Genetic divergence in nuclear genomes between populations of Fagus crenata along the Japan Sea and Pacific sides of Japan.

PubMed

Hiraoka, Koichi; Tomaru, Nobuhiro

2009-05-01

Genetic diversity and structure in Fagus crenata were studied by analyzing 14 nuclear microsatellite loci in 23 populations distributed throughout the species' range. Although population differentiation was very low (F (ST) = 0.027; R (ST) = 0.041), both neighbor-joining tree and Bayesian clustering analyses provided clear evidence of genetic divergence between populations along the Japan Sea (Japan Sea lineage) and Pacific (Pacific lineage) sides of Japan, indicating that physical barriers to migration and gene flow, notably the mountain ranges separating the populations along the Japan Sea and Pacific sides, have promoted genetic divergence between these populations. The two lineages of the nuclear genome are generally consistent with those of the chloroplast genome detected in a previous study, with several discrepancies between the two genomes. Within-population genetic diversity was generally very high (average H (E) = 0.839), but decreased in a clinal fashion from southwest to northeast, largely among populations of the Japan Sea lineage. This geographical gradient may have resulted from the late-glacial and postglacial recolonization to the northeast, which led to a loss of within-population genetic diversity due to cumulative founder effects.

Crustal architecture of the eastern margin of Japan Sea: back-arc basin opening and contraction

NASA Astrophysics Data System (ADS)

No, T.; Sato, T.; Takahashi, N.; Kodaira, S.; Kaneda, Y.; Ishiyama, T.; Sato, H.

2012-12-01

Although large earthquakes such as the 1964 Niigata earthquake (M 7.5), 1983 Nihonkai-Chubu earthquake (M 7.8), and 1993 Hokkaido Nansei-Oki earthquake (M 7.8) have caused large amounts of damage to the eastern margin of the Japan Sea, a substantial number of seismic studies have been conducted for the seismogenic zone on the Pacific Ocean side of Japan. In addition, the detail of the source fault model for the eastern margin of the Japan Sea is not well defined for all cases. This highlights the need for further studies to investigate seismic imaging. Therefore, we have collaborated with other Japanese research institutions for a project titled "Priority Investigations of Strain Concentration Areas" (which is funded by Special Coordination Funds for Promoting Science and Technology, Japan). This project has conducted seismic surveys from 2009 to 2012 using the deep-sea research vessel, Kairei, from the Japan Agency for Marine-Earth Science and Technology. There is a strain concentration area in the eastern part of the survey area (Okamura et al., 1995). The western part of the survey area includes the Yamato Basin and Japan Basin. It is very important to study the crustal structure in the seismotectonic studies of the eastern margin of the Japan Sea. We conducted a marine seismic survey by using a multichannel seismic (MCS) system and ocean bottom seismographs (OBSs) along the eastern margin of the Japan Sea. Seismic data were acquired along 42 lines with a total length of approximately 9,000 km. The following results were obtained from seismic imaging. On the basis of the results of the MCS imaging, active reverse faults and folds were observed in the margin of the Toyama Trough; however, the sedimentary layers in the trough were flat. In the sedimentary layers and crusts of the Sado Ridge, Mogami Trough, and source area of the 1964 Niigata earthquake located north of the Sado Island, greater deformation was observed. The deformation weakened toward the Yamato

A Linkage of Recent Arctic Summer Sea Ice and Snowfall Variability of Japan

NASA Astrophysics Data System (ADS)

Iwamoto, K.; Honda, M.; Ukita, J.

2014-12-01

In spite of its mid-latitude location, Japan has a markedly high amount of snowfall, which owes much to the presence of cold air-break from Siberia and thus depends on the strength of the Siberian high and the Aleutian low. With this background this study examines the relationship between interannual variability and spatial patterns of snowfall in Japan with large-scale atmospheric and sea ice variations. The lag regression map of the winter snowfall in Japan on the time series of the Arctic SIE from the preceding summer shows a seesaw pattern in the snowfall, suggesting an Arctic teleconnection to regional weather. From the EOF analyses conducted on the snowfall distribution in Japan, we identify two modes with physical significance. The NH SIC and SLP regressed on PC1 show a sea ice reduction in the Barents and Kara Seas and anomalous strength of the Siberia high as discussed in Honda et al. (2009) and other studies, which support the above notion that the snowfall variability of Japan is influenced by Arctic sea ice conditions. Another mode is related to the AO/NAO and the hemispheric scale double sea-ice seesaw centered over the sub-Arctic region: one between the Labrador and Nordic Seas in the Atlantic and the other between the Okhotsk and Bering Seas from the Pacific as discussed in Ukita et al. (2007). Together, observations point to a significant role of the sea-ice in determining mid-latitude regional climate and weather patterns.

Benthic community structures in the North Sea

NASA Astrophysics Data System (ADS)

Heip, C.; Craeymeersch, J. A.

1995-03-01

Coherent assemblages of marine benthic species have been recognized from the early twentieth century, and the classical papers of Petersen (1914, 1918) were based on studies of limited areas in the North Sea. In 1986, a synoptic survey of the North Sea north to 57°N was undertaken by a group of ten laboratories from seven North Sea countries. The results of this survey have recently been published (Heip et al., 1992a, b; Künitzer et al., 1992; Huys et al., 1992), and some of the results are summarized in this paper. The analysis of the macrofauna is based on slightly more than 700 taxa. In general, the North Sea macrofauna consists of northern species extending south to the northern margins of the Dogger Bank, and southern species extending north to the 100 m depth line. The central North Sea is an area of overlap of southern and northern species, especially around the 70 m depth contour. Consistent groupings of species are recognized that were summarized in seven faunal groupings. Macrofaunal body weight, density and diversity increase linearly towards the north. Macrofaunal biomass for the whole area averages 7 g adwt. m-2 and decreases from south to north. Distribution patterns and trends within the meiofauna were very different. Nematodes, which are the dominant taxon overall, are least abundant in the sandy sediments of the Southern Bight, then increase to a maximum around 53° 30' N and slowly decrease again towards the north. Copepod density and diversity are highest in the Southern Bight, due to the presence of many interstitial species. A large number of species new to science were recorded by the North Sea Benthos Survey and about 1500 species are expected to occur. Copepods show very distinct assemblages according to water depth and sediment type. The contrasting patterns in latitudinal gradients of body weight and number of species of macro- and meiofauna can be only partially explained. Latitude and sediment characteristics, such as grain size and

Collective dose estimates by the marine food pathway from liquid radioactive wastes dumped in the Sea of Japan.

PubMed

Togawa, O; Povinec, P P; Pettersson, H B

1999-09-30

IAEA-MEL has been engaged in an assessment programme related to radioactive waste dumping by the former USSR and other countries in the western North Pacific Ocean and its marginal seas. This paper focuses on the Sea of Japan and on estimation of collective doses from liquid radioactive wastes. The results from the Japanese-Korean-Russian joint expeditions are summarized, and collective doses for the Japanese population by the marine food pathway are estimated from liquid radioactive wastes dumped in the Sea of Japan and compared with those from global fallout and natural radionuclides. The collective effective dose equivalents by the annual intake of marine products caught in each year show a maximum a few years after the disposals. The total dose from all radionuclides reaches a maximum of 0.8 man Sv in 1990. Approximately 90% of the dose derives from 137Cs, most of which is due to consumption of fish. The total dose from liquid radioactive wastes is approximately 5% of that from global fallout, the contribution of which is below 0.1% of that of natural 210Po.

Spring and fall bloom evolutions estimated from 8 day composite satellite chlorophyll data in the East/Japan Sea

NASA Astrophysics Data System (ADS)

Kim, B.; Cho, Y.; Kim, S.; Kim, K.

2012-12-01

Bong-Guk Kim1, Yang-Ki Cho1, Sangil Kim2, Kwang-Yul, Kim1 1 School of Earth and Environmental Sciences, College of Natural Sciences, Seoul National University, Seoul, South Korea 2 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA To understand the ocean carbon cycle, estimating the ocean biomass is necessary and it has been done by various methods. Satellite observation is one of beneficial methods to investigate ocean biomass. Satellite data enable us to monitor chlorophyll-a for wide area with high resolution and frequency. The East/Japan Sea, which called as 'miniature ocean' due to its rapid turnover circulation, is one of the most productive ocean. With the concerning global warming, a number of studies on temporal and spatial distribution of satellite chlorophyll in the East/Japan Sea have been processed. However, most of these studies have used monthly data set which can not resolve detail evolution of chlorophyll-a. In this study, detail evolutions of spring and fall bloom are investigated by the CSEOF (Cyclo-Stationary EOF) analysis of 8-day composite MODIS chlorophyll data from July 2002 to February 2012. For the CSEOF analysis, optimal interpolation (OI) method was applied to fill the blank data which is critical problem in satellite data. Spring bloom started at western Japanese coast on 57th day of the year. And it gradually moves eastern coast of Korean and then moves to northern Primorye coast. Spring bloom spreads entire the East/Japan Sea on 113th day of the year and then, it disappears from the southern East/Japan Sea. Spring bloom ends in the northern East/Japan Sea. In the case of fall bloom, it starts at Korean coast on 265th day of the year, and it moves to the north along the Korean coast by 329th day of the year. After that day, fall bloom ends near the northern coast of Korea on 353rd day of the year.

Association of Ocean Energy Exploitation of Resources Promotion Sea of Japan

NASA Astrophysics Data System (ADS)

Aoyama, C.; Aoyama, S.

2014-12-01

Nine prefectures of 1 local government prefecture of the Sea of Japan side established "Association of Ocean Energy Exploitation of Resources Promotion Sea of Japan" (the following, Association of Sea of Japan) in September, 2012. They support methane hydrate exploitation of resources of the government and aim at the local activation and job creation. Niigata and Hyogo that were members of the association of Sea of Japan carried out a prefecture original methane hydrate investigation. They appeal to the government for development promotion of the government by showing the result. On the other hand, Wakayama located on the Pacific side wants to appeal to the government for the reexamination of the development sea area by showing that outer layer type methane hydrate exists to the sea area that is nearer the landside than the sea area that the government develops. The Independent Institute carried out collaborative investigation each with Niigata, Hyogo and Wakayama in 2013. I show the results of research. In the joint investigation with Niigata, plural plumes　were observed in Mogami trough east slope (from depth of the water 200m 600m) . In the joint investigation with Hyogo, I carried out observation of a methane plume and the structure and the seafloor topography under the sea bottom in Oki east sea area. Furthermore, I performed a piston core ring and gathered five samples and confirmed plural traces of the methane hydrate. In the joint investigation with Wakayama, plural plumes were observed in Shionomisaki canyon (from depth of the water 1,700m 2,200m). There is hardly the report of the plume on the Pacific side so far. Therefore I want to continue observing it in future.

Another look at North Sea pole tide dynamics

NASA Technical Reports Server (NTRS)

Dickman, S. R.; Preisig, J. R.

1986-01-01

The mechanism proposed by Wunsch (1974) to explain pole tide observations in the North Sea is evaluated. Wunsch's equations governing pole tide in the North Sea are presented, and solutions for correcting the depth, stream function, and deviation of the tidal height from the equilibrium values are described. The similarity between the Stokes paradox and the tidal equations of the North Sea, and the need for inclusion of inertial terms in the tidal equations are discussed.

Seismicity of the Earth 1900-2007, Japan and Vicinity

USGS Publications Warehouse

Rhea, Susan; Tarr, Arthur C.; Hayes, Gavin P.; Villaseñor, Antonio; Benz, Harley

2010-01-01

This map shows details of Japan and vicinity not visible in an earlier publication, U.S. Geological Survey Scientific Investigations Map 3064. Japan and its island possessions lie across four major tectonic plates: Pacific plate, North America plate; Eurasia plate; and Philippine Sea plate. The Pacific plate is subducted into the mantle, beneath Hokkaido and northern Honshu, along the eastern margin of the Okhotsk microplate, a proposed subdivision of the North America plate (Bird, 2003). Farther south, the pacific plate is subducted beneath volcanic islands along the eastern margin of the Philippine Sea plate. This 2,200 km-long zone of subduction of the Pacific plate is responsible for the creation of the deep offshore Ogasawara and Japan trenches as well as parallel chains of islands and volcanoes, typical of the Circumpacific island arcs. Similarly, the Philippine Sea plate is itself subducting under the Eurasia plate along a zone, extending from Taiwan to southern Honshu, that comprises the Ryuku Islands and the Nansei-Shonto trench.

Revisiting sea level changes in the North Sea during the Anthropocene

NASA Astrophysics Data System (ADS)

Jensen, Jürgen; Dangendorf, Sönke; Wahl, Thomas; Niehüser, Sebastian

2016-04-01

The North Sea is one of the best instrumented ocean basins in the world. Here we revisit sea level changes in the North Sea region from tide gauges, satellite altimetry, hydrographic profiles and ocean reanalysis data from the beginning of the 19th century to present. This includes an overview of the sea level chapter of the North Sea Climate Change Assessment (NOSCCA) complemented by results from more recent investigations. The estimates of long-term changes from tide gauge records are significantly affected by vertical land motion (VLM), which is related to both the large-scale viscoelastic response of the solid earth to ice melting since the last deglaciation and local effects. Removing VLM (estimated from various data sources such as GPS, tide gauge minus altimetry and GIA) significantly reduces the spatial variability of long-term trends in the basin. VLM corrected tide gauge records suggest a transition from relatively moderate changes in the 19th century towards modern trends of roughly 1.5 mm/yr during the 20th century. Superimposed on the long-term changes there is a considerable inter-annual to multi-decadal variability. On inter-annual timescales this variability mainly reflects the barotropic response of the ocean to atmospheric forcing with the inverted barometer effect dominating along the UK and Norwegian coastlines and wind forcing controlling the southeastern part of the basin. The decadal variability is mostly remotely forced and dynamically linked to the North Atlantic via boundary waves in response to long-shore winds along the continental slope. These findings give valuable information about the required horizontal resolution of ocean models and the necessary boundary conditions and are therefore important for the dynamical downscaling of sea level projections for the North Sea coastlines.

Some fundamental questions about the evolution of the Sea of Japan back-arc

NASA Astrophysics Data System (ADS)

Van Horne, A.; Sato, H.; Ishiyama, T.

2016-12-01

The Japanese island arc separated from Asia through the rifting of an active continental margin, and the opening of the Sea of Japan back-arc, in the middle Miocene. Due to its complex tectonic setting, the Sea of Japan back-arc was affected by multiple external events contemporary with its opening, including a plate reorganization, the opening of at least two other nearby back-arcs (Shikoku Basin and Okhotsk Sea/Kuril Basin), and two separate arc-arc collisions, involving encroachment upon Japan of the Izu-Bonin and Kuril arcs. Recent tectonic inversion has exposed entire sequences of back-arc structure on land, which remain virtually intact because of the short duration of inversion. Japan experiences a high level of seismic activity due to its position on the overriding plate of an active subduction margin. Continuous geophysical monitoring via a dense nationwide seismic/geodetic network, and a program of controlled-source refraction/wide-angle reflection profiling, directed towards earthquake hazard mitigation, have made it the repository of a rich geophysical data set through which to understand the processes that have shaped back-arc development. Timing, structural evolution, and patterns of magmatic activity during back-arc opening in the Sea of Japan were established by earlier investigations, but fundamental questions regarding back-arc development remain outstanding. These include (1) timing of the arrival of the Philippine Sea plate in southwest Japan, (2) the nature of the plate boundary prior to its arrival, (3) the pre-rift location of the Japanese island arc when it was attached to Asia, (4) the mechanism of back-arc opening (pull-apart or trench retreat), (5) the speed of opening, (6) simultaneous or sequential development of the multi-rift system, (7) the origin of the anomalously thick Yamato Basin ocean crust, and (8) the pattern of concentrated deformation in the failed-rift system of the eastern Sea of Japan since tectonic inversion. Resolving

Morphology, taxonomic status and distribution of the opisthobranch mollusc Coryphella (s.l.) japonica from the central deep water basin of the Sea of Japan

NASA Astrophysics Data System (ADS)

Martynov, Alexander V.

2013-02-01

The opisthobranch fauna (Gastropoda: Opisthobranchia) of the deep sea basins of the Sea of Japan is reviewed. A detailed description of the most common deep sea nudibranch species Coryphella japonicaVolodchenko, 1941 is given based on materials from various expeditions (including R/V "Vityaz" cruises and SoJaBio project). Distinct morphological features of C. japonica are discussed and its valid taxonomic status is confirmed. The considerable radular variability of C. japonica for the first time is documented using a scanning electron microscope. Unique features of the bathymetric distribution of C. japonica ranging from shelf to the abyssal depths are discussed in connection with the "pseudabyssal area" concept. C. japonica was compared to its assumed synonym C. salmonacea, and to similar C. athadona. Material from all these species, including types of C. japonica, was examined externally, anatomically via dissection, and SEM. C. salmonacea is restricted to North Atlantic and Arctic only, whereas C. japonica inhabits NE Pacific including deep water basins of the Sea of Japan.

Deep-Sea Phylogeographic Structure Shaped by Paleoenvironmental Changes and Ongoing Ocean Currents Around the Sea of Japan in a Crangonid Shrimp, Argis lar.

PubMed

Fujita, Junta; Drumm, David T; Iguchi, Akira; Ueda, Yuji; Yamashita, Yuho; Ito, Masaki; Tominaga, Osamu; Kai, Yoshiaki; Ueno, Masahiro; Yamashita, Yoh

2017-10-01

The deep-sea crangonid shrimp, Argis lar, is a highly abundant species from the northern Pacific Ocean. We investigated its phylogeographic and demographic structure across the species' extensive range, using mitochondrial DNA sequence variation to evaluate the impact of deep-sea paleoenvironmental dynamics in the Sea of Japan on population histories. The haplotype network detected three distinct lineages with allopatric isolation, which roughly corresponded to the Sea of Japan (Lineage A), the northwestern Pacific off the Japanese Archipelago (Lineage B), and the Bering Sea/Gulf of Alaska (Lineage C). Lineage A showed relatively low haplotype and nucleotide diversity, a significantly negative value of Tajima's D, and a star-shaped network, suggesting that anoxic bottom-water in the Sea of Japan over the last glacial period may have brought about a reduction in the Sea of Japan population. Furthermore, unexpectedly, the distributions of Lineage A and B were closely related to the pathways of the two ocean currents, especially along the Sanriku Coast. This result indicated that A. lar could disperse across shallow straits through the ocean current, despite their deep-sea adult habitat. Bayesian inference of divergence time revealed that A. lar separated into three lineages approximately 1 million years before present (BP) in the Pleistocene, and then had been influenced by deep-sea paleoenvironmental change in the Sea of Japan during the last glacial period, followed by a more recent larval dispersal with the ocean current since ca. 6 kilo years BP.

Sea level anomaly in the North Atlantic and seas around Europe: Long-term variability and response to North Atlantic teleconnection patterns.

PubMed

Iglesias, Isabel; Lorenzo, M Nieves; Lázaro, Clara; Fernandes, M Joana; Bastos, Luísa

2017-12-31

Sea level anomaly (SLA), provided globally by satellite altimetry, is considered a valuable proxy for detecting long-term changes of the global ocean, as well as short-term and annual variations. In this manuscript, monthly sea level anomaly grids for the period 1993-2013 are used to characterise the North Atlantic Ocean variability at inter-annual timescales and its response to the North Atlantic main patterns of atmospheric circulation variability (North Atlantic Oscillation, Eastern Atlantic, Eastern Atlantic/Western Russia, Scandinavian and Polar/Eurasia) and main driven factors as sea level pressure, sea surface temperature and wind fields. SLA variability and long-term trends are analysed for the North Atlantic Ocean and several sub-regions (North, Baltic and Mediterranean and Black seas, Bay of Biscay extended to the west coast of the Iberian Peninsula, and the northern North Atlantic Ocean), depicting the SLA fluctuations at basin and sub-basin scales, aiming at representing the regions of maximum sea level variability. A significant correlation between SLA and the different phases of the teleconnection patterns due to the generated winds, sea level pressure and sea surface temperature anomalies, with a strong variability on temporal and spatial scales, has been identified. Long-term analysis reveals the existence of non-stationary inter-annual SLA fluctuations in terms of the temporal scale. Spectral density analysis has shown the existence of long-period signals in the SLA inter-annual component, with periods of ~10, 5, 4 and 2years, depending on the analysed sub-region. Also, a non-uniform increase in sea level since 1993 is identified for all sub-regions, with trend values between 2.05mm/year, for the Bay of Biscay region, and 3.98mm/year for the Baltic Sea (no GIA correction considered). The obtained results demonstrated a strong link between the atmospheric patterns and SLA, as well as strong long-period fluctuations of this variable in spatial and

Back-arc basin opening and closure along the southern margin of the Sea of Japan

NASA Astrophysics Data System (ADS)

Sato, Hiroshi; Claringbould, Johan; Ishiyama, Tatsuya; Kato, Naoko; Abe, Susumu; Kawasaki, Shinji

2016-04-01

Following the tsunami disaster produced by 2001 Off-Tohoku earthquake (M9) along the Pacific coast of Japan, the Japanese government started an intense evaluation of tsunami hazards. This evaluation spanned along the full Japanese coast, including the Sea of Japan coast on the western side of the Japan arc. In the Sea of Japan, tsunamis are produced by crustal faults. As the longer interval of faulting activity, the historical records of tsunamis in the Sea of Japan are not enough for the evaluation of tsunami height. Thus, the evaluation is carried out based on structural analyses of the margin of the Sea of Japan. To get better understanding of the present-day structural geometry and develop a source-fault model in this region, intense seismic reflection profiling has been carried out since 2013. We introduce the results of the seismic reflection profiles and discuss the structural evolution of the southern margin of the Sea of Japan. 2D seismic reflection profiles were acquired using 1950 cu. in. air-gun and 2100 m streamer cable. The seismic profiles provide the image image up to 3 seconds TWT. The southern margin of the Sea of Japan was produced by back-arc opening and post-rift deformation, and the structural evolution of this area is divided into several stages: rifting (25 - 14 Ma), post-rift compression (14 - 5 Ma), weak thrusting (5 - 1 Ma), and strike-slip deformation (1 Ma to present). During the rifting stage that is associated with the fan-shaped opening of the Sea of Japan, grabens and half-grabens were formed trending parallel to the extension of SW-Japan arc. These grabens were filled by syn-rift sediments, and the maximum thickness of basin fill is observed along the southern margin of the rifted crust. The opening of the Sea of Japan ceased as a result of the collision of Izu-Bonin-Mariana arc system at the Izu collision zone on the central part of Honshu, Japan. Soon after the this event, the young Shikoku basin within the Philippine Sea plate

Mechanisms of long-term mean sea level variability in the North Sea

NASA Astrophysics Data System (ADS)

Dangendorf, Sönke; Calafat, Francisco; Øie Nilsen, Jan Even; Richter, Kristin; Jensen, Jürgen

2015-04-01

We examine mean sea level (MSL) variations in the North Sea on timescales ranging from months to decades under the consideration of different forcing factors since the late 19th century. We use multiple linear regression models, which are validated for the second half of the 20th century against the output of a state-of-the-art tide+surge model (HAMSOM), to determine the barotropic response of the ocean to fluctuations in atmospheric forcing. We demonstrate that local atmospheric forcing mainly triggers MSL variability on timescales up to a few years, with the inverted barometric effect dominating the variability along the UK and Norwegian coastlines and wind (piling up the water along the coast) controlling the MSL variability in the south from Belgium up to Denmark. However, in addition to the large inter-annual sea level variability there is also a considerable fraction of decadal scale variability. We show that on decadal timescales MSL variability in the North Sea mainly reflects steric changes, which are mostly remotely forced. A spatial correlation analysis of altimetry observations and baroclinic ocean model outputs suggests evidence for a coherent signal extending from the Norwegian shelf down to the Canary Islands. This supports the theory of longshore wind forcing along the eastern boundary of the North Atlantic causing coastally trapped waves to propagate along the continental slope. With a combination of oceanographic and meteorological measurements we demonstrate that ~80% of the decadal sea level variability in the North Sea can be explained as response of the ocean to longshore wind forcing, including boundary wave propagation in the Northeast Atlantic. These findings have important implications for (i) detecting significant accelerations in North Sea MSL, (ii) the conceptual set up of regional ocean models in terms of resolution and boundary conditions, and (iii) the development of adequate and realistic regional climate change projections.

Cycling of nutrient elements in the North Sea

NASA Astrophysics Data System (ADS)

Brockmann, U. H.; Laane, R. W. P. M.; Postma, J.

The cycling of elements of inorganic and organic nutrients (carbon, nitrogen, phosphorus and silicate) in the North Sea is described. The regional effects on nutrient cycling such as thermal and haline stratification, coastal interaction, river discharges, upwelling and frontal zones are discussed. The horizontal and vertical distribution of the inorganic nutrients (nitrate, phosphate, ammonia and silicate) at the surface is given for the whole North Sea during two situations: spring (1986) and winter (1987). In winter, highest nutrient concentrations were found at the northern boundary in the Atlantic inflow, and in the continental coastal waters. During the winter cruise, nutrient minima were detected in the Dogger Bank area. This is an indication that primary production continues during winter. Generally, the surface concentrations during winter were similar to the bottom concentrations. Except for phosphate, highest concentrations were measured just above the bottom. During late spring 1986 the concentrations of nutrients at the surface and below the densicline were generally significantly lower than during winter. Only at the Atlantic boundary in the north and near the estuaries higher concentrations were detected. In stratified parts of the North Sea, the decomposition of sedimented biomass caused the ammonia concentrations in the bottom layer to be significantly higher in spring than in winter. Incidents of frontal upwelling in the central North Sea introduce nutrient-rich bottom water into the euphotic zone, enhancing phytoplankton growth in the central North Sea during summer. The ratios of nitrogen nutrients to phosphate show that in the central North Sea nitrogen is a limiting factor rather than phosphorus, whereas in the continental coastal water and off England the opposite is true. Riverine input and trapping mechanisms in the estuaries and tidal flats cause the concentrations of organic matter (dissolved and particulate) to be highest in the coastal

Regulation of CO2 Air Sea Fluxes by Sediments in the North Sea

NASA Astrophysics Data System (ADS)

Burt, William; Thomas, Helmuth; Hagens, Mathilde; Brenner, Heiko; Pätsch, Johannes; Clargo, Nicola; Salt, Lesley

2016-04-01

A multi-tracer approach is applied to assess the impact of boundary fluxes (e.g. benthic input from sediments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the δ13C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration. In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indicates the presence of an external carbon source, which is traced to the European continental coastline using naturally-occurring radium isotopes (224Ra and 228Ra). 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of metabolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e. unbuffered) release of metabolic DIC. Finally, long-term pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.

Methylated Arsenic in the Southern North Sea

NASA Astrophysics Data System (ADS)

Millward, G. E.; Kitts, H. J.; Comber, S. D. W.; Ebdon, L.; Howard, A. G.

1996-07-01

Water samples collected in the southern North Sea in August 1988 (mid-summer), April 1989 (spring), September/October 1989 (late summer) and May 1990 were analysed for dissolved inorganic arsenic, monomethylarsenic (MMA) and dimethylarsenic (DMA). In mid-summer 1988, both MMA and DMA were observed throughout the southern North Sea, with lowest concentrations of dissolved inorganic arsenic (mean 6·48 nmol l -1) and the highest proportions of methylated arsenic (29%) being found in highly productive continental coastal waters. In April 1989, waters of the North Sea had a mean inorganic arsenic concentration of 12 nmol l -1and methylated species were not detected, even though phytoplankton blooms were present. Shipboard phytoplankton incubation studies (in May 1990) revealed that uptake of dissolved inorganic arsenic occurred at a rate of 0·57 nmol l -1 day -1, but the appearance of dissolved methylated species was not observed. During September/October 1989, while MMA and DMA were present in all sectors of the North Sea, the relative proportion of methylated compounds (11%) in continental coastal waters was less than mid-summer 1988. It was shown that estuarine, porewater and atmospheric inputs of arsenic species were relatively small during the observational periods, and that almost all of the methylated compounds originated from decaying algal tissue. Demethylation of DMA and MMA throughout winter contributed to the dissolved inorganic arsenic pool. The results are discussed in the context of the development of a predictive model for the cycling of arsenic in the North Sea.

SeaWiFS: North Pacific Storm

NASA Technical Reports Server (NTRS)

2002-01-01

An extratropical storm can be seen swirling over the North Pacific just south of Alaska. This SeaWiFS image was collected yesterday at 23:20 GMT. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

Two centuries of extreme events over the Baltic Sea and North Sea regions

NASA Astrophysics Data System (ADS)

Stendel, Martin; den Besselaar Else, van; Abdel, Hannachi; Jaak, Jaagus; Elizabeth, Kent; Christiana, Lefebvre; Gudrun, Rosenhagen; Anna, Rutgersson; Frederik, Schenk; der Schrier Gerard, van; Tim, Woolings

2017-04-01

Two centuries of extreme events over the Baltic Sea and North Sea regions In the framework of the BACC 2 (for the Baltic Sea) and NOSCCA projects (for the North Sea region), studies of past and present variability and changes in atmospheric variables within the North Sea region over the instrumental period (roughly the past 200 years) have been investigated. Findings on trends in temperature and precipitation have already been presented. Here we focus on data homogeneity issues and examine how reliable reanalyses are in this context. Unlike most other regions in the world, there is a wealth of old observations available for the Baltic and North Sea regions, most of it in handwritten form in meteorological journals and other publications. These datasets need to be carefully digitised and homogenized. For this, a thorough quality control must be applied; otherwise the digitised datasets may prove useless or even counterproductive. We present evidence that this step cannot be conducted without human interference and thus cannot be fully automated. Furthermore, inhomogeneities due to e.g. instrumentation and station relocations need to be addressed. A wealth of reanalysis products is available, which can help detect such inhomogeneities in observed time series, but at the same time are prone to biases and/or spurious trends themselves e.g. introduced by changes in the availability and quality of the underlying assimilated data. It therefore in general remains unclear in how far we can simulate the pre-satellite era with respect to homogeneity with reanalyses based only on parts of the observing system. Extreme events and changes in extreme situations are more important and of greater (societal) significance than changes in mean climate. However, changes in extreme weather events are difficult to assess not only because they are, per definition, rare events, but also due to the homogeneity issues outlined above. Taking these into account, we present evidence for changes

Reconstruction of paleoenvironmental changes based on the planktonic foraminiferal assemblages off Shimokita (Japan) in the northwestern North Pacific

NASA Astrophysics Data System (ADS)

Kuroyanagi, Azumi; Kawahata, Hodaka; Narita, Hisashi; Ohkushi, Ken'ichi; Aramaki, Takafumi

2006-08-01

Planktonic foraminifera live in the upper ocean, and their assemblages can record the surrounding environment. To reconstruct changes in water masses and the timing of flow of the Oyashio and Tsugaru currents through the Tsugaru Strait after the Last Glacial Maximum, when the Japan Sea had been almost isolated from the surrounding seas, we investigated at high resolution the planktonic foraminiferal fauna in seafloor sediments off the Shimokita (core MD01-2409: 41°33.9'N, 141°52.1'E), in the northwestern North Pacific, over the last 26,900 years. Factor analysis of the foraminiferal assemblage suggests that the water mass changed significantly as a result of the deglacial sea-level rise and opening of the straits into the Japan Sea. Mass accumulation rates of some selected foraminiferal species that inhabit characteristic environments (e.g., warm stratified water, Oyashio Current, Tsushima Current) corroborate these changes in water mass and water column structure. We also used the ratio of the dextral form to total Neogloboquadrina pachyderma as an indicator of subsurface (below the pycnocline) water temperature. We recognized five distinct periods of oceanographic change at the study site, which is just east of the Tsugaru Strait: (1) Oyashio Current affecting both surface and subsurface waters (26.9-15.7 thousand calendar years before present (cal. kyr BP)); (2) vertical mixing and subsurface warming as the Oyashio Current began to flow into the Japan Sea through the Tsugaru Strait (15.7-10.6 cal. kyr BP); (3) outflow of the Tsugaru Current from the Japan Sea into the Pacific, leading to baroclinic conditions, with the surface layer under the influence of the Tsugaru and the subsurface layers of the Oyashio Current (10.6-9.0 cal. kyr BP); (4) stratification of the water column developed as the flow of the Tsugaru Current increased (9.0-6.2 cal. kyr BP); and (5) warming of the subsurface layer, disruption of the stratification, and dominance of the Tsugaru

Organic Matter Contents and Paleoproductivity Variation Within Late Pleistocene Japan Sea/East Sea Sediments: Results from IODP Expedition 346

NASA Astrophysics Data System (ADS)

Black, H. D.; Anderson, W. T., Jr.

2017-12-01

Inorganic and organic matter concentrations as well as the stable isotopes of nitrogen and organic carbon are presented for continuous sedimentary sequences collected during Integrated Ocean Drilling Program (IODP) Expedition 346 in the Japan Sea/East Sea in 2013. During major glacioeustatic sea level changes, the paleoceanographic conditions within the Japan Sea/East Sea widely vary due to the shallow, narrow straights connecting the sea to surrounding waters limiting an influx of oceanic currents. During glacial sea level low-stands the sea can be nearly isolated, creating a highly-stratified water column and hypoxic to anoxic bottom water conditions. Meanwhile during sea level high-stands, the Tsushima Warm Current (TWC) flows into the sea bringing warmer, nutrient-rich inputs, leading to vertical mixing and oxic conditions. This study aims to better understand the role of orbital cycling within the organic matter and stable isotope contents of these Late Pleistocene sediments. A total of 192 samples were analyzed each for %CaCO3, %TOC, δ13C, %N, and δ15N from two Expedition 346 sampling sites (U1426 and U1427) during the last 430,000 years and statistical analyses were completed using wavelet and time series analyses. Carbonate concentration ranges from 0-44.3%, total organic carbon 0.2 to 6.4%, δ13C -25.8 to -19.6‰, %N 0.04 to 0.4%, and δ15N 3.8 to 13.1‰. These results are well correlated with b* color values of the sediment and generally show increased productivity during interglacial periods, likely through increased vertical mixing and deepwater ventilation, when compared to glacial periods within the Japan Sea/East Sea when the sea may be partially isolated.

2012/13 abnormal cold winter in Japan associated with Large-scale Atmospheric Circulation and Local Sea Surface Temperature over the Sea of Japan

NASA Astrophysics Data System (ADS)

Ando, Y.; Ogi, M.; Tachibana, Y.

2013-12-01

reference, the conventional AO index is shown by the gray line. (b) a 5-day running mean WP index, (c) area-averaged Surface Air Temperature anomalies in Japan, (d) Air Temperature anomalies, (e) heat flux anomalies, and (f) Sea Surface Temperature anomalies. The boxed area on the Sea of Japan indicates the area in which the (d)-(f) indexes were calculated.

North Atlantic sea-level variability during the last millennium

NASA Astrophysics Data System (ADS)

Gehrels, Roland; Long, Antony; Saher, Margot; Barlow, Natasha; Blaauw, Maarten; Haigh, Ivan; Woodworth, Philip

2014-05-01

Climate modelling studies have demonstrated that spatial and temporal sea-level variability observed in North Atlantic tide-gauge records is controlled by a complex array of processes, including ice-ocean mass exchange, freshwater forcing, steric changes, changes in wind fields, and variations in the speed of the Gulf Stream. Longer records of sea-level change, also covering the pre-industrial period, are important as a 'natural' and long-term baseline against which to test model performance and to place recent and future sea-level changes and ice-sheet change into a long-term context. Such records can only be reliably and continuously reconstructed from proxy methods. Salt marshes are capable of recording decimetre-scale sea-level variations with high precision and accuracy. In this paper we present four new high-resolution proxy records of (sub-) decadal sea-level variability reconstructed from salt-marsh sediments in Iceland, Nova Scotia, Maine and Connecticut that span the past 400 to 900 years. Our records, based on more than 100 new radiocarbon analyses, Pb-210 and Cs-137 measurements as well as other biological and geochemical age markers, together with hundreds of new microfossil observations from contemporary and fossil salt marshes, capture not only the rapid 20th century sea-level rise, but also small-scale (decimetre, multi-decadal) sea-level fluctuations during preceding centuries. We show that in Iceland three periods of rapid sea-level rise are synchronous with the three largest positive shifts of the reconstructed North Atlantic Oscillation (NAO) index. Along the North American east coast we compare our data with salt-marsh records from New Jersey, North Carolina and Florida and observe a trend of increased pre-industrial sea-level variability from south to north (Florida to Nova Scotia). Mass changes and freshwater forcing cannot explain this pattern. Based on comparisons with instrumental sea-level data and modelling studies we hypothesise that

North Sea ecosystem change from swimming crabs to seagulls

PubMed Central

Luczak, C.; Beaugrand, G.; Lindley, J. A.; Dewarumez, J-M.; Dubois, P. J.; Kirby, R. R.

2012-01-01

A recent increase in sea temperature has established a new ecosystem dynamic regime in the North Sea. Climate-induced changes in decapods have played an important role. Here, we reveal a coincident increase in the abundance of swimming crabs and lesser black-backed gull colonies in the North Sea, both in time and in space. Swimming crabs are an important food source for lesser black-backed gulls during the breeding season. Inhabiting the land, but feeding mainly at sea, lesser black-backed gulls provide a link between marine and terrestrial ecosystems, since the bottom-up influence of allochthonous nutrient input from seabirds to coastal soils can structure the terrestrial food web. We, therefore, suggest that climate-driven changes in trophic interactions in the marine food web may also have ensuing ramifications for the coastal ecology of the North Sea. PMID:22764111

North Sea ecosystem change from swimming crabs to seagulls.

PubMed

Luczak, C; Beaugrand, G; Lindley, J A; Dewarumez, J-M; Dubois, P J; Kirby, R R

2012-10-23

A recent increase in sea temperature has established a new ecosystem dynamic regime in the North Sea. Climate-induced changes in decapods have played an important role. Here, we reveal a coincident increase in the abundance of swimming crabs and lesser black-backed gull colonies in the North Sea, both in time and in space. Swimming crabs are an important food source for lesser black-backed gulls during the breeding season. Inhabiting the land, but feeding mainly at sea, lesser black-backed gulls provide a link between marine and terrestrial ecosystems, since the bottom-up influence of allochthonous nutrient input from seabirds to coastal soils can structure the terrestrial food web. We, therefore, suggest that climate-driven changes in trophic interactions in the marine food web may also have ensuing ramifications for the coastal ecology of the North Sea.

[Morphology of gametes in sea urchins from Peter the Great Bay, Sea of Japan].

PubMed

Drozdov, A L; Vinnikova, V V

2010-01-01

The fine structure of the gametes in six sea urchin species of the Sea of Japan was studied. The spermatozoons in Strongylocentrotus nudus, S. intermedius, Echinocardium cordatum, Scaphechinus mirabilis, Sc. grizeus and Echinarachnius parma are species-specific. The conical head and symmetrically disposed ring-shape mitochondrion are common to regular sea urchin sperm cells. S. nudus is characterized by the bulb-shaped head of the zoosperm; S. intermedius, by a bullet-shaped one. The zoosperm spearhead and small amount of postacrosome material are common to irregular sea urchins; the sperm width: length ratio varies for different species, with the highest for Sc. mirabilis. The zoosperm of Sc. griseus is characterized by two lipid drops in the cell center. Asymmetrical mitochondrion disposal is usual for E. parma. Actin filaments are found in the postacrosome material in the zoosperm of cordiform sea urchins. The differences in the fine structure of zoosperm in eurybiont species Ech. cordatum inhabiting the Sea of Japan and coastal areas of the Northeast Atlantic may bear record to the complex existence of species Ech. cordatum. The fine structure of zoosperm is unique for each of the studied families, Strongylocentrotidae, Scutellidae, and Loveniidae. The eggs of all the species are characterized by vitelline and tremelloid membranes. The vitelline membrane is formed by cytoplasm protrusions; the area between them is filled with fubrillary material. The tremelloid membrane is formed by fubrillary material associated with apical parts of microvilli of the vitelline membrane. The irregular sea urchins Sc. griseus, Sc. mirabilis and E. parma are characterized by chromatophores situated in the tremelloid membrane, with the highest abundance in Sc. mirabilis.

Henricia djakonovi sp. nov. (Echinodermata, Echinasteridae): a new sea star species from the Sea of Japan.

PubMed

Chichvarkhin, Anton

2017-01-01

A new sea star species, H. djakonovi sp.n., was discovered in Rudnaya Bay in the Sea of Japan. This is a sympatric species of the well-known and common species Henricia pseudoleviuscula Djakonov, 1958. Both species are similar in body size and proportions, shape of skeletal plates, and life coloration, which distinguishes them from the other Henricia species inhabiting the Sea of Japan. Nevertheless, these species can be distinguished by their abactinal spines: in both species, they are short and barrel-like, but the new species is the only Henricia species in Russian waters of the Pacific that possesses such spines with a massive, smooth, bullet-like tip. The spines in H. pseudoleviuscula are crowned with a variable number of well-developed thorns. About half (<50%) of the abactinal pseudopaxillae in the new species are oval, not crescent-shaped as in H. pseudoleviuscula .

Recruitment success of different fish stocks in the North Sea in relation to climate variability

NASA Astrophysics Data System (ADS)

Dippner, Joachim W.

1997-09-01

Long-term data of year class strengths of different commercially harvested fish stocks based on a virtual population analysis (VPA) are available from ICES. The anomalies of these long-term data sets of year class strength are analyzed using Empirical Orthogonal Functions (EOFs) and are related to climate variability: the anomalies of the sea surface temperature (SST) in the northern North Sea and the North Atlantic Oscillation (NAO) index. A Canonical Correlation Analysis (CCA) between the leading eigenmodes is performed. The results suggest that the variability in the fish recruitment of western mackerel and three gadoids, namely North Sea cod, North Sea saithe, and North Sea whiting is highly correlated to the variability of the North Sea SST which is directly influenced by the NAO. For North Sea haddock and herring no meaningful correlation exists to North Sea SST and NAO. The results allow the conclusion that is seems possible to predict long-term changes in the fish recruitment from climate change scenarios for North Sea cod, North Sea saithe and western mackerel. Furthermore, the results indicate the possibility of recruitment failure for North Sea cod, North Sea whiting, and western mackerel in the case of global warming.

Observed mean sea level changes around the North Sea coastline from 1800 to present

NASA Astrophysics Data System (ADS)

Wahl, T.; Haigh, I. D.; Woodworth, P. L.; Albrecht, F.; Dillingh, D.; Jensen, J.; Nicholls, R. J.; Weisse, R.; Wöppelmann, G.

2013-09-01

This paper assesses historic changes in mean sea level around the coastline of the North Sea, one of the most densely populated coasts in the world. Typically, such analyses have been conducted at a national level, and detailed geographically wider analyses have not been undertaken for about 20 years. We analyse long records (up to 200 years) from 30 tide gauge sites, which are reasonably uniformly distributed along the coastline, and: (1) calculate relative sea level trends; (2) examine the inter-annual and decadal variations; (3) estimate regional geocentric (sometimes also referred to as 'absolute') sea level rise throughout the 20th century; and (4) assess the evidence for regional acceleration of sea-level rise. Relative sea level changes are broadly consistent with known vertical land movement patterns. The inter-annual and decadal variability is partly coherent across the region, but with some differences between the Inner North Sea and the English Channel. Data sets from various sources are used to provide estimates of the geocentric sea level changes. The long-term geocentric mean sea level trend for the 1900 to 2011 period is estimated to be 1.5 ± 0.1 mm/yr for the entire North Sea region. The trend is slightly higher for the Inner North Sea (i.e. 1.6 ± 0.1 mm/yr), and smaller but not significantly different on the 95% confidence level for the English Channel (i.e. 1.2 ± 0.1 mm/yr). The uncertainties in the estimates of vertical land movement rates are still large, and the results from a broad range of approaches for determining these rates are not consistent. Periods of sea level rise acceleration are detected at different times throughout the last 200 years and are to some extent related to air pressure variations. The recent rates of sea level rise (i.e. over the last two to three decades) are high compared to the long-term average, but are comparable to those which have been observed at other times in the late 19th and 20th century.

Contribution of atmospheric circulation to recent off-shore sea-level variations in the Baltic Sea and the North Sea

NASA Astrophysics Data System (ADS)

Karabil, Sitar; Zorita, Eduardo; Hünicke, Birgit

2018-01-01

The main purpose of this study is to quantify the contribution of atmospheric factors to recent off-shore sea-level variability in the Baltic Sea and the North Sea on interannual timescales. For this purpose, we statistically analysed sea-level records from tide gauges and satellite altimetry and several climatic data sets covering the last century. Previous studies had concluded that the North Atlantic Oscillation (NAO) is the main pattern of atmospheric variability affecting sea level in the Baltic Sea and the North Sea in wintertime. However, we identify a different atmospheric circulation pattern that is more closely connected to sea-level variability than the NAO. This circulation pattern displays a link to sea level that remains stable through the 20th century, in contrast to the much more variable link between sea level and the NAO. We denote this atmospheric variability mode as the Baltic Sea and North Sea Oscillation (BANOS) index. The sea-level pressure (SLP) BANOS pattern displays an SLP dipole with centres of action located over (5° W, 45° N) and (20° E, 70° N) and this is distinct from the standard NAO SLP pattern in wintertime. In summertime, the discrepancy between the SLP BANOS and NAO patterns becomes clearer, with centres of action of the former located over (30° E, 45° N) and (20° E, 60° N). This index has a stronger connection to off-shore sea-level variability in the study area than the NAO in wintertime for the period 1993-2013, explaining locally up to 90 % of the interannual sea-level variance in winter and up to 79 % in summer. The eastern part of the Gulf of Finland is the area where the BANOS index is most sensitive to sea level in wintertime, whereas the Gulf of Riga is the most sensitive region in summertime. In the North Sea region, the maximum sea-level sensitivity to the BANOS pattern is located in the German Bight for both winter and summer seasons. We investigated, and when possible quantified, the contribution of several

Introduced marine species of the North Sea coasts

NASA Astrophysics Data System (ADS)

Reise, K.; Gollasch, S.; Wolff, W. J.

1998-09-01

About 80 non-indigenous species are assumed to have been introduced into the North Sea by transoceanic shipping and aquaculture. The number is certainly underestimated as most small organisms received insufficient attention at the species level. Also, the seafaring tradition of the North Sea countries is much longer than our biological surveys are. Most exotic invertebrates originate from the western Atlantic and were introduced by shipping, while most algae stem from the Pacific and came with the introduced oysters. A peak of newcomers was observed in the 1970s. Most of the arrivals became established in brackish environments, at harbor sites and in the vicinity of oyster farms, fouling on hard substrates or living as epibionts. A few live in sediments, are holoplanktonic or are parasites. At the open coast, approximately 6% of the macrobenthic species are exotics, while in estuaries their share is up to 20%. Most exotics have been encountered in the southern North Sea first, and many did not spread further north. About 25% of the established non-natives are widespread and attain locally high abundances. As a consequence, some inshore habitats are entirely dominated by exotics. The overall effect on the ecosystem seems to be more additive than one of displacement. This suggests that the coastal biota of the North Sea are quite capable of accommodating newcomers. However, this is no guarantee that the next introduced species may not cause severe ecological change or economic harm. There is a need to minimize the risk of unintentional introductions by ballast water treatment and by adhering to quarantine procedures in aquaculture. Current research on exotics in the North Sea is regarded as inadequate for proper evaluation and management requirements.

Assimilation of the seabird and ship drift data in the north-eastern sea of Japan into an operational ocean nowcast/forecast system

PubMed Central

Miyazawa, Yasumasa; Guo, Xinyu; Varlamov, Sergey M.; Miyama, Toru; Yoda, Ken; Sato, Katsufumi; Kano, Toshiyuki; Sato, Keiji

2015-01-01

At the present time, ocean current is being operationally monitored mainly by combined use of numerical ocean nowcast/forecast models and satellite remote sensing data. Improvement in the accuracy of the ocean current nowcast/forecast requires additional measurements with higher spatial and temporal resolution as expected from the current observation network. Here we show feasibility of assimilating high-resolution seabird and ship drift data into an operational ocean forecast system. Data assimilation of geostrophic current contained in the observed drift leads to refinement in the gyre mode events of the Tsugaru warm current in the north-eastern sea of Japan represented by the model. Fitting the observed drift to the model depends on ability of the drift representing geostrophic current compared to that representing directly wind driven components. A preferable horizontal scale of 50 km indicated for the seabird drift data assimilation implies their capability of capturing eddies with smaller horizontal scale than the minimum scale of 100 km resolved by the satellite altimetry. The present study actually demonstrates that transdisciplinary approaches combining bio-/ship- logging and numerical modeling could be effective for enhancement in monitoring the ocean current. PMID:26633309

Atmospheric concentrations and air-sea exchanges of nonylphenol, tertiary octylphenol and nonylphenol monoethoxylate in the North Sea.

PubMed

Xie, Zhiyong; Lakaschus, Soenke; Ebinghaus, Ralf; Caba, Armando; Ruck, Wolfgang

2006-07-01

Concentrations of nonylphenol isomers (NP), tertiary octylphenol (t-OP) and nonylphenol monoethoxylate isomers (NP1EO) have been simultaneously determined in the sea water and atmosphere of the North Sea. A decreasing concentration profile appeared following the distance increasing from the coast to the central part of the North Sea. Air-sea exchanges of t-OP and NP were estimated using the two-film resistance model based upon relative air-water concentrations and experimentally derived Henry's law constant. The average of air-sea exchange fluxes was -12+/-6 ng m(-2)day(-1) for t-OP and -39+/-19 ng m(-2)day(-1) for NP, which indicates a net deposition is occurring. These results suggest that the air-sea vapour exchange is an important process that intervenes in the mass balance of alkylphenols in the North Sea.

First columbellid species (Gastropoda: Buccinoidea) from deep-sea hydrothermal vents, discovered in Okinawa Trough, Japan.

PubMed

Chen, Chong; Watanabe, Hiromi Kayama; Araya, Juan Francisco

2017-12-12

The molluscan diversity of deep-sea chemosynthetic ecosystems in Japan has been in general well documented with about 80 described species, of which over half are gastropods (Sasaki et al. 2005; Fujikura et al. 2012; Sasaki et al. 2016). Recently, however, a number of novel hydrothermal vent sites were discovered in the area using multibeam echo-sounding (Nakamura et al. 2015), providing opportunities for new discoveries. As a part of ongoing studies documenting the biodiversity of such sites, we present the first record of Columbellidae from hydrothermal vents, with a new species recovered from Natsu and Aki sites, in the Iheya North hydrothermal field (for map and background on the vent field see Nakamura et al. 2015).

Terrestrial dissolved organic matter distribution in the North Sea.

PubMed

Painter, Stuart C; Lapworth, Dan J; Woodward, E Malcolm S; Kroeger, Silke; Evans, Chris D; Mayor, Daniel J; Sanders, Richard J

2018-07-15

The flow of terrestrial carbon to rivers and inland waters is a major term in the global carbon cycle. The organic fraction of this flux may be buried, remineralized or ultimately stored in the deep ocean. The latter can only occur if terrestrial organic carbon can pass through the coastal and estuarine filter, a process of unknown efficiency. Here, data are presented on the spatial distribution of terrestrial fluorescent and chromophoric dissolved organic matter (FDOM and CDOM, respectively) throughout the North Sea, which receives organic matter from multiple distinct sources. We use FDOM and CDOM as proxies for terrestrial dissolved organic matter (tDOM) to test the hypothesis that tDOM is quantitatively transferred through the North Sea to the open North Atlantic Ocean. Excitation emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) revealed a single terrestrial humic-like class of compounds whose distribution was restricted to the coastal margins and, via an inverse salinity relationship, to major riverine inputs. Two distinct sources of fluorescent humic-like material were observed associated with the combined outflows of the Rhine, Weser and Elbe rivers in the south-eastern North Sea and the Baltic Sea outflow to the eastern central North Sea. The flux of tDOM from the North Sea to the Atlantic Ocean appears insignificant, although tDOM export may occur through Norwegian coastal waters unsampled in our study. Our analysis suggests that the bulk of tDOM exported from the Northwest European and Scandinavian landmasses is buried or remineralized internally, with potential losses to the atmosphere. This interpretation implies that the residence time in estuarine and coastal systems exerts an important control over the fate of tDOM and needs to be considered when evaluating the role of terrestrial carbon losses in the global carbon cycle. Copyright © 2018 The Author(s). Published by Elsevier B.V. All rights reserved.

North Sea Storm Driving of Extreme Wave Heights

NASA Astrophysics Data System (ADS)

Bell, Ray; Gray, Suzanne; Jones, Oliver

2017-04-01

The relationship between storms and extreme ocean waves in the North sea is assessed using a long-period wave dataset and storms identified in the Interim ECMWF Re-Analysis (ERA-Interim). An ensemble sensitivity analysis is used to provide information on the spatial and temporal forcing from mean sea-level pressure and surface wind associated with extreme ocean wave height responses. Extreme ocean waves in the central North Sea arise due to either the winds in the cold conveyor belt (northerly-wind events) or winds in the warm conveyor belt (southerly-wind events) of extratropical cyclones. The largest wave heights are associated with northerly-wind events which tend to have stronger wind speeds and occur as the cold conveyor belt wraps rearwards round the cyclone to the cold side of the warm front. The northerly-wind events also provide a larger fetch to the central North Sea. Southerly-wind events are associated with the warm conveyor belts of intense extratropical storms developing in the right upper-tropospheric jet exit region. There is predictability in the extreme ocean wave events up to two days before the event associated with a strengthening of a high pressure system to the west (northerly-wind events) and south-west (southerly-wind events) of the British Isles. This acts to increase the pressure gradient over the British Isles and therefore drive stronger wind speeds in the central North sea.

Dose prediction in Japan for nuclear test explosions in North Korea.

PubMed

Takada, Jun

2008-11-01

The impact on Japan of the underground test conducted in North Korea on October 9, 2006 is examined. By the use of the results of modelling assessment and environmental monitoring, it is concluded that there was no radiation impact on Japan. This suggests a safely conducted underground nuclear test or an explosion with a very low output.

Convective Systems Over the Japan Sea: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Yoshizaki, Masanori; Shie, Chung-Lin; Kato, Teryuki

2002-01-01

Wintertime observations of MCSs (Mesoscale Convective Systems) over the Sea of Japan - 2001 (WMO-01) were collected from January 12 to February 1, 2001. One of the major objectives is to better understand and forecast snow systems and accompanying disturbances and the associated key physical processes involved in the formation and development of these disturbances. Multiple observation platforms (e.g., upper-air soundings, Doppler radar, wind profilers, radiometers, etc.) during WMO-01 provided a first attempt at investigating the detailed characteristics of convective storms and air pattern changes associated with winter storms over the Sea of Japan region. WMO-01 also provided estimates of the apparent heat source (Q1) and apparent moisture sink (Q2). The vertical integrals of Q1 and Q2 are equal to the surface precipitation rates. The horizontal and vertical adjective components of Q1 and Q2 can be used as large-scale forcing for the Cloud Resolving Models (CRMs). The Goddard Cumulus Ensemble (GCE) model is a CRM (typically run with a 1-km grid size). The GCE model has sophisticated microphysics and allows explicit interactions between clouds, radiation, and surface processes. It will be used to understand and quantify precipitation processes associated with wintertime convective systems over the Sea of Japan (using data collected during the WMO-01). This is the first cloud-resolving model used to simulate precipitation processes in this particular region. The GCE model-simulated WMO-01 results will also be compared to other GCE model-simulated weather systems that developed during other field campaigns (i.e., South China Sea, west Pacific warm pool region, eastern Atlantic region and central USA).

NOx Emissions from Oil and Gas Production in the North Sea

NASA Astrophysics Data System (ADS)

Lee, J. D.; Foulds, A.; Purvis, R.; Vaughan, A. R.; Carslaw, D.; Lewis, A. C.

2015-12-01

North Sea oil is a mixture of hydrocarbons, comprising liquid petroleum and natural gas, produced from petroleum reservoirs beneath the North Sea. As of January 2015, the North Sea is the world's most active offshore drilling region with 173 rigs drilling. During the summer of 2015, a series of survey flights took place on the UKs FAAM BAe 146 research aircraft with the primary aim to assess background methane (and other hydrocarbons) levels in the drilling areas of the North Sea. Also measured were Nitrogen Oxides (NO and NO2), which are emitted from almost all combustion processes and are a key air pollutant, both directly and as a precursor to ozone (O3). The oil and gas platforms in the North Sea are often manned and require significant power generation and support vessels for their continued operation, processes that potentially emit significant amounts of NOx into an otherwise relative clean environment. During these flights we were able to measure the NO­­­x (and any subsequently produced O3) emitted from specific rigs, as well as the NOx levels in the wider North Sea oil and gas production region (see figure for example). NOx mixing ratios of <10 ppbv were frequently observed in plumes, with significant perturbation to the wider North Sea background levels. NOx emissions from the rigs are point sources within the UKs National Atmospheric Emission Inventory (NAEI) and the measurements taken in plumes from individual rigs are used to assess the accuracy of these estimates.

Habitats of North American sea ducks.

USGS Publications Warehouse

Derksen, Dirk V.; Petersen, Margaret R.; Savard, Jean-Pierre L.

2015-01-01

Breeding, molting, fall and spring staging, and wintering habitats of the sea duck tribe Mergini are described based on geographic locations and distribution in North America, geomorphology, vegetation and soil types, and fresh water and marine characteristics. The dynamics of habitats are discussed in light of natural and anthropogenic events that shape areas important to sea ducks. Strategies for sea duck habitat management are outlined and recommendations for international collaboration to preserve key terrestrial and aquatic habitats are advanced. We follow the definition of habitat advanced by Odum (1971), which is the place or space where an organism lives. Weller (1999) emphasized that habitats for waterbirds required presence of sufficient resources (i.e., food, water, cover, space) for maintenance during a portion of their annual cycle. Habitats exploited by North American sea ducks are diverse, widespread across the continent and adjacent marine waters and until recently, most were only superficially known. A 15-year-long effort funded research on sea duck habitats through the Sea Duck Joint Venture and the Endangered or Threatened Species programs of the United States and Canada. Nevertheless, important gaps remain in our understanding of key elements required by some species during various life stages. Many significant habitats, especially staging and wintering sites, have been and continue to be destroyed or altered by anthropogenic activities. The goal of this chapter is to develop a comprehensive summary of marine, freshwater, and terrestrial habitats and their characteristics by considering sea duck species with similar needs as groups within the tribe Mergini. Additionally, we examine threats and changes to sea duck habitats from human-caused and natural events. Last, we evaluate conservation and management programs underway or available for maintenance and enhancement of habitats critical for sea ducks.

