Search

Studying ocean tides with satellite altimetry has traditionally been difficult in coastal regions. The 1 day repeat of the Cal/Val phase of SWOT provides a unique dataset that can be exploited for tidal analysis. In this work, KaRIn data from the SWOT Cal/Val phase are analyzed in two coastal regions to present a first look at the possibilities for tidal analysis from SWOT. The areas are: (a) Bristol Channel and (b) Great South Bay. When benchmarked against in situ measurements in these regions, substantial improvements over tide models, which typically report errors exceeding tens of centimeters and degrees, are seen. Specifically, the SWOT ocean-tide estimates exhibit amplitude discrepancies ranging from 1.75 to 3 cm and phase lag discrepancies between 1.75° and 2.75° when compared with in situ tide gauge data. These findings underscore the value of SWOT for tidal research in complex coastal regions.

Tidal flow of seawater across the Earth's magnetic field induces electric currents and magnetic fields within the ocean and solid Earth. The amplitude and phase of the induced fields depends on electrical properties of both the seawater and the solid Earth, thus can be used as a proxy to study seabed properties or potentially for monitoring long-term trends in the global ocean climatology. This paper presents new global oceanic tidal magnetic field models and their uncertainties for four tidal constituents, including M2, N2, O1 and for the first time Q1. Models are obtained through a robust least-squares analysis of magnetic field observations from the Swarm and CHAMP satellites using a specially designed data selection scheme. We compare the retrieved magnetic signals with several alternative models reported in the literature. Additionally, we validate them using a series of high-resolution global 3-D electromagnetic simulations and place constraints on the conductivity of sub-oceanic mantle for all tidal constituents, revealing an excellent agreement between all tidal constituents and the oceanic upper mantle structure.

Monthly gravity field recovery using data from the GRACE and GRACE Follow-On missions includes errors limiting the spatial and temporal resolution of the estimated gravity fields. The major error contributions, besides the noise of the accelerometer instruments, arise from temporal aliasing errors due to imperfections in the non-tidal atmospheric and oceanic de-aliasing models and ocean tide models. We derive uncertainty information for the eight major tidal constituents from five different ocean tide models and introduce it into the gravity field recovery process in terms of a constrained normal equation system while expanding the parameter space by additional tidal parameters to be adjusted. We prove the effectiveness of the ocean tide variance-covariance information through realistic simulations and we assess its potential based on microwave and laser interferometer observations from the GRACE Follow-On mission. We show that errors are reduced by more than 20% ocean wRMS for a Gaussian filter radius of 300 km if uncertainty information for ocean tides is considered and stochastic modeling of instrument errors is applied, compared to the latest GFZ release 6.1. Our results also show the limited visibility of the effectiveness of the ocean tide variance-covariance information due to the dominating error contribution of non-tidal atmospheric and oceanic mass variations. Additionally, we investigate the option of estimating ocean tide parameters over a 1-year period while including ocean tide uncertainty information in order to improve ocean tide background modeling.

With the availability of more than 9 years of Cryosat-2, it is possible to revisit polar ocean tides, which have traditionally been difficult to determine from satellite altimetry. The SAMOSA+ physical retracker is a stable retracker developed particularly for Cryosat-2. Being a physical retracker, it enables the determination of the sea state bias. Correcting for the sea state bias enables more reliable sea level estimates compared with traditional empirical retrackers used before. Cryosat-2 data have been analyzed for residual ocean tides to the FES2014 ocean tide model in the Arctic Ocean and Antarctic Ocean using the response formalism. We utilize data from the sub-cycle of Cryosat-2, which follows a repeating pattern of approximately 28.33 days. This sub-repeat period makes it an advantageous alias period for the majority of significant constituents. This allowed for the estimation and mapping of the major tidal constituents in the open ocean and also in floating ice shelves from data extracted from leads in the sea ice. A novel empirical ocean tide model designed specifically for the polar region, DTU22, is introduced. Our findings reveal substantial enhancements in semi-diurnal tides within the Arctic Ocean and improvement in diurnal constituents within the Southern Ocean. In the Southern Ocean, the diurnal constituents are particularly improved using the empirical model by more than a factor of two to around 3 cm for both constituents compared with FES2014b. These outcomes underscore the significance of incorporating the reprocessed and retracted Cryosat-2 data into tidal modeling, highlighting its pivotal role in advancing the field.

With the continued rise in global mean sea level, operational predictions of tidal height and total water levels have become crucial for accurate estimations and understanding of sea level processes. The Dutch Continental Shelf Model in Delft3D Flexible Mesh (DCSM-FM) is developed at Deltares to operationally estimate the total water levels to help trigger early warning systems to mitigate against these extreme events. In this study, a regional version of the Empirical Ocean Tide model for the Northwest European Continental Sea (EOT-NECS) is developed with the aim to apply better tidal forcing along the boundary of the regional DCSM-FM. EOT-NECS is developed at DGFI-TUM by using 30 years of multi-mission along-track satellite altimetry to derive tidal constituents which are estimated both empirically and semi-empirically. Compared to the global model, EOT20, EOT-NECS showed a reduction in the root-square-sum error for the eight major tidal constituents of 0.68 cm compared to in situ tide gauges. When applying constituents from EOT-NECS at the boundaries of DCSM-FM, an overall improvement of 0.29 cm was seen in the root-mean-square error of tidal height estimations made by DCSM-FM, with some regions exceeding a 1 cm improvement. Furthermore, of the fourteen constituents tested, eleven showed a reduction of RMS when included at the boundary of DCSM-FM from EOT-NECS. The results demonstrate the importance of using the appropriate tide model(s) as boundary forcings, and in this study, the use of EOT-NECS has a positive impact on the total water level estimations made in the northwest European continental seas., Mathematical Physics

© The Author(s), [year]. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Barreyre, T., Parnell‐Turner, R., Wu, J., & Fornari, D. Tracking crustal permeability and hydrothermal response during seafloor eruptions at the East Pacific Rise, 9°50’N. Geophysical Research Letters, 49(3), (2022): e2021GL095459, https://doi.org/10.1029/2021gl095459., Permeability controls energy and matter fluxes in deep-sea hydrothermal systems fueling a 'deep biosphere' of microorganisms. Here, we indirectly measure changes in sub-seafloor crustal permeability, based on the tidal response of high-temperature hydrothermal vents at the East Pacific Rise 9°50’N preceding the last phase of volcanic eruptions during 2005–2006. Ten months before the last phase of the eruptions, permeability decreased, first rapidly, and then steadily as the stress built up, until hydrothermal flow stopped altogether ∼2 weeks prior to the January 2006 eruption phase. This trend was interrupted by abrupt permeability increases, attributable to dike injection during last phase of the eruptions, which released crustal stress, allowing hydrothermal flow to resume. These observations and models suggest that abrupt changes in crustal permeability caused by magmatic intrusion and volcanic eruption can control first-order hydrothermal circulation processes. This methodology has the potential to aid eruption forecasting along the global mid-ocean ridge network., This research is funded by National Science Foundation (NSF) grants to D. J. Fornari and T. Barreyre (OCE-1949485), and to R. Parnell-Turner (OCE-1948936). T. Barreyre was supported by the University of Bergen, Norway.

