Source: https://marine.unh.edu/outreach-events/graduate-research-symposium
Timestamp: 2019-04-19 05:12:49+00:00

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This symposium is designed to showcase graduate student research, to build awareness of UNH marine research activities, and enhance interdisciplinary connections within the School of Marine Science and Ocean Engineering community. This one-day symposium will include a series of graduate student oral presentations, a keynote address, poster presentation reception and conclude with an award ceremony.
Oral Presentations & Keynote: 1 p.m.
Reception & Poster Session: 4:30 p.m.
The ocean itself is changing systematically due to human activities. Meanwhile, a spectrum of industries is crowding the oceans, especially near shore and in the exclusive economic zones that cover shelves and extend 200 miles from land. I will inventory developments associated with extracting energy, minerals, and water itself; shipping goods and information through cables and pipelines as well as on vessels; building and operating boats; harvesting ocean life; feeding and lodging tourists and living along coasts; disposing of wastes; and researching and monitoring to forecast the weather, improve safety, and protect the environment. Fulfilling these functions is populating the maritime environment with oceans a human-made “ocean of things.” Implications include multiplication of operational constraints; diminution of surprise and stealth; resumption of Great Power competition; new infrastructure vulnerabilities; S&T competition, where data is the new oil; and blurred lines among security, commercial, environmental, scientific interests.
Mass loss from the Greenland ice sheet has increased rapidly in the last two decades and has contributed significantly to observed sea level rise. The most pronounced change is occurring where ice sheets are grounded below sea level, due to enhanced interaction with warming ocean waters. However, our ability to predict future sea level rise is hampered by our limited knowledge of these glacial systems, including the regional water mass distribution and circulation responsible for that enhanced ocean-ice interaction. The Petermann Expedition of August 2015 encompassed a broad range of data collection in an effort to characterize the Petermann Glacier system, a marine-terminating glacier with a floating ice tongue that has undergone dramatic changes in the last decade. During the expedition, sonars were used to map the water column, generating a continuous dataset over 30 days. This mapping revealed extensive acoustic scattering layers, so called because the components of the layer – typically zooplankton – cause the acoustic energy to scatter much as it does when it encounters the seabed. The layer was observed to change depth in a spatially consistent manner and corresponded to our general, but limited understanding of the complex circulation pattern in the study area. Shipboard insolation data and satellite-derived light attenuation data were used to rule out response to light as the primary reason for changes in the scattering layer depth. Comparison to salinity and temperature measurements were used to demonstrate a pattern in the scattering layer depth distribution related to circulation, confirming that the continuous record provided by acoustics can supplement point observations of temperature and salinity to provide a more complete picture of regional oceanography and the glacial system as a whole.
An ocean mapping survey was conducted over the Southern California Antisubmarine Warfare Range hydrophone range to characterize the radiation pattern of the R/V Sally Ride's EM 122 (12 kHz) Kongsberg multibeam echosounder. Spanning a 2000 square kilometer area, the 89-hydrophones in the range, combined with the mapping survey, provided the opportunity to study the contribution of this anthropogenic noise to the marine soundscape. The soundscape was characterized and compared at select hydrophones on the range before and during the multibeam survey. One second averages of the sound level were calculated over the data collection period. Sound level percentiles (P1, P10, P50, P90 and P99) were calculated for the full spectrum (1 Hz- 48 kHz) and select frequency bands, and spectral probability density plots were generated for each time period. Frequency correlation matrices were produced for each time period and compared using difference matrices to identify changes in the soundscape. The results are placed in the context of the auditory scene of Cuvier's beaked whales resident on the range by applying a mid-frequency marine mammal weighting function. [Work supported by NOAA, ONR, and Scripps Institute of Oceanography].
Advances in multibeam sonar mapping and data visualization have increasingly brought to light the subtle integration errors remaining in bathymetric datasets. Traditional field calibration procedures, the patch test, just account for static orientation bias and sonar to position latency. However, this ignores the generally more subtle integration problems that generate time varying depth errors.
