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All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The relation of gravity waves and turbulence in the mesosphere

Since researchers couldn't prove that the mesospheric turbulence layers are generated by the simultaneously existing short-period gravity waves, they invoked other generation mechanisms than wave breaking. Possible mechanisms like lateral convection (Rottger 1980a), quasi-geostrophic flows at mesoscales (Lilly, 1983) or vortical modes of motion as seen in the ocean (Muller and Pujalet, 1984) could be candidates. Researchers are inclined to see a connection of these layers or laminae with very-long-period internal waves because of the periodicity in their vertical structure and their long mean persistency. Rottger (1980b) had proposed that such structures are due the modulation of the me an temperature and wind profiles by internal waves. The superposition of random or short-term wave-induced wind and temperature fluctuations with the background profile, modulated by very-long-period waves (quasi-inertia waves) then would yield the observed effects, and could explain the vertical periodicity, the long-term mean persistency as well as some short-term variability of their intensity.

Rottger, J.↗
NASA NTRS1989

Solitonlike solutions in loop current eddies

The application of the nonlinear quasi-geostrophic equations to an isolated eddy in the western continental slope region in the Gulf of Mexico is examined for a two-layer ocean model with bottom topography. In the linear limit, solutions are topographic nondispersive waves. Form-preserving solutions, or solitons, have been found. The solution is shown to be a limiting form for a nonlinear dispersive system propagating northward along the topographic waveguide in the western continental slope region in the Gulf of Mexico. Using satellite-tracked drifter data, a linear relationship is found between the amplitude of the deduced stream function of the eddy and its observed translational velocity over the continental slope, which supports the hypothesis that some mesoscale eddies interacting with the continental slope behave as solitons.

Nakamoto, Shoichiro↗
NASA NTRS1991

Marine research using data from TOPEX/Poseidon

The Proudman Oceanographic Laboratory (POL), the Institute of Oceanographic Sciences Deacon Laboratory (IOSDL), and the British National Space Centre (BNSC) plan to use radar altimeter data from the TOPEX/POSEIDON mission in five main areas of research. These are: (1) investigation of variations in Southern Ocean sea levels and circulation; (2) related numerical modeling and data assimilation; (3) global and regional ocean tides; (4) North Sea and northeast Atlantic studies; and (5) winds and waves. Each one of these topics is described briefly below while more information can be extracted from the United Kingdom response to the TOPEX/POSEIDON Announcement of Opportunity.

Woodworth, Philip L.↗
NASA NTRS1997

Simultaneous Measurements of Water Vapor Profiles From Airborne MIR and LASE

A NASA ER-2 aircraft flight with both Millimeter-wave Imaging radiometer (MIR) and lidar Atmospheric Sensing Experiment (LASE) was made over ocean areas in the eastern United States on September 25, 1995. The water vapor profiles derived from both instruments under both clear and cloudy conditions are compared in this paper. It is shown that good agreement is found between the MIR-derived and the LASE-measured water vapor profiles over the areas of clear-sky condition. In the cloudy areas, the MIR-retrieved values at the altitudes of the cloud layers and below are generally higher than those measured by the LASE.

Wang, J. R.↗
NASA NTRS2003

Possible Stick-Slip Mechanism for Whillans Ice Stream

Tidally-induced stick-slip motion in the mouth of Whillans Ice Stream provides a unique natural experiment in ice-stream response behavior and fiom which we might learn a great deal about subglacial till properties and sub-ice-stream conditions. At the IGS Symposium on Fast Glacier Flow (Yakutat, 2002), we reported our observations of stick- slip motion and demonstrated its synchronicity with tidal forcing. Recently, we have completed additional processing of our GPS data in differential mode. It reveals more details of the stick-slip events and illustrates that within 30 seconds, the temporal interval of our data, the ice stream accelerates to a speed corresponding to a completely lubricated bed. While details of individual events vary, there seems to be strong evidence of an elastic rebound on the time scale of one hour following most events. This suggests the event involves the release of stored elastic strain energy in the ice. The similar displacements of events suggest further that till or subglacial hydrologic properties limit the amount of elastic strain released in any single event. We follow a line of reasoning that dilatant strengthening limits the slip displacement and present model of the stick-slip process. To match the observed delay between the peak ocean tide and stick-slip events, our model includes a propagating pressure wave in the subglacial hydrologic system between the grounding line, where the rising tide first increases the subglacial water pressure and regions upstream where stored elastic strain increases the basal shear stress. This high-tide event is released when the increased water pressure reaches the region of increased shear stress. Dilatant strengthening stops the event by increasing pore volume and lowering the water pressure. Following this event, falling tide increases the normal forces, compresses the till and increases pore pressure again, leading to the second falling-tide event we observe every tidal cycle.

