NOAA Center for Operational Oceanographic Products & Services

Global sea level provides an important indicator of the state of the warming climate, but changes in regional sea level are most relevant for coastal communities around the world. With improvements to the sea-level observing system, the knowledge of regional sea-level change has advanced dramatically in recent years. Satellite measurements coupled with in situ observations have allowed for comprehensive study and improved understanding of the diverse set of drivers that lead to variations in sea level in space and time. Despite the advances, gaps in the understanding of contemporary sea-level change remain and inhibit the ability to predict how the relevant processes may lead to future change. These gaps arise in part due to the complexity of the linkages between the drivers of sea-level change. Here we review the individual processes which lead to sea-level change and then describe how they combine and vary regionally. The intent of the paper is to provide an overview of the current state of understanding of the processes that cause regional sea-level change and to identify and discuss limitations and uncertainty in our understanding of these processes. Areas where the lack of understanding or gaps in knowledge inhibit the ability to provide the needed information for comprehensive planning efforts are of particular focus. Finally, a goal of this paper is to highlight the role of the expanded sea-level observation network-particularly as related to satellite observations-in the improved scientific understanding of the contributors to regional sea-level change.

Abstract Meteotsunamis are atmospherically forced ocean waves with characteristics similar to seismic tsunamis. Several recent hazardous meteotsunamis resulted in damage and injuries along U.S. coastlines, such that the National Oceanic and Atmospheric Administration (NOAA) is investigating ways to detect and forecast meteotsunamis to provide advance warning. Better understanding meteotsunami occurrence along U.S. coastlines is a necessary step to pursue these objectives. Here a meteotsunami climatology of the U.S. East Coast is presented. The climatology relies on a wavelet analysis of 6-min water-level observations from 125 NOAA tide gauges from 1996 to 2017. A total of 548 meteotsunamis, or about per year, were identified and assessed using this approach along the U.S. East Coast. There were a total of 30 instances when gauges observed waves of more than 0.6 m, which is assumed to be a potentially impactful event, and several cases with wave heights more than 1 m. Tide gauges along the open coast observed the most frequent events, including more than five events per year at Atlantic City, New Jersey; Duck, North Carolina; and Myrtle Beach, South Carolina. The largest waves were observed by gauges in estuaries that amplified the meteotsunami signal, such as those in Providence, Rhode Island, and Port Canaveral, Florida. Seasonal trends indicate that meteotsunamis occur most frequently in the winter and summer months, especially July. This work supports future meteotsunami detection and warning capabilities at NOAA, including the development of an impact catalog to aid National Weather Service forecasters.

Operational ocean forecast systems provide routine marine products to an ever-widening community of users and stakeholders. The majority of users need information about the quality and reliability of the products to exploit them fully. Hence, forecast centres have been developing improved methods for evaluating and communicating the quality of their products. Global Ocean Data Assimilation Experiment (GODAE) OceanView, along with the Copernicus European Marine Core Service and other national and international programmes, has facilitated the development of coordinated validation activities among these centres. New metrics, assessing a wider range of ocean parameters, have been defined and implemented in real-time. An overview of recent progress and emerging international standards is presented here.

Abstract. Rip currents pose a major global beach hazard; estimates of annual rip-current-related deaths in the United States alone range from 35 to 100 per year. Despite increased social research into beach-goer experience, little is known about levels of rip current knowledge within the general population. This study describes the results of an online survey to determine the extent of rip current knowledge across the United States, with the aim of improving and enhancing existing beach safety education material. Results suggest that the US-based Break the Grip of the Rip!® campaign has been successful in educating the public about rip current safety directly or indirectly, with the majority of respondents able to provide an accurate description of how to escape a rip current. However, the success of the campaign is limited by discrepancies between personal observations at the beach and rip forecasts that are broadcasted for a large area and time. It was the infrequent beach user that identified the largest discrepancies between the forecast and their observations. Since infrequent beach users also do not seek out lifeguards or take the same precautions as frequent beach users, it is argued that they are also at greatest risk of being caught in a dangerous situation. Results of this study suggest a need for the national campaign to provide greater focus on locally specific and verified rip forecasts and signage in coordination with lifeguards, but not at the expense of the successful national awareness program.

