Accurate and rapid detection and assessment of tsunamis is critical for effective mitigation. We show here that a modest ∼10 cm tsunami from the M8.8 27 Feb 2010 Maule, Chile earthquake was detected ...by kinematic Global Positions System (GPS) solutions from a ship underway in the open ocean ‐ the first time shipboard tsunami detection has been achieved. Our results illustrate how the commercial shipping fleet represents a vast infrastructure of potential open ocean GPS platforms on shipping lanes that provide extremely good spatial coverage around most tsunamigenic source regions. Given the affordability of geodetic GPS systems, and ever‐improving satellite communications, it would be possible to equip a significant portion of the shipping fleet with real‐time‐streamed GPS systems and create a cost‐effective tsunami monitoring network with denser and more distributed coverage. We project that such a system would have detected the 2004 Indian Ocean tsunami in less than an hour.
Key Points
A 10 cm tsunami was detected in the open ocean using ship‐borne GPS
Key tsunami wave parameters can be estimated, even for moderate to small signals
The commercial shipping fleet could be used to form a tsunami monitoring network
Similar in strength to hurricanes, Extratropical Cyclones (ECs) are responsible for innavigable sea states, coastal inundation and erosion, and subsequent destruction to coastal infrastructure. ...Across modern operational wave models, there exists a known systematic underestimation of wave heights during these extreme events. Using a global database of EC storm tracks and 36 years of satellite altimeter data, we examine EC structure and assess model performance through storm centered composite analyses of significant wave height ( Hs) and U10 wind speed ( |U10|). Through the collocation of satellite altimeter observations with a state-of-the-art reanalysis product (ERA5), we investigate model performance with respect to |U10| and Hs within ECs of varying intensities. By rotating our data reference frames, we align all storm directions to account for asymmetry in EC wind fields and subsequent increased wave growth This rotation results in the organization of the strongest wind speed and Hs, as well as trends in the ERA5 performance. A characteristic EC radii is calculated and used to normalize data coordinates in the storm centered reference frame, which highlights the organization of EC structures. Performance metrics are then compared within different EC quadrants to explore the relationship between wind forcing accuracy and underestimation of Hs.
•Dispersed citrate capped silver nanoparticles were synthesised and characterised.•Nanoparticle aggregation was assessed in Daphnia magna diluted and undiluted media.•Aggregation was assessed by TEM ...and AFM measurements.•There was a significant reduction in toxicity in media1 compared to that in media10.
Due to the widespread use of silver nanoparticles (AgNPs), the likelihood of them entering the environment has increased and they are known to be potentially toxic. Currently, there is little information on the dynamic changes of AgNPs in ecotoxicity exposure media and how this may affect toxicity. Here, the colloidal stability of three different sizes of citrate-stabilized AgNPs was assessed in standard strength OECD ISO exposure media, and in 2-fold (media2) and 10-fold (media10) dilutions by transmission electron microscopy (TEM) and atomic force microscopy (AFM) and these characteristics were related to their toxicity towards Daphnia magna. Aggregation in undiluted media (media1) was rapid, and after diluting the medium by a factor of 2 or 10, aggregation was reduced, with minimal aggregation over 24h occurring in media10. Acute toxicity measurements were performed using 7nm diameter particles in media1 and media10. In media10 the EC50 of the 7nm particles for D. magna neonates was calculated to be 7.46μgL−1 with upper and lower 95% confidence intervals of 6.84μgL−1 and 8.13μgL−1 respectively. For media1, an EC50 could not be calculated, the lowest observed adverse effect concentration (LOAEC) of 11.25μgL−1 indicating a significant reduction in toxicity compared to that in media10. The data suggest the increased dispersion of nanoparticles leads to enhanced toxicity, emphasising the importance of appropriate media composition to fully assess nanoparticle toxicity in aquatic ecotoxicity tests.
Waves overtop berms and seawalls along the shoreline of Imperial Beach (IB), CA when energetic winter swell and high tide coincide. These intermittent, few-hour long events flood low-lying areas and ...pose a growing inundation risk as sea levels rise. To support city flood response and management, an IB flood warning system was developed. Total water level (TWL) forecasts combine predictions of tides and sea-level anomalies with wave runup estimates based on incident wave forecasts and the nonlinear wave model SWASH. In contrast to widely used empirical runup formulas that rely on significant wave height and peak period, and use only a foreshore slope for bathymetry, the SWASH model incorporates spectral incident wave forcing and uses the cross-shore depth profile. TWL forecasts using a SWASH emulator demonstrate skill several days in advance. Observations set TWL thresholds for minor and moderate flooding. The specific wave and water level conditions that lead to flooding, and key contributors to TWL uncertainty, are identified. TWL forecast skill is reduced by errors in the incident wave forecast and the one-dimensional runup model, and lack of information of variable beach morphology (e.g., protective sand berms can erode during storms). Model errors are largest for the most extreme events. Without mitigation, projected sea-level rise will substantially increase the duration and severity of street flooding. Application of the warning system approach to other locations requires incident wave hindcasts and forecasts, numerical simulation of the runup associated with local storms and beach morphology, and model calibration with flood observations.
