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This is a review of sea level data performed at three selected stations (Quebec-Lauzon, Harrington Harbour,and Halifax) in eastern Canada in order to investigate the seasonal trends and other long-term and short-term changes which occurred since the beginning of the 20th century. Stations situated in riverine or estuarine regions (e.g., Quebec-Lauzon) are significantly affected by freshwater flow in their annual cycle of sea level changes and exhibit a definite maximum in spring and minimum in autumn-winter. Other stations situated in the eastern half of the Gulf of St. Lawrence (e.g., Harrington Harbour) or near the open Atlantic coast (Halifax) mainly follow the general cycle of subarctic regions, with lows in spring-summer and highs in autumn-winter. Such seasonal variations appear to be related to the atmospheric pressure and baroclinic current variations. Secular trends in mean sea level in eastern Canadian waterbodies show a mean rise of about 2.56 mm/yr -1 due to tectonic motions, that is, land sub...

Interannual variations of sea level along the Bangladesh coast are quite pronounced and often dominate the long-term sea level trends that are taking place. The El Nino/Southern Oscillation (ENSO) induced variation is an important component of interannual mode of variations. The present article deals with the relationship between the sea level variations along the Bangladesh coast and the Southern Oscillation phenomenon. The mean tide level data of monsoon season (June to September) pertaining to Hiron Point (in Sundarbans) and Char Changa (on the mouth of Meghna River) have been analyzed and correlated to the Southern Oscillation Index (SOI). The annual variation of mean tide level in the coastal areas of Bangladesh reveals that the tide level reaches its peak during the monsoon season. The maximum tide level during the calendar year is recorded in August. Thus, it is not surprising that the inundation of the coastal belt of Bangladesh due to the floods is most common during the summer monsoon season, es...

Hourly sea level records from three stations in eastern Canada (Quebec-Lauzon, Harrington-Harbour and Halifax) are analyzed both in frequency domain from 1970 to 1979 and in time domain during 1973. At the three stations, the deterministic model explains 90 to 96% of the total variability of sea level. The semidiurnal and diurnal tides contribute largely to its variations. The residual series, less than 10% of the initial variations of sea level, contain irregular values including extreme values of seiches and storm surges. Such random variations are analyzed and modeled following the method described by Box and Jenkins (1976). The long period variations (2 to 30 days) can be attributed to meteorological forcing (atmospheric pressure and winds). The short period variations (some hours to one day) can be attributed to longitudinal seiches, semidiurnal and diurnal atmospheric tides, and inertial oscillations. The water discharge from the St. Lawrence River contributes 29% of the monthly residual sea level a...

The International Tsunami‐93 Symposium was sponsored jointly by the Tsunami Commission of the International Union of Geodesy and Geophysics and the International Coordination Group of the Intergovernmental Oceanographic Commission of UNESCO. It was organized by the Japan Society of Civil Engineers and was held in Wakayama, Japan, August 23–25, 1993. This review is based on the proceedings of the Conference, which were jointly edited by Professors Yoshito Tsuchiya and Nobuo Shuto. In total about 142 participants from 19 countries attended the symposium. They presented some 65 papers in 12 sessions dealing with various topics. Selected papers from the conference are briefly reviewed and highlights of the conference are noted.

A vertically integrated two‐dimensional (2‐D) and a five‐layer three‐dimensional (3‐D) numerical models were developed to compute the tides in the Gulf of Suez, Egypt. The computational grid used to schematize the Gulf has a horizontal resolution of 3 × 3 km and consists of a lattice of 23 × 100 points in the 2‐D model and five such lattices in the 3‐D model. Both 2‐D and 3‐D simulations clearly revealed the Kelvin wave nature of the tide with partial reflection. The M2 simulations also showed a strong tidal signature in the southern sector as compared to the northern part. For the 3‐D simulations, the horizontal and vertical eddy viscosity coefficients and the coefficient of bottom friction were respectively set to 3 × 106 cm2/s, 200 cm2/s, and 0.001. The tidal range decreases from the entrance of the Gulf of Suez toward the Bank of Tor where it reaches a small value and then increases again to about 1.5 m at Suez. A difference of six hours exists between the times of high water at the southern and north...