Bindschadler, Robert↗
NASA NTRS2003

Possible Stick-Slip Mechanism for Whillans Ice Stream

Tidally-induced stick-slip motion in the mouth of Whillans Ice Stream provides a unique natural experiment in ice-stream response behavior and from which we might learn a great deal about subglacial till properties and sub-ice-stream conditions. At the IGS Symposium on Fast Glacier Flow (Yakutat, 2002), we reported our observations of stick- slip motion and demonstrated its synchronicity with tidal forcing. Recently, we have completed additional processing of our GPS data in differential mode. It reveals more details of the stick-slip events and illustrates that within 30 seconds, the temporal interval of our data, the ice stream accelerates to a speed corresponding to a completely lubricated bed. While details of individual events vary, there seems to be strong evidence of an elastic rebound on the time scale of one hour following most events. This suggests the event involves the release of stored elastic strain energy in the ice. The similar displacements of events suggest further that till or subglacial hydrologic properties limit the amount of elastic strain released in any single event. We follow a line of reasoning that dilatant strengthening limits the slip displacement and present model of the stick-slip process. To match the observed delay between the peak ocean tide and stick-slip events, our model includes a propagating pressure wave in the subglacial hydrologic system between the grounding line, where the rising tide first increases the subglacial water pressure and regions upstream where stored elastic strain increases the basal shear stress. This high-tide event is released when the increased water pressure reaches the region of increased shear stress. Dilatant strengthening stops the event by increasing pore volume and lowering the water pressure. Following this event, falling tide increases the normal forces, compresses the till and increases pore pressure again, leading to the second falling-tide event we observe every tidal cycle.

Bindschadler, Robert↗
DOE OSTI2022

Mechanisms behind the Springtime North Pacific ENSO Teleconnection Bias in Climate Models

Previous studies have shown that models overestimate the strength of ENSO teleconnections to the North Pacific during springtime, but the underlying reasons for this bias remain unknown. Here, in this work, the relative contributions from basic-state and thermodynamic/dynamic forcing factors are disentangled through idealized experiments with the Community Earth System Model and a range of stationary wave modeling experiments. It is revealed that in CESM1 the diabatic heating biases over the tropical Indian Ocean and tropical central-western Pacific jointly favor a cyclonic (anticyclonic) circulation bias to occur in the North Pacific during the springtime of El Niño (La Niña) events. On one hand, the difference in the modeled and observed climatological basic state does not lead to the bias formation directly, as the diabatic heating biases are the primary cause. On the other hand, the springtime basic state is conducive to a more vigorous stationary wave response to the biased diabatic heating than the wintertime state, and this explains why the teleconnection bias occurs during springtime but not in winter. An iterative bias-correction approach is then implemented in the atmospheric model component of CESM1 to verify the linkage between the tropical diabatic heating bias and the teleconnection bias. Moreover, this explanation is shown to be relevant in other models of phase 5 of the Coupled Model Intercomparison Project (CMIP5) as a strong relationship is found between biases in ENSO-related tropical central-western Pacific/Indian Ocean precipitation and North Pacific circulation across models in spring.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Enabling Power at Sea: Opportunities for Expanded Ocean Observations through Marine Renewable Energy Integration

