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A paleoceanographic reconstruction of the southern Panama Basin for the last 23.000 years, based on the benthic foraminiferal analysis from the deep sea core ME0005A-24JC (0.01°N, 86.28°W, water depth 2941) is presented. Cluster and SHEBI (SHE Analysis for Biozone Identification) analyses performed on the benthic foraminiferal assemblages, evidence a faunal turnover in the early Holocene at 14 ky BP. Between 23 and 14 ky BP, Fursenkoina rotundata , Hoeglundina elegans , Globobulimina affinis , Globobulimina pacifica , Cibicidoides wuellerstorfi and Uvigerina hispidocostata were common. Conversely, from 14 ky to the present, the assemblage is represented by Chilostomella oolina , Laticarinina pauperata , and Uvigerina proboscidea . This faunal turnover suggests significant fluctuations in oxygen content at the sea floor and the organic matter (OM) influx, which could reflect: (1) fluctuations in the surface productivity related to the equatorial divergence and, (2) OM advection caused by the dynamic of the deep sea currents. Paleoproductivity estimates and benthic foraminiferal rates depict a general trend towards lower values since the Last Glacial Maximum (LGM) with a conspicuous change at 14 ky BP. Therefore, the paleoceanographic reconstructions of the ME0005A-24JC core suggest a transition from La Niña-like conditions during the LGM to El Niño-like conditions in the recent, as previously proposed for the Eastern Equatorial Pacific. Estimates of the paleo-intensity of deep sea currents based on the relative percentage abundance of the epifaunal foraminifera Cibicidoides wuellerstorfi suggest stronger deep sea currents on the Carnegie Ridge before 14 ky BP. [ABSTRACT FROM AUTHOR]

The purpose of this study is to show that seafloor hydrothermal venting in the open northeast Pacific Ocean has a marked impact on secondary biomass and production within the overlying water column. Specifically, we use net tows and concurrently measured acoustic backscatter data collected over six summers to examine the effects of hydrothermal venting from the Endeavour Segment of Juan de Fuca Ridge on macro-zooplankton biomass and production throughout the entire 2000 m depth range. Previous research shows that ontogenetic diapausing migrators and their predators from the upper ocean aggregate above the neutrally buoyant plumes in summer and resume feeding on plume and bottom upwelled particles, resulting in increased zooplankton reproductive output to the upper ocean. Within the limitations of our sampling methodology, net tows reveal a statistically significant exponential decline in total water-column biomass with increasing lateral distance from the vent fields. The acoustic backscatter data show a similar decline, but only below 800 m depth. Near-surface biomass was highly variable throughout the region, but values near vents consistently ranged higher than summer values found elsewhere in the offshore northeast Pacific. Water-column biomass was similar in magnitude above and below 800 m depth throughout the region. Because epiplume biomass can be advected a considerable distance from vent fields, biomass enhancement of the water column from hydrothermal venting may extend considerable distances to the west and northwest of the vent sites, in the prevailing directions of the subsurface flow. Based on the extensive acoustic Doppler current profiler (ADCP) data collected, and the strong correlation between zooplankton production derived from net sample biomass and acoustic backscatter intensity, we estimate that daily macro-zooplankton production in the upper 400 m of the water column within 10 km of the vent fields averages approximately 16% of photosynthetic primary production (the “ Z ratio”), whereas the total water-column zooplankton production averages 26% of surface primary production. Local grazing-rate estimates, metabolic constraints and other open-ocean studies suggest that the Z ratio should be no higher than 5%, which it is at off-axis background sites in the study region. This finding indicates that nutrient sources other than upper-ocean primary production fuel both upper- and deep-ocean zooplankton biomass and growth near the Endeavour Ridge hydrothermal vents. [ABSTRACT FROM AUTHOR]

Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by the isotopic compositions of methane and carbon dioxide, biomarkers, cultivation data, and gas compositions. Concentrations of indigenous microbial cells below 1.5 km ranged from <10 to ~104 cells cm-3. Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils. This suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed. [ABSTRACT FROM AUTHOR]

In part I, equatorial Pacific Ocean temperature index SST3.4 was found to have segments during 1990–2014 showing a phase-locked annual signal and phase-locked signals of 2- or 3-year periods. Phase locking is to an inferred solar forcing of 1.0 cycle/yr. Here the study extends to the global ocean, from surface to 700 and 2000 m. The same phase-locking phenomena are found. The El Niño/La Niña effect diffuses into the world oceans with a delay of about two months. [ABSTRACT FROM AUTHOR]