Such dynamic integration errors are the result of an unknown offset in one or more of orientation, space, sound speed or time between the sonar and ancillary sensors. Such errors are systematic, and thus should be predictable, based on their relationship between the input data and integrated output. A first attempt at addressing this problem utilized correlations between motion and ping-averaged residuals . The known limitations of that approach, however, included only being able to estimate the dominant signal, imperfectly accounting for irregular sounding distribution and it only working in shallow water.
This presentation discusses a new and improved means of utilizing the dynamics of the integration error signatures which can address multiple issues simultaneously, better account for along-track sounding distribution, and is not restricted to the shallow water geometry. The motion-driven signatures of multiple integration errors may be simultaneously identified through individually considering each sounding’s input-error relationship from extended sections of a single swath. Such an approach provides a means of underway system optimization using nothing more than the bathymetry of typical seafloors acquired during transit. Successful estimation, however, imposes conditions of significant vessel motion, and smooth, gently rolling bathymetry. Initial results of the new algorithm are presented using data generated from a simulator (with known inputs and integration errors) to test the efficacy of the method.
 J. Hughes Clarke, “Dynamic Motion Residuals in Swath Sonar Data : Ironing out the Creases,” International Hydrographic Review, Mar. 2003.
Pteropods are pelagic, free-swimming sea snails that have a thin aragonite shell that makes them fairly susceptible to the changing ocean chemistry that is associated with ocean acidification (OA). Pteropods are an important part of the ecosystems they are found in as they are a part of the diet of species at multiple trophic levels and help to facilitate the movement of carbon throughout the water column. Previous studies have shown that pteropods are sensitive to OA conditions as they have shown tendencies for shell dissolution, increased shell opacity, and decreased sinking speeds in more acidic conditions. Changes in other environmental conditions associated with OA, such as rising temperature and salinity, may also impact pteropods. Increased understanding about how the distribution of pteropods has changed as temperature and salinity conditions change can provide insight about how sensitive pteropods may be to these variables. The ECOMON dataset from NOAA Northwest Fisheries Department was used to determine if and how pteropod distribution has changed in the Atlantic Ocean off the east coast of the United States. Statistical analyses performed on the dataset determined there is a relationship between temperature, salinity, pteropod abundance, and their location over time. Ongoing research is further exploring the relationship between pteropod abundance and these environmental conditions. Understanding how pteropod populations respond to these changing variables is important in further establishing them as bioindicators for OA.
Invasive seaweeds are a potent threat to biodiversity in coastal ecosystems worldwide. Only a subset of all introduced seaweeds have made the leap from being locally problematic to global invaders. Here, we explore the use of species distribution models for analyzing the regional-scale distribution of invasive macroalgae. In particular, we attempted to identify locations that may be vulnerable to the introduction of certain highly successful invaders. Models were built for two species: Undaria pinnatifida and Dasysiphonia japonica. Both species are native to temperate Asia, but have become established in disparate regions of the world. Accuracy of the constructed models was assessed by comparing predicted highly suitable habitat to known occurrence records. They were then used to identify areas that may be vulnerable to introduction by either species in the future: U. pinnatifida is already established in a number of areas worldwide, but has yet to reach the Gulf of Maine. Dasysiphonia japonica is relatively recent to the Gulf of Maine, and is not as globally widespread, but may have the potential to spread beyond its current extent.
