Wilkin
John L.
Wilkin
John L.
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ArticleInterannual variability of the surface summertime eastward jet in the South China Sea(John Wiley & Sons, 2014-10-27) Li, Yuanlong ; Han, Weiqing ; Wilkin, John L. ; Zhang, Weifeng G. ; Arango, Hernan G. ; Zavala-Garay, Javier ; Levin, Julia C. ; Castruccio, Frederic S.The summertime eastward jet (SEJ) located around 12°N, 110°E–113°E, as the offshore extension of the Vietnam coastal current, is an important feature of the South China Sea (SCS) surface circulation in boreal summer. Analysis of satellite-derived sea level and sea surface wind data during 1992–2012 reveals pronounced interannual variations in its surface strength (SSEJ) and latitudinal position (YSEJ). In most of these years, the JAS (July, August, and September)-mean SSEJ fluctuates between 0.17 and 0.55 m s−1, while YSEJ shifts between 10.7°N and 14.3°N. These variations of the SEJ are predominantly contributed from the geostrophic current component that is linked to a meridional dipole pattern of sea level variations. This sea level dipole pattern is primarily induced by local wind changes within the SCS associated with the El Niño-Southern Oscillation (ENSO). Enhanced (weakened) southwest monsoon at the developing (decaying) stage of an El Niño event causes a stronger (weaker) SEJ located south (north) of its mean position. Remote wind forcing from the tropical Pacific can also affect the sea level in the SCS via energy transmission through the Philippine archipelago, but its effect on the SEJ is small. The impact of the oceanic internal variability, such as eddy-current interaction, is assessed using an ocean general circulation model (OGCM). Such impact can lead to considerable year-to-year changes of sea level and the SEJ, equivalent to ∼20% of the observed variation. This implies the complexity and prediction difficulty of the upper ocean circulation in this region.
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ArticleAutonomous and Lagrangian ocean observations for Atlantic tropical cyclone studies and forecasts(Oceanography Society, 2017-06) Goni, Gustavo J. ; Todd, Robert E. ; Jayne, Steven R. ; Halliwell, George R. ; Glenn, Scott ; Dong, Jili ; Curry, Ruth G. ; Domingues, Ricardo ; Bringas, Francis ; Centurioni, Luca R. ; DiMarco, Steven F. ; Miles, Travis ; Morell, Julio M. ; Pomales, Luis ; Kim, Hyun-Sook ; Robbins, Pelle E. ; Gawarkiewicz, Glen G. ; Wilkin, John L. ; Heiderich, Joleen ; Baltes, Rebecca ; Cione, Joseph J. ; Seroka, Greg ; Knee, Kelly ; Sanabia, ElizabethThe tropical Atlantic basin is one of seven global regions where tropical cyclones (TCs) commonly originate, intensify, and affect highly populated coastal areas. Under appropriate atmospheric conditions, TC intensification can be linked to upper-ocean properties. Errors in Atlantic TC intensification forecasts have not been significantly reduced during the last 25 years. The combined use of in situ and satellite observations, particularly of temperature and salinity ahead of TCs, has the potential to improve the representation of the ocean, more accurately initialize hurricane intensity forecast models, and identify areas where TCs may intensify. However, a sustained in situ ocean observing system in the tropical North Atlantic Ocean and Caribbean Sea dedicated to measuring subsurface temperature, salinity, and density fields in support of TC intensity studies and forecasts has yet to be designed and implemented. Autonomous and Lagrangian platforms and sensors offer cost-effective opportunities to accomplish this objective. Here, we highlight recent efforts to use autonomous platforms and sensors, including surface drifters, profiling floats, underwater gliders, and dropsondes, to better understand air-sea processes during high-wind events, particularly those geared toward improving hurricane intensity forecasts. Real-time data availability is key for assimilation into numerical weather forecast models.
