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The major (M w = 8.8) Chilean earthquake of 27 February 2010 generated a trans-oceanic tsunami that was observed throughout the Pacific Ocean. Waves associated with this event had features similar to those of the 1960 tsunami generated in the same region by the Great (M w = 9.5) 1960 Chilean Earthquake. Both tsunamis were clearly observed on the coast of British Columbia. The 1960 tsunami was measured by 17 analog pen-and-paper tide gauges, while the 2010 tsunami was measured by 11 modern digital coastal tide gauges, four NEPTUNE-Canada bottom pressure recorders located offshore from southern Vancouver Island, and two nearby open-ocean DART stations. The 2010 records were augmented by data from seven NOAA tide gauges on the coast of Washington State. This study examines the principal characteristics of the waves from the 2010 event (height, period, duration, and arrival and travel times) and compares these properties for the west coast of Canada with corresponding properties of the 1960 tsunami. Results show that the 2010 waves were approximately 3.5 times smaller than the 1960 waves and reached the British Columbia coast 1 h earlier. The maximum 2010 wave heights were observed at Port Alberni (98.4 cm) and Winter Harbour (68.3 cm); the observed periods ranged from 12 min at Port Hardy to 110–120 min at Prince Rupert and Port Alberni and 150 min at Bamfield. The open-ocean records had maximum wave heights of 6–11 cm and typical periods of 7 and 15 min. Coastal and open-ocean tsunami records revealed persistent oscillations that “rang” for 3–4 days. Tsunami energy occupied a broad band of periods from 3 to 300 min. Estimation of the inverse celerity vectors from cross-correlation analysis of the deep-sea tsunami records shows that the tsunami waves underwent refraction as they approached the coast of Vancouver Island with the direction of the incoming waves changing from an initial direction of 340° True to a direction of 15° True for the second train of waves that arrived 7 h later after possible reflection from the Marquesas and Hawaiian islands.

Eighteen papers are included in Volume 1 of a PAGEOPH topical issue Tsunamis in the World Ocean: Past, Present, and Future. These papers are briefly introduced. They are grouped into three categories: case studies of earthquake-generated tsunamis; tsunami forecast and hazard assessments; and theoretical and computational modeling of tsunami generation, propagation, and coastal behavior. Most of the papers were presented at the 24th International Tsunami Symposium held 14–16 July 2009 in Novosibirsk, Russia, and reflect the current state of tsunami science.

The catastrophic Indian Ocean tsunami generated off the coast of Sumatra on 26 December 2004 was recorded by a large number of tide gauges throughout the World Ocean. This study uses gauge records from 173 sites to examine the characteristics and energy decay of the tsunami waves from this event in the Indian, Atlantic and Pacific oceans. Findings reveal that the decay (e-folding) time of the tsunami wave energy within a given oceanic basin is not uniform, as previously reported, but depends on the absorption characteristics of the shelf adjacent to the coastal observation site and the time for the waves to reach the site from the source region. In general, the decay times for island and open-ocean bottom stations are found to be shorter than for coastal mainland stations. Decay times for the 2004 Sumatra tsunami ranged from about 13 h for islands in the Indian Ocean to 40–45 h for mainland stations in the North Pacific.

Currents in the northern Bay of La Paz were examined using an 8-month Acoustic Doppler Current Profiler (ADCP) record collected in the upper 185 m of the water column during 2007. Flow variability was dominated by tidal motions, which accounted for 43% (33% diurnal, 10% semidiurnal) of the total kinetic energy. The tidal motions had a pronounced vertical structure dominated within a shallow (∼30 m thick) surface layer by intense counterclockwise (CCW) rotary S 1 diurnal radiational currents that were highly coherent with the counterclockwise seabreeze. Motions within the semidiurnal frequency band were primarily associated with significant counterclockwise S 2 radiational tidal currents, which were also coherent with the seabreeze. Both S 1 and S 2 tidal ellipses in the upper layer were aligned perpendicular to the bay entrance with mean semi-major axes of 55 and 20 cm/s, respectively. Below the surface layer, tidal currents decayed rapidly to relatively weak, clockwise rotary barotropic motions. In contrast to those for radiational harmonics, tidal ellipses of the gravitational constituents (M 2 , K 1 and O 1 ) were oriented cross-bay. Energy within the diurnal frequency band in the surface layer was dominated by a coherent component (barotropic, phase-locked baroclinic and radiational), which accounted for roughly 65% (59% from S 1 alone) of the total diurnal kinetic energy. Of the remaining diurnal band energy, 18% was associated with an incoherent baroclinic component and 17% with a background noise component. Below 30 m depth, the corresponding estimates are 40%, 32% and 28%, respectively. The persistent, surface-intensified CCW rotary currents observed at the mooring site are assumed to be forced by strong CCW seabreeze winds in the presence of a “slippery” low-density surface layer. This response may be further augmented by topographic narrowing at the bay entrance and by the close proximity of the diurnal and inertial frequency bands in the region.

Semidiurnal tidal currents on the outer shelf of the Mackenzie Shelf in the Beaufort Sea were found to be strongly influenced by the locally generated baroclinic tide. Two primary factors are involved in this process: (1) the sharp shelf break along the northeastern Mackenzie Shelf, promoting the generation of vigorous internal tidal waves; and (2) the proximity to critical latitudes for M2 and N2 motions locking these waves and preventing them from leaving the source region. As a result, internal tides are resonantly trapped between the shelf and critical latitudes. The physical properties and temporal variations of tidal motions were examined using current meter measurements obtained from 1987–1988 at four sites (SS1, SS2, SS3, and SS4) offshore of the shelf break at depths of ∼200 m. Each mooring had Aanderaa RCM4s positioned at ∼35 m below the surface and ∼50 m above the bottom. Complex demodulation was used to compute the envelopes (amplitude modulation) of these components. A striking difference in the variability of clockwise (CW) and counterclockwise (CCW) tidal currents was found. The CW tides are highly variable, have greater amplitude, exhibit a burst-like character associated with wind events and contain about 80% of the total energy of the semidiurnal tidal currents. In contrast, the CCW components have a more regular temporal regime with distinct monthly, fortnightly and 10-day modulation at astronomical periodicities associated with frequency differences M2–N2 (0.03629 cpd), S2–M2 (0.06773 cpd), and S2–N2 (0.10402 cpd). Significant horizontal correlation of the CW current envelopes was found only between stations near the northeast Mackenzie Shelf, indicating this to be the main area of baroclinic internal wave generation.