The objective of the research is to characterize the potential role of marine snow and suspended minerals in the fate of spilled oil in Cook Inlet, Alaska. While extensive research has been conducted on minerals aggregating with spilled oil, larger organic aggregates, such as marine snow, have only recently been studied as a transport mechanism. This knowledge gap in understanding the fate of oil was highlighted following the Deepwater Horizon (DWH) blowout in the Gulf of Mexico (2010) when a significant percentage of the spilled oil was observed sinking to the seafloor as a result of association with marine snow. Research following the DWH blowout suggests both marine snow and mineral sediment are significant pathways that must be considered during an oil spill response. The U.S. Geological Survey and others have noted that an understanding of baseline marine snow conditions in areas of petroleum exploration and extraction is urgently needed. In the summer of 2018 and in January 2019, sinking particles were collected with a surface-tethered sediment trap in eastern Cook Inlet. The summer particle mass flux ranged from 30 to 220 g m-2 day-1. The particle composition ranged from 19 to 38% organic with little variation between three main sites. The data collected, in addition to local knowledge, was used to develop a procedure for laboratory scale roller table experiments which simulate surface oil and particle interaction. These experiments will be conducted May through August 2019 and paired with sediment trap data to quantify the potential for oil to sink via particle association. This presentation will summarize findings from field and laboratory work, and include a discussion on the relevance of this research to oil spill response decision-making in a larger context.
Military testing and training around the United States has resulted in over 10 million acres of property in underwater environments, potentially containing military weapons. The weapons, or munitions, are difficult to locate, capable of sudden movement, and a danger to marine life and the public. Improved understanding of their mobility in underwater environments is vital for safe and cost-effective munition recovery. A pressure-mapped model munition (PMM) was designed and fabricated to resolve the role of dynamic pressure gradients on munition mobility. The PMM is an untethered instrument, containing all electronics necessary to retrieve, time, and store data. The PMM is capable of detecting and measuring surface pressure gradients, orientation and positional changes, and uses an acoustic tracker for retrieval after deployments.
The surface pressure mapping was accomplished using an array of sixteen 3mm-diameter, diaphragm pressure sensors. Orientation changes were recorded using an Inertial Measurement Unit (IMU). All data is stored to an on-board microSD card and recorded with time stamps. The PMM was evaluated through several full-scale laboratory and field experiments to determine its accuracy in detecting hydrostatic pressure changes, orientation changes, passing waves, and environmental changes, such as being submerged in a sand bed. The PMM was able to resolve both the overlying progressive wave signal as well as the deviations due to vortex shedding around the cylinder. Improvements in the original PMM design were implemented into a newly revised PMM 2.0. Further lab and field testing are underway to investigate the increased resolution of vortex shedding due to pressure gradients, and positional changes of the PMM. The results of this research suggest that vortex shedding may significantly contribute to the burial of free-standing objects. Additionally, these results can be more broadly applied to relationships between sediment and fluid structures.
Environmental DNA (eDNA), or DNA present in an environmental sample, is emerging as a powerful tool to detect species present in an ecosystem without having to actually capture and identify individual organisms. Fish, invertebrates, and other animals shed DNA through fragments of tissue, reproductive and waste products into the environment they live in. High throughput sequencing of DNA extracted from environmental samples can identify hundreds of plant and animal species at relatively low cost. These methods have the potential to transform monitoring and management of coastal systems, but we are really only beginning to understand how to effectively apply the technology to achieve useful, reproducible results. This talk will focus on emerging eDNA methods for coastal and estuarine monitoring, including potential management applications, examples of relevant research, and development of standardized methods. I will present examples from a pilot environmental eDNA monitoring program being implemented at several National Estuarine Research Reserve (NERR) sites in New England and Oregon, where metabarcoding and single-species PCR methods are applied to species detection with a focus on fish and crabs. Sampling is being conducted in coordination with traditional monitoring programs including seine surveys, fish ladder counts, crab trapping and plankton tows to allow direct comparison to traditional methods. A challenge in implementing eDNA monitoring is the interpretation and analysis of the results, I will discuss our bioinformatics approach, and efforts to provide accessible analysis tools for our end users.
Graduate students with research focused in marine science or ocean engineering are welcome to present their research during the Poster Session and Reception. Posters registered by 5:00 pm on April 25, 2019 will be eligible for the poster competition. Prizes will be awarded to the two top poster presenters. To qualify for the award, you must register by the deadline. Please have your abstract title and content (350 words or less) prepared at time of registration.
Posters can be set up in the Piscataqua Room anytime by 12:00 pm on May 2, 2019. Easel and foam core will be provided. For poster tips, visit the Undergraduate Research Conference Poster Presentation Help page.