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PreprintTowards an integrated observation and modeling system in the New York Bight using variational methods. Part II : repressenter-based observing strategy evaluation( 2009-09-23) Zhang, Weifeng G. ; Wilkin, John L. ; Levin, Julia C.As part of an effort to build an integrated observation and modeling system for the New York Bight, this study explores observing system design using a representer-based method. The Representer of a single observation describes the covariance between the observed quantity and ocean state at all locations at any time. It is related closely to the influence of the observation on control variable correction in a 4D Variational data assimilation system. We prove that these properties hold for the combination of representers that is associated with an arithmetic function of model variables or a group of observations. The representer-based method is used here to identify which of a set of proposed tracks for an autonomous coastal glider is better for predicting horizontal salt flux within the Hudson Shelf Valley in a 2-day forecast period. Twin experiments confirm the result. The system is also used to compare different observation strategies. We show that a glider that traverses a regular transect influences a larger area than a continuously profiling mooring, but the mooring carries stronger influence at the observation location. The representer analysis shows how the information provided by observations extends toward the dynamically upstream and how increasing the duration of the analysis window captures more dynamical connections and expands the area of influence of the observations in data assimilation. Overall, the study demonstrates that the representer methodology can quantitatively contrast different observational strategies and determine spatial patterns and temporal extent of the influence of observations, both of which are helpful for evaluating the design of observation networks.
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ArticleThe impact of wind forcing on the thermal wind shear of a river plume(American Geophysical Union, 2019-10-31) Mazzini, Piero L. F. ; Chant, Robert J. ; Scully, Malcolm E. ; Wilkin, John L. ; Hunter, Elias J. ; Nidzieko, Nicholas J.A 38-day long time series obtained using a combination of moored Wirewalkers equipped with conductivity-temperature-depth profilers and bottom-mounted and subsurface acoustic Doppler current profilers provided detailed high-resolution observations that resolved near-surface velocity and vertical and cross-shelf density gradients of the Chesapeake Bay plume far field. This unprecedented data set allowed for a detailed investigation of the impact of wind forcing on the thermal wind shear of a river plume. Our results showed that thermal wind balance was a valid approximation for the cross-shelf momentum balance over the entire water column during weak winds (|𝜏w 𝑦 | < 0.075 Pa), and it was also valid within the interior during moderate downwelling (−0.125< 𝜏w 𝑦 < −0.075 Pa). Stronger wind conditions, however, resulted in the breakdown of the thermal wind balance in the Chesapeake Bay plume, with thermal wind shear overestimating the observed shear during downwelling and underestimating during upwelling conditions. A momentum budget analysis suggests that viscous stresses from wind-generated turbulence are mainly responsible for the generation of ageostrophic shear.
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ArticleCharacterizing wave- and current- induced bottom shear stress : U.S. middle Atlantic continental shelf(Elsevier B.V., 2012-11-05) Dalyander, P. Soupy ; Butman, Bradford ; Sherwood, Christopher R. ; Signell, Richard P. ; Wilkin, John L.Waves and currents create bottom shear stress, a force at the seabed that influences sediment texture distribution, micro-topography, habitat, and anthropogenic use. This paper presents a methodology for assessing the magnitude, variability, and driving mechanisms of bottom stress and resultant sediment mobility on regional scales using numerical model output. The analysis was applied to the Middle Atlantic Bight (MAB), off the U.S. East Coast, and identified a tidally-dominated shallow region with relatively high stress southeast of Massachusetts over Nantucket Shoals, where sediment mobility thresholds are exceeded over 50% of the time; a coastal band extending offshore to about 30 m water depth dominated by waves, where mobility occurs more than 20% of the time; and a quiescent low stress region southeast of Long Island, approximately coincident with an area of fine-grained sediments called the “Mud Patch”. The regional high in stress and mobility over Nantucket Shoals supports the hypothesis that fine grain sediment winnowed away in this region maintains the Mud Patch to the southwest. The analysis identified waves as the driving mechanism for stress throughout most of the MAB, excluding Nantucket Shoals and sheltered coastal bays where tides dominate; however, the relative dominance of low-frequency events varied regionally, and increased southward toward Cape Hatteras. The correlation between wave stress and local wind stress was lowest in the central MAB, indicating a relatively high contribution of swell to bottom stress in this area, rather than locally generated waves. Accurate prediction of the wave energy spectrum was critical to produce good estimates of bottom shear stress, which was sensitive to energy in the long period waves.