Major earthquakes occurred in the region of the Central Kuril Islands on November 15, 2006 (Mw = 8.3) and January 13, 2007 (Mw = 8.1). These earthquakes generated strong tsunamis recorded throughout the entire Pacific Ocean. The first was the strongest trans-Pacific tsunami of the past 42 years (since the Alaska tsunami in 1964). The high probability of a strong earthquake (Mw ≥ 8.5) and associated destructive tsunami occurring in this region was predicted earlier. The most probable earthquake source region was investigated and possible scenarios for the tsunami generation were modeled. Investigations of the events that occurred on November 15, 2006, and January 13, 2007, enabled us to estimate the validity of the forecast and compare the parameters of the forecasted and observed earthquakes and tsunamis. In this paper, we discuss the concept of “seismic gaps,” which formed the basis for the forecast of these events, and put forward further assumptions about the expected seismic activity in the region. We investigate the efficiency of the tsunami warning services and estimate the statistical parameters for the observed tsunami waves that struck the Far Eastern coast of Russia and Northern Japan. The propagation and transformation of the 2006 and 2007 tsunamis are studied using numerical hydrodynamic modeling. The spatial characteristics of the two events are compared.

Tsunami-like sea level oscillations recently recorded by tide gauges located at offshore, as well as sheltered, sites along the coasts of British Columbia (Canada) and Washington State (USA) are identified as meteorological tsunamis. The events resemble seismically generated tsunamis but have an atmospheric, rather than seismic, origin. The event of 9 December 2005 was sufficiently strong to trigger an automatic tsunami alarm, while other events generated oscillations in several ports that were potentially strong enough to cause damage to marine craft. Analysis of coincident 1-min sea level data and high-frequency atmospheric pressure data confirms that the events originated with atmospheric pressure jumps and trains of atmospheric gravity waves with amplitudes of 1.5–3 hPa. The pronounced events of 13 July 2007 and 26 February 2008 are examined in detail. Findings reveal that the first atmospheric pressure event had a propagation speed of 24.7 m/s and an azimuth of 352°; the second event had a speed of 30.6 m/s and an azimuth of 60°. These speeds and directions are in close agreement with high-altitude geostrophic winds (the jet stream) indicating that the atmospheric disturbances generating the tsunami-like sea level oscillations are likely wind-transported perturbations rather than freely propagating atmospheric gravity waves.

Alberni Inlet is a long and narrow fjord adjacent to Barkley Sound on the Pacific Coast of Vancouver Island, Canada. Port Alberni, at the head of the inlet, was affected in 1964 by the largest Pacific tsunami waves in Canadian history. We use observations and results from two numerical models to investigate the resonant characteristics of the region and amplification of tsunami waves in Barkley Sound and Alberni Inlet. The first model (A) was forced at its open boundary with a stationary autoregressive signal, similar to the observed background noise. The second model (B) used an initial sea-level deformation from a potential earthquake off California in the southern segment of the Cascadia Subduction Zone, producing transient tsunami waves. Spectral, cross-spectral and frequency-time (f-t) analyses of the observations were used to examine the resonant properties and topographic response of the local area. The respective results show large admittance functions over a wide 0.5–0.9 cph frequency band, implying a low Q factor but high amplification of arriving waves. This unusual behavior is a result of two effects: A quarter-wave resonance of the system for its fundamental Helmholtz mode and amplification due to the narrowing of the channel cross section from Barkley Sound to Alberni Inlet. The model A numerical results agree favorably with the observations, indicating an energetic resonant mode at frequency of ~0.53 cph (112 min), with its nodal line located near the entrance to Barkley Sound and amplification factor value close to 12. The results from the tsunami propagation model (B) yield spectral characteristics similar to those from the model A and from the observations. The maximum tsunami current speed for this scenario is 2.4 ms-1 in Sproat Narrows, which divides Alberni Inlet into two parts, while the largest computed wave height is 1.6 m in the northern Alberni Inlet, in the area of Port Alberni.

This study presents analyses and numerical simulations of local tsunamis generated by two recent earthquakes off the coast of British Columbia. The Queen Charlotte Islands earthquake (Mw = 6.1) on 12 October 2001 generated waves that were recorded by tide gauges at Bamfield, Tofino, Winter Harbour and Port Hardy on the coast of Vancouver Island, with maximum measured wave heights of 11.3, 18.2, 22.7 and 14.5 cm, respectively. The Explorer Plate earthquake off Vancouver Island (Mw = 6.6) on 2 November 2004 generated waves recorded only at Bamfield and Tofino, with lower heights of 7.5 cm and 10.8 cm, respectively. The generation of tsunamis by these moderate, Mw = 6.1–6.6, local earthquakes suggests the possibility of destructive tsunamis from local sources other than the Cascadia Subduction Zone. This, in turn, has implications for tsunami hazards for this seismically active region of coastal North America.

On November 15, 2006, at 11:14 UTC, one of the strongest tsunamigenous earthquakes occurred near the Russian coast in the region of the Central Kuril Islands. Its magnitude was M w = 8.3, and the epicenter was located on the island slope of the deep Kuril–Kamchatka Trench 90 km southeast of Simushir Island (Fig. 1). The earthquake generated a tsunami that was manifested over the entire Pacific Ocean and was recorded with high accuracy by numerous coastal pressure gauges and by a large number of deep-water stations located in the open part of the ocean. The tsunami of 2006 became the strongest event of such type observed in the Pacific Ocean over the last 42 years (after the strongest Alaska tsunami in 1964). It occurred less than two years after the catastrophic December 26, 2004, earthquake and tsunami in the Indian Ocean, which caused unprecedented destruction and victims. However, it stimulated a drastic intensification in tsunami research [1, 2]. The November 15, 2006, earthquake and tsunami are unique because the possibility of their occurrence in the Central Kuril Islands region was predicted [1, 3, 4] and the possible scenarios of tsunami propagation were modeled [5, 6].