Effects of small-scale turbulence on phytoplankton growth and metabolism.
Our current understanding of how turbulence affects small planktonic organisms is based on fluid dynamic theory, ocean models, and laboratory experiments that often have conflicting results. Atmospheric models predict that global temperature rise associated with climate change will affect turbulence patterns within the marine photic zone, where phytoplankton reside. To investigate how small-scale turbulence affects growth (growth rates, cell counts and extracted chlorophyll, and nutrient quotas) and metabolism (production of transparent exopolymer particles (TEP)) of marine primary producers, phytoplankton in monoculture and natural assemblages were incubated under a range of turbulent treatments. Results indicate that early in exponential growth of the monocultures, cell-specific TEP was higher with increased turbulence. During mid- and late exponential growth, there were no measurable differences in phytoplankton growth and TEP production as a function of turbulence. However, nutrient quotas were higher in the more turbulent tanks in phytoplankton cells >15 µm in length. Data from this study suggest that changes in turbulence in marine photic zones could result in increased nutrient storage in larger phytoplankton cells, as predicted by numerical models, but may not greatly affect the global carbon cycle via changes in TEP production.
While many trajectory models exist to predict the movement of oil floating in or on water, few are designed to address heavy oil on the bottom of water bodies. In addition, remobilization (erosion) of the material into the water column is also difficult to predict. While properties such as adhesion, viscosity and density of oil may be readily measured, the critical shear stress (CSS) and the effect of (current) velocity, salinity, and temperature are virtually unknown for most heavy oils. The Center for Spills and Environmental Hazards (CSE) has a 4,000 L annular flume, with a water depth of 0.43 m. An inner rectangular flume (1.2 m length, 0.2m width, 0.9 m height), placed inside the annular flume, was preceded by two flow straighteners to reduced turbulence and produce a uniform, one dimensional flow field. The current is generated by an electric thrust motor and measured in 3D by a Nortek AS (Norway) Vectrino II Profiling Velocimeter. A 20g circle of Alberta bitumen (SG = 0.998) was placed on a laminated grid (1cm2 square pattern) at the bottom of the straight flume. A total of 2.3m3 of water was then gradually added to the flume. The electric motor was started and the profiler began collecting data. Two cameras, placed along the side and above the oil, collected video of the erosions and length/width changes of the oil. Conditions were held steady for one hour once the desired current velocity was achieved. Temperatures, current velocity (X, Y, Z), and digital videographic data were collected during each run. Erosions and percent lengthening of the oil was monitored as a function of water temperature, salinity and velocity. The turbulent kinetic energy (TKE) method was used to calculate the bed shear stress (BSS). In addition to the expected impact of higher temperature on the movement along the bed and erosion into the water column, the viscoelastic and shear-thinning properties of the bitumen played a role in its behavior (lowering of viscosity at higher BSS slowing erosions and movement) and must be considered when predicting its behavior during a spill.
The recent emergence of Vibrio parahaemolyticus disease in the Northeast US is a challenge for public health safety, resource management and industry regulation. Most V. parahaemolyticus strains are believed to be non-pathogenic and those that do cause disease are contracted from the consumption of raw or undercooked seafood and shellfish from warm water environments. It is believed that co-occurring climate change associated environmental trends may be an underlying factor behind this new disease pattern. Surveillance of V. parahaemolyticus concentrations and coincident environmental conditions in the Great Bay Estuary has produced a long-term data set that can be applied to identify to conditions that may contribute to V. parahaemolyticus population dynamics in this region. Non-linear, temporal and multivariate analysis were applied to environmental and climatic data to determine that surface water temperature, average pH, average chlorophyll a, maximum turbidity and salinity were key variables to estimate V. parahaemolyticus concentration in oysters from the GBE. Focused studies into plankton dynamics suggest season specific plankton communities that are significantly associated with the variation that is observed in V. parahaemolyticus populations in oysters. The application of these results provides the basis to characterize ecological relationships for V. parahaemolyticus in this region and will be used to develop forecasting models of risk conditions for industry, shellfish resource managers and public health agencies in the Northeast.