We combine Synthetic Aperture Radar Interferometry (InSAR), tide gauge, and continuous GPS measurements to determine the spatial variation in vertical land motion (VLM) along the coast of the Los Angeles basin over the past decade, and to examine the impact of spatially variable VLM on relative sea level trends. By identifying radar scattering targets with long‐term coherence we make height corrections which allow interferogram creation for nearly the entire ERS‐1 catalog and permit estimation of average deformation rates with minimal temporal aliasing. Between Los Angeles Harbor and Newport Beach, mean VLM trends range from ∼3.4 to −4.3 mm/yr, reflecting the high level of ground water and oil extraction activity in the region. West of Los Angeles Harbor, VLM rates and spatial variability are roughly half as large. The 8‐year VLM trends exceed the long‐term sea level trend (0.8 mm/yr) determined from the 80 year Los Angeles Harbor tide gauge. The high degree of observed VLM variability emphasizes the need for the spatially continuous measurements provided by InSAR; a single tide gauge assessment of regional RSL would otherwise have limited applicability.

Abstract Climatologies of sea level anomalies (>0.05 m) and daily-mean storm surges (>0.3 m) are presented for the 1960–2010 cool seasons (October–April) along the East Coast of the United States at Boston, Massachusetts; Atlantic City, New Jersey; Sewells Point (Norfolk), Virginia; and Charleston, South Carolina. The high sea level anomaly and the number of storm surges, among the highest in the last half century during the 2009/10 cool season, are comparable during strong El Niño cool seasons. High numbers of daily storm surges occur in response to numerous East Coast extratropical cool-season storms and have a positive correlation with the El Niño phase of the El Niño–Southern Oscillation (ENSO). Patterns of anomalously high sea levels are attributed to El Niño–related changes to atmospheric pressure over the Gulf of Mexico and eastern Canada and to the wind field over the Northeast U.S. continental shelf.

Sea-level rise (SLR) is not just a future trend; it is occurring now in most coastal regions across the globe. It thus impacts not only long-range planning in coastal environments, but also emergency preparedness. Its inevitability and irreversibility on long time scales, in addition to its spatial non-uniformity, uncertain magnitude and timing, and capacity to drive non-stationarity in coastal flooding on planning and engineering timescales, create unique challenges for coastal risk-management decision processes. This review assesses past United States federal efforts to synthesize evolving SLR science in support of coastal risk management. In particular, it outlines the: (1) evolution in global SLR scenarios to those using a risk-based perspective that also considers low-probability but high-consequence outcomes, (2) regionalization of the global scenarios, and (3) use of probabilistic approaches. It also describes efforts to further contextualize regional scenarios by combining local mean sea-level changes with extreme water level projections. Finally, it offers perspectives on key issues relevant to the future uptake, interpretation, and application of sea-level change scenarios in decision-making. These perspectives have utility for efforts to craft standards and guidance for preparedness and resilience measures to reduce the risk of coastal flooding and other impacts related to SLR.

Ocean circulation and water mass characteristics around the Galápagos Archipelago are studied using a four-level nested-domain ocean system (HYCOM). The model sensitivity to atmospheric forcing frequency and spatial resolution is examined. Results show, that with prescribed atmospheric forcing, HYCOM can generally simulate the major El Niño events especially the strong 1997-1998 events. Waters surrounding the archipelago show a large range of temperature and salinity in association with four different current systems. West zones of Isabella and Fernandina Islands are the largest upwelling zones, resulting from the collision of the Equatorial Undercurrent (EUC) with the islands, bringing relatively colder, salty waters to the surface and marking the location of the highest biological production. Model results, which agree well with observations, show a seasonal cycle in the transport of the EUC, reaching a maximum during the late spring/early summer and minimum in the late fall. The far northern region is characterized by warmer, fresher water with the greatest mixed layer depth as a result of Panama Current waters entering from the northeast. Water masses over the remainder of the region result from mixing of cool Peru Current waters and upwelled Cold Tongue waters entering from the east.

The architecture, status and applications of a realtime data access, distribution, processing and storage system designed for networking radial data from surface current mapping HF-Radar instruments across the United States is presented. By leveraging the system design of HF-Radar sites, data access is generalized to nearly all sites while still providing alternate access options where needed. Data format convergence, while not required, is achieved for data from all systems through careful metadata mapping and code development. Object ring buffers (ORBs) and ORB communication protocol provide robust and flexible data transport while a relational database facilitates data storage. The HF-Radar Network has evolved from a prototype project to an operational status over the last 2.5 years with 4 data access sites (portals) and 1 data aggregation site (node) deployed. By early 2007, an additional portal and 2 additional nodes will be added to create a distributed network. To date, the repository contains over 356,000 radial files produced by 45 sites from 10 participating institutions. Recent development has focused on real-time total vector processing on a national scale. Base grids for the U.S. West and East/Gulf Coast of 1 km nominal resolution extending 300km offshore are created using an equidistant cylindrical projection. A community standard MATLAB toolbox for total vector processing is optimized for production on large grids and integrated into the real-time system to produce hourly surface current maps on a national scale at 1 km, 2 km and 6 km resolutions. Current applications of the HF-Radar network include an interactive radial diagnostic site for use by site operators and a prototype interactive web site providing the first images of realtime surface currents integrated across a national scale

