The Role of Laser Ranging for Calibrating Jason-1: The Corsica Tracking Campaign

The French Transportable Laser Ranging System (FTLRS), a highly transportable Satellite Laser Ranging (SLR) instrument, was set up in Corsica (from January to September 2002) for participating to the JASON-1 altimeter verification phase. In addition to the tracking of oceanographic satellite missions and in order to perform an accurate positioning, the FTLRS also acquired laser ranging data on geodetic satellites, STARLETTE and STELLA essentially.

The paper describes the analysis strategy mainly based on the use of a short-arc orbit technique to compute accurate 1 cm local orbits, and then the geocentric positioning (2–3 mm relative to GPS). Finally, we established the JASON-1 absolute calibration value, based on 9 SLR short-arcs (between cycles 1 and 26), at 108.2 ± 8.7 mm; the 10-day repeatability is of 26.1 mm showing that a great accuracy has been reached.     

Tidal and Nontidal Oscillations in Elkhorn Slough,CA

Elkhorn Slough is a shallow, tidally forced estuary that is directly connected to Monterey Bay. It is ebb-dominated and, due to continued erosion, the tidal prism has tripled over the past 40 years. Water level measurements at four locations are used to examine tidal and nontidal oscillations in Elkhorn Slough. The tidal response of Elkhorn Slough differs from that of Monterey Bay primarily due to the generation of a relatively large number of shallow-water tidal constituents that are due to tidal distortion caused by friction along the bottom and lateral boundaries, intertidal storage, and nonlinear advection. The shallow-water constituents range from 3 to almost 15 cycles per day (cpd) and include a rich variety of overtides and compound tides, whose amplitudes generally increase toward the head of the slough. The tidal harmonics are seasonally dependent, with lower amplitudes during the fall and winter and higher amplitudes in summer. The tidal constituents were examined using two types of spectral decomposition, the conventional power spectrum and the more recent Hilbert spectrum. Unlike the power spectrum, the Hilbert spectrum does not reveal any harmonic structure in the data. Energy associated with tidal distortion in this case appears to be broadly distributed across the spectral continuum. At least four nontidal oscillations occur in Elkhorn Slough with frequencies of 26.0, 39.7, 52.7, and 66.9 cpd. The Hilbert spectrum reveals maxima at 26, 39.7, and 66.9 cpd, but not at 52.7 cpd, suggesting that it is harmonically related to the oscillation at 26.0 cpd. The nontidal oscillations fall into the range of frequencies associated with the natural oscillations of Monterey Bay. However, evolutionary power spectra indicate that they appear to be permanent features of the system and thus are not necessarily consistent with seiche-like oscillations that are often transient and subject to damping. These oscillations could be caused by several factors including edge waves along the coast of Monterey Bay, long-period surface waves of atmospheric origin that enter the bay from offshore, or breaking internal waves in and around the Monterey Submarine Canyon. In conclusion, detailed hydrodynamic models are needed to provide a better understanding of how tidal harmonics are generated and preserved in Elkhorn Slough, and to determine the origin of the natural oscillations in Monterey Bay.     

Review on Tidal Energy Technologies and Research Subjects

Tidal current power is one of the promising and reliable renewable energies with the advantage of continuous and predictable resource. It can make stable electricity regardless of weather conditions or seasons all year around. The required technologies for tidal current power in the ocean have been developed for years and now recognized that it could be commercialized after intensive field tests and successful demonstrations. There are several tidal farm development projects in the world, such as the MeyGen project in UK with its commercialization at hand. However, various research subjects in the tidal current energy field are seeking improvements and industrialization of tidal current power in terms of economy and technical reliability. This paper introduces the resource assessment procedure of tidal energy that has been applied in Korea coastal regions. The key research subjects for tidal current power together with the interaction effect of multi-arrangement is described. Also, this paper is to introduce the research output of each subject such as turbine design, experimental validation, turbine interaction and wake, multi-array module, FSI (fluid-structure interaction), and duct application.     

Estimate of Coastal Water Depth Based on Aerial Photographs Using a Low-Altitude Remote Sensing System

Ocean Science Journal - Observing coastal water depths is very important to understand physical processes of the coastal environment and manage coastal resources. In this study, a low-altitude...     

An allostratigraphic approach to a non-marine basin: the north-western part of Cretaceous Kyongsang Basin, SE Korea

The north-western part of the Cretaceous Kyongsang Basin, south-east Korea, comprises alluvial deposits of conglomerate, gravelly sandstone, sandstone and mudstone which can be grouped into four allomembers bounded by stratigraphic discontinuities. The discontinuities trend NW–SE and are marked by distinct facies transitions, abrupt emplacement of conglomerate and thin but persistent mudstone beds. Sedimentary facies and architectural analyses reveal that each allomember formed a depositional system of fluvial channel networks draining toward the south-east with alluvial fans on the northern margin. Each allomember can be characterized by distinctive architecture of channel-fills, clast composition of conglomerate and sandstone/mudstone ratio. Successive units show an eastward shift in the locus of deposition, suggesting basinward relocations of alluvial systems. Such variations with time and space are interpreted to reflect changes in accommodation space and sediment supply during basin evolution, probably caused by fault movements. This study shows that detailed mapping, combined with architectural analysis, and the establishment of alluvial allostratigraphy can help assess changes in alluvial systems and structural development of the basin.     

Orbitally forced sedimentary rhythms in the stratigraphic record: is there room for tidal forcing?

The imprint of orbital cycles, which result from the varying eccentricity of the Earth’s orbit and changes in the orientation of its axis, have been recognised throughout the Phanerozoic rock record. Variations in insolation and their effect on climate are generally considered to be the sole transfer mechanism between the orbital variables and cyclic sedimentary successions. Common oceanographic principles, however, show that the ocean tide also responds to variations in the orbital parameters. The ocean tide has not yet been considered to be a valid, additional transfer mechanism for the orbital variations. In geological studies of Milankovitch cycles in sedimentary successions the insolation paradigm offers satisfying explanations, and the role of long‐term variations of the ocean tide has not yet been appreciated. Variations in the ocean tide, related to changing eccentricity (at present 0·0165, theoretical maximum 0·0728), affect a variety of oceanographic and sedimentary processes. In addition to the widely accepted paradigm of orbitally forced insolation changes, the tidal transfer of orbital signals may explain certain less well‐understood aspects of orbitally induced cycles in the stratigraphic record related to ocean mixing, organic productivity, and tidal processes in shallow seas and deep water. Variations of the ocean tide in relation to the 18·6 year lunar nodal cycle, which has no insolation counterpart by which they may be obscured, indeed show that these relatively small variations can produce significant effects in sedimentary environments that are sensitive to variations in the strength of the ocean tide. In analogy with the 18·6 year lunar nodal cycle, orbital variations of the tide on Milankovitch time scales are likely to have affected sedimentary systems in the past.