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© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Westerholm, D. G., Ainsworth, C. H., Barker, C. H., Brewer, P. G., Farrington, J. W., Justic, D., Kourafalou, V. H., Murawski, S. A., Shepherd, J. G., & Solo-Gabriele, H. M. Preparedness, planning, and advances in operational response. Oceanography, 34(1), (2021): 212–227, https://doi.org/10.5670/oceanog.2021.127., During the last 50 years, the numbers and sizes of oil spills have been significantly reduced through prevention. But spills still occur, and it is critical to prepare for these events through planning and exercises. Operational decisions are designed to expedite cleanup and minimize overall impacts, yet they often involve complex trade-offs between a multitude of competing interests. It is imperative to apply the best technology and science when events occur. However, while planning and response tactics have evolved over time, determining what may be most at risk is often confounded by sparse background data, modeling limitations, scalability, or research gaps. Since 2010, the Gulf of Mexico Research Initiative (GoMRI) and other oil spill research helped address many issues and propelled advances in spill modeling. As a result, there is an increased understanding of environmental impacts, how to assess damages, and the unintended consequences of spill countermeasures. The unprecedented amount of information resulting from this research has strengthened the bridge between the academic community and operational responders and brought improvements in preparedness, planning, and operations. This paper focuses primarily on GoMRI research and advances that relate to operational activities, as well as limitations and opportunities for gap-filling future research.

A major challenge for managing impacts and implementing effective mitigation measures and adaptation strategies for coastal zones affected by future sea level (SL) rise is our limited capacity to predict SL change at the coast on relevant spatial and temporal scales. Predicting coastal SL requires the ability to monitor and simulate a multitude of physical processes affecting SL, from local effects of wind waves and river runoff to remote influences of the large-scale ocean circulation on the coast. Here we assess our current understanding of the causes of coastal SL variability on monthly to multi-decadal timescales, including geodetic, oceanographic and atmospheric aspects of the problem, and review available observing systems informing on coastal SL. We also review the ability of existing models and data assimilation systems to estimate coastal SL variations and of atmosphere-ocean global coupled models and related regional downscaling efforts to project future SL changes. We discuss (1) observational gaps and uncertainties, and priorities for the development of an optimal and integrated coastal SL observing system, (2) strategies for advancing model capabilities in forecasting short-term processes and projecting long-term changes affecting coastal SL, and (3) possible future developments of sea level services enabling better connection of scientists and user communities and facilitating assessment and decision making for adaptation to future coastal SL change.

Coastal zones are highly dynamical systems affected by a variety of natural and anthropogenic forcing factors that include sea level rise, extreme events, local oceanic and atmospheric processes, ground subsidence, etc. However, so far, they remain poorly monitored on a global scale. To better understand changes affecting world coastal zones and to provide crucial information to decision-makers involved in adaptation to and mitigation of environmental risks, coastal observations of various types need to be collected and analyzed. In this white paper, we first discuss the main forcing agents acting on coastal regions (e.g., sea level, winds, waves and currents, river runoff, sediment supply and transport, vertical land motions, land use) and the induced coastal response (e.g., shoreline position, estuaries morphology, land topography at the land–sea interface and coastal bathymetry). We identify a number of space-based observational needs that have to be addressed in the near future to understand coastal zone evolution. Among these, improved monitoring of coastal sea level by satellite altimetry techniques is recognized as high priority. Classical altimeter data in the coastal zone are adversely affected by land contamination with degraded range and geophysical corrections. However, recent progress in coastal altimetry data processing and multi-sensor data synergy, offers new perspective to measure sea level change very close to the coast. This issue is discussed in much detail in this paper, including the development of a global coastal sea-level and sea state climate record with mission consistent coastal processing and products dedicated to coastal regimes. Finally, we present a new promising technology based on the use of Signals of Opportunity (SoOp), i.e., communication satellite transmissions that are reutilized as illumination sources in a bistatic radar configuration, for measuring coastal sea level. Since SoOp technology requires only receiver technology to