Field observations from an Odom Echotrac vertical-incidence 200 kHz echosounder were used to estimate seafloor mud fraction (fractional sediment size distribution less than 62.5 mm) in a tidally-dominated estuary with sediment distribution ranging 0–78% mud. Observations were obtained in water depths ranging 0.5–24 m in the Little Bay, New Hampshire. Backscatter waveform envelopes associated with the first acoustic interaction with the seafloor were analyzed and defined by seven properties: maximum and mean intensity, waveform width, area, skewness, kurtosis, and leading edge rise time. The spatial variability in these properties were decomposed into orthogonal eigenvectors using standard principle component analysis. The spatial weighting of the first principal component (representing 95% of the variance) was compared to observed surficial mud fraction. A simple logarithmic curve fit to the data accounted for 41% of the variability and well estimated (13% RMS error) the spatial pattern of mud across the bay from deep channels (no mud) to the flats (high mud content). The calibrated logarithmic function is used to estimate mud fraction spanning the estuary. Systematic deviations from the model are associated with regions with lower sediment porosity. When these anomalous data are removed from the analysis, the logarithmic model accounts for 62% of the variance. Application of the model along two cross-estuary transects in the Great Bay (independent from model development) resulted in similar RMS errors (15%) in predicted mud fraction showing that the empirical model works well for the Great Bay region provided the same sonar and settings are used.
Ocean Acidification (OA) is a complex problem in coastal waters, affecting a variety of stakeholder groups (commercial, environmental, governmental) across a wide range of spatial and temporal scales. Assessing and projecting OA impacts is difficult given the contributions of several processes, a lack of recent historical baseline data in many areas, and the dynamic nature of the coastal environment. Alkalinity is the ocean's primary buffer against climate-driven acidification. While the alkalinity of the ocean has long been studied, the variability of alkalinity in the coastal zone and the processes affecting alkalinity have received less attention. However, new technological advancements coupled with improved understanding of the chemistry of alkaline species may offer new insights into buffering against OA. Researchers in the UNH Ocean Process Analysis Laboratory are currently conducting two projects examining coastal alkalinity across a variety of settings. This presentation will discuss the state of knowledge regarding coastal alkalinity, outline the approach of each OPAL project, present new data and maps, and synthesize how these projects will advance our understanding of coastal alkalinity and acidification.
Quantifying the coupled physical and geochemical processes in the fluid-sediment interface is critical to managing coastal resources. This is of particular importance during times of enhanced hydrodynamic forcing where extreme tide or wind events can have a significant impact on water quality. A combination of field and laboratory experiments were used to examine the relationship between large-scale fluid shear stresses and geochemical fluxes at the fluid-sediment interface in the Great Bay Estuary, New Hampshire. Sediment geochemical measurements paired with flow field observations over several tidal cycles provide nutrient load estimates for the Bay. Sampling during typical tidal flow conditions along estuary-wide transects, an unexpected rotational flow field in the near-bed region of the water column was observed, which could have significant impact on the resultant nutrient release and nutrient budget estimates.
Effects of the biomedical bleeding process on the behavior and physiology of the American horseshoe crab, Limulus polyphemus.
The hemolymph from the American horseshoe crab, Limulus polyphemus, is used to produce Limulus Amebocyte Lysate (LAL), which is used to test medical devices and vaccines for Gram-negative bacteria. This process has a 10-30% mortality rate, as well as several sublethal impacts. The goals of this study were to: 1) investigate the effects of the bleeding procedure on the behavior of horseshoe crabs in their natural environment and; 2) determine which bleeding process stressors (blood loss, air exposure, or increased temperature) have the most deleterious effects. For the field study, 14 control and 14 bled animals were fitted with ultrasonic transmitters and released into the Great Bay Estuary, and their depth preferences and locomotor activity were recorded from May-December of 2016. Lab experiments were conducted in outdoor tanks where animals were exposed to combinations of stressors. Accelerometers were attached to 64 animals to measure activity; and blood samples were repeatedly drawn to monitor hemocyanin levels. The telemetry study showed that control and bled animals exhibited similar activity patterns and seasonal migrations with females being slightly more impacted by the bleeding process in the first few weeks after they were released. In the lab, hemocyanin concentrations and activity were significantly impacted by different combinations of stressors, but not individual stressors. We hope that when this study is completed, the findings can be utilized to more sustainably bleed horseshoe crabs.