The blue economy is a dynamic and rapidly growing movement that captures the interplay between economic, social, and ecological sustainability of the ocean and encompasses numerous maritime sectors and activities (e.g., commerce and trade; living resources; renewable energy; minerals, materials, and freshwater; and ocean health and data). The demand for ocean data to inform scientific, risk reduction, and national security needs is leading to a large increase in the number of deployed ocean observation and monitoring systems, most of which require increased power. Because ocean observation systems are often placed in remote locations, they primarily rely on energy storage (or in some cases in situ energy generation) to power instruments and equipment, which imposes limits on sampling rates, deployment times, and spatiotemporal resolution of data. The U.S. Department of Energy Water Power Technologies Office is exploring the potential for marine renewable energy (MRE) devices (largely wave and tidal energy converters) to provide power to support multiple blue economy opportunities. A portion of these opportunities focus on power at sea markets for providing power in off-grid and offshore locations to support a variety of ocean-based activities, including ocean observation and navigation, underwater vehicle charging, marine aquaculture, marine algae farming, and seawater mining. Initially, research has focused on better understanding how and where MRE can provide a consistent source of reliable power to extend ocean observing missions, including operation of autonomous underwater vehicles. Online surveys as well as phone and in-person interviews were conducted with experts in the field of ocean observing systems and observatories to gather end-user requirements, determine energy needs, identify opportunities for codevelopment, and pinpoint constraints for MRE to meet those needs. The surveys and interviews provided feedback on the potential for powering devices and vehicles using MRE, including identifying common themes and challenges that will inform foundational research and development steps needed to advance the integration of MRE with ocean observing systems. In most cases, additional power generation on the order of watts was identified as significantly beneficial to enhancing ocean observations capabilities.

16 TIDAL AND WAVE POWER↗
NASA NTRS1986

Variation of the drag coefficient and its dependence on sea state

Using a Gill propeller vane anemometer and resistance wave wires over a water column depth of 15 m, simultaneous measurements of the momentum flux and sea surface wave spectra were acquired from the Pisa mast, 28 km offshore in the German Bight during autumn and winter 1979. These data were analyzed to identify the relationship between wind stress and surface waves. It was found that wind stresses for wind speeds above 15 m/s were regularly higher than open ocean wind stresses as reported by Smith (1980) and by Large and Pond (1981) for the same mean wind speed. These results, when described in terms of the drag coefficient, compared closely with the results of Sheppard et al. (1972), who collected surface layer statistics over Lough Neagh, Northern Ireland. After modeling the surface waves of the North Sea as a function of wave saturation (or wave age), it became evident that variations in the magnitude of the drag coefficient could be explained by coincident variations in the surface wave energy spectrum. By applying the wave dependent roughness length model described by Kitaigorodskii (1973), the North Sea drag coefficient was predicted to be larger than drag coefficients reported from the open sea.

Geernaert, G. L.↗
NASA NTRS1991

Seasonal cloud-radiative forcing over land and ocean derived from ERBE satellites

Earth Radiation Budget Experiment (ERBE) data are analyzed to determine seasonal variations of radiative parameters. Particular attention is given to annual variations of the top-of-the atmosphere zonally averaged outgoing long-wave (LW) and absorbed short-wave (SW) flux, as well as the short- and long-wave components of cloud-radiative forcing. The ERBE results reveal significant seasonal variations in both outgoing LW and absorbed SW flux, and a pronounced difference between oceanic and continental surfaces.

Harrison, Edwin F.↗
DOE OSTI2021

Biofouling Analysis for Wave Energy Piston Design: CRADA 542 [Abstract only]

Triton System’s Wave Energy Converter (WEC) uses an oscillating water column approach to provide small scale power to ocean observing and navigational buoys. Biofouling and corrosion are a major concern for all ocean-deployed components, especially when mechanical motion is involved. Triton Systems will collaborate with PNNL to evaluate seals, materials, and component performance in a controlled biofouling test environment. Results from this testing will be used to improve seal design and material selection, mitigating risk of premature failure during open water testing and evaluation.

16 TIDAL AND WAVE POWER↗
NASA NTRS2014

Sea Ice Concentration and Extent

Among the most seasonal and most dynamic parameters on the surface of the Earth is sea ice which at any one time covers about 3-6% of the planet. In the Northern Hemisphere, sea ice grows in extent from about 6 x 10(exp 6) sq km to 16 x 10(exp 6) sq km, while in the Southern Hemisphere, it grows from about 3 x 10(exp 6) sq km to about 19 x 10(exp 6) sq km (Comiso, 2010; Gloersen et al., 1992). Sea ice is up to about 2-3 m thick in the Northern Hemisphere and about 1 m thick in the Southern Hemisphere (Wadhams, 2002), and compared to the average ocean depth of about 3 km, it is a relatively thin, fragile sheet that can break due to waves and winds or melt due to upwelling of warm water. Being constantly advected by winds, waves, and currents, sea ice is very dynamic and usually follows the directions of the many gyres in the polar regions. Despite its vast expanse, the sea ice cover was previously left largely unstudied and it was only in recent years that we have understood its true impact and significance as related to the Earths climate, the oceans, and marine life.