Permeability controls energy and matter fluxes in deep-sea hydrothermal systems fueling a 'deep biosphere' of microorganisms. Here, we indirectly measure changes in sub-seafloor crustal permeability, based on the tidal response of high-temperature hydrothermal vents at the East Pacific Rise 9°50’N preceding the last phase of volcanic eruptions during 2005–2006. Ten months before the last phase of the eruptions, permeability decreased, first rapidly, and then steadily as the stress built up, until hydrothermal flow stopped altogether ∼2 weeks prior to the January 2006 eruption phase. This trend was interrupted by abrupt permeability increases, attributable to dike injection during last phase of the eruptions, which released crustal stress, allowing hydrothermal flow to resume. These observations and models suggest that abrupt changes in crustal permeability caused by magmatic intrusion and volcanic eruption can control first-order hydrothermal circulation processes. This methodology has the potential to aid eruption forecasting along the global mid-ocean ridge network.

To mitigate temporal aliasing effects in monthly mean global gravity fields from the GRACE and GRACE-FO satellite tandem missions, both tidal and non-tidal background models describing high-frequency mass variability in atmosphere and oceans are needed. To quantify tides in the atmosphere, we exploit the higher spatial (31 km) and temporal (1 hr) resolution provided by the latest atmospheric ECMWF reanalysis, ERA5. The oceanic response to atmospheric tides is subsequently modeled with the general ocean circulation model MPIOM (in a recently revised TP10L40 configuration that includes the feedback of self-attraction and loading to the momentum equations and has an improved bathymetry around Antarctica) as well as the shallow water model TiME (employing a much higher spatial resolution and more elaborate tidal dissipation than MPIOM). Both ocean models consider jointly the effects of atmospheric pressure variations and surface wind stress. We present the characteristics of 16 waves beating at frequencies in the 1-6 cpd band and find that TiME typically outperforms the corresponding results from MPIOM and also FES2014b as measured from comparisons with tide gauge data. Moreover, we note improvements in GRACE-FO laser ranging interferometer range-acceleration pre-fit residuals when employing the ocean tide solutions from TiME, in particular, for the S-1 spectral line with most notable improvements around Australia, India, and the northern part of South America.

To mitigate temporal aliasing effects in monthly mean global gravity fields from the GRACE and GRACE-FO satellite tandem missions, both tidal and non-tidal background models describing high-frequency mass variability in atmosphere and oceans are needed. To quantify tides in the atmosphere, we exploit the higher spatial (31 km) and temporal (1 hr) resolution provided by the latest atmospheric ECMWF reanalysis, ERA5. The oceanic response to atmospheric tides is subsequently modeled with the general ocean circulation model MPIOM (in a recently revised TP10L40 configuration that includes the feedback of self-attraction and loading to the momentum equations and has an improved bathymetry around Antarctica) as well as the shallow water model TiME (employing a much higher spatial resolution and more elaborate tidal dissipation than MPIOM). Both ocean models consider jointly the effects of atmospheric pressure variations and surface wind stress. We present the characteristics of 16 waves beating at frequencies in the 1-6 cpd band and find that TiME typically outperforms the corresponding results from MPIOM and also FES2014b as measured from comparisons with tide gauge data. Moreover, we note improvements in GRACE-FO laser ranging interferometer range-acceleration pre-fit residuals when employing the ocean tide solutions from TiME, in particular, for the S-1 spectral line with most notable improvements around Australia, India, and the northern part of South America.

Tides and Earth-Moon system evolution are coupled over geological time. Tidal energy dissipation on Earth slows Earth's rotation rate, increases obliquity, lunar orbit semi-major axis and eccentricity, and decreases lunar inclination. Tidal and core-mantle boundary dissipation within the Moon decrease inclination, eccentricity and semi-major axis. Here we integrate the Earth-Moon system backwards for 4.5 Ga with orbital dynamics and explicit ocean tide models that are "high-level" (i.e., not idealized). To account for uncertain plate tectonic histories, we employ Monte Carlo simulations, with tidal energy dissipation rates (normalized relative to astronomical forcing parameters) randomly selected from ocean tide simulations with modern ocean basin geometry and with 55, 116, and 252 Ma reconstructed basin paleogeometries. The normalized dissipation rates depend upon basin geometry and Earth's rotation rate. Faster Earth rotation generally yields lower normalized dissipation rates. The Monte Carlo results provide a spread of possible early values for the Earth-Moon system parameters. Of consequence for ocean circulation and climate, absolute (un-normalized) ocean tidal energy dissipation rates on the early Earth may have exceeded today's rate due to a closer Moon. Prior to ∼3Ga , evolution of inclination and eccentricity is dominated by tidal and core-mantle boundary dissipation within the Moon, which yield high lunar orbit inclinations in the early Earth-Moon system. A drawback for our results is that the semi-major axis does not collapse to near-zero values at 4.5 Ga, as indicated by most lunar formation models. Additional processes, missing from our current efforts, are discussed as topics for future investigation.

Tides and Earth-Moon system evolution are coupled over geological time. Tidal energy dissipation on Earth slows Earth's rotation rate, increases obliquity, lunar orbit semi-major axis and eccentricity, and decreases lunar inclination. Tidal and core-mantle boundary dissipation within the Moon decrease inclination, eccentricity and semi-major axis. Here we integrate the Earth-Moon system backwards for 4.5 Ga with orbital dynamics and explicit ocean tide models that are "high-level" (i.e., not idealized). To account for uncertain plate tectonic histories, we employ Monte Carlo simulations, with tidal energy dissipation rates (normalized relative to astronomical forcing parameters) randomly selected from ocean tide simulations with modern ocean basin geometry and with 55, 116, and 252 Ma reconstructed basin paleogeometries. The normalized dissipation rates depend upon basin geometry and Earth's rotation rate. Faster Earth rotation generally yields lower normalized dissipation rates. The Monte Carlo results provide a spread of possible early values for the Earth-Moon system parameters. Of consequence for ocean circulation and climate, absolute (un-normalized) ocean tidal energy dissipation rates on the early Earth may have exceeded today's rate due to a closer Moon. Prior to ∼3Ga , evolution of inclination and eccentricity is dominated by tidal and core-mantle boundary dissipation within the Moon, which yield high lunar orbit inclinations in the early Earth-Moon system. A drawback for our results is that the semi-major axis does not collapse to near-zero values at 4.5 Ga, as indicated by most lunar formation models. Additional processes, missing from our current efforts, are discussed as topics for future investigation.