Despite increasing calls to connect science with decision-makers, challenges remain in facilitating the flow of information across sectors. In some cases, these challenges stem from lack of resources or other capacity limitations, in others from a fundamental lack for awareness of what information is most needed by decision makers and how information flows between groups. In this study, we focus on the information needs and sources as reported by business and government decision makers in coastal New England. Through analysis of semi-structured interviews, we focus on what types of information needs are identified and what sources of information business and government decision-makers rely on for their jobs. Within these sectors, we also explore 1) the timescale of the information needs as context for understanding how the different sectors conceptualize the challenges they face, and 2) the systems scale as context for understanding conceptualization of the system within which they operate. If we are to meet the calls for management relevant science and science based decision-making, understanding these factors of information flow will be a key component.
Henricia sanguinolenta is a native generalist predator that consumes sponges during the fall and spring months. Historically, in the summer and the fall months, these animals feed on detritus and filter particles from the water column. However, after the invasion of several tunicate species, these animals had the opportunity to feed on another prey species during the warmer months when food is less abundant. The goals of this study were to 1) monitor the percent cover of prey species throughout the year 2) determine sea star feeding patterns, and 3) evaluate the effect of diet on growth and reproduction. A field site was surveyed monthly to evaluate the percent cover of tunicate species, and instances of feeding were recorded. In a lab setting, sea stars were fed four different diets for six months. They were fed a combination of sponge and tunicate species that represented the historical and proposed current diet. They were weighed every two weeks, and at the end of the experiment the gonads and pyloric caeca were weighed.
An estimated 1400 gigatons of methane are held in subsea reservoirs on the shallow (<50 m average depth) Eastern Siberian Arctic Shelf (ESAS). Marine gas seeps and high methane concentrations in surface waters indicate these reservoirs are releasing methane via ebullition. Bubbles ebullated from the ESAS seafloor have a relatively short pathway through the water column and can facilitate the transport of methane directly to the atmosphere without oxidation. Methane seeps were mapped with a calibrated broadband split-beam echosounder on the ESAS in order to directly and quantitatively address the magnitude of methane flux and the fate of rising bubbles. Acoustic measurements were made over a broad range of frequencies (16 to 29 kHz), which allowed for very high range resolution and the identification of single bubbles in the water column. Seep bubble size distribution (BSD) were determined by exploiting bubble target strength models over the broad range of frequencies. By coupling BSD with bubble rise velocity measurements, made possible by split-beam target tracking, gas flux can be estimated.
This study applied organizational change management theories and principles to understand the appetite and attitudes of fishermen to change, including the Paradox of Fishermen. It also evaluated the efficacy of industry groups that serve to facilitate change on behalf of fishermen against the renowned Kotter model for organizational change, and it developed a new, comprehensive change management model to facilitate change in the New England groundfish fishery.
A tidal energy conversion system was designed to power an array of smart infrastructure and estuarine sensors on Portsmouth, NH’s Memorial Bridge. The purpose of this tidal energy conversion system is to demonstrate an emerging renewable energy technology, serve as a research tool, and increase public interest in S.T.E.M. as well as the United States’ critical energy and transportation infrastructure. The tidal energy conversion system consists of a crossflow hydrokinetic turbine, a floating turbine deployment platform, and two vertical guideposts that provide a mooring point between the turbine deployment platform and one of the bridge’s piers. A resource assessment was performed to determine the available energy that could be converted from the tidal currents at the deployment site. An energy management system was simulated to determine the potential for providing continuous power to the sensors. Expected loads were calculated to ensure that the tidal energy conversion system would perform as expected under local gravitational, wind, wave, and tidal current loading. As a part of a senior design project, a 1:13 Froude scaled model of the tidal energy conversion system and bridge pier was constructed and tested in a tow/wave tank to experimentally verify these loads.