Global Oceans is one chapter from the State of the Climate in 2019 annual report and is avail-able from https://doi.org/10.1175/BAMS-D-20-0105.1. Compiled by NOAA’s National Centers for Environmental Information, State of the Climate in 2019 is based on contr1ibutions from scien-tists from around the world. It provides a detailed update on global climate indicators, notable weather events, and other data collected by environmental monitoring stations and instru-ments located on land, water, ice, and in space. The full report is available from https://doi.org /10.1175/2020BAMSStateoftheClimate.1.

An unusual "triple-dip" La Nia, described in Sidebar 3.1, had continuing, wide-spread ramifications for the state of ocean and climate in 2022. Triple-dip La Nias are not unprecedented, but until now have always followed an extreme El Nio. Anomalously low sea-surface temperatures (SSTs) in the eastern tropical Pacific persisted from August 2020 through December 2022, with only a brief intermission in May-July 2021. Strengthened easterly trade winds drove anomalously strong westward surface currents and brought cold waters to the surface in the eastern equatorial Pacific while also accumulating anomalously salty and warm waters in the western equatorial Pacific, raising sea level there. These cold upwelled waters resulted in anomalously large fluxes of carbon dioxide from the ocean to the atmosphere and heat from the atmosphere to the ocean, with anomalously high chlorophyll concentrations found around its edges. Fresh sea-surface salinity (SSS) anomalies strengthened off the equator in the Pacific as the Intertropical Convergence Zone (ITCZ) and South Pacific Convergence Zone and associated rainfall shifted poleward.

Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Bulletin of the American Meteorological Society 102(8), (2021): S143–S198, https://doi.org/10.1175/BAMS-D-21-0083.1.

Abstract We use the standard deviation (sigma) of continuous 1 s water level sampling at 46 U.S. NOAA tide gauges available since 1996 as a high‐frequency variance measure. Sigma estimates local infragravity and incident wave band variability, is significantly correlated ( r = 0.5–0.9) to significant wave height ( H s ), and scales linearly to local observations and output from the global ocean wave reanalysis at most ocean‐exposed and harbor‐sheltered locations. Empirical orthogonal functions of daily mean sigma from six Hawaii tide gauges distinguish northerly and southerly modes that closely match local Hs observations. Depending on tide gauge location, the 99% of daily maxima sigma can be as large as or larger than the nontidal residual component of the water level sample. Our findings provide new uses of land‐based tide gauge data to estimate significant wave heights and dynamic water levels to better monitor for local conditions leading to impacts.

Abstract. The El Niño Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO) are known to influence coastal water levels along the East Coast of the United States. By identifying empirical orthogonal functions (EOFs), which coherently contribute from the Multivariate ENSO Index (MEI) to the AMO index (AMOI), we characterize both the expression of ENSO in the unsmoothed AMOI, and coherent relationships between these indices and interannual sea level anomalies at six stations in the Gulf of Mexico and western North Atlantic. Within the ENSO band (2–7 yr periods) the total contribution of MEI to unsmoothed AMOI variability is 79%. Cross correlation suggests that the MEI leads expression of the ENSO signature in the AMOI by six months, consistent with the mechanism of an atmospheric bridge. Within the ENSO band, essentially all of the coupling between the unsmoothed AMOI and sea level anomalies is the result of ENSO expression in the AMOI. At longer periods we find decadal components of sea level anomalies linked to the AMOI at three southern stations (Key West, Pensacola, Charleston), but not at the northern stations (Baltimore, Boston, Portland), with values of coherence ranging from 20 to 50%. The coherence of MEI to coastal sea level anomalies has a different structure and is generally weaker than that of the ENSO expressed AMOI influence, suggesting distinct physical mechanisms are influencing sea level anomalies due to a direct ENSO teleconnection when compared to teleconnections based on ENSO expression in the AMOI. It is expected that applying this analysis to extremes of sea level anomalies will reveal additional influences.