From Tides to Mixing along the Hawaiian Ridge Rudnick, Daniel L.; Boyd, Timothy J.; Brainard, Russell E. ...
Science (American Association for the Advancement of Science),
07/2003, Letnik:
301, Številka:
5631
Journal Article
Recenzirano
The cascade from tides to turbulence has been hypothesized to serve as a major energy pathway for ocean mixing. We investigated this cascade along the Hawaiian Ridge using observations and numerical ...models. A divergence of internal tidal energy flux observed at the ridge agrees with the predictions of internal tide models. Large internal tidal waves with peak-to-peak amplitudes of up to 300 meters occur on the ridge. Internal-wave energy is enhanced, and turbulent dissipation in the region near the ridge is 10 times larger than open-ocean values. Given these major elements in the tides-to-turbulence cascade, an energy budget approaches closure.
The International Cancer Microbiome Consortium (ICMC) is a recently launched collaborative between academics and academic-clinicians that aims to promote microbiome research within the field of ...oncology, establish expert consensus and deliver education for academics and clinicians. The inaugural two-day meeting was held at the Royal Society of Medicine (RSM), London, UK, 5-6 September 2017. Microbiome and cancer experts from around the world first delivered a series of talks during an educational day and then sat for a day of roundtable discussion to debate key topics in microbiome-cancer research. Talks delivered during the educational day covered a broad range of microbiome-related topics. The potential role of the microbiome in the pathogenesis of colorectal cancer was discussed and debated in detail with experts highlighting the latest data in animal models and humans and addressing the question of causation versus association. The impact of the microbiota on other cancers-such as lung and urogenital tract-was also discussed. The microbiome represents a novel target for therapeutic manipulation in cancer and a number of talks explored how this might be realised through diet, faecal microbiota transplant and chemotherapeutics. On the second day, experts debated pre-agreed topics with the aim of producing a consensus statement with a focus on the current state of our knowledge and key gaps for further development. The panel debated the notion of a 'healthy' microbiome and, in turn, the concept of dysbiosis in cancer. The mechanisms of microbiota-induced carcinogenesis were discussed in detail and our current conceptual models were assessed. Experts also considered co-factors in microbiome-induced carcinogenesis to conclude that the tripartite 'interactome' between genetically vulnerable host, environment and the microbiome is central to our current understanding. To conclude, the roundtable discussed how the microbiome may be exploited for therapeutic benefit in cancer and the safety implications of performing such research in oncology patients.
Extratropical cyclones (ECs) produce comparable wave heights and hazardous sea states to those under hurricanes. With strong wind speeds and considerably larger diameters, the impact of ECs on the ...global wave climate is substantial. Because ECs occur more frequently, move more quickly, and exist in a large variety of sizes and shapes, these storms are not as well documented. Here, we present findings from a global EC tracking algorithm aimed at creating an EC database of wave producing storms. We focus on the major ocean basins of extratropical cyclone activity: The North Atlantic, North Pacific, and Southern Oceans. Our tracking algorithm uses mean sea level pressure fields from the European Centre for Medium‐Range Weather Forecasts (ECMWF) high resolution, advanced data assimilating, ERA5 reanalysis over the years 1979–2020. The 42 year‐long data set of thousands of cyclone tracks allows seasonal patterns and longer‐term trends of EC activity to be analyzed in these ocean regions. In addition, we employ 36 years of satellite radar altimeter‐derived significant wave height (Hs) data from 14 inter‐calibrated satellite missions to study the wave climate induced by the identified ECs in each basin. The resulting wave climatology compares well with previous results in the mid to high latitudes. We then analyze average wave heights under different EC characteristics, including cyclone translational speed and maximum winds, which have strong effects on wave height variability. Finally, a brief analysis of EC and wave climate under positive and negative phases of the North Atlantic Oscillation is presented.
Plain Language Summary
Large storms which occur outside of the tropics, known as extratropical cyclones (ECs), create very large waves that can surpass that of tropical cyclones. These extreme sea states are responsible for coastal hazards including erosion and surge induced flooding. While tropical cyclones, or hurricanes, are well documented by devoted agencies, ECs are more difficult to track given their high occurrence, fast movement, and inconsistency of size and shape. Here we present the results from a tracking algorithm, applied over a 42 year period, aimed at documenting the many ECs which occur over the global oceans with specific focus placed on wave development within these storms. We use satellite measurements of wave heights within the tracked ECs to investigate wave growth and overall wave climate within these storms. In addition to studying the seasonality of ECs and associated wave activity, we show the regional influence of longer time‐scale climate variability on the same.