Article 76 of the United Nations Convention on the Law of the Sea provides a mechanism by which a coastal State can extend sovereign rights over resources of the seafloor and subsurface outside of its 200 nautical mile exclusive economic zone. In order for a coastal State to delineate this region, often referred to as the extended continental shelf (ECS), bathymetric, geophysical and geological data must be collected and analyzed to apply the mandates defined within Article 76. The coastal State must present its ECS delineation to a commission, called the Commission on the Limits of the Continental Shelf (CLCS). The CLCS reviews coastal States’ submissions and publishes recommendations as to whether they believe that the proposed ECS boundary is in accordance with Article 76. The United States has a potential ECS in the Chukchi Borderland region north of Alaska. This thesis examined two coastal States’ CLCS recommendations, the Kerguelen Plateau (Australia) and Vøring margin (Norway), to assess what criteria the CLCS utilized to classify seafloor highs, to forecast the impact these recommendations may have on a potential submission of the United States in the Chukchi Borderland region. This thesis has found that the CLCS requires a coastal State with seafloor highs that are connected to its continental margin to show that these features are (or not) morphologically and geologically continuous with the continental margin and landmass. If the coastal State can prove the seafloor high under question satisfies both of these criteria, it could potentially increase the coastal State’s final ECS outer boundary. Application of these criteria to the Chukchi Borderland region found that available data today could substantiate an argument that the Chukchi Borderland fulfills both criteria; however, further geological data needs to be collected from the northern extension of the Chukchi Borderland to support an Article 76 seafloor high classification.
Offshore wind proposal and installment is growing at a fantastic rate. In these necessarily large wind farms located near densely populated coastal cities, the governing fluid dynamics is not completely understood. An experimental study of a large offshore wind farm array is being conducted at the UNH Flow Physics Facility to better understand the flow around these devices.
Observations of wave orbital ripples and current driven mega-ripples at two cross shore locations within the sub-tidal area of a mega-nourishment were made as part of the MEGA-Perturbation EXperiment (MEGAPEX). MEGAPEX was an internationally collaborative field experiment that took place in the fall of 2014 at the Sand Engine mega-coastal nourishment in the Netherlands. Installed in 2011, the purpose of the 4.5 km alongshore and 700 m cross shore perturbation is to use currents to naturally nourish the southern Dutch coast for a period of 20 years. Over the past 4 years the Sand Engine has dramatically changed shape as seen in Fig. 1a (initial shape in 2011) and Fig. 1b (shape today) (Stive, et al. 2013). On the large scale, the mega-nourishment is very dynamic; raising the question of the dynamic nature of its small scale morphology. This research investigates the forcing mechanisms behind small scale temporal and spatial morphologic change of ripples at the tip of the Sand Engine. Morphologic patterns were observed with two stationary rotating pencil beam sonars with a 3 m diameter footprint positioned with a 100 m cross shore spacing, just seaward of the shoreline and just shoreward of the sub-tidal sandbar. Concomitant hydrodynamic forcing was measured using an array of ADVs and ADCPs. Measurements were collected over a month long period, capturing two significant coastal storms, one of which was the remnants of Hurricane Gonzolo. Two-dimensional spectral analysis determined ripple orientation, wave length, and height (Fig. 1c and 1d). Results show ripples changing orientation and regime between orbital and anorbital bed states as a function of hydrodynamic forcing, a rarely observed phenomenon in previous works. Ripple wave length varied between 14 cm and 1.2 m (Fig. 1c and 1d) dependent upon the phase of the tide, sometimes complete transformation took place within as little as 20 minutes. Finally, during the passing of the remnants of Hurricane Gonzolo, with a 5 m offshore wave height, ripple wave lengths of 2.5 m were observed within this relatively shallow nearshore area.

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