Patterns of variability in ocean properties are often closely related to large-scale climate pattern indices, and 2021 is no exception. The year 2021 started and ended with La Niña conditions, charmingly dubbed a “double-dip” La Niña. Hence, stronger-than-normal easterly trade winds
\nin the tropical south Pacific drove westward surface current anomalies in the equatorial Pacific; reduced sea surface temperature (SST) and upper ocean heat content in the eastern tropical Pacific; increased sea level, upper ocean heat content, and salinity in the western tropical Pacific;
\nresulted in a rim of anomalously high chlorophyll-a (Chla) on the poleward and westward edges of the anomalously cold SST wedge in the eastern equatorial Pacific; and increased precipitation over the Maritime Continent.
\nThe Pacific decadal oscillation remained strongly in a negative phase in 2021, with negative SST and upper ocean heat content anomalies around the eastern and equatorial edges of the North Pacific and positive anomalies in the center associated with low Chla anomalies. The South
\nPacific exhibited similar patterns. Fresh anomalies in the northeastern Pacific shifted towards the west coast of North America. 
\nThe Indian Ocean dipole (IOD) was weakly negative in 2021, with small positive SST anomalies in the east and nearly-average anomalies in the west. Nonetheless, upper ocean heat content was anomalously high in the west and lower in the east, with anomalously high freshwater flux and low sea surface salinities (SSS) in the east, and the opposite pattern in the west, as might be expected during a negative phase of that climate index.
\nIn the Atlantic, the only substantial cold anomaly in SST and upper ocean heat content persisted east of Greenland in 2021, where SSS was also low, all despite the weak winds and strong surface heat flux anomalies into the ocean expected during a negative phase of the North Atlantic
\nOscillation. These anomalies held throughout much of 2021. An Atlantic and Benguela Niño were both evident, with above-average SST anomalies in the eastern equatorial Atlantic and the west coast of southern Africa. Over much of the rest of the Atlantic, SSTs, upper ocean heat content, and sea level anomalies were above average.
\nAnthropogenic climate change involves long-term trends, as this year’s chapter sidebars emphasize. The sidebars relate some of the latest IPCC ocean-related assessments (including carbon, the section on which is taking a hiatus from our report this year). This chapter estimates that SST increased at a rate of 0.16–0.19°C decade−1 from 2000 to 2021, 0–2000-m ocean heat content warmed by 0.57–0.73 W m−2 (applied over Earth’s surface area) from 1993 to 2021, and global
\nmean sea level increased at a rate of 3.4 ± 0.4 mm yr−1 from 1993 to 2021. Global mean SST, which is more subject to interannual variations than ocean heat content and sea level, with values typically reduced during La Niña, was ~0.1°C lower in 2021 than in 2020. However, from 2020 to
\n2021, annual average ocean heat content from 0 to 2000 dbar increased at a rate of ~0.95 W m−2, and global sea level increased by ~4.9 mm. Both were the highest on record in 2021, and with year-on-year increases substantially exceeding their trend rates of recent decades.

The National Ocean Service (NOS) of National Oceanic and Atmospheric Administration is developing an operational nowcast/forecast system for the Gulf of Maine (GoMOFS). The system aims to produce real-time nowcasts and short-range forecast guidance for water levels, 3-dimensional currents, water temperature, and salinity over the broad GoM region. GoMOFS will be implemented using the Regional Ocean Model System (ROMS). This paper describes the system setup and results from a one-year (2012) hindcast simulation. The hindcast performance was evaluated using the NOS standard skill assessment software. The results indicate favorable agreement between observations and model forecasts. The root-mean-squared errors are about 0.12 m for water level, less than 1.5 °C for temperature, less than 1.5 psu for salinity, and less than 0.2 m/s for currents. It is anticipated to complete the system development and the transition into operations in fiscal year 2017.