The authors describe a two-dimensional (vector) regressional model for examining the anisotropic response of ice drift and ocean current velocity (“drift velocity”) to surface wind forcing. Illustration of the method is limited to sea ice response. The principal mathematical and physical properties of the model are outlined, together with estimates of the “response matrices” and the corresponding “response ellipses” (drift velocity response to a unity wind velocity forcing). For each direction, φ, of the wind vector the method describes a corresponding “wind factor” α(φ) (relative drift speed) and “turning angle” θ(φ) (the angle between the drift velocity and wind vector). The major ellipse axis corresponds to the direction of the “effective wind” (φ = φmax) and the minor axis to the direction of the “noneffective” wind. The eigenvectors of the response matrix define wind directions that are the same as the wind-induced drift velocity directions. Depending on the water depth and offshore distance, six analytical cases are possible, ranging from rectilinear response ellipses near the coast to purely circular response ellipses in the open ocean. The model is used to examine ice drift along the western shelf of Sakhalin Island (Sea of Okhotsk). Responses derived from the vector regression (four parameter) method are less constrained and therefore more representative of wind-induced surface motions than those derived using the traditional complex transfer function (two parameter) approach.

The M w = 9.3 megathrust earthquake of December 26, 2004 off the northwest coast of Sumatra in the Indian Ocean generated a catastrophic tsunami that was recorded by a large number of tide gauges throughout the World Ocean. Part 1 of our study of this event examines tide gauge measurements from the Indian Ocean region, at sites located from a few hundred to several thousand kilometers from the source area. Statistical characteristics of the tsunami waves, including wave height, duration, and arrival time, are determined, along with spectral properties of the tsunami records.

A series of tsunami-like waves of non-seismic origin struck several southern European countries during the period of 23 to 27 June 2014. The event caused considerable damage from Spain to Ukraine. Here, we show that these waves were long-period ocean oscillations known as meteorological tsunamis which are generated by intense small-scale air pressure disturbances. An unique atmospheric synoptic pattern was tracked propagating eastward over the Mediterranean and the Black seas in synchrony with onset times of observed tsunami waves. This pattern favoured generation and propagation of atmospheric gravity waves that induced pronounced tsunami-like waves through the Proudman resonance mechanism. This is the first documented case of a chain of destructive meteorological tsunamis occurring over a distance of thousands of kilometres. Our findings further demonstrate that these events represent potentially dangerous regional phenomena and should be included in tsunami warning systems.

An Mw = 7.2 earthquake occurred on 15 June 2005 (utc) seaward of northern California off the west coast of North America. Based on the earthquake location and source parameters, the West Coast and Alaska Tsunami Warning Center issued a tsunami warning for the region extending from the California‐Mexico border to northern Vancouver Island, British Columbia (the first tsunami warning for this region since the 1994 Mw = 8.2 Shikotan earthquake). Six tide gauges on the west coast recorded tsunami waves from this event, with a maximum trough‐to‐crest wave height of 27.7 cm observed at Crescent City, California. Waves of 2.5 to 6.5 cm were measured at the five other sites: Port Orford (Oregon), North Spit and Arena Cove (California), and Tofino and Bamfield (British Columbia). The open‐ocean Deep‐ocean Assessment and Reporting of Tsunami (DART) buoys, 46404 and 46405, recorded tsunami waves of 0.5 and 1.5 cm, respectively, closely matching wave heights derived from numerical models. Incoming tsunami wa...

Analysis of sea-level data obtained from the Atlantic Global Sea Level Observing System (GLOSS) sea-level station at Takoradi, Ghana, West Africa, clearly reveals a tsunami signal associated with the Mw = 9.3 Sumatra earthquake of 26 December 2004 in the Indian Ocean. The tsunami arrived at this location on 27 December 2004 at approximately 01:38 UTC (which is close to the expected tsunami arrival time at that site), after travelling for more than 24 hours. The first wave was negative (trough), in contrast with the South African stations where the first wave was mainly positive (crest). The dominant observed period at Takoradi was about 42 minutes. The maximum trough-to-crest wave height (41cm) was observed on 28 December at 00:15 UTC. There were two distinct tsunami ‘bursts', separated in time by about 14 hours, the larger being the second burst. A small residual lowering of the sea level (~15cm) during the tsunami and for several days afterwards, and a delayed (~4.5 days) lowering of seawater temperature (up to ~4.5&#176C), was observed, possibly indicating the presence of internal waves through the Gulf of Guinea associated with propagating tsunami waves. The prominent tsunami signal found in the Takoradi record suggests that tsunami waves could also be found at other sites off the West African coast. Keywords: Atlantic Ocean, focusing, Ghana, GLOSS, Gulf of Guinea, internal wave, reflection, sea-level changes, tide gauge, tsunami wave, West AfricaAfrican Journal of Marine Science 2006, 28(3&4): 705–712

The Mw=9.3 megathrust earthquake of December 26, 2004 off the coast of Sumatra in the Indian Ocean generated a catastrophic tsunami that caused widespread damage in coastal areas and left more than 226,000 people dead or missing. The Sumatra tsunami was accurately recorded by a large number of tide gauges throughout the world's oceans. This paper examines the amplitudes, frequencies and wave train structure of tsunami waves recorded by tide gauges located more than 20,000 km from the source area along the Pacific and Atlantic coasts of North America.

The lattice-gas model in the quasi-chemical approximation (QCA) was used for adsorption isotherms and heats of adsorption calculations. The theory considers the surface topography, taking into account the atomic surface structure and the occupancy correlation of different adsorption sites. A comparison between Monte-Carlo and QCA simulations of the adsorption isotherms for argon atoms on three faces (1 1 0), (1 0 0) and (1 0 1) of rutile shows that both techniques give rather similar results with the advantage of QCA calculations being performed in a fraction of the time necessary for the Monte-Carlo simulation.

Data for tsunamigenic earthquakes and observed tsunami run-up are used to estimate tsunami-risk for the coasts of Peru and northern Chile for zones bounded by 5–35° S latitude. Tsunamigenic earthquake estimates yield magnitudes of 8.52, 8.64, and 8.73 for recurrence periods of 50, 100, and 200 years, respectively. Based on three different empirical relations between earthquake magnitudes and tsunamis, we estimate expected tsunami wave heights for various return periods. The average heights were 11.2 m (50 years), 13.7 m (100 years), and 15.9 m (200 years), while the maximum height values (obtained by Iida’s method) were: 13.9, 17.3, and 20.4 m, respectively. Both the “averaged” and “maximum” seismological estimates of tsunami wave heights for this region are significantly smaller than the actually observed tsunami run-up of 24–28 m, for the major events of 1586, 1724, 1746, 1835, and 1877. Based directly on tsunami run-up data, we estimate tsunami wave heights of 13 m for a 50-year return period and 25 m for a 100-year return period. According to the “seismic gap” theory, we can expect that the next strong earthquake and tsunami will occur between 19 and 28° S in the vicinity of northern Chile.

