40, No. 11 ( 2010-11-01), p. 2466-2480
    Abstract: Two sea surface height (SSH) anomaly fields distributed by Archiving, Validation, and Interpretation of Satellite Oceanographic (AVISO) Altimetry are evaluated in terms of the effects that they produce on mixing. One SSH anomaly field, tagged REF, is constructed using measurements made by two satellite altimeters; the other SSH anomaly field, tagged UPD, is constructed using measurements made by up to four satellite altimeters. Advection is supplied by surface geostrophic currents derived from the total SSH fields resulting from the addition of these SSH anomaly fields to a mean SSH field. Emphasis is placed on the extraction from the currents of Lagrangian coherent structures (LCSs), which, acting as skeletons for patterns formed by passively advected tracers, entirely control mixing. The diagnostic tool employed to detect LCSs is provided by the computation of finite-time Lyapunov exponents. It is found that currents inferred using UPD SSH anomalies support mixing with characteristics similar to those of mixing produced by currents inferred using REF SSH anomalies. This result mainly follows from the fact that, being more easily characterized as chaotic than turbulent, mixing as sustained by currents derived using UPD SSH anomalies is quite insensitive to spatiotemporal truncations of the advection field.
    Type of Medium: Online Resource
    ISSN: 1520-0485 , 0022-3670
    URL: Article
    DOI: 10.1175/2010JPO4458.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2010
    detail.hit.zdb_id: 2042184-9
    detail.hit.zdb_id: 184162-2
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  • 4
    Online Resource
    Online Resource
    Objective Detection of Oceanic Eddies and the Agulhas Leakage
    American Meteorological Society ; 2013
    In:  Journal of Physical Oceanography Vol. 43, No. 7 ( 2013-07-01), p. 1426-1438
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 43, No. 7 ( 2013-07-01), p. 1426-1438
    Abstract: Mesoscale oceanic eddies are routinely detected from instantaneous velocities derived from satellite altimetry data. While simple to implement, this approach often gives spurious results and hides true material transport. Here it is shown how geodesic transport theory, a recently developed technique from nonlinear dynamical systems, uncovers eddies objectively. Applying this theory to altimetry-derived velocities in the South Atlantic reveals, for the first time, Agulhas rings that preserve their material coherence for several months, while ring candidates yielded by other approaches tend to disperse or leak within weeks. These findings suggest that available velocity-based estimates for the Agulhas leakage, as well as for its impact on ocean circulation and climate, need revision.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-12-0171.1
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
    detail.hit.zdb_id: 2042184-9
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  • 5
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    Tracking the H ercules 265 marine gas well blowout in the G ulf of M exico
    American Geophysical Union (AGU) ; 2016
    In:  Journal of Geophysical Research: Oceans Vol. 121, No. 1 ( 2016-01), p. 706-724
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 121, No. 1 ( 2016-01), p. 706-724
    Abstract: Atmospheric and surface water circulations were modeled Combustion byproducts were found in sediments and fishes after Hercules 265 rig blowout Baseline contamination levels are imperative for environmental impact studies
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Issue
    URL: Article
    DOI: 10.1002/jgrc.v121.1
    DOI: 10.1002/2015JC011037
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2016
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    detail.hit.zdb_id: 3094219-6
    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    Enduring Lagrangian coherence of a Loop Current ring assessed using independent observations
    Springer Science and Business Media LLC ; 2018
    In:  Scientific Reports Vol. 8, No. 1 ( 2018-07-26)
    Details
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 8, No. 1 ( 2018-07-26)
    Abstract: Ocean flows are routinely inferred from low-resolution satellite altimetry measurements of sea surface height assuming a geostrophic balance. Recent nonlinear dynamical systems techniques have revealed that surface currents derived from altimetry can support mesoscale eddies with material boundaries that do not filament for many months, thereby representing effective transport mechanisms. However, the long-range Lagrangian coherence assessed for mesoscale eddy boundaries detected from altimetry is constrained by the impossibility of current altimeters to resolve ageostrophic submesoscale motions. These may act to prevent Lagrangian coherence from manifesting in the rigorous form described by the nonlinear dynamical systems theories. Here we use a combination of satellite ocean color and surface drifter trajectory data, rarely available simultaneously over an extended period of time, to provide observational evidence for the enduring Lagrangian coherence of a Loop Current ring detected from altimetry. We also seek indications of this behavior in the flow produced by a data-assimilative system which demonstrated ability to reproduce observed relative dispersion statistics down into the marginally submesoscale range. However, the simulated flow, total surface and subsurface or subsampled emulating altimetry, is not found to support the long-lasting Lagrangian coherence that characterizes the observed ring. This highlights the importance of the Lagrangian metrics produced by the nonlinear dynamical systems tools employed here in assessing model performance.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    URL: Article
    DOI: 10.1038/s41598-018-29582-5
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
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  • 7
    Online Resource
    Online Resource
    Statistics of Simulated and Observed Pair Separations in the Gulf of Mexico
    American Meteorological Society ; 2016
    In:  Journal of Physical Oceanography Vol. 46, No. 7 ( 2016-07), p. 2183-2199
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 46, No. 7 ( 2016-07), p. 2183-2199
