With sea level rise, erosion, and human disturbances affecting coastal areas, strategies to protect and stabilize existing shorelines are needed. One popular solution to stabilize while conserving ...intertidal habitat is the use of “living shoreline” techniques which are designed to mimic natural shoreline communities by using native plants and animals. However, little information is available on the success of living shoreline stabilization. This project evaluated the wave energy attenuation associated with living shorelines that contained Crassostrea virginica (eastern oyster) and/or Spartina alterniflora (smooth cordgrass) in a wave tank. Four living shoreline techniques were assessed, including a control (sediment only), oysters alone, cordgrass alone, and a combination of oysters plus cordgrass. Time since deployment (newly deployed, one-year after deployment) was also assessed to see how wave energy attenuation changed with natural oyster recruitment and plant growth. Wave energy was calculated for each newly deployed and one-year old shoreline stabilization treatment using capacitance wave gauges and generated waves that were representative of boat wakes in Mosquito Lagoon, a shallow-water estuary in Florida. All one-year old treatments attenuated significantly more energy than newly-deployed treatments. The combination of one-year old S. alterniflora plus live C. virginica was the most effective as this treatment reduced 67 % of the wave energy created by a single recreational boat wake, compared to bare sediment. Natural resource managers and landowners facing shoreline erosion issues can use this information to create effective stabilization protocols that preserve shorelines while conserving native intertidal habitats.
Numerical modeling has proven to be a useful method for simulating internal tides within the coastal ocean. Monterey Bay is a location that experiences energetic semidiurnal internal tides, and they ...are pronounced within Monterey Submarine Canyon. Numerical simulations and field measurements indicate that the baroclinic energy fluxes there are spatially variable, leading to locations of positive and negative baroclinic energy flux divergences. Results derived from a SUNTANS (Stanford Unstructured Nonhydrostatic Terrain-following Adaptive Navier-Stokes Simulator) model simulation show that Monterey Submarine Canyon's baroclinic power is net dissipative (–8.3 MW). However, sources and sinks exist throughout the canyon, and they permeate the study domain. One way to understand internal tide power is related to the ratio of the bathymetric slope (γ) to the linear internal wave characteristic slope (s). Results show large and consistent integrated surpluses of baroclinic power between 0.5 ≤γ/s ≤ 5.5 (includes the critical ratio); some net surpluses exist whenγ/s > 5.5, but are mixed with dissipative power results. Whenγ/s < 0.5, integrated power is net dissipative.
Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and ...the turbulent mixing caused by their breaking, they affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis, sediment and pollutant transport and acoustic transmission; they also pose hazards for man-made structures in the ocean. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects. For over a decade, studies have targeted the South China Sea, where the oceans' most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. Here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of >200-metre-high breaking internal waves in the region of generation that give rise to turbulence levels >10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
The barrier island located off the coast of Chatham, Massachusetts, known as Nauset Beach, extends approximately 14.5 kilometers north to south terminating at Chatham Inlet. This inlet was formed ...during a major storm in 1987, and since then has been the only inlet into the Pleasant Bay estuary. This estuary exhibits a recurring process of breaching and closing, and in 2007 a large storm combined with low lying topography caused a breach in the barrier island approximately four kilometers north of the existing inlet. Since then this breach has deepened and widened significantly forming a new inlet into Pleasant Bay. Using a numerical model, this study explores what impacts this breach may have on the Pleasant Bay system in terms of tidal hydrodynamics and residence time, a proxy for water quality. Results of the breach include an increase in peak high tide on the order of 15%, a decrease in the system residence time from 0.9 to 0.7 days, and decreases in the peak ebb and flood currents through the pre-existing inlet of approximately 10%
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Internal gravity waves, the subsurface analogue of the familiar surface gravity waves that break on beaches, are ubiquitous in the ocean. Because of their strong vertical and horizontal currents, and ...the turbulent mixing caused by their breaking, they affect a panoply of ocean processes, such as the supply of nutrients for photosynthesis, sediment and pollutant transport and acoustic transmission; they also pose hazards for man-made structures in the ocean. Generated primarily by the wind and the tides, internal waves can travel thousands of kilometres from their sources before breaking, making it challenging to observe them and to include them in numerical climate models, which are sensitive to their effects. For over a decade, studies have targeted the South China Sea, where the oceans' most powerful known internal waves are generated in the Luzon Strait and steepen dramatically as they propagate west. Confusion has persisted regarding their mechanism of generation, variability and energy budget, however, owing to the lack of in situ data from the Luzon Strait, where extreme flow conditions make measurements difficult. Here we use new observations and numerical models to (1) show that the waves begin as sinusoidal disturbances rather than arising from sharp hydraulic phenomena, (2) reveal the existence of .200- metre-high breaking internal waves in the region of generation that give rise to turbulence levels .10,000 times that in the open ocean, (3) determine that the Kuroshio western boundary current noticeably refracts the internal wave field emanating from the Luzon Strait, and (4) demonstrate a factor-of-two agreement between modelled and observed energy fluxes, which allows us to produce an observationally supported energy budget of the region. Together, these findings give a cradle-to-grave picture of internal waves on a basin scale, which will support further improvements of their representation in numerical climate predictions.
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