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PreprintTowards an integrated observation and modeling system in the New York Bight using variational methods. Part I : 4DVAR data assimilation( 2009-09-23) Zhang, Weifeng G. ; Wilkin, John L. ; Arango, Hernan G.Four-dimensional Variational data assimilation (4DVAR) in the Regional Ocean Modeling System (ROMS) is used to produce a best-estimate analysis of ocean circulation in the New York Bight during spring 2006 by assimilating observations collected by a variety of instruments during an intensive field program. An incremental approach is applied in an overlapped cycling system with 3-day data assimilation window to adjust model initial conditions. The model-observation mismatch for all observed variables is reduced substantially. Comparisons between model forecast and independent observations show improved forecast skill for about 15 days for temperature and salinity, and 2 to 3 days for velocity. Tests assimilating only certain subsets of the data indicate that assimilating satellite sea surface temperature improves the forecast of surface and subsurface temperature but worsens the salinity forecast. Assimilating in situ temperature and salinity from gliders improves the salinity forecast but has little effect on temperature. Assimilating HF-radar surface current data improves the velocity forecast by 1-2 days yet worsens the forecast of subsurface temperature. During some time periods the convergence for velocity is poor as a result of the data assimilation system being unable to reduce errors in the applied winds because surface forcing is not among the control variables. This study demonstrates the capability of 4DVAR data assimilation system to reduce model-observation mismatch and improve forecasts in the coastal ocean, and highlights the value of accurate meteorological forcing.
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ArticleBarotropic tides on the southeast New England shelf : a view from a hybrid data assimilative modeling approach(American Geophysical Union, 2006-08-01) He, Ruoying ; Wilkin, John L.A high-resolution hybrid data assimilative (DA) modeling system is used to study barotropic tides and tidal dynamics on the southeast New England shelf. In situ observations include tidal harmonics of 5 major tidal constituents [M2, S2, N2, O1, and K1] analyzed from coastal sea level and bottom pressure gauges. The DA system consists of both forward and inverse models. The former is the three-dimensional, finite difference, nonlinear Regional Ocean Modeling System (ROMS). The latter is a three-dimensional linearized, frequency domain, finite element model TRUXTON. The DA system assimilates in situ observations via the inversion for the barotropic tidal open boundary conditions (OBCs). Model skill is evaluated by comparing the misfits between the observed and modeled tidal harmonics. The assimilation scheme is found effective and efficient in correcting the tidal OBCs, which in turn improve ROMS tidal solutions. Up to 50% decreases of model/data misfits are achieved after inverse data assimilation. Co-amplitude and co-phase maps and tidal current ellipses for each of 5 tidal constituents are generated, revealing complex tidal variability in this transition region between the tidally amplified Gulf of Maine in the northeast and the tidally much less energetic Middle Atlantic Bight in the southwest. Detailed examinations on the residual circulation, energetics, and momentum balances of the M2 tide reveal the key roles of the unique bottom bathymetry of Nantucket Shoals and the complex coastal geometry in affecting the regional tidal dynamics.
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Technical ReportA computer program for calculating frequencies and modal structure of free coastal-trapped waves(Woods Hole Oceanographic Institution, 1987-12) Wilkin, John L.A listing and full documentation is presented for a FORTRAN computer program which computes the dispersion curves and across-shelf modal structures of free coastal-trapped waves in a coastal channel. The three velocity components, mass transport streamfunction, and density and pressure perturbation fields are .computed. The solution procedure used (horizontal finite differences on a staggered grid and an expansion in the vertical in terms of modified Chebyshev polynomials) makes the solution compatible (without interpolation) with the numerical scheme employed in the Haidvogel et al. (1988) primitive equation ocean circulation model.