sea ice extent↗
NASA NTRS1990

Tropical Pacific moisture variability

The objectives are to describe synoptic scale variability of moisture over the tropical Pacific Ocean and the systems leading to this variability; implement satellite analysis procedures in support of this effort, and to incorporate additional satellite information into operational analysis forecast systems at the National Meteorological Center (NMC). Composite satellite radiance patterns describe features detectable well before the development of synoptic scale tropical plumes. These typical features were extracted from historical files of Tiros Operational Vertical Sounder (TOVS) radiance observations for a pair of tropical plumes which developed during January 1989. Signals were inserted into the NMC operational medium range forecast model and a suite of model integrations were conducted. Many of the 48 h model errors of the historical forecasts were eliminated by the inclusion of more complete satellite observations. Three studies in satellite radiance analysis progressed. An analysis which blended TOVS moisture channels, OLR observations and European Center for Medium Weather Forecasts (ECMWF) model analysis to generate fields of total precipitable water comparable to those estimated from Scanning Multichannel Microwave Radiometer (SMMR) mu-wave observations. This study demonstrated that a 10 y climatology of precipitable water over the oceans is feasible, using available infrared observations (OLR and TOVS) and model analysis (ECMWF, NMC or similar quality). The estimates are sensitive to model quality and the estimating model must be updated with operational model changes. Coe developed a set of tropical plume and ITCZ composites from TOVS observations, and from NMC and ECMWF analyses which had been passed through a radiative transfer model to simulate TOVS radiances. The composites have been completed as well as many statistical diagnostics of individual TOVS channels. Analysis of the computations is commencing. Chung has initiated a study of the differences between TOVS observed vapor structure during El Nino Southern Oscillation (ENSO) (1983) and non-ENSO (1984) years. Preliminary diagnosis demonstrates gross moisture changes between warm and cold sea surface temperature episodes.

Mcguirk, James P.↗
DOE OSTI2020

Power at Sea: Use of Wave Energy Converters for Powering Offshore Oil and Gas Operations

New innovative services and goods based on artificial intelligence, next-generation robotics, autonomy, digitization, and electrification are taking root in the ocean economy. More typical competitive forces, such as value enhancement and safety improvement, are also present, as suppliers constantly strive to improve their competitive positioning. Concurrently, the Oil and Gas sector is experiencing mounting pressure to decrease its operational carbon emissions, forcing efforts to reduce or eliminate liquid fuel consumption offshore. Companies in the ocean economy are having to react to this combination of macro- and micro-level drivers and innovate at an ever more rapid pace. However, before many of these new capabilities can be implemented, new, clean, reliable power sources are needed, especially as liquid fuel grows increasingly out of favor. For many of these loads—both old and new and ranging from watts to megawatts—wave energy systems provide the best solution for remote power generation. As such, research, development and demonstration activities are underway to prove wave energy's ability to provide reliable, consistent energy supplies for certain offshore Oil and Gas activities, paving the way for near term commercialization. Furthermore, this paper outlines these drivers, competitive reaction to them, and why and how wave energy can be a preferable choice for power at sea.

16 TIDAL AND WAVE POWER↗
DOE OSTI2021

Evidence for Coupling Between the Subseasonal Oscillations in the Southern Hemisphere Midlatitude Ocean and Atmosphere

Abstract A regional perspective is taken to investigate the intriguing ∼25‐day periodicity in the Southern Hemisphere (SH) baroclinic annular mode (BAM) and the possible underlying mechanisms. Results show that the 25‐day periodicity exists not only in the zonal average but also in the regional average of eddy activity as long as the domain of the average is wide enough to accommodate a wave packet. The favorable domain for the ∼25 days periodicity is located downstream of the largest baroclinicity in midlatitudes. The wave activity developed there can travel circumglobally several times with a typical group velocity of 25 m s −1 , and reenter the domain every 12.5 days, setting the base periodicity. A slower oceanic oscillation at a time scale of ∼100 days in the same region appears to select and reinforce the multiples of 12.5 days, giving rise to a pronounced ∼25‐day periodicity in the wave activity.