Ocean tides and winter surface storms are among the main factors driving the dynamics and spatial structure of marine coastal species, but the understanding of their impact on deep-sea and hydrothermal vent communities is still limited. Multidisciplinary deep-sea observatories offer an essential tool to study behavioural rhythms and interactions between hydrothermal community dynamics and environmental fluctuations. Here, we investigated whether species associated with a Ridgeia piscesae tubeworm vent assemblage respond to local ocean dynamics. By tracking variations in vent macrofaunal abundance at different temporal scales, we provide the first evidence that tides and winter surface storms influence the distribution patterns of mobile and non-symbiotic hydrothermal species (i.e. pycnogonids Sericosura sp. and Polynoidae polychaetes) at more than 2 km depth. Local ocean dynamics affected the mixing between hydrothermal fluid inputs and surrounding seawater, modifying the environmental conditions in vent habitats. We suggest that hydrothermal species respond to these habitat modifications by adjusting their behaviour to ensure optimal living conditions. This behaviour may reflect a specific adaptation of vent species to their highly variable habitat.

Ocean tides and winter surface storms are among the main factors driving the dynamics and spatial structure of marine coastal species, but the understanding of their impact on deep-sea and hydrothermal vent communities is still limited. Multidisciplinary deep-sea observatories offer an essential tool to study behavioural rhythms and interactions between hydrothermal community dynamics and environmental fluctuations. Here, we investigated whether species associated with a Ridgeia piscesae tubeworm vent assemblage respond to local ocean dynamics. By tracking variations in vent macrofaunal abundance at different temporal scales, we provide the first evidence that tides and winter surface storms influence the distribution patterns of mobile and non-symbiotic hydrothermal species (i.e. pycnogonids Sericosura sp. and Polynoidae polychaetes) at more than 2 km depth. Local ocean dynamics affected the mixing between hydrothermal fluid inputs and surrounding seawater, modifying the environmental conditions in vent habitats. We suggest that hydrothermal species respond to these habitat modifications by adjusting their behaviour to ensure optimal living conditions. This behaviour may reflect a specific adaptation of vent species to their highly variable habitat.

Ocean tides and winter surface storms are among the main factors driving the dynamics and spatial structure of marine coastal species, but the understanding of their impact on deep-sea and hydrothermal vent communities is still limited. Multidisciplinary deep-sea observatories offer an essential tool to study behavioural rhythms and interactions between hydrothermal community dynamics and environmental fluctuations. Here, we investigated whether species associated with a Ridgeia piscesae tubeworm vent assemblage respond to local ocean dynamics. By tracking variations in vent macrofaunal abundance at different temporal scales, we provide the first evidence that tides and winter surface storms influence the distribution patterns of mobile and non-symbiotic hydrothermal species (i.e. pycnogonids Sericosura sp. and Polynoidae polychaetes) at more than 2 km depth. Local ocean dynamics affected the mixing between hydrothermal fluid inputs and surrounding seawater, modifying the environmental conditions in vent habitats. We suggest that hydrothermal species respond to these habitat modifications by adjusting their behaviour to ensure optimal living conditions. This behaviour may reflect a specific adaptation of vent species to their highly variable habitat.

This Coastal and Hydraulics Engineering Technical Note (CHETN) reviews the development of a Regional Sediment Management (RSM) implementation strategy for Mobile Bay, AL. The objective of this strategy is to bring lessons learned through application of RSM and Engineering With Nature (EWN) principles and practices in the coastal environment to a broader perspective for sediment and related environmental management planning for Mobile Bay, specifically the placement within Mobile Bay of maintenance material dredged from the Mobile Harbor navigation channel. The Northern Gulf of Mexico (NGOM) RSM demonstration project concluded in 2003 (Rosati et al. 2001 [rev. 2004]). The U.S. Army Corps of Engineers (USACE), South Atlantic Division (SAD), Mobile District (SAM), continues to implement into District practice the RSM lessons learned from those NGOM studies. RSM is a systems-based approach for collaboratively addressing sediment-related issues within a regional context. RSM seeks to support sustainable solutions for more effective use of littoral, estuarine, and riverine sediment resources in an environmentally sensitive and economically efficient manner.

A global tuning experiment for the semidiurnal tide is performed with a barotropic model. The model is forced with the M2 equilibrium tide and accounts for the self-attraction and loading (SAL) term. In addition to a quadratic drag, various linear internal wave drag terms adjusted by a scale factor of O(1) are applied. The drag terms include the original Nycander (2005) tensor scheme, the Nycander tensor scheme reduced at supercritical slopes, and their scalar sisters, a Nycander scalar scheme computed for additional abyssal hill roughness, and the Jayne and St. Laurent (2001) scalar scheme. The Nycander scheme does not have a tunable parameter, but to obtain the best tidal solutions, it is demonstrated that some tuning is unavoidable. It is shown that the scalar Nycander schemes yield slightly lower root-mean square (RMS) elevation errors vs. the data-assimilative TPXO tide model than the tensor schemes. Although the simulation with the optimally tuned original Nycander scalar yields dissipation rates close to TPXO, the RMS error is among the highest. The RMS error is lowered for the reduced schemes, which place relatively more dissipation in deeper water. The inclusion of abyssal hill roughness improves the regional agreement with TPXO dissipation rates, without changing the RMS errors. It is difficult to have each ocean basin optimally tuned with the application of a constant scale factor. The relatively high RMS error in the Atlantic Ocean is reduced with a spatially varying scale factor with a larger value in the Atlantic. Our best global mean RMS error of 4.4 cm for areas deeper than 1000 m and equatorward of 66 is among the lowest obtained in a forward barotropic tide model., The original document contains color images. Published in Ocean Modelling, v85 p42-55, 2015. Prepared in collaboration with the University of Southern Mississippi, Stennis Space Center, MS, the University of Michigan, Ann Arbor, and Bangor University, Menai Bridge, Anglesey, UK. Sponsored in part by NRL N000173-06-2-C003.