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ArticleEvolving the physical global ocean observing system for research and application services through international coordination(Frontiers Media, 2019-08-06) Sloyan, Bernadette M. ; Wilkin, John L. ; Hill, Katherine Louise ; Chidichimo, Maria Paz ; Cronin, Meghan F. ; Johannessen, Johnny A. ; Karstensen, Johannes ; Krug, Marjolaine ; Lee, Tong ; Oka, Eitarou ; Palmer, Matthew D. ; Rabe, Benjamin ; Speich, Sabrina ; von Schuckmann, Karina ; Weller, Robert A. ; Yu, WeidongClimate change and variability are major societal challenges, and the ocean is an integral part of this complex and variable system. Key to the understanding of the ocean’s role in the Earth’s climate system is the study of ocean and sea-ice physical processes, including its interactions with the atmosphere, cryosphere, land, and biosphere. These processes include those linked to ocean circulation; the storage and redistribution of heat, carbon, salt and other water properties; and air-sea exchanges of heat, momentum, freshwater, carbon, and other gasses. Measurements of ocean physics variables are fundamental to reliable earth prediction systems for a range of applications and users. In addition, knowledge of the physical environment is fundamental to growing understanding of the ocean’s biogeochemistry and biological/ecosystem variability and function. Through the progress from OceanObs’99 to OceanObs’09, the ocean observing system has evolved from a platform centric perspective to an integrated observing system. The challenge now is for the observing system to evolve to respond to an increasingly diverse end user group. The Ocean Observations Physics and Climate panel (OOPC), formed in 1995, has undertaken many activities that led to observing system-related agreements. Here, OOPC will explore the opportunities and challenges for the development of a fit-for-purpose, sustained and prioritized ocean observing system, focusing on physical variables that maximize support for fundamental research, climate monitoring, forecasting on different timescales, and society. OOPC recommendations are guided by the Framework for Ocean Observing which emphasizes identifying user requirements by considering time and space scales of the Essential Ocean Variables. This approach provides a framework for reviewing the adequacy of the observing system, looking for synergies in delivering an integrated observing system for a range of applications and focusing innovation in areas where existing technologies do not meet these requirements.
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PreprintAdvancing coastal ocean modelling, analysis, and prediction for the US Integrated Ocean Observing System( 2017-04-19) Wilkin, John L. ; Rosenfeld, Leslie K. ; Allen, Arthur ; Baltes, Rebecca ; Baptista, Antonio ; He, Ruoying ; Hogan, Patrick ; Kurapov, Alexander ; Mehra, Avichal ; Quintrell, Josie ; Schwab, David ; Signell, Richard P. ; Smith, JaneThis paper outlines strategies that would advance coastal ocean modeling, analysis and prediction as a complement to the observing and data management activities of the coastal components of the U.S. Integrated Ocean Observing System (IOOS®) and the Global Ocean Observing System (GOOS). The views presented are the consensus of a group of U.S. based researchers with a cross-section of coastal oceanography and ocean modeling expertise and community representation drawn from Regional and U.S. Federal partners in IOOS. Priorities for research and development are suggested that would enhance the value of IOOS observations through model-based synthesis, deliver better model-based information products, and assist the design, evaluation and operation of the observing system itself. The proposed priorities are: model coupling, data assimilation, nearshore processes, cyberinfrastructure and model skill assessment, modeling for observing system design, evaluation and operation, ensemble prediction, and fast predictors. Approaches are suggested to accomplish substantial progress in a 3-8 year timeframe. In addition, the group proposes steps to promote collaboration between research and operations groups in Regional Associations, U.S. Federal Agencies, and the international ocean research community in general that would foster coordination on scientific and technical issues, and strengthen federal-academic partnerships benefiting IOOS stakeholders and end users.
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ArticleMultiscale multiphysics data-informed modeling for three-dimensional ocean acoustic simulation and prediction(Acoustical Society of America, 2019-09-30) Duda, Timothy F. ; Lin, Ying-Tsong ; Newhall, Arthur E. ; Helfrich, Karl R. ; Lynch, James F. ; Zhang, Weifeng G. ; Lermusiaux, Pierre F. J. ; Wilkin, John L.Three-dimensional (3D) underwater sound field computations have been used for a few decades to understand sound propagation effects above sloped seabeds and in areas with strong 3D temperature and salinity variations. For an approximate simulation of effects in nature, the necessary 3D sound-speed field can be made from snapshots of temperature and salinity from an operational data-driven regional ocean model. However, these models invariably have resolution constraints and physics approximations that exclude features that can have strong effects on acoustics, example features being strong submesoscale fronts and nonhydrostatic nonlinear internal waves (NNIWs). Here, work to predict NNIW fields to improve 3D acoustic forecasts using an NNIW model nested in a tide-inclusive data-assimilating regional model is reported. The work was initiated under the Integrated Ocean Dynamics and Acoustics project. The project investigated ocean dynamical processes that affect important details of sound-propagation, with a focus on those with strong intermittency (high kurtosis) that are challenging to predict deterministically. Strong internal tides and NNIW are two such phenomena, with the former being precursors to NNIW, often feeding energy to them. Successful aspects of the modeling are reported along with weaknesses and unresolved issues identified in the course of the work.