Phylogeography of the sandy beach amphipod Haustorioides japonicus along the Sea of Japan: Paleogeographical signatures of cryptic regional divergences

NASA Astrophysics Data System (ADS)

Takada, Yoshitake; Sakuma, Kay; Fujii, Tetsuo; Kojima, Shigeaki

2018-01-01

Recent findings of genetic breaks within apparently continuous marine populations challenge the traditional vicariance paradigm in population genetics. Such "invisible" boundaries are sometimes associated with potential geographic barriers that have forced divergence of an ancestral population, habitat discontinuities, biogeographic disjunctions due to environmental gradients, or a combination of these factors. To explore the factors that influence the genetic population structure of apparently continuous populations along the Sea of Japan, the sandy beach amphipod Haustorioides japonicus was examined. We sampled a total of 300 individuals of H. japonicus from the coast of Japan, and obtained partial sequences of the mitochondrial COI gene. The sequences from 19 local populations were clustered into five groups (Northwestern Pacific, Northern, Central, Southern Sea of Japan, and East China Sea) based on a spatial genetic mixture analysis and a minimum-spanning network. AMOVA and pairwise Fst tests further supported the significant divergence of the five groups. Phylogenetic analysis revealed the relationship among the haplotypes of H. japonicus and outgroups, which inferred the northward range expansion of the species. A relaxed molecular-clock Bayesian analysis inferred the early-to middle-Pleistocene divergence of the populations. Among the five clusters, the Central Sea of Japan showed the highest values for genetic diversity indices indicating the existence of a relatively stable and large population there. The hypothesis is also supported by Bayesian Skyline Plots that showed sudden population expansion for all the clusters except for Central Sea of Japan. The present study shows genetic boundaries between the Sea of Japan and the neighboring seas, probably due to geographic isolation during the Pleistocene glacial periods. We further found divergence between the populations along the apparently continuous coast of the Sea of Japan. Historical changes in the

Aftereffects of Subduction-Zone Earthquakes: Potential Tsunami Hazards along the Japan Sea Coast.

PubMed

Minoura, Koji; Sugawara, Daisuke; Yamanoi, Tohru; Yamada, Tsutomu

2015-10-01

The 2011 Tohoku-Oki Earthquake is a typical subduction-zone earthquake and is the 4th largest earthquake after the beginning of instrumental observation of earthquakes in the 19th century. In fact, the 2011 Tohoku-Oki Earthquake displaced the northeast Japan island arc horizontally and vertically. The displacement largely changed the tectonic situation of the arc from compressive to tensile. The 9th century in Japan was a period of natural hazards caused by frequent large-scale earthquakes. The aseismic tsunamis that inflicted damage on the Japan Sea coast in the 11th century were related to the occurrence of massive earthquakes that represented the final stage of a period of high seismic activity. Anti-compressive tectonics triggered by the subduction-zone earthquakes induced gravitational instability, which resulted in the generation of tsunamis caused by slope failing at the arc-back-arc boundary. The crustal displacement after the 2011 earthquake infers an increased risk of unexpected local tsunami flooding in the Japan Sea coastal areas.

Projected sea level rise, gyre circulation and water mass formation in the western North Pacific: CMIP5 inter-model analysis

NASA Astrophysics Data System (ADS)

Terada, Mio; Minobe, Shoshiro

2017-09-01

Future changes in the dynamic sea level (DSL), which is defined as sea-level deviation from the global mean sea level, is investigated over the North Pacific, by analyzing data from the Coupled Model Intercomparison Project Phase 5. The analysis provides more comprehensive descriptions of DSL responses to the global warming in this region than available from previous studies, by using surface and subsurface data until the year 2300 under middle and high greenhouse-gas emission scenarios. The DSL changes in the North Pacific are characterized by a DSL rise in the western North Pacific around the Kuroshio Extension (KE), as also reported by previous studies. Subsurface density analysis indicates that DSL rise around the KE is associated with decrease in density of subtropical mode water (STMW) and with northward KE migration, the former (latter) of which is relatively strong between 2000 and 2100 for both RCP4.5 and RCP8.5 (between 2100 and 2300 for RCP8.5). The STMW density decrease is related to large heat uptake to the south and southeast of Japan, while the northward KE migration is associated with the poleward shift of the wind stress field. These features are commonly found in multi-model ensemble means and the relations among representative quantities produced by different climate models.

Projected sea level rise, gyre circulation and water mass formation in the western North Pacific: CMIP5 inter-model analysis

NASA Astrophysics Data System (ADS)

Terada, Mio; Minobe, Shoshiro

2018-06-01

Future changes in the dynamic sea level (DSL), which is defined as sea-level deviation from the global mean sea level, is investigated over the North Pacific, by analyzing data from the Coupled Model Intercomparison Project Phase 5. The analysis provides more comprehensive descriptions of DSL responses to the global warming in this region than available from previous studies, by using surface and subsurface data until the year 2300 under middle and high greenhouse-gas emission scenarios. The DSL changes in the North Pacific are characterized by a DSL rise in the western North Pacific around the Kuroshio Extension (KE), as also reported by previous studies. Subsurface density analysis indicates that DSL rise around the KE is associated with decrease in density of subtropical mode water (STMW) and with northward KE migration, the former (latter) of which is relatively strong between 2000 and 2100 for both RCP4.5 and RCP8.5 (between 2100 and 2300 for RCP8.5). The STMW density decrease is related to large heat uptake to the south and southeast of Japan, while the northward KE migration is associated with the poleward shift of the wind stress field. These features are commonly found in multi-model ensemble means and the relations among representative quantities produced by different climate models.

Holocene relative sea-level change in Hiroshima Bay, Japan: A semi-quantitative reconstruction based on ostracodes

USGS Publications Warehouse

Yasuhara, Moriaki; Seto, Koji

2006-01-01

Holocene relative sea-level changes in Hiroshima Bay were reconstructed from fossil ostracodes from a core, using a semi-quantitative method. In Hiroshima Bay, relative sea level rose rapidly (about 25 m) between ca. 9000 cal yr BP and ca. 5800 cal yr BP, after which it gradually fell (about 5 m) to its present level. The peak in relative sea level occurred at ca. 5800 cal yr BP. The sea-level curve for Hiroshima Bay is similar to curves for tectonically stable areas of Japan (e.g., Osaka Bay). ?? by the Palaeontological Society of Japan.

Wind Stress Forcing of the North Sea "Pole Tide"

NASA Technical Reports Server (NTRS)

OConnor, William P.; Chao, Benjamin Fong; Zheng, Dawei; Au, Andrew Y.

1998-01-01

We conducted numerical simulations of the wind-forcing of the sea level variations in the North Sea using a barotropic ocean model with realistic geography, bathymetry, and boundary conditions, to examine the forcing of the 14-month "pole tide" which is known to be strong along the Denmark- Netherlands coast. The simulation input is the monthly-mean surface wind stress field from the National Centers for Environmental Prediction (NCEP) reanalysis for the 40-year period 1958-1997. The output sea level response was then compared with 10 coastal tide gauge records from the Permanent Service for Mean Sea Level (PSMSL). Besides the strong seasonal variations, several prominent quasi-periodicities exist at around 7 years, 3 years, 14 months, 9 months, and 6.5 months. Correlation and spectral analyses show remarkable agreement between the model output and the observations, particularly in the 14-month, or Chandler period band. The latter indicates that the enhanced pole tide found in the North Sea along the Denmark-Netherlands coast is actually the coastal setup response to wind stress forcing with a periodicity of 14 months. We find no need to invoke a geophysical explanation involving resonance-enhancement of pole tide in the North Sea to explain the observations.

North Atlantic storm driving of extreme wave heights in the North Sea

NASA Astrophysics Data System (ADS)

Bell, R. J.; Gray, S. L.; Jones, O. P.

2017-04-01

The relationship between storms and extreme ocean waves in the North Sea is assessed using a long-period wave data set and storms identified in the Interim ECMWF Re-Analysis (ERA-Interim). An ensemble sensitivity analysis is used to provide information on the spatial and temporal forcing from mean sea-level pressure and surface wind associated with extreme ocean wave height responses. Extreme ocean waves in the central North Sea arise due to intense extratropical cyclone winds from either the cold conveyor belt (northerly-wind events) or the warm conveyor belt (southerly-wind events). The largest wave heights are associated with northerly-wind events which tend to have stronger wind speeds and occur as the cold conveyor belt wraps rearward round the cyclone to the cold side of the warm front. The northerly-wind events provide a larger fetch to the central North Sea to aid wave growth. Southerly-wind events are associated with the warm conveyor belts of intense extratropical cyclones that develop in the left upper tropospheric jet exit region. Ensemble sensitivity analysis can provide early warning of extreme wave events by demonstrating a relationship between wave height and high pressure to the west of the British Isles for northerly-wind events 48 h prior. Southerly-wind extreme events demonstrate sensitivity to low pressure to the west of the British Isles 36 h prior.

Seasonal variation of semidiurnal internal tides in the East/Japan Sea

NASA Astrophysics Data System (ADS)

Jeon, Chanhyung; Park, Jae-Hun; Varlamov, Sergey M.; Yoon, Jong-Hwan; Kim, Young Ho; Seo, Seongbong; Park, Young-Gyu; Min, Hong Sik; Lee, Jae Hak; Kim, Cheol-Ho

2014-05-01

The seasonal variation of semidiurnal internal tides in the East/Japan Sea was investigated using 25 month long output from a real-time ocean forecasting system. The z coordinate eddy-resolving high-resolution numerical model, called the RIAM ocean model, incorporates data assimilation that nudges temperature and salinity fields together with volume transport through the Korea Strait to produce realistic oceanic currents and stratification. In addition to atmospheric forcing, it includes tidal forcing of 16 major components along open boundaries. The model generates energetic semidiurnal internal tides around the northern entrance of the Korea Strait. Energy conversion from barotropic to baroclinic (internal) tides varies seasonally with maxima in September (ranging 0.48-0.52 GW) and minima in March (ranging 0.11-0.16 GW). This seasonal variation is induced by the seasonality in stratification near the southwestern East/Japan Sea. The propagation distance of the internal tides is associated with generation intensity and wavelength. From late summer to early winter, the semidiurnal internal tides travel relatively far from the generation region due to stratification changes; its energy dissipates less as a result of longer wavelengths. Our results suggest that spatiotemporal variation of internal-tide-induced mixing due to the seasonality in the generation, propagation, and dissipation of internal tides should be considered for a more realistic simulation of water masses and circulation in models of the East/Japan Sea.

Edwardsia sojabio sp. n. (Cnidaria: Anthozoa: Actiniaria: Edwardsiidae), a new abyssal sea anemone from the Sea ofJapan

NASA Astrophysics Data System (ADS)

Sanamyan, Nadya; Sanamyan, Karen

2013-02-01

The paper describes new deep-water edwardsiid sea anemone Edwardsia sojabio sp. n. which is very common on soft muddy bottoms at lower bathyal and upper abyssal depths in the Sea of Japan. It was recorded in high quantity in depths between 2545 and 3550 m and is the second abyssal species of the genus Edwardsia.

Characteristics of the Japanese sea cucumber Apostichopus japonicus's population in the Sea of Japan (Kievka Bay)

NASA Astrophysics Data System (ADS)

Gavrilova, G. S.; Sukhin, I. Yu.

2011-06-01

In Kievka Bay of the Sea of Japan, the population of the Japanese sea cucumber Apostichopus japonicus inhabits the areas of coarse sediments and complex bottom topography. These distributional patterns are closely related to the species' ecology, i.e., to the demand for protection against the wave turbulence. The aggregationing coverage of the sea cucumber population is about 80 hectares, where ˜200 thousand animals were accounted for in the last years. The aggregation's area varies during the year, which is closely related to the species' biological peculiarities, such as their behavioral patterns and the redistribution of their food resources. A significant increase of the juvenile population occurred after the farm-reared sea cucumber spat were released in 2003.

Integrated tephrostratigraphy and stable isotope stratigraphy in the Japan Sea and East China Sea using IODP Sites U1426, U1427, and U1429, Expedition 346 Asian Monsoon

NASA Astrophysics Data System (ADS)

Sagawa, Takuya; Nagahashi, Yoshitaka; Satoguchi, Yasufumi; Holbourn, Ann; Itaki, Takuya; Gallagher, Stephen J.; Saavedra-Pellitero, Mariem; Ikehara, Ken; Irino, Tomohisa; Tada, Ryuji

2018-12-01

Integrated Ocean Drilling Program Expedition 346 "Asian Monsoon" obtained sediment successions at seven sites in the Japan Sea (Sites U1422-U1427 and U1430) and at two closely located sites in the northern East China Sea (Sites U1428 and U1429). The Quaternary sediments of the Japan Sea are characterized by centimeter- to decimeter-scale dark-light alternations at all sites deeper than 500 m water depth. The sedimentary records from these sites allow an investigation of the regional environmental response to global climate change, including changes in the Asian Monsoon and eustatic sea level. However, the discontinuous occurrence of calcareous microfossils in the deep-sea sediments and their distinct isotope signature that deviates from standard marine δ18O records do not permit the development of a detailed stable isotope stratigraphy for Japan Sea sediments. Here, we present the tephrostratigraphy for the two southernmost sites drilled in the Japan Sea (Sites U1426 and U1427) and for one site drilled in the East China Sea (Site U1429) along with the benthic δ18O isotope stratigraphy for the shallower Site U1427 and the East China Sea Site U1429. Eighteen tephra layers can be correlated between sites using the major-element composition and morphology of volcanic glass shards, and the compositions of grains and heavy minerals. Tephra correlations show that negative δ18O peaks in the Japan Sea correspond to positive glacial maxima peaks in the East China Sea. Using this integrated stratigraphic approach, we establish an orbital-scale age model at Site U1427 for the past 1.1 Myr. The correlation of tephra layers between the shallower Site U1427 (330 m below sea level: mbsl) and the deeper Site U1426 (903 mbsl) in the southern Japan Sea provides the opportunity for further age constraints. Our results show that alternations in sediment color at Sites U1426 and U1427 can be correlated for the past 1.1 Myr with minor exceptions. Thus, the stable isotope stratigraphy

Spatial distribution of cold-season lightning frequency in the coastal areas of the Sea of Japan

NASA Astrophysics Data System (ADS)

Tsurushima, Daiki; Sakaida, Kiyotaka; Honma, Noriyasu

2017-12-01

The coastal areas of the Sea of Japan are a well-known hotspot of winter lightning activity. This study distinguishes between three common types of winter lightning in that region (types A-C), based on their frequency distributions and the meteorological conditions under which they occur. Type A lightning occurs with high frequency in the Tohoku district. It is mainly caused by cold fronts that accompany cyclones passing north of the Japanese islands. Type B, which occurs most frequently in the coastal areas of the Hokuriku district, is mainly caused by topographically induced wind convergence and convective instability, both of which are associated with cyclones having multiple centers. Type C's lightning frequency distribution pattern is similar to that of type B, but its principal cause is a topographically induced wind convergence generated by cold air advection from the Siberian continent. Type A is most frequently observed from October to November, while types B and C tend to appear from November to January, consistent with seasonal changes in lightning frequency distribution in Japan's Tohoku and Hokuriku districts.

The North Korean missile program: How advanced is it?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, D.; Kadyshev, T.

1994-04-01

For the past three years there have been increasing numbers of reports that North Korea is developing a 1,000-1,300-kilometer range missile generally referred to as the NoDongg-1. Pyongyang`s missile program has generated international concern because of North Korea`s potential nuclear capabilities, its proximity to South Korea and Japan and its reported missile sales to Iran, Syria and Libya. In June 1993, Japanese and South Korean wire services reported that North Korea had test fired several missiles into the Sea of Japan in late May, at least two of which were though to be NoDong-1 missiles. A missile with a 1,300-kilometermore » range would give North Korea the capability to reach all of Japan, and give Iran and Libya the capability to reach all of Israel.« less

Changes in size and trends of North American sea duck populations associated with North Pacific oceanic regime shifts

USGS Publications Warehouse

Flint, Paul L.

2013-01-01

Broad-scale multi-species declines in populations of North American sea ducks for unknown reasons is cause for management concern. Oceanic regime shifts have been associated with rapid changes in ecosystem structure of the North Pacific and Bering Sea. However, relatively little is known about potential effects of these changes in oceanic conditions on marine bird populations at broad scales. I examined changes in North American breeding populations of sea ducks from 1957 to 2011 in relation to potential oceanic regime shifts in the North Pacific in 1977, 1989, and 1998. There was strong support for population-level effects of regime shifts in 1977 and 1989, but little support for an effect of the 1998 shift. The continental-level effects of these regime shifts differed across species groups and time. Based on patterns of sea duck population dynamics associated with regime shifts, it is unclear if the mechanism of change relates to survival or reproduction. Results of this analysis support the hypothesis that population size and trends of North American sea ducks are strongly influenced by oceanic conditions. The perceived population declines appear to have halted >20 years ago, and populations have been relatively stable or increasing since that time. Given these results, we should reasonably expect dramatic changes in sea duck population status and trends with future oceanic regime shifts.

Spatial sensitivity of inorganic carbon to model setup: North Sea and Baltic Sea with ECOSMO

NASA Astrophysics Data System (ADS)

Castano Primo, Rocio; Schrum, Corinna; Daewel, Ute

2015-04-01

In ocean biogeochemical models it is critical to capture the key processes adequately so they do not only reproduce the observations but that those processes are reproduced correctly. One key issue is the choice of parameters, which in most cases are estimates with large uncertainties. This can be the product of actual lack of detailed knowledge of the process, or the manner the processes are implemented, more or less complex. In addition, the model sensitivity is not necessarily homogenous across the spatial domain modelled, which adds another layer of complexity to biogeochemical modelling. In the particular case of the inorganic carbon cycle, there are several sets of carbonate constants that can be chosen. The calculated air-sea CO2 flux is largely dependent on the parametrization chosen. In addition, the different parametrizations all the underlying processes that in some way impact the carbon cycle beyond the carbonate dissociation and fluxes give results that can be significantly different. Examples of these processes are phytoplankton growth rates or remineralization rates. Despite their geographical proximity, the North and Baltic Seas exhibit very different dynamics. The North Sea receives important inflows of Atlantic waters, while the Baltic Sea is an almost enclosed system, with very little exchange from the North Sea. Wind, tides, and freshwater supply act very differently, but dominantly structure the ecosystem dynamics on spatial and temporal scales. The biological community is also different. Cyanobacteria, which are important due to their ability to fix atmospheric nitrogen, and they are only present in the Baltic Sea. These differentiating features have a strong impact in the biogeochemical cycles and ultimately shape the variations in the carbonate chemistry. Here the ECOSMO model was employed on the North Sea and Baltic Sea. The model is set so both are modelled at the same time, instead of having them run separately. ECOSMO is a 3-D coupled

The 14 month wind stressed residual circulation (pole tide) in the North Sea

NASA Technical Reports Server (NTRS)

Oconnor, W. P.

1986-01-01

From published research it is known that a quasi-periodic 14 month atmospheric pressure oscillation of a few tenths of a millibar exists in the region of the North and Baltic Seas. At some time in the cycle the associated wind stress has a westerly component that drives a circulation in the North Sea. The results of a dynamical model and comparisons with several North Sea residual circulation studies show that a large sea level gradient results along the Dutch coast. It is this feature that has been referred to as the enhanced pole tide. The dynamical similarity of this pole tide in the North and Baltic Seas to the annual and seasonal wind forced circulations is considered. It is inferred that the large deviations of the pole tide from equilibrium at coastal stations are the result of this sea level set up forces by the 14 month wind stress cycle.

Seasonal distribution of Gambierdiscus spp. in Wakasa Bay, the Sea of Japan, and antagonistic relationships with epiphytic pennate diatoms.

PubMed

Nakada, Mitsutaka; Hatayama, Yuki; Ishikawa, Akira; Ajisaka, Tetsuro; Sawayama, Shigeki; Imai, Ichiro

2018-06-01

The occurrence of the ciguatera fish poisoning (CFP) causative Gambierdiscus spp. was confirmed in the Sea of Japan for the first time in 2009. This paper reports seasonal distribution of Gambierdiscus spp. and epiphytic diatoms in the Sea of Japan. Monitoring results suggested an antagonistic interaction in abundances between epiphytic diatoms and the dinoflagellate Gambierdiscus spp. Allelopathic effects of diatoms were considered to be involved in the competitive phenomenon. Therefore it is hypothesized that cell densities of epiphytic pennate diatoms on macroalgae are a novel determinant affecting the abundance of Gambierdiscus spp. other than sea water temperature, salinity and nutrients. Monitorings of the abundance of epiphytic diatoms would lead us to predict the occurrences of Gambierdiscus spp. blooms in the CFP area, and thereby the CFP risk assessments would be developed. Phylogenetic analyses indicated that Gambierdiscus spp. in the Sea of Japan belonged to Gambierdiscus sp. type 2 which was reported to be non-toxic. Nevertheless, based on morphological characteristics, at least two types of Gambierdiscus spp. were found in the Sea of Japan. It is needed to test the toxicity of the both types of Gambierdiscus recognized in the present study for evaluation of the probability of CFP outbreak risks in the Sea of Japan in the future. Copyright © 2018 Elsevier B.V. All rights reserved.

Vietnam, the United States, and Japan in the South China Sea

DTIC Science & Technology

2014-10-01

Asia Pacific Center for Security Studies VIETNAM, THE UNITED STATES, AND JAPAN IN THE SOUTH CHINA SEA Dr. Alexander L. Vuving Paper for...since 1988. The standoff also served as a litmus test to identify who will side with whom in this conflict. While most of the world remained neutral...these actors relate to the South China Sea issue. This paper will focus on the three status quo powers; particularly, I will examine the strategies of

Estimating north pacific summer sea-level pressure back to 1600 using proxy climate records from China and North America

NASA Astrophysics Data System (ADS)

Wu, Xiangding; Lough, J. M.

1987-03-01

Sea-level pressure variations over the North Pacific Ocean influence the surface climate conditions of China and western North America. Documentary records of precipitation in China data back to the mid-15th century, and a well-replicated network of tree-ring chronologies from western North America dates to the early 17th century. These proxy climate records are used separately and together to estimate sea-level pressure variations over the North Pacific back to 1600 A.D. The models are calibrated over the period 1899 to 1950 and verified over the independent period, 1951 to 1963. The best estimates, derived from predictors in China and western North America, calibrate 44.7 % of summer sea-level pressure variance. The study demonstrates the potential of combining different proxy data sources to derive estimates of past climate.

Illicit drugs and their metabolites in 36 rivers that drain into the Bohai Sea and north Yellow Sea, north China.

PubMed

Wang, De-Gao; Zheng, Qiu-Da; Wang, Xiao-Ping; Du, Juan; Tian, Chong-Guo; Wang, Zhuang; Ge, Lin-Ke

2016-08-01

Illicit drugs and their metabolites have recently been recognized as an emerging group of contaminants due to their potential ecotoxicological impact in aquatic ecosystems. To date, information on the occurrence of these compounds in the aquatic environment of China remains limited. In this study, we collected surface water samples from 36 rivers in north China that discharge into the Bohai Sea and north Yellow Sea and measured the concentrations of amphetamine-like compounds, ketamines, cocainics, and opioids. The occurrence and spatial patterns of these substances show significant differences between the rivers and regions. Two designer drugs, methamphetamine (METH) and ketamine (KET), were the most abundant compounds detected in the entire set of samples (detection frequency of 92 and 69 %). The concentrations of METH and KET ranged from <0.1 to 42.0 ng L(-1) (mean = 4.53 ng L(-1)) and <0.05 to 4.50 ng L(-1) (mean = 0.49 ng L(-1)), respectively. The high detection frequencies of METH and KET are consistent with the fact that they are the main illicit drugs consumed in China. The high concentrations of these illicit drugs and their metabolites were found in areas that have a high population density. The riverine input of total illicit drugs into the Bohai Sea and north Yellow Sea was estimated to be in the range of 684 to 1160 kg per year.

Holocene sea-level change and Antarctic melting history derived from geological observations and geophysical modeling along the Shimokita Peninsula, northern Japan

NASA Astrophysics Data System (ADS)

Yokoyama, Yusuke; Okuno, Jun'ichi; Miyairi, Yosuke; Obrochta, Stephen; Demboya, Nobuhiro; Makino, Yoshinori; Kawahata, Hodaka

2012-07-01

A Mid to Late Holocene sea-level record based on combined geomorphological, geological and micropaleontological observations was obtained from well-developed wave cut benches subaerially exposed along the Shimokita Peninsula, northern Japan. Results indicate that the benches were formed during mid to late Holocene sea-level transgressions, reaching a maximum highstand level of 2 m above present at about 4,000 years ago. This timing corresponds to an abrupt, order of magnitude decrease in sedimentation rate as recorded in a core recovered from proximal Mutsu Bay. In addition, glacio-hydro-isostatic adjustment due to crustal deformation in response to postglacial sea-level rise was modeled, and results are consistent with the reconstructed local 2 m highstand. Given that meltwater contributions from the major North American and European ice sheets had largely ceased by 7,000 years ago, these independent lines of evidence, taken together, indicate that melting of the Antarctic ice sheet ended by 4,000 years ago.

Holocene sea-level change and Antarctic melting history derived from geological observations and geophysical modeling along the Shimokita Peninsula, northern Japan

NASA Astrophysics Data System (ADS)

Yokoyama, Y.; Okuno, J.; Miyairi, Y.; Obrochta, S.; Demboya, N.; Makino, Y.; Kawahata, H.

2012-12-01

A Mid to Late Holocene sea-level record based on combined geomorphological, geological and micropaleontological observations was obtained from well-developed wave cut benches subaerially exposed along the Shimokita Peninsula, northern Japan. Results indicate that the benches were formed during mid to late Holocene sea-level transgressions, reaching a maximum highstand level of 2 m above present at about 3,000 to 4,000 years ago. This timing corresponds to an abrupt, order of magnitude decrease in sedimentation rate as recorded in a core recovered from proximal Mutsu Bay. In addition, glacio-hydro-isostatic adjustment due to crustal deformation in response to postglacial sea-level rise was modeled, and results are consistent with the reconstructed local 2 m highstand. Given that meltwater contributions from the major North American and European ice sheets had largely ceased by 7,000 years ago, these independent lines of evidence, taken together, indicate that melting of the Antarctic ice sheet ended by late Holocene, around 3,000-4,000 years ago.

Modification of misovortices during landfall in the Japan Sea coastal region

NASA Astrophysics Data System (ADS)

Kato, Ryohei; Kusunoki, Kenichi; Inoue, Hanako Y.; Arai, Ken-ichiro; Nishihashi, Masahide; Fujiwara, Chusei; Shimose, Ken-ichi; Mashiko, Wataru; Sato, Eiichi; Saito, Sadao; Hayashi, Syugo; Yoshida, Satoru; Suzuki, Hiroto

2015-05-01

Misovortices frequently occur near the coastline of the Japan Sea during wintertime cold air outbreaks, generally developing over the sea and moving inland. To clarify the behavior of misovortices during landfall, temporal changes in the intensity and tilt of 12 misovortices over the coastal region of the Japan Sea were investigated during the winters of 2010/11 and 2011/12 using an X-band Doppler radar. For 11 vortices whose diameters were more than twice the effective radar beamwidth, the temporal change in the peak tangential velocity at lower levels (averaged below 400 m AGL) was analyzed. It was found that 8 out of the 11 vortices decreased after progressing between 0 and 6 km inland. For the remaining three vortices, the patterns of Doppler velocity couplet became unclear between 0 and 5 km inland, suggesting that these vortices also decayed soon after landfall. For four of the vortices, for which the analysis of the temporal evolution of tilt with height was made possible by several successive volume scans, the forward tilt with height increased after landfall. This study showed that modification to both the intensity and tilt with height of misovortices occurred after landfall.

What Causes the North Sea Level to Rise Faster over the Last Decade ?

NASA Astrophysics Data System (ADS)

Karpytchev, Mikhail; Letetrel, Camille

2013-04-01

We combined tide gauge records (PSMSL) and satellite altimetry data (TOPEX/POSEIDON-JASON 1-2) to reconstruct the mean level of the North Sea and the Norwegian Sea Shelf (NS-NSS) over 1950-2012. The reconstructed NS-NSS mean sea level fluctuations reveal a pronounced interannual variability and a strong sea level acceleration since the mid-1990's. In order to understand the causes of this acceleration, the NS-NSS mean sea level was cross-correlated with the North Atlantic Oscillation and Arctic Oscillation indices. While the interannual variability of the mean sea level correlates well with the NAO/AO indices, the observed acceleration in the NS-NSS mean level is not linked linearly to the NAO/AO fluctuations. On the other hand, the Empirical Orthogonal Functions (EOF) analysis of steric sea level variations in the eastern North Atlantic gives a dominant EOF pattern (55% of variance explained) that varies on a decadal scale very closely to the NS-NSS mean level flcutuations. Also, the amplification in the temporal amplitude of the dominant steric sea level EOF corresponds to the acceleration observed in the NS-NSS mean sea level signal. This suggests that decadal variations in the mean level of the North Sea - the Norwegian Sea Shelf reflect changes in the Subpolar Front currents (Rossby, 1996).

Late Quaternary tephrostratigraphy of Baegdusan and Ulleung volcanoes using marine sediments in the Japan Sea/East Sea

NASA Astrophysics Data System (ADS)

Lim, Chungwan; Toyoda, Kazuhiro; Ikehara, Ken; Peate, David W.

2013-07-01

Only Ulleung and Baegdusan volcanoes have produced alkaline tephras in the Japan Sea/East Sea during the Quaternary. Little is known about their detailed tephrostratigraphy, except for the U-Oki and B-Tm tephras. Trace element analysis of bulk sediments can be used to identify alkaline cryptotephra because of the large compositional contrast. Five sediment cores spanning the interval between the rhyolitic AT (29.4 ka) and Aso-4 (87 ka) tephras were analyzed using an INAA scanning method. Source volcanoes for the five detected alkaline cryptotephra were identified from major element analyses of hand-picked glass shards: Ulleung (U-Ym, and the newly identified U-Sado), and Baegdusan (B-J, and the newly identified B-Sado and B-Ym). The eruption ages of the U-Ym, U-Sado, B-J, B-Sado, and B-Ym tephras are estimated to be 38 ka, 61 ka, 26 ka, 51 ka, 68-69 ka, and 86 ka, respectively, based on correlations with regional-scale TL (thinly laminated) layer stratigraphy (produced by basin-wide changes in bottom-water oxygen levels in response to millennium-scale paleoclimate variations). This study has allowed construction of an alkaline tephrostratigraphical framework for the late Quaternary linked to global environmental changes in the Japan Sea/East Sea, and improves our knowledge of the eruptive histories of Ulleung and Baegdusan volcanoes.

North Sea Emerald crude oil assayed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rhodes, A.K.

1991-09-16

This book reports on an analysis of crude from Emerald field, 70 miles east of the Shetland Islands in the British North Sea, which shows that the crude is much heavier than typical North Sea crude. Elements of the long- delayed project appear to be in place, but production has not yet begun. Plans calls for producing the field at a rate of 30,000-40,000 b/d from a floating storage unit. Sovereign Oil and Gas plc has completed and fully tested seven production wells and four injectors in the marginal Emerald oil field. All flow lines are in place and themore » floating storage unit is ready to be installed. Production from Emerald will be sold to Neste Oy of Finland, at a minimum price of $17.90/bbl for Sullom Voe. Increases in spot prices above that level will be shared equally by the owners and purchaser.« less

A tracer study of ventilation in the Japan/East Sea

NASA Astrophysics Data System (ADS)

Postlethwaite, C. F.; Rohling, E. J.; Jenkins, W. J.; Walker, C. F.

2005-06-01

During the Circulation Research in East Asian Marginal Seas (CREAMS) summer cruises in 1999, a suite of samples was collected for tracer analysis. Oxygen isotopes combined with tritium-helium ventilation timescales and noble gas measurements give unique insights into the ventilation of water masses in the Japan/East Sea (JES). In particular, noble gases and oxygen isotopes are indicators of brine rejection, which may assist in explaining the recent changes observed in the ventilation of the JES. Oxygen isotope data presented here indicate that both thermally driven convection and brine rejection have played significant roles in deep-water formation but that brine rejection is unlikely to be a significant contributor at the moment. A 6-box ventilation model of the JES, calibrated with tritium and helium-3 measurements, performed better when a significant decrease of dense-water formation rates in the mid-1960s was incorporated. However, the model calculations suggest that Japan Sea Intermediate Water formation is still occurring. Subduction of sea-ice melt water may be a significant ventilation mechanism for this water mass, based on an argon saturation minimum at the recently ventilated salinity minimum in the northwestern sector of the JES. The salinity and oxygen isotope budgets imply a potential bottom-water formation rate of 3.97±0.89×10 12 m 3 yr -1 due to brine rejection, which could account for a time averaged fraction of between 25% and 35% of the ventilation of subsurface water formation in the JES.

Submarine basaltic fountain eruptions in a back-arc basin during the opening of the Japan Sea

NASA Astrophysics Data System (ADS)

Hosoi, Jun; Amano, Kazuo

2017-11-01

Basaltic rock generated during the middle Miocene opening of the Japan Sea, is widely distributed on the back-arc side of the Japanese archipelago. Few studies have investigated on submarine volcanism related to opening of the Japan Sea. The present study aimed to reconstruct details of the subaqueous volcanism that formed the back-arc basin basalts (BABB) during this event, and to discuss the relationship between volcanism and the tectonics of back-arc opening, using facies analyses based on field investigation. The study area of the southern Dewa Hills contains well-exposed basalt related to the opening of the Japan Sea. Five types of basaltic rock facies are recognized: (1) coherent basalt, (2) massive platy basalt, (3) jigsaw-fit monomictic basaltic breccia, (4) massive or stratified coarse monomictic basaltic breccia with fluidal clasts, and (5) massive or stratified fine monomictic basaltic breccia. The basaltic rocks are mainly hyaloclastite. Based on facies distributions, we infer that volcanism occurred along fissures developed mainly at the center of the study area. Given that the rocks contain many fluidal clasts, submarine lava fountaining is inferred to have been the dominant eruption style. The basaltic rocks are interpreted as the products of back-arc volcanism that occurred by tensional stress related to opening of the Japan Sea, which drove strong tectonic subsidence and active lava fountain volcanism.

Concentration of iodine-129 in surface seawater at subarctic and subtropical circulations in the Japan Sea

NASA Astrophysics Data System (ADS)

Suzuki, Takashi; Otosaka, Shigeyoshi; Togawa, Orihiko

2013-01-01

To investigate the migration of anthropogenic 129I in the environment, we measured 129I concentrations at both subarctic (above 40oN) and subtropical (below 40oN) circulations in the surface seawater of the Japan Sea. The averaged concentrations of stations 193, 194, 201, 206 and 210 above 200 m were (2.1 ± 0.3) × 1010 atoms/m3, (2.0 ± 0.2) × 1010 atoms/m3, (1.6 ± 0.3) × 1010 atoms/m3, (1.4 ± 0.3) × 1010 atoms/m3 and (1.7 ± 0.3) × 1010 atoms/m3, respectively. The averaged concentration at the subarctic circulation in the Japan Sea above 200 m (1.9 × 1010 atoms/m3) was higher than that in the subtropical circulation (1.5 × 1010 atoms/m3). This latitudinal distribution pattern of 129I is not consistent with those of bomb-derived radionuclides such as 14C, 90Sr and 137Cs. Taking into account latitudinal location and the total amount of releases from reprocessing plants, this discriminating latitudinal distribution of 129I in the Japan Sea would indicate that a significant amount of 129I originating from active reprocessing plants in Europe is supplied to the surface of the Japan Sea.

DUPAL anomaly in the Sea of Japan: Pb, Nd, and Sr isotopic variations at the eastern Eurasian continental margin

USGS Publications Warehouse

Tatsumoto, M.; Nakamura, Y.

1991-01-01

Volcanic rocks from the eastern Eurasian plate margin (southwestern Japan, the Sea of Japan, and northeastern China) show enriched (EMI) component signatures. Volcanic rocks from the Ulreung and Dog Islands in the Sea of Japan show typical DUPAL anomaly characteristics with extremely high ??208/204 Pb (up to 143) and enriched Nd and Sr isotopic compositions (??{lunate}Nd = -3 to -5, 87Sr 86Sr = ~0.705). The ??208/204 Pb values are similar to those associated with the DUPAL anomaly (up to 140) in the southern hemisphere. Because the EMI characteristics of basalts from the Sea of Japan are more extreme than those of southwestern Japan and inland China basalts, we propose that old mantle lithosphere was metasomatized early (prior to the Proterozoic) with subduction-related fluids (not present subduction system) so that it has been slightly enriched in incompatible elements and has had a high Th/U for a long time. The results of this study support the idea that the old subcontinental mantle lithosphere is the source for EMI of oceanic basalts, and that EMI does not need to be stored at the core/ mantle boundary layer for a long time. Dredged samples from seamounts and knolls from the Yamato Basin Ridge in the Sea of Japan show similar isotopic characteristics to basalts from the Mariana arc, supporting the idea that the Yamato Basin Ridge is a spreading center causing separation of the northeast Japan Arc from Eurasia. ?? 1991.

Lagrangian study of transport of subarctic water across the Subpolar Front in the Japan Sea

NASA Astrophysics Data System (ADS)

Prants, Sergey V.; Uleysky, Michael Yu.; Budyansky, Maxim V.

2018-06-01

The southward near-surface transport of transformed subarctic water across the Subpolar Front in the Japan Sea is simulated and analyzed based on altimeter data from January 1, 1993 to December 31, 2017. Computing Lagrangian indicators for a large number of synthetic particles, advected by the AVISO velocity field, we find preferred transport pathways across the Subpolar Front. The southward transport occurs mainly in the central part of the frontal zone due to suitable dispositions of mesoscale eddies promoting propagation of subarctic water to the south. It is documented with the help of Lagrangian origin and L-maps and verified by the tracks of available drifters. The transport of transformed subarctic water to the south is compared with the transport of transformed subtropical water to the north simulated by Prants et al. (Nonlinear Process Geophys 24(1):89-99, 2017c).

Lagrangian study of transport of subarctic water across the Subpolar Front in the Japan Sea

NASA Astrophysics Data System (ADS)

Prants, Sergey V.; Uleysky, Michael Yu.; Budyansky, Maxim V.

2018-05-01

The southward near-surface transport of transformed subarctic water across the Subpolar Front in the Japan Sea is simulated and analyzed based on altimeter data from January 1, 1993 to December 31, 2017. Computing Lagrangian indicators for a large number of synthetic particles, advected by the AVISO velocity field, we find preferred transport pathways across the Subpolar Front. The southward transport occurs mainly in the central part of the frontal zone due to suitable dispositions of mesoscale eddies promoting propagation of subarctic water to the south. It is documented with the help of Lagrangian origin and L-maps and verified by the tracks of available drifters. The transport of transformed subarctic water to the south is compared with the transport of transformed subtropical water to the north simulated by Prants et al. (Nonlinear Process Geophys 24(1):89-99, 2017c).

An Inter-Cultural Comparative Study on Elementary Science Teachers' Perceptions of Their Behavior and Inservice Needs between Japan and North Carolina.

ERIC Educational Resources Information Center

Shimizu, Kinya

This study compared several facets of teacher education between Japan and North Carolina. Similarities and differences in elementary science teachers' perceptions of the academic backgrounds in Japan and North Carolina were evaluated as well as similarities and differences in elementary teachers' perceptions of classroom practices in Japan and…

Gradient measurements of gaseous elemental mercury (Hg0) in the marine boundary layer of the northwest Sea of Japan (East Sea).

PubMed

Kalinchuk, Viktor; Lopatnikov, Evgeny; Astakhov, Anatoly

2018-06-01

Gaseous elemental mercury (Hg 0 ) is a prolific and persistent contaminant in the atmosphere. Atmospheric concentrations of Hg 0 were determined from 17 September to 7 October 2015 in the northwest Sea of Japan aboard the Russian research vessel Professor Gagarinsky. Simultaneous measurements of Hg 0 concentrations were performed 2 m and 20 m above the sea surface using automatic Hg 0 analysers RA-915M and RA-915+, respectively. Concentrations ranged from 0.3 to 25.9 ng/m 3 (n = 5207) and from 0.3 to 27.8 ng/m 3 (n = 4415), with medians of 1.7 and 1.6 ng/m 3 , respectively. Elevated Hg 0 was observed during three episodes from 19 to 22 September, likely caused by one or more of the following factors: 1) atmospheric transport of Hg 0 from the west and south-west (from N. Korea, China, and the Yellow Sea region); 2) Hg 0 emission from the sea due to pollution by water from the Tumannaya River; or 3) underwater geological activities. Increased Hg 0 concentration was observed during periods when air masses flowed from the south, and low concentrations were observed when air masses came from the north. A daytime increase of Hg 0 concentrations at a height of 2 m occurred simultaneously with decreasing Hg 0 at a height of 20 m. These diurnal variations suggest that two contrasting processes occur during the daytime in the marine boundary layer (MBL): Hg 0 emission from the sea surface and Hg 0 oxidation in the MBL by active halogens formed by photolysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Diseases in North Sea fishes

NASA Astrophysics Data System (ADS)

Dethlefsen, V.

1984-03-01

Prior to the studies reviewed here, only lymphocystis and skeletal deformities of a variety of fish species and certain diseases of eel were known to occur in the German Bight (North Sea). From 1977 until now, 9 externally visible lesions on North Sea fishes were observed; in addition to those mentioned before, they comprise: fin rot, ulcerations, epidermal papilloma, hyperplasia, pseudobranchial tumour, eye diseases and gill swellings. With the exception of information on changes in frequencies of vertebral deformities of herring from the 1950's to the 1970's, there are no long-term data characterizing changes in frequencies of the diseases under study. For pseudobranchial tumours of cod and epidermal papilloma of dab, information is provided on occurrence and abundance. The distribution pattern of cod afflicted with pseudobranchial tumours is strongly influenced by the migratory behaviour of the fish. Epidermal papillomas of dab were more frequently found at stations within the inner German Bight than in neighbouring areas. The Bight is used for dumping of wastes from titaniumdioxide production. Further disease hot spots are areas off the Humber estuary and the British coast. Analysis of chromium in dab from the German Bight revealed elevated concentrations in epidermal tissues of specimens from the dumping area compared with that found in dab from neighbouring localities. Particulate iron was demonstrated to occur in mucous cells of dab from the dumping area. From increased levels of heavy metals with cancerogenic potential in sensitive target tissues and from increased prevalences of diseased fish in the dumping area it is concluded that these phenomena are possibly causally linked. In the vicinity of the Humber estuary high disease rates were encountered and areas with high prevalences of dab afflicted with epidermal papilloma extended over regions shown to be transport routes for persistent pollutants such as radioactive materials. It is therefore suggested

Enhancement of the surface methane hydrate-bearing layer based on the specific microorganisms form deep seabed sediment in Japan Sea.

NASA Astrophysics Data System (ADS)

Hata, T.; Yoneda, J.; Yamamoto, K.

2017-12-01

A methane hydrate-bearing layer located near the Japan Sea has been investigated as a new potential energy resource. In this study examined the feasibility of the seabed surface sediment strength located in the Japan Sea improvement technologies for enhancing microbial induced carbonate precipitation (MICP) process. First, the authors cultivated the specific urease production bacterium culture medium from this surface methane hydrate-bearing layer in the seabed (-600m depth) of Japan Sea. After that, two types of the laboratory test (consolidated-drained triaxial tests) were conducted using this specific culture medium from the seabed in the Japan Sea near the Toyama Prefecture and high urease activities bacterium named Bacillus pasteurii. The main outcomes of this research are as follows. 1) Specific culture medium focused on the urease production bacterium can enhancement of the urease activities from the methane hydrate-bearing layer near the Japan Sea side, 2) This specific culture medium can be enhancement of the surface layer strength, 3) The microbial induced carbonate precipitation process can increase the particle size compared to that of the original particles coating the calcite layer surface, 4) The mechanism for increasing the soil strength is based on the addition of cohesion like a cement stabilized soil.

The New Positioning Technology for Sea Recovery Operations in Japan

NASA Astrophysics Data System (ADS)

Shoji, Yasuhiro; Yoshida, Tetsuya; Fuke, Hideyuki; Iijima, Issei; Izutsu, Naoki; Kato, Yoichi; Matsuzaka, Yukihiko; Namiki, Michiyoshi; Sato, Takatoshi; Tamura, Keisuke; Toriumi, Michihiko; Kakehashi, Yuya; Mizuta, Eiichi

2012-07-01

In Japan which has few flat plain and high population density, it is very difficult to drop a balloon safely on to the land. Hence balloons launched from Japan have always been dropped on the sea. In order to recover the balloons and the gondolas floating on the sea surely and rapidly, and to keep the gondolas and ships safe, much efforts and innovations have been made. Ones of the important innovations are positioning buoys. A buoy attached on a balloon gondola floats independently after the splash down, and informs its position to the recovery team. We had developed some types of such buoys; `radio beacon buoy' transmits a pattern of radio signal to navigate the recovery boats to the gondola. Another type of the buoys, `GPS ARGOS buoy,' finds its position with the GPS and sends the information to the balloon base via ARGOS satellite communication network. These technologies had contributed so much to the sea recovery operations however they also had some limitations. Recently, a new positioning buoy with better performance has developed; `Iridium buoy' detects the position with the GPS, and informs it to the balloon base via the Iridium satellite communication network and the internet. The Iridium buoy provides the accurate position surely and immediately with good time resolution. Furthermore the information can be received by very common devices which can receive e-mails. Thanks to the new buoy, the balloon operation team can always know where the gondola is on the sea more precisely, more simultaneously and more easily. That enables the operation team to inform the gondola's location to the authorities concerned as well as the recovery team, which contributes to the safety of both of the gondola and the sea traffics. In this presentation, the Iridium Buoy will be introduced mainly. Also the overview of the present sea recovery operation with the buoy and the past operations will be mentioned

Re-initiation of bottom water formation in the East Sea (Japan Sea) in a warming world.

PubMed

Yoon, Seung-Tae; Chang, Kyung-Il; Nam, SungHyun; Rho, TaeKeun; Kang, Dong-Jin; Lee, Tongsup; Park, Kyung-Ae; Lobanov, Vyacheslav; Kaplunenko, Dmitry; Tishchenko, Pavel; Kim, Kyung-Ryul

2018-01-25

The East Sea (Japan Sea), a small marginal sea in the northwestern Pacific, is ventilated deeply down to the bottom and sensitive to changing surface conditions. Addressing the response of this marginal sea to the hydrological cycle and atmospheric forcing would be helpful for better understanding present and future environmental changes in oceans at the global and regional scales. Here, we present an analysis of observations revealing a slowdown of the long-term deepening in water boundaries associated with changes of water formation rate. Our results indicate that bottom (central) water formation has been enhanced (reduced) with more (less) oxygen supply to the bottom (central) layer since the 2000s. This paper presents a new projection that allows a three-layered deep structure, which retains bottom water, at least until 2040, contrasting previous results. This projection considers recent increase of slope convections mainly due to the salt supply via air-sea freshwater exchange and sea ice formation and decrease of open-ocean convections evidenced by reduced mixed layer depth in the northern East Sea, resulting in more bottom water and less central water formations. Such vigorous changes in water formation and ventilation provide certain implications on future climate changes.

Comparison of numerical hindcasted severe waves with Doppler radar measurements in the North Sea

NASA Astrophysics Data System (ADS)

Ponce de León, Sonia; Bettencourt, João H.; Dias, Frederic

2017-01-01

Severe sea states in the North Sea present a challenge to wave forecasting systems and a threat to offshore installations such as oil and gas platforms and offshore wind farms. Here, we study the ability of a third-generation spectral wave model to reproduce winter sea states in the North Sea. Measured and modeled time series of integral wave parameters and directional wave spectra are compared for a 12-day period in the winter of 2013-2014 when successive severe storms moved across the North Atlantic and the North Sea. Records were obtained from a Doppler radar and wave buoys. The hindcast was performed with the WAVEWATCH III model (Tolman 2014) with high spectral resolution both in frequency and direction. A good general agreement was obtained for integrated parameters, but discrepancies were found to occur in spectral shapes.

Interaction between Meso-scale Eddies and Sub-polar Front in the East (Japan) Sea based on ARGO, AVHRR, and Numerical Model

NASA Astrophysics Data System (ADS)

Ro, Y.; Kim, E.

2008-12-01

The East (Japan) Sea is drawing keen international attentions from broad spectrum of groups such as scientists, diplomats, and defense officers for its geopolitical situation, peculiar scientific assets recognized as miniature ocean. From physical oceanographic aspect, it is very rich with many features such as basin-wide circulation pattern, boundary currents, sub-polar front, meso-scale eddy activities and deep water formation. The circulation pattern in the East (Japan) Sea has been of major interests for its peculiar gyre, a western boundary current and its separation that resembles the currents such as Kuroshio and Gulf Stream. In relation to the gyre system in the East Sea, the formation of the East Korea Warm Current (EKWC) has brought up with many numerical experiments. Numerical experiments suggested a new idea to explain the formation of the EKWC in that the potential energy supply into the Ulleung Basin (UB) from the meso-scale eddy is a key process. This is closely linked with the baroclinic instability and the meandering of offshore component of Tsushima Warm Current. The UB has drawn attentions for its role of the formation of two major boundary currents, EKWC, North Korea Warm Current (NKCC), their interaction with the mesoscale UWE, watermass exchange between the Northern Japan Basin and UB. Numerical experiments along with hydrographic and other satellite datasets such as AVHRR, altimeter and ARGO profiles have been analyzed to understand the formation of the UWE. We found that the influence of the bottom topography and frictional forcing against lateral boundary are all closely associated with the sub-polar front. Meandering of the axis of the sub-polar front is closely linked with the separation point of the EKWC, Ulleung Warm Eddy, and other small and meso-scale eddies on the sub-polar front. These will be demonstrated with results of the numerical modeling experiments and animation movie will be presented.

Helicopter support of North Sea oil exploration.

PubMed

Preston, F S

1978-04-01

Exploration for oil beneath the North Sea started in the early 1960's with the discovery of natural gas and oil in the southern part between the coasts of East Anglia and the Netherlands. Since then oil exploration has built up considerably, the main effort moving northwards between the Shetland Islands and the Norwegian coasts. The helicopter offered the most direct and rapid contact with off-shore oil rigs and since these early days and immense helicopter operation has been built up round the borders of the North Sea by all the nations involved. Flying conditions in this area, particularly in winter, are at times difficult if not to say hazardous. Nevertheless, a sophisticated helicopter support service has been built up using modern aircraft and equipment which is unique in aviation history. This paper attempts to trace the history of the service, the operational problems involved and the special needs such as survival equipment and clothing. In addition, a co-ordinated air/sea rescue service largely based on helicopters has been built up and provides not only rescue facilities for possible rig disasters but also for shipping emergencies in the area.

Mantle wedge structure beneath the Yamato Basin, southern part of the Japan Sea, revealed by long-term seafloor seismic observations

NASA Astrophysics Data System (ADS)

Shinohara, M.; Nakahigashi, K.; Yamashita, Y.; Yamada, T.; Mochizuki, K.; Shiobara, H.

2016-12-01

The Japanese Islands are located at subduction zones where Philippine Sea (PHS) plate subducts from the southeast beneath the Eurasian plate and the Pacific plate descends from the east beneath the PHS and Eurasian plates and have a high density of seismic stations. Many seismic tomography studies using land seismic station data were conducted to reveal the seismic structure. These studies discussed the relationship between heterogeneous structures and the release of fluids from the subducting slab, magma generation and movement in the subduction zone. However, regional tomography using the land station data did not have a sufficient resolution to image a deep structure beneath the Japan Sea.To obtain the deep structure, observations of natural earthquakes within the Japan Sea are essential. Therefore, we started the repeating long-term seismic observations using ocean bottom seismometers(OBSs) in the Yamato Basin from 2013 to 2016. We apply travel-time tomography method to the regional earthquake and teleseismic arrival-data recorded by OBSs and land stations. In this presentation, we will report the P and S wave tomographic images down to a depth of 300 km beneath the southern part of the Japan Sea. This study was supported by "Integrated Research Project on Seismic and Tsunami Hazards around the Sea of Japan" conducted by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan.

Decadal sea level variability in the East China Sea linked to the North Pacific Gyre Oscillation

NASA Astrophysics Data System (ADS)

Moon, Jae-Hong; Song, Y. Tony

2017-07-01

In view of coastal community's need for adapting to sea level rise (SLR), understanding and predicting regional variability on decadal to longer time scales still remain a challenging issue in SLR research. Here, we have examined the low-frequency sea level signals in the East China Sea (ECS) from the 50-year hindcast of a non-Boussinesq ocean model in comparison with data sets from altimeters, tide-gauges, and steric sea level produced by in-situ profiles. It is shown that the mean sea levels in the ECS represent significant decadal fluctuations over the past 50 years, with a multi-decadal trend shift since the mid-1980s compared to the preceding 30 years. The decadal fluctuations in sea level are more closely linked to the North Pacific Gyre Oscillation (NPGO) rather than the Pacific Decadal Oscillation, which reflects the multi-decadal trend shift. A composite analysis indicates that wind patterns associated with the NPGO is shown to control the decadal variability of the western subtropical North Pacific. A positive NPGO corresponds to cyclonic wind stress curl anomaly in the western subtropical regions that results in a higher sea level in the ECS, particularly along the continental shelf, and lower sea levels off the ECS. The reverse occurs in years of negative NPGO.

Variability and connectivity of plaice populations from the Eastern North Sea to the Baltic Sea, part II. Biological evidence of population mixing

NASA Astrophysics Data System (ADS)

Ulrich, Clara; Hemmer-Hansen, Jakob; Boje, Jesper; Christensen, Asbjørn; Hüssy, Karin; Sun, Hailu; Clausen, Lotte Worsøe

2017-02-01

A multi-disciplinary study was conducted to clarify stock identity and connectivity patterns in the populations of European plaice (Pleuronectes platessa) in the Skagerrak-Kattegat transition area between the Eastern North Sea and the Baltic Sea. Five independent biological studies were carried out in parallel. Genetic markers suggested the existence of different genetic populations in the transition area. Growth backcalculation with otoliths resulted in significant although limited differences in growth rates between North Sea and Skagerrak, indicating weak differentiation or important mixing. Hydrogeographical drift modelling suggested that some North Sea juveniles could settle along the coast line of the Skagerrak and the Kattegat. Tagging data suggested that both juveniles and adult fish from the North Sea perform feeding migrations into Skagerrak in summer/autumn. Finally, survey data suggested that Skagerrak also belongs to the area distribution of North Sea plaice. The outcomes of the individual studies were then combined into an overall synthesis. The existence of some resident components was evidenced, but it was also demonstrated that North Sea plaice migrate for feeding into Skagerrak and might constitute a large share of the catches in this area. The mixing of different populations within a management area has implications for stock assessment and management. Choice must be made to either lump or split the populations, and the feasibility and constraints of both options are discussed. The outcomes of this work have directly influenced the management decisions in 2015.

Persistent organochlorine pesticides and polychlorinated biphenyls in air of the North Sea region and air-sea exchange.

PubMed

Mai, Carolin; Theobald, Norbert; Hühnerfuss, Heinrich; Lammel, Gerhard

2016-12-01

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were studied to determine occurrence, levels and spatial distribution in the marine atmosphere and surface seawater during cruises in the German Bight and the wider North Sea in spring and summer 2009-2010. In general, the concentrations found in air are similar to, or below, the levels at coastal or near-coastal sites in Europe. Hexachlorobenzene and α-hexachlorocyclohexane (α-HCH) were close to phase equilibrium, whereas net atmospheric deposition was observed for γ-HCH. The results suggest that declining trends of HCH in seawater have been continuing for γ-HCH but have somewhat levelled off for α-HCH. Dieldrin displayed a close to phase equilibrium in nearly all the sampling sites, except in the central southwestern part of the North Sea. Here atmospheric deposition dominates the air-sea exchange. This region, close to the English coast, showed remarkably increased surface seawater concentrations. This observation depended neither on riverine input nor on the elevated abundances of dieldrin in the air masses of central England. A net depositional flux of p,p'-DDE into the North Sea was indicated by both its abundance in the marine atmosphere and the changes in metabolite pattern observed in the surface water from the coast towards the open sea. The long-term trends show that the atmospheric concentrations of DDT and its metabolites are not declining. Riverine input is a major source of PCBs in the German Bight and the wider North Sea. Atmospheric deposition of the lower molecular weight PCBs (PCB28 and PCB52) was indicated as a major source for surface seawater pollution.

An Annual Cycle Of Currents Around Tsushima Island And Resulting Inflow Conditions In The Sea Of Japan

NASA Astrophysics Data System (ADS)

Perkins, H.; Teague, W. J.; Chang, K.-I.; Suk, M.-S.; Lee, J.-C.; Book, J. W.; Jacobs, G. A.