The accuracy of state-of-the-art global barotropic tide models is assessed using bottom pressure data, coastal tide gauges, satellite altimetry, various geodetic data on Antarctic ice shelves, and independent tracked satellite orbit perturbations. Tide models under review include empirical, purely hydrodynamic (forward), and assimilative dynamical, i.e., constrained by observations. Ten dominant tidal constituents in the diurnal, semidiurnal, and quarter-diurnal bands are considered. Since the last major model comparison project in 1997, models have improved markedly, especially in shallow-water regions and also in the deep ocean. The root-sum-square differences between tide observations and the best models for eight major constituents are approximately 0.9, 5.0, and 6.5 cm for pelagic, shelf, and coastal conditions, respectively. Large intermodel discrepancies occur in high latitudes, but testing in those regions is impeded by the paucity of high-quality in situ tide records. Long-wavelength components of models tested by analyzing satellite laser ranging measurements suggest that several models are comparably accurate for use in precise orbit determination, but analyses of GRACE intersatellite ranging data show that all models are still imperfect on basin and subbasin scales, especially near Antarctica. For the M2 constituent, errors in purely hydrodynamic models are now almost comparable to the 1980-era Schwiderski empirical solution, indicating marked advancement in dynamical modeling. Assessing model accuracy using tidal currents remains problematic owing to uncertainties in in situ current meter estimates and the inability to isolate the barotropic mode. Velocity tests against both acoustic tomography and current meters do confirm that assimilative models perform better than purely hydrodynamic models., Published in Reviews of Geophysics, v52 p243-282, 2014. The original document contains color images.

Tidal forcing has been inserted into eddy-resolving global simulations of the HYbrid Coordinate Ocean Model (HYCOM). The tidal flows over realistic topography generate internal tides, i.e. internal waves at tidal frequencies. Similarly, geostrophic flows over rough topography generate internal lee waves. While it is not yet possible to resolve internal lee waves in global models, their impact can be parameterized. We have inserted parameterized topographic lee wave drag in global simulations that do not include tidal forcing., The original document contains color images. Published in Exchanges, v19 n2 p30-33, Jul 2014. Additional ONR grant N00014-11-1-0487. Sponsored in part by NRL N000173-06-2-C003.

The objective of the project was to develop an analysis framework and methodologies for evaluation of coastal military installation vulnerabilities and test them under prescribed scenarios of increased local mean sea level over the next century. Methodologies were developed to assess the potential scope and magnitude of impacts from physical effects of flooding, inundation, erosion, seawater intrusion, and alteration of tidal flows. Assessment methodologies targeted potential vulnerabilities of buildings, civil infrastructure, training areas, and waterfront and coastal structures. The project focused on conditions in the southwestern United States and utilized the key coastal military installations at Naval Base Coronado and Marine Corps Base Camp Pendleton to test the approach., Prepared in collaboration with the Terracosta Consulting Group, San Diego CA, the San Diego Supercomputer Center, University of California San Diego, the USGS San Diego Project Office, and Moffatt & Nichol-Blaylock, San Diego, CA.

A partnership of institutions (academia and government) is collaborating on inserting and validating barotropic and baroclinic tides in 1/12 deg and 1/25 deg numerical simulations of the global ocean. The collaboration is applying the results of the 1/12 deg and 1/25 deg simulations to a number of problems of scientific interest, described in further detail below. This partnership builds on the strong relationship that the lead PI of this proposal, Brian Arbic, has established since 2006 with Florida State University (FSU) and the Stennis Space Center branch of the Naval Research Laboratory (NRL) . NRL and FSU have a long-standing relationship, developed during the National Oceanographic Partnership Program (NOPP)-supported HYCOM (HYbrid Coordinate Ocean Model) consortium effort, to develop and transition an eddy-resolving, real-time global and basin-scale ocean prediction system. These systems are being transitioned for operational use by the U.S. Navy at the Naval Oceanographic Office (NAVOCEANO), Stennis Space Center, MS. This project builds upon work begun with Naval Research Laboratory contract N000173-06-2-C003, and reported on in Arbic et al. (2010).

The overall technical goal is to implement a 1/25 deg horizontal resolution global ocean prediction system based on the HYbrid Coordinate Ocean Model (HYCOM) with tides and dynamic sea ice. The scientific goals include but are not limited to a) evaluation of the internal tides representation in support of field programs, b) data assimilation in the presence of tides, c) evaluation of the model's ability to provide useful boundary conditions to high resolution coastal models, d) interaction of the open ocean with ice, e) shelf-deep ocean interactions, f) upper ocean physics including mixed layer/sonic depth representation, g) mixing, etc.

The ultimate limitations to the performance of long-range sonar are due to ocean sound speed perturbations and the characteristics of the ambient acoustic noise field. Scattering and diffraction resulting from internal waves and other ocean processes limit the temporal and spatial coherence of the received signal, while the ambient noise field is in direct competition with the received signal. Research conducted in the North Pacific Acoustic Laboratory (NPAL) program at the Applied Physics Laboratory (APL-UW) is directed toward a complete understanding of the basic physics of low-frequency, long-range, deep water, broadband acoustic propagation, the effects of ocean variability on signal coherence, and the fundamental limits to signal processing at long-range that are imposed by ocean processes. The long-term goal of NPAL is to optimize advanced signal processing techniques, including matched-field processing and adaptive array processing methods, based upon knowledge about the multi-dimensional character of the propagation and noise fields and their impact on long-range ocean acoustic signal transmissions.

We are interested in the general problems of internal waves and ocean mixing. Knowledge of these is important for advancing the performance of operational and climate models, as well as for understanding local problems such as pollutant dispersal and biological productivity. In the specific case of NLIWs, the currents and displacements of the waves are strong enough to impact undersea operations. More generally, most of the ocean s physical and acoustic environments (particularly in straits) are severely impacted by internal waves. The research described here substantially improves both our understanding and predictive ability of linear internal tides and NLIWs in Luzon Strait and the South China Sea., Additional grant no. N00014-09-1-0184.

The long-term goal is to enhance our understanding of coastal oceanography by means of applying simple dynamical theories to high-quality observations obtained in the field. Objectives: * Conduct a field program in the South China Sea to determine the combined impact of large submarine sand dunes (hereafter dunes) and large amplitude nonlinear internal waves (hereafter waves) on sound transmission over the Chinese continental slope near Taiwan * Determine how the nonlinear internal waves (NLIW) and tides interact with the seafloor to form and maintain the dunes * Study how enhanced bottom roughness in the dune field affects energy dissipation in the NLIWs and tides as they shoal over the upper continental slope.

Presented at the Layered Ocean Model Workshop held in Ann Arbor, MI on 21-23 May 2013.