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ThesisScattering of coastal-trapped waves by irregularities in coastline and topography(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1988-09) Wilkin, John L.A study is conducted of the scattering of freely-propagating subinertial frequency coastal-trapped waves (CTWS) by large variations in coastline and topography using analytical and numerical techniques. Particular attention is paid to the role of stratification because, as shown, the introduction of even modest stratification can eliminate backscattered free-waves with large wavenumbers which occur, theoretically, in a barotropic ocean. An analytical solution is presented for the scattering of barotropic waves incident upon a discontinuity in shelf width. Discussion of solutions relying on backscattered free-waves is avoided by considering only the range of parameters over which energy transmission is nearly 100%. The solution shows there is a substantial transfer of energy to modes other than that of the incident wave. The transmitted mode most readily excited is that which has the across-shelf structure most closely coinciding with that of the incident wave. For a widening shelf, energy is therefore readily transferred to higher modes. The resultant presence of multiple modes produces a strong modulation in flow intensity and phase progression downstream of the scattering region which may affect the interpretation of shelf wave observations. A non-dispersive shelf wave 'pulse' of limited a10ngshelf extent scatters into a train of similarly shaped waves of all allowable modes, each propagating at its own free-wave speed. To overcome limitations of the analytical study a numerical model which accomodates arbitrary density stratification, bathymetry, and coastline, is employed. Numerical simulations are conducted of the scattering of CTWs by a set of topographic and coastline variations which are representative of many continental shelves. The strength of the scattering observed is found to be proportional to a topographic warp factor which estimates the severity of the topographic irregularities. The scattering is amplified by density stratification. A comparison of the effects of widening and narrowing topographies shows that the gross scattering effects of 'reciprocal' topographies are qnite similar. Within the scattering region itself, the strengths of the scattered-wave-induced currents exhibit substantial variation over short spatial scales. On both widening and narrowiag shelves, there is generally a marked intensification of the flow within the scattering region, and significant differences in the directions of the currents at points separated by a few tens of kilometers indicate the occurence of rapid variations ia phase. On narrowing shelves, the influence of the scattering can extend upstream into the region of uniform topography even when no freely-propagating backscattered waves exist. A simulation is condncted of CTW scattering at a site on the East Coast of Australia where observations suggest the presence of scattered freely-propagating CTWs. The success of the model simulation in reproducing features of observations confirms that realistic shelf geometries can scatter significant levels of CTW energy, and that the scattered waves can have an appreciable signal in current-meter observations made on the continental shelf. This demonstrates that along irregular coastlines it is necessary to account for the possibility that CTW scattering processes filay be in effect if oceanographic observations are to be interpreted correctly.