A ten-month long time series of current measurements has been made on two sections across Korea/Tsushima Strait, thus revealing most of an annual cycle of the Tsushima Current that flows into the Japan/East Sea. One section is southwest, the other north- east, of Tsushima Island, giving respectively conditions upstream and downstream of the Island. Along the bathymetric slope upstream of the Island, the current consists of a single, broad stream concentrated in mid-channel. Downstream, this single core is found to have separated into two branches, one on each of the Strait. Between these two near-coastal streams, in the apparent wake of the Island, currents are variable and lack a well-defined mean. This separation persisted during all seasons despite vari- ation in total transport by a factor of two, from 3.5 Sv in October 1999 to 1.7 Sv in January 2000, and despite changes from maximum to minimum stratification. Both branches of the divided current were stronger during high transport and weaker during low transport, but since each branch was measured by only one or two moorings, trans- port estimates for the separate branches are not available. Strongest currents occurred at the surface close to the Korean coast near Ulsan in early fall with low-pass surface currents reaching 90 cm/s during October and November. Farther downstream, outside the measurement area, the two branches define the inflow to the Japan/East Sea. The branch along the Japanese coast remains close to the coast. It undergoes strong annual variability but is steady on shorter time scales. The Korean branch of the current also undergoes strong annual changes but experiences very strong variability, especially in winter. This branch is thought to switch between two paths. The first parallels the Ko- rean coast; the second follows bathymetric contours that lead it back to the Japanese coast. A mechanism for switching between these paths is provided by vorticity asso- ciated with bottom intrusions

Temperature affects the timing of spawning and migration of North Sea mackerel

NASA Astrophysics Data System (ADS)

Jansen, Teunis; Gislason, Henrik

2011-01-01

Climate change accentuates the need for knowing how temperature impacts the life history and productivity of economically and ecologically important species of fish. We examine the influence of temperature on the timing of the spawning and migrations of North Sea Mackerel using data from larvae CPR surveys, egg surveys and commercial landings from Danish coastal fisheries in the North Sea, Skagerrak, Kattegat and inner Danish waters. The three independent sources of data all show that there is a significant relationship between the timing of spawning and sea surface temperature. Large mackerel are shown to arrive at the feeding areas before and leave later than small mackerel and the sequential appearance of mackerel in each of the feeding areas studied supports the anecdotal evidence for an eastward post-spawning migration. Occasional commercial catches taken in winter in the Sound N, Kattegat and Skagerrak together with catches in the first quarter IBTS survey furthermore indicate some overwintering here. Significant relationships between temperature and North Sea mackerel spawning and migration have not been documented before. The results have implications for mackerel resource management and monitoring. An increase in temperature is likely to affect the timing and magnitude of the growth, recruitment and migration of North Sea mackerel with subsequent impacts on its sustainable exploitation.

Surfactant control of air-sea gas exchange from North Sea coastal waters and the Atlantic Meridional Transect

NASA Astrophysics Data System (ADS)

Pereira, R.

2016-02-01

Suppression of gas transfer velocity (kw) by surfactants are well established, both in laboratory wind flumes and purposeful oceanic releases. However, the effects on kw of time and space varying concentrations of natural surfactant are inadequately studied. We have developed an automated gas exchange tank for simultaneous high precision measurement of kw in unmodified seawater samples. Here we present data from two studies along a coastal North Sea transect during 2012-2013 and the Atlantic Meridional Transect (AMT) 24 from September to November 2014. Measurements of surfactant activity (SA), CDOM absorbance and chlorophyll-a have enabled us to characterize the effects of variable amounts of natural surfactant on kw. North Sea coastal waters range in k660 (kw normalized to the value for CO2 in freshwater at 20oC) was 6.8-24.5 cm hr-1 (n=20), with the ranges of SA, total CDOM absorbance (200-450 nm) and chlorophyll-a measured in the surface microlayer (SML) of our seawater samples were 0.08-0.38 mg l-1 T-X-100, 0.13-4.7 and 0.09-1.54 µg l-1, respectively. The AMT k660 ranged from 7.0-23.9 cm hr-1 (n=22), with SA measured in the SML and subsurface water (SSW) of our seawater samples ranging from 0.15-1.08 mg l-1 T-X-100 and 0.07-0.43 mg l-1 T-X-100, respectively. Importantly, we found 12-45% (North Sea) and 1-43% (AMT) k660 suppression relative to Milli-Q water that relate to seasonal and spatial differences in SA. The North Sea demonstrated notable seasonal influences on k660 suppression that were related to CDOM absorbance and chlorophyll-a. The degree of k660 suppression was highest in summer consistent with k660 control by natural surfactant. The degree of k660 suppression decreased with distance offshore in the North Sea and displayed a strong relationship with SA (r2 = 0.51-0.64, p = 0.02, n = 20). The AMT demonstrated notable differences in k660 suppression between hemispheres and across the Longhurst Provinces but the overall relationship between k660

Ecology of the North Sea: Problems, successes, failures, future needs

NASA Astrophysics Data System (ADS)

Kinne, O.

1995-03-01

After defining ‘ecology’, outlining the basic categories of ecological research and listing examples of modern ecological investigations, this introductory paper focusses on basic considerations; it is, in essence, a programmatic contribution. Research details on the ecology of the North Sea are the subject of the following papers. The problems of ecological North Sea research are formidable. Hydrological and biological fluctuations and variabilities are pronounced. Exchange patterns with the Atlantic are complex, and the inputs of rivers and rain defy exact measurement and prediction. Season, weather, climate—and as yet insufficiently known and controlled human-caused impacts—further complicate the situation. All this results in an unusually high degree of uncertainty. New questions and problems arise before the old ones can be answered or solved. Nevertheless, ecological North Sea research has achieved many successes. The North Sea is the most intensively investigated sea area on our planet. Generations of zoologists, botanists and hydrographers — and more recently microbiologists, meteorologists, climatologists, chemists, pathologists and toxicologists — have produced an impressive body of knowledge. Slowly we are beginning to understand the forces that govern energy budgets and balances, material fluxes, and the factors that control and direct ecosystem dynamics. Essential driving forces of ecosystem dynamics result from microbial, especially bacterial, activities. Ecological modelling has paved the way for new theories and insights, and holds promise for progress towards a predictive ecology. Failures and shortcomings include insufficient long-term research, inadequately designed experiments, and misconceptions in environmental protection. Net changes in ecological processes of an heterogeneous and intensely varying environment such as the North Sea can only be comprehended adequately against the background of sustained measurements over decades

Air-sea exchange fluxes of synthetic polycyclic musks in the North Sea and the Arctic.

PubMed

Xie, Zhiyong; Ebinghaus, Ralf; Temme, Christian; Heemken, Olaf; Ruck, Wolfgang

2007-08-15

Synthetic polycyclic musk fragrances Galaxolide (HHCB) and Tonalide (AHTN) were measured simultaneously in air and seawater in the Arctic and the North Sea and in the rural air of northern Germany. Median concentrations of gas-phase HHCB and AHTN were 4 and 18 pg m(-3) in the Arctic, 28 and 18 pg m(-3) in the North Sea, and 71 and 21 pg m(-3) in northern Germany, respectively. Various ratios of HHCB/AHTN implied that HHCB is quickly removed by atmospheric degradation, while AHTN is relatively persistent in the atmosphere. Dissolved concentrations ranged from 12 to 2030 pg L(-1) for HHCB and from below the method detection limit (3 pg L(-1)) to 965 pg L(-1) for AHTN with median values of 59 and 23 pg L(-1), respectively. The medians of volatilization fluxes for HHCB and AHTN were 27.2 and 14.2 ng m(-2) day(-1) and the depositional fluxes were 5.9 and 3.3 ng m(-2) day(-1), respectively, indicating water-to-air volatilization is a significant process to eliminate HHCB and AHTN from the North Sea. In the Arctic, deposition fluxes dominated the air-sea gas exchange of HHCB and AHTN, suggesting atmospheric input controls the levels of HHCB and AHTN in the polar region.

Virulence Profiles of Vibrio vulnificus in German Coastal Waters, a Comparison of North Sea and Baltic Sea Isolates.

PubMed

Bier, Nadja; Jäckel, Claudia; Dieckmann, Ralf; Brennholt, Nicole; Böer, Simone I; Strauch, Eckhard

2015-12-15

Vibrio vulnificus is a halophilic bacterium of coastal environments known for sporadically causing severe foodborne or wound infections. Global warming is expected to lead to a rising occurrence of V. vulnificus and an increasing incidence of human infections in Northern Europe. So far, infections in Germany were exclusively documented for the Baltic Sea coast, while no cases from the North Sea region have been reported. Regional variations in the prevalence of infections may be influenced by differences in the pathogenicity of V. vulnificus populations in both areas. This study aimed to compare the distribution of virulence-associated traits and genotypes among 101 V. vulnificus isolates from the Baltic Sea and North Sea in order to assess their pathogenicity potential. Furthermore, genetic relationships were examined by multilocus sequence typing (MLST). A high diversity of MLST sequences (74 sequence types) and differences regarding the presence of six potential pathogenicity markers were observed in the V. vulnificus populations of both areas. Strains with genotypes and markers associated with pathogenicity are not restricted to a particular geographic region. This indicates that lack of reported cases in the North Sea region is not caused by the absence of potentially pathogenic strains.

Virulence Profiles of Vibrio vulnificus in German Coastal Waters, a Comparison of North Sea and Baltic Sea Isolates

PubMed Central

Bier, Nadja; Jäckel, Claudia; Dieckmann, Ralf; Brennholt, Nicole; Böer, Simone I.; Strauch, Eckhard

2015-01-01

Vibrio vulnificus is a halophilic bacterium of coastal environments known for sporadically causing severe foodborne or wound infections. Global warming is expected to lead to a rising occurrence of V. vulnificus and an increasing incidence of human infections in Northern Europe. So far, infections in Germany were exclusively documented for the Baltic Sea coast, while no cases from the North Sea region have been reported. Regional variations in the prevalence of infections may be influenced by differences in the pathogenicity of V. vulnificus populations in both areas. This study aimed to compare the distribution of virulence-associated traits and genotypes among 101 V. vulnificus isolates from the Baltic Sea and North Sea in order to assess their pathogenicity potential. Furthermore, genetic relationships were examined by multilocus sequence typing (MLST). A high diversity of MLST sequences (74 sequence types) and differences regarding the presence of six potential pathogenicity markers were observed in the V. vulnificus populations of both areas. Strains with genotypes and markers associated with pathogenicity are not restricted to a particular geographic region. This indicates that lack of reported cases in the North Sea region is not caused by the absence of potentially pathogenic strains. PMID:26694432

Shallow gas in Cenozoic sediments of the Southern North Sea

NASA Astrophysics Data System (ADS)

Trampe, Anna F.; Lutz, Rüdiger; Franke, Dieter; Thöle, Hauke; Arfai, Jashar

2013-04-01

Shallow petroleum systems in the southern North Sea are known for several decades but they were not actively explored for a long time. In recent years these unconventional shallow petroleum systems are studied in greater detail and one shallow gas field (A-12) is in production in the Netherlands. Additionally, oil was encountered in Miocene sandstones in the southern Danish North Sea (Lille John well) just north of the Danish-German border. Seismic amplitude anomalies are an indication for hydrocarbons in sediments. Therefore we have mapped the occurrence of seismic amplitude anomalies in the German North Sea based on more than 25.000 km of 2D seismic data and around 4.000 km2 of 3D seismic data. Amplitude anomalies are ubiquitous phenomena in the study area. These anomalies are not only caused by hydrocarbons but also by changing lithologies e.g. peat or fluid migration. Therefore several classes of seismic anomalies, e.g. bright spots, chimneys, blanking areas and velocity pull-down were mapped. Examples for these classes were studied with AVO (amplitude variation with offset) analyses to verify the existence or non-existence of gas in the sediments. Shallow gas can be produced and transported through the dense pipeline grid of the southern and central North Sea or it could be burned offshore close to wind parks in small power plants and the electric energy then transported through the existing power connections of the wind parks. Thus enabling a continuous energy supply during calm wind periods. This study is carried out within the framework of the project "Geoscientific Potential of the German North Sea (GPDN)" in which the Cenozoic sedimentary system was mapped in great detail. A detailed model of delta evolution (Baltic river system) was developed which serves as a structural framework. The studied interval is time equivalent to the Utsira formation which is used offshore Norway for sequestration of CO2. These different possibilities of using or exploiting

A test of present-day plate geometries for northeast Asia and Japan

NASA Technical Reports Server (NTRS)

Demets, Charles

1992-01-01

Alternative geometries for the present-day configuration of plate boundaries in northeast Asia and Japan are tested using NUVEL-1 and 256 horizontal earthquake slip vectors from the Japan and northern Kuril trenches. Statistical analysis of the slip vectors is used to determine whether the North American, Eurasian, or Okhotsk plate overlies the trench. Along the northern Kuril trench, slip vectors are well-fit by the NUVEL-1 Pacific-North America Euler pole, but are poorly fit by the Pacific-Eurasia Euler pole. Results for the Japan trench are less conclusive, but suggest that much of Honshu and Hokkaido are also part of the North American plate. The simplest geometry consistent with the trench slip vectors is a geometry in which the North American plate extends south to 41 deg N, and possibly includes northern Honshu and southern Hokkaido. Although these results imply that the diffuse seismicity that connects the Lena River delta to Sakhalin Island and the eastern Sea of Japan records motion between Eurasia and North America, onshore geologic and seismic data define an additional belt of seismicity in Siberia that cannot be explained with this geometry. Assuming that these two seismic belts constitute evidence for an Okhotsk block, two published kinematic models for motion of the Okhotsk block are tested. The first model, which predicts motion of up to 15 mm/yr relative to North America, is rejected because Kuril and Japan trench slip vectors are fit more poorly than for the simpler geometry described above. The second model gives a good fit to the trench slip vectors, but only if Okhotsk-North America motion is slower than 5 mm/yr.

Ecology and conservation of North American sea ducks

USGS Publications Warehouse

Savard, Jean-Pierre L.; Derksen, Dirk V.; Esler, Daniel N.; Eadie, John M.

2015-01-01

Harvest history The book presents a comprehensive synthesis of sea duck ecology, documents factors that have caused population declines of some species, and provides managers with measures to enhance recovery of depressed populations of sea ducks in North America. Capturing the current state of knowledge of this unique tribe, it provides a benchmark for where we are in conservation efforts and suggests future directions for researchers, managers, students, conservationists, and avian enthusiasts.

A 21-Year Record of Arctic Sea Ice Extents and Their Regional, Seasonal, and Monthly Variability and Trends

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.; Cavalieri, Donald J.; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

Satellite passive-microwave data have been used to calculate sea ice extents over the period 1979-1999 for the north polar sea ice cover as a whole and for each of nine regions. Over this 21-year time period, the trend in yearly average ice extents for the ice cover as a whole is -32,900 +/- 6,100 sq km/yr (-2.7 +/- 0.5 %/decade), indicating a reduction in sea ice coverage that has decelerated from the earlier reported value of -34,000 +/- 8,300 sq km/yr (-2.8 +/- 0.7 %/decade) for the period 1979-1996. Regionally, the reductions are greatest in the Arctic Ocean, the Kara and Barents Seas, and the Seas of Okhotsk and Japan, whereas seasonally, the reductions are greatest in summer, for which season the 1979-1999 trend in ice extents is -41,600 +/- 12,900 sq km/ yr (-4.9 +/- 1.5 %/decade). On a monthly basis, the reductions are greatest in July and September for the north polar ice cover as a whole, in September for the Arctic Ocean, in June and July for the Kara and Barents Seas, and in April for the Seas of Okhotsk and Japan. Only two of the nine regions show overall ice extent increases, those being the Bering Sea and the Gulf of St. Lawrence.For neither of these two regions is the increase statistically significant, whereas the 1079 - 1999 ice extent decreases are statistically significant at the 99% confidence level for the north polar region as a whole, the Arctic Ocean, the Seas of Okhotsk and Japan, and Hudson Bay.

Rogue run-up events at the North Sea coast

NASA Astrophysics Data System (ADS)

Didenkulova, Ira; Blossier, Brice; Daly, Christopher; Herbst, Gabriel; Senichev, Dmitry; Winter, Christian

2015-04-01

On the 1st of January, 1995, the Statoil-operated "Draupner" platform located in the North Sea recorded the so-called "New Year wave". Since then, rogue waves have been the topic of active scientific discussions and investigations. Waves of extreme height appearing randomly at the sea surface have been measured in both deep and shallow waters and have been involved in a number of ship accidents. Nowadays rogue waves are frequently recorded all over the world with several different instruments (range finders installed on offshore platforms, deployed buoys, radars including SAR, etc.). Rogue wave also occur at the coast, where they appear as either sudden flooding of coastal areas or high splashes over steep banks or sea walls. These waves are especially dangerous for beach users and lead regularly to human injuries and fatalities. Despite numerous reports of human accidents, coastal rogue waves have not yet been recorded experimentally. In this paper we discuss the recording of rogue wave events at German North Sea coasts by using high-resolution beach cameras. The recorded rogue waves are observed during different tide levels and different weather conditions. Possible mechanisms of their generation are discussed.

Extreme Storm Surges in the North Sea

NASA Astrophysics Data System (ADS)

Goennert, G.; Buß, Th.; Mueller, O.; Thumm, S.

2009-04-01

Extreme Storm Surges in the North Sea Gabriele Gönnert, Olaf Müller, Thomas Buß and Sigrid Thumm Climate Change will cause a rise of the sea level and probably more frequent and more violent storm surges. This has serious consequences for the safety of people as well as for their values and assets behind the dikes. It is therefore inevitable to first assess how sea level rise and an extreme storm surge event designes. In a second step it is possible to determine the risk for specific locations and develop strategies. The Project XtremRisk - Extreme Storm Surges at the North Sea Coast and in Estuaries. Risk calculation and risk strategies, funded by the German Federal Government will help answering these questions. The „Source-Pathway-Receptor" Concept will be used as a basis for risk analysis and development of new strategies. The Project offers methods to assess the development of extreme events under the conditions of today. Under conditions reflecting the climate change it will be tried to design an extreme event. For these three main points will be considered: a) Analysis and calculation of each factor, which produce a storm surge and its maximum level occurring in the last 100 years. These are: - maximum surge level: surge (due to the wind), - influence of the tide and the interaction between surge and tide, - influence of external surges , b) The hydrodynamics of a storm surge cause nonlinear effects in the interaction of the named factors. These factors and effects will both be taken into account to calculate the magnitude of the extreme storm surge. This step is very complex and need additional examination by numerical models. c) Analysis of the different scenarios to mean sea level rise and to the increase of wind speed due to the climate change. The presentation will introduce methods and show first results of the analysis of extreme events and the mean sea level rise.

Physical processes in the transition zone between North Sea and Baltic Sea. Numerical simulations and observations

NASA Astrophysics Data System (ADS)

Stanev, Emil V.; Lu, Xi; Grashorn, Sebastian

2015-09-01

The dynamics in the transition zone between the North Sea and Baltic Sea are analyzed here using data from a 22-year-long climatic simulation with a focus on the periods 1992-1994 and 2001-2003 when two recent major inflow events occurred. Observations from gauges and in situ measurements are used to validate the model. Parameters, which cannot be easily measured, such as water and salt transports through straits, have been compared against similar previous estimates. The good performance of simulations is attributed to the finer resolution of the model compared to earlier set ups. The outflow in the Kattegat, which is an analogue of the tidal outflows, tends to propagate to the North over the shallows without showing a substantial deflection to the right due to the Earth's rotation. The inflow follows the topography. The different inflow and outflow pathways are explained as a consequence of the specific combination of bathymetry, axial and lateral processes. The circulation in Kattegat is persistently clockwise with an eastern intensification during inflow and a western one during outflow regimes. The tidal wave there propagates as Kelvin wave, keeping the coast on its right. The flows in the two main straits reveal very different responses to tides, which are also highly asymmetric during inflow and outflow conditions. The circulation has a typical two-layer structure, the correlation between salinity and velocity tends to increase the salt transport in the salinity conveyor belt. The transversal circulation in the entrance of the Sound enhances the vertical mixing of the saltier North Sea water. The long-term averaged ratio of the water transports through the Great Belt and the Sound is ∼2.6-2.7 but this number changes reaching lower values during the major inflow in 1993. The transports in the straits are asymmetric. During inflow events the repartition of water penetrating the Baltic Sea is strongly in favor of the pathway through the Sound, which provides

Murchison project organization and control. [North Sea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lauzen, P.K.; Hall, J.N.

This paper describes the project management organization and the management control systems used for Conoco's Murchison field development in the North Sea. These systems created for Murchison proved largely successful and have been enhanced for use during the Hutton field development. Management concepts are described in the context of the cost control system.

Comparing acoustic measurement data in eastern margin of Sea of Japan and Umitaka Spur

NASA Astrophysics Data System (ADS)

Kondo, M., IV; Aoyama, C.

2017-12-01

Recently, methane hydrate is gaining remarkable attention for the abundant amount in the sea area around Japan, and also for its carbon dioxide emission amount being as little as that of natural resources when being combusted. Two types of methane hydrates are known to exist, depending on the settings. Sand layer type methane hydrate contains sand particles and is extracted mainly in the Pacific Ocean, around 100 to 400m below seafloor. On the other hand, shallow type is found around 100m below seafloor in the Sea of Japan, in clumps, veins, and particles. One of the extraction methods of shallow type methane hydrate observed in the Sea of Japan is the seabed exploration system using acoustic equipment, which Chiharu Aoyama owns patent. Methane plumes often exist in the vicinity of shallow type methane hydrate and these seeping plumes are visualized as images on acoustic instruments such as quantitative echo sounder and multi-beam echo sounder (hereinafter referred to as MBES). These images look like rising beams on monitors and are called gas plumes. Methane hydrate can be explored effectively in the area using this method and it is understood that even when the same plume is examined, backscattering strength data (hereinafter referred as SV) observed using acoustic equipment will not be the same on quantitative echo sounder and MBES. In June 2017, measurement of acoustic data using multi-beam sonar (EM122) and quantitative echo sounder (EA600) were performed onboard DAIICHI KAIYOMARU (KAIYO ENGINEERING CO., LTD) at eastern margin of Sea of Japn and at Umitaka Spur. In this study, author will make comparisons of the acoustic data.

Levels and distribution of polybrominated diphenyl ethers and organochlorine compounds in sea turtles from Japan.

PubMed

Malarvannan, Govindan; Takahashi, Shin; Isobe, Tomohiko; Kunisue, Tatsuya; Sudaryanto, Agus; Miyagi, Toshihiko; Nakamura, Masaru; Yasumura, Shigeki; Tanabe, Shinsuke

2011-01-01

Three species of sea turtles (green, hawksbill and loggerhead turtles) stranded along the coasts or caught (by-catch) around Ishigaki Island and Kochi, Japan were collected between 1998 and 2006 and analyzed for six organohalogen compounds viz., PBDEs, PCBs, DDTs, CHLs, HCHs and HCB. The present study is the first and foremost to report the occurrence of organohalogen compounds in the sea turtles from Japan. Among the compounds analyzed, concentrations of PCBs, DDTs and CHLs were the highest in all the turtle samples. PBDEs were ubiquitously present in all the turtle species. Comparing with the other two species, concentrations of organohalogens in green turtle were relatively low and decreasing trend in the concentrations were noted with increasing carapace length. Concentrations of OCs in sea turtles from the coasts of Ishigaki Island and Kochi were relatively low as compared to those from other locations in the world. Copyright © 2011 Elsevier Ltd. All rights reserved.

Deglacial and Holocene sea-ice variability north of Iceland and response to ocean circulation changes

NASA Astrophysics Data System (ADS)

Xiao, Xiaotong; Zhao, Meixun; Knudsen, Karen Luise; Sha, Longbin; Eiríksson, Jón; Gudmundsdóttir, Esther; Jiang, Hui; Guo, Zhigang

2017-08-01

Sea-ice conditions on the North Icelandic shelf constitute a key component for the study of the climatic gradients between the Arctic and the North Atlantic Oceans at the Polar Front between the cold East Icelandic Current delivering Polar surface water and the relatively warm Irminger Current derived from the North Atlantic Current. The variability of sea ice contributes to heat reduction (albedo) and gas exchange between the ocean and the atmosphere, and further affects the deep-water formation. However, lack of long-term and high-resolution sea-ice records in the region hinders the understanding of palaeoceanographic change mechanisms during the last glacial-interglacial cycle. Here, we present a sea-ice record back to 15 ka (cal. ka BP) based on the sea-ice biomarker IP25, phytoplankton biomarker brassicasterol and terrestrial biomarker long-chain n-alkanols in piston core MD99-2272 from the North Icelandic shelf. During the Bølling/Allerød (14.7-12.9 ka), the North Icelandic shelf was characterized by extensive spring sea-ice cover linked to reduced flow of warm Atlantic Water and dominant Polar water influence, as well as strong meltwater input in the area. This pattern showed an anti-phase relationship with the ice-free/less ice conditions in marginal areas of the eastern Nordic Seas, where the Atlantic Water inflow was strong, and contributed to an enhanced deep-water formation. Prolonged sea-ice cover with occasional occurrence of seasonal sea ice prevailed during the Younger Dryas (12.9-11.7 ka) interrupted by a brief interval of enhanced Irminger Current and deposition of the Vedde Ash, as opposed to abruptly increased sea-ice conditions in the eastern Nordic Seas. The seasonal sea ice decreased gradually from the Younger Dryas to the onset of the Holocene corresponding to increasing insolation. Ice-free conditions and sea surface warming were observed for the Early Holocene, followed by expansion of sea ice during the Mid-Holocene.

Regional Sea Level Changes and Projections over North Pacific Driven by Air-sea interaction and Inter-basin Teleconnections

NASA Astrophysics Data System (ADS)

Li, X.; Zhu, J.; Xie, S. P.

2017-12-01

After the launch of the TOPEX/Poseidon satellite since 1992, a series of regional sea level changes have been observed. The northwestern Pacific is among the most rapid sea-level-rise regions all over the world. The rising peak occurs around 40°N, with the value reaching 15cm in the past two decades. Moreover, when investigating the projection of global sea level changes using CMIP5 rcp simulations, we found that the northwestern Pacific remains one of the most rapid sea-level-rise regions in the 21st century. To investigate the physical dynamics of present and future sea level changes over the Pacific, we performed a series of numerical simulations with a hierarchy of climate models, including earth system model, ocean model, and atmospheric models, with different complexity. Simulation results indicate that this regional sea level change during the past two decades is mainly caused by the shift of the Kuroshio, which is largely driven by the surface wind anomaly associated with an intensified and northward shifted north Pacific sub-tropical high. Further analysis and simulations show that these changes of sub-tropical high can be primarily attributed to the regional SST forcing from the Pacific Decadal Oscillation, and the remote SST forcings from the tropical Atlantic and the Indian Ocean. In the rcp scenario, on the other hand, two processes are crucial. Firstly, the meridional temperature SST gradient drives a northward wind anomaly across the equator, raising the sea level all over the North Pacific. Secondly, the atmospheric circulation changes around the sub-tropical Pacific further increase the sea level of the North Western Pacific. The coastal region around the Northwest Pacific is the most densely populated region around the world, therefore more attention must be paid to the sea level changes over this region, as suggested by our study.

Phytoplankton Bloom in North Sea off Scotland

NASA Technical Reports Server (NTRS)

2008-01-01

The northern and western highlands of Scotland were still winter-brown and even dusted with snow in places, but the waters of the North Sea were blooming with phytoplankton on May 8, 2008, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite passed over the region and captured this image. The tiny, plant-like organisms swirled in the waters off the country's east coast, coloring the shallow coastal waters shades of bright blue and green. Phytoplankton are tiny organisms--many are just a single cell--that use chlorophyll and other pigments to capture light for photosynthesis. Because these pigments absorb sunlight, they change the color of the light reflected from the sea surface back to the satellite. Scientists have used observations of 'ocean color' from satellites for more than 20 years to track worldwide patterns in phytoplankton blooms. Phytoplankton are important to the Earth system for a host of reasons, including their status as the base of the ocean food web. In the North Sea, they are the base of the food web that supports Scotland's commercial fisheries, including monkfish and herring. As photosynthesizers, they also play a crucial role in the carbon cycle, removing carbon dioxide from the atmosphere. Some oceanographers are concerned that rising ocean temperatures will slow phytoplankton growth rates, harming marine ecosystems and causing carbon dioxide to accumulate more rapidly in the atmosphere.

Two centuries of observed atmospheric variability and change over the North Sea region

NASA Astrophysics Data System (ADS)

Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard; Woollings, Tim

2016-04-01

In the upcoming North Sea Region Climate Change Assessment (NOSCCA), we present a synthesis of current knowledge about past, present and possible future climate change in the North Sea region. A climate change assessment from published scientific work has been conducted as a kind of regional IPCC report, and a book has been produced that will be published by Springer in 2016. In the framework of the NOSCCA project, we examine past and present studies of variability and changes in atmospheric variables within the North Sea region over the instrumental period, roughly the past 200 years, based on observations and reanalyses. The variables addressed in this presentation are large-scale circulation, pressure and wind, surface air temperature, precipitation and radiative properties (clouds, solar radiation, and sunshine duration). While air temperature over land, not unexpectedly, has increased everywhere in the North Sea region, with strongest trends in spring and in the north of the region, a precipitation increase has been observed in the north and a decrease in the south of the region. This pattern goes along with a north-eastward shift of storm tracks and is in agreement with climate model projections under enhanced greenhouse gas concentrations. For other variables, it is not obvious which part of the observed changes may be due to anthropogenic activities and which is internally forced. It remains also unclear to what extent atmospheric circulation over the North Sea region is influenced by distant factors, in particular Arctic sea-ice decline in recent decades. There are indications of an increase in the number of deep cyclones (but not in the total number of cyclones), while storminess since the late 19th century shows no robust trends. The persistence of circulation types appears to have increased over the last century, and consequently, there is an indication for 'more extreme' extreme events. However, changes in extreme weather events are difficult to assess

Observing and modelling phytoplankton community structure in the North Sea

NASA Astrophysics Data System (ADS)

Ford, David A.; van der Molen, Johan; Hyder, Kieran; Bacon, John; Barciela, Rosa; Creach, Veronique; McEwan, Robert; Ruardij, Piet; Forster, Rodney

2017-03-01

Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models are therefore not yet frequently validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical-biogeochemical ocean models, the biogeochemical components of which are different variants of the widely used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. An initial comparison of the formulations and parameterizations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed phytoplankton community structure. These findings will help inform future model development, which should be coupled

Molecular phylogenetic and chemical analyses of the microbial mats in deep-sea cold seep sediments at the northeastern Japan Sea.

PubMed

Arakawa, Shizuka; Sato, Takako; Sato, Rumi; Zhang, Jing; Gamo, Toshitaka; Tsunogai, Urumu; Hirota, Akinari; Yoshida, Yasuhiko; Usami, Ron; Inagaki, Fumio; Kato, Chiaki

2006-08-01

Microbial communities inhabiting deep-sea cold seep sediments at the northeastern Japan Sea were characterized by molecular phylogenetic and chemical analyses. White patchy microbial mats were observed along the fault offshore the Hokkaido Island and sediment samples were collected from two stations at the southern foot of the Shiribeshi seamount (M1 site at a depth of 2,961 m on the active fault) and off the Motta Cape site (M2 site at a depth of 3,064 m off the active fault). The phylogenetic and terminal-restriction fragment polymorphism analyses of PCR-amplified 16S rRNA genes revealed that microbial community structures were different between two sampling stations. The members of ANME-2 archaea and diverse bacterial components including sulfate reducers within Deltaproteobacteria were detected from M1 site, indicating the occurrence of biologically mediated anaerobic oxidation of methane, while microbial community at M2 site was predominantly composed of members of Marine Crenarchaeota group I, sulfate reducers of Deltaproteobacteria, and sulfur oxidizers of Epsilonproteobacteria. Chemical analyses of seawater above microbial mats suggested that concentrations of sulfate and methane at M1 site were largely decreased relative to those at M2 site and carbon isotopic composition of methane at M1 site shifted heavier ((13)C-enriched), the results of which are consistent with molecular analyses. These results suggest that the mat microbial communities in deep-sea cold seep sediments at the northeastern Japan Sea are significantly responsible for sulfur and carbon circulations and the geological activity associated with plate movements serves unique microbial habitats in deep-sea environments.

Is Ice-Rafted Sediment in a North Pole Marine Record Evidence for Perennial Sea-ice Cover?

NASA Technical Reports Server (NTRS)

Tremblay, L.B.; Schmidt, G.A.; Pfirman, S.; Newton, R.; DeRepentigny, P.

2015-01-01

Ice-rafted sediments of Eurasian and North American origin are found consistently in the upper part (13 Ma BP to present) of the Arctic Coring Expedition (ACEX) ocean core from the Lomonosov Ridge, near the North Pole (approximately 88 degrees N). Based on modern sea-ice drift trajectories and speeds, this has been taken as evidence of the presence of a perennial sea-ice cover in the Arctic Ocean from the middle Miocene onwards. However, other high latitude land and marine records indicate a long-term trend towards cooling broken by periods of extensive warming suggestive of a seasonally ice-free Arctic between the Miocene and the present. We use a coupled sea-ice slab-ocean model including sediment transport tracers to map the spatial distribution of ice-rafted deposits in the Arctic Ocean. We use 6 hourly wind forcing and surface heat fluxes for two different climates: one with a perennial sea-ice cover similar to that of the present day and one with seasonally ice-free conditions, similar to that simulated in future projections. Model results confirm that in the present-day climate, sea ice takes more than 1 year to transport sediment from all its peripheral seas to the North Pole. However, in a warmer climate, sea-ice speeds are significantly faster (for the same wind forcing) and can deposit sediments of Laptev, East Siberian and perhaps also Beaufort Sea origin at the North Pole. This is primarily because of the fact that sea-ice interactions are much weaker with a thinner ice cover and there is less resistance to drift. We conclude that the presence of ice-rafted sediment of Eurasian and North American origin at the North Pole does not imply a perennial sea-ice cover in the Arctic Ocean, reconciling the ACEX ocean core data with other land and marine records.

Thickness and Lower Limit Seismogenic Layer within the Crust beneath Japanese Islands on the Japan Sea Side

NASA Astrophysics Data System (ADS)

Matsubara, M.; Sato, H.

2015-12-01

1. Introduction I investigate the depth of the seismogenic layer in order to estimate the lower limit of the seismogenic fault plane since this depth is related to the size of the earthquake caused by the active fault. I have indexes D10 and D90 as the upper and lower limits of the seismogenic layer defined as the depth above which 10 % and 90 % of the whole crustal earthquakes occurred from the surface, respectively. The difference between the D10 and D90 is the thickness of the seismogenic layer. 2. Data and method The NIED Hi-net has a catalog of hypocenters determined with one-dimensional　velocity (1D) structure (Ukawa et al., 1984) and I estimated the D10 and D90 with this catalog at first. I construct the system to relocate the hypocenters from 2001 to 2013 with magnitude greater than 1.5 on the Japan Sea side shallower than 50 km depth with the three-dimensional velocity (3D) structure (Matsubara and Obara, 2011) obtained by seismic tomography. I estimate the D10 and D90 from the hypocenter catalog with 3D structure. 3. Result Many earthquakes shallower than 5 km with 1D structure are relocated to deeper with 3D structure and the earthquakes deeper than 15 km are relocated to about 5 km shallower. With 3D structure D10 deepens and D90 shallows from 1D structure. D90 beneath the northern Honshu is deeper than the other area and D90 beneath the Japan Sea is much deeper than the inland area. The thickness of the seismogenic layer beneath the Japan Sea is also thick from 8-16 km. D90 on the Japan Sea side of the southwestern Japan on the west side of the Itoigawa Shizuoka Tectonic Line is very shallow as 11-16 km and the thickness of the seismogenic layer is also thin as 2-7 km. 4. Discussion Omuralieva et al. (2012) relocated the JMA unified hypocenters with 3D structure and estimated shallower D90 than that from the JMA catalog. Very deep D90 beneath the northern Hokkaido and northern Honshu is consistent with our result. 5. Conclusion Using 3D velocity

Phytoplankton of the North Sea and its dynamics: A review

NASA Astrophysics Data System (ADS)

Reid, P. C.; Lancelot, C.; Gieskes, W. W. C.; Hagmeier, E.; Weichart, G.

Phytoplankton is the major contributor to algal biomass and primary production of the North Sea, although crops of macroalgae can locally be up to 2000 g C.m -2 along the coast of the U.K. and Norway, and microphytobenthos dominates production in the shallow tidal flat areas bordering the coasts of England, the Netherlands, Germany and Denmark. Data collected since 1932 during the Continuous Plankton Recorder Survey show consistent patterns of geographical, seasonal and annual variation in the distribution of phytoplankton and its major taxonomic components. There is a trend of increased colouration in Recorder silks in the southern North Sea until approximately 1975 since when Colour levels (assumed to be indicative of algal biomass) have declined. In the eutrophic Dutch Wadden Sea the algal crop continued to increase; in Dutch coastal North Sea waters a trend of biomass increase reversed since 1984, apparently due to a reduction in Rhine river outflow. Long-term observations made at Helgoland since the 60's also show trends of increasing nutrients and phytoplankton biomass only to 1984. Adverse effects such as deoxygenation, foam formation and toxin production have been linked to mass concentrations of algae known as blooms. There is no evidence from existing reports for an increase in their frequency, although some years stand out with larger numbers. Occurrence of blooms can partly be explained by hydrographic conditions. More than 30 taxa are recognised as occurring in bloom proportions in the North Sea, approximately one third of which can be toxic. The crop of Bacillariophyceae (diatoms) is not likely to increase with eutrophication due to silicate limitation. An extensive subsurface maximum of armoured dinoflagellates, its abundance gouverned by hydrographic conditions, is the most characteristic feature of the central and northern North Sea in the summer months. Abundance, sometimes dominance, of picoplankton and of species that are not readily detected by

North Sea Scyphomedusae; summer distribution, estimated biomass and significance particularly for 0-group Gadoid fish

NASA Astrophysics Data System (ADS)

Hay, S. J.; Hislop, J. R. G.; Shanks, A. M.

Data on the by-catch of Scyphomedusae from pelagic trawls was collected during the routine ICES International 0-group Gadoid Surveys of the North Sea, in June and July of the years 1971-1986 (except 1984). These data are used to describe the distributions, abundances and biomasses of three common North Sea Scyphomedusae: Aurelia aurita (L.), Cyanea capillata (L.) and C. lamarckii (Péron & Lesuer). Information is also presented on inter-annual variability, size (umbrella diameter) frequencies and, for the Cyanea species, umbrella diameter: wet weight relationships. The general role and ecological significance of Scyphomedusae is discussed and, given the well known 'shelter' relationships between Scyphomedusae and certain 0-group fish, whiting ( Merlangius merlangus) and haddock ( Melanogrammus aeglefinus), in particular. The data were examined for evidence of such relationships. Aurelia aurita, although fairly widespread in the northern North Sea was virtually absent from the central North Sea but very abundant in coastal waters. This species was particularly abundant off the Scottish east coast and especially in the Moray Firth. Cyanea lamerckii was most abundant in the southern and eastern North Sea. More widespread than Aurelia, this species was also most abundant in coastal regions, particularly off the Danish west coast. Cyanea capillata, with a more northern distribution was also more widely distributed and abundant offshore. This species was most abundant in the area between the Orkney/Shetland Isles and the Norwegian Deep and in shelf waters of the north west approaches to the North Sea. As with C. lamarckii it was also, in some years, abundant off the Scottish east coast and west of Denmark. The abundance and the size frequency of the jellyfish show considerable inter-annual variability, and variability between regions of the North Sea. It is considered that hydrographic variability and differences in food supply to both medusae and to their sessile

Reserve growth in oil fields of the North Sea

USGS Publications Warehouse

Klett, T.R.; Gautier, D.L.

2005-01-01

The assessment of petroleum resources of the North Sea, as well as other areas of the world, requires a viable means to forecast the amount of growth of reserve estimates (reserve growth) for discovered fields and to predict the potential fully developed sizes of undiscovered fields. This study investigates the utility of North Sea oil field data to construct reserve-growth models. Oil fields of the North Sea provide an excellent dataset in which to examine the mechanisms, characteristics, rates and quantities of reserve growth because of the high level of capital investments, implementation of sophisticated technologies and careful data collection. Additionally, these field data are well reported and available publicly. Increases in successive annual estimat es of recoverable crude oil volumes indicate that oil fields in the North Sea, collectively and in each country, experience reserve growth. Specific patterns of reserve growth are observed among countries and primary producing reservoir-rock types. Since 1985, Norwegian oil fields had the greatest volume increase; Danish oil fields increased by the greatest percentage relative to 1985 estimates; and British oil fields experienced an increase in recoverable oil estimates for the first ten years since 1985, followed by a slight reduction. Fields producing primarily from clastic reservoirs account for the majority of the estimated recoverable oil and, therefore, these fields had the largest volumetric increase. Fields producing primarily from chalk (limestone) reservoirs increased by a greater percentage relative to 1985 estimates than did fields producing primarily from clastic reservoirs. Additionally, the largest oil fields had the greatest volumetric increases. Although different reserve-growth patterns are observed among oil fields located in different countries, the small number of fields in Denmark precludes construction of reserve-growth models for that country. However, differences in reserve

Sea-Level Acceleration Hotspot along the Atlantic Coast of North America

NASA Astrophysics Data System (ADS)

Sallenger, A. H.; Doran, K. J.; Howd, P.

2012-12-01

Spatial variations of sea level rise (SLR) can be forced by dynamic processes arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes arising from mass re-distributions changing gravity and the earth's rotation and shape. The sea-level variations can form unique spatial patterns, yet there are very few field observations verifying predicted patterns, or fingerprints. We present evidence of SLR acceleration in a 1,000-km-long hotspot on the North American Atlantic coast north of Cape Hatteras, North Carolina to above Boston, Massachusetts. By using accelerations, or rate differences, sea level signals that are linear over sub-century records, like the relative sea level changes arising from vertical land movements of glacial isostatic adjustment, do not affect our results. For a 60-yr regression window (between 1950-1979 and 1980-2009), mean increase in the rate of SLR in the hotspot was 1.97 ± 0.64 mm/yr. (For a 40-yr window, the mean rate increase was 3.80 ± 1.06 mm/yr.) South of Cape Hatteras to Key West, Florida, rate differences for either 60 yr or 40 yr windows were not statistically different from zero (e.g. for 60 yr window: mean= 0.11 ± 0.92 mm/yr). This pattern is similar to a fingerprint of dynamic SLR established by sea-level projections in several climate model studies. Correlations were consistent with accelerated SLR associated with a slowdown of Atlantic Meridional Overturning Current.

Backarc spreading and mantle wedge flow beneath the Japan Sea: insight from Rayleigh-wave anisotropic tomography

NASA Astrophysics Data System (ADS)

Liu, Xin; Zhao, Dapeng

2016-10-01

We present the first high-resolution Rayleigh-wave phase-velocity azimuthal anisotropy tomography of the Japan subduction zone at periods of 20-150 s, which is determined using a large number of high-quality amplitude and phase data of teleseismic fundamental-mode Rayleigh waves. The obtained 2-D anisotropic phase-velocity models are then inverted for a 3-D shear-wave velocity azimuthal anisotropy tomography down to a depth of ˜300 km beneath Japan. The subducting Pacific slab is imaged as a dipping high-velocity zone with trench-parallel fast-velocity directions (FVDs) which may indicate the anisotropy arising from the normal faults produced at the outer-rise area near the Japan trench axis, overprinting the slab fossil fabric, whereas the mantle wedge generally exhibits lower velocities with trench-normal FVDs which reflect subduction-driven corner flow and anisotropy. Depth variations of azimuthal anisotropy are revealed in the big mantle wedge beneath the Japan Sea, which may reflect past deformations in the Eurasian lithosphere related to backarc spreading during 21 to 15 Ma and complex current convection in the asthenosphere induced by active subductions of both the Pacific and Philippine Sea plates.

Inter-annual variability of North Sea plaice spawning habitat

NASA Astrophysics Data System (ADS)

Loots, C.; Vaz, S.; Koubbi, P.; Planque, B.; Coppin, F.; Verin, Y.

2010-11-01

Potential spawning habitat is defined as the area where environmental conditions are suitable for spawning to occur. Spawning adult data from the first quarter (January-March) of the International Bottom Trawl Survey have been used to study the inter-annual variability of the potential spawning habitat of North Sea plaice from 1980 to 2007. Generalised additive models (GAM) were used to create a model that related five environmental variables (depth, bottom temperature and salinity, seabed stress and sediment type) to presence-absence and abundance of spawning adults. Then, the habitat model was applied each year from 1970 to 2007 to predict inter-annual variability of the potential spawning habitat. Predicted responses obtained by GAM for each year were mapped using kriging. A hierarchical classification associated with a correspondence analysis was performed to cluster spawning suitable areas and to determine how they evolved across years. The potential spawning habitat was consistent with historical spawning ground locations described in the literature from eggs surveys. It was also found that the potential spawning habitat varied across years. Suitable areas were located in the southern part of the North Sea and along the eastern coast of England and Scotland in the eighties; they expanded further north from the nineties. Annual survey distributions did not show such northward expansion and remained located in the southern North Sea. This suggests that this species' actual spatial distribution remains stable against changing environmental conditions, and that the potential spawning habitat is not fully occupied. Changes in environmental conditions appear to remain within plaice environmental ranges, meaning that other factors may control the spatial distribution of plaice spawning habitat.

Mechanisms controlling the intra-annual mesoscale variability of SST and SPM in the southern North Sea

NASA Astrophysics Data System (ADS)

Pietrzak, Julie D.; de Boer, Gerben J.; Eleveld, Marieke A.

2011-04-01

Thermal and optical remote sensing data were used to investigate the spatial and temporal distribution of sea surface temperature (SST) and of suspended particulate matter (SPM) in the southern North Sea. Monthly SST composites showed pronounced seasonal warming of the southern North Sea and delineated the English coastal and continental coastal waters. The East-Anglia Plume is the dominant feature of the English coastal waters in the winter and autumn SPM composites, and the Rhine region of freshwater influence (ROFI), including the Flemish Banks, is the dominant feature of the continental waters. These mesoscale spatial structures are also influenced by the evolution of fronts, such as the seasonal front separating well-mixed water in the southern Bight, from the seasonally stratified central North Sea waters. A harmonic analysis of the SST and SPM images showed pronounced seasonal variability, as well as spring-neap variations in the level of tidal mixing in the East Anglia Plume, the Rhine ROFI and central North Sea. The harmonic analysis indicates the important role played by the local meteorology and tides in governing the SST and near-surface SPM concentrations in the southern North Sea. In the summer, thermal stratification affects the visibility of SPM to satellite sensors in the waters to the north of the Flamborough and Frisian Fronts. Haline stratification plays an important role in the visibility of SPM in the Rhine ROFI throughout the year. When stratified, both regions typically exhibit low surface SPM values. A numerical model study, together with the harmonic analysis, highlights the importance of tides and waves in controlling the stratification in the southern North Sea and hence the visibility of SPM.

Sea Urchin Embryogenesis as Bioindicators of Marine Pollution in Impact Areas of the Sea of Japan/East Sea and the Sea of Okhotsk.

PubMed

Lukyanova, Olga N; Zhuravel, Elena V; Chulchekov, Denis N; Mazur, Andrey A

2017-08-01

The embryogenesis of the sea urchin sand dollar Scaphechinus mirabilis was used as bioindicators of seawater quality from the impact areas of the Sea of Japan/East Sea (Peter the Great Bay) and the Sea of Okhotsk (northwestern shelf of Sakhalin Island and western shelf of Kamchatka Peninsula). Fertilization membrane formation, first cleavage, blastula formation, gastrulation, and 2-armed and 4-armed pluteus formation have been analyzed and a number of abnormalities were calculated. Number of embryogenesis anomalies in sand dollar larvae exposed to sea water from different stations in Peter the Great Bay corresponds to pollution level at each area. The Sea of Okhotsk is the main fishing area for Russia. Anthropogenic impact on the marine ecosystem is caused by fishing and transport vessels mainly. But two shelf areas are considered as "hot spots" due to oil and gas drilling. Offshore oil exploitation on the northeastern Sakhalin Island has been started and at present time oil is being drill on oil-extracting platforms continuously. Significant reserves of hydrocarbons are prospected on western Kamchatka shelf, and exploitation drilling in this area was intensified in 2014. A higher number of abnormalities at gastrula and pluteus stages (19-36%) were detected for the stations around oil platforms near Sakhalin Island. On the western Kamchatka shelf number of abnormalities was 7-21%. Such anomalies as exogastrula, incomplete development of pairs of arms were not observed at all; only the delay of development was registered. Eggs, embryos, and larvae of sea urchins are the suitable bioindicators of early disturbances caused by marine pollution in impact ecosystems.

Enhanced waterflooding design with dilute surfactant concentrations for North Sea conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michels, A.M.; Djojosoeparto, R.S.; Haas, H.

1996-08-01

Efficient selection procedures for surfactants have been applied to design a low-concentration surfactant-flooding process for North Sea oilfield application. Anionic surfactants of the propoxy ethoxy glyceryl sulfonate type can be used at 0.1 wt% concentrations together with sacrificial agents and without a polymer drive. Currently estimated unit technical costs (UTC`s)--at 8%--for application in the North Sea oil fields range frommore » $81 to $$94/incremental m{sup 3}, without taking uncertainty factors into account. Including such factors would likely add another $$31/m{sup 3} to the costs.« less

The role of atmospheric internal variability on the prediction skill of interannual North Pacific sea-surface temperatures

NASA Astrophysics Data System (ADS)

Narapusetty, Balachandrudu

2017-06-01

The sensitivity of the sea-surface temperature (SST) prediction skill to the atmospheric internal variability (weather noise) in the North Pacific (20∘-60∘N;120∘E-80∘W) on decadal timescales is examined using state-of-the-art Climate Forecasting System model version 2 (CFS) and a variation of CFS in an Interactive Ensemble approach (CFSIE), wherein six copies of atmospheric components with different perturbed initial states of CFS are coupled with the same ocean model by exchanging heat, momentum and fresh water fluxes dynamically at the air-sea interface throughout the model integrations. The CFSIE experiments are designed to reduce weather noise and using a few ten-year long forecasts this study shows that reduction in weather noise leads to lower SST forecast skill. To understand the pathways that cause the reduced SST prediction skill, two twenty-year long forecasts produced with CFS and CFSIE for 1980-2000 are analyzed for the ocean subsurface characteristics that influence SST due to the reduction in weather noise in the North Pacific. The heat budget analysis in the oceanic mixed layer across the North Pacific reveals that weather noise significantly impacts the heat transport in the oceanic mixed layer. In the CFSIE forecasts, the reduced weather noise leads to increased variations in heat content due to shallower mixed layer, diminished heat storage and enhanced horizontal heat advection. The enhancement of the heat advection spans from the active Kuroshio regions of the east coast of Japan to the west coast of continental United States and significantly diffuses the basin-wide SST anomaly (SSTA) contrasts and leads to reduction in the SST prediction skill in decadal forecasts.

Deep-water Hydrozoa (Cnidaria: Medusozoa) in the Sea of Japan, collected during the 51st Cruise of R/V Akademik M.A. Lavrentyev, with description Opercularella angelikae, sp. nov.

NASA Astrophysics Data System (ADS)

Stepanjants, Sofia D.

2013-02-01

A report is given about Hydrozoa collected at depths between 455 and 3666 m in the Sea of Japan during the Russian-German expedition on R/V Akademik M.A. Lavrentyev. Ten species were found, with four of them being typical bathyal-abyssal and abyssal zones. A new species, Opercularella angelikae, is described, and it was the dominant hydroid in samples from 970 to 3660 m. Four eurybathic species characteristics of the Sea of Japan were sampled between 455 and 582 m. Abyssal (pseudoabyssal after Andriashev, 1979) hydroid fauna in the Sea of Japan is reported. The hypothesis that an exclusively deep-water fauna is lacking in abyssal regions of the Sea of Japan is disputed. The author's personal opinion considered concerning the borders of 1000 m between shallow and deep hydrozoan species in the Sea of Japan.

The Holocene palaeogeography and relative sea level for two tidal basins of the German North Sea coast

NASA Astrophysics Data System (ADS)

Bungenstock, Friederike; Wartenberg, Wolfram; Mauz, Barbara; Freund, Holger; Frechen, Manfred; Weerts, Henk J. T.; Berner, Heinrich

2014-05-01

The response of coasts to global sea-level rise is highly variable. Knowledge of driving coastal parameters alongside the regional sea-level history is therefore indispensable when the response to global sea-level rise is to be assessed. Here, we study the Holocene relative sea-level of the south coast of the North Sea which is controlled by a number of very local parameters, as well as by regional glacio-isostatic adjustments. It is therefore crucial to restrict the data acquisition and evaluation to small coastal sections, ideally to single tidal basins, to minimize the sources of uncertainties (Bungenstock & Weerts 2010, 2012). We present data from two tidal basins, Langeoog and Jade Bay. For Langeoog a database derived from 600 cores, 68 km of Boomer seismic data, 33 radiocarbon ages and 8 OSL dates is available. (Bungenstock & Schäfer 2009, Mauz & Bungenstock 2007). For the Jade bay, the database comprises sedimentary markers, pollen and macro remains derived from 68 cores. The sedentary chronology is based on 54 radiocarbon ages and pollen constraints (Wartenberg & Freund 2011, Wartenberg et al. 2013). For both tidal basins the sedimentological record was interpreted in terms of the local paleogeographical development since about 7000 cal BP and its influence on the local relative sea-level curve. While the trend of the relative sea level is similar for both tidal basins, it shows a different altitude. The timing of the main marine transgression within the Langeoog area takes place ~3000 cal. BP whereas the sedimentological record of the Jade Bay shows two prominent transgressions, one for ~5000 cal. BP and one for ~3000 cal. BP. The Langeoog palaeo-environment is continuously characterised by marine influence. Within the Jade Bay two different palaeo-environments could be identified, documenting that from the West to the centre the landscape development in the Jade Bay was drainage driven feeding the associated fen peat with minerogenic water but being

Boreal Tintinnid Assemblage in the Northwest Pacific and Its Connection with the Japan Sea in Summer 2014.

PubMed

Li, Haibo; Xu, Zhiqiang; Zhang, Wuchang; Wang, Shaoqing; Zhang, Guangtao; Xiao, Tian

2016-01-01

Tintinnids are planktonic ciliates that play an important role in marine ecosystem. According to their distribution in the world oceans, tintinnid genera were divided into several biogeographical types such as boreal, warm water, austral and neritic. Therefore, the oceanic tintinnid assemblage could be correspondingly divided into boreal assemblage, warm water assemblage and austral assemblage. The purpose of this study was to investigate the characteristics of boreal tintinnid assemblage in the Northwest Pacific and the Arctic, and to identify the connection between boreal tintinnid assemblage and neighboring assemblages. Surface water samples were collected along a transect from the East China Sea to the Chukchi Sea in summer 2014. According to the presence of boreal genera and warm water genera, three tintinnid assemblages (the East China Sea neritic assemblage, the Japan Sea warm water assemblage, and the boreal assemblage) were identified along the transect. The boreal assemblage extended from the Chukchi Sea to the waters north of the Sōya Strait. Densities peaks occurred at stations in the two branches of the Alaska Current and decreased both northward and southward. The densities were <10 ind./dm3 at most stations in Arctic region. The dominant genera (Acanthostomella, Codonellopsis, Parafavella, and Ptychocylis) accounted for 79.07±29.67% (n = 49) of the abundance in the boreal assemblage. The densities of the dominant genera covaried with strongly significant positive correlations. Tintinnids with lorica oral diameter of 22-26 μm and 38-42 μm were dominant and contributed 67.35% and 15.13%, respectively, to the total abundance in the boreal assemblage. The distribution and densities of tintinnids in the study area suggest that the Sōya Strait might be a geographical barrier for tintinnids expansion.

Biogeochemical properties of sinking particles in the southwestern part of the East Sea (Japan Sea)

NASA Astrophysics Data System (ADS)

Kim, Minkyoung; Hwang, Jeomshik; Rho, TaeKeun; Lee, Tongsup; Kang, Dong-Jin; Chang, Kyung-Il; Noh, Suyun; Joo, HuiTae; Kwak, Jung Hyun; Kang, Chang-Keun; Kim, Kyung-Ryul

2017-03-01

This study investigates the biological pump system in the East Sea (Japan Sea) by conducting an analysis of the total particle flux, biogenic material composition, and carbon isotope ratios of sinking particles. The samples were collected for one year starting from March 2011 using time-series sediment traps deployed at depths of 1040 m and 2280 m on bottom-tethered mooring at Station EC1 (37.33°N, 131.45°E; 2300 m water depth) in the Ulleung Basin (UB), southwestern part of the East Sea. The temporal variation in the particulate organic carbon (POC) flux at 1000 m shows a good relationship with the primary production in the corresponding surface water. The ratio of POC flux at 1000 m to satellite-based primary production in the corresponding region in the UB was 3%, which is comparable to the values of 2 to 5% estimated from previous studies of other part of the East Sea. The lithogenic material accounted for > 17% of the sinking particles at 1000 m and for a larger fraction of 40 to 60% at 2280 m. The radiocarbon contents of the sinking POC at both trap depths imply the additional supply of aged POC, with a much greater contribution at 2280 m. Overall, the particle flux in the deep interior of the East Sea appears to be controlled by the supply of complex sources, including aeolian input, the lateral supply of resuspended sediments, and biological production in the surface water.