Presented at the Layered Ocean Model Workshop held in Ann Arbor, MI on 21-23 May 2013. Prepared in cooperation with the Univ of Michigan, Bangor Univ, and the Univ of Brest.

This Coastal and Hydraulics Engineering Technical Note (CHETN) describes the second module of the MetOcnDat (Meteorological and Oceanographic or Metocean) system, called TideNet. The MetOcnDat modular system in development consists of toolboxes for waves, tides, and river flow databases that will facilitate conversion of data used in input files for numerical models and provide tabular and graphical information for project planning and design reports. TideNet is a web-based Graphical-User-Interface (GUI) data management tool that allows users to access, process, and analyze tide data available from different tidal databases. This first application of TideNet deals only with tide data from the National Weather Service (NWS) database used in various coastal, ocean, and marine engineering applications. Metocean data include winds, waves, tides (water levels and currents), and river discharges. The first two Technical Notes (TNs) in the MetOcnDat system series (Demirbilek et al. 2013; Wilson et al. 2012) described the application of WaveNet, a companion module of TideNet, for the National Data Buoy Center (NDBC) buoy and Wave Information Stduy (WIS) databases. The TideNet is a web-based GUI that provides users with GIS mapping tools to query tide data sources in a desired geographic region of USA and its territories. Users can select a tide data source through the Google Map interface to view data and parameters of interest. The utilities of TideNet available at the selected tide data source can query the data source, then plot, analyze, and extract tidal information based on a user-specified time window and output data in different formats for engineering applications. TideNet has additional post-processing capabilities to produce tables and figures and prepare input files for numerical models.

The Federal Emergency Management Agency, Region III office, has initiated a study to update the coastal storm surge elevations within the states of Virginia, Maryland, and Delaware, and the District of Columbia including the Atlantic Ocean, Chesapeake Bay including its tributaries, and the Delaware Bay. This effort is one of the most extensive coastal storm surge analyses to date, encompassing coastal floodplains in three states and including the largest estuary in the world. The study will replace outdated coastal storm surge stillwater elevations for all Flood Insurance Studies in the study area, and serve as the basis for new coastal hazard analysis and ultimately updated Flood Insurance Rate Maps (FIRMs). The end-to-end storm surge modeling system includes the Advanced Circulation Model for Oceanic, Coastal and Estuarine Waters (ADCIRC) for simulation of two-dimensional hydrodynamics. ADCIRC was dynamically coupled to the unstructured numerical wave model Simulating WAves Nearshore (unSWAN) to calculate the contribution of waves to total storm surge. The modeling system validation included a comprehensive tidal calibration followed by an assessment using carefully reconstructed wind and pressure fields from three major flood events for the Region III domain: Hurricane Isabel, Hurricane Ernesto, and Extratropical Storm Ida. Model skill was accessed by quantitative comparison of model output to wind, wave, water level, and high water mark observations. Prior reports covered Submittal 1 requirements by providing details on the bathymetric/topographic digital environmental model (Report 1.1), description of the computational system (Report 1.2), and documenting the selection process for storms used in the study (Report 1.3). This report (2.0) completes the required Submittal 2 documentation by providing details of the modeling system calibration and performance., Sponsored in part by USACE. Prepared in cooperation with Renaissance Computing Institute, Chapel Hill, NC and ARCADIS, Boulder, CO.

Our long-term scientific goals are to understand the dynamics and identify mechanisms of small-scale processes in the ocean with the objective of developing improved parameterizations of mixing for ocean models. Internal tides, inertial waves, nonlinear internal waves (NLIWs), and turbulence mixing are all key components to understanding mixing within the stratified ocean. Each of these factors can lead to uncertainty within current ocean models due to their complex interplay. This study focuses primarily on small-scale processes, internal tides, and also key circulation features including cold dome events localized at the continental slope of the East China Sea (ECS) and intrusions generated as the Kuroshio and barotropic tides interact with the continental shelf of the ECS. These small-scale processes and circulation features modulate the temporal, horizontal, and vertical spatial structures of the water properties of the ocean. These processes may significantly modify acoustic properties and thus introduce uncertainty into sonar performance and acoustic propagation models. Our ultimate goal is to collaborate with acousticians to identify oceanic processes that alter acoustic properties. A detailed understanding of these properties, mechanism, and dynamics will aid in quantification and assessment of uncertainty in acoustic prediction., The original document contains color images.

Tidal turbines harness hydrokinetic energy resulting from ocean tidal flows to generate power. This type of power generation is a potential source of clean, reliable renewable energy. However, the technology is still under development. The effects of unsteady flow conditions, specifically surface gravity waves, on tidal turbines have not been completely analyzed. The effects of waves on performance characteristics were assessed for a model horizontal axis tidal turbine selected by the Department of Energy and designed by the National Renewable Energy Laboratory (NREL). The performance characteristics of the 1/25th scale model turbine were tested under unsteady flow conditions. Parameters including wave height, wave length and tow speed for the experiment were scaled to properly model flow conditions that a horizontal axis tidal turbine was expected to experience at a full scale. First, turbine rotational speed, torque and thrust were measured for steady flow conditions and unsteady flow conditions characterized by a range of incoming waves. Turbine performance characteristics, including thrust and power coefficients, were obtained as functions of rotor tip speed ratio for the unsteady flow conditions tested. The second experiment involved a detailed fluid flow survey in the near wake of the turbine with and without one of the waves utilized in the first experiment, as measured by Acoustic Doppler Velocimeters. The results provided a characterization of velocity fields in the near wake of the turbine, necessary information for the placement of multiple turbines in a larger array., The original document contains color images.

The ocean flows and undulates in response to wind stress, heating and cooling, and the gravitational attraction of the Sun and Moon. For the first time, Naval Research Laboratory scientists, in collaboration with university colleagues, have simulated ocean tides concurrently within the ocean circulation over the entire globe at very high resolution.1 The surface tides interact with bottom topography to generate internal waves. Surprisingly, the strongest internal tide generation is not where the surface tides are the largest. The strongest interactions occur in limited regions, oceanic internal wave hot spots. The internal waves radiate away from the hot spots as focused beams, which propagate for thousands of kilometers, and are an important source of energy for mixing the ocean interior. Both the ocean circulation and the tidal flow of the model compare well to a new set of global observations consisting of satellite altimeter tidal heights, historical moored current meters, and drifting buoys. The new model allows estimates of the ocean currents and tidal elevations anywhere on the globe at any time.