On November 18, 1929, a M=7.2 earthquake occurred at the southern edge of the Grand Banks, 280 km south of Newfoundland. The earthquake triggered a large submarine slope failure (200 km 3 ), which was transformed into a turbidity current carrying mud and sand eastward up to 1000 km at estimated speeds of about 60–100 km/h, breaking 12 telegraph cables. The tsunami generated by this failure killed 28 people, making it the most catastrophic tsunami in Canadian history. Tsunami waves also were observed along other parts of the Atlantic coast of Canada and the United States. Waves crossing the Atlantic were recorded on the coasts of Portugal and the Azores Islands. Tsunami waves had amplitudes of 3–8 m and runup of up to 13 m along the coast of the Burin Peninsula (Newfoundland). To simulate the slide-generated tsunami from this event, our initial analysis uses a shallow-water model; the slide was assumed to be a viscous, incompressible fluid layer; water was inviscid and incompressible. The preliminary results of the numerical modeling are encouraging, with computed and observed tsunami arrival times in reasonable agreement. D 2004 Elsevier B.V. All rights reserved.

Ice-drift velocity records from coastal radar stations, combined with data from moored current meters and coastal wind stations, are used to examine sea-ice motion off the northeastern coast of Sakhalin Island in the Sea of Okhotsk. Ice motion is shown to be governed primarily by diurnal tidal currents and wind-induced drift, which explain 92%–95% of the total ice-drift variance. Diurnal tidal motions predominate off the northern Sakhalin coast, accounting for 65%–80% of the variance, while low-frequency wind-induced motions prevail off the south-central coast, accounting for over 91% of the ice-drift variance. Maximum diurnal tidal ice-drift velocities range from 90–110 cm s−1 on the north coast to 10–15 cm s−1 on the south coast, in good agreement with the barotropic model of Kowalik and Polyakov. The presence of diurnal shelf waves accounts for the strong diurnal currents on the steeply sloping northern Sakhalin shelf, while the absence of such waves explains the weak diurnal currents on the more gently sloping south-central shelf. Using a vector regression model, the authors show that wind-induced ice-drift “response ellipses” (the current velocity response to a unity wind-velocity forcing) are consistent with a predominantly alongshore response to the wind, with wind-induced currents most pronounced off the south-central coast where water depths are relatively shallow. Time–frequency analysis of wind and ice-drift series reveals that, in winter, when sea ice is most extensive and internally cohesive, the ice response is almost entirely aligned with the alongshore component of the wind; in spring, when sea ice is broken and patchy, the ice responds to both the cross- and alongshore components of the wind.

A few years ago the Canadian Hydrographic Service initiated a major upgrade toall tide gauges and tsunami stations on the coast of British Columbia (B.C.). Thisprogram was undertaken to address shortcomings of the earlier digital systems andwas driven by concerns about emergency response continuity in the year 2000. By1999, thirteen tide gauge stations had been installed and were operational. Three ofthese stations (Tofino, Winter Harbour, and Langara) were selected for use as tsunamiwarning stations. Several years of continuous, high quality data have now been collectedat these stations and used for analysis of long waves in the tsunami frequency band.Careful examination of these data revealed two weak tsunamis recorded by severalB.C. stations: a distant tsunami of June 23, 2001 generated by the Peru Earthquake(Mw = 8.4), and a local tsunami of October 12, 2001 induced by the Queen Charlotte Earthquake (Mw = 6.3$). Spectral characteristics of these two tsunamis are compared with the spectral characteristics of long waves generated by a strong storm (October, 2000) and of ordinary background oscillations. The topographic admittance functions (frequency responses) constructed for all stations showed that most of them (in particular, Winter Harbour, Tofino, Bamfield, Port Hardy, and Victoria) have strong resonance at periods from 2.5 to 20 min, indicating that these locations are vulnerable to relatively high-frequency tsunamis. The Winter Harbour station also has two strong resonant peaks with periods of 30 and 47 min and with amplification factors of about 7. The estimated source functions show very clear differences between long waves associated with the seismic source (typical periods 10–30 min) and those generated by a storm, which typically have shorter periods and strong energy pumping from high-frequencies due to non-linear interaction of wind waves.

A modified and corrected version of the viscous slide model of JIANG and LEBLOND (1994) is used to assess the tsunami risk associated with hypothetical underwater slope failures in two coastal areas of British Columbia having potentially unstable sediment deposits: (a) Malaspina Strait, separating the mainland coast and Texada Island in the central Strait of Georgia; and (b) Roberts Bank on the foreslope of the Fraser River Delta in the southern Strait of Georgia. The intent of this study is to demonstrate the capability of the model for tsunami risk assessment and to improve upon previous studies of tsunami risk in the region based on reasonable submarine landslide scenarios. The potential risk from tsunamis associated with slide failures has been examined, but the likelihood of failure events themselves was not considered. For the Malaspina Strait scenarios, simulated tsunamis are generated by failure of a lobe of perched sediment situated on the slope of eastern Texada Island. Failure as a flow slide of the estimated 1,250,000 m 3 of sediment generates wave troughs reaching � 4:9 m and trough-to-crest heights of 6 to 8 m along the coast of Texada Island. At Cape Cockburn, on the opposite side of the strait, wave heights of 1.5 to 2.0 m are produced. For Roberts Bank, simulated waves are examined for two separate failure scenarios. The larger slide (Case 1) involves the failure of a sediment lobe with lateral dimensions of 7 · 3k m 2 and volume of 0.75 km 3 while the smaller slide (Case 2) fails a sediment lobe with dimensions of 4 · 2.6 km 2 and volume of 0.23 km 3 . Computations were made both for high (+3 m) and low (� 3 m) tide conditions. For both failure volumes, maximum wave amplitudes (up to 18 m for Case 1 and 8 m for Case 2) occur on the coasts of Mayne and Galiano Islands, opposite the source area. Wave amplitudes are much smaller (1 to 4 m) on the mainland coast because of the reflection of the initial waves from Roberts Bank. Additional numerical experiments were conducted for both regions to estimate the sensitivity of the computed tsunami wave heights to input parameters, such as slide viscosity, bulk density, and slide position.