This paper summarizes recent efforts on Observing System Evaluation (OS-Eval) by the Ocean Data Assimilation and Prediction (ODAP) communities such as GODAE OceanView and CLIVAR-GSOP. It provides some examples of existing OS-Eval methodologies, and attempts to discuss the potential and limitation of the existing approaches. Observing System Experiment (OSE) studies illustrate the impacts of the severe decrease in the number of TAO buoys during 2012-2014 and TRITON buoys since 2013 on ODAP system performance. Multi-system evaluation of the impacts of assimilating satellite sea surface salinity data based on OSEs has been performed to demonstrate the need to continue and enhance satellite salinity missions. Impacts of underwater gliders have been assessed using Observing System Simulation Experiments (OSSEs) to provide guidance on the effective coordination of the western North Atlantic observing system elements. OSSEs are also being performed under H2020 AtlantOS project with the goal to enhance and optimize the Atlantic in-situ networks. Potential of future satellite missions of wide-swath altimetry and surface ocean currents monitoring is explored through OSSEs and evaluation of Degrees of Freedomfor Signal (DFS). Forecast Sensitivity Observation Impacts (FSOI) are routinely evaluated for monitoring the ocean observation impacts in the US Navy's ODAP system. Perspectives on the extension of OS-Eval to coastal regions, the deep ocean, polar regions, coupled data assimilation, and biogeochemical applications are also presented. Based on the examples above, we identify the limitations of OS-Eval, indicating that the most significant limitation is reduction of robustness and reliability of the results due to their system-dependency. The difficulty of performing evaluation in near real time is also critical. A strategy to mitigate the limitation and to strengthen the impact of evaluations is discussed. In particular, we emphasize the importance of collaboration within t

Integration of observations of the coastal ocean continuum, from regional oceans to shelf seas and estuaries/deltas with models, can substantially increase the value of observations and enable a wealth of applications. In particular, models can play a critical role at connecting sparse observations, synthesizing them, and assisting the design of observational networks; in turn, whenever available, observations can guide coastal model development. Coastal observations should sample the two-way interactions between nearshore, estuarine and shelf processes and open ocean processes, while accounting for the different pace of circulation drivers, such as the fast atmospheric, hydrological and tidal processes and the slower general ocean circulation and climate scales. Because of these challenges, high-resolution models can serve as connectors and integrators of coastal continuum observations. Data assimilation approaches can provide quantitative, validated estimates of Essential Ocean Variables in the coastal continuum, adding scientific and socioeconomic value to observations through applications (e.g., sea-level rise monitoring, coastal management under a sustainable ecosystem approach, aquaculture, dredging, transport and fate of pollutants, maritime safety, hazards under natural variability or climate change). We strongly recommend an internationally coordinated approach in support of the proper integration of global and coastal continuum scales, as well as for critical tasks such as community-agreed bathymetry and coastline products.

A major challenge for managing impacts and implementing effective mitigation measures and adaptation strategies for coastal zones affected by future sea level (SL) rise is our limited capacity to predict SL change at the coast on relevant spatial and temporal scales. Predicting coastal SL requires the ability to monitor and simulate a multitude of physical processes affecting SL, from local effects of wind waves and river runoff to remote influences of the large-scale ocean circulation on the coast. Here we assess our current understanding of the causes of coastal SL variability on monthly to multi-decadal timescales, including geodetic, oceanographic and atmospheric aspects of the problem, and review available observing systems informing on coastal SL. We also review the ability of existing models and data assimilation systems to estimate coastal SL variations and of atmosphere-ocean global coupled models and related regional downscaling efforts to project future SL changes. We discuss (1) observational gaps and uncertainties, and priorities for the development of an optimal and integrated coastal SL observing system, (2) strategies for advancing model capabilities in forecasting short-term processes and projecting long-term changes affecting coastal SL, and (3) possible future developments of sea level services enabling better connection of scientists and user communities and facilitating assessment and decision making for adaptation to future coastal SL change.

