Spread of oil from theTenyo Maru,off the Southwest coast of Vancouver Island

We provide background oceanography and observations and hindcast simulations of spreading oil leaked from the wreck of theTenyo Maru, a fishing vessel that sank off the western entrance to Juan de Fuca Strait in July 1991. The vessel sank in the region of the Tully Eddy on the continental shelf. Although this eddy is normally present in summer, its location shifts and its trapping time varies considerably. The spread of theTenyo Maru oil is represented reasonably well by assuming the eddy to be a littler further to the east and north of its position as observed during drifter studies in 1986. Observations in 1985 showed that the preferred exit route of surface water from the eddy was toward the southeast, the direction followed by theTenyo Maru oil in 1991; however, other drift paths are possible, and under different weather conditions the oil could have drifted toward the Vancouver Island coast.     

Thinner Sea Ice Contribution to the Remarkable Polynya Formation North of Greenland in August 2018

In August 2018, a remarkable polynya was observed off the north coast of Greenland, a perennial ice zone where thick sea ice cover persists. In order to investigate the formation process of this polynya, satellite observations, a coupled iceocean model, ocean profiling data, and atmosphere reanalysis data were applied. We found that the thinnest sea ice cover in August since 1978(mean value of 1.1 m, compared to the average value of 2.8 m during 1978-2017) and the modest southerly wind caused by a positive North Atlantic Oscillation(mean value of 0.82, compared to the climatological value of-0.02) were responsible for the formation and maintenance of this polynya. The opening mechanism of this polynya differs from the one formed in February 2018 in the same area caused by persistent anomalously high wind. Sea ice drift patterns have become more responsive to the atmospheric forcing due to thinning of sea ice cover in this region.     

Random walk of the Earth's pole related to the Chandler wobble excitation

Summary. The equation governing the polar motion shows that the polar secular drift and the Chandler wobble amplitude are related to each other. In particular, a drift of the mean pole position comes out as a consequence of the maintenance of the Chandler wobble by possible step perturbations of the Earth's inertia tensor.
The minimum excitation functions necessary to explain the Chandler wobble amplitude variations for the period 1901–84 are derived from the Chandler term, with the hypothesis that the excitations follow a uniform random distribution in time. It is shown that they have the statistical properties of the steps of a two-dimensional random walk. These functions are then used to derive, from a statistical simulation, a lower limit of the secular drift which may result from the excitation of the Chandler wobble.
The drift generated by the random walk is of the same order of magnitude as the observed secular drift for the period 1901–84, but their time dependence is different. This indicates that the observed secular drift cannot be explained as the consequence of an excitation of the Chandler wobble by random steps of the Earth's inertia tensor. However, the possible contribution of the Chandler wobble excitation to the polar drift has to be taken into account when other mechanisms, such as lithospheric rebound related to deglaciation, are proposed.     

An experimental study of the surface drift currents in a wave flume

The Lagrangian surface drift current induced by surface gravity waves in a wave flume has been investigated experimentally by the particle tracking method. It was observed that in most regions of the flume, the time-mean surface drift current was in the opposite direction to that of the wave propagation. The secondary current in the form of a pair of longitudinal vortices caused by the lateral boundaries was analyzed. It is suggested that the convection of the vorticity generated by the wave-absorber and the lateral boundaries is an important factor in the determination of the time-mean drift in a wave flume.     

Numerical study on the reverse drift force of floating BBDB wave energy absorbers

The motions and time-mean horizontal drift forces of floating backward-bent duct buoy wave energy absorbers in regular waves are calculated taking account of the oscillating surface-pressure due to the pressure drop in the air chamber above the oscillating water column within the scope of the linear wave theory. The present numerical results show that the time-mean drift forces of backward-bent duct buoys are in the reverse direction of propagation of the incident waves over specific frequency ranges as found by McCormick through his experimental work. The drift force has been calculated by the near-field method. A brief discussion on Maruo’s formula which shows that the time-mean drift force must be in the direction of propagation of the incident waves, has also been presented.     

Late Pliocene Mega Debris Flow Deposit and Related Fluid Escapes Identified on the Antarctic Peninsula Continental Margin by Seismic Reflection Data Analysis

We have obtained improved images of a debris flow deposit through the reprocessing of multichannel seismic reflection data between Drifts 6 and 7 of the continental rise of the Pacific margin of the Antarctic Peninsula. The reprocessing, primarily aimed at the reduction of noise, relative to amplitude preservation, deconvolution, also included accurate velocity analyses. The deposit is dated as upper Pliocene (nearly 3.0 Ma) via correlation to Sites 1095 and 1096 of the Ocean Drilling Program (ODP) Leg 178. The estimated volume is about 1800 km³ and the inferred provenance from the continental slope implies a run out distance exceeding 250 km. The dramatic mass-wasting event that produced this deposit, unique in the sedimentary history of this margin, is related to widespread late Pliocene margin erosion. This was associated with a catastrophic continental margin collapse, following the Antarctic ice sheet expansion in response to global cooling. The seismic data analysis also allowed us to identify diffractions and amplitude anomalies interpreted as expressions of sedimentary mounds at the seafloor overlying narrow high-velocity zones that we interpret as conduits of fluid expulsion hosting either methane hydrates or authigenic carbonates. Fluid expulsion was triggered by loading of underlying sediments by the debris flow deposits and may have continued until today by input of fluids from sediment compaction following the deep diagenesis of biogenic silica.     

Wave-induced drift of an elliptical surface film

This study investigates experimentally the drift velocity of an elliptical surface film advected by deep-water waves. Thin polyethylene sheets were used to simulate the inextensible surface film. The drift velocities were obtained by recording and analyzing a sequence of images captured using a video camera. The results show that the drift velocity increases with the longitudinal length of the polyethylene sheet until approximately 0.8 times the wavelength. Beyond that, further increment would not result in substantial increase in the drift velocity. The effect due to the normalized transverse width is found to be significant within a particular range. At large wave steepness, the drift velocity appears to be limited by the Stokes drift. A set of best-fit empirical equations based on the sigmoidal function is introduced for oil spill trajectory prediction.