Key Points
A new extratropical cyclone tracker is applied to 42 years of global reanalysis to investigate climatology and seasonality of storms
Ocean basin composite analyses of satellite‐derived significant wave height observations show wave dependence on cyclones characteristics
The North Atlantic Oscillation climate modes show strong influence on cyclone activity and induced wave climate in the North Atlantic
Landfalling tropical cyclones (TC) generate extreme waves, introducing significant property, personal, and financial risks and damage. Accurate simulations of the sea state during these storms are ...used to support risk and damage assessments and the design of coastal structures. However, the TCs generate a complex surface gravity wave field as a result of the inherently strong temporal and spatial gradients of the wind forcing. This complexity is a significant challenge to model. To advance our understanding of the performance of these models on the eastern seaboard of the United States, we conduct an assessment of four hindcast products, three based on WAVEWATCH-III and the other using the Wave Modeling project, for six major landfall TCs between 2011–2019. Unique to our assessment was a comprehensive analysis of these hindcast products against an array of fixed wave buoys that generate high quality data. The analysis reveals a general tendency for the wave models to underestimate significant wave height (Hs) around the peak of the TC. However, when viewed on an individual TC basis, distinct Hs error patterns are evident. Case studies of hurricanes Sandy and Florence illustrate complex Hs bias patterns, likely resulting from various mechanisms including insufficient resolution, improper wind input and source term parameterization (e.g., drag coefficient), and omission of wave–current interactions. Despite the added challenges of simulating complex wave fields in shallow coastal waters, the higher resolution Wave Information Study and National Centers for Environmental Prediction (ST4 parameterization only) hindcasts perform relatively well. Results from this study illustrate the challenge of simulating the spatial and temporal variability of TC generated wave fields and demonstrate the value of in-situ validation data such as the north Atlantic buoy array.
The Coastal Data Information Program (CDIP) provides wave data to the public in near real-time, maintains an operational wave model for the California coast, and is engaged in ocean wave research on ...a global scale. CDIP’s array of moored wave buoy stations are instrumented with Datawell Waveriders. CDIP’s recent work to improve monitoring capabilities for directional surface wave spectra, surface current, and temperature is described. This includes data quality assurance and control, real-time alerts, telemetry and dissemination information technology infrastructure and methodology, data visualization tools, and mooring and instrumentation innovation. CDIP’s goal is to maximize data reliability, availability, accuracy, and precision. Validation of commonly used wave models – operational, hindcast, and forecast – with CDIP data is automated to provide assessments of relative skills at a variety of coastal locations and wave conditions. Wave heights measured by the buoys typically exceed modeled heights during the most energetic events, such as hurricanes, nor’easters, and bomb cyclones. In a practical validation example, the global wave model used to drive CDIP’s California coastal wave forecasts was recently changed, based on comparisons against buoy data. Forecast performance has improved for swell events, which are a challenge to model accurately in the Southern California Bight.
The influence of a deep (30 m), narrow (30 m) cross‐shore channel on the circulation and wave‐induced setup over a shallow (∼0.5 m) and wide (∼400 m) shore‐attached fringing reef is examined using ...field measurements collected at Ipan, Guam. Mean currents on the reef flat over a 7‐week study period during mid and high tides when the reef is submerged are directed toward the channel with the alongshore component of the current increasing with proximity to the channel. The cross‐shore component of the reef flat current is directed onshore at the sensors in the far‐field of the channel with a weak offshore flow at the current meter located closest to the channel (∼760 m to the north). Low‐frequency fluctuations of the alongshore reef flat current and offshore channel current are significantly correlated and with the incident significant wave height. Mean and low‐frequency fluctuating currents are forced by the spatially variable wave‐driven setup, modulated by tidal elevation, which creates a pressure gradient over the reef flat due to the channel where waves do not break. The dominant alongshore momentum balance on the reef flat is between the pressure gradient and bottom stress, with an inferred drag coefficient of CD ∼ 0.01. A simple analytical model is presented that is consistent with the observations and delineates the near‐ and far‐field of the channel as a function of the aspect ratio of the reef. Observations from a longer deployment of channel currents are highly correlated with incident wave height in distinct tidal level bands.
Plain Language Summary
Observations of waves, water levels, and currents at Ipan, Guam, are analyzed to determine how wave‐driven flow on a shore‐attached fringing reef is influenced by a cross‐reef channel. Breaking waves at the outer reef cause elevated water levels over the reef flat. At the deep, narrow channel wave breaking is suppressed, resulting in a pressure gradient that forces a rip circulation toward and out the channel. The dominant physical balance between bottom friction and this pressure gradient leads to an estimate of a drag coefficient CD ∼ 0.01. The wave‐driven channel current is modulated by tidal submergence of the reef flat, and the flow scales with offshore wave heights at high tidal levels. A simple analytical model describes the spatially variable pressure gradient and defines the region of influence of the channel as a function of the length to width ratio of the reef flat.
Key Points
Breaking wave setup over a shore‐attached fringing reef is suppressed by a deep, narrow channel generating an alongshore pressure gradient
A steady rip circulation on the reef flat and out the channel is generated that is highly correlated with wave height and tidal level
The balance between bottom drag and the induced pressure gradient leads to an inferred drag coefficient of CD ∼0.01
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