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  • 1
    Online Resource
    Online Resource
    Annual and Interannual Variability in the California Current System: Comparison of an Ocean State Estimate with a Network of Underwater Gliders
    American Meteorological Society ; 2018
    In:  Journal of Physical Oceanography Vol. 48, No. 12 ( 2018-12), p. 2965-2988
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 48, No. 12 ( 2018-12), p. 2965-2988
    Abstract: A data-constrained state estimate of the southern California Current System (CCS) is presented and compared with withheld California Cooperative Oceanic Fisheries Investigations (CalCOFI) data and assimilated glider data over 2007–17. The objective of this comparison is to assess the ability of the California State Estimate (CASE) to reproduce the key physical features of the CCS mean state, annual cycles, and interannual variability along the three sections of the California Underwater Glider Network (CUGN). The assessment focuses on several oceanic metrics deemed most important for characterizing physical variability in the CCS: 50-m potential temperature, 80-m salinity, and 26 kg m −3 isopycnal depth and salinity. In the time mean, the CASE reproduces large-scale thermohaline and circulation structures, including observed temperature gradients, shoaling isopycnals, and the locations and magnitudes of the equatorward California Current and poleward California Undercurrent. With respect to the annual cycle, the CASE captures the phase and, to a lesser extent, the magnitude of upper-ocean warming and stratification from late summer to early fall and of isopycnal heave during springtime upwelling. The CASE also realistically captures near-surface diapycnal mixing during upwelling season and the semiannual cycle of the California Undercurrent. In terms of interannual variability, the most pronounced signals are the persistent warming and downwelling anomalies of 2014–16 and a positive isopycnal salinity anomaly that peaked with the 2015–16 El Niño.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-18-0037.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2018
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  • 2
    Online Resource
    Online Resource
    Volume and Heat Budgets in the Coastal California Current System: Means, Annual Cycles, and Interannual Anomalies of 2014–16
    American Meteorological Society ; 2020
    In:  Journal of Physical Oceanography Vol. 50, No. 5 ( 2020-05), p. 1435-1453
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 50, No. 5 ( 2020-05), p. 1435-1453
    Abstract: The data-assimilating California State Estimate (CASE) enables the explicit evaluation of spatiotemporally varying volume and heat budgets in the coastal California Current System (CCS). An analysis of over 10 years of CASE model output (2007–17) diagnoses the physical drivers of the CCS mean state, annual cycles, and the 2014–16 temperature anomalies associated with a marine heat wave and an El Niño event. The largest terms in the mean mixed layer (from−50 to 0 m) volume budgets are upward vertical transport at the coast and offshore-flowing ageostrophic Ekman transport at the surface, the two branches of the coastal upwelling overturning cell. Contributions from onshore geostrophic flow in the Southern California Bight and alongshore geostrophic convergence in the central CCS balance the mean volume budgets. The depth-dependent annual cycle of vertical velocity exhibits the strongest upward velocity between −40- and −30-m depth in April. Interannual volume budgets show that over 50% of the 2013.5–16.5 time period experienced downwelling anomalies, which were balanced predominantly by alongshore transport convergence and, less often, by onshore transport anomalies. Mixed layer temperature anomalies persisted for the entirety of 2014–16, reaching a maximum of +3° in October 2015. The mixed layer heat budget shows that intermittent high air–sea heat flux anomalies and alongshore and vertical heat advection anomalies all contributed to warming during 2014–16. A subsurface (from −210 to −100 m) heat budget reveals that in September 2015 anomalous poleward heat advection into the Southern California Bight by the California Undercurrent caused deeper warming during the 2015/16 El Niño.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-19-0271.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2020
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  • 3
    Online Resource
    Online Resource
    Cyclonic Eddies in the Gulf of Mexico: Observations by Underwater Gliders and Simulations by Numerical Model
    American Meteorological Society ; 2015
    In:  Journal of Physical Oceanography Vol. 45, No. 1 ( 2015-01), p. 313-326
    Details
    In: Journal of Physical Oceanography, American Meteorological Society, Vol. 45, No. 1 ( 2015-01), p. 313-326
    Abstract: Circulation in the Gulf of Mexico (GoM) is dominated by the Loop Current (LC) and by Loop Current eddies (LCEs) that form at irregular multimonth intervals by separation from the LC. Comparatively small cyclonic eddies (CEs) are thought to have a controlling influence on the LCE, including its separation from the LC. Because the CEs are so dynamic and short-lived, lasting only a few weeks, they have proved a challenge to observe. This study addresses that challenge using underwater gliders. These gliders’ data and satellite sea surface height (SSH) are used in a four-dimensional variational (4DVAR) assimilation in the Massachusetts Institute of Technology (MIT) general circulation model (MITgcm). The model serves two purposes: first, the model’s estimate of ocean state allows the analysis of four-dimensional fields, and second, the model forecasts are examined to determine the value of glider data. CEs have a Rossby number of about 0.2, implying that the effects of flow curvature, cyclostrophy, to modify the geostrophic momentum balance are slight. The velocity field in CEs is nearly depth independent, while LCEs are more baroclinic, consistent with the CEs origin on the less stratified, dense side of the LCE. CEs are formed from water in the GoM, rather than the Atlantic water that distinguishes the LCE. Model forecasts are improved by glider data, using a quality metric based on satellite SSH, with the best 2-month GoM forecast rivaling the accuracy of a global hindcast.