A two‐dimensional, nonlinear, vertically integrated model for the Gulf of Suez, Egypt, was used to simulate the interaction between tides and the surge heights resulting from a 15 m/s storm blowing from the northwestern direction for 24 hours. The results show that the predominant surges as well as the envelope of the tide plus surge curve are all negative throughout the whole area of the Gulf of Suez and increasing northward. It was shown that, although in principle, the shallow Gulf of Suez can support and propagate positive storm surges, they do not occur, mainly because the winds from the prevailing weather systems are conducive to generate negative surges. Since the tidal range in the Gulf of Suez is small, even the combined water level from the surge and tide remains mostly negative.

The explosion of the ammunition ship Mont Blanc in Halifax Harbor produced a strong tsunami locally. There was not an operational tide gauge at the time to document the changes in sea level, but there are several narrative reports of extreme high and low water. In this study we examine the tsunami by looking at integrating three different aspects. We have collected narrative reports to see what quantitative information might be obtained from them. We have estimated the height of the initial mound of water that would be produced from an explosion of 2.9 kilotons in the harbor narrows where the Mont Blanc grounded. Finally, we have formulated a numerical model to follow the progress of the wave through the harbor, into Bedford Basin and out toward the Atlantic Ocean. Various analytical, empirical, and numerical models on explosion‐generated waves provide an estimate for the tsunami amplitude as a function of the explosive charge and limited by the water depth. For the Halifax explosion, the tsunami...

A two‐dimensional time‐dependent nonlinear tidal model was developed for the St. Lawrence estuary, with two open boundaries. This model is a substantial improvement over two earlier models which did not include the nonlinear terms. The model is run simultaneously, to hindcast the tide on any particular day, using as boundary conditions real data for the five important constituents, namely M2, S2, N2, K1, and O1. Coamplitude and cophase diagrams were constructed and compared with known shore‐based gauge observation. This comparison revealed that the model performs quite satisfactory. Further calibration was then carried out by adjusting the bottom friction coefficient. Such a calibration is necessary before the model can be used to simulate tsunami generation and propagation in the estuary. The total water level during the occurrence of a tsunami should include not only the tsunami amplitude, but also the interaction of the tsunami with the tide.

An earthquake occurred off the west coast of Nicaragua at 18 h 16 m on September 1, 1992. Despite a relatively modest magnitude (Ms = 7.0 Mw = 7.6), the earthquake generated a significant tsunami, which strongly impacted the coast of Nicaragua and was felt at several remote stations. In an attempt to better understand the tsunami propagation and coastal impact, we conducted a field survey on November 2–7, 1992, i.e., roughly 2 months after the event. We emphasized the observation of run‐up and inundation, but also collected a limited number of sand samples and mud cores. A total of 12 sites were surveyed, with multiple stations per site. This article presents the results of the survey, including a detailed discussion of the observation methods and data processing strategies. Observed run‐ups (relative to MSL) were typically in the 4–7 m range, with a maximum run‐up of 9.1 m at San Martin, an open coast site with a steep beach slope. Inundation extents were relatively modest, typically of the orde...

Sea level records from nine stations in eastern Canada have been analyzed in order to investigate the seasonal trends and other long‐term changes that have occurred since the beginning of this century. The four stations situated in riverine or estuarine regions are significantly affected by freshwater flow in their annual cycle of sea level changes and exhibit a definite maximum in spring and minimum in autumnwinter. Other stations situated in the eastern half of the Gulf of St. Lawrence or near the open Atlantic coast follow the general cycle of subarctic regions, with a low in spring‐summer and a high in autumn‐winter. Such seasonal variations appear to be related to the atmospheric pressure and baroclinic current variations. Secular trends in mean sea level show a mean rise of about 25.6 cm/century along the Atlantic coast of Canada. The monthly mean sea level series are subjected to Fourier spectral analysis in an attempt to identify the major long‐period cycles present in the records. The sp...

A vertically integrated tidal model of Barkley Sound has been developed as the first phase of a study of circulation and its interaction with juvenile salmon moving through Alberni Inlet and Barkley Sound to the Pacific Ocean. This model is an implementation of the three‐dimensional baroclinic model GF8 using a single layer, with a horizontal grid size of 400 m. Elevations and velocity boundary condition data for this model were obtained from an irregular grid finite element model of the west coast of Vancouver Island. The resulting barotropic tidal model was found to be stable, and produced tidal elevations in close agreement with observations. Modeled tidal currents at the location of a current meter morred in Imperial Eagle Channel agreed well with observations, to the extent that barotropic currents could be deduced in a simple manner from observations containing both barotropic and baroclinic modes. The next phase in the modeling program was the development of an upper layer baroclinic model...