This study contributes to long-term efforts toward understanding: the origins of the Kuroshio Current and circulation of the Western Pacific. The proposed observational program focuses on understanding: the annual cycle of the Kuroshio and its associated mesoscale variability, quantifying Kuroshio spatial structure and temporal evolution, and investigating Kuroshio and mesoscale response to strong monsoonal forcing. The boundary currents off the east coast of the Philippines are of critical importance to the general circulation of the Pacific Ocean. The westward flowing North Equatorial Current (NEC) runs into the Philippine coast and bifurcates into the northward Kuroshio and the southward Mindanao Current (MC) (Figure 1; Nitani, 1972). The partitioning of the flow into the Kuroshio and MC is an important observable. Quantifying these flows and understanding bifurcation dynamics are essential to improving predictions of regional circulation, and to characterizing property transports that ultimately affect Pacific climate. Fluctuations in the Kuroshio and MC can significantly impact variability downstream. For example, the Kuroshio penetrates through Luzon Strait into the South China Sea and onto the East China Sea shelf. The Kuroshio front dramatically alters stratification and may impact internal wave climate. This effort focuses on quantifying Kuroshio variability and dynamics in the formation region east of Luzon and Taiwan.

The long term research goal of this project is to develop a clear picture of the key processes involved in internal tide generation at the Luzon Strait through the use of laboratory experimentation supported by analytical modeling, and thereby assist the predictive capability for large amplitude solitary waves in the South China Sea. The objective is to design and execute the necessary laboratory experiments in appropriate dynamic regimes. To use this to clearly determine the big picture regarding internal tide generation at the Luzon Strait. To share these results with researchers performing numerical simulations and field studies and support the interpretation of their data sets. The primary approach is to perform a large scale laboratory experiment at the Coriolis platform in Grenoble, France, in which a realistic model of the topography is used and care is taken so that the key geometrical and dynamical parameters in the experiment are consistent with those of the ocean. The internal wave fields generated in the laboratory are studied using a variety of experimental techniques, in particular Particle Image Velocimetry to obtain velocity field data. The data from these experiments is processed and visualized in a variety of ways in order to explain the observed wave dynamics. The experiments were performed in Fall 2010, producing a vast amount of data. Experiments were run for a wide range of forcing amplitudes, single and multiple forcing frequencies, and stratifications. Since then, the PIV data sets for these experiments have been processed to obtain velocity field data for all the key experiments, and further processing of this data has been used to generate our results.

We are focused on understanding small-scale processes that influence the ocean s thermodynamic and dynamic properties on the sub-mesoscale (scales less than 10 km). This includes the enhanced internal waves generation and turbulent processes occurring in the Luzon Passage at the Lan-Yu and Heng-Chun ridges. The waters of the Luzon Passage are among the most energetic environments in the global ocean. Tidal currents as large as 0.8 m/s and strong stratification over the steep ridge topography give rise to internal wave generation, driving baroclinic currents. In addition, the Kuroshio Current often drives strong flow through the area. Not surprisingly, this environment supports exceptional turbulent energy levels distributed over full depth, leading to mixing between the South China Sea and Kuroshio water masses. Here, we present the first full-depth, direct measurements of turbulence along the Lan-Yu Ridge of the Luzon Straits over a spring neap cycle of tidal forcing. Data were collected on the east and west slopes of a ridge crest suggested by model results to be the site of exceptional baroclinic conversion of the barotropic tide. Measurements at each of these locations show that the strongest turbulence levels occur during the phase of the flood-ebb cycle when flow is in the downhill direction, indicating either hydraulic or slope convection processes. Our analysis shows very large turbulence levels, with dissipation rates reaching 105 W/kg at 1000-m depth, and depth-integrated dissipation rate levels reaching 1 W/m2. This implies that at least 10% of the locally generated baroclinic energy is dissipated directly before radiating away and suggests that local turbulent processes have considerable impact on the internal wave generation occurring at this region., Prepared in collaboration with the Dept. of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA.

This study contributes to long-term efforts toward understanding: upper ocean response to atmospheric forcing and submesoscale dynamics of the mixed and transition layer. This program also follows the team s long-term focus on developing new approaches for exploiting autonomous technologies for conducting process-level measurements. Objectives are to: A) Characterize the upper ocean response to typhoon forcing, in particular the temporal and spatial evolution of the cold wake generated by a typhoon and B) Demonstrate the utility of a new glider-borne microstructure sensor package for collecting high-quality turbulence measurements over the course of long-duration (weeks to months) deployments. The Impact of Typhoons on the Ocean in the Pacific (ITOP) program brought together an international team of oceanographers and atmospheric scientists to conduct a highly collaborative investigation of the oceanic response to typhoon forcing. Novel aspects of this program included the availability of C130 aircraft capable of air-dropping autonomous assets directly in front of propagating typhoons and extended access to a global-class research vessel, R/V Roger Revelle, stationed in Kaoshiung and capable of carrying autonomous assets and rapid survey capability into the typhoon s cold wake, shortly after the storm s passage. This permitted direct measurement of both the immediate response to the typhoon s passage and the longer timescale evolution of the resulting cold wake. This project focused on understanding cold wake evolution using a fleet of ten long-endurance autonomous Seagliders (three of which were equipped with temperature microstructure sensors) and ship-based surveys employing a rapid-profiling underway CTD.

We seek a more complete and fundamental understanding of the hierarchy of processes that transfer energy and momentum from large scales, feed the internal wave field, and ultimately dissipate through turbulence. This cascade impacts the acoustic, optical, and biogeochemical properties of the water column, and feeds back to alter the larger scale circulation. Studies within the Ocean Mixing Group at OSU emphasize observations, innovative sensor / instrumentation development and integration, and process-oriented internal wave and turbulence modeling for interpretation. Luzon Strait represents a major source of internal tides and NLIWs in the SCS. However, unlike other regions of strong internal wave generation (i.e., Hawaii), Luzon Strait is believed to be highly dissipative. We seek to understand the character of this enhanced nonlinearity and turbulence, and how it affects internal wave generation and transmission.

The long term goals are to use observations and analysis of stratified flow past complex topography to understand how internal tidal interaction in straits is responsible for the generation of large amplitude high frequency internal waves. Our objectives include the development and deployment of a 2-D array of pressure-sensor-equipped inverted echo sounders (PIES) so as to observe the generation of internal waves by tidal interaction with topography in Luzon Strait, and to interpret the results using appropriate models of internal wave formation and evolution. Our approach required construction of a 2-dimensional array of PIES (Li et al. 2009) and their deployment for 9 months both within Luzon Strait and in the deep basin to its west. In addition, the plans included a single instrument deployment east of the strait so as to acquire time series measurements of internal waves radiating into the Pacific. The observations provide a basis for testing models of the generation and evolution of topographically generated internal waves. PIES measure the return acoustic travel time between the sea floor and surface, as well as the local pressure. The measurement effectively filters out the higher modes, revealing the first internal mode response. The effects of barotropic pressure variations are removed from the time series. This work has being carried out with collaboration of M Alford (APL U. Washington, instrument deployments), M Buisjman (GFDL Princeton, model comparisons), H Simmons (SFOS U Alaska, model comparisons), Y-J Yang (Naval Academy, Taiwan, instrument deployment/recovery) and other IWISE team members.