Effects of air-sea coupling over the North Sea and the Baltic Sea on simulated summer precipitation over Central Europe

NASA Astrophysics Data System (ADS)

Ho-Hagemann, Ha Thi Minh; Gröger, Matthias; Rockel, Burkhardt; Zahn, Matthias; Geyer, Beate; Meier, H. E. Markus

2017-12-01

This study introduces a new approach to investigate the potential effects of air-sea coupling on simulated precipitation inland over Central Europe. We present an inter-comparison of two regional climate models (RCMs), namely, the COSMO-CLM (hereafter CCLM) and RCA4 models, which are configured for the EURO-CORDEX domain in the coupled and atmosphere-only modes. Two versions of the CCLM model, namely, 4.8 and 5.0, join the inter-comparison being almost two different models while providing pronouncedly different summer precipitation simulations because of many changes in the dynamics and physics of CCLM in version 5.0. The coupling effect on the prominent summer dry bias over Central Europe is analysed using seasonal (JJA) mean statistics for the 30-year period from 1979 to 2009, with a focus on extreme precipitation under specific weather regimes. The weather regimes are compared between the coupled and uncoupled simulations to better understand the mechanism of the coupling effects. The comparisons of the coupled systems with the atmosphere-only models show that coupling clearly reduces the dry bias over Central Europe for CCLM 4.8, which has a large dry summer bias, but not for CCLM 5.0 and RCA4, which have smaller dry biases. This result implies that if the atmosphere-only model already yields reasonable summer precipitation over Central Europe, not much room for improvement exists that can be caused by the air-sea coupling over the North Sea and the Baltic Sea. However, if the atmosphere-only model shows a pronounced summer dry bias because of a lack of moisture transport from the seas into the region, the considered coupling may create an improved simulation of summer precipitation over Central Europe, such as for CCLM 4.8. For the latter, the benefit of coupling varies over the considered timescales. The precipitation simulations that are generated by the coupled system COSTRICE 4.8 and the atmosphere-only CCLM 4.8 are mostly identical for the summer mean

Variability in the correlation between Asian dust storms and chlorophyll a concentration from the North to Equatorial Pacific.

PubMed

Tan, Sai-Chun; Yao, Xiaohong; Gao, Hui-Wang; Shi, Guang-Yu; Yue, Xu

2013-01-01

A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997-2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the <50 m China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54-0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For the >50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32-0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36). These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas.

Buried paleo-sedimentary basins in the north-eastern Black Sea-Azov Sea area and tectonic implications (DOBRE-2)

NASA Astrophysics Data System (ADS)

Starostenko, Vitaly; Stephenson, Randell; Janik, Tomasz; Tolkunov, Anatoly

2014-05-01

A number of independent but inter-related projects carried out under the auspices of various national and international programmes in Ukraine including DARIUS were aimed at imaging the upper lithosphere, crustal and sedimentary basin architecture in the north-eastern Black Sea, southern Crimea and Kerch peninsulas and the Azov Sea. This region marks the transition from relatively undisturbed Precambrian European cratonic crust and lithosphere north of the Azov Sea to areas of significant Phanerozoic tectonics and basin development, in both extensional as well as compressional environments, to the south, including the eastern Black Sea rift, which is the main sedimentary basin of the study area. The wide-angle reflection and refraction (WARR) profile DOBRE-2, a Ukrainian national project with international participation (see below), overlapping some 115 km of the southern end of the DOBREfraction'99 profile (that crosses the intracratonic Donbas Foldbelt) in the north and running to the eastern Black Sea basin in the south, utilised on- and offshore recording and energy sources. It maps crustal velocity structure across the craton margin and documents, among other things, that the Moho deepens from 40 km to ~47 km to the southwest below the Azov Sea and Crimean-Caucasus deformed zone. A regional CDP seismic profile coincident with DOBRE-2, crossing the Azov Sea, Kerch Peninsula and the north-eastern Black Sea southwest to the Ukraine-Turkey border, acquired by Ukrgeofisika (the Ukrainian national geophysical company) reveals in its inferred structural relationships the ages of Cretaceous and younger extensional and subsequent basin inversion tectonic events as well as the 2D geometry of basement displacement associated with post mid-Eocene inversion. A direct comparison of the results of the WARR velocity model and the near-vertical reflection structural image has been made by converting the former into the time domain. The results dramatically demonstrate that

Distribution and sources of dissolved black carbon in surface waters of the Chukchi Sea, Bering Sea, and the North Pacific Ocean

NASA Astrophysics Data System (ADS)

Nakane, Motohiro; Ajioka, Taku; Yamashita, Youhei

2017-05-01

Pyrogenic carbon, also called black carbon (BC), is an important component in the global carbon cycle. BC produced by biomass burning or fossil fuel combustion is transported to oceans by the atmosphere or rivers. However, environmental dynamics (i.e., major sources and sinks) of BC in marine environments have not been well documented. In this study, dissolved BC (DBC) collected from surface waters of the Chukchi Sea, the Bering Sea, and the subarctic and subtropical North Pacific were analyzed using the benzene polycarboxylic acid (BPCA) method. The DBC concentration and the ratio of B5CA and B6CA to all BPCAs (an index of the DBC condensation degree) ranged from 4.8 to 15.5 µg-C L-1 and from 0.20 to 0.43, respectively, in surface waters of the Chukchi/Bering Seas and the North Pacific Ocean. The concentration and condensation degree of DBC in the Chukchi/Bering Seas were higher and more variable than those in the subarctic and subtropical North Pacific, which implies that the major factors controlling DBC distribution were different in these marine provinces. In the Chukchi/Bering Seas, the DBC concentration was negatively correlated to salinity but positively correlated to chromophoric dissolved organic matter (CDOM) quantity and total dissolved lignin phenol concentration estimated by CDOM parameters. These correlations indicated that the possible major source of DBC in the Chukchi/Bering Seas was Arctic rivers. However, in the North Pacific, where riverine inputs are negligible for most sampling sites, DBC was possibly derived from the atmosphere. Although spectral slopes of CDOM at 275-295 nm (an index of the photodegradation degree of CDOM) differed widely between the subarctic and subtropical North Pacific, the concentration and condensation degrees of DBC were similar between the subarctic and subtropical North Pacific, which suggests that photodegradation was not the only major factor controlling DBC distribution. Therefore, DBC distributions of the

Response of the Baltic and North Seas to river runoff from the Baltic watershed - Physical and biological changes

NASA Astrophysics Data System (ADS)

Hänninen, Jari; Vuorinen, Ilppo; Rajasilta, Marjut; Reid, Philip C.

2015-11-01

Selected Baltic Sea watershed River Runoff (BSRR) events during 1970-2000 were used as predictor in Generalised Linear Mixed Models (GLIMMIX) for evidence of simultaneous changes/chain of events (including possible time lags) in some chemical, physical and biological variables in the Baltic and North Sea ecosystems. Our aim was to explore for climatic-based explanation for ecological regime shifts that were documented semi-simultaneously in both ecosystems. Certain similarities were identified in the North Sea and the Baltic Sea salinity, oxygen concentration, temperature and phyto- and zooplankton parameters. These findings suggest that BSRR events which originate in the Baltic Sea catchment area modify and contribute to large scale ecosystem changes not only in the Baltic Sea, but also in the adjacent parts of the North Sea. However, the Baltic Sea inter-annual and inter-decadal variabilities of physical and biological parameters are driven by direct atmospheric forcing, typically with a relatively short lag. In contrast, such changes in the North Sea are influenced by both local and direct atmospheric forcing, typically with a longer lag than in the Baltic, and a more regional, indirect forcing from changes in the North Atlantic. We suggest that this interactive system partially is behind large scale ecosystem regime shifts found in both Seas. During our study period two such shifts have been identified independently from us in a study earlier in the Southern and Central Baltic in 1980s and 1990s and a later one in 2001/2002 in the North Sea. As a post hoc test we compared the 0+ year class strength of the North Sea herring with BSRR intensity, and found evidence for higher herring production in high BSRR periods, which further corroborates the idea of a remote effect from the large watershed area of the Baltic. Regime shifts as well as their semi-synchronous appearance in two neighbouring sea areas could be identified. GLIMMIX models provide opportunities for

Warming in the Nordic Seas, North Atlantic storms and thinning Arctic sea ice

NASA Astrophysics Data System (ADS)

Alexeev, Vladimir A.; Walsh, John E.; Ivanov, Vladimir V.; Semenov, Vladimir A.; Smirnov, Alexander V.

2017-08-01

Arctic sea ice over the last few decades has experienced a significant decline in coverage both in summer and winter. The currently warming Atlantic Water layer has a pronounced impact on sea ice in the Nordic Seas (including the Barents Sea). More open water combined with the prevailing atmospheric pattern of airflow from the southeast, and persistent North Atlantic storms such as the recent extremely strong Storm Frank in December 2015, lead to increased energy transport to the high Arctic. Each of these storms brings sizeable anomalies of heat to the high Arctic, resulting in significant warming and slowing down of sea ice growth or even melting. Our analysis indicates that the recently observed sea ice decline in the Nordic Seas during the cold season around Svalbard, Franz Joseph Land and Novaya Zemlya, and the associated heat release from open water into the atmosphere, contributed significantly to the increase in the downward longwave radiation throughout the entire Arctic. Added to other changes in the surface energy budget, this increase since the 1960s to the present is estimated to be at least 10 W m-2, which can result in thinner (up to at least 15-20 cm) Arctic ice at the end of the winter. This change in the surface budget is an important contributing factor accelerating the thinning of Arctic sea ice.

Bering Sea Nd isotope records of North Pacific Intermediate Water circulation

NASA Astrophysics Data System (ADS)

Rabbat, C.; Knudson, K. P.; Goldstein, S. L.

2017-12-01

North Pacific Intermediate Water (NPIW) is the primary water mass associated with Pacific meridional overturning circulation. While the relationship between Atlantic meridional overturning circulation and climate has been extensively studied, a lack of suitable sediment cores has limited past investigations of North Pacific climate and NPIW variability. Integrated Ocean Drilling Program Site U1342 (818 m water depth) on Bower's Ridge in the Bering Sea is located at a sensitive depth for detecting changes in NPIW, and it is the only available sub-arctic North Pacific site that offers long, continuous core recovery, relatively high sedimentation rates, excellent foraminifera preservation, and a well-constrained age model over multiple glacial-interglacial cycles. Previous work at Site U1342 from Knudson and Ravelo (2015), using non-quantitative circulation proxies, provides evidence for enhanced NPIW formation during extreme glacials associated with the closure of the Bering Strait and suggest that NPIW was formed locally within the Bering Sea. Our work builds on the potential importance of these results and applies more robust and potentially quantitative circulation proxies to constrain NPIW variability. Here, we present new records of NPIW circulation from Site U1342 based on Nd isotope analyses on fish debris and Fe-Mn encrusted foraminifera, which serve as semi-quantitative "water mass tracers." Weak Bering Sea NPIW formation and ventilation are reflected by relatively lower eNd values indicative of open subarctic North Pacific waters, which are presently predominant, whereas enhanced Bering Sea NPIW formation and ventilation are be reflected by relatively higher eNd values due to the input of Nd from regional volcanic rocks.

Distribution and trajectories of floating and benthic marine macrolitter in the south-eastern North Sea.

PubMed

Gutow, Lars; Ricker, Marcel; Holstein, Jan M; Dannheim, Jennifer; Stanev, Emil V; Wolff, Jörg-Olaf

2018-06-01

In coastal waters the identification of sources, trajectories and deposition sites of marine litter is often hampered by the complex oceanography of shallow shelf seas. We conducted a multi-annual survey on litter at the sea surface and on the seafloor in the south-eastern North Sea. Bottom trawling was identified as a major source of marine litter. Oceanographic modelling revealed that the distribution of floating litter in the North Sea is largely determined by the site of origin of floating objects whereas the trajectories are strongly influenced by wind drag. Methods adopted from species distribution modelling indicated that resuspension of benthic litter and near-bottom transport processes strongly influence the distribution of litter on the seafloor. Major sink regions for floating marine litter were identified at the west coast of Denmark and in the Skagerrak. Our results may support the development of strategies to reduce the pollution of the North Sea. Copyright © 2018 Elsevier Ltd. All rights reserved.

A database of paleoceanographic sediment cores from the North Pacific, 1951-2016

NASA Astrophysics Data System (ADS)

Borreggine, Marisa; Myhre, Sarah E.; Mislan, K. Allison S.; Deutsch, Curtis; Davis, Catherine V.

2017-09-01

We assessed sediment coring, data acquisition, and publications from the North Pacific (north of 30° N) from 1951 to 2016. There are 2134 sediment cores collected by American, French, Japanese, Russian, and international research vessels across the North Pacific (including the Pacific subarctic gyre, Alaskan gyre, Japan margin, and California margin; 1391 cores), the Sea of Okhotsk (271 cores), the Bering Sea (123 cores), and the Sea of Japan (349 cores) reported here. All existing metadata associated with these sediment cores are documented here, including coring date, location, core number, cruise number, water depth, vessel metadata, and coring technology. North Pacific sediment core age models are built with isotope stratigraphy, radiocarbon dating, magnetostratigraphy, biostratigraphy, tephrochronology, % opal, color, and lithological proxies. Here, we evaluate the iterative generation of each published age model and provide comprehensive documentation of the dating techniques used, along with sedimentation rates and age ranges. We categorized cores according to the availability of a variety of proxy evidence, including biological (e.g., benthic and planktonic foraminifera assemblages), geochemical (e.g., major trace element concentrations), isotopic (e.g., bulk sediment nitrogen, oxygen, and carbon isotopes), and stratigraphic (e.g., preserved laminations) proxies. This database is a unique resource to the paleoceanographic and paleoclimate communities and provides cohesive accessibility to sedimentary sequences, age model development, and proxies. The data set is publicly available through PANGAEA at https://doi.org/10.1594/PANGAEA.875998.

Large-scale forcing of the European Slope Current and associated inflows to the North Sea

NASA Astrophysics Data System (ADS)

Marsh, Robert; Haigh, Ivan D.; Cunningham, Stuart A.; Inall, Mark E.; Porter, Marie; Moat, Ben I.

2017-04-01

The European Slope Current provides a shelf-edge conduit for Atlantic Water, a substantial fraction of which is destined for the northern North Sea, with implications for regional hydrography and ecosystems. Drifters drogued at 50 m in the European Slope Current at the Hebridean shelf break follow a wide range of pathways, indicating highly variable Atlantic inflow to the North Sea. Slope Current pathways, timescales and transports over 1988-2007 are further quantified in an eddy-resolving ocean model hindcast. Particle trajectories calculated with model currents indicate that Slope Current water is largely recruited from the eastern subpolar North Atlantic. Observations of absolute dynamic topography and climatological density support theoretical expectations that Slope Current transport is to first order associated with meridional density gradients in the eastern subpolar gyre, which support a geostrophic inflow towards the slope. In the model hindcast, Slope Current transport variability is dominated by abrupt 25-50 % reductions of these density gradients over 1996-1998. Concurrent changes in wind forcing, expressed in terms of density gradients, act in the same sense to reduce Slope Current transport. This indicates that coordinated regional changes of buoyancy and wind forcing acted together to reduce Slope Current transport during the 1990s. Particle trajectories further show that 10-40 % of Slope Current water is destined for the northern North Sea within 6 months of passing to the west of Scotland, with a general decline in this percentage over 1988-2007. Salinities in the Slope Current correspondingly decreased, evidenced in ocean analysis data. Further to the north, in the Atlantic Water conveyed by the Slope Current through the Faroe-Shetland Channel (FSC), salinity is observed to increase over this period while declining in the hindcast. The observed trend may have broadly compensated for a decline in the Atlantic inflow, limiting salinity

Analysis of gravity anomalies in the Ulleung Basin (East Sea/Sea of Japan) and its implications for the architecture of rift-dominated back-arc basin

NASA Astrophysics Data System (ADS)

Kim, Y. M.; Lee, S. M.

2016-12-01

Marginal basins located between the continent and arc islands often exhibit diverse style of opening, from regions that appear to have formed by well-defined and localized spreading center to those with less obvious zones of extension and a broad magmatic emplacement in the lower crust. The difference in the mode of back-arc opening may lead to a marked difference in crustal structure including its overall thickness and mechanical strength. The Ulleung Basin (UB) in the East Sea/Sea of Japan is considered to represent a continental rifting end-member of back-arc opening. However, compared to nearby Yamato Basin (YB) and Japan Basin (JB) in the NE corner of the sea, its structure and crustal characteristics are less well understood. This study examines the marine gravity anomalies of the UB in order to delineate the variations in crustal structure. Our analysis shows that the Moho depth from the sea surface varies from 16 km at the basin center to 22 km at the margins. However, within the basin center, the inferred thickness of the crust not including sediment is more or less the same (10-12 km), by varying only about 10-20% of the total thickness, contrary to the previous suggestions. The revelation that the UB has a thick but uniform thickness crust is consistent with previous observations using ocean bottom seismometers and is similar recent findings from the nearby YB. Another important feature is that small residual mantle gravity anomaly highs (40 mGal) exist in the northern part of the basin. These small highs trend in the NNE-SSW direction and thus corresponding to the orientation of the major tectonic structures on the Korean Peninsula, raising the possibility that they are the result of localized extension and extra crustal thinning at the time of basin formation. Alternatively, the presence of small magmatic underplating at the base of the crust, perhaps similar to high velocity region in the lower crust of YB, was also considered. According to our study

Quantifying the impact of the major driving mechanisms of inter-annual variability of salinity in the North Sea

NASA Astrophysics Data System (ADS)

Núñez-Riboni, Ismael; Akimova, Anna

2017-05-01

New 67-year long (1948-2014) gridded time series of salinity in the North Sea at all depths allowed to quantify, spatially resolved, the amount of inter-annual salinity variability explained by each of its driving mechanisms: sea level pressure (SLP), precipitation, river run-off, zonal and meridional winds and currents over the eastern North Atlantic. For the current data, not only annual averages but also their deviations, as measure of turbulence, were considered. Our results summarize and expand the knowledge gathered in the last 50 years about the mechanisms driving inter-annual variability of salinity in the North Sea. Three mechanisms, uncorrelated with each other and acting over separate regions of the North Sea, arise as most important: (1) River run-off from continental Europe explains 50-80% of inter-annual salinity variations at lag 0 in the Southern and German Bights and the Norwegian Trench up to the connection with the North Atlantic, down to the seabed near the coasts and to the deep Norwegian Trench (100 m); (2) Remote variations of salinity in the Rockall Trough explain 70% of salinity variations of the tongue of high salinity in the northwestern North Sea with a lag of one year and down the water column; (3) The Neva discharge explains 60% of salinity changes in Skagerrak and southern Norwegian trench at lag 0. An explanation for this correlation might be the Baltic freshwater outflow being modulated by the Neva discharge through intensification of the estuarine gravitational circulation. We confirmed known relations between river run-off, precipitation over continental Europe, SLP over northern Europe and zonal wind over western Europe. Linked to these changes, we found also changes of meridional wind north of Scotland favoring eastward Ekman transport of salty North Atlantic waters into the North Sea off the Norwegian coast. Excluding this only case, we found no significant correlation between wind-driven currents and North Sea salinity changes

Migration area of the Tsushima Warm Current Branches within the Sea of Japan: Implications from transport of 228Ra

NASA Astrophysics Data System (ADS)

Inoue, M.; Shirotani, Y.; Furusawa, Y.; Fujimoto, K.; Kofuji, H.; Yoshida, K.; Nagao, S.; Yamamoto, M.; Hamajima, Y.; Honda, N.; Morimoto, A.; Takikawa, T.; Shiomoto, A.; Isoda, Y.; Minakawa, M.

2017-07-01

We investigated lateral profiles of 228Ra (half-life; 5.75 years) activity and 228Ra/226Ra (1600 years) activity ratio using 241 surface water samples collected in/around the Sea of Japan and the East China Sea (ECS) during June-October of 2009-2014. In the ECS, the 228Ra/226Ra ratio in the surface waters exhibited markedly wide variation (<0.05-3.5) in June, predominantly reflecting the mixing between the 228Ra-rich continental shelf water and the 228Ra-depleted Kuroshio Current water. In July, the surface waters of the central Sea of Japan (135-138°E) became separated into three currents: the Offshore Branch of the Tsushima Warm Current (OBTWC) (228Ra/226Ra =0.7-1.2) at 39-41°N, the Coastal Branch of the TWC (CBTWC) ( 0.7) on the southern side, and sub-Arctic Current ( 0.7) on the northern side. From the central to northeastern Sea of Japan, the 228Ra/226Ra ratio at the surface (0.8-1.0) was within a range between that of the CBTWC and OBTWC. The fraction of continental shelf water in the CBTWC, OBTWC, and in their combined current was estimated to be 11-16%, 8%, and 10-11%, respectively.

Wasp-Waist Interactions in the North Sea Ecosystem

PubMed Central

Fauchald, Per; Skov, Henrik; Skern-Mauritzen, Mette; Johns, David; Tveraa, Torkild

2011-01-01

Background In a “wasp-waist” ecosystem, an intermediate trophic level is expected to control the abundance of predators through a bottom-up interaction and the abundance of prey through a top-down interaction. Previous studies suggest that the North Sea is mainly governed by bottom-up interactions driven by climate perturbations. However, few studies have investigated the importance of the intermediate trophic level occupied by small pelagic fishes. Methodology/Principal Findings We investigated the numeric interactions among 10 species of seabirds, two species of pelagic fish and four groups of zooplankton in the North Sea using decadal-scale databases. Linear models were used to relate the time series of zooplankton and seabirds to the time series of pelagic fish. Seabirds were positively related to herring (Clupea harengus), suggesting a bottom-up interaction. Two groups of zooplankton; Calanus helgolandicus and krill were negatively related to sprat (Sprattus sprattus) and herring respectively, suggesting top-down interactions. In addition, we found positive relationships among the zooplankton groups. Para/pseudocalanus was positively related to C. helgolandicus and C. finmarchicus was positively related to krill. Conclusion/Significance Our results indicate that herring was important in regulating the abundance of seabirds through a bottom-up interaction and that herring and sprat were important in regulating zooplankton through top-down interactions. We suggest that the positive relationships among zooplankton groups were due to selective foraging and switching in the two clupeid fishes. Our results suggest that “wasp-waist” interactions might be more important in the North Sea than previously anticipated. Fluctuations in the populations of pelagic fish due to harvesting and depletion of their predators might accordingly have profound consequences for ecosystem dynamics through trophic cascades. PMID:21829494

Distribution of slab-derived fluids around the edge of the Philippine Sea Plate from Central to Northeast Japan

NASA Astrophysics Data System (ADS)

Nakamura, Hitomi; Iwamori, Hikaru; Ishizuka, Osamu; Nishizawa, Tatsuji

2018-01-01

Marginal parts of a plate and subducting slab can play important roles in geodynamics. This is because in areas where a plate interacts with other plates or with the mantle thermal, geochemical, and mechanical interactions are expected. The Philippine Sea (PHS) slab that subducts beneath the Japan arcs has such an edge. To examine the relationship between arc magmatism and the slab edge in the transition zone from Northeast Japan to Central Japan, we investigated isotopic systematics of the regional volcanic rocks, incorporating data from literature and new data for five isotopic ratios of Sr, Nd, and Pb. The new data included major element compositions of 22 samples from the back-arc area, and 5 isotopic ratios for 6 samples selected from Pleistocene to early Quaternary epochs. Consequently, several findings were determined based on the spatial variation of the isotopic ratios and the estimated amount of slab-derived fluid: (1) the amount of fluid derived from the two subducting slabs (i.e., the Pacific slab and the PHS slab) decreases northward from a significantly high value ( 5 wt% fluid added to the source mantle), away from the seismically determined edge of the PHS slab; (2) the proportion of the PHS component in the total slab-derived fluid also decays northward; and (3) the PHS component spreads to the north beyond the seismically determined edge of the PHS slab. These observations strongly suggest that the existence of an aseismic PHS slab beneath southernmost parts of Northeast Japan delivers the PHS component to the arc magmatism. As was indicated by previous geodynamical studies, subduction of the PHS and PAC slabs may generate suction force towards the corner of mantle wedge, which might account for the large amount of fluid near the seismically determined slab edge as described in (1) above.

Comparisons between observations and numerical simulations of Japan (East) Sea flow and mass fields in 1999 through 2001

NASA Astrophysics Data System (ADS)

Mooers, Christopher N. K.; Bang, Inkweon; Sandoval, Francisco J.

2005-06-01

The Princeton Ocean Model (POM), as implemented for the Japan (East) Sea (JES) with mesoscale-admitting resolution is driven by seasonal throughflow and synoptic atmospheric forcing for 1999 through 2001. Temperature and salinity profiles from shipborne and PALACE float CTDs, and horizontal velocities at 800 m from PALACE float trajectories, plus horizontal velocities at 15 m from WOCE surface drifters for 1988 through 2001, are used to assess the performance of the numerical simulations for a base case. General agreement exists in the circulation at 15 and 800 m and the horizontal and vertical structure of the upper ocean temperature and salinity fields. The mean observed flow at 15 m defines the two branches of the Tsushima Warm Current and hints at the existence of a large cyclonic gyre over the Japan Basin, which the simulations also produce. The mean observed flow at 800 m defines a large cyclonic recirculation gyre over the Japan Basin that validates the simulated flow pattern. Variances of the observed and simulated flows at 15 and 800 m have similar patterns. The main discrepancies are associated with the strength of the seasonal thermocline and halocline and the location of the Subpolar Front. When smoother topography and smaller lateral friction are used in other cases, the thermocline and halocline strengthen, agreeing better with the observed values, and when 80% of total outflow transport is forced to exit through Soya Strait, the Subpolar Front extends along the coast to the north of Tsugaru Strait, which is an observed feature absent in the base case.

Phylogenetics, phylogeography and population genetics of North American sea ducks (tribe: Mergini)

USGS Publications Warehouse

Talbot, Sandra L.; Sonsthagen, Sarah A.; Pearce, John M.; Scribner, Kim T.

2015-01-01

Many environments occupied by North American sea ducks are remote and difficult to access, and as a result, detailed information about life history characteristics that drive population dynamics within and across species is limited. Nevertheless, progress on this front during the past several decades has benefited by the application of genetic technologies, and for several species, these technologies have allowed for concomitant tracking of population trends and genetic diversity, delineation of populations, assessment of gene flow among metapopulations, and understanding of migratory connectivity between breeding and wintering grounds. This chapter provides an overview of phylogenetic, phylogeographic, and population genetics studies of North American sea duck species, many of which have sought to understand the major and minor genetic divisions within and among sea duck species, and most of which have been conducted with the understanding that the maintenance of genetic variation in wild sea duck populations is fundamental to the group’s long-term persistence.

The study of mesoscale phenomena, winter monsoon clouds and snow area. [Sea of Japan

NASA Technical Reports Server (NTRS)

Tsuchiya, K. (Principal Investigator)

1975-01-01

The author has identified the following significant results. The clouds under a moderate winter monsoon situation taken with S190A camera reveal existence of clouds with band structure of various wavelengths. The wavelength ranges from 0.4 to 3.5 kms. There was a good relationship between the longitudinal cloud band and vertical wind shear. There was a distinct difference in size of clouds between the Japan Sea side or upwind side and the Pacific Ocean side or downwind side of the Japanese mainland. Large solid cumulus clusters have the size of 20 x 35 sq km over the Japan Sea off the coast of Hokuriku District. It was found that S190A aerial color pictures showing shadows of fair weather cumuli over the sea could be successfully used in estimating cloud height while S190A station 1 picture was more useful over the land since it could more clearly distinguish shadow from vegetation. The height of fair weather cumuli estimated from shadows agree with the lifted condensation level. It was also found that these pictures were effectively used in delineating snow cover area. S192 data, especially IR channel, were found to be effective in finding topography of nimbostratus.

Is ice-rafted sediment in a North Pole marine record evidence for perennial sea-ice cover?

PubMed

Tremblay, L B; Schmidt, G A; Pfirman, S; Newton, R; DeRepentigny, P

2015-10-13

Ice-rafted sediments of Eurasian and North American origin are found consistently in the upper part (13 Ma BP to present) of the Arctic Coring Expedition (ACEX) ocean core from the Lomonosov Ridge, near the North Pole (≈88° N). Based on modern sea-ice drift trajectories and speeds, this has been taken as evidence of the presence of a perennial sea-ice cover in the Arctic Ocean from the middle Miocene onwards (Krylov et al. 2008 Paleoceanography 23, PA1S06. (doi:10.1029/2007PA001497); Darby 2008 Paleoceanography 23, PA1S07. (doi:10.1029/2007PA001479)). However, other high latitude land and marine records indicate a long-term trend towards cooling broken by periods of extensive warming suggestive of a seasonally ice-free Arctic between the Miocene and the present (Polyak et al. 2010 Quaternary Science Reviews 29, 1757-1778. (doi:10.1016/j.quascirev.2010.02.010)). We use a coupled sea-ice slab-ocean model including sediment transport tracers to map the spatial distribution of ice-rafted deposits in the Arctic Ocean. We use 6 hourly wind forcing and surface heat fluxes for two different climates: one with a perennial sea-ice cover similar to that of the present day and one with seasonally ice-free conditions, similar to that simulated in future projections. Model results confirm that in the present-day climate, sea ice takes more than 1 year to transport sediment from all its peripheral seas to the North Pole. However, in a warmer climate, sea-ice speeds are significantly faster (for the same wind forcing) and can deposit sediments of Laptev, East Siberian and perhaps also Beaufort Sea origin at the North Pole. This is primarily because of the fact that sea-ice interactions are much weaker with a thinner ice cover and there is less resistance to drift. We conclude that the presence of ice-rafted sediment of Eurasian and North American origin at the North Pole does not imply a perennial sea-ice cover in the Arctic Ocean, reconciling the ACEX ocean core data with

Variability in the Correlation between Asian Dust Storms and Chlorophyll a Concentration from the North to Equatorial Pacific

PubMed Central

Tan, Sai-Chun; Yao, Xiaohong; Gao, Hui-Wang; Shi, Guang-Yu; Yue, Xu

2013-01-01

A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997–2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the <50 m China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54–0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For the >50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32–0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36). These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas. PMID:23460892

Biogeochemical Implications of Recent Changes in the Ventilation of the Japan/East Sea

NASA Astrophysics Data System (ADS)

Jenkins, W. J.

2006-12-01

The Japan/East Sea (JES) is a highly productive marine ecosystem that constitutes an important fisheries resource for a number of nations. As a weakly stratified marginal sea separated from the Pacific Ocean by shallow straits, the ventilation of the abyssal JES is remarkably susceptible to climate change. Not surprisingly, such changes have indeed been noted for the late-glacial and Holocene. Over the past half-century or more, there has been a trend toward increasing deep water temperatures, increasing dissolved inorganic nutrients, and decreasing dissolved oxygen levels that are consistent with a reduction in deep ventilation in recent decades. I present a minimum complexity model of the Japan Sea that utilize observations of the transient tracers CFCs, tritium, and 3He to place useful constraints on the character, magnitude, and timing of these changes. I describe these changes within the context of differing mechanisms for deep water formation and ventilation. The converse of ventilation is the return of deep nutrients to the surface ocean, which in turn forms the basis of the food pyramid, and hence the support for new primary production in this strategically important marginal sea. The tracer constrained model calculations suggest that the primary (convective) supply of inorganic nitrogen to the shallow JES reduced by nearly a factor of two (from 1.7 to 0.9 Tmoles) in the latter half of the 20^th century. I relate the changes in abyssal nutrient reflux to climatic modulation of water mass formation changes, and present the implications for water column remineralization processes. The implications of the large scale changes for the sustenance of fishery stocks is significant.

Reevaluation of mid-Pliocene North Atlantic sea surface temperatures

USGS Publications Warehouse

Robinson, Marci M.; Dowsett, Harry J.; Dwyer, Gary S.; Lawrence, Kira T.

2008-01-01

Multiproxy temperature estimation requires careful attention to biological, chemical, physical, temporal, and calibration differences of each proxy and paleothermometry method. We evaluated mid-Pliocene sea surface temperature (SST) estimates from multiple proxies at Deep Sea Drilling Project Holes 552A, 609B, 607, and 606, transecting the North Atlantic Drift. SST estimates derived from faunal assemblages, foraminifer Mg/Ca, and alkenone unsaturation indices showed strong agreement at Holes 552A, 607, and 606 once differences in calibration, depth, and seasonality were addressed. Abundant extinct species and/or an unrecognized productivity signal in the faunal assemblage at Hole 609B resulted in exaggerated faunal-based SST estimates but did not affect alkenone-derived or Mg/Ca–derived estimates. Multiproxy mid-Pliocene North Atlantic SST estimates corroborate previous studies documenting high-latitude mid-Pliocene warmth and refine previous faunal-based estimates affected by environmental factors other than temperature. Multiproxy investigations will aid SST estimation in high-latitude areas sensitive to climate change and currently underrepresented in SST reconstructions.

Timing of Neogene Manganese Deposit Formation in the Paleo-Japan Sea, northeast Japan

NASA Astrophysics Data System (ADS)

Ito, T.; Orihashi, Y.; Yanagisawa, Y.; Sakai, S.; Motoyama, I.; Kamikuri, S. I.; Komuro, K.; Suzuki, K.

2017-12-01

The generation ages of the two Neogene manganese deposits in northeast Japan were determined by diatom and radiolarian biostratigraphic analyses and zircon U-Pb dating. The manganese deposits analyzed were from the Kitaichi and Maruyama mines in the Fukaura district, northeast Japan. Manganese oxide layers of 0.5 m (Kitaichi) and 1.5 m (Maruyama) in thickness were predominantly composed of todorokite and occur conformably within volcanogenic sediments, which stratigraphically had correlated to middle Miocene in previous studies. The ages of the manganese oxide layers were 12.4 Ma. There was no time gap between the Kitaichi and the Maruyama manganese oxide layers, between the manganese oxide layer and the underlying tuffaceous sandstone in the Kitaichi mine, or within the manganese oxide layer of ca. 1.5 m thickness in the Maruyama mine. On the other hand, the overlying tuffaceous sandstone was dated at 4.5 Ma. The results suggest that the manganese oxide layers were formed immediately after the deposition of the tuffaceous sandstone at 12.4 Ma and that the restricted supply of volcanogenic and/or other detrital matter had kept for a long time (ca. 7 m.y.). The timing of the manganese deposit generation, 12.4 Ma, is identical to the age of the base of the Onnagawa Stage on the Nishikurosawa Stage in the Neogene stratotype section on the Japan Sea side, northeast Japan. And this is equivalent to the age of the start of diatom blooming. Paleogeographically, the manganese oxide deposition happened in a shallower area on a paleo-hill or a small island surrounded by stagnant mid to deep basins with diatom and organically carbon-rich, laminated, and fine-grained mud. It is highly probable that upwelling of mid to deep water rich in both dissolved manganese and nutrients is the trigger for the manganese deposit generation in shallower areas and the deposition of diatomaceous sediments in mid and deep basins. Eustatic regression might be the reason for the short

Volcanism and Tectonics of the Central Deep Basin, Sea of Japan

NASA Astrophysics Data System (ADS)

Lelikov, E. P.; Emelyanova, T. A.; Pugachev, A. A.

2018-01-01

The paper presents the results of a study on the geomorphic structure, tectonic setting, and volcanism of the volcanoes and volcanic ridges in the deep Central Basin of the Sea of Japan. The ridges rise 500-600 m above the acoustic basement of the basin. These ridges were formed on fragments of thinned continental crust along deep faults submeridionally crossing the Central Basin and the adjacent continental part of the Primorye. The morphostructures of the basin began to submerge below sea level in the Middle Miocene and reached their contemporary positions in the Pliocene. Volcanism in the Central Basin occurred mostly in the Middle Miocene-Pliocene and formed marginal-sea basaltoids with OIB (ocean island basalt) geochemical signatures indicating the lower-mantle plume origin of these rocks. The OIB signatures of basaltoids tend to be expressed better in the eastern part of the Central Basin, where juvenile oceanic crust has developed. The genesis of this crust is probably related to rising and melting of the Pacific superplume apophyse.

Marine sedimentary coring and high-quality, multi-proxy records in the high-latitude North Pacific: a synthesis of paleoceanographic cruise and research effort

NASA Astrophysics Data System (ADS)

Borreggine, M. J.; Myhre, S. E.; Smith-Mislan, A.; Davis, C. V.; Deutsch, C.

2016-12-01

We assessed sedimentary coring efforts, data acquisition and publications from the subpolar North Pacific and marginal seas from 1951-2015. We found a total of 1,249 sediment cores collected by American, French, Japanese and Russian research vessels across the Subarctic Pacific (639 cores), Alaskan Gyre (8 cores), Sea of Okhotsk (270 cores), Bering Sea (120 cores), and the Sea of Japan (212 cores). Of these, 27% are investigated in peer-reviewed publications; this fraction varies from the Subarctic Pacific (18%), Alaskan Gyre (100%), Sea of Okhotsk (33%), Bering Sea (57%), and the Sea of Japan (25%). We assess the biological, geochemical, isotopic, and stratigraphic lines of evidence available for these cores, alongside coring technology, location, depth, cruise and vessel metadata. Coring effort peaked in 1996, 2009, and 2010 where 86, 90, and 67 cores, respectively, were recovered in the five regions collectively. Piston cores are the most common (347 cores) of the 24 different coring technologies used in the last 64 years. Published sedimentation rates range across the Subarctic Pacific (0.132-208 cm/ka), Alaskan Gyre (9-10,000 cm/ka), Sea of Okhotsk (0.7-115.5 cm/ka), Bering Sea (3-250 cm/ka), and the Sea of Japan (0.5-25 cm/ka), with the highest rates in the Alaskan Gyre. Age model development has transitioned from singular techniques to multiproxy approaches. Recent chronologies are built using a mix of isotope stratigraphy, radiocarbon dating, magnetostratigraphy, biostratigraphy, tephrochronology, % opal, color, and lithophysical proxies. Out of 275 published chronologies for the North Pacific, 132 (48%) are built with radiocarbon dating. Sedimentary data in the North Pacific includes biological, geochemical, isotopic, and stratigraphic analyses, and we document all proxy evidence to-date across all cores assessed. This database of coring and publication provides a unique resource and comprehensive assessment to the paleoceanographic community, can be used

Scavenging processes of marine aerosols by sea fog over the northern North Pacific

NASA Astrophysics Data System (ADS)

Narita, Y.; Iwamoto, Y.; Yoshida, K.; Kondo, M.; Uematsu, M.

2007-12-01

Sea fog appears frequently over the subarctic North Pacific in summertime. Typical advection fog over this region may affect the distribution of natural and anthropogenic substances from lands as well as marine biogenic substances. To clarify the variation of chemical composition in fog water, size distribution of fog droplets and fog scavenging processes, investigation was conducted over the northern North Pacific, where sea fog appears frequently in summer, during the KH-04-3 cruise of R/V Hakuho-maru in 2004. The sea salt composition is governed 65% of total concentration of inorganic ions and the non-sea-salt (nss-) sulfate occupied 10 % in the 90 sea fog water samples. The average size distribution of liquid water content (LWC) of sea fog showed a bimodal pattern with peaks of 7.0 and 27.5 μm in diameter, while its distribution on land fog commonly showed a monomodal pattern. LWC, number concentrations of fog droplets and concentrations of sea salt composition were high at the edge of the fog area, and decreased toward the center of the fog area. The peak of LWC size distribution was shifted from 17.0 μm at the edge to 36.5 μm in the center area. Based on the relationship of chemical compositions between aerosols and fog droplets, nss-SO42- and NH 4 + in sea fog water consisted of 85 % of the coarse mode aerosol and 15 % of the fine mode by ion basis. The fog droplets are expected to deposit with growing of its droplet size with coagulation and adsorbing reactive gases as a function of the distance from the edge of the sea fog area. These results suggest that sea fog over the subarctic North Pacific is an important as a scavenger of natural and anthropogenic substances transported from the Asian continent and its nitrogen flux to the marine environment may stimulate phytoplankton growth.

Multi-model ensemble combinations of the water budget in the East/Japan Sea

NASA Astrophysics Data System (ADS)

HAN, S.; Hirose, N.; Usui, N.; Miyazawa, Y.

2016-02-01

The water balance of East/Japan Sea is determined mainly by inflow and outflow through the Korea/Tsushima, Tsugaru and Soya/La Perouse Straits. However, the volume transports measured at three straits remain quantitatively unbalanced. This study examined the seasonal variation of the volume transport using the multiple linear regression and ridge regression of multi-model ensemble (MME) methods to estimate physically consistent circulation in East/Japan Sea by using four different data assimilation models. The MME outperformed all of the single models by reducing uncertainties, especially the multicollinearity problem with the ridge regression. However, the regression constants turned out to be inconsistent with each other if the MME was applied separately for each strait. The MME for a connected system was thus performed to find common constants for these straits. The estimation of this MME was found to be similar to the MME result of sea level difference (SLD). The estimated mean transport (2.42 Sv) was smaller than the measurement data at the Korea/Tsushima Strait, but the calibrated transport of the Tsugaru Strait (1.63 Sv) was larger than the observed data. The MME results of transport and SLD also suggested that the standard deviation (STD) of the Korea/Tsushima Strait is larger than the STD of the observation, whereas the estimated results were almost identical to that observed for the Tsugaru and Soya/La Perouse Straits. The similarity between MME results enhances the reliability of the present MME estimation.

Regional Mapping and Resource Assessment of Shallow Gas Hydrates of Japan Sea - METI Launched 3 Years Project in 2013.

NASA Astrophysics Data System (ADS)

Matsumoto, R.

2014-12-01

Agency of Natural Resources and Energy of METI launched a 3 years shallow gas hydrate exploration project in 2013 to make a precise resource assessment of shallow gas hydrates in the eastern margin of Japan Sea and around Hokkaido. Shallow gas hydrates of Japan Sea occur in fine-grained muddy sediments of shallow subsurface of mounds and gas chimneys in the form of massive nodular to platy accumulation. Gas hydrate bearing mounds are often associated with active methane seeps, bacterial mats and carbonate concretions and pavements. Gases of gas hydrates are derived either from deep thermogenic, shallow microbial or from the mixed gases, contrasting with totally microbial deep-seated stratigraphically controlled hydrates. Shallow gas hydrates in Japan Sea have not been considered as energy resource due to its limited distribution in narrow Joetsu basin. However recently academic research surveys have demonstrated regional distribution of gas chimney and hydrate mound in a number of sedimentary basins along the eastern margin of Japan Sea. Regional mapping of gas chimney and hydrate mound by means of MBES and SBP surveys have confirmed that more than 200 gas chimneys exist in 100 km x 100 km area. ROV dives have identified dense accumulation of hydrates on the wall of half collapsed hydrate mound down to 30 mbsf. Sequential LWD and shallow coring campaign in the Summer of 2014, R/V Hakurei, which is equipped with Fugro Seacore R140 drilling rig, drilled through hydrate mounds and gas chimneys down to the BGHS (base of gas hydrate stability) level and successfully recovered massive gas hydrates bearing sediments from several horizons.

Avian Influenza Ecology in North Atlantic Sea Ducks: Not All Ducks Are Created Equal

PubMed Central

Hall, Jeffrey S.; Russell, Robin E.; Franson, J. Christian; Soos, Catherine; Dusek, Robert J.; Allen, R. Bradford; Nashold, Sean W.; TeSlaa, Joshua L.; Jónsson, Jón Eínar; Ballard, Jennifer R.; Harms, Naomi Jane; Brown, Justin D.

2015-01-01

Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology. PMID:26677841

Avian Influenza Ecology in North Atlantic Sea Ducks: Not All Ducks Are Created Equal.

PubMed

Hall, Jeffrey S; Russell, Robin E; Franson, J Christian; Soos, Catherine; Dusek, Robert J; Allen, R Bradford; Nashold, Sean W; TeSlaa, Joshua L; Jónsson, Jón Eínar; Ballard, Jennifer R; Harms, Naomi Jane; Brown, Justin D

2015-01-01

Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology.

Avian influenza ecology in North Atlantic sea ducks: Not all ducks are created equal

USGS Publications Warehouse

Hall, Jeffrey S.; Russell, Robin E.; Franson, J. Christian; Soos, Catherine; Dusek, Robert J.; Allen, R. Bradford; Nashold, Sean W.; Teslaa, Joshua L.; Jónsson, Jón Einar; Ballard, Jennifer R.; Harms, Naomi Jnae; Brown, Justin D.

2015-01-01

Wild waterfowl are primary reservoirs of avian influenza viruses (AIV). However the role of sea ducks in the ecology of avian influenza, and how that role differs from freshwater ducks, has not been examined. We obtained and analyzed sera from North Atlantic sea ducks and determined the seroprevalence in those populations. We also tested swab samples from North Atlantic sea ducks for the presence of AIV. We found relatively high serological prevalence (61%) in these sea duck populations but low virus prevalence (0.3%). Using these data we estimated that an antibody half-life of 141 weeks (3.2 years) would be required to attain these prevalences. These findings are much different than what is known in freshwater waterfowl and have implications for surveillance efforts, AIV in marine environments, and the roles of sea ducks and other long-lived waterfowl in avian influenza ecology.

Benthic Biotic Response to Climate Changes over the Last 700,000 Years, the Sea of Japan: Ostracode Assemblages from Site U1427, IODP Expedition 346

NASA Astrophysics Data System (ADS)

Huang, H. H. M.; Yasuhara, M.; Iwatani, H.; Alvarez Zarikian, C. A.; Bassetti, M. A.; Sagawa, T.

2016-12-01

The Sea of Japan is a marginal sea, semi-enclosed by the Eurasian Continent, Korean Peninsula, Japanese Islands, and shallow straits (water depth < 130 m). Marginal seas are ideal natural laboratories to study biotic responses to large-scale paleoclimate-ocean mechanisms as they are typically sensitive to glacial/interglacial and stadial/interstadial cycles. The modern oceanographic setting in the Sea of Japan is characterized by the influx of the Tsushima Warm Current (TWC) from the East China Sea, and this setting was formed 1.7 My ago by tectonic subsidence of the Tsushima Strait. The Sea of Japan, therefore, is an interesting research subject for studying the biotic response to orbital-scale climate changes and benthic faunal development under the influence of TWC. Here we present 700,000-year record of benthic biotic response to the paleoceanographic changes in the southern Sea of Japan based on ostracode assemblage reconstruction at IODP Site U1427. Five local extinction events were caused by extreme bottom conditions (mainly oxygen depletion) during the Ice Age Terminations I, II, IV, V, and VII. Primary and secondary ostracode assemblages were revealed by Q-mode k-means clustering, CABFAC factor analysis, and non-metric multidimensional scaling. The primary ostracode components, characterized by Krithe sawanensis and Cytheropteron hyalinosa, broadly reflect glacial/interglacial and high-latitude insolation cycles. In contrast, a faunal shift determined by the secondary faunal components was driven by the TWC enhancement at 300 ka.

Sea Level Budget along the East Coast of North America

NASA Astrophysics Data System (ADS)

Pease, A. M.; Davis, J. L.; Vinogradova, N. T.

2016-12-01

We analyzed tide gauge data, taken from 1955 to 2015, from 29 locations along the east coast of North America. A well-documented period of sea-level acceleration began around 1990. The sea level rate (referenced to epoch 1985.0) and acceleration (post-1990) are spatially and temporally variable, due to various physical processes, each of which is also spatially and temporally variable. To determine the sea-level budgets for rate and acceleration, we considered a number of major contributors to sea level change: ocean density and dynamics, glacial isostatic adjustment (GIA), the inverted barometer effect, and mass change associated with the Greenland Ice Sheet (GIS) and the Antarctic Ice Sheet (AIS). The geographic variability in the budgets for sea-level rate is dominated by GIA. At some sites, GIA is the largest contributor to the rate. The geographic variability in the budgets for sea-level acceleration is dominated by ocean dynamics and density and GIS mass loss. The figure below shows budgets for sea-level rate (left) and acceleration (right) for Key West, Fla., (top) and The Battery in New York City (bottom). The blue represents values (with error bar shown) estimated from tide gauge observations, and the yellow represents the total values estimated from the individual model contributions (each in red, green, cyan, pink, and black). The estimated totals for rate and acceleration are good matches to the tide-gauge inferences. To achieve a reasonable fit, a scaling factor (admittance) for the combined contribution of ocean dynamics and density was estimated; this admittance may reflect the low spatial sampling of the GECCO2 model we used, or other problems in modeling coastal sea-level. The significant contributions of mass loss to the acceleration enable us to predict that, if such mass-loss continues or increases, the character of sea-level change on the North American east coast will change in the next 50-100 years. In particular, whereas GIA presently

Large-scale forcing of the European Slope Current and associated inflows to the North Sea

NASA Astrophysics Data System (ADS)

Marsh, Robert; Haigh, Ivan; Cunningham, Stuart; Inall, Mark; Porter, Marie; Moat, Ben

2017-04-01

Drifters drogued at 50 m in the European Slope Current at the Hebridean shelf break follow a wide range of pathways, indicating highly variable Atlantic inflow to the North Sea. Slope Current pathways, timescales and transports over 1988-2007 are further quantified in an eddy-resolving ocean model hindcast. Particle trajectories calculated with model currents indicate that Slope Current water is largely "recruited" from the eastern subpolar North Atlantic. Observations of absolute dynamic topography and climatological density support theoretical expectations that Slope Current transport is to first order associated with meridional density gradients in the eastern subpolar gyre, which support a geostrophic inflow towards the slope. In the model hindcast, Slope Current transport variability is dominated by abrupt 25-50% reductions of these density gradients over 1996-1998. Concurrent changes in wind forcing, expressed in terms of density gradients, act in the same sense to reduce Slope Current transport. This indicates that coordinated regional changes of buoyancy and wind forcing acted together to reduce Slope Current transport during the 1990s. Particle trajectories further show that 10-40% of Slope Current water is destined for the northern North Sea within 6 months of passing to the west of Scotland, with a clear decline in this Atlantic inflow over 1988-2007. The influence of variable Slope Current transport on the northern North Sea is also expressed in salinity variations. A proxy for Atlantic inflow may be found in sea level records. Variability of Slope Current transport is implicit in mean sea level differences between Lerwick (Shetland) and Torshavn (Faeroes), in both tide gauge records and a longer model hindcast spanning 1958-2013. Potential impacts of this variability on North Sea biogeochemistry and ecosystems, via associated changes in temperature and seasonal stratification, are discussed.

The occurrence of macro- and mesoscopic methane hydrate in the eastern margin of Japan Sea

NASA Astrophysics Data System (ADS)

Matsumoto, R.; Kakuwa, Y.; Tanahashi, M.; Hiruta, A.

2016-12-01

Shallow methane hydrate is known to occur in muddy sediments that were deposited in the eastern margin of Japan Sea. In such settings, the hydrate occurs just below the seabed or is exposed directly on the seabed. Its presence is quite different from the pore-filling type of hydrate typically found in sandstone of the Pacific Ocean side of the Japanese islands. This presentation focuses on categorizing the distribution of gas hydrate in Japan Sea which, until recently, has been poorly understood. Macroscopic occurrence: Numerous gas chimney structures, which are characterized by an acoustic blanking on sub-bottom profiler images, have been discovered in the eastern margin of Japan Sea. We carried out seafloor drilling at several topographic highs that showed gas chimney structures. The results confirm that, while methane hydrate does not occur in the well-stratified part of SBP images, it does occur uniquely in the gas chimney structure-bearing mounds and pockmarks. Several horizons of methane hydrate-concentrated layers are identified by our LWD data and are traceable over lateral distances of as much as a kilometer.. In another case, the methane hydrate-concentrated layers occur stratigraphically in a regular manner with methane-derived carbonate nodules. We interpret the second case as one in which methane gas was supplied by regularly repeated movements of active fault(s). Mesoscopic occurrence: Methane hydrate is classified into 5 types that are readily observable in drilled cores: granular, nodular, platy, veiny and massive. The granular type is common over shallower intervals, while platy and veiny types are more common in the deeper intervals. Nevertheless, a significant fraction of the granular type may have possibly originated from the destruction and dissociation of other types during drilling and recovery. The massive type hydrate that characterizes highly-concentrated layers transitions to other types laterally as methane hydrate becomes poorly

Terrestrial biomarkers in the sediment of the East Sea (Japan Sea) since the MIS 11: implications for paleoproductivity and paleoclimatic changes

NASA Astrophysics Data System (ADS)

Hyun, S.; Suh, Y. J.; Woo, K. S.; Ikehara, M.

2014-12-01

Terrestrial biomarkers such as n-alkanes and cholesterol were analyzed to infer the variations of paleoproductivity and the corresponding paleoclimatologic information from the sediment of the Korean Plateau, East Sea (Japan Sea) since the Marine Isotope Stage (MIS) 11 (ca. 400 ka). Previous studies of SST variation have shown that glacial-interglacial scale changes were quite variable with the maximum range of 26oC in MIS 7, and the minimum range of 12oC during MIS 2 and 6. The distribution of terrestrial n-alkanes signatures is characterized by the occurrence of high odd number frequency with a minor contribution of specific compound (nC27 only). Average Chain Length (ACL) and Carbon Preferences Index (CPI), both of which are derived from n-alkane combination, show similar shifting between glacial and interglacial periods. This suggests that paleovegetation communities had been changed in responding to paleoclimatological variations, and the input amount of terrestrial compound was strongly linked with paleoclimatologic changes. In particular, depleted values of δ13Corg during MIS 2, 8 and 10 were coincident with lower nitrogen isotope values indicating local paleoceanographic effects such as paleoproductivity changes. Decoupling between δ13Corg and δ15Norg during MIS 1, 3, 5, 7 and coupling of the two during MIS 8 and 11 can be observed, which appear to be interpreted as local productivity changes. In particular, high abundance of cholesterol and C21 n-alkanes, which were derived from diatom, increased during interglacial periods. Therefore, alkenones, SST and n-alkanes signatures coincide with δ13Corg and δ15Norg variations during glacial-interglacial cycles and further strongly associated with cholesterol abundance suggesting that the paleoenvironmental conditions in East Sea during glacial-interglacial periods were sensitive not only to global climate changes but also to local paleceanographic variations. Surface water circulation around the Korea

Simulated wind-generated inertial oscillations compared to current measurements in the northern North Sea

NASA Astrophysics Data System (ADS)

Bruserud, Kjersti; Haver, Sverre; Myrhaug, Dag

2018-06-01

Measured current speed data show that episodes of wind-generated inertial oscillations dominate the current conditions in parts of the northern North Sea. In order to acquire current data of sufficient duration for robust estimation of joint metocean design conditions, such as wind, waves, and currents, a simple model for episodes of wind-generated inertial oscillations is adapted for the northern North Sea. The model is validated with and compared against measured current data at one location in the northern North Sea and found to reproduce the measured maximum current speed in each episode with considerable accuracy. The comparison is further improved when a small general background current is added to the simulated maximum current speeds. Extreme values of measured and simulated current speed are estimated and found to compare well. To assess the robustness of the model and the sensitivity of current conditions from location to location, the validated model is applied at three other locations in the northern North Sea. In general, the simulated maximum current speeds are smaller than the measured, suggesting that wind-generated inertial oscillations are not as prominent at these locations and that other current conditions may be governing. Further analysis of the simulated current speed and joint distribution of wind, waves, and currents for design of offshore structures will be presented in a separate paper.

Simulated wind-generated inertial oscillations compared to current measurements in the northern North Sea

NASA Astrophysics Data System (ADS)

Bruserud, Kjersti; Haver, Sverre; Myrhaug, Dag

2018-04-01

Measured current speed data show that episodes of wind-generated inertial oscillations dominate the current conditions in parts of the northern North Sea. In order to acquire current data of sufficient duration for robust estimation of joint metocean design conditions, such as wind, waves, and currents, a simple model for episodes of wind-generated inertial oscillations is adapted for the northern North Sea. The model is validated with and compared against measured current data at one location in the northern North Sea and found to reproduce the measured maximum current speed in each episode with considerable accuracy. The comparison is further improved when a small general background current is added to the simulated maximum current speeds. Extreme values of measured and simulated current speed are estimated and found to compare well. To assess the robustness of the model and the sensitivity of current conditions from location to location, the validated model is applied at three other locations in the northern North Sea. In general, the simulated maximum current speeds are smaller than the measured, suggesting that wind-generated inertial oscillations are not as prominent at these locations and that other current conditions may be governing. Further analysis of the simulated current speed and joint distribution of wind, waves, and currents for design of offshore structures will be presented in a separate paper.

Sea-ice evaluation of NEMO-Nordic 1.0: a NEMO-LIM3.6-based ocean-sea-ice model setup for the North Sea and Baltic Sea

NASA Astrophysics Data System (ADS)

Pemberton, Per; Löptien, Ulrike; Hordoir, Robinson; Höglund, Anders; Schimanke, Semjon; Axell, Lars; Haapala, Jari

2017-08-01

The Baltic Sea is a seasonally ice-covered marginal sea in northern Europe with intense wintertime ship traffic and a sensitive ecosystem. Understanding and modeling the evolution of the sea-ice pack is important for climate effect studies and forecasting purposes. Here we present and evaluate the sea-ice component of a new NEMO-LIM3.6-based ocean-sea-ice setup for the North Sea and Baltic Sea region (NEMO-Nordic). The setup includes a new depth-based fast-ice parametrization for the Baltic Sea. The evaluation focuses on long-term statistics, from a 45-year long hindcast, although short-term daily performance is also briefly evaluated. We show that NEMO-Nordic is well suited for simulating the mean sea-ice extent, concentration, and thickness as compared to the best available observational data set. The variability of the annual maximum Baltic Sea ice extent is well in line with the observations, but the 1961-2006 trend is underestimated. Capturing the correct ice thickness distribution is more challenging. Based on the simulated ice thickness distribution we estimate the undeformed and deformed ice thickness and concentration in the Baltic Sea, which compares reasonably well with observations.