Coastal zones are highly dynamical systems affected by a variety of natural and anthropogenic forcing factors that include sea level rise, extreme events, local oceanic and atmospheric processes, ground subsidence, etc. However, so far, they remain poorly monitored on a global scale. To better understand changes affecting world coastal zones and to provide crucial information to decision-makers involved in adaptation to and mitigation of environmental risks, coastal observations of various types need to be collected and analyzed. In this white paper, we first discuss the main forcing agents acting on coastal regions (e.g., sea level, winds, waves and currents, river runoff, sediment supply and transport, vertical land motions, land use) and the induced coastal response (e.g., shoreline position, estuaries morphology, land topography at the land-sea interface and coastal bathymetry). We identify a number of space-based observational needs that have to be addressed in the near future to understand coastal zone evolution. Among these, improved monitoring of coastal sea level by satellite altimetry techniques is recognized as high priority. Classical altimeter data in the coastal zone are adversely affected by land contamination with degraded range and geophysical corrections. However, recent progress in coastal altimetry data processing and multi-sensor data synergy, offers new perspective to measure sea level change very close to the coast. This issue is discussed in much detail in this paper, including the development of a global coastal sea-level and sea state climate record with mission consistent coastal processing and products dedicated to coastal regimes. Finally, we present a new promising technology based on the use of Signals of Opportunity (SoOp), i.e., communication satellite transmissions that are reutilized as illumination sources in a bistatic radar configuration, for measuring coastal sea level. Since SoOp technology requires only receiver technology to

The marine environment plays an increasingly important role in shaping economies and infrastructures, and touches upon many aspects of our lives, including food supplies, energy resources, national security and recreational activities. Global Ocean Data Assimilation Experiment (GODAE) and GODAE OceanView have provided platforms for international collaboration that significantly contribute to the scientific development and increasing uptake of ocean forecasting products by end users who address societal issues such as those listed above. Many scientific challenges and opportunities remain to be tackled in the ever-changing field of operational oceanography, from the observing system to modelling, data assimilation and product dissemination. This paper provides a brief overview of past achievements in GODAE OceanView, but subsequently concentrates on the future scientific foci of GODAE OceanView and its Task Teams, and provides a vision for the future of ocean forecasting.

The overarching goal is to determine how simulations and forecasts of currents and water properties in the coastal ocean, and the scientific understanding obtained from them, are influenced by the initial and boundary conditions provided to nested coastal ocean models. In addition to surface atmospheric forcing and coastal freshwater runoff, the coastal ocean is influenced by offshore ocean variability resulting from processes ranging from basin-scale wind-driven gyre and thermohaline circulation down to regional and local circulation associated with boundary currents and eddies. To accurately represent the offshore ocean influence, the coastal model must be nested within fields that accurately represent (1) the initial state of the ocean throughout the model domain and (2) currents and water properties at the nested model boundaries during the model run. We specifically evaluate the HYCOM (HYbrid Coordinate Ocean Model) data assimilation products developed as part of the Global Ocean Data Assimilation Experiment (GODAE) for providing these fields. Coastal model evaluation is being performed over a range of environments to provide feedback that will guide improvements to the HYCOM-GODAE products. The overall regional focus encompasses the coastal northern and eastern Gulf of Mexico through the Florida Straits, which represent a broad range of shelf geometries, river runoff, seasonal atmospheric forcing, and offshore forcing. Three regions are emphasized: (1) the West Florida Shelf (WFS); (2) the South Florida Coastal Region (SoFLA), including the Florida Straits, the Florida Keys and Atlantic Keys shelf, Florida Bay, and the adjacent southwest Florida shelf; and (3) the coastal northern Gulf of Mexico (NGoM). This project focuses only on downscaling open-ocean variability to the coastal ocean (one way nesting)., Prepared in collaboration with the College of Marine Science, University of South Florida, St. Petersburg, FL ; Naval Research Laboratory, Stennis Space Center, MS; Planning Systems, Incorporated, Stennis Space Center, MS; and Naval Research Laboratory, Monterey, CA. The original document contains color images. All DTIC reproductions will be in black and white.

The overarching goal is to determine how simulations and forecasts of currents and water properties in the coastal ocean, and the scientific results obtained from them, are influenced by the initial and boundary conditions provided to nested coastal ocean models. In addition to surface atmospheric forcing and coastal freshwater runoff, the coastal ocean is influenced by offshore ocean variability resulting from processes ranging from basin-scale wind-driven gyre and thermohaline circulation down to regional and local circulation associated with boundary currents and eddies. To accurately represent the offshore ocean influence, the coastal model must be nested within fields that accurately represent (1) the initial state of the ocean throughout the model domain and (2) currents and water properties at the nested model boundaries during the model run. We specifically evaluate the HYCOM (HYbrid Coordinate Ocean Model) data assimilation products developed as part of the Global Ocean Data Assimilation Experiment (GODAE) for providing these fields. Coastal model evaluation is being performed over a range of environments to provide feedback that will guide improvements to the HYCOM-GODAE products. The overall regional focus encompasses the coastal northern and eastern Gulf of Mexico through the Florida Straits, which represent a broad range of shelf geometries, river runoff, seasonal atmospheric forcing, and offshore forcing. Three regions are emphasized: (1) the West Florida Shelf (WFS); (2) the South Florida Coastal Region (SoFLA), including the Florida Straits, the Florida Keys and Atlantic Keys shelf, Florida Bay, and the adjacent southwest Florida shelf; and (3) the coastal northern Gulf of Mexico (NGoM). This project focuses only on downscaling open-ocean variability to the coastal ocean (one way nesting)., A National Oceanographic Partnership Program Award. The original document contains color images.