    Type of Medium: Online Resource
    ISSN: 0022-3670 , 1520-0485
    URL: Article
    DOI: 10.1175/JPO-D-14-0138.1
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2015
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  • 4
    Online Resource
    Online Resource
    The SPICEX (Spice Experiment) component of the 2004 North Pacific Acoustic Laboratory (NPAL) experiment: An overview
    Acoustical Society of America (ASA) ; 2006
    In:  The Journal of the Acoustical Society of America Vol. 120, No. 5_Supplement ( 2006-11-01), p. 3020-3020
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 120, No. 5_Supplement ( 2006-11-01), p. 3020-3020
    Abstract: The objectives of the SPICEX component of the 2004 North Pacific Acoustic Laboratory (NPAL) experiment were (i) to elucidate the relative roles of internal waves, ocean spice, and internal tides in causing acoustic fluctuations; (ii) to understand the acoustic scattering far into the geometric shadow zone beneath caustics previously seen on bottom-mounted SOSUS receivers (shadow-zone arrivals); and (iii) to explore the range dependence of the fluctuation statistics. Two vertical line array receivers deployed in close proximity in the central North Pacific Ocean, together spanning much of the water column, recorded transmissions from broadband 250-Hz sources moored at the sound channel axis (750 m) and at surface conjugate depth (3000 m) at ranges of 500 and 1000 km from June through November 2004. Extensive environmental measurements were made along the acoustic path. The acoustic data from SPICEX reveal the vertical structure of the deep shadow zone arrivals. Internal waves are able to account for much of the observed vertical scattering in the reception finale, but other mechanisms seem necessary to account for the early shadow zone arrivals. Receptions from the abyssal sources show scattering occurring predominantly along the acoustic time fronts, as previously suggested by simulations, rather than across them.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4787093
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2006
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  • 5
    Online Resource
    Online Resource
    Mean, Annual, and Interannual Circulation and Volume Transport in the Western Tropical North Pacific From the Western Pacific Ocean State Estimates (WPOSE)
    American Geophysical Union (AGU) ; 2022
    In:  Journal of Geophysical Research: Oceans Vol. 127, No. 6 ( 2022-06)
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 127, No. 6 ( 2022-06)
    Abstract: Volume transport variability was greatest equatorward of 8°N, at the intersection of North and South Pacific currents Subthermocline (lower‐layer) interannual volume transport anomalies were of the same magnitude of those of the thermocline (upper‐layer) Interannual volume transport anomalies in the western tropical North Pacific increased before the mature 2015/2016 El Niño event
    Type of Medium: Online Resource
    ISSN: 2169-9275 , 2169-9291
    URL: Article
    DOI: 10.1029/2021JC018213
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2022
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    SSG: 16,13
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  • 6
    Online Resource
    Online Resource
    Thermohaline structure in the California Current System: Observations and modeling of spice variance : THERMOHALINE STRUCTURE OFF CALIFORNIA
    American Geophysical Union (AGU) ; 2012
    In:  Journal of Geophysical Research: Oceans Vol. 117, No. C2 ( 2012-02), p. n/a-n/a
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 117, No. C2 ( 2012-02), p. n/a-n/a
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2011JC007589
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2012
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    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Comparison of 4DVAR and EnKF state estimates and forecasts in the Gulf of Mexico
    Wiley ; 2019
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 145, No. 721 ( 2019-04), p. 1354-1376
    Details
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 145, No. 721 ( 2019-04), p. 1354-1376
    Abstract: An experiment is conducted to compare four‐dimensional variational (4DVAR) and ensemble Kalman filter (EnKF) assimilation systems and their predictability in the Gulf of Mexico (GoM) using the Massachusetts Institute of Technology general circulation model (MITgcm). The quality of the ocean‐state estimates, forecasts, and the contribution of ensemble prediction are evaluated. The MITgcm–Estimating the Circulation and Climate of the Ocean (ECCO) 4DVAR (MITgcm–ECCO) and the MITgcm–Data Assimilation Research Testbed (DART) EnKF (MITgcm–DART) systems were used to compute two‐month hindcasts (March–April, 2010) by assimilating satellite‐derived along‐track sea‐surface height (SSH) and gridded sea‐surface temperature (SST) observations. The estimates from both methods at the end of the hindcast period were then used to initialize forecasts for two months (May–June, 2010). This period was selected because a loop current (LC) eddy (Eddy Franklin: Eddy‐F) detachment event occurred at the end of May 2010, immediately after the Deepwater Horizon (DwH) oil spill. Despite some differences between the setups, both systems produce analyses and forecasts of comparable quality and both solutions significantly outperformed model persistence. A reference forecast initialized from the 1/12° Hybrid Coordinate Ocean Model (HYCOM)/NCODA global analysis also performed well. The EnKF experiments for sensitivity to filter parameters showed enhanced predictability when using more ensemble members and stronger covariance localization, but not for larger inflation. The EnKF experiments varying the number of assimilation cycles showed enhanced short‐term (long‐term) predictability with fewer (more) assimilation cycles. Additional hindcast and forecast experiments at other times of significant LC evolution showed mixed performance of both systems, which depends strongly on the background state of the GoM circulation. The present work demonstrates a practical application of both assimilation methods for the GoM and compares them in a limited number of realizations. The overall conclusion showing improved short‐term (long‐term) predictability for EnKF (4DVAR) carries an important caveat that the results from this study are specific to a few 4DVAR and EnKF LC eddy separation experiments in the GoM and cannot be generalized to conclude the relative performance of both methods, especially in other applications. However, some of the concepts and methods should carry over to other applications.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    URL: Article
    DOI: 10.1002/qj.2019.145.issue-721
    DOI: 10.1002/qj.3493
    RVK:
    UA 1000
    RVK:
    UA 7650
    Language: English
    Publisher: Wiley
    Publication Date: 2019
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  • 8
    Online Resource
    Online Resource
    State estimates and forecasts of the loop current in the Gulf of Mexico using the MITgcm and its adjoint : State estimates and Forecasts in the GoM
    American Geophysical Union (AGU) ; 2013
    In:  Journal of Geophysical Research: Oceans Vol. 118, No. 7 ( 2013-07), p. 3292-3314
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 118, No. 7 ( 2013-07), p. 3292-3314
    Type of Medium: Online Resource
    ISSN: 2169-9275
    URL: Article
    DOI: 10.1002/jgrc.20239
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2013
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    detail.hit.zdb_id: 161667-5
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    SSG: 16,13
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  • 9
    Online Resource
    Online Resource
    The vertical structure of shadow-zone arrivals at long range in the ocean
    Acoustical Society of America (ASA) ; 2006
    In:  The Journal of the Acoustical Society of America Vol. 119, No. 5_Supplement ( 2006-05-01), p. 3344-3344
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 119, No. 5_Supplement ( 2006-05-01), p. 3344-3344
    Abstract: Multimegameter-range acoustic data obtained by bottom-mounted SOSUS receivers show significant acoustic energy penetrating several hundred meters into the geometric shadow zones below cusps in the predicted acoustic time fronts, much further than can be accounted for by diffraction [Dushaw et al., IEEE J. Oceanic Eng. 24, 202–214 (1999)]. Acoustic data from two vertical line array receivers deployed in close proximity in the North Pacific Ocean, together virtually spanning the water column, show similar shadow-zone arrivals for transmissions from broadband 250-Hz sources moored at the sound-channel axis (750 m) and at surface conjugate depth (3000 m) at ranges of 500 and 1000 km. The vertical structure of the receptions will be compared to parabolic equation propagation simulations for sound-speed fields constructed from high-resolution underway conductivity-temperature-depth (UCTD) data in the upper 400 m, widely spaced deep CTD casts, and climatological data. Predictions will be made (i) for the observed field; (ii) for a smoothed field, and (iii) for fields that include sound-speed fines structure due to density variations (internal waves) or due to density-compensated sound-speed variations (spice).
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4786449
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2006
    detail.hit.zdb_id: 1461063-2
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  • 10
    Online Resource
    Online Resource
    Poleward flows in the southern California Current System: Glider observations and numerical simulation
    American Geophysical Union (AGU) ; 2011
    In:  Journal of Geophysical Research Vol. 116, No. C2 ( 2011-02-17)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 116, No. C2 ( 2011-02-17)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2010JC006536
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2011
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    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
    Location Call Number Limitation Availability
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