Projected impact of climate change in the North and Baltic Sea. Results from dynamical downscaling of global CMIP climate scenarios

NASA Astrophysics Data System (ADS)

Gröger, Matthias; Maier-Reimer, Ernst; Mikolajewicz, Uwe; Sein, Dmitry

2013-04-01

Climate models have predicted strongest climate change impact for the mid/high lattiude areas. Despite their importance, shelves seas (which are supposed to account for more than 20% of global marine primary production and for up to 50% of total marine carbon uptake) are not adequately resolved in climate models. In this study, the global ocean general circulation and biogeochemistry model MPIOM/HAMOCC has been setup with an enhanced resolution over the NW European shelf (~10 km in the southern North Sea). For a realistic representation of atmosphere-ocean interactions the regional model REMO has been implemented. Thus, this model configuration allows a physically consistent simulation of climate signal propagation from the North Atlantic over the North Sea into the Baltic Sea since it interactively simulates mass and energy fluxes between the three basins. The results indicate substantial changes in hydrographic and biological conditions for the end of the 21st Century. A freshening by about 0.75 psu together with a surface warming of ~2.0 K and associated circulation changes in and outside the North Sea reduce biological production on the NW European shelf by ~35%. This reduction is twice as strong as the reduction in the open ocean. The underlying mechanism is a spatially well confined stratification feedback along the shelf break and the continental slope which reduces the winter mixed layer by locally more than 200 m compared to current conditions. As a consequence winter nutrient supply from the deep Atlantic declines between 40 and 50%. In addition to this, the volume transport of water and salt into the North Sea will slightly reduce (~10%) during summer. At the end of the 21st Century the North Sea appears nearly decoupled from the deep Atlantic. The projected decline in biological productivity and subsequent decrease of phytoplankton (by averaged 25%) will probably negatively affect the local fish stock in the North Sea. In the Baltic Sea the climate

Two centuries of observed atmospheric variability and change over the North Sea region

NASA Astrophysics Data System (ADS)

Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; van Oldenborgh, Geert Jan; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard

2015-04-01

Situated in northwestern Europe, the North Sea region is under influence of air masses from subtropical to arctic origin, and thus exhibits significant natural climate variability. As the land areas surrounding the North Sea are densely populated, climate change is an important issue in terms of e.g. coastal protection, fishery and trade. This study is part of the NOSCCA initiative (North Sea Region Climate Change Assessment) and presents observed variability and changes in atmospheric parameters during the last roughly 200 years. Circulation patterns show considerable decadal variability. In recent decades, a northward shift of storm tracks and increased cyclonic activity has been observed. There is also an indication of increased persistence of weather types. The wind climate is dominated by large multidecadal variability, and no robust long-term trends can be identified in the available datasets. There is a clear positive trend in near-surface temperatures, in particular during spring and winter. Over the region as a whole, no clear long-term precipitation trends are visible, although regional indications exist for an increased risk of extreme precipitation events.

The Dead Sea

NASA Technical Reports Server (NTRS)

2006-01-01

The Dead Sea is the lowest point on Earth at 418 meters below sea level, and also one of the saltiest bodies of water on Earth with a salinity of about 300 parts-per-thousand (nine times greater than ocean salinity). It is located on the border between Jordan and Israel, and is fed by the Jordan River. The Dead Sea is located in the Dead Sea Rift, formed as a result of the Arabian tectonic plate moving northward away from the African Plate. The mineral content of the Dead Sea is significantly different from that of ocean water, consisting of approximately 53% magnesium chloride, 37% potassium chloride and 8% sodium chloride. In the early part of the 20th century, the Dead Sea began to attract interest from chemists who deduced that the Sea was a natural deposit of potash and bromine. From the Dead Sea brine, Israel and Jordan produce 3.8 million tons potash, 200,000 tons elemental bromine, 45,000 tons caustic soda, 25, 000 tons magnesium metal, and sodium chloride. Both countries use extensive salt evaporation pans that have essentially diked the entire southern end of the Dead Sea.

With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet.

ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop

Free-living marine nematodes of Desmodorella and Zalonema (Nematoda: Desmodoridae) with description of two new species from the deep sea of the North Western Pacific.

PubMed

Fadeeva, Natalia; Mordukhovich, Vladimir; Zograf, Julia

2016-10-18

Examination of material recently collected by the German-Russian deep-sea expeditions has revealed that new species occur regularly in macro- and meiobenthic samples of the North-Western (NW) Pacific. In this paper, we report three desmodorid species of the genera Desmodorella and Zalonema from the NW Pacific. They were studied and described using both scanning electron microscopy (SEM) and light microscopy. Desmodorella tenuispiculum (Allgen, 1928) was found at several locations in the Sea of Japan during the Russian-German expedition SoJaBio (Sea of Japan Biodiversity Studies) cruise of RV ''Akademik M.V. Lavrentyev'' in 2010, at water depths ranging between 515 and 1500 m. Zalonema granda sp. nov. and Z. kamchatkaensis sp. nov. are characterized by having a larger body size in comparison with other species of the genus. Zalonema kamchatkaensis sp. nov. is characterized by having a convex cephalic capsule, subcephalic setae (3-4 μm long) located in the middle and at the posterior region of the cephalic capsule, very large spiral amphidial fovea with 2.1-2.2 turns, sexual dimorphism in amphideal fovea size (larger in males, 39-45 μm, than in females, 37-43 μm). Zalonema granda sp. nov. is characterized by having a very long body (3.3-4.3 mm), curved elongate spicules (1.4-1.6 body diameter long), with blade broadening anteriorly towards the rounded capitulum, and pointed distally; weakly developed tubular gubernaculum, and absence of pre-cloacal supplements.

Verification and recovery of thick deposits of massive gas hydrate from chimney structures, eastern margin of Japan Sea

NASA Astrophysics Data System (ADS)

Matsumoto, R.; Kakuwa, Y.; Snyder, G. T.; Tanahashi, M.; Yanagimoto, Y.; Morita, S.

2016-12-01

The initial scientific research that was carried out between 2004 and 2013 has provided us with invaluable evidence that gas hydrates occur widely on and below the sea floor down to approximately 30 mbsf within gas chimney structures in Japan Sea (Matsumoto, 2005; 2009). In 2013, METI (Ministry of Economy, Trade and Industry) launched a 3-year exploration project to assess the resource potential of shallow gas hydrates in Japan Sea. During the course of the project, Meiji University and AIST conducted: sea-going geophysical surveys with AUV, and high resolution 3D seismic and CSEM. These were followed by LWD and coring down to BSR depths, and coupled with a number of analyses and experiments. Regional mapping by MBES and SBP has confirmed 1742 gas chimneys in an area of 64,000km2 along the eastern margin of Japan Sea and around Hokkaido. Multiple LWD operations have revealed anomalous profiles such as extremely low natural gamma ray, high velocity Vp, and high resistivity Ro down to BSR depths, providing a strong indication that thick and massive gas hydrates exist throughout gas chimneys above the BSR. In several cases, conventional coring using 6-m long core liners recovered nearly 6 m long massive gas hydrates in several horizons adjacent to the anomalous LWD sites.The PCTB pressure coring system (Geotek Ltd) successfully cored 2-m long intervals of undisturbed, pressurized hydrate-bearing cores, providing valuable information about the in-situ occurrence and textural relations of hydrate and surrounding sediments. Full dissociation and slow degassing experiments of pressurized cores were conducted using onboard PCATS (Pressure core analysis and transfer system) to measure the amount of gases from hydrates. The mean volume fraction of gas hydrates in well-developed gas chimney structures is estimated to be 30 to 86 vol.% based on coupled PCATS and chloride anomaly profiles. Such an unusually high accumulation of gas hydrates in gas chimneys is assumed to have

Marine Fog over the Western Pacific Marginal Seas Based Upon Ship Observations for 1950 - 2007

NASA Astrophysics Data System (ADS)

Dorman, C. E.; Koracin, D. R.

2016-12-01

An analysis is presented of the marine fog distribution over the western Pacific marginal seas based upon the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) ship observations taken during 1950-2007. Fog occurrence is reported in routine weather reports that are encoded in an ICOADS ship observation. This includes the marginal seas of Okhotsk Sea, Japan Sea, Yellow Sea and South China Sea which have significant fog occurrences with values much greater than in the surrounding ocean with distinct seasonal trends but different generation mechanisms. The greatest occurrence is 55 % in Jun-Jul-Aug over the Okhotsk Sea followed by 28 % over the Japan Sea. This is seasonally controlled by the sea level pressure gradient moving air over a negative sea surface temperature gradient. During Dec-Jan-Feb, the SLP gradient reverses, moving cold, dry continental air over the Okhotsk and Japan Seas, eliminating any fog. The maximum fog over the Okhotsk Sea is over isolated locations with shallow water. In the Japan Sea, the most frequent fog occurs along the north side of the sea over a narrow shelf with the lowest SST of the entire Sea. In the Yellow Sea, the fog frequency peak is from Dec through May. In Mar-Apr-May the highest value is 18 % which is centered at 33 N 122 W while elevated values extend along the China coast to Taiwan. In Jun-Jul-Aug, highest values are mostly confined to the Yellow Sea. In Dec-Jan-Feb, decreased but significant fog occurrences extend along the entire China coast when the highest value in the Yellow Sea is 5 % and in South China Sea it is 6 %. The only other world marine fog occurrence analysis discovered by us is a US Department of Agriculture Jun-Jul-Aug marine fog frequency chart published in 1938 that does not show any fog in the Okhotsk Sea and misses most of the fog occurrence reported by ships in the Yellow Sea.

Artificial radionuclides in the surface waters of the Baltic Sea and the North Sea in the fall of 1984

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kadzhene, G.I.; Kleiza, I.V.; Korotkov, V.P.

1987-10-01

The authors compare data from the literature with data taken in the fall of 1984 on the concentrations of cesium 137, strontium 90, cesium 144, and tritium in the waters of the Baltic and North seas. Sampling was conducted along the coastal regions as well as offshore and the consequent concentration and distribution profiles are mapped. They attempt to assess the weight of meteorological and water current as well as seasonal factors on the determined levels and also point to possible sources of the isotopes, including nuclear power plants situated along Baltic and North Sea shorelines and an atmospheric testmore » of a thermonuclear bomb carried out by China.« less

Comparative Analysis of Japanese Three-Spined Stickleback Clades Reveals the Pacific Ocean Lineage Has Adapted to Freshwater Environments while the Japan Sea Has Not

PubMed Central

Ravinet, Mark; Takeuchi, Naoko; Kume, Manabu; Mori, Seiichi; Kitano, Jun

2014-01-01

Divergent selection and adaptive divergence can increase phenotypic diversification amongst populations and lineages. Yet adaptive divergence between different environments, habitats or niches does not occur in all lineages. For example, the colonization of freshwater environments by ancestral marine species has triggered adaptive radiation and phenotypic diversification in some taxa but not in others. Studying closely related lineages differing in their ability to diversify is an excellent means of understanding the factors promoting and constraining adaptive evolution. A well-known example of the evolution of increased phenotypic diversification following freshwater colonization is the three-spined stickleback. Two closely related stickleback lineages, the Pacific Ocean and the Japan Sea occur in Japan. However, Japanese freshwater stickleback populations are derived from the Pacific Ocean lineage only, suggesting the Japan Sea lineage is unable to colonize freshwater. Using stable isotope data and trophic morphology, we first show higher rates of phenotypic and ecological diversification between marine and freshwater populations within the Pacific Ocean lineage, confirming adaptive divergence has occurred between the two lineages and within the Pacific Ocean lineage but not in the Japan Sea lineage. We further identified consistent divergence in diet and foraging behaviour between marine forms from each lineage, confirming Pacific Ocean marine sticklebacks, from which all Japanese freshwater populations are derived, are better adapted to freshwater environments than Japan Sea sticklebacks. We suggest adaptive divergence between ancestral marine populations may have played a role in constraining phenotypic diversification and adaptive evolution in Japanese sticklebacks. PMID:25460163

Comparative analysis of Japanese three-spined stickleback clades reveals the Pacific Ocean lineage has adapted to freshwater environments while the Japan Sea has not.

PubMed

Ravinet, Mark; Takeuchi, Naoko; Kume, Manabu; Mori, Seiichi; Kitano, Jun

2014-01-01

Divergent selection and adaptive divergence can increase phenotypic diversification amongst populations and lineages. Yet adaptive divergence between different environments, habitats or niches does not occur in all lineages. For example, the colonization of freshwater environments by ancestral marine species has triggered adaptive radiation and phenotypic diversification in some taxa but not in others. Studying closely related lineages differing in their ability to diversify is an excellent means of understanding the factors promoting and constraining adaptive evolution. A well-known example of the evolution of increased phenotypic diversification following freshwater colonization is the three-spined stickleback. Two closely related stickleback lineages, the Pacific Ocean and the Japan Sea occur in Japan. However, Japanese freshwater stickleback populations are derived from the Pacific Ocean lineage only, suggesting the Japan Sea lineage is unable to colonize freshwater. Using stable isotope data and trophic morphology, we first show higher rates of phenotypic and ecological diversification between marine and freshwater populations within the Pacific Ocean lineage, confirming adaptive divergence has occurred between the two lineages and within the Pacific Ocean lineage but not in the Japan Sea lineage. We further identified consistent divergence in diet and foraging behaviour between marine forms from each lineage, confirming Pacific Ocean marine sticklebacks, from which all Japanese freshwater populations are derived, are better adapted to freshwater environments than Japan Sea sticklebacks. We suggest adaptive divergence between ancestral marine populations may have played a role in constraining phenotypic diversification and adaptive evolution in Japanese sticklebacks.

Space Radar Image of North Sea, Germany

NASA Image and Video Library

1999-05-01

This is an X-band image of an oil slick experiment conducted in the North Sea, Germany. The image is centered at 54.58 degrees north latitude and 7.48 degrees east longitude. This image was acquired by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on October 6, 1994, during the second flight of the spaceborne radar. The experiment was designed to differentiate between petroleum oil spills and natural slicks floating on the sea surface. Two types of petroleum oil and six types of oils resembling natural sea surface slicks were poured on the sea surface from ships and a helicopter just before the space shuttle flew over the region. At the bottom of the image is the Sylt peninsula, a famous holiday resort. Twenty-six gallons (100 liters) of diesel oil was dissipated due to wave action before the shuttle reached the site. The oil spill seen at the uppermost part of the image is about 105 gallons (400 liters) of heavy heating oil and the largest spill is about 58 gallons (220 liters) of oleyl alcohol, resembling a "natural oil" like the remaining five spills used to imitate natural slicks that have occurred offshore from various states. The volume of these other oils spilled on the ocean surface during the five experimental spills varied from 16 gallons to 21 gallons (60 liters to 80 liters). The distance between neighboring spills was about half a mile (800 meters) at the most. The largest slick later thinned out to monomolecular sheets of about 10 microns, which is the dimension of a molecule. Oceanographers found that SIR-C/X-SAR was able to clearly distinguish the oil slicks from algae products dumped nearby. Preliminary indications are that various types of slicks may be distinguished, especially when other radar wavelengths are included in the analysis. Radar imaging of the world's oceans on a continuing basis may allow oceanographers in the future to detect and clean up oil spills much more

Vertical nutrient fluxes, turbulence and the distribution of chlorophyll a in the north-eastern North Sea

NASA Astrophysics Data System (ADS)

Bendtsen, Jørgen; Richardson, Katherine

2017-04-01

During summer the northern North Sea is characterized by nutrient rich bottom water masses and nutrient poor surface layers. This explains the distribution of chlorophyll a in the water column where a subsurface maximum, referred to as the deep chlorophyll maximum (DCM), often is present during the growth season. Vertical transport of nutrients between bottom water masses and the well lit surface layer stimulates phytoplankton growth and this generally explains the location of the DCM. However, a more specific understanding of the interplay between vertical transports, nutrient fluxes and phytoplankton abundance is required for identifying the nature of the vertical transport processes, e.g the role of advection versus vertical turbulent diffusion or the role of localized mixing associated with mesoscale eddies. We present results from the VERMIX study in the north-eastern North Sea where nutrients, chlorophyll a and turbulence profiles were measured along five north-south directed transects in July 2016. A high-resolution sampling program, with horizontal distances of 1-10 km between CTD-stations, resolved the horizontal gradients of chlorophyll a across the steep bottom slope from the relatively shallow central North Sea ( 50-80 m) towards the deep Norwegian Trench (>700 m). Low oxygen concentrations in the bottom water masses above the slope indicated enhanced biological production where vertical mixing would stimulate phytoplankton growth around the DCM. Measurements of variable fluorescence (Fv/Fm) showed elevated values in the DCM which demonstrates a higher potential for electron transport in the Photosystem II in the phytoplankton cells, i.e. an indication of nutrient-rich conditions favorable for phytoplankton production. Profiles of the vertical shear and microstructure of temperature and salinity were measured by a VMP-250 turbulence profiler and the vertical diffusion of nutrients was calculated from the estimated vertical turbulent diffusivity and the

Regional and temporal changes in epizoobiontic bryozoan-communities of Flustra foliacea (Linnaeus, 1758) and implications for North Sea ecology

NASA Astrophysics Data System (ADS)

Bitschofsky, F.; Forster, S.; Scholz, J.

2011-02-01

Until recently, bryozoans have not been used as indicators for changes in bottom communities or climate control in the North Sea Basin, despite a 200-year history of bryozoan collecting. The epizoobiontic bryozoan fauna of Flustra foliacea (Linnaeus, 1758) was analysed on 51 sample stations kept in four German museums. The samples cover the entire North Sea and different time periods (1776-2008, mainly the period of 1904/1905 compared to 1980-87). Cluster analysis shows a differentiation into a northern and a southern North Sea assemblage. The northern assemblage is characterized by Amphiblestrum flemingii (Busk, 1854), Callopora dumerilii (Audouin, 1826) and Tricellaria ternata (Ellis & Solander, 1786), while the southern North Sea is characterized by Electra pilosa (Linnaeus, 1767), Crisia eburnea (Linnaeus, 1758) and Plagioecia patina (Lamarck, 1816). Spatial separation approximately follows the 50 m depth contour. The temporal distribution patterns of bryozoans are discussed in terms of NAO (North Atlantic Oscillation) and temperature variations.

Local adaptation and oceanographic connectivity patterns explain genetic differentiation of a marine diatom across the North Sea–Baltic Sea salinity gradient

PubMed Central

Sjöqvist, C; Godhe, A; Jonsson, P R; Sundqvist, L; Kremp, A

2015-01-01

Drivers of population genetic structure are still poorly understood in marine micro-organisms. We exploited the North Sea–Baltic Sea transition for investigating the seascape genetics of a marine diatom, Skeletonema marinoi. Eight polymorphic microsatellite loci were analysed in 354 individuals from ten locations to analyse population structure of the species along a 1500-km-long salinity gradient ranging from 3 to 30 psu. To test for salinity adaptation, salinity reaction norms were determined for sets of strains originating from three different salinity regimes of the gradient. Modelled oceanographic connectivity was compared to directional relative migration by correlation analyses to examine oceanographic drivers. Population genetic analyses showed distinct genetic divergence of a low-salinity Baltic Sea population and a high-salinity North Sea population, coinciding with the most evident physical dispersal barrier in the area, the Danish Straits. Baltic Sea populations displayed reduced genetic diversity compared to North Sea populations. Growth optima of low salinity isolates were significantly lower than those of strains from higher native salinities, indicating local salinity adaptation. Although the North Sea–Baltic Sea transition was identified as a barrier to gene flow, migration between Baltic Sea and North Sea populations occurred. However, the presence of differentiated neutral markers on each side of the transition zone suggests that migrants are maladapted. It is concluded that local salinity adaptation, supported by oceanographic connectivity patterns creating an asymmetric migration pattern between the Baltic Sea and the North Sea, determines genetic differentiation patterns in the transition zone. PMID:25892181

Effects of wave-induced forcing on a circulation model of the North Sea

NASA Astrophysics Data System (ADS)

Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian

2017-04-01

The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution NEMO model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force and the sea-state dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water level and current predictions.

New deep-sea free-living marine nematodes from the Sea of Japan: the genera Siphonolaimus and Halichoanolaimus (Nematoda: Chromadorea) with keys to species identifications.

PubMed

Zograf, Julia; Trebukhova, Yulia; Pavlyuk, Olga

2015-01-16

In deep-sea sediments from the Sea of Japan, two new species, Halichoanolaimus brandtae sp. n. and Siphonolaimus japonicus sp. n., were found and described. Siphonolaimus japonicus sp. n. is characterized by having short anterior sensillae, body length of 3670-4500 μm, buccal cavity with axial spear, and length of the spicules. Halichoanolaimus brandtae sp.n is characterized by the number of amphideal rings, long spicules, five precloacal supplements and by having a long cylindrical part of the tail. Keys to species level are provided. 

NASA Spots Typhoon Phanfone Affecting Japan

NASA Image and Video Library

2017-12-08

Over the weekend of Oct. 5 and 6, Typhoon Phanfone's center made landfall just south of Tokyo and passed over the city before exiting back into the Northwestern Pacific Ocean. NASA's Aqua satellite captured a picture of the typhoon as Tokyo braced for its large eye. On its way to mainland Japan, Phanfone struck Kadena Air Base on the island of Okinawa. According to the website for U.S. Air Force Kadena Air Base (www.kadena.af.mil), "One Airman is confirmed deceased and two more are missing after they were washed out to sea from the northwest coast of Okinawa at about 3:45 p.m. Oct. 5. An Airman that was found by the Japanese Coast Guard and pulled from the sea was later pronounced dead at a local hospital. HH-60s from Kadena Air Base and Japanese Coast Guard are continuing to search for the remaining two Airmen. Rough seas are complicating rescue efforts." Typhoon Phanfone's large eye made landfall near the city of Hamamatsu on Oct. 5 around 8 a.m. local time and then tracked north before turning eastward into the Pacific Ocean north of Tokyo. The MODIS instrument known as the Moderate Resolution Imaging Spectroradiometer captures amazing pictures from its orbit aboard NASA's Aqua satellite. MODIS snapped a picture of Typhoon Phanfone approaching Japan on Oct. 5 at 12:55 a.m. EDT. At that time, the Typhoon had already passed north of Okinawa, and was just south of the large island of Kyushu. The MODIS image revealed a large eye with powerful bands of thunderstorms spiraling into the center. On Oct. 6 by 0900 UTC (5 a.m. EDT), Phanfone had weakened from a typhoon to a tropical storm back over open waters of the Northwestern Pacific Ocean. Maximum sustained winds were near 60 knots (69.0 mph/111.1 kph). Phanfone was located near 38.0 north longitude and 145.0 east latitude. That's about 201 nautical miles (271 miles/372 km) south-southeast of Misawa Air Base, Japan. Phanfone was moving to the northeast at 40 knots (46 mph/74 kph). Forecasters at the Joint Typhoon

The internal consistency of the North Sea carbonate system

NASA Astrophysics Data System (ADS)

Salt, Lesley A.; Thomas, Helmuth; Bozec, Yann; Borges, Alberto V.; de Baar, Hein J. W.

2016-05-01

In 2002 (February) and 2005 (August), the full suite of carbonate system parameters (total alkalinity (AT), dissolved inorganic carbon (DIC), pH, and partial pressure of CO2 (pCO2) were measured on two re-occupations of the entire North Sea basin, with three parameters (AT, DIC, pCO2) measured on four additional re-occupations, covering all four seasons, allowing an assessment of the internal consistency of the carbonate system. For most of the year, there is a similar level of internal consistency, with AT being calculated to within ± 6 μmol kg- 1 using DIC and pH, DIC to ± 6 μmol kg- 1 using AT and pH, pH to ± 0.008 using AT and pCO2, and pCO2 to ± 8 μatm using DIC and pH, with the dissociation constants of Millero et al. (2006). In spring, however, we observe a significant decline in the ability to accurately calculate the carbonate system. Lower consistency is observed with an increasing fraction of Baltic Sea water, caused by the high contribution of organic alkalinity in this water mass, not accounted for in the carbonate system calculations. Attempts to improve the internal consistency by accounting for the unconventional salinity-borate relationships in freshwater and the Baltic Sea, and through application of the new North Atlantic salinity-boron relationship (Lee et al., 2010), resulted in no significant difference in the internal consistency.

Impacts of the north and tropical Atlantic Ocean on the Antarctic Peninsula and sea ice.

PubMed

Li, Xichen; Holland, David M; Gerber, Edwin P; Yoo, Changhyun

2014-01-23

In recent decades, Antarctica has experienced pronounced climate changes. The Antarctic Peninsula exhibited the strongest warming of any region on the planet, causing rapid changes in land ice. Additionally, in contrast to the sea-ice decline over the Arctic, Antarctic sea ice has not declined, but has instead undergone a perplexing redistribution. Antarctic climate is influenced by, among other factors, changes in radiative forcing and remote Pacific climate variability, but none explains the observed Antarctic Peninsula warming or the sea-ice redistribution in austral winter. However, in the north and tropical Atlantic Ocean, the Atlantic Multidecadal Oscillation (a leading mode of sea surface temperature variability) has been overlooked in this context. Here we show that sea surface warming related to the Atlantic Multidecadal Oscillation reduces the surface pressure in the Amundsen Sea and contributes to the observed dipole-like sea-ice redistribution between the Ross and Amundsen-Bellingshausen-Weddell seas and to the Antarctic Peninsula warming. Support for these findings comes from analysis of observational and reanalysis data, and independently from both comprehensive and idealized atmospheric model simulations. We suggest that the north and tropical Atlantic is important for projections of future climate change in Antarctica, and has the potential to affect the global thermohaline circulation and sea-level change.

150 years of ecosystem evolution in the North Sea - from pristine conditions to acidification

NASA Astrophysics Data System (ADS)

Pätsch, Johannes; Lorkowski, Ina; Kühn, Wilfried; Moll, Andreas; Serna, Alexandra

2010-05-01

The 3-d coupled physical-biogeochemical model ECOHAM was applied to the Northwest European Shelf (47° 41‘ - 63° 53' N, 15° 5' W - 13° 55' E) for the years 1860, 1960 and continuously for the time interval 1970 - 2006. From stable nitrogen isotope analysis in sediment cores of the German Bight in the southeastern part of the North Sea (inner shelf) we found the period before 1860 unaffected by anthropogenic river inputs of nitrogen. After this period the delta15N-ratios significantly increased from ~6 per mil to more than 8 per mil in recent sediments indicating eutrophication by anthropogenic nitrate mainly from intensive agriculture fertilization. We deduced from the successful simulation of delta15N patterns in recent sediments that during pristine conditions nitrogen loads of the main continental rivers were about 10% of the modern input while the deposition of inorganic atmospheric nitrogen was 28% of the recent atmospheric flux. The 1960-sediment exhibited similar delta15N-values as the recent sediment which allows the conclusion that eutrophication in the German Bight predates the 1960 period of rapidly increasing river loads. By comparing model results with observational data in the North Sea we analyzed the variability of simulated carbon fluxes (1970-2006) constituting the so called "shelf pump" which transports atmospheric CO2 via biological fixation, vertical export and advection into the adjacent North Atlantic. Even though the highly variable North Atlantic water-inflow which correlated with the North Atlantic Oscillation Index (NAOI) supplied the northern North Sea with strongly varying nutrient inputs, the interannual variability of the strength of the shelf pump was mainly governed by the variability of the southern basin's biological productivity. The net ecosystem production (NEP) in the southern North Sea varies around zero inducing CO2 exchange with the atmosphere which is near equilibrium. In the northern North Sea the strong positive

Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics.

PubMed

Zipkin, Elise F; Gardner, Beth; Gilbert, Andrew T; O'Connell, Allan F; Royle, J Andrew; Silverman, Emily D

2010-08-01

Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species-habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate

Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics

USGS Publications Warehouse

Zipkin, Elise F.; Gardner, Beth; Gilbert, Andrew T.; O'Connell, Allan F.; Royle, J. Andrew; Silverman, Emily D.

2010-01-01

Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species-habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate

Prevalence and molecular characterisation of Acanthocephala in pinnipedia of the North and Baltic Seas.

PubMed

Waindok, Patrick; Lehnert, Kristina; Siebert, Ursula; Pawliczka, Iwona; Strube, Christina

2018-04-01

Harbour seals ( Phoca vitulina ) and grey seals ( Halichoerus grypus ) are final hosts of acanthocephalans in the German North and Baltic Seas. Parasitic infections in seals can cause pathological changes, which may result in deteriorated health of the host. Common gastrointestinal parasites of harbour and grey seals are acanthocephalans and a number of 275 of 2460 (11.2%) investigated seals from 1996 to 2013 were infected with Corynosoma spp. (Acanthocephala, Polymorphidae). The prevalence showed a wave-like pattern: it increased from 1.2% and 0.4% in 1996 and 1997, respectively, to 23.9% during the second phocine distemper epizootic in 2002 and decreased to 6.2% in 2004. In 2005, prevalence peaked again with 25.0% followed by a decrease to 9.3% in 2009 and an increase to 38.5% in 2012. Statistical analysis revealed that harbour seals originating from the North Sea showed a higher prevalence than grey seals, whereas no significant difference between grey and harbour seals from the Baltic Sea was observed. Furthermore, juvenile pinnipedia from the North Sea were significantly less infected with Corynosoma spp. than seals older than seven month. Molecular species identification as well as phylogenetic relationship analysis among the detected Corynosoma species were achieved by sequencing and comparisons of the ribosomal ITS1-5.8S-ITS2-complex and cytochrome-c-oxidase I gene. Molecular analysis resulted in a newly arranged distribution of Acanthocephala in the North Sea as in contrast to previous studies, C. strumosum could not be confirmed as predominant species. Instead, C. magdaleni and a C. magdaleni isolate (isolate Pv1NS) with an atypical number of longitudinal rows of hooks at the proboscis were detected. Furthermore, morphological and molecular analyses indicate the possible finding of a cryptic species (Candidatus Corynosoma nortmeri sp. nov.).

Distribution and sea-to-air fluxes of volatile halocarbons in the Bohai Sea and North Yellow Sea during spring.

PubMed

He, Zhen; Liu, Qiu-Lin; Zhang, Ying-Jie; Yang, Gui-Peng

2017-04-15

Concentrations of volatile halocarbons (VHCs), such as CHBr 2 Cl, CHBr 3 , C 2 HCl 3 , and C 2 Cl 4 , in the Bohai Sea (BS) and North Yellow Sea (NYS) were measured during the spring of 2014. The VHC concentrations varied widely and decreased with distance from the coast in the investigated area, with low values observed in the open sea. Depth profiles of the VHCs were characterized by the highest concentration generally found in the upper water column. The distributions of the VHCs in the BS and NYS were clearly influenced by the combined effects of biological production, anthropogenic activities, and riverine input. The sea-to-air fluxes of CHBr 2 Cl, CHBr 3 , C 2 HCl 3 , and C 2 Cl 4 in the study area were estimated to be 47.17, 56.63, 162.56, and 104.37nmolm -2 d -1 , respectively, indicating that the investigated area may be a source of atmospheric CHBr 2 Cl, CHBr 3 , C 2 HCl 3 , and C 2 Cl 4 in spring. Copyright © 2017 Elsevier B.V. All rights reserved.

Anthropogenic 129I in the North Pacific, Bering and Chukchi Seas, and Arctic Ocean in 2012-2013

NASA Astrophysics Data System (ADS)

Nagai, H.; Hasegawa, A.; Yamagata, T.; Kumamoto, Y.; Nishino, S.; Matsuzaki, H.

2015-10-01

Most of anthropogenic 129I in marine environment are due to discharge from the nuclear fuel reprocessing facilities at Sellafield (U.K.) and La Hague (France) for past few decades. The discharge raised 129I concentration in seawaters in the North Atlantic and Arctic Oceans to more than 109 atoms L-1, which is two orders of magnitude higher than that in other region. Recently, in March 2011, a large quantity of 129I was released into the western North Pacific due to the Fukushima Daiichi Nuclear Power Plant (F1NPP) accident. To evaluate the influence of these events, we have measured 129I concentration in seawaters in the northern North Pacific Ocean, Bering and Chukchi Seas, and Arctic Ocean in 2012-2013. The 129I concentrations were 1.0-1.8 × 107 atoms L-1 in the surface waters in the vicinity of 47°N 150°E-130°W North Pacific Ocean, Bering Sea, and Chukchi Sea (<74°N), which are equal to or lower than the 129I concentration level in surface water in the North Pacific Ocean before the F1NPP accident. The vertical profiles in the North Pacific were almost same as that observed in the western North Pacific before the F1NPP accident. The 129I distribution in seawater in the North Pacific to the Chukchi Sea revealed no significant increase of 129I concentration caused by the F1NPP accident. The 129I concentrations were 13-14 × 107 atoms L-1 in surface waters and 80 × 107 atoms L-1 at depths of 300 and 800 m in the Arctic Ocean.

Effects of wave-induced forcing on a circulation model of the North Sea

NASA Astrophysics Data System (ADS)

Staneva, Joanna; Alari, Victor; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian

2017-01-01

The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution Nucleus for European Modelling of the Ocean (NEMO) model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force, the sea-state-dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water-level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state-dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25-27 October 2013), and about a month later, the storm Xaver (5-7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20-30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water-level and current predictions.

Plate convergence and deformation, North Luzon Ridge, Philippines

NASA Astrophysics Data System (ADS)

Lewis, Stephen D.; Hayes, Dennis E.

1989-10-01

Marine geophysical and earthquake seismology data indicate that the North Luzon Ridge, a volcano-capped bathymetrie ridge system that extends between Luzon and Taiwan, is presently undergoing deformation in response to the relative motion between the Asian and Philippine Sea plates. Plate motion models predict convergence along the western side of the Philippine Sea plate, from Japan in the north to Indonesia in the south, and most of this plate margin is defined by active subduction zones. However, the western boundary of the Philippine Sea plate adjacent to the North Luzon Ridge shows no evidence of an active WNW-dipping subduction zone; this is in marked contrast to the presence of both the Philippine Trench/East Luzon Trough subduction zones to the south and the Ryukyu Trench subduction zone to the north. Crustal shortening, in response to ongoing plate convergence in the North Luzon Ridge region, apparently takes place through a complex pattern of strike-slip and thrust faulting, rather than by the typical subduction of oceanic lithosphere along a discreet zone. The curvilinear bathymetrie trends within the North Luzon Ridge represent the traces of active faults. The distribution of these faults, mapped by both multichannel and single-channel seismic reflection methods and earthquake seismicity patterns and focal mechanism solutions, suggest that right-lateral, oblique-slip faulting occurs along NE-trending faults, and left-lateral, oblique-slip faulting takes place on N- and NNW-trending faults. The relative plate convergence accommodated by the deformation of the North Luzon Ridge will probably be taken up in the future by the northward-propagating East Luzon Trough subduction zone.

Assessment of undiscovered conventional oil and gas resources in the West Korea Bay–North Yellow Sea Basin, North Korea and China, 2017

USGS Publications Warehouse

Schenk, Christopher J.; Tennyson, Marilyn E.; Mercier, Tracey J.; Hawkins, Sarah J.; Finn, Thomas M.; Gaswirth, Stephanie B.; Marra, Kristen R.; Klett, Timothy R.; Le, Phuong A.; Leathers-Miller, Heidi M.; Woodall, Cheryl A.

2017-07-11

Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered, technically recoverable conventional resources of 1.1 billion barrels of oil and 2.2 trillion cubic feet of gas in the West Korea Bay–North Yellow Sea Basin, North Korea and China.

Grains of Nonferrous and Noble Metals in Iron-Manganese Formations and Igneous Rocks of Submarine Elevations of the Sea of Japan

NASA Astrophysics Data System (ADS)

Kolesnik, O. N.; Astakhova, N. V.

2018-01-01

Iron-manganese formations and igneous rocks of submarine elevations in the Sea of Japan contain overlapping mineral phases (grains) with quite identical morphology, localization, and chemical composition. Most of the grains conform to oxides, intermetallic compounds, native elements, sulfides, and sulfates in terms of the set of nonferrous, noble, and certain other metals (Cu, Zn, Sn, Pb, Ni, Mo, Ag, Pd, and Pt). The main conclusion that postvolcanic hydrothermal fluids are the key sources of metals is based upon a comparison of the data of electron microprobe analysis of iron-manganese formations and igneous rocks dredged at the same submarine elevations in the Sea of Japan.

Carbon fluxes in North American coastal and shelf seas: Current status and trends

NASA Astrophysics Data System (ADS)

Fennel, K.; Alin, S. R.; Barbero, L.; Evans, W.; Martin Hernandez-Ayon, J. M.; Hu, X.; Lohrenz, S. E.; Muller-Karger, F. E.; Najjar, R.; Robbins, L. L.; Shadwick, E. H.; Siedlecki, S. A.; Steiner, N.; Turk, D.; Vlahos, P.; Wang, A. Z.

2016-12-01

Coastal and shelf seas represent an interface between all major components of the global carbon cycle: land, atmosphere, marine sediments and the ocean. Fluxes and transformations of carbon in coastal systems are complex and highly variable in space and time. The First State of the Carbon Cycle Report (http://cdiac.ornl.gov/SOCCR/final.html, Chapter 15, Chavez et al. 2007) concluded that carbon budgets of North American ocean margins were not well quantified because of insufficient observations and the complexity and highly localized spatial variability of coastal carbon dynamics. Since then significant progress has been made through the expansion of carbon observing networks, the implementation of modeling capabilities, and national and international coordination and synthesis activities. We will review the current understanding of coastal carbon fluxes around the North American continent including along the Atlantic and Pacific coasts, the northern Gulf of Mexico, and the North American Arctic region and provide a compilation of regional estimates of air-sea fluxes of CO2. We will discuss generalizable patterns in coastal air-sea CO2 exchange and other carbon fluxes as well as reasons underlying spatial heterogeneity. After providing an overview of the principal modes of carbon export from coastal systems, we will apply these mechanisms to the North American continent, and discuss observed and projected trends of key properties and fluxes. The presentation will illustrate that despite significant advances in capabilities and understanding, large uncertainties remain.

Triassic structural and stratigraphic evolution of the Central German North Sea sector

NASA Astrophysics Data System (ADS)

Wolf, Marco; Jähne-Klingberg, Fabian

2017-04-01

The subsurface of the Central German North Sea sector is characterized by a complex sequence of tectonic events that span from the Permo-Carboniferous initiation of the Southern Permian Basin to the present day. The Triassic period is one of the most prominent stratigraphic intervals in this area due to alternating phases of relatively tectonic quiescence and intense tectonic activity with the development of grabens, salt-tectonics movements, various regional and local erosional events and strong local and regional changes in subsidence over time. The heterogeneous geological history led to complex structural and lithological patterns. The presented results are part of a comprehensive investigation of the Central German North Sea sector. It was carried out within the scope of the project TUNB (www.bgr.bund.de). The main goal was to enhance the understanding of the Triassic geological development in the area of interest due to detailed seismic interpretation of several hundred 2D seismic lines and as well 3D seismic data sets. A seismostratigraphic concept was used to interpret most formations of the Triassic resulting in a detailed subdivision of the Triassic unit. Depth and thickness maps for every stratigraphic unit and geological cross sections provided new insights regarding an overall basin evolution as well as the timing and mechanisms of rifting and salt-tectonics. New results concerning the evolution of the Keuper in the German North Sea and especially the Triassic evolution of the Horn Graben, as one of the major Triassic rift-structures in the North Sea, will be highlighted. We will show aspects of strong tectonic subsidence in the Horn Graben in the Lower Triassic. In parts of the study area, halotectonic movements started in the Upper Triassic, earlier than previously proposed. Besides mapping of regional seismic reflectors, distinct sedimentary features like fluvial channel systems of the Stuttgart formation (Middle Keuper) or subrosion-like structures

Exchanges between the open Black Sea and its North West shelf

NASA Astrophysics Data System (ADS)

Shapiro, Georgy; Wobus, Fred; Zhou, Feng

2014-05-01

Exchanges between the vast NW shelf and the deep basin of the Black Sea play a significant role in maintaining the balance of nutrients, heat content and salinity of the shelf waters. Nearly 87 % of the Black Sea is entirely anoxic below 70 to 200m and contains high levels of hydrogen sulphide (Zaitsev et al, 2001), and this makes the shelf waters particularly valuable for maintaining the Black Sea ecosystem in good health. The increase in salinity of shelf waters occurs partially due to exchanges with more saline open sea waters and represents a threat to relics and endemic species. The shelf-break is commonly considered the bottle-neck of the shelf-deep sea exchanges (e.g. (Huthnance, 1995, Ivanov et al, 1997). Due to conservation of potential vorticity, the geostrophic currents flow along the contours of constant depth. However the ageostrophic flows (Ekman drift, mesoscale eddies, filaments, internal waves) are not subject to the same constraints. It has been shown that during the winter well mixed cold waters formed on the North West shelf propagate into the deep sea, providing an important mechanism for the replenishment of the Cold Intermediate Layer ( Staneva and Stanev, 1997). However, much less is known about exchanges in the warm season. In this study, the transports of water, heat and salt between the northwestern shelf and the adjacent deep basin of the Black Sea are investigated using a high-resolution three-dimensional primitive equation model, NEMO-SHELF-BLS (Shapiro et al, 2013). It is shown that during the period from April to August, 2005, both onshore and offshore cross-shelf break transports in the top 20 m were as high as 0.24 Sv on average, which was equivalent to the replacement of 60% of the volume of surface shelf waters (0 - 20 m) per month. Two main exchange mechanisms are studied: (i) Ekman transport, and (ii) transport by mesoscale eddies and associated meanders of the Rim Current. The Ekman drift causes nearly uniform onshore or

Analysis of gravity anomalies in the Ulleung Basin (East Sea/Sea of Japan) and its implications for the crustal structure of rift-dominated back-arc basin

NASA Astrophysics Data System (ADS)

Kim, Yoon-Mi; Lee, Sang-Mook

2018-01-01

The Ulleung Basin (UB), one of three major basins in the East Sea/Sea of Japan, is considered to represent a continental-rifting end-member of back-arc basin system, but is much less understood compared to the nearby Yamato Basin (YB) and Japan Basin (JB). This study examines the gravity anomalies of the UB since the variation in crustal thickness can provide important insights on the mode of extension during basin opening. Our analysis shows that the Moho depth (from the sea surface) varies from 16 km at the basin center to 22 km at the edges. However, within the central part of the basin, the crustal thickness (not including sediment) is more or less the same (10-12 km), by varying only about 10-20% of the total thickness, contrary to the previous suggestions. Our finding of anomalous but uniformly thick crust is consistent with the recent seismic results from the YB (14 km on average). A mantle residual gravity anomaly high (∼20 mGal) exists in the northeastern part of the UB. This feature is interpreted as the location of maximum extension (slightly thinner crust by ∼1 km). Together with another moderate gravity high to the southwest, the two anomalies form a NNE-SSW line, which corresponds to the direction of the major tectonic structures of the Korean Peninsula. We argue that the a massive magmatic emplacement took place extensively in the lower crust of the UB during the opening, significantly increasing its overall thickness to almost twice as that of the JB where a mid-ocean-ridge style seafloor spreading occurred. Two important post-opening processes took place after the formation of uniformly thick crust: post-rift volcanic intrusions in the north, especially in its northeast sections but had little effect on the residual gravity anomaly itself, and the deflection of crust in response to differential sediment loading towards the south, producing the median high in the basement in response to the flexural bending. We also conducted a simple test to

2011 Great East Japan tsunami in Okhotsk Sea region: numerical modelings and observation data

NASA Astrophysics Data System (ADS)

Kostenko, Irina; Zaytsev, Andrey; Yalciner, Ahmet; Pelinovsky, Efim

2013-04-01

The 11 March, 2011 Great East Japan Earthquake with Mw: 9.0 occurred at 05:46:23 UTC with its epicenter estimated at 38.322_N, 142.369_E, and focal depth of 32 km (USGS, 2011). Tsunami waves propagated in Pacific Ocean to all directions. At Russian coast the highest waves were observed in the Kuril Islands (Malokurilskoye, Kunashir Island) which located in between Pacific ocean and the Okhotsk Sea. Kuril island provides limited transmission of tsunami waves from Pacific ocean. tsunami In 2011 Great East Japan Earthquake and Tsunami event, the maximum amplitude of the tsunami was observed as 3 m in Kuril islands. However, tsunami arrived Okhotsk Sea losing a significant amount of energy. Therefore the tsunami amplitudes at the coast of the Okhotsk Sea were smaller. In order to estimate the level of energy loss while passing through the narrow straits of the Kuril Islands, a series of numerical simulations was done by using tsunami numerical code NAMI DANCE. Ten largest earthquake shocks capable of generating tsunami were used as inputs of tsunami sources in the modeling. Hence the relation between the transmission of tsunami and the dimensions of the straits are compared and discussed. Finally the characteristics of tsunami propagation (arrival time and coastal amplification) at the coast in the Okhotsk Sea. The varying grid structure is used in numerical modeling in order to make finer analysis of tsunami passing through narrow straits of the Kuril Islands. This allows to combine exactly the installation locations of stationary and computational gauges. The simulation results are compared with the observations. The linear form of shallow water equations are used in the deep ocean region offshore part of the Sea of Okhotsk. Boussinesq type equations were also used at the near shore area in simulations. Since the Okhotsk Sea Results are a semi enclosed basin, the reflection characteristics at the coastal boundaries may be important. The numerical experiments are also

Sea-level variability in the Common Era along the Atlantic coast of North America

NASA Astrophysics Data System (ADS)

Kemp, A.; Kopp, R. E.; Horton, B.; Little, C. M.; Engelhart, S. E.; Mitrovica, J. X.

2017-12-01

Common Era relative sea-level trends on the margins of the North Atlantic Ocean vary through time and across space as a result of simultaneous global (basin-wide)-, regional- (linear and non-linear), and local-scale processes. A growing suite of relative sea-level reconstructions derived from dated salt-marsh (and mangrove) sediment on the Atlantic coast of North America provides an opportunity to quantify the contributions from several physical processes to Common Era sea-level trends. In particular, this coastline is susceptible to relative sea-level changes caused by melting of the Greenland Ice Sheet and redistribution of existing ocean mass on timescales of days to centuries by evolving patterns and strengths of atmospheric and oceanic circulation. Using a case study from Newfoundland, Canada, we demonstrate how high-resolution (decadal- and decimeter-scale) relative sea level reconstructions are produced from sequences of salt-marsh sediment that were deposited under conditions of long-term sea-level rise. We use an expanded database of Common Era relative sea-level reconstructions from the Atlantic coast of North America that spans locations from Newfoundland to the southern Florida to identify spatial and temporal patterns of change. A spatio-temporal statistical model enables us to decompose each reconstruction (with uncertainty) into contributions from global-, regional- (linear and non-linear), and local-scale processes. This analysis shows that spatially-variable glacio-isostatic adjustment was the primary driver of sea-level change. The global signal is dominated by the onset of anthropogenic sea-level rise in the late 19th century, which caused the 20th century to experience a faster rate of rise than any of the preceding 26 centuries. Differentiating between regional non-linear and local-scale processes is a challenging using an inherently sparse network of reconstructions. However, we show that sites south of Cape Hatteras have sea-level histories

The Minor Rivers of Black Sea North-Western Coast

NASA Astrophysics Data System (ADS)

Alyukaeva, Alevtina

2017-04-01

The generalisations and conclusions have been done based on the expeditional monitoring of minor rivers of the Russian Federation Black Sea Coast for summer-autumn mean water in 2011-2015. The length of coastal line under monitoring was 300 km with 78 rivers with length no longer, then 50 km. The monitoring task was to establish the natural background of river effluent for the region under study. The observation parameters are physical measures (temperature, pH, Eh), solution (salts) and suspension forms of effluent (feculence, suspension chemical composition). 1. The tendency to decrease minor river water temperature at isthmus correspondent to movement from north-west to south-east along the coastal line. The causes are the growing length of the rivers and steepness of the relief along the Black Sea Caucasus. 2. The dependence between the size of coagulated suspension and water temperature is established. Moreover the intensive mix is not able to compensate the negative influence of the low temperature. 3. The value of hydrogen index, mineralization and specific electric conductivity for minor river are growing from north-west to south-east along the coastal line. 4. By the main ionic composition of the minor rivers of Black Sea north-eastern coast can be classified as hydrocarbonate. The main characteristic (marker) of colt composition for the region is the sensible concentrations of potassium and sodium. 5. The amount of suspension substance in the river water and its feculence changes between 50 mg/dm3 дo 280 mg/dm3. In particle size distribution composition of river suspensions the politic fractions (up to 70%) are prevailed, sand and silt fractions are presented less (25%). 6. Suspension form content of microelements depends on general amount of suspension in river water. The suspension form migration is significant for lead, cobalt, tin and silver. Other metals "prefer" the solution forms and can be arranged approximately in the following: vanadium

Spatio-temporal variability of the North Sea cod recruitment in relation to temperature and zooplankton.

PubMed

Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

2014-01-01

The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability.

Spatio-Temporal Variability of the North Sea Cod Recruitment in Relation to Temperature and Zooplankton

PubMed Central

Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

2014-01-01

The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability. PMID:24551103

Mercury species in dab (Limanda limanda) from the North Sea, Baltic Sea and Icelandic waters in relation to host-specific variables.

PubMed

Lang, Thomas; Kruse, Reinhard; Haarich, Michael; Wosniok, Werner

2017-03-01

In the framework of the ICON project (Integrated Assessment of Contaminant Impacts on the North Sea), muscle tissue from a total of 135 common dab (Limanda limanda) (20-28 cm total length) was collected in seven offshore sampling areas in the North Sea, at Iceland and in the Baltic Sea during Aug/Sept and December 2008 for a chemical mercury speciation analysis by means of gas chromatography and detection by cold vapour atomic fluorescence spectroscopy (GC-CVAFS). There was a highly significant correlation between concentrations of methylmercury (MeHg + ) and inorganic mercury (Hg 2+ ) in individual fish, and the mean ratio of MeHg + compared to Σ Hg (MeHg +  + Hg 2+ ) was 94.0%. The results revealed statistically significant differences in concentrations of MeHg + and Hg 2+ , respectively, between sampling areas. Mean concentrations in the German Bight (North Sea), in Icelandic waters and in Mecklenburg Bight (Baltic Sea) were low (MeHg + : 0.023-0.036; Hg 2+ : 0.001-0.002 mg/kg wet weight), while concentrations in dab from the Dogger Bank, Firth of Forth and the vicinity of the Ekofisk oil field (all North Sea) were significantly higher (MeHg + : 0.059-0.101; Hg 2+ : 0.003-0.004 mg/kg wet weight). Statistical correlation analysis on effects of host-specific factors revealed that neither length, weight, age, sex nor condition factor showed a significant relationship with Hg concentrations. However, Hg concentrations were significantly correlated with the Fish Disease Index (FDI), indicating a relationship between Hg concentrations and the health status of dab. Multiple linear regression analysis aiming to find factors affecting Hg concentrations revealed that only the sampling area had a highly significant main effect on Hg concentrations, and in some cases, additionally the condition factor contributed significantly to the final model. From the results, it cannot be excluded that elevated Hg concentration recorded in dab were linked to discharges from

Crustal analysis of the Ulleung Basin in the East Sea (Japan Sea) from enhanced gravity mapping

NASA Astrophysics Data System (ADS)

Park, Chan Hong; Kim, Jeong Woo; Isezaki, Nobuhiro; Roman, Daniel R.; von Frese, Ralph R. B.

2006-12-01

To facilitate geological analyses of the Ulleung Basin in the East Sea (Japan Sea) between Korea and Japan, shipborne and satellite altimetry-derived gravity data are combined to derive a regionally coherent anomaly field. The 2-min gridded satellite altimetry-based gravity predicted by Sandwell and Smith [Sandwell DT, Smith WHF (1997) J Geophys Res 102(B5):10,039-10,054] are used for making cross-over adjustments that reduce the errors between track segments and at the cross-over points of shipborne gravity profiles. Relative to the regionally more homogeneous satellite gravity anomalies, the longer wavelength components of the shipborne anomalies are significantly improved with minimal distortion of their shorter wavelength components. The resulting free-air gravity anomaly map yields a more coherent integration of short and long wavelength anomalies compared to that obtained from either the shipborne or satellite data sets separately. The derived free-air anomalies range over about 140 mGals or more in amplitude and regionally correspond with bathymetric undulations in the Ulleung Basin. The gravity lows and highs along the basin’s margin indicate the transition from continental to oceanic crust. However, in the northeastern and central Ulleung Basin, the negative regional correlation between the central gravity high and bathymetric low suggests the presence of shallow denser mantle beneath thinned oceanic crust. A series of gravity highs mark seamounts or volcanic terranes from the Korean Plateau to Oki Island. Gravity modeling suggests underplating by mafic igneous rocks of the northwestern margin of the Ulleung Basin and the transition between continental and oceanic crust. The crust of the central Ulleung Basin is about a 14-15 km thick with a 4-5 km thick sediment cover. It may also include a relatively weakly developed buried fossil spreading ridge with approximately 2 km of relief.

Japan: Shikoku Island

Atmospheric Science Data Center

2016-08-24

... and island stations in the waters surrounding Japan and Korea. They characterized meteorological conditions, measured the atmospheric ... flew overhead. These MISR images, centered just north of Shikoku Island in southwest Japan, were acquired on April 13, 2001 ...

Wind extremes in the North Sea basin under climate change: an ensemble study of 12 CMIP5 GCMs

NASA Astrophysics Data System (ADS)

de Winter, R.; Ruessink, G.; Sterl, A.

2012-12-01

Coastal safety may be influenced by climate change, as changes in extreme surge levels and wave extremes may increase the vulnerability of dunes and other coastal defenses. In the North Sea, an area already prone to severe flooding, these high surge levels and waves are generated by severe wind speeds during storm events. As a result of the geometry of the North Sea, not only the maximum wind speed is relevant, but also wind direction. Analyzing changes in a changing climate implies that several uncertainties need to be taken into account. First, there is the uncertainty in climate experiments, which represents the possible development of the emission of greenhouse gases. Second, there is uncertainty between the climate models that are used to analyze the effect of different climate experiments. The third uncertainty is the natural variability of the climate. When this system variability is large, small trends will be difficult to detect. The natural variability results in statistical uncertainty, especially for events with high return values. We addressed the first two types of uncertainties for extreme wind conditions in the North Sea using 12 CMIP5 GCMs. To evaluate the differences between the climate experiments, two climate experiments (rcp4.5 and rcp8.5) from 2050-2100 are compared with historical runs, running from 1950-2000. Rcp4.5 is considered to be a middle climate experiment and rcp8.5 represents high-end climate scenarios. The projections of the 12 GCMs for a given scenario illustrate model uncertainty. We focus on the North Sea basin, because changes in wind conditions could have a large impact on safety of the densely populated North Sea coast, an area that has already a high exposure to flooding. Our results show that, consistent with ERA-Interim results, the annual maximum wind speed in the historical run demonstrates large interannual variability. For the North Sea, the annual maximum wind speed is not projected to change in either rcp4.5 or rcp8

Long-Term Trends in Calcifying Plankton and pH in the North Sea

PubMed Central

Beare, Doug; McQuatters-Gollop, Abigail; van der Hammen, Tessa; Machiels, Marcel; Teoh, Shwu Jiau; Hall-Spencer, Jason M.

2013-01-01

Relationships between six calcifying plankton groups and pH are explored in a highly biologically productive and data-rich area of the central North Sea using time-series datasets. The long-term trends show that abundances of foraminiferans, coccolithophores, and echinoderm larvae have risen over the last few decades while the abundances of bivalves and pteropods have declined. Despite good coverage of pH data for the study area there is uncertainty over the quality of this historical dataset; pH appears to have been declining since the mid 1990s but there was no statistical connection between the abundance of the calcifying plankton and the pH trends. If there are any effects of pH on calcifying plankton in the North Sea they appear to be masked by the combined effects of other climatic (e.g. temperature), chemical (nutrient concentrations) and biotic (predation) drivers. Certain calcified plankton have proliferated in the central North Sea, and are tolerant of changes in pH that have occurred since the 1950s but bivalve larvae and pteropods have declined. An improved monitoring programme is required as ocean acidification may be occurring at a rate that will exceed the environmental niches of numerous planktonic taxa, testing their capacities for acclimation and genetic adaptation. PMID:23658686

Eutrophication status of the North Sea, Skagerrak, Kattegat and the Baltic Sea in present and future climates: A model study

NASA Astrophysics Data System (ADS)

Skogen, Morten D.; Eilola, Kari; Hansen, Jørgen L. S.; Meier, H. E. Markus; Molchanov, Mikhail S.; Ryabchenko, Vladimir A.

2014-04-01

A method to combine observations and an ensemble of ecological models has been used to assess eutrophication. Using downscaled forcing from two GCMs under the A1B emission scenario, an assessment of the eutrophication status was made for a control (1970-2000) and a future climate (2070-2100) period. By using validation results from a hindcast to compute individual weights between the models, an assessment of eutrophication is done using a set of threshold values. The final classification distinguishes between three categories: problem area, potential problem area, and non-problem area, in accordance with current management practice as suggested by the Oslo and Paris Commissions (OSPAR) and the Helsinki Commission (HELCOM). For the control run the assessment indicates that the Kattegat, the Danish Straits, the Gulf of Finland, the Gotland Basin as well as main parts of the Arkona Basin, the Bornholm Basin, and the Baltic proper may be classified as problem areas. The main part of the North Sea and also the Skagerrak are non-problem areas while the main parts of the Gulf of Bothnia, Gulf of Riga and the entire southeastern continental coast of the North Sea may be classified as potential problem areas. In the future climate scenarios most of the previous potential problem areas in the Baltic Sea have become problem areas, except for the Bothnian Bay where the situation remain fairly unchanged. In the North Sea there seems to be no obvious changes in eutrophication status in the projected future climate.

Role of North Indian Ocean Air-Sea Interaction in Summer Monsoon Intraseasonal Oscillation

NASA Astrophysics Data System (ADS)

Zhang, L.; Han, W.; Li, Y.