Hydrographic surveys and satellite imaging reveal that mesoscale anticyclonic (AC) eddies are common features of the area south of Bussol' Strait, the deepest of the Kuril straits connecting the western North Pacific and Sea of Okhotsk. To examine the velocity structure of these eddies, we deployed groups of 15-m drogued satellite-tracked surface drifters over the Kuril-Kamchatka Trench in the fall of 1990 and late summer of 1993. Drifters in both groups entered large AC eddies centered over the axis of the trench seaward of Bussol' Strait and subsequently underwent a slow northeastward translation. One drifter (Drifter 1315) deployed near the center of the “Bussol' eddy” in 1990, remained in the eddy for roughly 45 days and made five loops at successively greater distances from the eddy center. Large-amplitude (80–100 cm/s) storm-generated inertial oscillations were observed during the first two loops. The vorticity field associated with the eddy resulted in a Doppler “red-shift” of inertial frequency motions such that the “effective” inertial period of 21 hours was roughly 4 hours greater than the nominal inertial period for the drifter latitude (45°N). In 1993, a second drifter (Drifter 15371) was retained in the Bussol' eddy for about 40 days. This eddy had characteristics similar to those of the 1990 eddy but was devoid of significant high-frequency motions until the drifter's final half loop. The observed spatial scales, persistence, and slow poleward translation of the eddies suggests that they play an important role in the dynamics of the East Kamchatka and Oyashio current systems.

Collection of papers on meteorological tsunamis.

Tsunami-like intense sea-level oscillations, associated with atmospheric activity (meteorological tsunamis), are common in the Great Lakes and on the East Coast of the United States. They are generated by various types of atmospheric disturbances including hurricanes, frontal passages, tornados, trains of atmospheric gravity waves, and derechos. “Derecho” is a rapidly moving line of convectively induced intense thunder storm fronts producing widespread damaging winds and squalls. The derecho of June 29–30, 2012 devastatingly propagated from western Iowa to the Atlantic coast, passing more than 1, 000 km and producing wind gusts up to 35 m/s. This derecho induced pronounced seiche oscillations in Lake Michigan, Chesapeake Bay, and along the US Atlantic coast. Sea-level records from the updated National Oceanic and Atmospheric Administration (NOAA) tide gauge network, together with the NOAA and automated surface-observing system air pressure and wind records, enabled us to examine physical properties and temporal/spatial variations of the generated waves. Our findings indicate that the generation mechanisms of extreme seiches in the basins under study are significantly different: energetic winds play the main role in seiche formation in Chesapeake Bay ; atmospheric pressure disturbances are most important for the Atlantic coast ; and the combined effect of pressure oscillations and wind is responsible for pronounced events in the Great Lakes. The “generation coefficient, ” which is the ratio of the maximum observed sea-level height and the height of air pressure disturbance, was used to map the sea-level response and to identify “hot spots” for this particular event, i.e., harbors and bays with amplified seiche oscillations. The Froude number, Fr = U/c, where U is the speed of the atmospheric disturbance and c is the long-wave speed, is the key parameter influencing the water response to specific atmospheric disturbances ; the maximum response was found for those regions and disturbance parameters for which Fr ~1.0.

Satellite-tracked surface drifters deployed in September 1993 in the vicinity of the Kuril–Kamchatka Trench were advected onto the Pacific continental shelf of the Kuril Islands where they encountered strong (40–50 cm s−1) diurnal tidal currents. One of the drifters subsequently passed through Friz Strait into the Sea of Okhotsk, experiencing intense (>100 cm s−1) diurnal currents in the strait and strong (35–40 cm s−1) diurnal currents over the Okhotsk shelf of the Kuril Islands. The across-shelf structure of the diurnal tidal currents is shown to be consistent with that of free, topographically trapped subinertial waves propagating along the continental margin of the islands. Of the three continental shelf wave models considered (a barotropic model with zero mean flow, a barotropic model with nonzero alongshore mean flow, and a baroclinic model based on the observed density structure), only the baroclinic model accurately explains the main features of the diurnal currents for the Pacific and Ok...

We use hourly sea level records from southern California to the Aleutian Islands to examine low-frequency variability in the northeast Pacific during the 1982–83 and 1997–98 El Nino events. Comparison between events is facilitated by long-term records for Yakutat, Tofino, Neah Bay, and San Francisco which appear to be representative of distinct coastal oceanic regimes. Residual (tide-removed) time series reveal that the anomalously high sea levels of the 1997–98 El Nino persisted from the spring of 1997 to the spring of 1998, and this event was more protracted than the 1982–83 El Nino. During both major events, the annual (Sa), semiannual (Ssa), and synoptic-scale sea level constituents were amplified relative to non-El Nino years, with synoptic fluctuations in sea level height and sea level pressure for mid-latitude sites Tofino and Neah Bay strongly correlated through the inverted barometer response. The spectral anomaly coefficient, SjR(ω)=[Rj(ω)−1]/[Rj(ω)+1] (where R j (ω)=S j / S j is the spectral ratio between the El Nino spectrum, Sj(ω), and the time-averaged non-El Nino spectrum, S(ω) j , for tide gauge site “j”) indicates that both events gave rise to enhanced sea level variability at periods of days to weeks because of passing atmospheric systems. However, the 1982–83 El Nino generated greater signal variance at seasonal-scales (periods of months) while the 1997–98 El Nino generated greater variance at synoptic scales (periods of days). Findings further indicate that poleward oceanic propagation of the 1982–83 and 1997–98 events terminated near central California, and that much of the enhanced sea level variability observed at mid to high latitudes was associated with atmospheric teleconnection responses that gave rise to amplified variations in coastal sea level pressure and/or surface wind stress.