In the past, sea level changes in the Indian Ocean received much less attention than those in the Atlantic and Pacific oceans. Here the sea level variation in the western part of the Indian Ocean has been considered. Rather than concentrating on the yet unproven, slow, and gradual sea level rise due to the so‐called greenhouse warming, attention is paid to the much more dramatic sea level variations that can occur within a few hours due to storm surges and tsunamis. In that part of the western Indian Ocean that is considered here, the storm surges are generated from the sea level atmospheric pressure fields and tangential surface wind stresses associated with travelling weather systems such as tropical cyclones. One can adapt the results from tsunami runup studies to storm surges since both phenomena fall into the classification of long gravity waves.

Marine positioning is relevant for several aspects of tsunami research, observation, and prediction. These include accurate positioning of instruments on the ocean bottom for determining the deep‐water signature of the tsunami, seismic observational setups to measure the earthquake parameters, equipment to determine the tsunami characteristics during the propagation phase, and instruments to map the vertical uplift and subsidence that occurs during a dip‐slip earthquake. In the accurate calculation of coastal tsunami run‐up through numerical models, accurate bathymetry is needed, not only near the coast (for tsunami run‐up) but also in the deep ocean (for tsunami generation and propagation). If the bathymetry is wrong in the source region, errors will accumulate and will render the numerical calculations inaccurate. Without correct and detailed run‐up values on the various coastlines, tsunami prediction for actual events will lead to false alarms and loss of public confidence.

Canada has increased the number of tsunami warning stations on the Pacific Coast from two to three. The last gauge was installed at the north end of Vancouver Island, thereby filling a large gap previously existing and providing full coverage along the coast. The record of gauges at two of the three locations is accessible either by telephone or by means of meteor burst communication, alleviating the difficulties experienced during the tsunami threat of May 6, 1986, when telephone communications were disrupted by heavy use. The gauge at Langara Island will be relocated in a more accessible and also a more tsunami‐responsive location at Rennell Sound in the Queen Charlotte Islands. All tsunami gauges also serve as tide gauges, recording the water level every 15 min. In the event of a tsunami, the recording interval can be altered to every 60 s. Suggestions have been made that Canada attempt deep‐sea recording of tsunamis off its Pacific Coast. Although this would be of great scientific value, no s...

The Boussinesq equations are supposed to be superior to the shallow water equations for use in the computations of tsunami travel, because they contain additional terms to account for dispersion. However, it is shown here that in real situations, the superiority of the Boussinesq system is not always apparent.

Marine geodetic processes are occurring on the west coast of Canada, as in other places on the globe, with a wide range of time scales. To understand the causative forces, various geological, oceanographic, and ocean‐atmosphere interaction problems have to be considered. In this brief review, the effects of tides, storm surges, tsunamis, and increases in atmospheric and ocean temperatures due to atmospheric carbon dioxide buildup are considered.

Maximum tsunami amplitudes that will result from major earthquakes on the outer coast of the Pacific Northwest region of North America were considered in Part 1 (Marine Geodesy 13(2):101–146). Here the tsunami threat for the inner coast is considered by developing a numerical model for the system consisting of the Strait of Georgia, Juan de Fuca Strait, and Puget Sound (GFP model). Three different source areas were considered for the outer coast models, and the resulting tsunami was propagated to the entrance of Juan de Fuca Strait. Using the output from the outer models, the GFP model was run. The results showed that whereas large tsunami amplitudes can occur on the outer coast, inside the GFP system, unless the earthquake occurs in the system itself, no major tsunami will result.

The semidiurnal L2 tide, in a model simulation of mixed tides in the straits of Georgia and Juan de Fuca, is the only tidal constituent with a nondegenerate amphidromic point in the system.

Tsunami research has suffered considerably due to the lack of an objective magnitude scale. The Imamura‐Iida Grade Scale, although it has been used until now as a magnitude scale, is not o...