During the March 11, 2011 Tohoku tsunami, some Japanese and Russian tide gauges in the Sea of Japan recorded sea level disturbances with periods of several to 10 min and amplitudes of several to a few tens of centimeters starting immediately after the earthquake. Tsunami travel times computed from the 2011 source in the Pacific Ocean to these stations are 1-2 h. To examine the cause of the observed tsunami forerunners and to reproduce them, we carried out tsunami numerical computations from three kinds of coseismic seafloor deformation: the vertical displacement in the tsunami source area in the Pacific Ocean, the vertical displacement extending in the Sea of Japan, and the vertical displacement including the effects of the horizontal displacement and the seafloor slope in both the Pacific Ocean and the Sea of Japan. Only the last source reproduced the observed tsunami forerunners. This indicates that the tsunami forerunners were produced by the horizontal displacement of fault motion and the seafloor slope in the Sea of Japan. For the tide gauge records in Japan, the forerunners with periods longer than 2 min were well reproduced by the tsunami simulation. The shorter-period components may be induced by seismic ground shakings. For the tide gauge records in Russia, the agreement between the observed and computed waveforms was less satisfactory, probably because of less accurate and coarser bathymetry data. [ABSTRACT FROM AUTHOR]

Many species of Solenogastres (Mollusca: Aplacophora) have been described from relatively remote locations or the deep sea. However, knowledge of the diversity of this group of carnivorous molluscs remains incomplete, even in relatively accessible, shallow localities. Here, we describe three new species of interstitial solenogasters from a well-studied site virtually right off the dock of Friday Harbor Laboratories (WA, USA). Two new species ofMacellomenia,M. schanderisp. nov. andM. morseaesp. nov, are described, greatly expanding the biogeographic range of this genus previously only known from the Atlantic. Interestingly,M. schanderiappears to be more similar to the AtlanticM. adenotaSalvini-Plawen, 2003a than the co-occurringM. morseae. However, the one specimen ofM. morseaewe were able to examine by histology was a juvenile, so the adult condition of some characters (mostly dealing with the reproductive system) are unknown. Additionally, a new species ofHypomenia,H. sanjuanensissp. nov, is described, also extending the geographic range of this previously monotypic genus known only from the Gulf of Naples, Italy. DNA barcode sequences are provided to aid in the identification ofM. schanderi,H. sanjuanensis, and the previously described sympatric speciesMeiomenia swedmarkiMorse, 1979. http://zoobank.org/urn:lsid:zoobank.org:pub:87E88772-B9BC-4BE6-93AB-C19FD944DD23 [ABSTRACT FROM AUTHOR]

Several slope failures are observed near the deformation front on the frontal ridges of the northern Cascadia accretionary margin off Vancouver Island. The cause for these events is not clear, although several lines of evidence indicate a possible connection between the occurrence of gas hydrate and submarine landslide features. The presence of gas hydrate is indicated by a prominent bottom-simulating reflector (BSR), at a depth of ∼265–275 m beneath the seafloor (mbsf), as interpreted from vertical-incidence and wide-angle seismic data beneath the ridge crests of the frontal ridges. For one slide, informally called Slipstream Slide, the velocity structure inferred from tomography analyses shows anomalous high velocities values of about 2.0 km s−1 at shallow depths of 100 mbsf. The estimated depth of the glide plane (100 ± 10 m) closely matches the depth of these shallow high velocities. In contrast, at a frontal ridge slide just to the northwest (informally called Orca Slide), the glide plane occurs at the same depth as the current BSR. Our new results indicate that the glide plane of the Slipstream slope failure is associated with the contrast between sediments strengthened by gas hydrate and overlying sediments where little or no hydrate is present. In contrast, the glide plane of Orca Slide is between sediment strengthened by hydrate underlain by sediments beneath the gas hydrate stability zone, possibly containing free gas. Additionally, a set of margin perpendicular normal faults are imaged from seafloor down to BSR depth at both frontal ridges. As inferred from the multibeam bathymetry, the estimated volume of the material lost during the slope failure at Slipstream Slide is about 0.33 km3, and ∼0.24 km3 of this volume is present as debris material on the ocean basin floor. The 20 per cent difference is likely due to more widely distributed fine sediments not easily detectable as bathymetric anomalies. These volume estimates on the Cascadia margin are approaching the mass failure volume for other slides that have generated large tsunamis—for example 1–3 km3 for a 1998 Papua New Guinea slide. [ABSTRACT FROM PUBLISHER]