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ArticleSEASTAR: A mission to study ocean submesoscale dynamics and small-scale atmosphere-ocean processes in coastal, shelf and polar seas(Frontiers Media, 2019-08-13) Gommenginger, Christine ; Chapron, Bertrand ; Hogg, Andy ; Buckingham, Christian ; Fox-Kemper, Baylor ; Eriksson, Leif ; Soulat, Francois ; Ubelmann, Clement ; Ocampo-Torres, Francisco ; Nardelli, Bruno Buongiorno ; Griffin, David ; Lopez-Dekker, Paco ; Knudsen, Per ; Andersen, Ole ; Stenseng, Lars ; Stapleton, Neil ; Perrie, Will ; Violante-Carvalho, Nelson ; Schulz-Stellenfleth, Johannes ; Woolf, David K. ; Isern-Fontanet, Jordi ; Ardhuin, Fabrice ; Klein, Patrice ; Mouche, Alexis ; Pascual, Ananda ; Capet, Xavier ; Hauser, Daniele ; Stoffelen, Ad ; Morrow, Rosemary ; Aouf, Lotfi ; Breivik, Øyvind ; Fu, Lee-Lueng ; Johannessen, Johnny A. ; Aksenov, Yevgeny ; Bricheno, Lucy ; Hirschi, Joel ; Martin, Adrien C. H. ; Martin, Adrian P. ; Nurser, A. J. George ; Polton, Jeff ; Wolf, Judith ; Johnsen, Harald ; Soloviev, Alexander ; Jacobs, Gregg A. ; Collard, Fabrice ; Groom, Steve ; Kudryavtsev, Vladimir ; Wilkin, John L. ; Navarro, Victor ; Babanin, Alexander ; Martin, Matthew ; Siddorn, John ; Saulter, Andrew ; Rippeth, Tom P. ; Emery, Bill ; Maximenko, Nikolai ; Romeiser, Roland ; Graber, Hans C. ; Alvera Azcarate, Aida ; Hughes, Chris W. ; Vandemark, Douglas ; da Silva, Jose ; Van Leeuwen, Peter Jan ; Naveira Garabato, Alberto C. ; Gemmrich, Johannes ; Mahadevan, Amala ; Marquez, Jose ; Munro, Yvonne ; Doody, Sam ; Burbidge, GeoffHigh-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.
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ArticleGlobal perspectives on observing ocean boundary current systems(Frontiers Media, 2019-08-08) Todd, Robert E. ; Chavez, Francisco P. ; Clayton, Sophie A. ; Cravatte, Sophie ; Goes, Marlos Pereira ; Graco, Michelle ; Lin, Xiaopei ; Sprintall, Janet ; Zilberman, Nathalie ; Archer, Matthew ; Arístegui, Javier ; Balmaseda, Magdalena A. ; Bane, John M. ; Baringer, Molly O. ; Barth, John A. ; Beal, Lisa M. ; Brandt, Peter ; Calil, Paulo H. R. ; Campos, Edmo ; Centurioni, Luca R. ; Chidichimo, Maria Paz ; Cirano, Mauro ; Cronin, Meghan F. ; Curchitser, Enrique N. ; Davis, Russ E. ; Dengler, Marcus ; deYoung, Brad ; Dong, Shenfu ; Escribano, Ruben ; Fassbender, Andrea ; Fawcett, Sarah E. ; Feng, Ming ; Goni, Gustavo J. ; Gray, Alison R. ; Gutiérrez, Dimitri ; Hebert, Dave ; Hummels, Rebecca ; Ito, Shin-ichi ; Krug, Marjolaine ; Lacan, Francois ; Laurindo, Lucas ; Lazar, Alban ; Lee, Craig M. ; Lengaigne, Matthieu ; Levine, Naomi M. ; Middleton, John ; Montes, Ivonne ; Muglia, Michael ; Nagai, Takeyoshi ; Palevsky, Hilary I. ; Palter, Jaime B. ; Phillips, Helen E. ; Piola, Alberto R. ; Plueddemann, Albert J. ; Qiu, Bo ; Rodrigues, Regina ; Roughan, Moninya ; Rudnick, Daniel L. ; Rykaczewski, Ryan R. ; Saraceno, Martin ; Seim, Harvey E. ; Sen Gupta, Alexander ; Shannon, Lynne ; Sloyan, Bernadette M. ; Sutton, Adrienne J. ; Thompson, LuAnne ; van der Plas, Anja K. ; Volkov, Denis L. ; Wilkin, John L. ; Zhang, Dongxiao ; Zhang, LinlinOcean boundary current systems are key components of the climate system, are home to highly productive ecosystems, and have numerous societal impacts. Establishment of a global network of boundary current observing systems is a critical part of ongoing development of the Global Ocean Observing System. The characteristics of boundary current systems are reviewed, focusing on scientific and societal motivations for sustained observing. Techniques currently used to observe boundary current systems are reviewed, followed by a census of the current state of boundary current observing systems globally. The next steps in the development of boundary current observing systems are considered, leading to several specific recommendations.