Our long-term scientific goals are to understand the dynamics and identify mechanisms of small-scale processes i.e., internal tides, inertial waves, nonlinear internal waves (NLIWs), and turbulence mixing in the ocean and thereby help develop improved parameterizations of mixing for ocean models. Mixing within the stratified ocean is a particular focus as the complex interplay of internal waves from a variety of sources and turbulence makes this a current locus of uncertainty. For this study, our focus is on generation, propagation, evolution, and dissipation of small-scale internal waves and internal tides as the Kuroshio and barotropic tides interact with the two prominent submarine ridges in Luzon Strait. The primary objectives of this observational program are to quantify 1) the generation of NLIWs and internal tides in the vicinity of Luzon Strait, 2) the energy flux of NLIWs and internal tides into the Pacific Ocean and South China Sea (SCS), 3) the effects of the Kuroshio on the generation and propagation of NLIWs and internal tides, 4) the seasonal variation of NLIWs and internal tides, and 5) to study other small-scale processes, e.g., hydraulics and instabilities along internal tidal beams and at the Kuroshio front.

Our long-term goals are to develop a physical understanding of the processes which lead to mixing in the ocean, with the aim of using this understanding to develop parameterizations of mixing suitable for global and regional models, and applying such models to societally relevant problems. A particular focus is the mixing induced by tidal flow over topography, and mixing induced by breaking nonlinear internal waves. The scientific objectives of this study are to explore internal waves generated by tidal flow through straits in the region close to the sill. Our geographic focus is the Luzon Straits. A particular scientific focus is nonlinear overturning and breaking within the straits leading to mixing and modification of the wave field. One possibility which we examine is whether transient internal hydraulic jumps are possible in the Luzon Straits, whether these jumps are released to propagate toward the topography as internal bores when the flow relaxes, and whether the bores lead to local mixing. We explore the details of the Luzon Strait topography to identify locations particularly conducive to local overturning processes. The Luzon Strait features two parallel north south oriented ridges; we examine how the wave fields of the two ridges interact and affect wave generation and mixing processes. We also examine the importance of three-dimensional bathymetry in determining the locations of mixing. To summarize, our goals are to (a) examine the dependence of nonlinear features and local breaking at the generation site on topographic shape and stratification; (b) evaluate how the interaction between the ridges affect the mixing; (c) examine the extent to which the mixing processes are determined by three-dimensional topography variations.

Our long-term scientific goals are to understand the dynamics and identify mechanisms of small-scale processes i.e., internal tides, inertial waves, nonlinear internal waves, vortical modes, and turbulence mixing in the ocean and thereby help develop improved parameterizations of mixing for ocean models. Mixing within the stratified ocean is a particular focus as the complex interplay of internal waves from a variety of sources and turbulence makes this a current locus of uncertainty. Our focus is on observing processes that lead to lateral mixing of water properties. Our primary scientific objective is to improve our understanding and parameterization schemes of small- to submeso-scale oceanic processes. Dispersion due to lateral processes with vertical and horizontal shears could enhance turbulent mixing. Both internal waves and vortical motions exist at vertical scales smaller than order of 10 m and horizontal scales smaller than few km. They have distinct kinematics and dynamics. Internal waves propagate and may carry energy to remote regions before they break and dissipate via turbulent processes, whereas vortical motions do not propagate and are often long lived. Separation of these two motions is necessary to improve parameterization schemes., Prepared in collaboration with the School of Oceanography, University of Washington, Seattle.

Ocean tides, and the atmospherically forced oceanic general circulation and its associated mesoscale eddy field, have long been run separately in high-resolution global models. They are now being simulated concurrently in a high-resolution version of the HYbrid Coordinate Ocean Model (HYCOM). The incorporation of horizontally varying stratification with the addition of atmospheric forcing yields internal tides (internal waves of tidal frequency) in high-latitude, low-stratification regions that are qualitatively different from those in earlier global internal tide models, in which atmospheric forcing and horizontally variable stratification were absent. The internal tides in the new concurrent HYCOM simulations compare well with those measured in along-track satellite altimeter data. The new concurrent simulations demonstrate that the wavenumber spectrum of sea surface height --a measure of the energy contained in different length scales is dominated in some locations by internal tides and in others by mesoscale eddies. Tidal kinetic energies in the new concurrent simulations compare well with those in current-meter observations, as long as sufficient spatial averaging is performed. The new concurrent simulations are being used in the planning of future-generation satellite altimeters, in the provision of boundary conditions for coastal ocean models, and in studies of ocean mixing., The original document contains color images. Published in Oceanography, v25 n2 p20-29, 2012.

The morphodynamics of the John's Pass-Blind Pass dual inlet system were investigated based on hydrodynamic and morphology measurements, and numerical modeling. The co-existence of the dual inlets is realized by the dominance of mixed-energy John's Pass in terms of tidal prism and size of the ebb delta and the artificial maintenance of the wave-dominated migratory Blind Pass. Due to the secondary role of Blind Pass, the aggressive anthropogenic activities there do not seem to have a significant influence on the morphodynamics of John's Pass. On the other hand, the opening (in 1848) and subsequent evolution of John's Pass had substantial influence on Blind Pass, causing it to migrate rapidly to the south. In addition anthropogenic activities had much more influence on the morphodynamics of the secondary Blind Pass than that of the dominating John's Pass. Results from numerical modeling provide a semi-quantitative understanding of the hydrodynamics and morphodynamics of John's Pass and Blind Pass in association with cold front passages, which have substantial influences on inlet morphology. Two large eddies are modeled from the interactions between the southward longshore current and John's Pass ebb and flood flow, respectively. These eddies are closely related to the morphodynamics of the channel margin linear bar and longshore transport divergence at the downdrift side. Both are key features of a mixed-energy inlet. The shallow water and wave-breaking-induced longshore current and elevated sediment suspension along the ebb delta terminal lobe provide the pathway for sediment bypassing. The morphodynamics of Blind Pass are dominated by wave forcing. The weak ebb jet is not capable of forming a sizable ebb delta and tends to be deflected by the strong longshore current, causing elevated longshore transport along the downdrift beach., Published in Marine Geology v291-294 p162 175, 2012. Sponsored in part by Pinellas County, Florida. Prepared in cooperation with the Department of Geology, University of South Florida, Tampa.