This investigation addresses the difficult problem of using a multi data set of water levels to study seich oscillations in the Baltic Sea. The Baltic Sea is a semi-enclosed sea area and is connected with the North Atlantic Ocean through the North Sea. The applied method is based on the analysis of environmentally corrected radar altimeter (RA) data in conjunction with simulated water levels obtained by an operational circulation model of the Federal Maritime and Hydrographic Agency (Bundesamt fur Seeschiffahrt und Hydrographie, BSH) and tide gauge data. RA data of the First European Remote Sensing Satellite (ERS-1) have been analysed. The RA data were collected during the three-day repeat cycle from August 12 to December 9, 1991. An advantage of the analysis is the coverage and the geographical location of one and the same frequently repeated descending sub-satellite pass over the Bothnian Bay and the central Baltic Sea. Due to the assumed linear dynamics of this sea area the observation of sea level changes in the sense of a standing wave between the Bothnian Bay and the Baltic Proper is investigated. Amplitudes of water level changes up to 1 m have been recorded at tide gauge stations in the northern and southern parts of the Baltic Sea, respectively, during August and December 1991. Water level changes of less than 20 cm were calculated from the corrected altimeter data during the overflights of ERS-1. Tide gauge data and water level differences of tide gauge data measured at Kemi (Bothnian Bay), Finland, and Kolobrzeg at the Polish coast were used for frequency analyses. The analysed time series have been limited to five months due to the duration of the three-day repeat cycle of ERS-1. For frequency analysis the given sampling interval of 4 h is not appropriate, but a period of 12.4 h was clearly identified. This period corresponds to the fourth mode of theoretical estimated ones. The differences of water levels of the simulated data between Kemi and Kolobrzeg of about 25 cm agree fairly well with the results obtained by the RA data. Due to these results and the synoptic view of the along-track subsatellite passes it turned out that seiches can be observed by the ERS-1 radar altimeter.

In light of the recent enhanced activity in the study of tsunami waves and their source mechanisms, we consider tsunami-like waves that are induced by atmospheric processes rather than by seismic sources. These waves are mainly associated with atmospheric gravity waves, pressure jumps, frontal passages, squalls and other types of atmospheric disturbances, which normally generate barotropic ocean waves in the open ocean and amplify them near the coast through specific resonance mechanisms (Proudman, Greenspan, shelf, harbour). The main purpose of the present study is to describe this hazardous phenomenon, to show similarities and differences between seismic and meteorological tsunamis and to provide an overview of meteorological tsunamis in the World Ocean. It is shown that tsunamis and meteotsunamis have the same periods, same spatial scales, similar physical properties and affect the coast in a comparably destructive way. Some specific features of meteotsunamis make them akin to landslide-generated tsunamis. The generation efficiency of both phenomena depend on the Froude number (Fr), with resonance taking place when Fr~1.0. Meteotsunamis are much less energetic than seismic tsunamis and that is why they are always local, while seismic tsunamis can have globally destructive effects. Destructive meteotsunamis are always the result of a combination of several resonant factors; the low probability of such a combination is the main reason why major meteotsunamis are infrequent and observed only at some specific locations in the ocean.

Statistics of the near-surface circulation in the northeast Pacific Ocean were derived from the trajectories of nearly 100 surface drifters tracked between August 1990 and December 1995 as part of the World Ocean Circulation Experiment's (WOCE) Surface Velocity Program (SVP). Drifters were drogued within the mixed layer (15 m drogue depth) or near the top of the permanent halocline (120 m). All branches of the Alaskan Gyre were well-sampled at both depths, revealing a weak Subarctic Current, a bifurcation of the Subarctic Current near 48°N, 130°W at 15 m depth, and strong, variable flow in the Alaska Current and Alaskan Stream. At 120 m depth, northward flow in the Alaska Current occurred much farther offshore than within the mixed layer. The drifter trajectories revealed interannual variability, with evidence of an intensified Alaskan Gyre during the winters of 1991–92 and 1992–93 and more southerly transport during winter 1994–95. A minimum in eddy kinetic energy was found at both depths within the northern branch of the Subtropical Gyre. Eddy kinetic energies were nearly twice as high in the mixed layer compared to below, and were 2–3 times larger in winter than in summer throughout most of the near-surface Alaskan Gyre. High eddy energies observed near the eastern perimeter of the Alaskan Gyre may be due to the offshore intrusion of eddies formed by coastal current instabilities. Taylor's theory of single-particle dispersion was applied to the drifter ensembles to estimate Lagrangian decorrelation scales and eddy diffusivities. Both the initial dispersion and random walk regimes were identified in the dispersion time series computed for several regions of both ensembles. The integral time scales and eddy diffusivities computed from the dispersion scale linearly with r.m.s. velocity, which is consistent with drifter studies from the Atlantic. An exception is the meridional integral time scales, which were nearly constant throughout the study area and at both drogue depths. The magnitudes of the derived eddy statistics are comparable to those derived from surface drifters in other parts of the world ocean. These are the first Lagrangian estimates of particle dispersion over a broad region of the near-surface North Pacific, and the consistency of the results with previous studies from the Atlantic lends credence to the idea that the simplifying assumptions of Taylor (1921) (Proceedings of the London Mathematical Society Series A 20, 196–221) are reasonably valid throughout the upper ocean. This bodes well for the effective parameterization of near-surface diffusivities in general circulation models. Finally, the drifter-derived velocity statistics were used to speculate on the source regions of waters of possible coastal origin observed at offshore stations during the field studies of the Canadian Joint Global Ocean Flux Study.

We examine the origin and behavior of the catastrophic tsunami that impacted Skagway Harbor at the head of Taiya Inlet, Alaska, on November 3, 1994. Geomorphologic and tide gauge data, combined with numerical simulation of the event, reveal that the tsunami was generated by an underwater landslide formed during the collapse of a cruise-ship dock undergoing construction. Use of a fine-grid model for Skagway Harbor and a coarse-grid model for Taiya Inlet enables us to explain many of the eyewitness accounts and to reproduce the dominant oscillations in the tide gauge record, including the persistent (∼1 h) 3-min oscillation in Skagway Harbor. The occurrence of the landslide is linked to critical overloading of the slope materials at a time of extreme low tide.

The effects of reduced sampling schedules (duty cycles) on velocity statistics derived from satellite-tracked drifters in the northeast Pacific Ocean are investigated. Continuous segments of the drifter records (in which all available satellite positions fixes are recorded and processed by Service ARGOS) are degraded to match the standard duty cycle used in the World Ocean Circulation Experiment–Surface Velocity Program, in which there are 48 h of no data transmission followed by 24 h of received transmission (48–24 h). Also examined are duty cycles of 32–16 h and 16–8 h. It is found that the strong inertial motions prevalent in the drifter records result in significantly biased statistics derived from the degraded series. Reproduction of the original prime (mean and standard deviation) and rotary spectral statistics requires an interpolation that takes into account the oscillatory component of the drifter motions. Duty cycles having shorter but more frequent gaps (e.g., 16–8 h) are not sufficien...