    Abstract: Pair-separation statistics of in situ and synthetic surface drifters deployed near the Deepwater Horizon site in the Gulf of Mexico are investigated. The synthetic trajectories derive from a 1-km-resolution data-assimilative Navy Coastal Ocean Model (NCOM) simulation. The in situ drifters were launched in the Grand Lagrangian Deployment (GLAD). Diverse measures of the dispersion are calculated and compared to theoretical predictions. For the NCOM pairs, the measures indicate nonlocal pair dispersion (in which pair separations grow exponentially in time) at the smallest sampled scales. At separations exceeding 100 km, pair motion is uncorrelated, indicating absolute rather than relative dispersion. With the GLAD drifters, however, the statistics are ambiguous, with some indicating local dispersion (in which pair separations exhibit power-law growth) and others suggesting nonlocal dispersion. The difference between the two datasets stems in part from inertial oscillations, which affect the energy levels at small scales without greatly altering pair dispersion. These were significant in GLAD but much weaker in the NCOM simulation. In addition, the GLAD drifters were launched over a limited geographical area, producing few independent realizations and hence lower statistical significance. Restricting the NCOM set to pairs launched at the same locations yields very similar results, suggesting the model is for the most part capturing the observed dispersion.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-15-0127.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2016
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    detail.hit.zdb_id: 184162-2
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  • 8
    Online Resource
    Online Resource
    Persistent Lagrangian Transport Patterns in the Northwestern Gulf of Mexico
    American Meteorological Society ; 2019
    In:  Journal of Physical Oceanography Vol. 49, No. 2 ( 2019-02), p. 353-367
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 49, No. 2 ( 2019-02), p. 353-367
    Abstract: Persistent Lagrangian transport patterns at the ocean surface are revealed from climatological Lagrangian coherent structures (cLCSs) computed from daily climatological surface current velocities in the northwestern Gulf of Mexico (NWGoM). The climatological currents are computed from daily velocities produced by an 18-yr-long free-running submesoscale-permitting Nucleus for European Modelling of the Ocean (NEMO) simulation of the Gulf of Mexico. Despite the intense submesoscale variability produced by the model along the shelf break, which is found to be consistent with observations and previous studies, a persistent mesoscale attracting barrier between the NWGoM shelf and the deep ocean is effectively identified by a hook-like pattern associated with persistent strongly attracting cLCSs. Simulated tracer and satellite-tracked drifters originating over the shelf tend to be trapped there by the hook-like pattern as they spread cyclonically. Tracers and drifters originating beyond the shelf tend to be initially attracted to the hook-like pattern as they spread anticyclonically and eventually over the deep ocean. The findings have important implications for the mitigation of contaminant accidents such as oil spills.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-17-0207.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2019
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    detail.hit.zdb_id: 184162-2
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  • 9
    Online Resource
    Online Resource
    Surface Pathways Connecting the South and North Atlantic Oceans
    American Geophysical Union (AGU) ; 2022
    In:  Geophysical Research Letters Vol. 49, No. 1 ( 2022-01-16)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 49, No. 1 ( 2022-01-16)
    Abstract: Surface pathways connecting the North Brazil Current and the tropical North Atlantic are identified from observational trajectories Observational surface drifter trajectories are discretized to a Markov chain and evaluated using transition path theory One pathway follows the traditional upper‐limb route through the Caribbean Sea and Gulf of Mexico and the other remains in the Atlantic
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2021GL096646
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 10
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    Zonal Jets as Meridional Transport Barriers in the Subtropical and Polar Lower Stratosphere
    American Meteorological Society ; 2012
    In:  Journal of the Atmospheric Sciences Vol. 69, No. 2 ( 2012-02-01), p. 753-767
    Details
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 69, No. 2 ( 2012-02-01), p. 753-767
    Abstract: Applications of recent results from dynamical systems theory to the study of transport and mixing in incompressible two-dimensional flows lead to the expectation that, independent of the background potential vorticity (PV) distribution, weakly perturbed zonal jets are associated with barriers that inhibit meridional transport. Here the authors provide evidence in support of this expectation based on the analysis of isentropic winds in the lower stratosphere as produced by the Canadian Middle Atmosphere Model (CMAM), a comprehensive general circulation model. Specifically, barriers to meridional transport are found to be associated with the (eastward) austral polar night jet, for which the meridional gradient of background PV is large, and also for the (westward) boreal summer subtropical jet, for which the background PV gradient is quite small. The identification of the meridional transport barriers is based on the computation of finite-time Lyapunov exponents (FTLEs), which characterize the amount of stretching about fluid particle trajectories. Being composed of regular fluid particle trajectories lying on invariant tori, the meridional transport barriers are identified with topologically circular, local minimizing curves or trenches of the backward-plus-forward FTLE field. Results from explicit passive tracer advection experiments and flux computations are also presented, which are consistent with results inferred using the FTLE diagnostic.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    URL: Article
    DOI: 10.1175/JAS-D-11-084.1
    RVK:
    UA 4800
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2012
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    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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