The overarching goal is to improve our capability to map, understand, and predict changes in currents and water properties in the coastal ocean. Providing real-time (nowcast) and future (forecast) coastal ocean fields requires a coastal ocean nowcast/forecast system that consists of several components: 1. a high-quality ocean general circulation model; 2. accurate surface flux (atmospheric forcing) fields to drive the ocean model; 3. accurate estimates of coastal ocean fields at the start of a model run and along the lateral boundaries of the coastal domain during model runs; 4. accurate estimates of freshwater input from rivers and estuaries; and 5. high-quality ocean observations. The observations are necessary to provide the accurate initial and boundary fields required by component (3) and to evaluate the performance of the nowcast/forecast system. The central focus of this project is component (3), specifically to quantify and understand the impact of initial and boundary fields on coastal ocean nowcasts and forecasts, and to provide feedback that will motivate improvements in generating these fields. We are evaluating initial and boundary fields provided by a nowcast/forecast system based on the HYbrid Coordinate Ocean Model (HYCOM) developed at the Naval Research Laboratory (NRL-Stennis) as part of the Global Ocean Data Assimilation Experiment (GODAE). Results are being communicated to NRL to guide improvement strategies for their nowcast/forecast system. Although our central focus is on component (3), we also consider the other four components of the coastal nowcast/forecast system. We are striving to improve ocean model performance, evaluate model sensitivity to different atmospheric forcing products, study sensitivity to river runoff, and assess the adequacy of available coastal ocean observations. Coastal ocean simulations are also being analyzed to improve our scientific understanding of ocean variability observed in our region of interest., A National Oceanographic Partnership Program Award. Prepared in collaboration with the Florida State University, Tallahassee, FL; College of Marine Science, University of South Florida, St. Petersburg, FL; Naval Research Laboratory, Stennis Space Center, MS; Planning Systems, Incorporated, Stennis Space Center, MS; and the Naval Research Laboratory, Monterey, CA. The original document contains color images.

The overarching goal is to improve our capability to model and understand currents and water properties in the coastal ocean, and to improve our capability to forecast future changes in these currents and water properties. Coastal ocean models are used for a wide range of purposes, including naval operations, commercial marine operations (including the influence of ocean currents on shipping and oil rigs), storm surge prediction, prediction of pollution dispersion, studies of coastal fisheries and ecosystems, and providing ocean currents for search and rescue operations. This project focuses on one important aspect of improving the performance of coastal ocean models, specifically improving the quality of the fields that are used to initialize these models and provide information on water properties and currents outside of the coastal region being modeled. Although the coastal ocean is strongly influenced by surface atmospheric forcing and coastal freshwater runoff, offshore ocean variability exerts a very significant influence in many regions due to a wide range of processes such as basin-scale climate variability, boundary current meanders, and offshore ocean eddies. To accurately represent the influence of this offshore variability on a coastal ocean model, the model must be nested within fields that accurately represent (1) the initial state of the coastal ocean throughout the model domain and (2) currents and water properties at the nested model boundaries. We will specifically evaluate the use of the HYbrid Coordinate Ocean Model (HYCOM) data assimilation product developed as part of the Global Ocean Data Assimilation Experiment (GODAE) for this purpose. The influence of these initial and boundary fields on the performance of the coastal model will be thoroughly evaluated. This information will provide important feedback that will be used to guide improvements to the HYCOM-GODAE product that provides the initial and boundary fields. The overall regional focus, Prepared in cooperation with University of South Florida, St. Petersburg, FL, Naval Research Laboratory, Stennis Space Center, MS, Planning Systems, Inc., Stennis Space Center, MS, and Naval Research Laboratory, Monterey, CA.