The tsunami travel‐time charts that are presently in use by the Tsunami Warning Center were constructed originally in 1948 based on the hydrographic data available in the mid 1940s. Even the revised charts of 1971 made use of essentially the same data. It is shown here that the travel times deduced by these charts could be in error by as much as two hours in some cases. Even worse, the compiled travel times as deduced from these charts are generally greater than the observed travel times, which is a dangerous situation from a tsunami warning point of view.

The present knowledge on the influence of an ice layer on oceanic wave motion is reviewed. Whereas it is clear that short period wind waves are definitely damped by an ice layer, the extent of the influence of an ice cover on long waves is not clear. The observational as as well as the theoretical evidence on the influence of ice cover on the amplitudes of storm surges and on the propagation of tides and tsunamis is not clear enough to draw any definite conclusions.

Maximum tsunami amplitudes that will result from major earthquakes in the Pacific Northwest region of North America are considered. The modeled region encompasses the coastlines of British Columbia in Canada, and Washington and Oregon in the United States. Three separate models were developed for the outer coast and one model for the system consisting of the Strait of Georgia, Juan de Fuca Strait, and Puget Sound (GFP model) (Part 2). Three different source areas were considered for the outer coast models and the resulting tsunami was propagated to the entrance of Juan de Fuca Strait. Using the output from the other models, the GFP model was run. The results showed that large tsunami amplitudes can occur on the outer coast, whereas inside the GFP system, unless the earthquake occurs in the system itself, no major tsunami will result (Part 2).

Tidal flow patterns computed at various stages of the tide (high tide, falling tide, ebb tide, low tide, and flooding tide) and at different chronological stages (9000, 6000, 4500, 3000, and 2300 years B.P. and the present) using tidal numerical models were presented and interpreted in relation to sedimentary processes and the growth of the Fraser River delta during the past 9000 years. The overall tidal flows are least affected by the deltaic growth at high tide than at any other state of the tide. The net tidal flow with the overall northerly component has a sedimentary effect, in that there is an asymmetry in the transportation of silt and clay with more of these fine materials moved to the north of the delta than to the south. There is also independent seismic evidence for the existence of a tidal channel some 2000 B.P. between Point Roberts and the Fraser delta. This study attempted to link closely the sedimentary structure of the deltaic growth of the Fraser River with the physical oceanogr...

The propagation of tides in the Fraser River is discussed, with particular attention to the nonlinear interactions that characterize tides in such a system. The tidal regime is reviewed, and then the distortion of the tidal wave as it propagates upstream is discussed. The seasonal variation in tidal constituents can be related to the seasonally varying magnitude of the Fraser River discharge. The distortion in the tidal wave is related to the production of overtides through the nonlinear advective and friction terms. By considering the astronomical constituents of the tide, expressions are derived for the production of such overtides as the M4 and are quantitatively related to the relative magnitudes of tidal and mean velocity contributions.

The dynamics of tsunamis can be divided, for convenience, into three parts: tsunami generation, tsunami propagation, and the coastal problems. Out of these three, the problem of tsunami propagation is probably better understood than the other two. One of the main hindrances to the quantitative prediction of tsunami amplitudes at various coastal locations is a lack of detailed knowledge about the deep water signature of a tsunami. Here, the present understanding of this problem is discussed.

We comment on the statements that amphidromes in marginal seas with cooscillating tides in the Northern Hemisphere have anticlockwise rotation, of cotidal lines, and that rotation in the Southern Hemisphere will be clockwise.

A computer program has been developed to draw paleo‐continental maps for the period 190 million years ago to the present. The user has the option of specifying the projection and the scale. Maps can be drawn for the globe as a whole, for the northern hemisphere alone, and for the southern hemisphere alone, or indeed for any specified part of the globe. These paleo‐geographic maps are useful for the computation of paleo‐tides, paleo‐ocean circulation studies and climate.

In the recent seismological literature, several articles appeared which suggested that major earthquakes are likely to occur in the near future, in the various seismic gaps around the rim of the Pacific Basin. Although the direct effects of these earthquakes may be confined to local areas, the tsunamis that will generate are expected to travel Pacific Ocean wide and cause great destruction even at far off places around the Pacific Ocean. Here, the various approaches to delineating the tsunami hazard are discussed and some suggestions are made.