Observational evidence is presented for pervasive nonlinear interaction between inertial and M 2 frequency oscillations in the northeast Pacific. Enhanced currents at the sum frequency (termed the fM 2 frequency) have the rotary spectral properties of freely propagating waves suggesting permanent energy exchange from the inertial and semidiurnal bands to the fM 2 band. The interaction may be responsible for the greater than predicted decay of inertial energy observed in the ocean and may contribute significantly to oceanic mixing.

We examine current variability in the open northeast Pacific using 3-hourly sampled trajectories from satellite-tracked drifters drogued at depths of 15 and 120 m within the wind-mixed layer and permanent pycnocline, respectively. Findings show the following. (1) Motions were dominated by inertial currents which accounted for 58% (35%) of the total variance measured by the shallow (deep) drifters. Semidiurnal motions accounted for roughly 10% of the variance at both depths. There were detectable currents at twice the inertial frequency (2f ≈ 3 cpd) and negligible diurnal currents. (2) Inertial currents attained root-mean-square (rms) speeds of around 50 cm/s in the mixed layer and 10 cm/s in the pycnocline. Speeds in the semidiurnal band were similar (≈10 cm/s) at both depths. (3) Inertial and semidiurnal currents were strongly clockwise rotary, while low-frequency currents ( 0.95] occurred for drifter separations Δr 500 km. Semidiurnal currents were uncorrelated beyond several tens of kilometers. (6) Inertial currents appear to be linked to the passage of atmospheric lows, and semidiurnal currents to the passage of remotely generated baroclinic tides. The spectral peak near 2f is indicative of nonlinear inertial wave interactions.

Extreme atmosphere-induced seiche oscillations occasionally occur in specific inlets and bays of the world ocean causing severe damage to coastal areas, ships and port constructions. Ciu- tadella inlet (Menorca Island, Western Mediterranean) can be singled out as a place where such large seiches, locally known as rissaga, are quite common. Similar (although weaker) oscillations are also regularly observed in bays of Shikotan Island (South Kuril Islands, northwestern Pacific). Several spectacular events in these regions, identified in the first part of this study (Rabinovich and Monserrat, 1996), are analysed to determine the atmospheric parameters responsible for the generation of large- amplitude seiches. Their generation mechanism was shown to be quite different from that causing ordinary background oscillations. Coincidence of some external factors and certain resonance effects seem to be necessary to produce the destructive waves. In particular, rissaga waves in Ciutadella inlet were found to be related to significant atmospheric disturbances propagating from the southwest, coinciding with the orientation of the inlet, and having a phase speed of about 30 m/s, which is close to the phase speed of long waves offshore from Menorca. Pronounced resonant properties of the inner basin strongly amplify incoming waves in Ciutadella inlet. In contrast, the bays of the northwestern coast of Shikotan Island are protected from normally incident atmosphere-induced waves by the elongated Kunashir Island, hence the whole situation there is not so favorable for the excitation of large seiches.

The catastrophic Ligurian Earthquake on February 23, 1887 caused significant damage and numerous casualties in northwestern Italy and southeastern France. The first (main) shock (estimated magnitude of 6.2–6.5) produced tsunami waves observed along 250 km of the Ligurian coast from Genoa to Cannes. Typical tsunami run-up heights were 1–2 m. The first wave was found to be negative, supporting the assumption that the earthquake was produced by release of stress along an offshore normal fault. Computed tsunami waveforms are in qualitative agreement with observed run-ups. Unique 1887 tsunami records in Genoa and Nice harbors were found and analyzed. Numerical computations of eigenoscillations for the old (1887) Genoa harbor were made and found to be in a good agreement with the tsunami observations. The dominant observed period of 22.5 min was shown to be related to the fundamental (Helmholtz) mode of the old port. Long “ringing” and slow decay of tsunami oscillations in Genoa are associated with “pumping” of wave energy from the external basin. Several wave trains are revealed in the record that occur at 2–2.5 h intervals. They are interpreted as edge waves propagating along the Ligurian shelf and reflecting from its borders.

A new approach is proposed to separate the influence of source and topography in observed tsunami spectra and to reconstruct the initial source spectrum. The method assumes a linear tide gauge response to external forcing and is based on comparative analysis of tsunami and background spectra. Evaluation of the ratio of tsunami to background spectra gives functional characteristics that are invariant of station location and dependent only on the source parameters. Three events, the Urup tsunami of December 22, 1991 (northwest Pacific), the Hokkaido Southwest (Okushiri) tsunami of July 12, 1993 (Sea of Japan), and the Shikotan tsunami of October 4, 1994 (northwest Pacific), are used as examples of the proposed approach. The source spectra reconstructed from the analysis of different tide gauges were found to be in good agreement with each other and with the seismological, geodetic, and field survey data.

Satellite-tracked drifters were used to examine eddy activity in the vicinity of the Emperor Seamount Chain (ESC) in the North Pacific during 1991–1993. The trajectories of two drifters drogued at a depth of 120 m revealed a pair of counterrotating mesoscale eddies attached to the leeside of Ojin/Jingu Seamount in the summer of 1992. The eddies had diameters of 75–100 km and rotational speeds of 20–40 cm/s at 120 m. Sea surface height anomalies derived from blended TOPEX/ERS-1 satellite altimetry revealed that the eddies had a surface manifestation as well. One of the drifters made five loops within the cyclonic eddy over a period of 62 days, during which time the eddy translated westward, toward the seamount, at 2.9 cm/s. This is one of the first observations demonstrating an extended attachment of a topographically generated eddy to a seamount. Drifters drogued at a depth of 15 m which crossed the ESC in the summer of 1991 and winter of 1993 revealed no eddy activity, most likely because of a decoupling of the topographic influence to the 15 m flow at their crossing latitude over the Nintoku Seamount (summit depth at 1000 m). The implication is that eddy formation within the mixed layer near the ESC is confined to the region around the taller Ojin/Jingu and Kinmei Seamounts (summit depths at 800 m and 100 m, respectively). It is suggested that long-lived eddies attached to the leeside of the ESC can profoundly influence local biological production and water exchange between the western and eastern basins of the North Pacific.