The long-term goal is to use the HYbrid Coordinate Ocean Model (HYCOM) with tides, dynamic sea ice, and data assimilation in an eddy-resolving, fully global ocean prediction system with 1/25 horizontal resolution that will run in real time at the Naval Oceanographic Office (NAVOCEANO) starting in FY13. The model will include shallow water and provide boundary conditions to finer resolution coastal models that may use HYCOM or a different model. The objective is to develop, evaluate, and investigate the dynamics of 1/25 global HYCOM (HYbrid Coordinate Ocean Model) with tides coupled to CICE (Los Alamos Community Ice CodE) with atmospheric forcing only, with data assimilation via NCODA (NRL Coupled Ocean Data Assimilation), and in forecast mode. Also to incorporate advances in dynamics and physics from the science community into the HYCOM established and maintained within the Navy., The original document contains color images.

In the Golden Gate (San Francisco) inlet, tidal currents are dominant and have complex spatial and temporal variations owing to the large size of estuary connected through the narrow channel and the shallow ebb shoal (bar) at the mouth. To capture such variations, shipboard ADCP profiling is a technically viable approach that can yield unique insight into the vertical structure of currents. Shipboard ADCP data from four cruises conducted by the R/V Point Sur in the San Francisco Bight are used in this study. Transects along the channel axis were automatically extracted from the irregularly sampled underway data using changes in speed and heading in combination with geographic criteria. Processed data contains transects traversed in various tidal conditions. Flood currents are bottom intensified with more strength in the relatively deeper area of the channel. In low tidal range conditions, the directions and speed of surface currents are nearly uniform along the entire channel. Ebb currents are surface intensified, decreasing from the Golden Gate to the bar. In low tidal range, near-surface and bottom currents flow in opposite directions. The tidal currents exhibit cross channel variations in strength. Ebb results in surface outflow mainly along the northern part of entrance, whereas the flood flow is strongest along the southern part.

Ocean tides, and the atmospherically forced oceanic general circulation and its associated mesoscale eddy field, have long been run separately in high-resolution global models. They are now being simulated concurrently in a high-resolution version of the HYbrid Coordinate Ocean Model (HYCOM). The incorporation of horizontally varying stratification with the addition of atmospheric forcing yields internal tides (internal waves of tidal frequency) in high-latitude low-stratification regions that are qualitatively different from those in earlier global internal tide models, in which atmospheric forcing and horizontally variable stratification were absent. The internal tides in the new concurrent HYCOM simulations compare well with those measured in along-track satellite altimeter data. The new concurrent simulations demonstrate that the wavenumber spectrum of sea surface height a measure of the energy contained in different length scales is dominated in some locations by internal tides and in others by mesoscale eddies. Tidal kinetic energies in the new concurrent simulations compare well with those in current-meter observations, as long as sufficient spatial averaging is performed. The new concurrent simulations are being used in the planning of future-generation satellite altimeters, in the provision of boundary conditions for coastal ocean models and in studies of ocean mixing., Published in Oceanography, v25 n2 p20-29, June 2012.

This project, with Eric Kunze at the University of Victoria (now at APL-UW), was undertaken as part of a Departmental Research Initiative (DRI) of the Office of Naval Research (ONR) entitled AESOP (Assessing the Effectiveness of Submesoscale Ocean Parameterizations). The principal goals of AESOP were to (a) increase the understanding of ocean dynamics particularly processes that are not included or not resolved in numerical models and (b) improve forecasts of ocean conditions. Our (Girton and Kunze) component of the experiment was focused on internal tides and mixing, both in terms of constraining the dominant mechanisms supplying energy for mixing in the ocean and for the purposes of explaining tidal and internal wave velocity variance in the coastal ocean. The principal tasks of AESOP were a set of ocean observations designed to evaluate submesoscale processes (including internal tides and small-scale fronts and eddies) in a suite of models of the coastal ocean around Monterey Bay. These observations formed metrics that could be used to test the representation of the processes in the models. In addition, model studies were undertaken to study the impact of those processes on the larger-scale fields., Report contains color.

The long-term sea level change during 1993 to 2008 was investigated in the Malaysian seas from satellite altimetry data of the TOPEX, JASON-1, ERS-1, ERS-2 and ENVISAT missions. Sea level data retrieval and reduction were carried out using the radar altimeter database system (RADS). In RADS data processing, the 2008 updated environmental and geophysical corrections were applied. Six 1° × 1° areas were chosen for the altimetry data comparison and to find the best ocean tide model for the Malaysian seas, where the altimeter tracks are nearby tide gauge locations. Similarity in the patterns of sea level variations indicates good agreement between tide gauge and altimetry data when using the FES2004 ocean tide model. It also shows that altimetry data is perfectly suited to investigate long-term sea level change in the Malaysian seas. Here, sea level variations for four areas in the Malaysian seas have been investigated using 15 years of altimetry data. The altimeter sea level time series revealed that since 1993, the mean sea level in Malaysian seas has been rising at a geographically-dependent rate varying from 1.4 to 4.1 mm/yr. This kind of information is important for studying environmental issues related to flood investigations and global warming especially for an area that until now have not gotten much attention from the altimeter science community., Space Engineering, Aerospace Engineering

The long-term sea level change during 1993 to 2008 was investigated in the Malaysian seas from satellite altimetry data of the TOPEX, JASON-1, ERS-1, ERS-2 and ENVISAT missions. Sea level data retrieval and reduction were carried out using the radar altimeter database system (RADS). In RADS data processing, the 2008 updated environmental and geophysical corrections were applied. Six 1° × 1° areas were chosen for the altimetry data comparison and to find the best ocean tide model for the Malaysian seas, where the altimeter tracks are nearby tide gauge locations. Similarity in the patterns of sea level variations indicates good agreement between tide gauge and altimetry data when using the FES2004 ocean tide model. It also shows that altimetry data is perfectly suited to investigate long-term sea level change in the Malaysian seas. Here, sea level variations for four areas in the Malaysian seas have been investigated using 15 years of altimetry data. The altimeter sea level time series revealed that since 1993, the mean sea level in Malaysian seas has been rising at a geographically-dependent rate varying from 1.4 to 4.1 mm/yr. This kind of information is important for studying environmental issues related to flood investigations and global warming especially for an area that until now have not gotten much attention from the altimeter science community., Space Engineering, Aerospace Engineering