2017-12-01

Air-sea coupling processes over the North Indian Ocean associated with Indian summer monsoon intraseasonal oscillation (MISO) are analyzed. Observations show that MISO convection anomalies affect underlying sea surface temperature (SST) through changes in surface shortwave radiation (via cloud cover change) and surface latent heat flux (associated with surface wind speed change). In turn, SST anomalies determine the changing rate of MISO precipitation (dP/dt): warm (cold) SST anomalies cause increasing (decreasing) precipitation rate through increasing (decreasing) surface convergence. Air-sea interaction gives rise to a quadrature relationship between MISO precipitation and SST anomalies. A local air-sea coupling model (LACM) is established based on these observed physical processes, which is a damped oscillatory system with no external forcing. The period of LACM is proportional to the square root of mean state mixed layer depth , assuming other physical parameters remain unchanged. Hence, LACM predicts a relatively short (long) MISO period over the North Indian Ocean during the May-June monsoon developing (July-August mature) phase when is shallow (deep). This result is consistent with observed MISO statistics. An oscillatory external forcing of a typical 30-day period is added to LACM, representing intraseasonal oscillations originated from the equatorial Indian Ocean and propagate into the North Indian Ocean. The period of LACM is then determined by both the inherent period associated with local air-sea coupling and the period of external forcing. It is found that resonance occurs when , amplifying the MISO in situ. This result explains the larger MISO amplitude during the monsoon developing phase compared to the mature phase, which is associated with seasonal cycle of . LACM, however, fails to predict the observed small MISO amplitude during the September-October monsoon decaying phase, when is also shallow. This deficiency might be associated with the

Rare earth elements in Japan Sea sediments and diagenetic behavior of Ce/Ce∗: Results from ODP Leg 127

NASA Astrophysics Data System (ADS)

Murray, Richard W.; Buchholtzten Brink, Marilyn R.; Brumsack, Hans J.; Gerlach, David C.; Russ, G. Price

1991-09-01

The relative effects of paleoceanographic and paleogeographic variations, sediment lithology, and diagenetic processes on the recorded rare earth element (REE) chemistry of Japan Sea sediments are evaluated by investigating REE total abundances and relative fractionations in 59 samples from Ocean Drilling Program Leg 127. REE total abundances (ΣREE) in the Japan Sea are strongly dependent upon the paleoceanographic position of a given site with respect to terrigenous and biogenic sources. REE concentrations at Site 794 (Yamato Basin) overall correspond well to aluminosilicate chemical indices and are strongly diluted by SiO2 within the late Miocene-Pliocene diatomaceous sequence. Eu/Eu∗ values at Site 794 reach a maximum through the diatomaceous interval as well, most likely suggesting an association of Eu/Eu∗ with the siliceous component, or reflecting slight incorporation of a detrital feldspar phase. ΣREE at Site 795 (Japan Basin) also is affiliated strongly with aluminosilicate phases, yet is diluted only slightly by siliceous input. At Site 797 (Yamato Basin), REE is not as clearly associated with the aluminosilicate fraction, is correlated moderately to siliceous input, and may be sporadically influenced by detrital heavy minerals originating from the nearby rifted continental fragment composing the Yamato Rise. The biogenic influence is largest at Site 794, moderately developed at Site 797, and of only minor importance at Site 795, reflecting basinal contrasts in productivity such that the Yamato Basin records greater biogenic input than the Japan Basin, while the most productive waters overlie the easternmost sequence of Site 794. Ce/Ce∗ profiles at all three sites increase monotonically with depth, and record progressive diagenetic LREE fractionation. The observed Ce/Ce∗ record does not respond to changes in oxygenation state of the overlying water, and Ce/Ce∗ correlates slightly better with depth than with age. The downhole increase in Ce

Coastal Sea Level along the North Eastern Atlantic Shelf from Delay Doppler Altimetry

NASA Astrophysics Data System (ADS)

Fenoglio-Marc, L.; Benveniste, J.; Andersen, O. B.; Gravelle, M.; Dinardo, S.; Uebbing, B.; Scharroo, R.; Kusche, J.; Kern, M.; Buchhaupt, C.

2017-12-01

Satellite altimetry data of the CryoSat-2 and Sentinel-3 missions processed with Delay Doppler methodology (DDA) provide improved coastal sea level measurements up to 2-4 km from coast, thanks to an along-track resolution of about 300m and a higher signal to noise ratio. We investigate the 10 Kilometre stripe along the North-Eastern Atlantic shelf from Lisbon to Bergen to detect the possible impacts in sea level change studies of this enhanced dataset. We consider SAR CryoSat-2 and Sentinel-3 altimetry products from the ESA GPOD processor and in-house reduced SAR altimetry (RDSAR) products. Improved processing includes in RDSAR the application of enhanced retrackers for the RDSAR waveform. Improved processing in SAR includes modification both in the generation of SAR waveforms, (as Hamming weighting window on the burst data prior to the azimuth FFT, zero-padding prior to the range FFT, doubling of the extension for the radar range swath) and in the SAMOSA2 retracker. Data cover the full lifetime of CryoSat-2 (6 years) and Sentinel-3 (1 year). Conventional altimetry are from the sea level CCI database. First we analyse the impact of these SAR altimeter data on the sea level trend and on the estimation of vertical motion from the altimeter minus tide gauge differences. VLM along the North-Eastern Atlantic shelf is generally small compared to the North-Western Atlantic Coast VLM, with a smaller signal to noise ratio. Second we investigate impact on the coastal mean sea level surface and the mean dynamic topography. We evaluate a mean surface from the new altimeter data to be combined to state of the art geoid models to derive the mean dynamic topography. We compare the results to existing oceanographic and geodetic mean dynamic topography solutions, both on grid and pointwise at the tide gauge stations. This study is supported by ESA through the Sea Level CCI and the GOCE++DYCOT projects

A new perspective on origin of the East Sea Intermediate Water: Observations of Argo floats

NASA Astrophysics Data System (ADS)

Park, JongJin; Lim, Byunghwan

2018-01-01

The East Sea Intermediate Water (ESIW), defined as the salinity minimum in the East Sea (hereafter ES) (Sea of Japan), is examined with respect to its overall characteristics and its low salinity origin using historical Argo float data from 1999 to 2015. Our findings suggest that the ESIW is formed in the western Japan Basin (40-42°N, 130-133°E), especially west of the North Korean front in North Korean waters, where strong negative surface wind stress curl resides in wintertime. The core ESIW near the formation site has temperatures of 3-4 °C and less than 33.98 psu salinity, warmer and fresher than that in the southern part of the ES. In order to trace the origin of the warmer and fresher water at the sea surface in winter, we analyzed the data in three different ways: (1) spatial distribution of surface water properties using monthly climatology from the Argo float data, (2) seasonal variation of heat and salt contents at the formation site, and (3) backtracking of surface drifter trajectories. Based on these analyses, it is likely that the warmer and fresher surface water properties found in the ESIW formation site are attributed to the low-salinity surface water advected from the southern part of the ES in autumn.

Seasonal and weekly variability of Atlantic inflow into the northern North Sea

NASA Astrophysics Data System (ADS)

Sheehan, Peter; Berx, Bee; Gallego, Alejandro; Hall, Rob; Heywood, Karen

2017-04-01

Quantifying the variability of Atlantic inflow is necessary for managing the North Sea ecosystem and for producing accurate models for forecasting, for example, oil spill trajectories. The JONSIS hydrographic section (2.23°W to 0° at 59.28°N) crosses the path of the main inflow of Atlantic water into the northwestern North Sea. 122 occupations between 1989 and 2015 are examined to determine the annual cycle of thermohaline-driven volume transport into the North Sea. Thermohaline transport is at a minimum (0.1 Sv) during winter when it is driven by a horizontal salinity gradient across a zonal bottom front; it is at a maximum (0.35 Sv) in early autumn when it is driven by a horizontal temperature gradient that develops across the same front. The amplitude of the annual cycle of temperature-driven transport (0.15 Sv) is bigger than the amplitude of the annual cycle of salinity-driven transport (0.025 Sv). The annual cycles are approximately six months out of phase. Our quantitative results are the first to be based on a long-term dataset, and we advance previous understanding by identifying a salinity-driven flow in winter. Week-to-week variability of the Atlantic inflow is examined from ten Seaglider occupations of the JONSIS section in October and November 2013. Tidal ellipses produced from glider dive-average current observations are in good agreement with ellipses produced from tide model predictions. Total transport is derived by referencing geostrophic shear to dive-average-current observations once the tidal component of the flow has been removed. Total transport through the section during the deployment (0.5-1 Sv) is bigger than the thermohaline component (0.1-0.2 Sv), suggesting non-thermohaline forcings (e.g. wind forcing) are important at that time of year. Thermohaline transport during the glider deployment is in agreement with the annual cycle derived from the long-term observations. The addition of the glider-derived barotropic current permits a more

Plastic ingestion by Scyliorhinus canicula trawl captured in the North Sea.

PubMed

Smith, L E

2018-05-01

The ingestion of plastic debris by marine organisms has been documented across a variety of taxa including; marine mammals, sea birds, sea turtles and some fish species. Fewer reports have described ingestion by sharks, in this study the gastrointestinal tracts of 20 small spotted catsharks (Scyliorhinus canicula) trawl captured in the North Sea were investigated. Macroplastics (>20 mm) were found in 2 individuals and microplastic (<5 mm) was found in one other individual, this is the first time that plastic ingestion has been reported in this species. These observations suggest that gastrointestinal analysis of commonly landed elasmobranch species is worthwhile, to further understanding on the organisms and habitats impacted by plastic pollution. Copyright © 2018 Elsevier Ltd. All rights reserved.

Closing the Gaps in Offshore P&A: Lessons Learned From the North Sea

NASA Astrophysics Data System (ADS)

Torsater, M.

2017-12-01

This talk will give an overview of the major challenges related to offshore well plugging and abandonment (P&A) with examples from the North Sea. The talk will outline why today's P&A operations are so time consuming and expensive, and it will point out current technology gaps and issues related to standards and regulations in the North Sea countries. Emerging P&A solutions will be discussed, and results from large ongoing research projects in Norway will be shared. Special emphasis will be given to promising new concepts, such as using creeping shale formations as permanent well barriers, and using thermal methods for removal of tubing and casing. The long-term aspects of well plugging will also be discussed, together with methods available for minimizing leakage risk.

Shallow Gas Migration along Hydrocarbon Wells-An Unconsidered, Anthropogenic Source of Biogenic Methane in the North Sea.

PubMed

Vielstädte, Lisa; Haeckel, Matthias; Karstens, Jens; Linke, Peter; Schmidt, Mark; Steinle, Lea; Wallmann, Klaus

2017-09-05

Shallow gas migration along hydrocarbon wells constitutes a potential methane emission pathway that currently is not recognized in any regulatory framework or greenhouse gas inventory. Recently, the first methane emission measurements at three abandoned offshore wells in the Central North Sea (CNS) were conducted showing that considerable amounts of biogenic methane originating from shallow gas accumulations in the overburden of deep reservoirs were released by the boreholes. Here, we identify numerous wells poking through shallow gas pockets in 3-D seismic data of the CNS indicating that about one-third of the wells may leak, potentially releasing a total of 3-17 kt of methane per year into the North Sea. This poses a significant contribution to the North Sea methane budget. A large fraction of this gas (∼42%) may reach the atmosphere via direct bubble transport (0-2 kt yr -1 ) and via diffusive exchange of methane dissolving in the surface mixed layer (1-5 kt yr -1 ), as indicated by numerical modeling. In the North Sea and in other hydrocarbon-prolific provinces of the world shallow gas pockets are frequently observed in the sedimentary overburden and aggregate leakages along the numerous wells drilled in those areas may be significant.

Occurrence of Ergasilus megaceros Wilson, 1916, in the sea lamprey and other fishes from North America

USGS Publications Warehouse

Muzzall, Patrick M.; Hudson, Patrick L.

2004-01-01

Ergasilus megaceros (Copepoda: Ergasilidae) was recovered from the nasal fossae (lamellae) of the olfactory sac in 1 (1.8%) of 56 sea lampreys, Petromyzon marinus Linne, 1758, collected in May 2002 from the Cheboygan River, Michigan. Although the sea lamprey is a new host record for E. megaceros, this fish species may not be a preferred host because of its low prevalence. Ergasilus megaceros is the second ergasilid species reported from the sea lamprey in North America. This is the third report of an ergasilid species infecting the nasal fossae of fishes in North America, with E. rhinos being the only other species reported from this site.

Last 900 ka river longprofile changes controlled by Yoro fault activity and glacial sea-level changes, Nobi plain, central Japan

NASA Astrophysics Data System (ADS)

Sugai, T.; Sato, T.

2015-12-01

This paper compared grain size, thickness, and lithological character of ten fluvial gravel layers formed during the glacial sea-level lowstands intervening inner bay mud layers deposited during the interglacial marine transgressional periods since the last 900 ka by integrated analyses of sediment cores including 600 m deep onein the Nobi plain, central Japan. Linkages between river long profile changes and sea-level and climate changes will be discussed. The Nobi basin is one of the representative delta type alluvial lowlands in Japan dominated by longitudinal drainage system named Kiso river system flowing southward from central Japan Alps with abundant water and sediment discharges. The basin bounded by the Yoro fault on the west has been tilted westward by the repetitive faulting activity. The basin stratigraphy and its stacking patterns suggest uniform and rapid subsidence and tilting rates of the basin with the maximum value of 1 mm yr-1 and 10-4 kyr-1 respectively produced by the Yoro fault activity under the W-E compressional regional stress field during the middle and late Quaternary periods. Tephrochronological, paleomagnetic, geochemical, and diatom analyses enabled to identify ten times repeated marine transgression-regression sequences correlated with full glacial-interglacial sea-level changes during the last 900 ka. All of the ten sequence boundaries were characterized by fluvial gravel layers were formed by the Kiso river system. The mean maximum gravel size is proportional to the magnitude of sea level lowering inferred from MIS curve, i.e. gravels deposited in MIS 12 and 16 are the largest, and those in MIS 14 and 8 are the smallest since MIS 16. This suggests that the longitudinal profile of the Kiso river system has been adjusting to the sea level changes and that the steeper longitudinal profile formed in the lower sea level periods can transport larger gravels to the drilling sites. In fact the present river bed gravel size is in proportion

Magnitude and location of historical earthquakes in Japan and implications for the 1855 Ansei Edo earthquake

USGS Publications Warehouse

Bakun, W.H.

2005-01-01

Japan Meteorological Agency (JMA) intensity assignments IJMA are used to derive intensity attenuation models suitable for estimating the location and an intensity magnitude Mjma for historical earthquakes in Japan. The intensity for shallow crustal earthquakes on Honshu is equal to -1.89 + 1.42MJMA - 0.00887?? h - 1.66log??h, where MJMA is the JMA magnitude, ??h = (??2 + h2)1/2, and ?? and h are epicentral distance and focal depth (km), respectively. Four earthquakes located near the Japan Trench were used to develop a subducting plate intensity attenuation model where intensity is equal to -8.33 + 2.19MJMA -0.00550??h - 1.14 log ?? h. The IJMA assignments for the MJMA7.9 great 1923 Kanto earthquake on the Philippine Sea-Eurasian plate interface are consistent with the subducting plate model; Using the subducting plate model and 226 IJMA IV-VI assignments, the location of the intensity center is 25 km north of the epicenter, Mjma is 7.7, and MJMA is 7.3-8.0 at the 1?? confidence level. Intensity assignments and reported aftershock activity for the enigmatic 11 November 1855 Ansei Edo earthquake are consistent with an MJMA 7.2 Philippine Sea-Eurasian interplate source or Philippine Sea intraslab source at about 30 km depth. If the 1855 earthquake was a Philippine Sea-Eurasian interplate event, the intensity center was adjacent to and downdip of the rupture area of the great 1923 Kanto earthquake, suggesting that the 1855 and 1923 events ruptured adjoining sections of the Philippine Sea-Eurasian plate interface.

Fate of microplastics and mesoplastics carried by surface currents and wind waves: A numerical model approach in the Sea of Japan.

PubMed

Iwasaki, Shinsuke; Isobe, Atsuhiko; Kako, Shin'ichiro; Uchida, Keiichi; Tokai, Tadashi

2017-08-15

A numerical model was established to reproduce the oceanic transport processes of microplastics and mesoplastics in the Sea of Japan. A particle tracking model, where surface ocean currents were given by a combination of a reanalysis ocean current product and Stokes drift computed separately by a wave model, simulated particle movement. The model results corresponded with the field survey. Modeled results indicated the micro- and mesoplastics are moved northeastward by the Tsushima Current. Subsequently, Stokes drift selectively moves mesoplastics during winter toward the Japanese coast, resulting in increased contributions of mesoplastics south of 39°N. Additionally, Stokes drift also transports micro- and mesoplastics out to the sea area south of the subpolar front where the northeastward Tsushima Current carries them into the open ocean via the Tsugaru and Soya straits. Average transit time of modeled particles in the Sea of Japan is drastically reduced when including Stokes drift in the model. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Neutral poly- and perfluoroalkyl substances in air and seawater of the North Sea.

PubMed

Xie, Zhiyong; Zhao, Zhen; Möller, Axel; Wolschke, Hendrik; Ahrens, Lutz; Sturm, Renate; Ebinghaus, Ralf

2013-11-01

Concentrations of neutral poly- and perfluoroalkyl substances (PFASs), such as fluorotelomer alcohols (FTOHs), perfluoroalkane sulfonamides (FASAs), perfluoroalkane sufonamidoethanols (FASEs), and fluorotelomer acrylates (FTACs), have been simultaneously determined in surface seawater and the atmosphere of the North Sea. Seawater and air samples were taken aboard the German research vessel Heincke on the cruise 303 from 15 to 24 May 2009. The concentrations of FTOHs, FASAs, FASEs, and FTACs in the dissolved phase were 2.6-74, <0.1-19, <0.1-63, and <1.0-9.0 pg L(-1), respectively. The highest concentrations were determined in the estuary of the Weser and Elbe rivers and a decreasing concentration profile appeared with increasing distance from the coast toward the central part of the North Sea. Gaseous FTOHs, FASAs, FASEs, and FTACs were in the range of 36-126, 3.1-26, 3.7-19, and 0.8-5.6 pg m(-3), which were consistent with the concentrations determined in 2007 in the North Sea, and approximately five times lower than those reported for an urban area of Northern Germany. These results suggested continuous continental emissions of neutral PFASs followed by transport toward the marine environment. Air-seawater gas exchanges of neutral PFASs were estimated using fugacity ratios and the two-film resistance model based upon paired air-seawater concentrations and estimated Henry's law constant values. Volatilization dominated for all neutral PFASs in the North Sea. The air-seawater gas exchange fluxes were in the range of 2.5×10(3)-3.6×10(5) pg m(-2) for FTOHs, 1.8×10(2)-1.0×10(5) pg m(-2) for FASAs, 1.1×10(2)-3.0×10(5) pg m(-2) for FASEs and 6.3×10(2)-2.0×10(4) pg m(-2) for FTACs, respectively. These results suggest that the air-seawater gas exchange is an important process that intervenes in the transport and fate for neutral PFASs in the marine environment.

Topography of the 410 km and 660 km discontinuities beneath the Japan Sea and adjacent regions by analysis of multiple-ScS waves

NASA Astrophysics Data System (ADS)

Wang, Xin; Li, Juan; Chen, Qi-Fu

2017-02-01

The northwest Pacific subduction region is an ideal location to study the interaction between the subducting slab and upper mantle discontinuities. Due to the sparse distribution of seismic stations in the sea, previous studies mostly focus on mantle transition zone (MTZ) structures beneath continents or island arcs, leaving the vast area of the Japan Sea and Okhotsk Sea untouched. In this study, we analyzed multiple-ScS reverberation waves, and a common-reflection-point stacking technique was applied to enhance consistent signals beneath reflection points. A topographic image of the 410 km and 660 km discontinuities is obtained beneath the Japan Sea and adjacent regions. One-dimensional and 3-D velocity models are adapted to obtain the "apparent" and "true" depth. We observe a systematic pattern of depression ( 10-20 km) and elevation ( 5-10 km) of the 660, with the topography being roughly consistent with the shift of the olivine-phase transition boundary caused by the subducting Pacific plate. The behavior of the 410 is more complex. It is generally 5-15 km shallower at the location where the slab penetrates and deepened by 5-10 km oceanward of the slab where a low-velocity anomaly is observed in tomography images. Moreover, we observe a wide distribution of depressed 410 beneath the southern Okhotsk Sea and western Japan Sea. The hydrous wadsleyite boundary caused by the high water content at the top of the MTZ could explain the depression. The long-history trench rollback motion of Pacific slab might be responsible for the widely distributed depression of the 410 ranging upward and landward from the slab.

The Bonn Agreement Aerial Surveillance programme: trends in North Sea oil pollution 1986-2004.

PubMed

Carpenter, Angela

2007-02-01

This paper examines the use of aerial surveillance activities conducted in the North Sea region of Europe since 1986 to assess trends in levels of oil inputs into the marine environment, both across the whole region and within the waters of the different coastal states. It makes use of data collected under the aegis of the 1969 Bonn Agreement through its Annual Reports on Aerial Surveillance and examines developments in surveillance methods and technology which have led to improvements in the detection of oil spills, even during the hours of darkness. The paper then examines country specific data for the eight North Sea contracting parties to the Agreement to assess trends in oil spills in the region.

Forecasting petroleum discoveries in sparsely drilled areas: Nigeria and the North Sea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Attanasi, E.D.; Root, D.H.

1988-10-01

Decline function methods for projecting future discoveries generally capture the crowding effects of wildcat wells on the discovery rate. However, these methods do not accommodate easily situations where exploration areas and horizons are expanding. In this paper, a method is presented that uses a mapping algorithm for separating these often countervailing influences. The method is applied to Nigeria and the North Sea. For an amount of future drilling equivalent to past drilling (825 wildcat wells), future discoveries (in resources found) for Nigeria are expected to decline by 68% per well but still amount to 8.5 billion barrels of oil equivalentmore » (BOE). Similarly, for the total North Sea for an equivalent amount and mix among areas of past drilling (1322 wildcat wells), future discoveries are expected to amount to 17.9 billion BOE, whereas the average discovery rate per well is expected to decline by 71%.« less

Seasonal and longitudinal distributions of atmospheric water-soluble dicarboxylic acids, oxocarboxylic acids, and α-dicarbonyls over the North Pacific

NASA Astrophysics Data System (ADS)

Bikkina, Srinivas; Kawamura, Kimitaka; Imanishi, Katsuya; Boreddy, S. K. R.; Nojiri, Yukihiro

2015-05-01

In order to assess the seasonal variability of atmospheric abundances of dicarboxylic acids, oxocarboxylic acids, and α-dicarbonyls over the North Pacific and Sea of Japan, aerosol samples were collected along the longitudinal transacts during six cruises between Canada and Japan. The back trajectory analyses indicate that aerosol samples collected in winter and spring are influenced by the East Asian outflow, whereas summer and fall samples are associated with the pristine maritime air masses. Molecular distributions of water-soluble organics in winter and spring samples show the predominance of oxalic acid (C2) followed by succinic (C4) and malonic acids (C3). In contrast, summer and fall marine aerosols are characterized by the predominance of C3 over C4. Concentrations of dicarboxylic acids were higher over the Sea of Japan than the North Pacific. With a lack of continental outflow, higher concentrations during early summer are ascribed to atmospheric oxidation of organic precursors associated with high biological activity in the North Pacific. This interpretation is further supported by the high abundances of azelaic acid, which is a photochemical oxidation product of biogenic unsaturated fatty acids, over the Bering Sea in early summer when surface waters are characterized by high biological productivity. We found higher ratios of oxalic acid to pyruvic and glyoxylic acids (C2/Pyr and C2/ωC2) and glyoxal and methylglyoxal (C2/Gly and C2/MeGly) in summer and fall than in winter and spring, suggesting a production of C2 from the aqueous-phase oxidation of oceanic isoprene. In this study, dicarboxylic acids account for 0.7-38% of water-soluble organic carbon.

Mapping the North Sea base-Quaternary: using 3D seismic to fill a gap in the geological record

NASA Astrophysics Data System (ADS)

Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

2014-05-01

The identification and mapping of the base-Quaternary boundary in the central parts of the North Sea is problematic due to the change from an unconformable transition between Pliocene and Pleistocene deltaic deposits in the southern North Sea to a conformable one further north (Sejrup et al 1991; Gatliff et al 1994). The best estimates of the transition use seismic reflection data to identify a 'crenulated reflector' (Buckley 2012), or rely on correlating sparse biostratigraphy (Cameron et al 1987). Recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) allows greater confidence in the correlation to a regional 3D seismic dataset and show that the base-Quaternary can be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The mapped horizon is presented here alongside the difference between this new interpretation and the previously interpreted base-Quaternary (Buckley 2012). The revised base-Quaternary surface reaches a depth of 1248 ms TWT or approximately 1120 m (assuming average velocity of 1800 m/s) showing an elongate basin shape that follows the underlying structure of the Central Graben. The difference between the revised base-Quaternary and the traditional base-Quaternary reaches a maximum of over 600 ms TWT or approximately 540 m in the south-west with over 300 ms TWT or approximately 270 m at the Josephine well (56° 36.11'N, 2° 27.09'E) in the centre of the basin. Mapping this new base-Quaternary allows for the interpretation of the paleo-envionrment during the earliest Quaternary. Seismic attribute analysis indicates a deep water basin with sediment deposition from multiple deltas and redistribution by deep

Interannual SST Variability in the Japan/East Sea and Relationship with Environmental Variables

DTIC Science & Technology

2006-01-01

Soya Strait (SS), and Tartar Strait (TTS). (b) Regional geography. Interannual SST Variability in the Japan/East Sea 117 200 interruptions due to...caused by differential seasonal forcing. During the summer strong solar radiation penetrates into the entire Longitude(oE) La tit ud e( o N ) 50 50 100...1988.6 1988.8 1989 1989.2 1989.4 1989.6 1989.8 1990 1990.2 -3 -2 -1 0 1 2 3 Time(year) Te m pe ra tu re (o C ) Longitude(oE) La tit ud e( o N ) (a) 5

A multi-decadal wind-wave hindcast for the North Sea 1949-2014: coastDat2

NASA Astrophysics Data System (ADS)

Groll, Nikolaus; Weisse, Ralf

2017-12-01

Long and consistent wave data are important for analysing wave climate variability and change. Moreover, such wave data are also needed in coastal and offshore design and for addressing safety-related issues at sea. Using the third-generation spectral wave model WAM a multi-decadal wind-wave hindcast for the North Sea covering the period 1949-2014 was produced. The hindcast is part of the coastDat database representing a consistent and homogeneous met-ocean data set. It is shown that despite not being perfect, data from the wave hindcast are generally suitable for wave climate analysis. In particular, comparisons of hindcast data with in situ and satellite observations show on average a reasonable agreement, while a tendency towards overestimation of the highest waves could be inferred. Despite these limitations, the wave hindcast still provides useful data for assessing wave climate variability and change as well as for risk analysis, in particular when conservative estimates are needed. Hindcast data are stored at the World Data Center for Climate (WDCC) and can be freely accessed using the North_Sea" target="_blank">doi:10.1594/WDCC/coastDat-2_WAM-North_Sea Groll and Weisse(2016) or via the coastDat web-page http://www.coastdat.de.

Towards uncertainty estimation for operational forecast products - a multi-model-ensemble approach for the North Sea and the Baltic Sea

NASA Astrophysics Data System (ADS)

Golbeck, Inga; Li, Xin; Janssen, Frank

2014-05-01

Several independent operational ocean models provide forecasts of the ocean state (e.g. sea level, temperature, salinity and ice cover) in the North Sea and the Baltic Sea on a daily basis. These forecasts are the primary source of information for a variety of information and emergency response systems used e.g. to issue sea level warnings or carry out oil drift forecast. The forecasts are of course highly valuable as such, but often suffer from a lack of information on their uncertainty. With the aim of augmenting the existing operational ocean forecasts in the North Sea and the Baltic Sea by a measure of uncertainty a multi-model-ensemble (MME) system for sea surface temperature (SST), sea surface salinity (SSS) and water transports has been set up in the framework of the MyOcean-2 project. Members of MyOcean-2, the NOOS² and HIROMB/BOOS³ communities provide 48h-forecasts serving as inputs. Different variables are processed separately due to their different physical characteristics. Based on the so far collected daily MME products of SST and SSS, a statistical method, Empirical Orthogonal Function (EOF) analysis is applied to assess their spatial and temporal variability. For sea surface currents, progressive vector diagrams at specific points are consulted to estimate the performance of the circulation models especially in hydrodynamic important areas, e.g. inflow/outflow of the Baltic Sea, Norwegian trench and English Channel. For further versions of the MME system, it is planned to extend the MME to other variables like e.g. sea level, ocean currents or ice cover based on the needs of the model providers and their customers. It is also planned to include in-situ data to augment the uncertainty information and for validation purposes. Additionally, weighting methods will be implemented into the MME system to develop more complex uncertainty measures. The methodology used to create the MME will be outlined and different ensemble products will be presented. In

A cautionary tale: A study of a methane enhancement over the North Sea

NASA Astrophysics Data System (ADS)

Cain, M.; Warwick, N. J.; Fisher, R. E.; Lowry, D.; Lanoisellé, M.; Nisbet, E. G.; France, J.; Pitt, J.; O'Shea, S.; Bower, K. N.; Allen, G.; Illingworth, S.; Manning, A. J.; Bauguitte, S.; Pisso, I.; Pyle, J. A.

2017-07-01

Airborne measurements of a methane (CH4) plume over the North Sea from August 2013 are analyzed. The plume was only observed downwind of circumnavigated gas fields, and three methods are used to determine its source. First, a mass balance calculation assuming a gas field source gives a CH4 emission rate between 2.5 ± 0.8×104 and 4.6 ± 1.5×104 kg h-1. This would be greater than the industry's reported 0.5% leak rate if it were emitting for more than half the time. Second, annual average UK CH4 emissions are combined with an atmospheric dispersion model to create pseudo-observations. Clean air from the North Atlantic passed over mainland UK, picking up anthropogenic emissions. To best explain the observed plume using pseudo-observations, an additional North Sea source from the gas rigs area is added. Third, the δ13C-CH4 from the plume is shown to be -53‰, which is lighter than fossil gas but heavier than the UK average emission. We conclude that either an additional small-area mainland source is needed, combined with temporal variability in emission or transport in small-scale meteorological features. Alternatively, a combination of additional sources that are at least 75% from the mainland (-58‰) and up to 25% from the North Sea gas rigs area (-32‰) would explain the measurements. Had the isotopic analysis not been performed, the likely conclusion would have been of a gas field source of CH4. This demonstrates the limitation of analyzing mole fractions alone, as the simplest explanation is rejected based on analysis of isotopic data.

Korea and the Yellow Sea

NASA Image and Video Library

2017-12-08

NASA image acquired September 24, 2012 City lights at night are a fairly reliable indicator of where people live. But this isn’t always the case, and the Korean Peninsula shows why. As of July 2012, South Korea’s population was estimated at roughly 49 million people, and North Korea’s population was estimated at about half that number. But where South Korea is gleaming with city lights, North Korea has hardly any lights at all—just a faint glimmer around Pyongyang. On September 24, 2012, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this nighttime view of the Korean Peninsula. This imagery is from the VIIRS “day-night band,” which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe signals such as gas flares, auroras, wildfires, city lights, and reflected moonlight. The wide-area image shows the Korean Peninsula, parts of China and Japan, the Yellow Sea, and the Sea of Japan. The white inset box encloses an area showing ship lights in the Yellow Sea. Many of the ships form a line, as if assembling along a watery border. Following the 1953 armistice ending the Korean War, per-capita income in South Korea rose to about 17 times the per-capital income level of North Korea, according to the U.S. Central Intelligence Agency. Worldwide, South Korea ranks 12th in electricity production, and 10th in electricity consumption, per 2011 estimates. North Korea ranks 71st in electricity production, and 73rd in electricity consumption, per 2009 estimates. NASA Earth Observatory image by Jesse Allen and Robert Simmon, using VIIRS Day-Night Band data from the Suomi National Polar-orbiting Partnership. Suomi NPP is the result of a partnership between NASA, the National Oceanic and Atmospheric Administration, and the Department of Defense. Caption by Michon Scott. Instrument: Suomi NPP - VIIRS Credit: NASA Earth Observatory Click here to view all of the Earth at Night 2012

Studying internal and external magnetic fields in Japan using MAGSAT data

NASA Technical Reports Server (NTRS)

Fukushima, N. (Principal Investigator); Maeda, H.; Yukutake, T.; Tanaka, M.; Oshima, S.; Ogawa, K.; Kawamura, M.; Miyazaki, Y.; Uyeda, S.; Kobayashi, K.

1980-01-01

Examination of the total intensity data of CHRONIT on a few paths over Japan and its neighboring sea shows MAGSAT is extremely useful for studying the local magnetic anomaly. In high latitudes, the signatures of field aligned currents are clearly recognized. These include (1) the persistent basic pattern of current flow; (2) the more intense currents in the summer hemisphere than in the winter hemisphere; (3) more fluctuations in current intensities in summer dawn hours; and (4) apparent dawn-dusk asymmetry in the field-aligned current intensity between the north and south polar regions.

Evaluation of harvest and information needs for North American sea ducks

USGS Publications Warehouse

Koneff, Mark D.; Zimmerman, Guthrie S.; Dwyer, Chris P.; Fleming, Kathleen K.; Padding, Paul I.; Devers, Patrick K.; Johnson, Fred A.; Runge, Michael C.; Roberts, Anthony J.

2017-01-01

Wildlife managers routinely seek to establish sustainable limits of sport harvest or other regulated forms of take while confronted with considerable uncertainty. A growing body of ecological research focuses on methods to describe and account for uncertainty in management decision-making and to prioritize research and monitoring investments to reduce the most influential uncertainties. We used simulation methods incorporating measures of demographic uncertainty to evaluate risk of overharvest and prioritize information needs for North American sea ducks (Tribe Mergini). Sea ducks are popular game birds in North America, yet they are poorly monitored and their population dynamics are poorly understood relative to other North American waterfowl. There have been few attempts to assess the sustainability of harvest of North American sea ducks, and no formal harvest strategy exists in the U.S. or Canada to guide management. The popularity of sea duck hunting, extended hunting opportunity for some populations (i.e., special seasons and/or bag limits), and population declines have led to concern about potential overharvest. We used Monte Carlo simulation to contrast estimates of allowable harvest and observed harvest and assess risk of overharvest for 7 populations of North American sea ducks: the American subspecies of common eider (Somateria mollissima dresseri), eastern and western populations of black scoter (Melanitta americana) and surf scoter (M. perspicillata), and continental populations of white-winged scoter (M. fusca) and long-tailed duck (Clangula hyemalis). We combined information from empirical studies and the opinions of experts through formal elicitation to create probability distributions reflecting uncertainty in the individual demographic parameters used in this assessment. Estimates of maximum growth (rmax), and therefore of allowable harvest, were highly uncertain for all populations. Long-tailed duck and American common eider appeared to be at high

Evaluation of harvest and information needs for North American sea ducks.

PubMed

Koneff, Mark D; Zimmerman, Guthrie S; Dwyer, Chris P; Fleming, Kathleen K; Padding, Paul I; Devers, Patrick K; Johnson, Fred A; Runge, Michael C; Roberts, Anthony J

2017-01-01

Wildlife managers routinely seek to establish sustainable limits of sport harvest or other regulated forms of take while confronted with considerable uncertainty. A growing body of ecological research focuses on methods to describe and account for uncertainty in management decision-making and to prioritize research and monitoring investments to reduce the most influential uncertainties. We used simulation methods incorporating measures of demographic uncertainty to evaluate risk of overharvest and prioritize information needs for North American sea ducks (Tribe Mergini). Sea ducks are popular game birds in North America, yet they are poorly monitored and their population dynamics are poorly understood relative to other North American waterfowl. There have been few attempts to assess the sustainability of harvest of North American sea ducks, and no formal harvest strategy exists in the U.S. or Canada to guide management. The popularity of sea duck hunting, extended hunting opportunity for some populations (i.e., special seasons and/or bag limits), and population declines have led to concern about potential overharvest. We used Monte Carlo simulation to contrast estimates of allowable harvest and observed harvest and assess risk of overharvest for 7 populations of North American sea ducks: the American subspecies of common eider (Somateria mollissima dresseri), eastern and western populations of black scoter (Melanitta americana) and surf scoter (M. perspicillata), and continental populations of white-winged scoter (M. fusca) and long-tailed duck (Clangula hyemalis). We combined information from empirical studies and the opinions of experts through formal elicitation to create probability distributions reflecting uncertainty in the individual demographic parameters used in this assessment. Estimates of maximum growth (rmax), and therefore of allowable harvest, were highly uncertain for all populations. Long-tailed duck and American common eider appeared to be at high

Evaluation of harvest and information needs for North American sea ducks

PubMed Central

Dwyer, Chris P.; Fleming, Kathleen K.; Padding, Paul I.; Devers, Patrick K.; Johnson, Fred A.; Runge, Michael C.; Roberts, Anthony J.

2017-01-01

Wildlife managers routinely seek to establish sustainable limits of sport harvest or other regulated forms of take while confronted with considerable uncertainty. A growing body of ecological research focuses on methods to describe and account for uncertainty in management decision-making and to prioritize research and monitoring investments to reduce the most influential uncertainties. We used simulation methods incorporating measures of demographic uncertainty to evaluate risk of overharvest and prioritize information needs for North American sea ducks (Tribe Mergini). Sea ducks are popular game birds in North America, yet they are poorly monitored and their population dynamics are poorly understood relative to other North American waterfowl. There have been few attempts to assess the sustainability of harvest of North American sea ducks, and no formal harvest strategy exists in the U.S. or Canada to guide management. The popularity of sea duck hunting, extended hunting opportunity for some populations (i.e., special seasons and/or bag limits), and population declines have led to concern about potential overharvest. We used Monte Carlo simulation to contrast estimates of allowable harvest and observed harvest and assess risk of overharvest for 7 populations of North American sea ducks: the American subspecies of common eider (Somateria mollissima dresseri), eastern and western populations of black scoter (Melanitta americana) and surf scoter (M. perspicillata), and continental populations of white-winged scoter (M. fusca) and long-tailed duck (Clangula hyemalis). We combined information from empirical studies and the opinions of experts through formal elicitation to create probability distributions reflecting uncertainty in the individual demographic parameters used in this assessment. Estimates of maximum growth (rmax), and therefore of allowable harvest, were highly uncertain for all populations. Long-tailed duck and American common eider appeared to be at high

Identifying active foraminifera in the Sea of Japan using metatranscriptomic approach

NASA Astrophysics Data System (ADS)

Lejzerowicz, Franck; Voltsky, Ivan; Pawlowski, Jan

2013-02-01

Metagenetics represents an efficient and rapid tool to describe environmental diversity patterns of microbial eukaryotes based on ribosomal DNA sequences. However, the results of metagenetic studies are often biased by the presence of extracellular DNA molecules that are persistent in the environment, especially in deep-sea sediment. As an alternative, short-lived RNA molecules constitute a good proxy for the detection of active species. Here, we used a metatranscriptomic approach based on RNA-derived (cDNA) sequences to study the diversity of the deep-sea benthic foraminifera and compared it to the metagenetic approach. We analyzed 257 ribosomal DNA and cDNA sequences obtained from seven sediments samples collected in the Sea of Japan at depths ranging from 486 to 3665 m. The DNA and RNA-based approaches gave a similar view of the taxonomic composition of foraminiferal assemblage, but differed in some important points. First, the cDNA dataset was dominated by sequences of rotaliids and robertiniids, suggesting that these calcareous species, some of which have been observed in Rose Bengal stained samples, are the most active component of foraminiferal community. Second, the richness of monothalamous (single-chambered) foraminifera was particularly high in DNA extracts from the deepest samples, confirming that this group of foraminifera is abundant but not necessarily very active in the deep-sea sediments. Finally, the high divergence of undetermined sequences in cDNA dataset indicate the limits of our database and lack of knowledge about some active but possibly rare species. Our study demonstrates the capability of the metatranscriptomic approach to detect active foraminiferal species and prompt its use in future high-throughput sequencing-based environmental surveys.

Extreme storm surge modelling in the North Sea. The role of the sea state, forcing frequency and spatial forcing resolution

NASA Astrophysics Data System (ADS)

Ridder, Nina; de Vries, Hylke; Drijfhout, Sybren; van den Brink, Henk; van Meijgaard, Erik; de Vries, Hans

2018-02-01

This study shows that storm surge model performance in the North Sea is mostly unaffected by the application of temporal variations of surface drag due to changes in sea state provided the choice of a suitable constant Charnock parameter in the sea-state-independent case. Including essential meteorological features on smaller scales and minimising interpolation errors by increasing forcing data resolution are shown to be more important for the improvement of model performance particularly at the high tail of the probability distribution. This is found in a modelling study using WAQUA/DCSMv5 by evaluating the influence of a realistic air-sea momentum transfer parameterization and comparing it to the influence of changes in the spatial and temporal resolution of the applied forcing fields in an effort to support the improvement of impact and climate analysis studies. Particular attention is given to the representation of extreme water levels over the past decades based on the example of the Netherlands. For this, WAQUA/DCSMv5 is forced with ERA-Interim reanalysis data. Model results are obtained from a set of different forcing fields, which either (i) include a wave-state-dependent Charnock parameter or (ii) apply a constant Charnock parameter ( α C h = 0.032) tuned for young sea states in the North Sea, but differ in their spatial and/or temporal resolution. Increasing forcing field resolution from roughly 79 to 12 km through dynamically downscaling can reduce the modelled low bias, depending on coastal station, by up to 0.25 m for the modelled extreme water levels with a 1-year return period and between 0.1 m and 0.5 m for extreme surge heights.

Influence of Sea Ice on the Thermohaline Circulation in the Arctic-North Atlantic Ocean

NASA Technical Reports Server (NTRS)

Mauritzen, Cecilie; Haekkinen, Sirpa

1997-01-01

A fully prognostic coupled ocean-ice model is used to study the sensitivity of the overturning cell of the Arctic-North-Atlantic system to sea ice forcing. The strength of the thermohaline cell will be shown to depend on the amount of sea ice transported from the Arctic to the Greenland Sea and further to the subpolar gyre. The model produces a 2-3 Sv increase of the meridional circulation cell at 25N (at the simulation year 15) corresponding to a decrease of 800 cu km in the sea ice export from the Arctic. Previous modeling studies suggest that interannual and decadal variability in sea ice export of this magnitude is realistic, implying that sea ice induced variability in the overturning cell can reach 5-6 Sv from peak to peak.

Monitoring of oil hydrocarbons pollution in the Sea of Japan, based on detection of marker genes in microbial communities

NASA Astrophysics Data System (ADS)

Kim, A. V.; Buzoleva, L. S.; Bogatyrenko, E. A.; Zemskaya, T. I.; Mamaeva, E. V.

2018-01-01

By means of molecular biology techniques, metabolic potential of microbial communities within the regions of inshore water areas in the Sea of Japan with various anthropogenic load was explored. Presence of functional genes, responsible for oil hydrocarbons destruction, for microbial communities within the regions of inshore water areas in the Sea of Japan was first researched. In total microbial DNA from water mass in the regions with chronic anthropogenic pollution, the genes, responsible for oxidation of broad range of n-alkanes and polycyclic aromatic hydrocarbons, were found. Detection of marker genes in the background water area (in the Vostok Bay) was ever indicating ecological deterioration within this territory. Thereby, it was demonstrated, that molecular genetic methods, aimed at marker gene detection in total bacterial DNA from environment objects, proved themselves to be more effective technique for identification of oil hydrocarbons water pollution, in comparison with trivial culturable methods.

Analysis of tidal currents in the North Sea from shipboard acoustic Doppler current profiler data

NASA Astrophysics Data System (ADS)

Vindenes, Håvard; Orvik, Kjell Arild; Søiland, Henrik; Wehde, Henning

2018-06-01

North Sea tidal currents are determined by applying harmonic analysis to ship-borne acoustic Doppler current profiler data recorded from 1999 to 2016, covering large areas of the northern North Sea. Direct current measurement data sets of this magnitude are rare in the otherwise well investigated North Sea, and thus it is a valuable asset in studying and expanding our understanding of its tidal currents and circulation in general. The harmonic analysis is applied to a least squares fit of the current observations at a set of knot points. Results from the harmonic analysis compare favorably to tidal parameters estimated from observations from moored instruments. The analysis shows that the tides are characterized by strong semi-diurnal component, with amplitudes of the principal Lunar constituent ranging from 1.6 cm/s in the Skagerrak to 67 cm/s in the Fair Isle Channel. Diurnal tides are found to be approximately one fifth the strength of the predominant semi-diurnal constituent. Output from a regional barotropic tide model compares well to tidal current determined from the harmonic analysis of the Acoustic Doppler Current Profiler data.

Characterizing the detectability of emission signals from a North Korean nuclear detonation

DOE PAGES

Werth, David; Buckley, Robert

2017-02-01

Here, the detectability of emission sources, defined by a low-level of mixing with other sources, was estimated for various locations surrounding the Sea of Japan, including a site within North Korea. A high-resolution meteorological model coupled to a dispersion model was used to simulate plume dynamics for four periods, and two metrics of airborne plume mixing were calculated for each source. While emissions from several known sources in this area tended to blend with others while dispersing downwind, the North Korean plume often remained relatively distinct, thereby making it potentially easier to unambiguously ‘backtrack’ it to its source.

Different nature of glacial CaCO3 constituents between MIS 2 and MIS 12 in the East Sea/Japan Sea and its paleoceanographic implication

NASA Astrophysics Data System (ADS)

Khim, Boo-Keun; Tada, Ryuji; Itaki, Takuya

2014-05-01

Two piston cores (PC-05 and PC-08) were collected on the Yamato Rise in the East Sea/Japan Sea during the KR07-12 cruise. A composite core was achieved with the successful replacement of almost half of the upper part of core PC-05 by the entirety of core PC-08 based on the co-equivalence of L* values and the dark layers, because an interval (170 cm to 410 cm) of core PC-05 was considerably disturbed due to fluidization during the core execution. Chronostratigraphy of the composite core was constructed by the direct comparison of L* values to the well-dated core MD01-2407 that was obtained in the Oki Ridge. The lower-bottom of the composite core reached back to Marine Isotope Stage (MIS) 14, based on the age estimate by LR04 stacks. Downcore opal variation of the composite core exhibited the distinct orbital-scale cyclic changes; high during the interglacial and low during the glacial periods. However, downcore CaCO3 variation showed no corresponding orbital-scale cyclic change between glacial and interglacial periods. Some intervals of both periods were high in CaCO3 content. Frequent and large fluctuations in CaCO3 content seemed to be more related to the presence of dark layers containing thin lamination (TL) within the glacial and interglacial intervals. It is worthy to note that MIS 2 and MIS 12 are characterized by distinctly high CaCO3 content, showing up to 18% and 73%, respectively, among the glacial periods. Furthermore, in terms of lithology, MIS 2 was characterized by a thick dark layer (low L* values) with TL, whereas MIS 12 preserved the distinctly light layer (high L* values) with parallel laminations. Another remarkable dissimilarity between MIS 2 and MIS 12 was the nature of their CaCO3 constituent; the CaCO3 constituent of MIS 2 consisted of mostly planktonic foraminifera, whereas that of MIS 12 was mostly dump of coccolithophorids, regardless the presence of planktonic foraminifera. The distinctness of the CaCO3 constituents between MIS 2 and MIS

Pleistocene environments and glacial history of the northern North Sea

NASA Astrophysics Data System (ADS)

Reinardy, Benedict; Hjelstuen, Berit; Petter Sejrup, Hans; Augedal, Hans; Jørstad, Arild

2017-04-01

Based on new geochronological and lithological data combined with analyses of 3D seismic data, the Pliocene-Pleistocene development of the central northern North Sea has been investigated. At the start of the Plio-Pleistocene Transition the study area was dominated by a deltaic, shallow marine or tidal depositional environment with sediments mainly sourced from the west with a local provenance. Directly above the base Quaternary a 60 m thick layer of mud-rich sediments of glacimarine origin were deposited at a rate of 12 cm/ka between 2-1.5 Ma and up to 80 cm/ka between 1.5 - 1.2 Ma possibly reflecting glacial ice advancing to the Norwegian coastline. The high rate of deposition in the Early Pleistocene occurred immediately before the initiation of the Norwegian Channel Ice Stream at 1.1 Ma. Following this, a large part of the sediment input from Fennoscandia seems to have been directed away from the study area to the shelf break. At the start of the Mid Pleistocene Transition (MPT), subaerial conditions allowed the formation of a >50 km long fluvial channel across the study area draining water from the east to the south west. The earliest evidence of grounded ice in the investigated area comes from mega scale glacial lineations formed during the MPT, at or just after 1.2 Ma. Following this, a regional unconformity was formed by one or more grounded ice advances across the study area possibly during or directly after the MPT and likely marks the boundary between the Early and Mid Pleistocene glacimarine sediments. The Mid to Late Pleistocene stratigraphy is dominated by glacimarine sediments and tills and is associated with multiple generations of tunnel valleys observed within the seismic data. A high shear strength till containing chalk clasts transported from the west and/or south of the study area was likely deposited during MIS6 and may have been more conducive to tunnel valley formation in comparison to lower shear strength tills deposited by later ice

An extreme event of sea-level rise along the Northeast Coast of North America in 2009-2010.

PubMed

Goddard, Paul B; Yin, Jianjun; Griffies, Stephen M; Zhang, Shaoqing

2015-02-24

The coastal sea levels along the Northeast Coast of North America show significant year-to-year fluctuations in a general upward trend. The analysis of long-term tide gauge records identified an extreme sea-level rise (SLR) event during 2009-10. Within this 2-year period, the coastal sea level north of New York City jumped by 128 mm. This magnitude of interannual SLR is unprecedented (a 1-in-850 year event) during the entire history of the tide gauge records. Here we show that this extreme SLR event is a combined effect of two factors: an observed 30% downturn of the Atlantic meridional overturning circulation during 2009-10, and a significant negative North Atlantic Oscillation index. The extreme nature of the 2009-10 SLR event suggests that such a significant downturn of the Atlantic overturning circulation is very unusual. During the twenty-first century, climate models project an increase in magnitude and frequency of extreme interannual SLR events along this densely populated coast.

The first find of massive pyrolusite in a deep-water basin of the Sea of Japan

NASA Astrophysics Data System (ADS)

Astakhova, N. V.; S"edin, V. T.; Mozherovsky, A. V.; Lopatnikov, E. A.

2015-05-01

Data are presented on the chemical composition and the content of microelements including REEs in samples of pyrolusite, todorokite, and birnessite collected from a depth of 3500-3200 m by dredging a nameless elevation in the Central Basin of the Sea of Japan. The samples of pyrolusite are characterized by high hardness and density (3.35 g/cm3). The conclusion of their hydrothermal genesis is made.

Mapping Relative Sea Level Influences of the Cape Fear Arch in southern North Carolina

NASA Astrophysics Data System (ADS)

Hawkes, A.; Kemp, A.; Capar, P.

2017-12-01

Long-term relative sea-level (RSL) records are a necessary benchmark by which to gauge present accelerated rates of sea-level rise, future sea-level predictions, and their implications to the coastal zone. The east coast of the United States functions as a significant region of latitudinal RSL variability due to the continuous recovery of land from the deglaciation of the Laurentide Ice Sheet since the Last Glacial Maximum. Differential glacial isostatic adjustment (GIA) along the coastline has caused higher rates of subsidence in areas around the former forbulge maxima near New Jersey and Delaware and lower rates to the north and south of this maxima. However, the coast between southern North Carolina and northern South Carolina is experiencing a slower rate of RSL rise then is seen in reconstructed GIA latitudinal trends along the U.S. east coast. It was thought that this could have been attributed to non-isostatic, long-term tectonic processes causing less GIA subsidence of the lithosphere within the region impacted by uplift from the Cape Fear Arch (CFA), an underlying crystalline basement high. A recent study suggests that RSL rise is slower around the CFA than areas to the north and south due to suggested CFA uplift rates of 0.24+0.15mm a-1. An absence of RSL records for 200km north of the CFA make mapping of its influence difficult. Additional RSL records to the north of the CFA allow for a better understanding of the asymmetrical distribution in the rate of RSL rise in this region. Because the distribution in the rate of RSLR between records is not linear it is important for these low-lying coastal communities to better understand their risk to future RSLR.

Temporal and spatial variations of 134Cs and 137Cs levels in the Sea of Japan and Pacific coastal region: Implications for dispersion of FDNPP-derived radiocesium.

PubMed

Inoue, M; Shirotani, Y; Yamashita, S; Takata, H; Kofuji, H; Ambe, D; Honda, N; Yagi, Y; Nagao, S

2018-02-01

To investigate the dispersion of Fukushima Dai-ichi Nuclear Power Plant (FDNPP)-derived radiocesium in the Sea of Japan and western Pacific coastal region and determine the sources of radiocesium in these areas, we examined the temporal and spatial variations of 134 Cs and 137 Cs concentrations (activities) during 2011-2016 in seawaters around the western Japanese Archipelago, particularly in the Sea of Japan. In May 2013, the surface concentration of 134 Cs was ∼0.5 mBq/L (decay-corrected to March 11, 2011), and that of 137 Cs exceeded the pre-accident level in this study area, where the effects of radiocesium depositions just after the FDNPP accident disappeared in surface waters in October 2011. Subsequently, radiocesium concentrations gradually increased during 2013-2016 (∼0.5-1 mBq/L for 134 Cs), exhibiting approximately homogeneous distributions in each year. The temporal and spatial variations of 134 Cs and 137 Cs concentrations indicated that FDNPP-derived radiocesium around the western Japanese Archipelago, including the Sea of Japan, has been supported by the Kuroshio Current and its branch, Tsushima Warm Current, during 2013-2016. However, in the Sea of Japan, the penetration of 134 Cs was limited to depths of less than ∼200 m during three years following the re-delivery of FDNPP-derived radiocesium. Copyright © 2017 Elsevier Ltd. All rights reserved.

A probabilistic storm surge risk model for the German North Sea and Baltic Sea coast

NASA Astrophysics Data System (ADS)

Grabbert, Jan-Henrik; Reiner, Andreas; Deepen, Jan; Rodda, Harvey; Mai, Stephan; Pfeifer, Dietmar

2010-05-01

The German North Sea coast is highly exposed to storm surges. Due to its concave bay-like shape mainly orientated to the North-West, cyclones from Western, North-Western and Northern directions together with astronomical tide cause storm surges accumulating the water in the German bight. Due to the existence of widespread low-lying areas (below 5m above mean sea level) behind the defenses, large areas including large economic values are exposed to coastal flooding including cities like Hamburg or Bremen. The occurrence of extreme storm surges in the past like e.g. in 1962 taking about 300 lives and causing widespread flooding and 1976 raised the awareness and led to a redesign of the coastal defenses which provide a good level of protection for today's conditions. Never the less the risk of flooding exists. Moreover an amplification of storm surge risk can be expected under the influence of climate change. The Baltic Sea coast is also exposed to storm surges, which are caused by other meteorological patterns. The influence of the astronomical tide is quite low instead high water levels are induced by strong winds only. Since the exceptional extreme event in 1872 storm surge hazard has been more or less forgotten. Although such an event is very unlikely to happen, it is not impossible. Storm surge risk is currently (almost) non-insurable in Germany. The potential risk is difficult to quantify as there are almost no historical losses available. Also premiums are difficult to assess. Therefore a new storm surge risk model is being developed to provide a basis for a probabilistic quantification of potential losses from coastal inundation. The model is funded by the GDV (German Insurance Association) and is planned to be used within the German insurance sector. Results might be used for a discussion of insurance cover for storm surge. The model consists of a probabilistic event driven hazard and a vulnerability module, furthermore an exposure interface and a financial

Bathymetric controls on Pliocene North Atlantic and Arctic sea surface temperature and deepwater production

USGS Publications Warehouse

Robinson, M.M.; Valdes, P.J.; Haywood, A.M.; Dowsett, H.J.; Hill, D.J.; Jones, S.M.

2011-01-01

The mid-Pliocene warm period (MPWP; ~. 3.3 to 3.0. Ma) is the most recent interval in Earth's history in which global temperatures reached and remained at levels similar to those projected for the near future. The distribution of global warmth, however, was different than today in that the high latitudes warmed more than the tropics. Multiple temperature proxies indicate significant sea surface warming in the North Atlantic and Arctic Oceans during the MPWP, but predictions from a fully coupled ocean-atmosphere model (HadCM3) have so far been unable to fully predict the large scale of sea surface warming in the high latitudes. If climate proxies accurately represent Pliocene conditions, and if no weakness exists in the physics of the model, then model boundary conditions may be in error. Here we alter a single boundary condition (bathymetry) to examine if Pliocene high latitude warming was aided by an increase in poleward heat transport due to changes in the subsidence of North Atlantic Ocean ridges. We find an increase in both Arctic sea surface temperature and deepwater production in model experiments that incorporate a deepened Greenland-Scotland Ridge. These results offer both a mechanism for the warming in the North Atlantic and Arctic Oceans indicated by numerous proxies and an explanation for the apparent disparity between proxy data and model simulations of Pliocene northern North Atlantic and Arctic Ocean conditions. Determining the causes of Pliocene warmth remains critical to fully understanding comparisons of the Pliocene warm period to possible future climate change scenarios. ?? 2011.

Long-term Trend of Satellite-observed Chlorophyll-a Concentration Variations in the East/Japan Sea

NASA Astrophysics Data System (ADS)

Park, J. E.; PARK, K. A.

2016-02-01

Long-term time-series of satellite ocean color data enable us to analyze the effects of climate change on ocean ecosystem through chlorophyll-a concentration as a proxy for phytoplankton biomass. In this study, we constructed a 17 year-long time-series dataset (1998-2014) of chlorophyll-a concentration by combining SeaWiFS (Obrview-2, 1997-2010) and MODIS (Aqua, 2002-present) data in the East Sea (Japan Sea). Several types of errors such as anonymously high values (a speckle error), stripe-like patterns, discrepancy originating from time gap between the two satellites were eliminated to enhance the accuracy of chlorophyll-a concentration data. The composited chlorophyll-a concentration maps, passing through the post-processing of the speckle errors, were improved significantly, by 14% of abnormal variability in maximum. Using the database, we investigated spatial and temporal variability of chlorophyll-a concentration in the East Sea. Spatial distribution of long-term trend of chlorophyll-a concentration indicated obvious distinction between northern and southern regions of the subpolar front. It revealed predominant seasonal variabilities as well as long-term changes in the timings of spring bloom. This study addresses the important role of local climate change on fast changing ecosystem of the East Sea as one of miniature oceans.

Forecasting petroleum discoveries in sparsely drilled areas: Nigeria and the North Sea

USGS Publications Warehouse

Attanasi, E.D.; Root, D.H.