A near-surface satellite-tracked drifter launched off the east coast of the Kuril Islands on September 4,1993 began a 2.5-year Odyssey across the North Pacific Ocean. During its travels, the drifter encountered numerous energetic oceanographic regimes as it moved from the region of the Kuril-Kamchatka Trench to the continental margin of the Kuril Islands, through Friza Strait into the Sea of Okhotsk, seaward again through Bussol’ Strait, and then eastward across the North Pacific. Oceanic features detected along the basin-wide trajectory include a quasi-permanent anticyclonic eddy over the Kuril-Kamchatka Trench, open-ocean wind-driven inertial oscillations, coastal-trapped diurnal shelf waves, semidiurnal tidal currents, transient cyclonic and anticyclonic eddies, through-strait flows, and wave-like mesoscale meanders. The single drifter track delineates the dynamically-rich variability of upper ocean currents, emphasizes the marked difference in flow dynamics between boundary and open ocean regions, and provides a time-scale for the movement of surface waters across the entire North Pacific.

We show that the tsunami of November 3, 1994 in Skagway, Alaska was generated by an underwater landslide formed during the collapse of a cruise ship wharf undergoing construction at the head of Taiya Inlet. This event occurred at a time of extreme low tide and was not associated with a regional seismic event or incoming oceanic tsunami. Persistent wave motions with an amplitude of 1 m and a period of 3 min recorded by a tide gauge in Skagway Harbor following the landslide are linked to the formation of a cross-inlet seiche and quarter-wave resonance within the harbor. The high Q factor for the harbor (Q ≈ 20) indicates weak dissipation and strong resonance within the harbor.

[1] The 2004 Sumatra tsunami was clearly recorded by two UK bottom pressure gauges, DPN and DPS, deployed in Drake Passage between South America and Antarctica. These open-ocean records were examined to estimate characteristics of the tsunami waves and to compare the results of numerical simulations with the observations. Maximum wave heights measured at these gauges were 4.9 cm at DPN and 7.4 cm at DPS; the travel times from the source area were 19 h 46 min and 19 h 39 min respectively, consistent with the times obtained from the nearby coastal tide gauges. The numerical model described well the frequency content, amplitudes and general structure of the observed waves, with only small time shifts probably related to wave dispersion effects. The shifts were 15 min for DPN and 10 min for DPS, with the modeled waves leading the observations in each case. Further inspection of the simulated and observed records revealed that the identified tsunami waves are related to the second (main) train of waves propagating by the energy conserving route along the mid-ocean ridges, while the first train of waves travelling by the fastest route across the ocean remained unrecognizable in the observed DPS and DPN records and undetectable in the records of coastal tide gauges because of their insignificant amplitudes compared to the background variability.

[1] As part of the NEPTUNE-Canada cabled seafloor observatory, an array of six high-precision bottom pressure recorders was installed in the late summer of 2009 at depths from 100 to 2600 m seaward of the southwest coast of Vancouver Island in the northeast Pacific. The instruments transmit 1-sec bottom pressure data at roughly 0.1 mm equivalent sea level height to the Data Management and Archiving System (DMAS) at the University of Victoria. On September 30, 2009, the array recorded waves of 2.5 to 6 cm amplitude associated with the transoceanic tsunami generated by the Mw = 8.1 Samoa earthquake in the South Pacific. These open-ocean observations were uncontaminated by coastal effects, demonstrating that NEPTUNE records from future tsunami events can be effectively used as realtime input to a regional numerical tsunami forecast model. We validate this proposition by showing that wave forms simulated by the regional model using the leading train of waves of the 2009 event are in good agreement with observed tsunami records for both the shelf stations and nearby coastal tide gauges. Tsunami waves simulated by this model are also significantly more accurate for local regions than those determined by global-scale tsunami models. This ability to assimilate “pristine” open-ocean data from the cabled observatory into an operational tsunami forecast model makes it possible to provide updated wave information that could help mitigate the impact of future tsunamis approaching the west coast of British Columbia and northern Washington State.

[1] We report unique deep-sea recordings of the Sumatra tsunami of December 2004 by high-resolution DART® (Deep-ocean Assessment and Reporting of Tsunami) and CORK (Circulation Obviation Retrofit Kit) bottom pressure sensors deployed at depths of ∼1500–3500 m in Cascadia Basin in the northeast Pacific. The simultaneous records from these sites establish the first-ever regional-scale tsunami detection array for the open ocean, enabling us to resolve both seafloor and crustal tsunami signals and to determine fundamental properties of the waves following their 22,000 km journey from the source region. Waves reaching the basin had mean amplitudes of ∼5 mm with energy spread over a broad frequency band from 0.4 to 7 cph. Peak tsunami energy was in the 0.8 to 2 cph (75 to 30 min) band. Leading waves from the event arrived 34–35 h after the earthquake, roughly 7 h later than expected, suggesting that the tsunami mainly propagated by the “most economic” (minimum energy loss) path along mid-ocean ridge wave-guides rather than taking the direct and fastest path across the ocean. Motions within the peak energy band comprise roughly 50% coherent progressive waves propagating from the south at longwave phase speeds of ∼150 ms−1 and 50% random waves scattered from the coast and bottom irregularities. Tsunami amplitudes in the borehole were one-third those on the seafloor. The extensive “ringing” and anomalously slow (3.5-day) e-folding decay time of the tsunami wave energy indicates long duration energy flux radiating from the Indian Ocean via the Southern Pacific Ocean.

[1] Bottom pressure measurements acquired from the TAG hydrothermal field on the Mid-Atlantic Ridge (26°N) contain clusters of narrowband spectral peaks centered at periods from 22 to 53.2 minutes. The strongest signal at 53.2 min corresponds to 13 mm of water depth variation. Smaller, but statistically significant, signals were also observed at periods of 22, 26.5, 33.4, and 37.7 min (1–4 mm amplitude). These kinds of signals have not previously been observed in the ocean, and they appear to represent vertical motion of the seafloor in response to hydrothermal flow - similar in many ways to periodic terrestrial geysers. We demonstrate that displacements of 13 mm can be produced by relatively small flow-induced pressures (several kPa) if the source region is less than ∼100 m below the seafloor. We suggest that the periodic nature of the signals results from a non-linear relationship between fluid pore pressure and crustal permeability.