A model to examine the impacts of long term sea level rise (SLR) is being implemented in the coastal North Carolina ecosystem. This area is particularly vulnerable to SLR, as a fragile system of barrier islands protects an extensive but sensitive estuarine system. The primary impact of SLR is to the hydrodynamic response of the system: circulation, tidal amplitude, and inundation patterns due to tides, winds, and storms can all change in response to rising sea level. Rates of SLR in the region are just under 3 mm/year and are increasing, and inundation is tied to inlet conveyance which can be modified by SLR. A Coastal Flooding Model (CFM) has been developed for the region by combining a finite element hydrodynamic model with a continuous bathymetric and topographic elevation dataset. The CFM domain extends from 90 km offshore of the Outer Banks to the 15 m topographic contour and from northern Currituck Sound south to the New River. The CFM provides high resolution of coastal features down to 20 m. High resolution topographic elevation data relative to the North American Vertical Datum of 1988 (NAVD 88) was combined with bathymetric sounding data relative to local tidal datums by transforming the tidal datums to NAVD 88 with the VDatum vertical transformation tool developed by the National Oceanic and Atmospheric Administration's (NOAA) National Ocean Service (NOS). The VDatum tool allows for transformation among nearly 30 different tidal, orthometric, and ellipsoidal vertical datums. A 6 m horizontal resolution continuous bathymetric/topographic (bathy/topo) Digital Elevation Model (DEM) was constructed for accurate modeling of inundation. The CFM is relative to the NAVD 88 vertical datum and was populated with DEM elevations where available and other topographic and bathymetric data relative to NAVD 88 elsewhere to create a continuous bathy/topo elevation field. A two-dimensional barotropic model is used to simulate the tidal response in the CFM to study changes due to SLR and will also be used to model regional synoptic wind events and hurricane storm surge propagation with SLR. Accurate simulation of inundation patterns is accomplished by high localized resolution in the coastal zone, continuous bathy/topo data, and an accurate wetting/drying algorithm. The CFM is validated against observational data before modification of initial and boundary water levels to represent eustatic SLR. The RMS error at tidal stations was calculated for the primary constituent amplitudes and phases. The average of these RMS amplitude errors is 7.8 x 10–3 m and the average of the RMS phase errors is 6.57°. Shoreline migration can be dynamically computed from the CFM simulation output as a function of SLR. Finally, the CFM will be coupled to submodels that characterize the ecological impact of SLR.

Annual average global mean sea level (GMSL) from satellite altimetry (1993–present; Beckley et al. 2021) reached a new high in 2023, rising to 101.4 mm above 1993 (Fig. 3.15a). This marks the 12th consecutive year (and 28th out of the last 30) that GMSL increased relative to the previous year, continuing a multi-decadal trend of 3.2±0.4 mm yr−1 and acceleration of 0.075±0.025 mm yr−2 in GMSL during the satellite altimetry era (Fig. 3.15a). A quadratic fit with corrections for the eruption of Mount Pinatubo (Fasullo et al. 2016) yields a climate-driven trend of 3.1±0.4 mm yr−1 and acceleration of 0.092±0.025 mm yr−2 (updated from Nerem et al. 2018).

Abstract Vulnerability of coastal regions to extreme events motivates an operational coupled inland‐coastal modeling strategy focusing on the coastal transition zone (CTZ), an area between the coast and upland river. To tackle this challenge, we propose a top‐down framework for investigating the contribution of different processes to the hydrodynamics of CTZs with various geometrical shapes, different physical properties, and under several forcing conditions. We further propose a novel method, called tidal vanishing point (TVP), for delineating the extent of CTZs through the upland. We demonstrate the applicability of our framework over the United States East and Gulf coasts. We categorize CTZs in the region into three classes, namely, without estuary (direct river–coast connection), triangular‐, and trapezoidal‐shaped estuary. The results show that although semidiurnal tidal constituents are dominant in most cases, diurnal tidal constituents become more prevalent in the river segment as the discharge increases. Also, decreasing the bed roughness value promotes more significant changes in the results than increasing it by the same value. Additionally, the estuary promotes tidal energy attenuation and consequently decreases the reach of tidal signals through the upland. The proposed framework is generic and extensible to any coastal region.

NOAA's National Ocean Service applies hydrodynamic models for the development, transition and implementation of operational forecast systems in U.S. estuaries, ports, lakes and the coastal ocean. These models and systems have applications in the support of safe and efficient marine navigation and emergency response as well as marine geospatial and ecological applications. There are currently nine water bodies in which operational forecast systems are functioning (the Chesapeake Bay, the Port of New York and New Jersey, Galveston Bay, the St. Johns River, and the five Great Lakes). Operational forecast systems are under development for the Columbia River, Delaware Bay, Tampa Bay, Cook Inlet, and elsewhere. Once tested, fully evaluated, and deemed accurate by National Ocean Service standards, experimental forecast systems are transitioned into the operational environment. The technical components of a real-time estuarine modeling system are described in terms of a "standard" Coastal Ocean Modeling Framework (COMF) which increases the efficiency of research, development, transition and operations. The COMF includes the essential operational management of observations and forecasts of atmospheric, coastal and riverine inputs, as well as the operational quality control and dissemination of results. It also includes protocols and software for the skill assessment of operational forecast systems. The COMF abides by Integrated Ocean Observing System and Earth System Modeling Framework standards. It is intended to stimulate a community approach to coastal modeling by providing tools, observational data, and a Model Evaluation Environment with which to configure, execute, and determine model uncertainties. A future strategy of transitioning from individual port or estuarine models to a regional modeling approach is also being developed to enhance the efficiency of development and operations.