1988-01-01

Decline function methods for projecting future discoveries generally capture the crowding effects of wildcat wells on the discovery rate. However, these methods do not accommodate easily situations where exploration areas and horizons are expanding. In this paper, a method is presented that uses a mapping algorithm for separating these often countervailing influences. The method is applied to Nigeria and the North Sea. For an amount of future drilling equivalent to past drilling (825 wildcat wells), future discoveries (in resources found) for Nigeria are expected to decline by 68% per well but still amount to 8.5 billion barrels of oil equivalent (BOE). Similarly, for the total North Sea for an equivalent amount and mix among areas of past drilling (1322 wildcat wells), future discoveries are expected to amount to 17.9 billion BOE, whereas the average discovery rate per well is expected to decline by 71%. ?? 1988 International Association for Mathematical Geology.

A wave equation migration method for receiver function imaging: 2. Application to the Japan subduction zone

NASA Astrophysics Data System (ADS)

Chen, Ling; Wen, Lianxing; Zheng, Tianyu

2005-11-01

The newly developed wave equation poststack depth migration method for receiver function imaging is applied to study the subsurface structures of the Japan subduction zone using the Fundamental Research on Earthquakes and Earth's Interior Anomalies (FREESIA) broadband data. Three profiles are chosen in the subsurface imaging, two in northeast (NE) Japan to study the subducting Pacific plate and one in southwest (SW) Japan to study the Philippine Sea plate. The descending Pacific plate in NE Japan is well imaged within a depth range of 50-150 km. The slab image exhibits a little more steeply dipping angle (˜32°) in the south than in the north (˜27°), although the general characteristics between the two profiles in NE Japan are similar. The imaged Philippine Sea plate in eastern SW Japan, in contrast, exhibits a much shallower subduction angle (˜19°) and is only identifiable at the uppermost depths of no more than 60 km. Synthetic tests indicate that the top 150 km of the migrated images of the Pacific plate is well resolved by our seismic data, but the resolution of deep part of the slab images becomes poor due to the limited data coverage. Synthetic tests also suggest that the breakdown of the Philippine Sea plate at shallow depths reflects the real structural features of the subduction zone, rather than caused by insufficient coverage of data. Comparative studies on both synthetics and real data images show the possibility of retrieval of fine-scale structures from high-frequency contributions if high-frequency noise can be effectively suppressed and a small bin size can be used in future studies. The derived slab geometry and image feature also appear to have relatively weak dependence on overlying velocity structure. The observed seismicity in the region confirms the geometries inferred from the migrated images for both subducting plates. Moreover, the deep extent of the Pacific plate image and the shallow breakdown of the Philippine Sea plate image are

Management and protection protocols for nesting sea turtles on Cape Hatteras National Seashore, North Carolina

USGS Publications Warehouse

Cohen, J.B.

2005-01-01

Executive Summary 1. The southeast U.S. population of the loggerhead turtle (Caretta caretta) has increased since the species was listed as federally threatened in 1978. Since standardized monitoring began in North Carolina in 1995, the number of nests at Cape Hatteras National Seashore (CAHA) fluctuated from year to year, and was lowest in 1996 and 1997 (39 nests) and highest in 2003 (101 nests). Green turtles (Chelonia mydas) and leatherback turtles (Dermochelys coriacea) have nested in small numbers at CAHA, sporadically over time. 2. Hatching success of sea turtle nests typically approaches 80%. At CAHA hatching success from 1999-2003 was low when hurricanes hit during the nesting season (30%-38%), and ranged from 52%-70% otherwise. Hatching success at CAHA is usually correlated with hatching success in the surrounding subpopulation (north Florida to North Carolina). 3. Inclement weather, predation, and human recreation can negatively impact nesting rate and hatching success. 4. Currently there is little protection from recreation at CAHA for nesting females and nests that have not been found by monitors. We propose three management options to provide such protection, and to increase protection for known nests and hatchlings. We propose an adaptive management framework for assessing the effectiveness of these management options in improving sea turtle nesting rate and nest and hatchling survival. 5. We recommend continued efforts to trap and remove mammalian predators from all sea turtle habitat. We further recommend intensive monitoring and surveillance of protected areas to determine the extent and timing of threats to nests and broods, including nest overwash, predation, and disturbance or vandalism by humans. 6. Continue to relocate nests and assist stranded turtles according to North Carolina Wildlife Resources Commission guidelines. 7. Artificial light sources pose a serious threat to sea turtles in some parts of CAHA, which must be remedied immediately

Revisiting the estimation of the North Sea air-sea flux of CO2 in 2001/02

NASA Astrophysics Data System (ADS)

Meyer, Maybritt; Paetsch, Johannes; Geyer, Beate; Thomas, Helmuth

2017-04-01

Based on seasonal observations of pCO2 and 6-hourly wind data derived from ERA-40 reanalysis data Thomas et al. (2004) estimated the annual North Sea net uptake of CO2 for the years 2001/02. The wind data were provided by the ECMWF with a spatial resolution of 1.125˚ (ECMWF, 2005). An updated estimate has now been achieved by using the more appropriate wind data set coastDat2 (Geyer, 2014) resulting from atmospheric hourly hindcast for Europe and the North Atlantic using COSMO-CLM version 4.8_clm_11 with spectral nudging from 1948-2015. The model uses a grid point distance of 0.22 degrees with an extension of about 68˚ W to 82˚ E, 25.6˚ N to 81.4˚ N. It could be shown that coastDat2 rather than ERA-40 data fit to observed hourly observations at the German Weather Service station Helgoland (54.175˚ N, 7.892˚ E). In most cases the coastDat2 values are larger than the ERA-40 values. The comparison of North Sea wide CO2 uptake yields 1.3 for ERA-40 and 1.8 mol CO2 m-2 a-1 for coastDat2 wind fields. References Geyer, B., 2014. Earth System Science Data, 6(1): 147-164. Doi:10.5194/essd-6-147-2014. ECMWF, 2005. http://www.ecmwf.int Thomas, H., Bozec, Y., Elkalay, K., de Baar, H.J.W., 2004. Science, 304: 1005-1008.

Distribution and air-sea exchange of current-use pesticides (CUPs) from East Asia to the high Arctic Ocean.

PubMed

Zhong, Guangcai; Xie, Zhiyong; Cai, Minghong; Möller, Axel; Sturm, Renate; Tang, Jianhui; Zhang, Gan; He, Jianfeng; Ebinghaus, Ralf

2012-01-03

Surface seawater and marine boundary layer air samples were collected on the ice-breaker R/V Xuelong (Snow Dragon) from the East China Sea to the high Arctic (33.23-84.5° N) in July to September 2010 and have been analyzed for six current-use pesticides (CUPs): trifluralin, endosulfan, chlorothalonil, chlorpyrifos, dacthal, and dicofol. In all oceanic air samples, the six CUPs were detected, showing highest level (>100 pg/m(3)) in the Sea of Japan. Gaseous CUPs basically decreased from East Asia (between 36.6 and 45.1° N) toward Bering and Chukchi Seas. The dissolved CUPs in ocean water ranged widely from Sea of Japan (35.2° N) and evenly distributed between 36.9 and 72.5° N, but it remained below the detection limit at the highest northern latitudes in Chukchi Sea. In contrast with other CUPs, concentrations of chlorothalonil and dacthal were more abundant in Chukchi Sea and in East Asia. The air-sea gas exchange of CUPs was generally dominated by net deposition. Latitudinal trends of fugacity ratios of α-endosulfan, chlorothalonil, and dacthal showed stronger deposition of these compounds in East Asia than in Chukchi Sea, while trifluralin showed stronger deposition in Chukchi Sea (-455 ± 245 pg/m(2)/day) than in the North Pacific (-241 ± 158 pg/m(2)/day). Air-sea gas exchange of chlorpyrifos varied from net volatilizaiton in East Asia (<40° N) to equilibrium or net deposition in the North Pacific and the Arctic.

Marine downscaling of a future climate scenario in the North Sea and possible effects on dinoflagellate harmful algal blooms.

PubMed

Friocourt, Y F; Skogen, M; Stolte, W; Albretsen, J

2012-01-01

Two hydrodynamic and ecological models were used to investigate the effects of climate change-according to the IPCC A1b emission scenario - on the primary productivity of the North Sea and on harmful algal blooms. Both models were forced with atmospheric fields from a regional downscaling of General Circulation Models to compare two sets of 20-year simulations representative of present climate (1984-2004) conditions and of the 2040s. Both models indicated a general warming of the North Sea by up to 0.8°C and a slight freshening by the 2040s. The models suggested that the eastern North Sea would be subjected to more temperature and salinity changes than the western part. In addition, the ecological modules of the models indicated that the warming up of the sea would result in a slightly earlier spring bloom. The one model that also computes the distribution of four different phytoplankton groups suggests an increase in the abundance of dinoflagellates, whereas the abundance of diatoms, flagellates and Phaeocystis sp. remains comparable to current levels, or decrease. Assuming that Dinophysis spp. would experience a similar increase in abundance as the modelled group of dinoflagellates, it is hypothesised that blooms of Dinophysis spp. may occur more frequently in the North Sea by 2040. However, implications for shellfish toxicity remain unclear.

Emerald oil field on production in North Sea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-08-31

This paper reports that Midland and Scottish Energy Ltd. (MSE) has placed Emerald oil field on stream in the U.K. North Sea with a floating production unit. Initial production, from two satellite wells, will be used to commission facilities. Three water injection wells have been unplugged and are ready for start-up. MSE will place a central cluster of wells-five producers and one water injector-on stream during the next few weeks. Production will build to an expected 25,000 b/d from 35 million bbl of reserves. Field development has undergone an unusually large number of setbacks and changes.

Role of cold water and beta-effect in the formation of the East Korean Warm Current in the East/Japan Sea: a numerical experiment

NASA Astrophysics Data System (ADS)

Kim, Yong-Yub; Cho, Yang-Ki; Kim, Young Ho

2018-06-01

The contributions of bottom cold water and planetary β-effect to the formation of the East Korean Warm Current (EKWC), the western boundary current in the East/Japan Sea (EJS), were evaluated using an idealized three-dimensional numerical model. The model results suggest that the bottom cold water and, to a lesser extent, the planetary β-effect both contribute to the formation of the EKWC. The cold water functions as the bottom of the upper layer, to control the EKWC via conservation of potential vorticity. It is known that cold waters, such as the North Korean Cold Water and Korea Strait Bottom Cold Water often observed during summer along the southwestern coast of the EJS, originate from the winter convection in the northern area. Observational studies consistently show that the EKWC strengthens in summer when the cold water extends further south along the western boundary.

Holocene sea surface temperature and sea ice extent in the Okhotsk and Bering Seas

USGS Publications Warehouse

Harada, Naomi; Katsuki, Kota; Nakagawa, Mitsuhiro; Matsumoto, Akiko; Seki, Osamu; Addison, Jason A.; Finney, Bruce P.; Sato, Miyako

2014-01-01

Accurate prediction of future climate requires an understanding of the mechanisms of the Holocene climate; however, the driving forces, mechanisms, and processes of climate change in the Holocene associated with different time scales remain unclear. We investigated the drivers of Holocene sea surface temperature (SST) and sea ice extent in the North Pacific Ocean, and the Okhotsk and Bering Seas, as inferred from sediment core records, by using the alkenone unsaturation index as a biomarker of SST and abundances of sea ice-related diatoms (F. cylindrus and F. oceanica) as an indicator of sea ice extent to explore controlling mechanisms in the high-latitude Pacific. Temporal changes in alkenone content suggest that alkenone production was relatively high during the middle Holocene in the Okhotsk Sea and the western North Pacific, but highest in the late Holocene in the eastern Bering Sea and the eastern North Pacific. The Holocene variations of alkenone-SSTs at sites near Kamchatka in the Northwest Pacific, as well as in the western and eastern regions of the Bering Sea, and in the eastern North Pacific track the changes of Holocene summer insolation at 50°N, but at other sites in the western North Pacific, in the southern Okhotsk Sea, and the eastern Bering Sea they do not. In addition to insolation, other atmosphere and ocean climate drivers, such as sea ice distribution and changes in the position and activity of the Aleutian Low, may have systematically influenced the timing and magnitude of warming and cooling during the Holocene within the subarctic North Pacific. Periods of high sea ice extent in both the Okhotsk and Bering Seas may correspond to some periods of frequent or strong winter–spring dust storms in the Mongolian Gobi Desert, particularly one centered at ∼4–3 thousand years before present (kyr BP). Variation in storm activity in the Mongolian Gobi Desert region may reflect changes in the strength and positions of the Aleutian Low and Siberian

Biogeography of Coptis Salisb. (Ranunculales, Ranunculaceae, Coptidoideae), an Eastern Asian and North American genus.

PubMed

Xiang, Kun-Li; Erst, Andrey S; Xiang, Xiao-Guo; Jabbour, Florian; Wang, Wei

2018-05-24

Numerous studies have favored dispersal (colonization) over vicariance (past fragmentation) events to explain eastern Asian-North American distribution patterns. In plants, however the disjunction between eastern Asia and western North America has been rarely examined using the integration of phylogenetic, molecular dating, and biogeographical methods. Meanwhile, the biogeographic patterns within eastern Asia remain poorly understood. The goldthread genus Coptis Salisb. includes 15 species disjunctly distributed in North America, Japan, mainland China, and Taiwan. We present a dated phylogeny for Coptis under the optimal clock model and infer its historical biogeography by comparing different biogeographic models. The split of Coptis and Xanthorhiza Marshall occurred in the middle Miocene (ca. 15.47 Ma). Coptis started their diversification in the early late Miocene (ca. 9.55 Ma). A late Miocene vicariance event resulted in the eastern Asian and western North American disjunction in the genus. Within eastern Asia, dispersals from mainland Asia to Japan and from Japan to Taiwan occurred at ca. 4.85 Ma and at ca. 1.34 Ma, respectively. Our analyses provide evidence that both vicariance and dispersal events have played important roles in shaping the current distribution and endemism of Coptis, likely resulting from eustatic sea-level changes, mountain formation processes and an increasing drier and cooler climate from the middle Miocene onwards.

Elongation Of The North Anatolian Fault Zone in the Sea of Marmara

NASA Astrophysics Data System (ADS)

Kurtulus, C.; Canbay, M. M.

2003-04-01

The North Anatolian Fault Zone (NAFZ) is a 1500 km long, seismically active, right lateral strike sleep fault that accommodates the relative motion between the Anatolian and Pontide blocks. The Sea of Marmara is an intra-continental sea lying along the western part of the NAFZ. There are two major fault systems in the Sea of Marmara one of which consists of the east-west striking faults and the other one is made up of NE-SW-trending faults that dissect the first group. The east, middle and the south parts of the Sea of Marmara are interpreted as pull-apart basins characterized by shear stresses. The interpretation of the structural framework indicates that the northern strand of the NAFZ traverses the Gulf of Izmit and deep Marmara to bind the Gulf of Saros and the middle strand of it traverses the Gulf of Gemlik, Bandirma and the Gulf of Erdek.

8 January 2013 Mw=5.7 North Aegean Sea Earthquake Sequence

NASA Astrophysics Data System (ADS)

Kürçer, Akın; Yalçın, Hilal; Gülen, Levent; Kalafat, Doǧan

2014-05-01

The deformation of the North Aegean Sea is mainly controlled by the westernmost segments of North Anatolian Fault Zone (NAFZ). On January 8, 2013, a moderate earthquake (Mw= 5.7) occurred in the North Aegean Sea, which may be considered to be a part of westernmost splay of the NAFZ. A series of aftershocks were occurred within four months following the mainschock, which have magnitudes varying from 1.9 to 5.0. In this study, a total of 23 earthquake moment tensor solutions that belong to the 2013 earthquake sequence have been obtained by using KOERI and AFAD seismic data. The most widely used Gephart & Forsyth (1984) and Michael (1987) methods have been used to carry out stress tensor inversions. Based on the earthquake moment tensor solutions, distribution of epicenters and seismotectonic setting, the source of this earthquake sequence is a N75°E trending pure dextral strike-slip fault. The temporal and spatial distribution of earthquakes indicate that the rupture unilaterally propagated from SW to NE. The length of the fault has been calculated as approximately 12 km. using the afterschock distribution and empirical equations, suggested by Wells and Coppersmith (1994). The stress tensor analysis indicate that the dominant faulting type in the region is strike-slip and the direction of the regional compressive stress is WNW-ESE. The 1968 Aghios earthquake (Ms=7.3; Ambraseys and Jackson, 1998) and 2013 North Aegean Sea earthquake sequences clearly show that the regional stress has been transferred from SW to NE in this region. The last historical earthquake, the Bozcaada earthquake (M=7.05) had been occurred in the northeast of the 2013 earthquake sequence in 1672. The elapsed time (342 year) and regional stress transfer point out that the 1672 earthquake segment is probably a seismic gap. According to the empirical equations, the surface rupture length of the 1672 Earthquake segment was about 47 km, with a maximum displacement of 170 cm and average displacement

Potential contribution of surface-dwelling Sargassum algae to deep-sea ecosystems in the southern North Atlantic

NASA Astrophysics Data System (ADS)

Baker, Philip; Minzlaff, Ulrike; Schoenle, Alexandra; Schwabe, Enrico; Hohlfeld, Manon; Jeuck, Alexandra; Brenke, Nils; Prausse, Dennis; Rothenbeck, Marcel; Brix, Saskia; Frutos, Inmaculada; Jörger, Katharina M.; Neusser, Timea P.; Koppelmann, Rolf; Devey, Colin; Brandt, Angelika; Arndt, Hartmut

2018-02-01

Deep-sea ecosystems, limited by their inability to use primary production as a source of carbon, rely on other sources to maintain life. Sedimentation of organic carbon into the deep sea has been previously studied, however, the high biomass of sedimented Sargassum algae discovered during the VEMA Transit expedition in 2014/2015 to the southern North Atlantic, and its potential as a regular carbon input, has been an underestimated phenomenon. To determine the potential for this carbon flux, a literature survey of previous studies that estimated the abundance of surface water Sargassum was conducted. We compared these estimates with quantitative analyses of sedimented Sargassum appearing on photos taken with an autonomous underwater vehicle (AUV) directly above the abyssal sediment during the expedition. Organismal communities associated to Sargassum fluitans from surface waters were investigated and Sargassum samples collected from surface waters and the deep sea were biochemically analyzed (fatty acids, stable isotopes, C:N ratios) to determine degradation potential and the trophic significance within deep-sea communities. The estimated Sargassum biomass (fresh weight) in the deep sea (0.07-3.75 g/m2) was several times higher than that estimated from surface waters in the North Atlantic (0.024-0.84 g/m2). Biochemical analysis showed degradation of Sargassum occurring during sedimentation or in the deep sea, however, fatty acid and stable isotope analysis did not indicate direct trophic interactions between the algae and benthic organisms. Thus, it is assumed that components of the deep-sea microbial food web form an important link between the macroalgae and larger benthic organisms. Evaluation of the epifauna showed a diverse nano- micro-, meio, and macrofauna on surface Sargassum and maybe transported across the Atlantic, but we had no evidence for a vertical exchange of fauna components. The large-scale sedimentation of Sargassum forms an important trophic link

Spatially-Resolved Influence of Temperature and Salinity on Stock and Recruitment Variability of Commercially Important Fishes in the North Sea

PubMed Central

Akimova, Anna; Núñez-Riboni, Ismael; Kempf, Alexander; Taylor, Marc H.

2016-01-01

Understanding of the processes affecting recruitment of commercially important fish species is one of the major challenges in fisheries science. Towards this aim, we investigated the relation between North Sea hydrography (temperature and salinity) and fish stock variables (recruitment, spawning stock biomass and pre-recruitment survival index) for 9 commercially important fishes using spatially-resolved cross-correlation analysis. We used high-resolution (0.2° × 0.2°) hydrographic data fields matching the maximal temporal extent of the fish population assessments (1948–2013). Our approach allowed for the identification of regions in the North Sea where environmental variables seem to be more influential on the fish stocks, as well as the regions of a lesser or nil influence. Our results confirmed previously demonstrated negative correlations between temperature and recruitment of cod and plaice and identified regions of the strongest correlations (German Bight for plaice and north-western North Sea for cod). We also revealed a positive correlation between herring spawning stock biomass and temperature in the Orkney-Shetland area, as well as a negative correlation between sole pre-recruitment survival index and temperature in the German Bight. A strong positive correlation between sprat stock variables and salinity in the central North Sea was also found. To our knowledge the results concerning correlations between North Sea hydrography and stocks’ dynamics of herring, sole and sprat are novel. The new information about spatial distribution of the correlation provides an additional help to identify mechanisms underlying these correlations. As an illustration of the utility of these results for fishery management, an example is provided that incorporates the identified environmental covariates in stock-recruitment models. PMID:27584155

Trace element levels in fish from clean and polluted coastal marine sites in the Mediterranean Sea, Red Sea and North Sea

NASA Astrophysics Data System (ADS)

Kress, Nurit; Herut, Barak; Shefer, Edna; Hornung, Hava

1999-12-01

The bioaccumulation of Hg, Cd, Zn, Cu, Mn and Fe was evaluated in the muscle and liver tissue of four fish species (Siganus rivulatus, Diplodus sargus, Lithognatus mormyrus and Plathychtis flesus) from clean and polluted marine coastal sites in the Red Sea, Mediterranean Sea and North Sea within the framework of the MARS 1 program. Representative liver samples were screened for organic contaminants (DDE, PCBs and PAHs) which exhibited very low concentrations. The levels of Cd, Cu, Zn, Fe and Mn found in the muscle tissue in this study were similar among the four species and within the naturally occurring metal ranges. However, differences were found among the sites. In the Red Sea, Cu was higher in the muscle of S. rivulatus at Ardag and Zn at the Observatory (OBS). Cu, Zn and Mn were higher in the Red Sea than in the specimens from the Mediterranean. The differences were attributed to different diets derived from distinctively different natural environments. D. sargus from Haifa Bay (HB) had higher Cd, Cu and Mn values than specimens from Jaffa (JFA), and L. mormyrus higher Cd, Fe and Mn in HB, corresponding to the polluted environmental status of the Bay. No differences in metal levels were found among the North Sea sites, except for Fe that was lower at the Eider station. Hg was low in all the specimens, but the values varied with species and sites. The lowest Hg values were found in S. rivulatus, the herbivorous species, as expected from its trophic level. Hg in P. flesus was higher than in S. rivulatus but still low. Higher Hg values were found in the muscle tissue of L. mormyrus,with the highest values in D. sargus, both carnivorous species from the same family. Hg in D. sargus was higher in HB than in JFA, as expected, but in the larger specimens of L. mormyrus from JFA values were higher, while in the small specimens there were no differences in Hg values. The levels of all metals were higher in the liver than in the muscle, with enrichment factors ranging

Recent observations in the straits of the East/Japan Sea: A review of hydrography, currents and volume transports

NASA Astrophysics Data System (ADS)

Na, Hanna; Isoda, Yutaka; Kim, Kuh; Kim, Young Ho; Lyu, Sang Jin

2009-09-01

Recent observations of hydrography, currents and volume transports in the straits of the East/Japan Sea are reviewed. It is newly found that bottom cold water in the Korea/Tsushima Strait originating from the northern region of the East/Japan Sea appears not only in summer and autumn but also in winter. Intensive observations in the Korea/Tsushima Strait revealed two distinct cores of northeastward currents in the upper layer of the western and eastern channels. Mean volume transport through the Korea/Tsushima Strait is calculated as 2.5 ± 0.5 Sv from four-year direct and indirect measurements. As continuous monitoring has started in the Tsugaru and Soya Straits, understanding of temporal variability of currents and volume transports through the straits is in progress. For the first time, simultaneous time series of volume transports are available in the Korea/Tsushima and Tsugaru Straits during the winter of 1999-2000. Ouflow through the Tsugaru Strait accounts for about 70% of inflow through the Korea/Tsushima Strait for this period.

Climate drift of AMOC, North Atlantic salinity and arctic sea ice in CFSv2 decadal predictions

NASA Astrophysics Data System (ADS)

Huang, Bohua; Zhu, Jieshun; Marx, Lawrence; Wu, Xingren; Kumar, Arun; Hu, Zeng-Zhen; Balmaseda, Magdalena A.; Zhang, Shaoqing; Lu, Jian; Schneider, Edwin K.; Kinter, James L., III

2015-01-01

There are potential advantages to extending operational seasonal forecast models to predict decadal variability but major efforts are required to assess the model fidelity for this task. In this study, we examine the North Atlantic climate simulated by the NCEP Climate Forecast System, version 2 (CFSv2), using a set of ensemble decadal hindcasts and several 30-year simulations initialized from realistic ocean-atmosphere states. It is found that a substantial climate drift occurs in the first few years of the CFSv2 hindcasts, which represents a major systematic bias and may seriously affect the model's fidelity for decadal prediction. In particular, it is noted that a major reduction of the upper ocean salinity in the northern North Atlantic weakens the Atlantic meridional overturning circulation (AMOC) significantly. This freshening is likely caused by the excessive freshwater transport from the Arctic Ocean and weakened subtropical water transport by the North Atlantic Current. A potential source of the excessive freshwater is the quick melting of sea ice, which also causes unrealistically thin ice cover in the Arctic Ocean. Our sensitivity experiments with adjusted sea ice albedo parameters produce a sustainable ice cover with realistic thickness distribution. It also leads to a moderate increase of the AMOC strength. This study suggests that a realistic freshwater balance, including a proper sea ice feedback, is crucial for simulating the North Atlantic climate and its variability.

Biweekly Sea Surface Temperature over the South China Sea and its association with the Western North Pacific Summer Monsoon

NASA Astrophysics Data System (ADS)

Vaid, B. H.

2017-02-01

The association of the biweekly intraseasonal (BWI) oscillation in the Sea Surface Temperature (SST) over the South China Sea (SCS) and the Western North Pacific Summer Monsoon is authenticated using version 4 the Tropical Rainfall Measuring Mission Microwave Imager data (SST and rain) and heat fluxes from Ocean Atmosphere Flux project data during 1998-2012. The results suggest that the SCS involves ocean-atmosphere coupling on biweekly timescales. The positive biweekly SST anomalies lead the rain anomalies over the SCS by 3 days, with a significant correlation coefficient ( r = 0.6, at 99 % significance levels) between the SST-rain anomalies. It is evident from lead/lag correlation between biweekly SST and zonal wind shear that warm ocean surface induced by wind shear may contribute to a favorable condition of the convective activity over the SCS. The present study suggests that ocean-to-atmospheric processes induced by the BWI oscillation in the SCS SST results in enhanced sea level pressure and surface shortwave radiation flux during the summer monsoon. Besides, it is observed that the SCS BWI oscillation in the changes of SST causes a feedback in the atmosphere by modifying the atmospheric instability. This suggests that the active/break biweekly cycle of the SST over the SCS is related by sea level pressure, surface heat fluxes and atmospheric instability. The potential findings here indicate that the biweekly SST over the SCS play an important role in the eastward and the southward propagation of the biweekly anomalies in the Western North Pacific.

Nitrate consumption in sediments of the German Bight (North Sea)

NASA Astrophysics Data System (ADS)

Neumann, Andreas; van Beusekom, Justus E. E.; Holtappels, Moritz; Emeis, Kay-Christian

2017-09-01

Denitrification on continental margins and in coastal sediments is a major sink of reactive N in the present nitrogen cycle and a major ecosystem service of eutrophied coastal waters. We analyzed the nitrate removal in surface sediments of the Elbe estuary, Wadden Sea, and adjacent German Bight (SE North Sea) during two seasons (spring and summer) along a eutrophication gradient ranging from a high riverine nitrate concentrations at the Elbe Estuary to offshore areas with low nitrate concentrations. The gradient encompassed the full range of sediment types and organic carbon concentrations of the southern North Sea. Based on nitrate penetration depth and concentration gradient in the porewater we estimated benthic nitrate consumption rates assuming either diffusive transport in cohesive sediments or advective transport in permeable sediments. For the latter we derived a mechanistic model of porewater flow. During the peak nitrate discharge of the river Elbe in March, the highest rates of diffusive nitrate uptake were observed in muddy sediments (up to 2.8 mmol m- 2 d- 1). The highest advective uptake rate in that period was observed in permeable sediment and was tenfold higher (up to 32 mmol m- 2 d- 1). The intensity of both diffusive and advective nitrate consumption dropped with the nitrate availability and thus decreased from the Elbe estuary towards offshore stations, and were further decreased during late summer (minimum nitrate discharge) compared to late winter (maximum nitrate discharge). In summary, our rate measurements indicate that the permeable sediment accounts for up to 90% of the total benthic reactive nitrogen consumption in the study area due to the high efficiency of advective nitrate transport into permeable sediment. Extrapolating the averaged nitrate consumption of different sediment classes to the areas of Elbe Estuary, Wadden Sea and eastern German Bight amounts to an N-loss of 3.1 ∗ 106 mol N d- 1 from impermeable, diffusion

Drivers of summer oxygen depletion in the central North Sea

NASA Astrophysics Data System (ADS)

Queste, B. Y.; Fernand, L.; Jickells, T. D.; Heywood, K. J.; Hind, A. J.

2015-06-01

In stratified shelf seas, oxygen depletion beneath the thermocline is a result of a greater rate of biological oxygen demand than the rate of supply of oxygenated water. Suitably equipped gliders are uniquely placed to observe both the supply through the thermocline and the consumption of oxygen in the bottom layers. A Seaglider was deployed in the shallow (≈ 100 m) stratified North Sea in a region of known low oxygen during August 2011 to investigate the processes regulating supply and consumption of dissolved oxygen below the pycnocline. The first deployment of such a device in this area, it provided extremely high resolution observations, 316 profiles (every 16 min, vertical resolution of 1 m) of CTD, dissolved oxygen concentrations, backscatter and fluorescence during a three day deployment. The high temporal resolution observations revealed occasional small scale events that supply oxygenated water into the bottom layer at a rate of 2±1 μmol dm-3 day-1. Benthic and pelagic oxygen sinks, quantified through glider observations and past studies, indicate more gradual background consumption rates of 2.5±1 μmol dm-3 day-1. This budget revealed that the balance of oxygen supply and demand is in agreement with previous studies of the North Sea. However, the glider data show a net oxygen consumption rate of 2.8±0.3 μmol dm-3 day-1 indicating a localised or short-lived increase in oxygen consumption rates. This high rate of oxygen consumption is indicative of an unidentified oxygen sink. We propose that this elevated oxygen consumption is linked to localised depocentres and rapid remineralisation of resuspensded organic matter. The glider proved to be an excellent tool for monitoring shelf sea processes despite challenges to glider flight posed by high tidal velocities, shallow bathymetry, and very strong density gradients. The direct observation of these processes allows more up to date rates to be used in the development of ecosystem models.

Drivers of summer oxygen depletion in the central North Sea

NASA Astrophysics Data System (ADS)

Queste, Bastien Y.; Fernand, Liam; Jickells, Timothy D.; Heywood, Karen J.; Hind, Andrew J.

2016-02-01

In stratified shelf seas, oxygen depletion beneath the thermocline is a result of a greater rate of biological oxygen demand than the rate of supply of oxygenated water. Suitably equipped gliders are uniquely placed to observe both the supply through the thermocline and the consumption of oxygen in the bottom layers. A Seaglider was deployed in the shallow (≍ 100 m) stratified North Sea in a region of known low oxygen during August 2011 to investigate the processes regulating supply and consumption of dissolved oxygen below the pycnocline. The first deployment of such a device in this area, it provided extremely high-resolution observations, 316 profiles (every 16 min, vertical resolution of 1 m) of conductivity, temperature, and depth (CTD), dissolved oxygen concentrations, backscatter, and fluorescence during a 3-day deployment.The high temporal resolution observations revealed occasional small-scale events (< 200 m or 6 h) that supply oxygenated water to the bottom layer at a rate of 2 ± 1 µmol dm-3 day-1. Benthic and pelagic oxygen sinks, quantified through glider observations and past studies, indicate more gradual background consumption rates of 2.5 ± 1 µmol dm-3 day-1. This budget revealed that the balance of oxygen supply and demand is in agreement with previous studies of the North Sea. However, the glider data show a net oxygen consumption rate of 2.8 ± 0.3 µmol dm-3 day-1, indicating a localized or short-lived (< 200 m or 6 h) increase in oxygen consumption rates. This high rate of oxygen consumption is indicative of an unidentified oxygen sink. We propose that this elevated oxygen consumption is linked to localized depocentres and rapid remineralization of resuspended organic matter.The glider proved to be an excellent tool for monitoring shelf sea processes despite challenges to glider flight posed by high tidal velocities, shallow bathymetry, and very strong density gradients. The direct observation of these processes allows more up to date

Seasonal carbon uptake rates of phytoplankton in the northern East/Japan Sea

NASA Astrophysics Data System (ADS)

Lee, Sang Heon; Joo, HuiTae; Lee, Jae Hyung; Lee, Jang Han; Kang, Jae Joong; Lee, Ho Won; Lee, Dabin; Kang, Chang Keun

2017-09-01

Korea-Russia joint expeditions have been conducted mainly in the less studied Russian sector of the East/Japan Sea to understand the physical and ecological structures. In this study, the carbon uptake rates of phytoplankton measured in 2012 (middle-late October) and 2015 (middle April-early May) were analyzed to understand seasonal and spatial distributions of phytoplankton production, using a 13C-15N dual isotope tracer technique. The water columns in the euphotic layers were well mixed during our cruise periods in both years. The water column-integrated chl-a concentrations (mean ± S.D. = 2.28 ± 1.47 mg m-3) in 2015 was significantly higher (t-test, p < 0.01) than in 2012 (mean ± S.D. = 0.49 ± 0.29 mg m-3) because of different sampling seasons. Small phytoplankton (< 2 μm) were relatively dominant in 2012, whereas different sizes of phytoplankton were evenly distributed in 2015 although a spatial distribution of large phytoplankton (> 20 μm) was observed near the Russian coast. The daily carbon uptake rates in this study were 180.5 and 441.6 mg C m-2 d-1 in 2012 and 2015, respectively which are significantly (t-test, p < 0.01) lower than the averaged values previously reported in the East/Japan Sea (863 ± 679.6 mg C m-2 d-1). The potential reasons for the lower rate in this study are discussed. The small phytoplankton contribution (47.4%) averaged from the two different cruises in this study is consistent with the result (47%) reported in temperate regions. Moreover, a significantly (t-test, p < 0.01) lower contribution of small phytoplankton in total primary production than total phytoplankton biomass in this study is consistent with the results from other regions. Lower total primary production might be expected due to increasing contribution of small phytoplankton under warmer conditions.

Prevalence and causes of loss of consciousness in former North Sea occupational divers.

PubMed

Sundal, Endre; Irgens, Ågot; Troland, Kari; Thorsen, Einar; Grønning, Marit

2013-01-01

Loss of consciousness (LOC) is a serious event during diving. The purpose of this study wasto estimate the prevalence and causes of LOC during diving in former North Sea divers, and the impacton health-related quality of life. Up to 1990 a total of 373 Norwegian offshore divers worked in the North Sea. From 2000 to 2011, 221 of these were referred to the Department of Occupational Medicine at Haukeland University Hospital for examination due to health complaints. They filled in a questionnaire for registration of diving experience and health complaints, including the SF-36 version 1 for the assessment of quality oflife. The questionnaire and the hospital records were systematically reviewed by 2 independent observers. Episodes of LOC during diving and the causes were registered. All participants underwent a clinical neurological examination. Electroencephalogram (EEG) and the event-related brain potential (P300) were recorded. One or more episodes of LOC were reported by 58 of 219 divers. LOC due to gas cut was reportedby 27 of these. Divers having experienced LOC due to gas cut had lower SF-36 sub-scores then the rest of the diving population. EEG and P300 recordings did not differ between the groups. A high proportion of former Norwegian North Sea divers reported episodes of LOC, for whichgas cut was the most common cause. Both hypoxia and peritraumatic stress associated with the episodecould have a long term impact on the quality of life. Neurophysiological functions, however, did not differbetween the groups.

Spatial patterns of increases and decreases in the length of the sea ice season in the north polar region, 1979-1986

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.

1992-01-01

Recently it was reported that sea ice extents in the Northern Hemisphere showed a very slight but statistically significant decrease over the 8.8-year period of the Nimbus 7 scanning multichannel microwave radiometer (SMMR) data set. In this paper the same SMMR data are used to reveal spatial patterns in increasing and decreasing sea ice coverage. Specifically, the length of the ice season is mapped for each full year of the SMMR data set (1979-1986), and the trends over the 8 years in these ice season lengths are also mapped. These trends show considerable spatial coherence, with a shortening in the sea ice season apparent in much of the eastern hemisphere of the north polar ice cover, particularly in the Sea of Okhotsk, the Barents Sea, and the Kara Sea, and a lengthening of the sea ice season apparent in much of the western hemisphere of the north polar ice cover, particularly in Davis Strait, the Labrador Sea, and the Beaufort Sea.

Solar wind: A possible factor driving the interannual sea surface temperature tripolar mode over North Atlantic

NASA Astrophysics Data System (ADS)

Xiao, Ziniu; Li, Delin

2016-06-01

The effect of solar wind (SW) on the North Atlantic sea surface temperature (SST) in boreal winter is examined through an analysis of observational data during 1964-2013. The North Atlantic SSTs show a pronounced meridional tripolar pattern in response to solar wind speed (SWS) variations. This pattern is broadly similar to the leading empirical orthogonal function (EOF) mode of interannual variations in the wintertime SSTs over North Atlantic. The time series of this leading EOF mode of SST shows a significant interannual period, which is the same as that of wintertime SWS. This response also appears as a compact north-south seesaw of sea level pressure and a vertical tripolar structure of zonal wind, which simultaneously resembles the North Atlantic Oscillation (NAO) in the overlying atmosphere. As compared with the typical low SWS winters, during the typical high SWS winters, the stratospheric polar night jet (PNJ) is evidently enhanced and extends from the stratosphere to the troposphere, even down to the North Atlantic Ocean surface. Notably, the North Atlantic Ocean is an exclusive region in which the SW signal spreads downward from the stratosphere to the troposphere. Thus, it seems that the SW is a possible factor for this North Atlantic SST tripolar mode. The dynamical process of stratosphere-troposphere coupling, together with the global atmospheric electric circuit-cloud microphysical process, probably accounts for the particular downward propagation of the SW signal.

Linking a sea level pressure anomaly dipole over North America to the central Pacific El Niño

NASA Astrophysics Data System (ADS)

Ding, Ruiqiang; Li, Jianping; Tseng, Yu-heng; Sun, Cheng; Zheng, Fei

2017-08-01

This study demonstrates the close connection between the north-south dipole pattern of sea level pressure anomalies over northeastern North America to the western tropical North Atlantic, referred to as the North American dipole (NAD), and the central Pacific (CP)-type El Niño a year later. In contrast to other ENSO precursors, such as the North Pacific Oscillation (NPO) and Pacific-North America (PNA) pattern, the NAD appears more closely related to the CP-type El Niño than to the eastern Pacific (EP)-type El Niño, indicating that the NAD may serve as a unique precursor for the CP El Niño. The wintertime NAD induces sea surface temperature anomalies in the northern tropical Atlantic (NTA), which subsequently play an important role in developing the CP El Niño-like pattern in the tropical Pacific over the course of the following year. It appears that the NAD influence on CP El Niño involves air-sea interaction over several major basins, including the subtropical/tropical Pacific and the NTA. Additional analysis indicates that the correlation of either the NAD index or the NPO index with the CP El Niño state a year later depends on the status of the other index. When the wintertime NAD index is of the opposite sign to the simultaneous NPO index, the correlation of the NAD or NPO index with the Niño4 index becomes much weaker.

Evolution of ice sheets in the early Quaternary of the central North Sea: 2.58 Ma to 0.78 Ma

NASA Astrophysics Data System (ADS)

Lamb, R.; Huuse, M.; Stewart, M.; Brocklehurst, S. H.

2016-12-01

Integration of chronostratigraphic proxies with 3D seismic and well-log data has allowed for a basin-wide re-interpretation of the onset of glaciation in the central North Sea during the Quaternary. Mapping of seismic geomorphology, calculations of water depth and sediment accumulation rates, and other basin analysis techniques unravel the evolution of the North Sea basin during the early Pleistocene, a period of dramatic global cooling and rapid 41 kyr glacial-interglacial cycles, identifying a system which is increasingly dominated by large, continental-scale ice sheets. Prior to this study continental-scale ice sheets were generally not considered able to grow in a 41 kyr cycle and the earliest date for such an ice sheet in the North Sea was identified at the onset of tunnel valley formation in the Elsterian (0.48 Ma; MIS 12) which forms a large regional-scale glacial unconformity. At the onset of the Pleistocene at 2.58 Ma the North Sea basin was an elongate `mega-fjord' with water depths of up to 350 m, infilling rapidly as the European river systems deposited a large clinoform complex in the southern end of the basin. This period corresponds to the preservation of large scale ice-berg scouring on clinoform topsets, suggesting the presence of marine-terminating ice sheets with repeated calving events. As the Pleistocene progressed and global climate became increasingly colder the North Sea became smaller and shallower due to the continual infill of the basin. At 1.72 Ma the basin reached a critical point between the cold climate and the shallowing of the basin and the first evidence for grounded glaciation in the form of mega-scale glacial lineations is seen at this level. Between 1.72 and 0.48 Ma there is evidence for ice-streaming in the form of multiple MSGL flow sets re-occupying the central North Sea, as well as a large glaciotectonic complex. The glacial geomorphological evidence presented pushes back the date of grounded glaciation in the central North

Shift Work Disorder Among Oil Rig Workers in the North Sea

PubMed Central

Waage, Siri; Moen, Bente Elisabeth; Pallesen, Ståle; Eriksen, Hege R.; Ursin, Holger; Åkerstedt, Torbj⊘rn; Bjorvatn, Bj⊘rn

2009-01-01

Study Objectives: Shift work disorder (SWD) is a circadian rhythm sleep disorder caused by work hours during the usual sleep period. The main symptoms are excessive sleepiness and insomnia temporally associated with the working schedule. The aim of the present study was to examine SWD among shift workers in the North Sea. Design and Participants: A total of 103 shift workers (2 weeks on 7 nights/ 7days, 12-h shifts, 4 weeks off), mean age 39.8 years, working at an oil rig in the North Sea responded to a questionnaire about SWD. They also completed the Pittsburgh Sleep Quality Index, Bergen Insomnia Scale, Epworth Sleepiness Scale, Composite Morningness Questionnaire, Subjective Health Complaint Inventory, Demand/Control, and Instrumental Mastery Oriented Coping (based on the Utrecht Coping list). Most of these instruments were administered during the first day of the 2-week working period, thus reflecting symptoms and complaints during the 4-week non-work period. The shift workers were also compared to day workers at the oil rig. Results: Twenty-four individuals were classified as suffering from SWD, yielding a prevalence for SWD of 23.3%. During the 4-week non-work period, individuals with SWD reported significantly poorer sleep quality, as measured by the Pittsburgh Sleep Quality Index, and more subjective health complaints than individuals not having SWD. There were no differences between the 2 groups in sleepiness, insomnia, circadian preference, psychological demands, or control. Individuals with SWD reported significantly lower scores on coping. The reports of shift workers without SWD were similar to those of day workers regarding sleep, sleepiness, subjective health complaints, and coping. Conclusions: The prevalence of SWD was relatively high among these shift workers. Individuals with SWD reported poorer sleep quality and more subjective health complaints in the non-work period than shift workers not having SWD. Citation: Waage S; Moen BE; Pallesen S

Coccolithophore assemblage response to Black Sea Water inflow into the North Aegean Sea (NE Mediterranean)

NASA Astrophysics Data System (ADS)

Karatsolis, B.-Th.; Triantaphyllou, M. V.; Dimiza, M. D.; Malinverno, E.; Lagaria, A.; Mara, P.; Archontikis, O.; Psarra, S.

2017-10-01

This study aims to presents the species composition of living coccolithophore communities in the NE Aegean Sea, investigating their spatial and temporal variations along a north-south transect in the area receiving the inflowing surface Black Sea Water (BSW) over the deeper Levantine Water (LW) layer. Coccolithophores in the area were relatively diverse and a total of 95 species over 3 sampling periods studied were recognized using Scanning Electron Microscope (SEM) techniques. R-mode hierarchical cluster analysis distinguished two coccolithophore Groups (I, IIa, IIb, IIc) with different ecological preferences. Emiliania huxleyi was the most abundant species of Group I, whereas Syracosphaera spp., Rhabdosphaera spp. and holococcolithophores were prevailing in the highly diversified Group II assemblages. Biometric analysis conducted on E. huxleyi coccoliths from Aegean water column and Black Sea sediment trap samples, indicated that during autumn, NE Aegean specimens in samples under BSW influence were featured by unimodal distribution concerning the coccolith relative tube width, with values similar to those provided by the Black Sea specimens. In early spring, coccoliths in the stations with increased BSW influx displayed a bimodal pattern of relative tube width with smaller values found mostly in the surface layers, while the distribution became again unimodal and dominated by larger values within the deeper LW layers. In the summer period, the typical LW holococcolithophore species (Group II) presented low cell numbers in the surface layer (<20 m), which is their usual ecological niche in the Aegean Sea, compared to greater depths, therefore marking LW mass flowing beneath the less saline BSW surface lid. In contrast to Black Sea early summer bloom conditions, E. huxleyi was almost absent in the NE Aegean during the summer sampling period.

Long term seismic observation using ocean bottom seismographs in Marmara Sea, Turkey

NASA Astrophysics Data System (ADS)

Takahashi, N.; Pinar, A.; Kalafat, D.; Yamamoto, Y.; Citak, S.; Comoglu, M.; Çok, Ö.; Ogutcu, Z.; Suvarikli, M.; Tunc, S.; Gurbuz, C.; Ozel, N.; Kaneda, Y.

2015-12-01

The North Anatolian Fault crosses the Marmara Sea with a direction of E-W. There are many large earthquakes repeatedly along the fault with a linkage each other. Due to recent large eastern Aegean earthquake with M6, the Marmara Sea is the "blank zone". Japan and Turkey have a SATREPS collaborative study to clarify the structural characters, construct fault models, simulate the strong motion and tsunami, evaluate these risks with hazard maps and educate disaster prevention for local governments and residents. Our activity is one of the most basic studies, and the objectives are to clarify hypocenter locations, monitor the move, and construct fault models referring seismic/magnetotelluric structures, geodetic nature and trenching works. The target area is from western Marmara Sea to the off Istanbul area along the north Anatolian Fault. We deployed ten Ocean Bottom Seismographs (OBSs) between the Tekirdag Basin and the Central Basin in September, 2014. Then, we added five Japanese OBSs and deployed them at the western end of the Marmara Sea and the eastern Central Basin to extend observed area in March, 2015. The OBS has a three-component velocity sensor with a natural frequency of 4.5 Hz and a hydrophone. Japanese team have clarified seismicity around Japan using the OBS. The magnitude of the detected events is 1.0-1.5. We retrieved all 15 OBSs in July, 2015 and deployed them again on the same locations after data copy and battery maintenance. We started OBS data analysis combined with land stations data. Now we detect events automatically using these data and succeeded detection of over one thousand around the north Anatolian Fault. The tentative results show heterogeneous seismicity. The western and central basins have relative high seismicity and the seismogenic zone becomes thicker rather than previous estimation. Then we will evaluate hypocenter locations with high resolution and discuss the shape of faults in each segment and their linkage.

Recent advances in the compilation of holocene relative Sea-level database in North America

NASA Astrophysics Data System (ADS)

Horton, B.; Vacchi, M.; Engelhart, S. E.; Nikitina, D.

2015-12-01

Reconstruction of relative sea level (RSL) has implications for investigation of crustal movements, calibration of earth rheology models and the reconstruction of ice sheets. In recent years, efforts were made to create RSL databases following a standardized methodology. These regional databases provided a framework for developing our understanding of the primary mechanisms of RSL change since the Last Glacial Maximum and a long-term baseline against which to gauge changes in sea-level during the 20th century and forecasts for the 21st. Here we present two quality-controlled Holocene RSL database compiled for North America. Along the Pacific coast of North America (British Columbia, Canada to California, USA), our re-evaluation of sea-level indicators from geological and archaeological investigations yield 841 RSL data-points mainly from salt and freshwater wetlands or adjacent estuarine sediment as well as from isolation basin. Along the Atlantic coast of North America (Hudson Bay, Canada to South Carolina, USA), we are currently compiling a database including more than 2000 RSL data-points from isolation basin, salt and freshwater wetlands, beach ridges and intratidal deposits. We outline the difficulties and solutions we made to compile databases in such different depostional environment. We address complex tectonics and the framework to compare such large variability of RSL data-point. We discuss the implications of our results for the glacio-isostatic adjustment (GIA) models in the two studied regions.

Petrophysical Properties Of Sandy Sediments Possibly Hosting Gas Hydrate In The Eastern Margin Of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Takashima, I.; Sunaga, H.; Sasaki, S.; Matsumoto, R.

2011-12-01

In 2010 the MD179 project was undertaken by the Marion Dufresne aiming at recovery of deep seated gas and gas hydrate, methane induced carbonate, and deep sediments older than 300 ka in order to develop geologic model of gas hydrate accumulation and evaluate the possible environmental impact of gas hydrate for the last glacial-interglacial cycles. Sediment samples below the seafloor were obtained in the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas by the MD179 cruise. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene silty layers, where trace fossils and strong bioturbations are commonly observed. Those sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these arenite sands were undertaken, which indicatesd that porosities of muddy sediments are around 50 % but those of arenites range from 42 to 52 %, of which mean pore sizes and permeabilities are larger than those of siltstones and mudstones. These coarser sediments might have been transported approximately around 3 to 30 ka, where supplying sediments may not be abundant due to sea level fluctuation during the Pleistocene ice age. While the presence of gas hydrate in intergranular pores of arenite sands has not been confirmed, the soupy occurrence in recovered sediments may strongly indicate the presence of gas hydrate filling the intergranular pore system of arenite sands that is called pore-space hydrates. They have been recognized till now in the Mallik as well as in the Nankai Trough areas, which are considered to be very common even in the subsurface sandy sediments at the eastern margin of Japan Sea. Concentration of gas hydrate may need primary intergranular pores large enough to occur within a host sediment that may be arenite sand without matrix grains deposited in the sedimentary

Shipboard determination of radiocesium in seawater after the Fukushima accident: results from the 2011-2012 Russian expeditions to the Sea of Japan and western North Pacific Ocean.

PubMed

Ramzaev, V; Nikitin, A; Sevastyanov, A; Artemiev, G; Bruk, G; Ivanov, S

2014-09-01

A total of 88 seawater samples were collected during two Russian research expeditions (April-May 2011 and August-September 2012) to the Sea of Japan, the Oyashio Current region near Kuril Islands and the Kuroshio-Oyashio transition area in the western North Pacific Ocean. The observations were made aboard the R/V Pavel Gordienko and Akademik Shokalsky in order to study the impact of the Fukushima accident on radioactive contamination of the marine environment. On the board of a ship, the water samples were passed through filters to retain particles with the size of >1 micron. Cesium was extracted from the large volumes (100-3000 L) of the filtrated water using a selective fiber chemisorbent impregnated with copper ferrocyanide. Measurements of (134)Cs and (137)Cs activities in 83 samples of sorbents and 21 samples of filters were performed in the ship-based laboratory with a semiconductor HP-Ge detector. The quantified activity concentrations of dissolved radiocesium ranged from 1 Bq m(-3) to 34 Bq m(-3) for (137)Cs and from 0.2 Bq m(-3) to 29 Bq m(-3) for (134)Cs. Activity concentrations of (137)Cs and (134)Cs were strongly correlated with each other (r = 0.993, n = 59). The (137)Cs/(134)Cs activities ratio in the Fukushima-derived radiocesium inventory for the study areas was deduced to be 0.99 ± 0.03 (on 15 March 2011) and the pre-Fukushima background level of (137)Cs in seawater was estimated as 1.3 ± 0.3 Bq m(-3). The lowest activities of both isotopes were determined in the western part of the Sea of Japan near the Russian coast, while the maximal levels were observed in the open Pacific Ocean, some 500-800 km offshore the Fukushima Dai-ichi Nuclear Power Plant. Contamination with (134)Cs at a level of 0.3-2.6 Bq m(-3) was registered in seawater samples collected in 2011 near the Kuril Islands and Kamchatka in the Oyashio Current region. During the period from April-May 2011 to August-September 2012, activity concentrations of (137)Cs and (134)Cs in surface

An Aquatic Decomposition Scoring Method to Potentially Predict the Postmortem Submersion Interval of Bodies Recovered from the North Sea.

PubMed

van Daalen, Marjolijn A; de Kat, Dorothée S; Oude Grotebevelsborg, Bernice F L; de Leeuwe, Roosje; Warnaar, Jeroen; Oostra, Roelof Jan; M Duijst-Heesters, Wilma L J

2017-03-01

This study aimed to develop an aquatic decomposition scoring (ADS) method and investigated the predictive value of this method in estimating the postmortem submersion interval (PMSI) of bodies recovered from the North Sea. This method, consisting of an ADS item list and a pictorial reference atlas, showed a high interobserver agreement (Krippendorff's alpha ≥ 0.93) and hence proved to be valid. This scoring method was applied to data, collected from closed cases-cases in which the postmortal submersion interval (PMSI) was known-concerning bodies recovered from the North Sea from 1990 to 2013. Thirty-eight cases met the inclusion criteria and were scored by quantifying the observed total aquatic decomposition score (TADS). Statistical analysis demonstrated that TADS accurately predicts the PMSI (p < 0.001), confirming that the decomposition process in the North Sea is strongly correlated to time. © 2017 American Academy of Forensic Sciences.

Man induced change in community control in the north-western Black Sea: The top-down bottom-up balance.

PubMed

Bănaru, Daniela; Harmelin-Vivien, Mireille; Boudouresque, Charles F

2010-05-01

The present study shows how marine commercial fish food webs dramatically changed in the north-western Black Sea on both pelagic and benthic environments. Fisheries landings, diversity and equitability strongly decreased between 1965-1970 and 2001-2005. Fishes adapted their feeding behaviour to the increasingly low species diversity of the Black Sea communities. Their food web became poor and simplified following the loss of many top predator species and their trophic links. Linkage density, connectivity and Lyapunov stability proxy strongly decreased. The north-western Black Sea system switched from a complex top-down and bottom-up functioning pattern to a dominantly bottom-up functioning pattern. This study contributes to a better understanding of these transformations within the Danube-Black Sea system in the last decades. An attempt is made to relate these changes with river inputs, fisheries and coastal pollution. Copyright 2009 Elsevier Ltd. All rights reserved.

Plate convergence and long-term crustal deformation in central Japan

NASA Astrophysics Data System (ADS)

Heki, Kosuke; Miyazaki, Shin'ichi

Surveys by continuous Global Positioning System in and around Japan revealed that the Amurian Plate collides with the North American Plate in central Japan by ∼2 cm/yr. Long-term crustal deformation seems to be influenced mainly by this collision although subduction of oceanic plates governs short-term elastic deformation over the arc. Here we study the long-term deformation field by carefully removing the short-term signals inferred from a-priori plate convergence vectors and coupling strengths predicted by a thermal model. The obtained field shows that the change in velocities occurs along the longitude 135° ∼ 137°, and there exist a relatively rigid block and zones accommodating strains. Characteristic compressional deformation is found northwest of Izu due possibly to the collision of the Izu-Bonin arc with Honshu. Plate convergence rate along the Nankai-Suruga Trough is considerably smaller in eastern parts, due partly to the transition from the Amurian to the North American Plate of the landward side, and partly to the motion of the Izu Microplate relative to the Philippine Sea Plate. This accounts for longer recurrence intervals of interplate earthquakes in the Suruga Trough where the Tokai earthquake is anticipated to occur.

High resolution simulations on the North Aegean Sea seasonal circulation

NASA Astrophysics Data System (ADS)

Kourafalou, V. H.; Barbopoulos, K.

2003-01-01

The seasonal characteristics of the circulation in the North Aegean Sea are examined with the aid of a climatological type simulation (three-year run with perpetual year forcing) on a fine resolution grid (2.5 km by 2.5 km). The model is based on the Princeton Ocean Model with a parameterisation of plume dynamics that is employed for the input of waters with hydrographic properties that are different than the properties of basin waters, as the Black Sea Water (BSW) outflow through the Dardanelles Strait and riverine sources. The model is nested with a sequence of coarser regional and basin-wide models that provide for the long-term interaction between the study area and the Eastern Mediterranean at large. The results are employed to discuss the response of the North Aegean to the important circulation forcing mechanisms in the region, namely wind stress, heat and salt fluxes, buoyancy due to rivers and the BSW outflow (which is low in salinity and occasionally low in temperature) and the interaction with the Southern Aegean. The high resolution allows for the detailed representation of the complicated topography that presides in the region. This helps produce a rich eddy field and it allows for variability in the pathways of BSW that has implications in the basin hydrography and circulation.

Molecular identification of Anisakis and Hysterothylacium larvae in marine fishes from the East China Sea and the Pacific coast of central Japan.