Xue, Daokai↗
DOE OSTI2024

Prototyping of a Rotary Triboelectric Nanogenerator for Power at Sea

Increasing at-sea power generation by Triboelectric Nanogenerator (TENG) energy harvesters towards the order of 1-Watt will create significant opportunities to power ocean observation buoys and distributed sensor nodes by extending mission time and increasing sensor payload. Of the many possible configurations of harvesting wave energy with TENGs, we document the rationale for choosing and developing a rotary TENG that operates by the freestanding mode. The rotary TENG prototype consists of two plates, a rotor and a stator, to take advantage of the various mechanisms of converting wave action into rotational motion. We have constructed a testing apparatus that allows us to vary several key parameters of the device: distance between rotor and stator, triboelectric material, rotational speed, number of electrodes and output load impedance. Preliminary results show that when driven at a constant 500 rpm, we can achieve a power density of 0.7 W/m3. A variable speed motor drives the rotor, which can be driven using a velocity profile informed by the equivalent to the output from a wave energy converter (WEC). The optimized rotational TENG can be stacked and driven by a single shaft, increasing the energy density of the device. The output of such a TENG could be used to power devices in the ocean at a low cost and high durability.

electrostatic generator↗
DOE OSTI2023

Review of TEAMER Awards for WEC-Sim Support: Preprint

Testing Expertise and Access for Marine Energy Research (TEAMER) is a U.S. Department of Energy Water Power Technologies Office sponsored program, overseen by the Pacific Ocean Energy Trust, which aims to advance the state of marine energy technologies. The program connects technology developers with experts at U.S. facilities, including numerical modeling and analysis facilities, like WEC-Sim. The WEC-Sim facility is supported by the WEC-Sim development team at Sandia National Laboratories and the National Renewable Energy Laboratory. WEC-Sim (Wave Energy Converter SIMulator) is an open-source software for simulating wave energy converters. WEC-Sim can model the multi-body dynamics of devices comprised of bodies, joints, power take-off systems, and mooring systems. Since TEAMER's first round of support in 2020, there have been eighteen TEAMER awards focused on numerical model development in WEC-Sim. TEAMER awards for WEC-Sim support have modeled a wide range of wave energy converter archetypes, including point absorbers, attenuators, oscillating water columns, and many other novel architectures. A wide variety of studies have been conducted, leading to important insights for TEAMER partners and software improvements for WECSim. This article highlights several successful WEC-Sim TEAMER awards. The awards described herein include TEAMER recipients Ocean Motion Technologies, AquaHarmonics, iProTech, East Carolina University, Virginia Tech, Maiden Wave Energy, and the University of Massachusetts Dartmouth. The awards of these seven partners contain a wide range of investigations and cover the creation of baseline hydrodynamic models, PTO modeling, geometry optimization in both boundary element methods and WECSim, and model tuning and validation.

industry support↗
DOE OSTI2024

Migration and accumulation of hydrous mantle incipient melt in the Earth's asthenosphere: Constraints from in-situ falling sphere viscometry measurements

The Earth's oceanic lithosphere-asthenosphere boundary (LAB) is marked by a notable decrease in seismic wave velocities and an increase in attenuation. This phenomenon is likely attributed to the accumulation of partial melt at the top of the asthenosphere. Nevertheless, the process involving the upward migration and aggregation of low-degree partial melts, highly likely to be mantle incipient melts in the asthenosphere, remains underexplored. Viscosity is a key factor controlling the flow of melts, thus in this study, we used In-situ X-ray falling sphere viscometry experiments to determine the viscosity of the mantle incipient melt containing 1.8–4.0 wt.% water at 1.5–6 GPa and 2100 K. We found that water and pressure can effectively decrease the viscosity of the mantle incipient melt. Therefore, the mantle incipient melts are highly mobile with a high segregation velocity in the deeper part of the asthenosphere. However, during ascent, their mobility diminishes due to an increase in viscosity and a decrease in water content. In conclusion, these mechanisms potentially contribute to the accumulation of partial melt at the top of the asthenosphere.

58 GEOSCIENCES↗