Abstract: An inventory of Canada's marine renewable energy resources based on numerical modeling of the potential tidal, wave and wind energy has been published that identifies areas with maximum resource potential. However, the inventory does not consider the seabed geological conditions that will control the safe development of seabed installations and cable corridors. The Geological Survey of Canada (Natural Resources Canada) has therefore undertaken an assessment of seafloor geological characteristics and physical environmental parameters that will be encountered during any extensive deployment of marine renewable energy systems for the Pacific offshore of Canada. Here we present an overview of seabed characterization for key sites for each of the three energy types. Narrow passages exiting the Salish Sea near the Canadian boundary with the United States and northwards out of the Strait of Georgia provide very promising sites for tidal generation. Here, elliptical fields of very large subaqueous dunes, from 12 to 28m in height, present a significant challenge to site development. Along the exposed continental shelf of Vancouver Island focused wave-energy close to shore (40–60m water depth) offers significant energy potential, but any engineering systems would have to be founded on a seafloor made up of a mobile gravel lag and an extensive boulder pavement. A large wind farm proposed for the Pacific North Coast would be built on an extensive shallow bank that has active sediment transport and a large field of sand ridges that have developed within a macrotidal environment. A significant challenge is providing for a safe seafloor cable corridor of over 100km that crosses a large subaqueous dune field to connect to the electrical grid on the mainland. These examples show how geoscience has and will provide critical information to project proponents and regulators for the safe development of marine renewable energy. [Copyright &y& Elsevier]

Abstract: Coarse-grained ripples (CGRs) develop within the seafloor depression–sand ridge systems along the Shimizu coast, in the northwestern part of Suruga Bay facing the Pacific Ocean, central Japan. In this paper, we analyze data from high-resolution bathymetry, seafloor observation by an underwater video camera, and high-resolution seismic surveys and seafloor trenching of shallow strata, obtained between 2005 and 2007, to describe their geomorphological and sedimentological characteristics in detail, and to examine the formative processes and maintenance of the systems. In water depths of 5–30m, CGRs occur in seafloor depressions that are approximately 40–70cm deeper than the surrounding sandy seafloor. In many cases, the ripples develop in depressions between shore-normal sand ridges composed mainly of fine sand (<70cm high, 100–400m long) on a relatively narrow shelf. The alongshore width of the sand ridges is 10–100m, and that of the depressions is 10–150m. The CGRs (wavelength<3.5m, height<30cm) have almost shore-parallel crests with a symmetrical or slightly asymmetrical shape, suggesting wave-generated oscillating flows. The crests of the lager ripples are composed of gravel (maximum long axis: 5–8cm) and the troughs consist of fine to very fine sand. The CGR–depression–sand ridge systems develop widely during the passage of typhoons in the summer–autumn seasons. At the narrower shelf, the surface fine-grained sediments and the surface and subsurface coarse-grained sediments, which form the sand ridges and the CGRs respectively, are repeatedly eroded and redeposited during typhoon-related storms. In contrast, active sediments are currently limited to the surface fine deposits on the wider shelf areas. The sediments that make up the CGRs appear to be derived from both modern beach sediments and relict sediments. We postulate that the CGR–depression–sand ridge system appears to be controlled mainly by both seafloor erosion and offshore-directed sediment transport during storms, and these processes may depend on the shelf width. In fact, the sand ridges (covering the CGRs) that imply significant offshore-directed transport only develop on the narrower shelf. The distribution and seabed expression of the CGRs is constrained by the thickness and distribution of surface-covering sandy sediments, such as the sand ridges. This represents a new interpretation of the distribution of CGRs within seafloor depressions on the shelf of an active margin that receives a large supply of sandy and gravelly fluvial sediments, and differs from the processes seen on the sediment-starved shelves of passive margins. [Copyright &y& Elsevier]

A long-range sound propagation experiment was conducted in the West Pacific Ocean in July 2013. Linear frequency-modulated signals with a frequency band of 260–360 Hz were transmitted by a transducer hung on a floating ship during the experiment and were received by a horizontal line array towed by another ship sailing away from the transducer. The maximum distance between the two ships was 1029 km. Signals were received at the distances 34–220 km, 612–635 km and 926–1029 km. Transmission loss versus distance between source and receiver was obtained and compared with the theoretical results predicted by the parabolic equation method program RAM. It is shown that RAM is adequate for estimating the transmission loss for distances up to 1029 km. When the water depth is larger than the surface conjugate depth, the ocean bottom rarely influences the transmission loss in the convergence zones. However, in the opposite situation, the ocean bottom contributes significantly to the transmission loss. [ABSTRACT FROM AUTHOR]