PubMed

Kong, Qingming; Fan, Lanfen; Zhang, Junhe; Akao, Nobuaki; Dong, Kewei; Lou, Di; Ding, Jianzu; Tong, Qunbo; Zheng, Bin; Chen, Rui; Ohta, Nobuo; Lu, Shaohong

2015-04-16

Anisakiasis is a human disease caused by the accidental ingestion of larvae belonging to the family Anisakidae. Three fish species, the small yellow croaker Pseudosciaena polyactis, the mackerel Pneumatophorus japonicus and the hairtail Trichiurus haumela are important source for food products in the East China Sea. The prevalence and the identification of Anisakidae larvae in these fishes will benefit the prevention and control of anisakiasis. In this study, fish samples were obtained from fish markers in the East China Sea and the Pacific coast of central Japan during April 2011 and July 2013. For species identification, the PCR-based restriction fragment length polymorphism (PCR-RFLP) analysis of the entire ITS region (ITS1, 5.8 S and ITS2) of nuclear ribosomal DNA (rDNA) was performed. In total, 2004 larvae were collected from 80 hairtail fish, 20 small yellow croaker, and 27 mackerel from the East China Sea and the Pacific coast of central Japan. High prevalence of Anisakidae larvae infection (116/122, 95.1%) was detected in the East China Sea. Seven species were identified belonging to the genera Anisakis (Nematoda: Anisakidae) and Hysterothylacium (Nematoda: Anisakidae). Anisakis pegreffii was the predominant species accounting for 84.8% of all larvae examined in East China Sea, while all Anisakidae larvae isolated from Japan were identified as Anisakis simplex sensu stricto (s.s.). In the East China Sea, A. simplex s.s. and Anisakis typica were 0.6% (4/619) and 1.5% (9/619) of the identified nematodes, respectively. Interestingly, one larva was identified as a recombinant genotype of A. simplex s.s. and A. pegreffii. In addition, four species of the genus Hysterothylacium, namely, Hysterothylacium amoyense (31/619, 5.0%), Hysterothylacium aduncum (10/619, 1.6%), Hysterothylacium fabri (21/619, 3.4%) and Hysterothylacium spp. (18/619, 2.9%) were also identified in the present study. This is a comprehensive epidemiological dataset for the family Anisakidae in

Modelling climate change effects on benthos: Distributional shifts in the North Sea from 2001 to 2099

NASA Astrophysics Data System (ADS)

Weinert, Michael; Mathis, Moritz; Kröncke, Ingrid; Neumann, Hermann; Pohlmann, Thomas; Reiss, Henning

2016-06-01

In the marine realm, climate change can affect a variety of physico-chemical properties with wide-ranging biological effects, but the knowledge of how climate change affects benthic distributions is limited and mainly restricted to coastal environments. To project the response of benthic species of a shelf sea (North Sea) to the expected climate change, the distributions of 75 marine benthic species were modelled and the spatial changes in distribution were projected for 2099 based on modelled bottom temperature and salinity changes using the IPCC scenario A1B. Mean bottom temperature was projected to increase between 0.15 and 5.4 °C, while mean bottom salinity was projected to moderately increase by 1.7. The spatial changes in species distribution were modelled with Maxent and the direction and extent of these changes were assessed. The results showed a latitudinal northward shift for 64% of the species (maximum 109 km; brittle star Ophiothrix fragilis) and a southward shift for 36% (maximum 101 km; hermit crab Pagurus prideaux and the associated cloak anemone Adamsia carciniopados; 105 km). The relatively low rates of distributional shifts compared to fish or plankton species were probably influenced by the regional topography. The environmental gradients in the central North Sea along the 50 m depth contour might act as a 'barrier', possibly resulting in a compression of distribution range and hampering further shifts to the north. For 49 species this resulted in a habitat loss up to 100%, while only 11 species could benefit from the warming in terms of habitat gain. Particularly the benthic communities of the southern North Sea, where the strongest temperature increase was projected, would be strongly affected by the distributional changes, since key species showed northward shifts and high rates of habitat loss, with potential ramifications for the functioning of the ecosystem.

The impact of shipping emissions on air pollution in the greater North Sea region - Part 1: Current emissions and concentrations

NASA Astrophysics Data System (ADS)

Aulinger, A.; Matthias, V.; Zeretzke, M.; Bieser, J.; Quante, M.; Backes, A.

2016-01-01

The North Sea is one of the areas with the highest ship traffic densities worldwide. At any time, about 3000 ships are sailing its waterways. Previous scientific publications have shown that ships contribute significantly to atmospheric concentrations of NOx, particulate matter and ozone. Especially in the case of particulate matter and ozone, this influence can even be seen in regions far away from the main shipping routes. In order to quantify the effects of North Sea shipping on air quality in its bordering states, it is essential to determine the emissions from shipping as accurately as possible. Within Interreg IVb project Clean North Sea Shipping (CNSS), a bottom-up approach was developed and used to thoroughly compile such an emission inventory for 2011 that served as the base year for the current emission situation. The innovative aspect of this approach was to use load-dependent functions to calculate emissions from the ships' current activities instead of averaged emission factors for the entire range of the engine loads. These functions were applied to ship activities that were derived from hourly records of Automatic Identification System signals together with a database containing the engine characteristics of the vessels that traveled the North Sea in 2011. The emission model yielded ship emissions among others of NOx and SO2 at high temporal and spatial resolution that were subsequently used in a chemistry transport model in order to simulate the impact of the emissions on pollutant concentration levels. The total emissions of nitrogen reached 540 Gg and those of sulfur oxides 123 Gg within the North Sea - including the adjacent western part of the Baltic Sea until 5° W. This was about twice as much of those of a medium-sized industrialized European state like the Netherlands. The relative contribution of ships to, for example, NO2 concentration levels ashore close to the sea can reach up to 25 % in summer and 15 % in winter. Some hundred kilometers

Climatic forcing of Quaternary deep-sea benthic communities in the North Pacific Ocean

USGS Publications Warehouse

Yasuhara, Moriaki; Hunt, G.; Cronin, T. M.; Hokanishi, N.; Kawahata, H.; Tsujimoto, Akira; Ishitake, M.

2012-01-01

There is growing evidence that changes in deep-sea benthic ecosystems are modulated by climate changes, but most evidence to date comes from the North Atlantic Ocean. Here we analyze new ostracod and published foraminiferal records for the last 250,000 years on Shatsky Rise in the North Pacific Ocean. Using linear models, we evaluate statistically the ability of environmental drivers (temperature, productivity, and seasonality of productivity) to predict changes in faunal diversity, abundance, and composition. These microfossil data show glacial-interglacial shifts in overall abundances and species diversities that are low during glacial intervals and high during interglacials. These patterns replicate those previously documented in the North Atlantic Ocean, suggesting that the climatic forcing of the deep-sea ecosystem is widespread, and possibly global in nature. However, these results also reveal differences with prior studies that probably reflect the isolated nature of Shatsky Rise as a remote oceanic plateau. Ostracod assemblages on Shatsky Rise are highly endemic but of low diversity, consistent with the limited dispersal potential of these animals. Benthic foraminifera, by contrast, have much greater dispersal ability and their assemblages at Shatsky Rise show diversities typical for deep-sea faunas in other regions. Statistical analyses also reveal ostracod-foraminferal differences in relationships between environmental drivers and biotic change. Rarefied diversity is best explained as a hump-shaped function of surface productivity in ostracods, but as having a weak and positive relationship with temperature in foraminifera. Abundance shows a positive relationship with both productivity and seasonality of productivity in foraminifera, and a hump-shaped relationship with productivity in ostracods. Finally, species composition in ostracods is influenced by both temperature and productivity, but only a temperature effect is evident in foraminifera. Though

Mapping the spawning grounds of North Sea cod (Gadus morhua) by direct and indirect means.

PubMed

Fox, Clive J; Taylor, Martin; Dickey-Collas, Mark; Fossum, Petter; Kraus, Gerd; Rohlf, Norbert; Munk, Peter; van Damme, Cindy J G; Bolle, Loes J; Maxwell, David L; Wright, Peter J

2008-07-07

Despite recent evidence for sub-stock structuring, North Sea cod are assessed as a single unit. As a consequence, knowledge of sub-stock trends is poor. In particular, there are no recent evaluations of which spawning grounds are active. Here we report results from the first ichthyoplankton survey to cover the whole North Sea. Also, this survey, conducted in 2004, was the first to make extensive use of DNA-based molecular methods to unambiguously identify early developmental stage cod eggs. We compare the findings from the plankton survey with estimated egg production inferred from the distribution of mature cod in contemporaneous trawl surveys. Results from both approaches were in general agreement and showed hot spots of egg production around the southern and eastern edges of the Dogger Bank, in the German Bight, the Moray Firth and to the east of the Shetlands. These areas broadly coincide with known spawning locations from the period 1940 to 1970. We were, however, unable to directly detect significant numbers of cod eggs at the historic spawning ground off Flamborough (northeast coast of England). The results demonstrate that most of the major spawning grounds of cod in the North Sea are still active but that some localized populations may have been reduced to the point where it is now difficult to detect the presence of eggs in the plankton.

Mapping the spawning grounds of North Sea cod (Gadus morhua) by direct and indirect means

PubMed Central

Fox, Clive J; Taylor, Martin; Dickey-Collas, Mark; Fossum, Petter; Kraus, Gerd; Rohlf, Norbert; Munk, Peter; van Damme, Cindy J.G; Bolle, Loes J; Maxwell, David L; Wright, Peter J

2008-01-01

Despite recent evidence for sub-stock structuring, North Sea cod are assessed as a single unit. As a consequence, knowledge of sub-stock trends is poor. In particular, there are no recent evaluations of which spawning grounds are active. Here we report results from the first ichthyoplankton survey to cover the whole North Sea. Also, this survey, conducted in 2004, was the first to make extensive use of DNA-based molecular methods to unambiguously identify early developmental stage cod eggs. We compare the findings from the plankton survey with estimated egg production inferred from the distribution of mature cod in contemporaneous trawl surveys. Results from both approaches were in general agreement and showed hot spots of egg production around the southern and eastern edges of the Dogger Bank, in the German Bight, the Moray Firth and to the east of the Shetlands. These areas broadly coincide with known spawning locations from the period 1940 to 1970. We were, however, unable to directly detect significant numbers of cod eggs at the historic spawning ground off Flamborough (northeast coast of England). The results demonstrate that most of the major spawning grounds of cod in the North Sea are still active but that some localized populations may have been reduced to the point where it is now difficult to detect the presence of eggs in the plankton. PMID:18397869

New insights into the earliest Quaternary environments in the Central North Sea from 3D seismic

NASA Astrophysics Data System (ADS)

Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

2014-05-01

In the past the transition between an unconformable surface in the south to a conformable horizon towards the north has made identification and mapping the base-Quaternary in the central North Sea difficult (Sejrup et al 1991; Gatliff et al 1994). However recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) has allowed greater confidence in the correlation to the region 3D seismic datasets and thus has allowed the base-Quaternary to be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The revised base-Quaternary surface reaches a depth of 1248 ms TWT with an elongate basin shape which is significantly deeper than the traditionally mapped surface. Using RMS amplitudes and other seismic attributes the revised base-Quaternary has been investigated along the horizon and in time slice to interpret the environments of the earliest Quaternary prior to the onset of glaciation. Combined with analysis of aligned elongate furrows over 10 km long, 100 m wide and 100 m deep suggest a deep marine environment in an almost enclosed basin with persistent strong NW-SE bottom currents in the deepest parts. Pockmarks were formed by the escape of shallow gas on the sides of a small delta in the eastern part of the basin. The progradation of large deltas from both the north and south into the basin make up the majority of the deposition of sediment into the basin. Key Words: base-Quaternary; seismic interpretation; paleoenvironments References: Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional

Variability in Organic-Carbon Sources and Sea-Ice Coverage North of Iceland (Subarctic) During the Past 15,000 Years

NASA Astrophysics Data System (ADS)

Xiao, X.; Zhao, M.; Knudsen, K. L.; Eiriksson, J.; Gudmundsdottir, E. R.; Jiang, H.; Guo, Z.

2017-12-01

Sea ice, prevailing in the polar region and characterized by distinct seasonal and interannual variability, plays a pivotal role in Earth's climate system (Thomas and Dieckmann, 2010). Studies of spatial and temporal changes in modern and past sea-ice occurrence may help to understand the processes controlling the recent decrease in Arctic sea-ice cover. Here, we determined the concentrations of sea-ice diatom-derived biomarker "IP25" (monoene highly-branched isoprenoid with 25 carbon atom; Belt et al., 2007), phytoplankton-derived biomarker brassicasterol and terrigenous biomarker long-chain n-alkanols in a sediment core from the North Icelandic shelf to reconstruct the high-resolution sea-ice variability and the organic-matter sources during the past 15,000 years. During the Bølling/Allerød, the North Icelandic shelf was characterized by extensive spring sea-ice cover linked to reduced flow of warm Atlantic Water and dominant Polar water influence; the input of terrestrial and sea-ice organic matters was high while the marine organic matter derived from phytoplankton productivity was low. Prolonged sea-ice cover with occasional occurrence of seasonal sea ice prevailed during the Younger Dryas interrupted by a brief interval of enhanced Irminger Current; the organic carbon input from sea-ice productivity, terrestrial matter and phytoplankton productivity all decreased. The seasonal sea ice decreased gradually from the Younger Dryas to the onset of the Holocene corresponding to increasing insolation. Therefore, the sea-ice productivity decreased but the phytoplankton productivity increased during this time interval. The biomarker records from this sediment core give insights into the variability in sea ice and organic-carbon sources in the Arctic marginal area during the last deglacial and Holocene. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Org. Geochem. 38, 16

A novel marine nitrite-oxidizing Nitrospira species from Dutch coastal North Sea water

PubMed Central

Haaijer, Suzanne C. M.; Ji, Ke; van Niftrik, Laura; Hoischen, Alexander; Speth, Daan; Jetten, Mike S. M.; Damsté, Jaap S. Sinninghe; Op den Camp, Huub J. M.

2013-01-01

Marine microorganisms are important for the global nitrogen cycle, but marine nitrifiers, especially aerobic nitrite oxidizers, remain largely unexplored. To increase the number of cultured representatives of marine nitrite-oxidizing bacteria (NOB), a bioreactor cultivation approach was adopted to first enrich nitrifiers and ultimately nitrite oxidizers from Dutch coastal North Sea water. With solely ammonia as the substrate an active nitrifying community consisting of novel marine Nitrosomonas aerobic ammonia oxidizers (ammonia-oxidizing bacteria) and Nitrospina and Nitrospira NOB was obtained which converted a maximum of 2 mmol of ammonia per liter per day. Switching the feed of the culture to nitrite as a sole substrate resulted in a Nitrospira NOB dominated community (approximately 80% of the total microbial community based on fluorescence in situ hybridization and metagenomic data) converting a maximum of 3 mmol of nitrite per liter per day. Phylogenetic analyses based on the 16S rRNA gene indicated that the Nitrospira enriched from the North Sea is a novel Nitrospira species with Nitrospira marina as the next taxonomically described relative (94% 16S rRNA sequence identity). Transmission electron microscopy analysis revealed a cell plan typical for Nitrospira species. The cytoplasm contained electron light particles that might represent glycogen storage. A large periplasmic space was present which was filled with electron dense particles. Nitrospira-targeted polymerase chain reaction analyses demonstrated the presence of the enriched Nitrospira species in a time series of North Sea genomic DNA samples. The availability of this new Nitrospira species enrichment culture facilitates further in-depth studies such as determination of physiological constraints, and comparison to other NOB species. PMID:23515432

Assimilating NOAA SST data into BSH operational circulation model for North and Baltic Seas

NASA Astrophysics Data System (ADS)

Losa, Svetlana; Schroeter, Jens; Nerger, Lars; Janjic, Tijana; Danilov, Sergey; Janssen, Frank

A data assimilation (DA) system is developed for BSH operational circulation model in order to improve forecast of current velocities, sea surface height, temperature and salinity in the North and Baltic Seas. Assimilated data are NOAA sea surface temperature (SST) data for the following period: 01.10.07 -30.09.08. All data assimilation experiments are based on im-plementation of one of the so-called statistical DA methods -Singular Evolutive Interpolated Kalman (SEIK) filter, -with different ways of prescribing assumed model and data errors statis-tics. Results of the experiments will be shown and compared against each other. Hydrographic data from MARNET stations and sea level at series of tide gauges are used as independent information to validate the data assimilation system. Keywords: Operational Oceanography and forecasting

The shear-wave splitting in the crust and the upper mantle around the Bohai Sea, North China

NASA Astrophysics Data System (ADS)

Yutao, Shi; Yuan, Gao; Lingxue, Tai; Yuanyuan, Fu

2015-11-01

In order to infer the distribution of local stress and the deep geodynamic process in North China, this study detects seismic anisotropy in the crust and upper mantle beneath the Bohai Sea area. A total of 535 local shear-wave and 721 XKS (including SKS, PKS and SKKS phases) splitting measurements were obtained from stations in permanent regional seismograph networks and a temporary seismic network called ZBnet-E. The dominant fast polarization orientation of local shear-waves in the crust is nearly East-West, suggesting an East-West direction of local maximum compressive stress in the area. Nearly North-South fast orientation was obtained at some stations in the Tan-Lu fault belt and the Zhang-Bo seismic belt. The average fast orientation from XKS splitting analysis is 87.4° measured clockwise from the North. The average time-delays of XKS splitting are range from 0.54 s to 1.92 s, corresponding to a 60-210 km thick layer of anisotropy. The measured results indicate that upper mantle anisotropy beneath Bohai Sea area, even the eastern part of North China, is mainly from asthenospheric mantle flow from the subduction of the Pacific plate. From the complicated anisotropic characteristics in this study, we infer that there might be multiple mechanisms in the crust and upper mantle around the Bohai Sea area that led to the observed anisotropy.

Toward a Regional Triad -- The Nature of Future US Strategic Engagement in the South China Sea

DTIC Science & Technology

2012-12-14

generally focused on Japan and the Republic of Korea (ROK) in the north . The East Sea Fleet, focused upon Taiwan in the center, is homeported at...Singapore, Thailand, Brunei, Burma ( Myanmar ), Cambodia, Laos, and Vietnam. 30Colloquially, “the ASEAN Way”--their charter stresses the non...United States Department of Defense Foreign Military Sales Program INF Intermediate-Range Nuclear Forces Treaty MEU U.S. Marine Expeditionary Unit

Long-term decrease in phosphate concentrations in the surface layer of the southern Japan Sea

NASA Astrophysics Data System (ADS)

Kodama, Taketoshi; Igeta, Yosuke; Kuga, Mizuki; Abe, Shoko

2016-10-01

To identify possible causes for the long-term trends in nutrient concentrations in the southern Japan Sea (JS), we studied nutrient concentrations that were obtained by the Japan Meteorological Agency. Our evaluation shows that phosphate concentrations declined in the surface layers in summer (0-20 and 21-50 m depth) and winter (0-20, 21-50, and 51-100 m depth) over the last 40 years, while no significant linear trend was observed for nitrate concentrations. The declining trend in the phosphate concentration was quantified as 1.8-3.3 nM yr-1. The increase in atmospheric nutrient deposition to the JS could not explain the decline in phosphate concentration. In addition, the mixed-layer depth during winter did not demonstrate any significant trend, and an increase in phosphate concentrations was not observed in any layers; therefore, the decrease in nutrient supply from deep JS water was not considered a major possible cause for the decline in the phosphate concentration. In contrast, the phosphate concentration in the surface of the southern JS during winter showed a significant positive correlation with the concentration in the 21-50 m depth layer of the saline East China Sea (ECS) water in the preceding summer, and the surface water of the southern JS was almost entirely replaced by water originating from the ECS during May-October. Therefore, it is concluded that the declining trend in the phosphate concentrations in the southern JS is caused by horizontal advection of ECS water.

Seasonal and interannual variation of physical and biological processes during 1994-2001 in the Sea of Japan/East Sea: A three-dimensional physical-biogeochemical modeling study

NASA Astrophysics Data System (ADS)

Liu, Guimei; Chai, Fei

2009-09-01

A Pacific basin-wide physical-biogeochemical model has been used to investigate the seasonal and interannual variation of physical and biological fields with analyses focusing on the Sea of Japan/East Sea (JES). The physical model is based on the Regional Ocean Model System (ROMS), and the biogeochemical model is based on the Carb on, Si(OH) 4, Nitrogen Ecosystem (CoSiNE) model. The coupled ROMS-CoSiNE model is forced with the daily air-sea fluxes derived from the National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) reanalysis for the period of 1994 to 2001, and the model results are used to evaluate climate impact on nutrient transport in Mixed Layer Depth (MLD) and phytoplankton spring bloom dynamics in the JES. The model reproduces several key features of sea surface temperature (SST) and surface currents, which are consistent with the previous modeling and observational results in the JES. The calculated volume transports through the three major straits show that the Korea Strait (KS) dominates the inflow to the JES with 2.46 Sv annually, and the Tsugaru Strait (TS) and the Soya Strait (SS) are major outflows with 1.85 Sv and 0.64 Sv, respectively. Domain-averaged phytoplankton biomass in the JES reaches its spring peak 1.8 mmol N m - 3 in May and shows a relatively weak autumn increase in November. Strong summer stratification and intense consumption of nitrate by phytoplankton during the spring result in very low nitrate concentration at the upper layer, which limits phytoplankton growth in the JES during the summer. On the other hand, the higher grazer abundance likely contributes to the strong suppression of phytoplankton biomass after the spring bloom in the JES. The model results show strong interannual variability of SST, nutrients, and phytoplankton biomass with sudden changes in 1998, which correspond to large-scale changes of the Pacific Decadal Oscillation (PDO). Regional comparisons of

Effect of DGPS failures on dynamic positioning of mobile drilling units in the North Sea.

PubMed

Chen, Haibo; Moan, Torgeir; Verhoeven, Harry

2009-11-01

Basic features of differential global positioning system (DGPS), and its operational configuration on dynamically positioned (DP) mobile offshore drilling units in the North Sea are described. Generic failure modes of DGPS are discussed, and a critical DGPS failure which has the potential to cause drive-off for mobile drilling units is identified. It is the simultaneous erroneous position data from two DGPS's. Barrier method is used to analyze this critical DGPS failure. Barrier elements to prevent this failure are identified. Deficiencies of each barrier element are revealed based on the incidents and operational experiences in the North Sea. Recommendations to strengthen these barrier elements, i.e. to prevent erroneous position data from DGPS, are proposed. These recommendations contribute to the safety of DP operations of mobile offshore drilling units.

North Atlantic teleconnection patterns signature on sea level from satellite altimetry

NASA Astrophysics Data System (ADS)

Iglesias, Isabel; Lázaro, Clara; Joana Fernandes, M.; Bastos, Luísa

2015-04-01

Presently, satellite altimetry record is long enough to appropriately study inter-annual signals in sea level anomaly and ocean surface circulation, allowing the association of teleconnection patterns of low-frequency variability with the response of sea level. The variability of the Atlantic Ocean at basin-scale is known to be complex in space and time, with the dominant mode occurring on annual timescales. However, interannual and decadal variability have already been documented in sea surface temperature. Both modes are believed to be linked and are known to influence sea level along coastal regions. The analysis of the sea level multiannual variability is thus essential to understand the present climate and its long-term variability. While in the open-ocean sea level anomaly from satellite altimetry currently possesses centimetre-level accuracy, satellite altimetry measurements become invalid or of lower accuracy along the coast due to the invalidity of the wet tropospheric correction (WTC) derived from on-board microwave radiometers. In order to adequately analyse long-term changes in sea level in the coastal regions, satellite altimetry measurements can be recovered by using an improved WTC computed from recent algorithms that combine wet path delays from all available observations (remote sensing scanning imaging radiometers, GNSS stations, microwave radiometers on-board satellite altimetry missions and numerical weather models). In this study, a 20-year (1993-2013) time series of multi-mission satellite altimetry (TOPEX/Poseidon, Jason-1, OSTM/Jason-2, ERS-1/2, ENVISAT, CryoSat-2 and SARAL), are used to characterize the North Atlantic (NA) long-term variability on sea level at basin-scale and analyse its response to several atmospheric teleconnections known to operate on the NA. The altimetry record was generated using an improved coastal WTC computed from either the GNSS-derived path Delay or the Data Combination methodologies developed by University of

The influence of riverine nitrogen on the dynamics of the North Sea oxygen minimum zone

NASA Astrophysics Data System (ADS)

Große, Fabian; Kreus, Markus; Lenhart, Hermann; Pätsch, Johannes

2016-04-01

The mitigation of eutrophication and its concomitants, like oxygen deficiency in bottom waters, is one of the major aspects of the ecological management of coastal marine ecosystems. In the past, biogeochemical models helped to significantly improve the understanding of the interaction of the physical and biological processes driving eutrophication. Anthropogenic river input of nitrogen (N) and phosphorus (P) is the main driver for eutrophication. Nevertheless, the quantification of their influence in a specific region remains an important issue, since it is as crucial for an efficient management as it is difficult to obtain. During the past decade, a quantitative method applicable to biogeochemical models - often referred to as `trans-boundary nutrient transports' (TBNT) - became more and more popular in the context of marine ecosystem management. This method allows for the tracing of elements from various sources, e.g., nitrogen (N) from different rivers, throughout the whole process chain of the applied model. By this, it provides valuable information about the contributions from different sources to the overall amount and turnover of an element in different areas of the model domain. This information constitutes the basis for the quantification, evaluation and optimisation of river input reduction targets for the tributaries, which are defined in relation to their ecological consequences in the marine environment. In existing studies, the TBNT method has been applied to a variety of biogeochemical models, e.g. to quantify the atmospheric contribution to total N in the North Sea (Troost et al., 2013). This study presents a novel approach to link the TBNT method applied to N to the biological processes driving the oxygen dynamics in the bottom layer of the North Sea. For this purpose, simulations from the biogeochemical model ECOHAM (ECOlogical model HAMburg) are analysed for the years 2002 and 2010, with the focus on the southern central North Sea, the region of

Phylogenetic diversity of Flavobacteria isolated from the North Sea on solid media.

PubMed

Hahnke, Richard L; Harder, Jens

2013-10-01

Flavobacteria are abundant in the North Sea, an epeiric sea on the continental shelf of Europe. However, this abundance has so far not been reflected by the number of strains in culture collections. In this study, Flavobacteria were isolated from pelagic and benthic samples, such as seawater, phytoplankton, sediment and its porewater, and from surfaces of animals and seaweeds on agar plates with a variety of carbon sources. Dilution cultivation with a new medium, incubation at low temperatures and with long incubation times, and colony screening by a Flavobacteria-Cytophagia-specific PCR detecting 16S rRNA gene sequences led to a collection of phylogenetically diverse strains. Two strains affiliated with Flammeovirgaceae and seven strains affiliated with Cyclobacteriaceae, whereas within the Flavobacteriaceae 20 isolated strains presumably represented seven novel candidate genera and 355 strains affiliated with 26 of 80 validly described marine Flavobacteriaceae genera, based on a genus boundary of 95.0% 16S rRNA gene sequence identity. The majority of strains (276) affiliated with 37 known species in 16 genera (based on a boundary of 98.7% 16S rRNA gene sequence identity), whereas 79 strains likely represented 42 novel species in 22 established Flavobacteriaceae genera. Pigmentation, iridescence, gliding motility, agar lysis, and flexirubin as a chemical marker supported the taxonomy at the species level. This study demonstrated the culturability on solid medium of phylogenetically diverse Flavobacteria originating from the North Sea. Copyright © 2013 Elsevier GmbH. All rights reserved.

Dissolved organic nitrogen dynamics in the North Sea: A time series analysis (1995-2005)

NASA Astrophysics Data System (ADS)

Van Engeland, T.; Soetaert, K.; Knuijt, A.; Laane, R. W. P. M.; Middelburg, J. J.

2010-09-01

Dissolved organic nitrogen (DON) dynamics in the North Sea was explored by means of long-term time series of nitrogen parameters from the Dutch national monitoring program. Generally, the data quality was good with little missing data points. Different imputation methods were used to verify the robustness of the patterns against these missing data. No long-term trends in DON concentrations were found over the sampling period (1995-2005). Inter-annual variability in the different time series showed both common and station-specific behavior. The stations could be divided into two regions, based on absolute concentrations and the dominant times scales of variability. Average DON concentrations were 11 μmol l -1 in the coastal region and 5 μmol l -1 in the open sea. Organic fractions of total dissolved nitrogen (TDN) averaged 38 and 71% in the coastal zone and open sea, respectively, but increased over time due to decreasing dissolved inorganic nitrogen (DIN) concentrations. In both regions intra-annual variability dominated over inter-annual variability, but DON variation in the open sea was markedly shifted towards shorter time scales relative to coastal stations. In the coastal zone a consistent seasonal DON cycle existed with high values in spring-summer and low values in autumn-winter. In the open sea seasonality was weak. A marked shift in the seasonality was found at the Dogger Bank, with DON accumulation towards summer and low values in winter prior to 1999, and accumulation in spring and decline throughout summer after 1999. This study clearly shows that DON is a dynamic actor in the North Sea and should be monitored systematically to enable us to understand fully the functioning of this ecosystem.

Field survey of trans-boundary air pollution with high time resolution at coastal sites on the Sea of Japan during winter in Japan.

PubMed

Aikawa, Masahide; Hiraki, Takatoshi; Tamaki, Motonori; Kasahara, Mikio; Kondo, Akira; Uno, Itsushi; Mukai, Hitoshi; Shimizu, Atsushi; Murano, Kentaro

2006-11-01

An intensive field survey, with 6-h measurement intervals, of concentrations of chemical species in particulate matter and gaseous compounds was carried out at coastal sites on the Sea of Japan during winter. The concentration variation of SO(2)(g) and HNO(3)(g) were well correlated, whereas the NH(3)(g) concentration variation had no correlation with those of SO(2)(g) and HNO(3)(g). The NH(4) (+) (p)/non-sea-salt- (nss-)SO(4) (2 -)(p) ratio in particulate matter was mainly affected by the location of the sampling site. One or more concentration peaks of nss-Ca(2 +) for survey period were observed. Backward trajectories analyses for the highest nss-Ca(2 +) concentration peaks showed some inconsistency in pathways. We consider that insufficient mixing of the atmosphere and/or insufficient time for the transported air pollutants to react with those discharged locally are the most likely explanations for the discrepancies between the measured products [HNO(3)][NH(3)] and the calculated values.

Teleconnection between sea ice in the Barents Sea in June and the Silk Road, Pacific-Japan and East Asian rainfall patterns in August

NASA Astrophysics Data System (ADS)

He, Shengping; Gao, Yongqi; Furevik, Tore; Wang, Huijun; Li, Fei

2018-01-01

In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes. Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east-west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific-Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.

Teleconnection between Sea Ice in the Barents Sea in June and the Silk Road, Pacific-Japan and East Asian Rainfall Patterns in August

NASA Astrophysics Data System (ADS)

He, S.; Gao, Y.; Furevik, T.; Huijun, W.; Li, F.

2017-12-01

In contrast to previous studies that have tended to focus on the influence of the total Arctic sea-ice cover on the East Asian summer tripole rainfall pattern, the present study identifies the Barents Sea as the key region where the June sea-ice variability exerts the most significant impacts on the East Asian August tripole rainfall pattern, and explores the teleconnection mechanisms involved. The results reveal that a reduction in June sea ice excites anomalous upward air motion due to strong near-surface thermal forcing, which further triggers a meridional overturning wave-like pattern extending to midlatitudes. Anomalous downward motion therefore forms over the Caspian Sea, which in turn induces zonally oriented overturning circulation along the subtropical jet stream, exhibiting the east-west Rossby wave train known as the Silk Road pattern. It is suggested that the Bonin high, a subtropical anticyclone predominant near South Korea, shows a significant anomaly due to the eastward extension of the Silk Road pattern to East Asia. As a possible descending branch of the Hadley cell, the Bonin high anomaly ultimately triggers a meridional overturning, establishing the Pacific-Japan pattern. This in turn induces an anomalous anticyclone and cyclone pair over East Asia, and a tripole vertical convection anomaly meridionally oriented over East Asia. Consequently, a tripole rainfall anomaly pattern is observed over East Asia. Results from numerical experiments using version 5 of the Community Atmosphere Model support the interpretation of this chain of events.

Transboundary transport of anthropogenic sulfur in PM2.5 at a coastal site in the Sea of Japan as studied by sulfur isotopic ratio measurement.

PubMed

Inomata, Yayoi; Ohizumi, Tsuyoshi; Take, Naoko; Sato, Keiichi; Nishikawa, Masataka

2016-05-15

Sulfur isotopic ratios (δ(34)S) in size separated aerosol particles (PM2.5 and coarse particles) were measured at Niigata-Maki facing the Sea of Japan. Non-sea salt δ(34)S (δ(34)Snss) in PM2.5 showed seasonal variations with relatively high values in winter (1.0-3.9‰ in spring, 2.8-4.5‰ in summer, 1.3-4.5‰ in autumn, 3.7-5.7‰ in winter). Taking into consideration air mass transport routes, δ(34)Snss in the air masses which originated in the Asian continent and were transported over the Sea of Japan to the monitoring sites were higher than those values for air masses which were transported over the Japanese islands after leaving the Asian continent for each season. Considering that the δ(34)Snss in sulfuric acid derived from domestic emissions in Japan are lower than those of δ(34)Snss in coal, the lower δ(34)Snss for the air mass transported over the Japanese islands suggest that sulfuric acid in PM2.5 modified the δ(34)Snss due to aerosol mixing with sulfuric acid in Japan. Material balance calculations suggested that the relative contribution of transboundary transport in winter was also higher than for other seasons (40-75% in spring, 51-63% in summer, 45-73% in autumn, and 53-81% in winter). In particular, the contribution to the air masses which were transported directly from the Asian continent was relatively large (75% in spring, 59% in autumn, 78% in winter) in comparison with that for the air masses which were transported over Japan. Copyright © 2016 Elsevier B.V. All rights reserved.

Multi-decadal storminess fluctuations of Black Sea due to North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Kuznetsov, Sergey; Saprykina, Yana; Grigorieva, Victoria; Aydoǧan, Berna; Aydoǧan, Burak

2017-04-01

Storminess variability is of key importance for many marine applications, naval and coastal engineering. Studying the evolution of this phenomenon along with large scale atmospheric patterns and being able to predict them is crucial for in the context of rising sea level due to climate change what make the low-lying coasts in the Black Sea to become increasingly vulnerable to marine hazards. The aim of this work is to clarify the trends, statistics and reasons of variations of storminess in dependence of such climatic characteristic as NAO (North Atlantic Oscillation Index). The analysis of Black Sea storminess activity was performed on the base of visual wave observations (Voluntary Observing Ship or VOS) for the period 1970-2011. Annual means and maximum heights of wind-driven seas and swell waves averaging over whole Black Sea area were investigated separately. The both wind-driven seas and swell demonstrate the decreasing in heights about 10% the same as their periods for the chosen time frame. Parametric spectral analysis was performed. The periods of wave height fluctuations for wind-driven seas and swell were shown to coincide with each other and with periods of low frequency fluctuation of NOA: 14 and 4 year respectively. Correlation coefficients of wave height and NOA were 0.3 for swell and 0.4 for wind-driven sea. Nonlinear regularities of NAO fluctuations were investigated using wavelet and spavlet (spectra of modules of wavelet coefficients) analyses. Their influence on variability of storminess in Black Sea is discussed. The reported study was funded by RFBR (project No. 16-55-76002 ERA_a) and by TUBITAK (project No. 116M061) in frame of BS STEMA project.

Thick massive gas hydrate deposits were revealed by LWD in Off-Joetsu area, eastern margin of Japan Sea.

NASA Astrophysics Data System (ADS)

Tanahashi, M.; Morita, S.; Matsumoto, R.

2016-12-01

GR14 and HR15 survey cruises, which were dedicated to the LWD (Logging While Drilling), were carried out in summers of 2014 and 2015, respectively, by Meiji University and Geological Survey of Japan, AIST to explore the "gas chimney" structures in eastern margin of Japan Sea. Shallow (33 to 172m-bsf, average 136m-bsf) 33 LWD drilling were performed in Oki Trough, Off-Joetsu, and Mogami Trough areas along eastern margin of Japan Sea during two cruises. Schlumberger LWD tools, GeoVISION (resistivity), TeleScope, ProVISION (NMR) and SonicVISION were used during GR14. NeoScope (neutron) was added and SonicScope was replaced for SonicVISION during HR14. The data quality was generally good. "Gas chimney" structures with acoustic blanking columns on the high frequency seismic sections with mound and pockmark morphologic features on the sea bottom, are well developed within survey areas. Every LWD records taken from gas chimney structures during the cruises show high resistivity and acoustic velocity anomalies which suggest the development of gas hydrate. Characteristic development of massive gas hydrate was interpreted at the Umitaka CW mound structure, Off-Joetsu. The mound lies at 890-910m in water depth and has very rough bottom surface, regional high resistivity, regional high heat flow, several natural seep sites, 200m x 300m area, and 10-20m height. 8 LWD holes, J18L to J21L and J23L to J26L, were drilled on and around the mound. There are highly anomalous intervals which suggest the development of massive gas hydrate at J24L, with high resistivity, high Vp and Vs, high neutron porosity, low natural gamma ray intensity, low neutron gamma density, low NMR porosity, low NMR permeability, low formation sigma, from 10 to 110m-bsf with intercalating some thin less hydrate layers. It is interpreted that there is several tens of meter thick massive gas hydrate in the gas chimney mound. It is partly confirmed by the later nearby coring result which showed the repetition of

Heinrich events and sea level changes: records from uplifted coral terraces and marginal seas

NASA Astrophysics Data System (ADS)

Yokoyama, Y.; Esat, T. M.; Suga, H.; Obrochta, S.; Ohkouchi, N.

2017-12-01

Repeated major ice discharge events spaced every ca.7,000 years during the last ice age was first detected in deep sea sediments from North Atlantic. Characterized as lithic layers, these Heinrich Events (Heinrich, 1988 QR) correspond to rapid climate changes attributed to weakened ocean circulation (eg., Broecker, 1994 Nature; Alley, 1998 Nature) as shown by a number of different proxies. A better understanding of the overall picture of Heinrich events would benefit from determining the total amount of ice involved each event, which is still under debate. Sea level records are the most direct means for that, and uranium series dated corals can constrain the timing precisely. However, averaged global sea level during the time of interest was around -70m, hindering study from tectonically stable regions. Using uplifted coral terraces that extend 80 km along the Huon Peninsula, Papua New Guinea, the magnitude of sea level change during Heinrich Events was successfully reconstructed (Yokoyama et al., 2001 EPSL; Chappell et al., 1996 EPSL; Cutler et al., 2003). The H3 and H5 events are also well correlated with continuous sea level reconstructions using Red Sea oxygen isotope records (Siddall et al., 2003 Nature; Yokoyama and Esat, 2011Oceanography). Global ice sheet growth after 30 ka complicates interpretation of the Huon Peninsula record. However oxygen isotope data from the Japan Sea, a restricted margin sea with a shallow sill depth similar to the Red Sea, clearly captures the episode of H2 sea level change. The timing of these sea level excursions correlate well to the DSDP Site 609 detrital layers that are anchored in the latest Greenland ice core chronology (Obrochta et al., 2012 QSR). In the presentation, Antarctic ice sheet behavior during the H2 event will also be discussed using marginal seas oxygen records.

Denali Ice Core Record of North Pacific Sea Surface Temperatures and Marine Primary Productivity

NASA Astrophysics Data System (ADS)

Polashenski, D.; Osterberg, E. C.; Kreutz, K. J.; Winski, D.; Wake, C. P.; Ferris, D. G.; Introne, D.; Campbell, S. W.

2016-12-01

Chemical analyses of precipitation preserved in glacial ice cores provide a unique opportunity to study changes in atmospheric circulation patterns and ocean surface conditions through time. In this study, we aim to investigate changes in both the physical and biological parameters of the north-central Pacific Ocean and Bering Sea over the twentieth century using the deuterium excess (d-excess) and methanesulfonic acid (MSA) records from the Mt. Hunter ice cores drilled in Denali National Park, Alaska. These parallel, 208 m-long ice cores were drilled to bedrock during the 2013 field season on the Mt. Hunter plateau (63° N, 151° W, 3,900 m above sea level) by a collaborative research team consisting of members from Dartmouth College and the Universities of Maine and New Hampshire. The cores were sampled on a continuous melter system at Dartmouth College and analyzed for the concentrations major ions (Dionex IC) and trace metals (Element2 ICPMS), and for stable water isotope ratios (Picarro). The depth-age scale has been accurately dated to 400 AD using annual layer counting of several chemical species and further validated using known historical volcanic eruptions and the Cesium-137 spike associated with nuclear weapons testing in 1963. We use HYSPLIT back trajectory modeling to identify likely source areas of moisture and aerosol MSA being transported to the core site. Satellite imagery allows for a direct comparison between chlorophyll a concentrations in these source areas and MSA concentrations in the core record. Preliminary analysis of chlorophyll a and MSA concentrations, both derived almost exclusively from marine biota, suggest that the Mt. Hunter ice cores reflect changes in North Pacific and Bering Sea marine primary productivity. Analysis of the water isotope and MSA data in conjunction with climate reanalysis products shows significant correlations (p<0.05) between d-excess and MSA in the ice record and sea surface temperatures in the Bering Sea and

Organotins in North Sea brown shrimp (Crangon crangon L.) after implementation of the TBT ban.

PubMed

Verhaegen, Y; Monteyne, E; Neudecker, T; Tulp, I; Smagghe, G; Cooreman, K; Roose, P; Parmentier, K

2012-03-01

The organotin (OT) compounds tributyltin (TBT) and triphenyltin (TPhT) are potent biocides that have been used ubiquitously in antifouling paints and pesticides since the mid-1970s. These biocides are extremely toxic to marine life, particularly marine gastropod populations. The European Union therefore took measures to reduce the use of TBT-based antifouling paints on ships and ultimately banned these paints in 2003. Despite sufficient data on OT concentrations in marine gastropods, data are scarce for other species such as the North Sea brown shrimp (Crangon crangon), a dominant crustacean species in North Sea inshore benthic communities. The present study provides the first spatial overview of OT concentrations in North Sea brown shrimp. We have compared these data with historical concentrations in shrimp as well as with sediment concentrations. We have also addressed the effect on the shrimp stock and any human health risks associated with the OT concentrations found. TBT and TPhT in shrimp tail muscle ranged from 4 to 124 and from 1 to 24 μg kg(-1) DW, respectively. High levels are accumulated in estuarine areas and are clearly related with sediment concentrations (biota-sediment accumulation factor ~10). Levels have decreased approximately 10-fold since the ban took effect, coinciding with a recovery of the shrimp stock after 30 years of gradual regression. Furthermore, the OT levels found in brown shrimp no longer present a human health risk. Copyright © 2011 Elsevier Ltd. All rights reserved.

Modelling Local Sea-Breeze Flow and Associated Dispersion Patterns Over a Coastal Area in North-East Spain: A Case Study

NASA Astrophysics Data System (ADS)

Soler, M. R.; Arasa, R.; Merino, M.; Olid, M.; Ortega, S.

2011-07-01

The structure and evolution of the sea breeze in the north-west part of the Mediterranean (Catalonia, north-east Spain) is studied both experimentally and, predominantly, using numerical models to increase understanding of sea-breeze structure and three-dimensional (3D) pollution distributions in coastal environments. Sea-breeze components are modelled and analyzed using the fifth-generation Pennsylvania State University-National Centre for Atmospheric Research Mesoscale Model (MM5). The results show that the growth and structure of the sea-breeze circulation is modulated by the synoptic flow and especially by the complex topography of the area. 3D pollution transport in a sea breeze is modelled by coupling the MM5 to the Community Multiscale Air Quality (CMAQ) model, with results indicating that topography and synoptic flow are the main factors modulating horizontal and vertical pollutant transport in sea-breeze episodes. In this way, horizontal dispersion is limited by the complex topography of the area, whilst the sea-breeze flow is intensified by anabatic upslope winds that contribute to vertical pollutant transport. The numerical model results also indicate that the sea-breeze circulation with a weak return flow at upper levels grows due to a synoptic onshore wind component. However, such a sea-breeze circulation is capable of transporting pollutants towards the coast.

Spawning stock and recruitment in North Sea cod shaped by food and climate

PubMed Central

Olsen, Esben Moland; Ottersen, Geir; Llope, Marcos; Chan, Kung-Sik; Beaugrand, Grégory; Stenseth, Nils Chr.

2011-01-01

In order to provide better fisheries management and conservation decisions, there is a need to discern the underlying relationship between the spawning stock and recruitment of marine fishes, a relationship which is influenced by the environmental conditions. Here, we demonstrate how the environmental conditions (temperature and the food availability for fish larvae) influence the stock–recruitment relationship and indeed what kind of stock–recruitment relationship we might see under different environmental conditions. Using unique zooplankton data from the Continuous Plankton Recorder, we find that food availability (i.e. zooplankton) in essence determines which model applies for the once large North Sea cod (Gadus morhua) stock. Further, we show that recruitment is strengthened during cold years and weakened during warm years. Our combined model explained 45 per cent of the total variance in cod recruitment, while the traditional Ricker and Beverton–Holt models only explained about 10 per cent. Specifically, our approach predicts that a full recovery of the North Sea cod stock might not be expected until the environment becomes more favourable. PMID:20810442

Space Radar Image of North Sea, Germany

NASA Technical Reports Server (NTRS)

1994-01-01

This is an X-band image of an oil slick experiment conducted in the North Sea, Germany. The image is centered at 54.58 degrees north latitude and 7.48 degrees east longitude. This image was acquired by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on October 6, 1994, during the second flight of the spaceborne radar. The experiment was designed to differentiate between petroleum oil spills and natural slicks floating on the sea surface. Two types of petroleum oil and six types of oils resembling natural sea surface slicks were poured on the sea surface from ships and a helicopter just before the space shuttle flew over the region. At the bottom of the image is the Sylt peninsula, a famous holiday resort. Twenty-six gallons (100 liters) of diesel oil was dissipated due to wave action before the shuttle reached the site. The oil spill seen at the uppermost part of the image is about 105 gallons (400 liters) of heavy heating oil and the largest spill is about 58 gallons (220 liters) of oleyl alcohol, resembling a 'natural oil' like the remaining five spills used to imitate natural slicks that have occurred offshore from various states. The volume of these other oils spilled on the ocean surface during the five experimental spills varied from 16 gallons to 21 gallons (60 liters to 80 liters). The distance between neighboring spills was about half a mile (800 meters) at the most. The largest slick later thinned out to monomolecular sheets of about 10 microns, which is the dimension of a molecule. Oceanographers found that SIR-C/X-SAR was able to clearly distinguish the oil slicks from algae products dumped nearby. Preliminary indications are that various types of slicks may be distinguished, especially when other radar wavelengths are included in the analysis. Radar imaging of the world's oceans on a continuing basis may allow oceanographers in the future to detect and clean up oil spills much more

The efficacy of the modified Atkins diet in North Sea Progressive Myoclonus Epilepsy: an observational prospective open-label study.

PubMed

van Egmond, Martje E; Weijenberg, Amerins; van Rijn, Margreet E; Elting, Jan Willem J; Gelauff, Jeannette M; Zutt, Rodi; Sival, Deborah A; Lambrechts, Roald A; Tijssen, Marina A J; Brouwer, Oebele F; de Koning, Tom J

2017-03-07

North Sea Progressive Myoclonus Epilepsy is a rare and severe disorder caused by mutations in the GOSR2 gene. It is clinically characterized by progressive myoclonus, seizures, early-onset ataxia and areflexia. As in other progressive myoclonus epilepsies, the efficacy of antiepileptic drugs is disappointingly limited in North Sea Progressive Myoclonus Epilepsy. The ketogenic diet and the less restrictive modified Atkins diet have been proven to be effective in other drug-resistant epilepsy syndromes, including those with myoclonic seizures. Our aim was to evaluate the efficacy of the modified Atkins diet in patients with North Sea Progressive Myoclonus Epilepsy. Four North Sea Progressive Myoclonus Epilepsy patients (aged 7-20 years) participated in an observational, prospective, open-label study on the efficacy of the modified Atkins diet. Several clinical parameters were assessed at baseline and again after participants had been on the diet for 3 months. The primary outcome measure was health-related quality of life, with seizure frequency and blinded rated myoclonus severity as secondary outcome measures. Ketosis was achieved within 2 weeks and all patients completed the 3 months on the modified Atkins diet. The diet was well tolerated by all four patients. Health-related quality of life improved considerably in one patient and showed sustained improvement during long-term follow-up, despite the progressive nature of the disorder. Health-related quality of life remained broadly unchanged in the other three patients and they did not continue the diet. Seizure frequency remained stable and blinded rating of their myoclonus showed improvement, albeit modest, in all patients. This observational, prospective study shows that some North Sea Progressive Myoclonus Epilepsy patients may benefit from the modified Atkins diet with sustained health-related quality of life improvement. Not all our patients continued on the diet, but nonetheless we show that the modified

Temperature tracking by North Sea benthic invertebrates in response to climate change.

PubMed

Hiddink, Jan G; Burrows, Michael T; García Molinos, Jorge

2015-01-01

Climate change is a major threat to biodiversity and distributions shifts are one of the most significant threats to global warming, but the extent to which these shifts keep pace with a changing climate is yet uncertain. Understanding the factors governing range shifts is crucial for conservation management to anticipate patterns of biodiversity distribution under future anthropogenic climate change. Soft-sediment invertebrates are a key faunal group because of their role in marine biogeochemistry and as a food source for commercial fish species. However, little information exists on their response to climate change. Here, we evaluate changes in the distribution of 65 North Sea benthic invertebrate species between 1986 and 2000 by examining their geographic, bathymetric and thermal niche shifts and test whether species are tracking their thermal niche as defined by minimum, mean or maximum sea bottom (SBT) and surface (SST) temperatures. Temperatures increased in the whole North Sea with many benthic invertebrates showing north-westerly range shifts (leading/trailing edges as well as distribution centroids) and deepening. Nevertheless, distribution shifts for most species (3.8-7.3 km yr(-1) interquantile range) lagged behind shifts in both SBT and SST (mean 8.1 km yr(-1)), resulting in many species experiencing increasing temperatures. The velocity of climate change (VoCC) of mean SST accurately predicted both the direction and magnitude of distribution centroid shifts, while maximum SST did the same for contraction of the trailing edge. The VoCC of SBT was not a good predictor of range shifts. No good predictor of expansions of the leading edge was found. Our results show that invertebrates need to shift at different rates and directions to track the climate velocities of different temperature measures, and are therefore lagging behind most temperature measures. If these species cannot withstand a change in thermal habitat, this could ultimately lead to a drop in

Late Pliocene-Pleistocene environments and glacial history of the northern North Sea

NASA Astrophysics Data System (ADS)

Reinardy, Benedict T. I.; Hjelstuen, Berit O.; Sejrup, Hans Petter; Augedal, Hans; Jørstad, Arild

2017-02-01

Based on new geochronological (amino acids and Sr-isotopes) and lithological data combined with analyses of 3D seismic data, the Pliocene-Pleistocene development of the central northern North Sea has been investigated. At the start of the Plio-Pleistocene Transition the study area was dominated by a deltaic, shallow marine or tidal depositional environment with sediments mainly sourced from the west. These sand-rich sediments include green glauconitic grains that belong to the Utsira Sand with a local provenance. Directly above the base Quaternary (R2) a 60 m thick layer of mud-rich sediments of glacimarine origin were deposited at a rate of ∼12 cm/ka between ∼2-1.5 Ma and up to 80 cm/ka between 1.5 and 1.2 Ma possibly reflecting glacial ice advancing to the Norwegian coastline. The high rate of deposition in the Early Pleistocene occurred immediately before the initiation of the Norwegian Channel Ice Stream at ∼1.1 Ma. Following this, a large part of the sediment input from Fennoscandia seems to have been directed away from the study area to the shelf break. At the start of the Mid Pleistocene Transition (MPT), subaerial conditions allowed the formation of a >50 km long fluvial channel across the study area draining water from the east to the south west. The earliest evidence of grounded ice in the investigated area comes from mega scale glacial lineations formed during the MPT, at or just after ∼1.2 Ma. Following this, a regional unconformity (R4) was formed by one or more grounded ice advances across the study area possibly during or directly after the MPT and likely marks the boundary between the Early and Mid Pleistocene glacimarine sediments. The Mid to Late Pleistocene stratigraphy is dominated by glacimarine sediments and tills and is associated with multiple generations of tunnel valleys observed within the seismic data. A high shear strength till containing chalk clasts transported from the west and/or south of the study area was likely deposited

Hierarchical modeling of bycatch rates of sea turtles in the western North Atlantic

USGS Publications Warehouse

Gardner, B.; Sullivan, P.J.; Epperly, S.; Morreale, S.J.

2008-01-01

Previous studies indicate that the locations of the endangered loggerhead Caretta caretta and critically endangered leatherback Dermochelys coriacea sea turtles are influenced by water temperatures, and that incidental catch rates in the pelagic longline fishery vary by region. We present a Bayesian hierarchical model to examine the effects of environmental variables, including water temperature, on the number of sea turtles captured in the US pelagic longline fishery in the western North Atlantic. The modeling structure is highly flexible, utilizes a Bayesian model selection technique, and is fully implemented in the software program WinBUGS. The number of sea turtles captured is modeled as a zero-inflated Poisson distribution and the model incorporates fixed effects to examine region-specific differences in the parameter estimates. Results indicate that water temperature, region, bottom depth, and target species are all significant predictors of the number of loggerhead sea turtles captured. For leatherback sea turtles, the model with only target species had the most posterior model weight, though a re-parameterization of the model indicates that temperature influences the zero-inflation parameter. The relationship between the number of sea turtles captured and the variables of interest all varied by region. This suggests that management decisions aimed at reducing sea turtle bycatch may be more effective if they are spatially explicit. ?? Inter-Research 2008.

Holocene relative sea-level changes from North America and the Caribbean

NASA Astrophysics Data System (ADS)

Horton, Benjamin; Engelhart, Simon; Vacchi, Matteo; Khan, Nicole; Peltier, Dick; Roy, Keven

2014-05-01

Reconstructions of Holocene relative sea level (RSL) are important for identifying the ice equivalent meltwater contribution to sea-level change during deglaciation. Holocene RSL reconstructions from near, intermediate and far field regions enable the assessment of earth and ice parameters of Glacial Isostatic Adjustment (GIA) models. RSL reconstructions provide data for estimating rates of spatially variable and ongoing vertical land motion; a requirement for understanding the variation in modern and late Holocene sea level as recorded by instrumental and proxy records. Here we explain the methodology employed to reconstruct former sea levels, which follows the practice of the International Geoscience Programme (IGCP). We produce sea level index points from the Pacific and Atlantic coasts of North America and the Caribbean. Index points are defined as the most reliable observations of former sea levels. They consist of an estimate of X (age) and Y (the position of former RSL). Where a suite of index points are developed for a locality or region, they describe changes in RSL through time and estimate rates of change. A valid index point must meet the following four criteria; (1) location of the sample is known; (2) the altitude of the sample (and the error associated with measuring that altitude) is known; (3) the indicative meaning (the relationship between the sample and a tide level) is estimated; and (4) the age of the sample, which is commonly radiocarbon dated is calibrated to sidereal years using the latest calibration curves. In total databases have over 2000 sea-level index points from formerly ice covered, uplifting regions of Canada, to the region of forebulge collapse along the subsiding mid-Atlantic and mid-Pacific coastlines of the United States, to the tropical regions of the Caribbean. Recent analyses of these new published databases have led to a further refinement of the most recent of the ICE-NG (VMX) series of global models of GIA. The records

Predation rates by North Sea cod (Gadus morhua) - Predictions from models on gastric evacuation and bioenergetics

USGS Publications Warehouse

Hansson, S.; Rudstam, L. G.; Kitchell, J.F.; Hilden, M.; Johnson, B.L.; Peppard, P.E.

1996-01-01

We compared four different methods for estimating predation rates by North Sea cod (Gadus moi hua). Three estimates, based on gastric evacuation rates, came from an ICES multispecies working group and the fourth from a bioenergetics model. The bioenergetics model was developed from a review of literature on cod physiology. The three gastric evacuation rate models produced very different prey consumption estimates for small (2 kg) fish. For most size and age classes, the bioenergetics model predicted food consumption rates intermediate to those predicted by the gastric evacuation models. Using the standard ICES model and the average population abundance and age structure for 1974-1989, annual, prey consumption by the North Sea cod population (age greater than or equal to 1) was 840 kilotons. The other two evacuation rate models produced estimates of 1020 and 1640 kilotons, respectively. The bioenergetics model estimate was 1420 kilotons. The major differences between models were due to consumption rate estimates for younger age groups of cod. (C) 1996 International Council for the Exploration of the Sea

Climate change impact on North Sea wave conditions: a consistent analysis of ten projections

NASA Astrophysics Data System (ADS)

Grabemann, Iris; Groll, Nikolaus; Möller, Jens; Weisse, Ralf

2015-02-01

Long-term changes in the mean and extreme wind wave conditions as they may occur in the course of anthropogenic climate change can influence and endanger human coastal and offshore activities. A set of ten wave climate projections derived from time slice and transient simulations of future conditions is analyzed to estimate the possible impact of anthropogenic climate change on mean and extreme wave conditions in the North Sea. This set includes different combinations of IPCC SRES emission scenarios (A2, B2, A1B, and B1), global and regional models, and initial states. A consistent approach is used to provide a more robust assessment of expected changes and uncertainties. While the spatial patterns and the magnitude of the climate change signals vary, some robust features among the ten projections emerge: mean and severe wave heights tend to increase in the eastern parts of the North Sea towards the end of the twenty-first century in nine to ten projections, but the magnitude of the increase in extreme waves varies in the order of decimeters between these projections. For the western parts of the North Sea more than half of the projections suggest a decrease in mean and extreme wave heights. Comparing the different sources of uncertainties due to models, scenarios, and initial conditions, it can be inferred that the influence of the emission scenario on the climate change signal seems to be less important. Furthermore, the transient projections show strong multi-decadal fluctuations, and changes towards the end of the twenty-first century might partly be associated with internal variability rather than with systematic changes.

An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation

NASA Astrophysics Data System (ADS)

Caian, Mihaela; Koenigk, Torben; Döscher, Ralf; Devasthale, Abhay

2018-01-01

This work investigates links between Arctic surface variability and the phases of the winter (DJF) North Atlantic Oscillation (NAO) on interannual time-scales. The analysis is based on ERA-reanalysis and model data from the EC-Earth global climate model. Our study emphasizes a mode of sea-ice cover variability that leads the NAO index by 1 year. The mechanism of this leading is based on persistent surface forcing by quasi-stationary meridional thermal gradients. Associated thermal winds lead a slow adjustment of the pressure in the following winter, which in turn feeds-back on the propagation of sea-ice anomalies. The pattern of the sea-ice mode leading NAO has positive anomalies over key areas of South-Davis Strait-Labrador Sea, the Barents Sea and the Laptev-Ohkostsk seas, associated to a high pressure anomaly over the Canadian Archipelago-Baffin Bay and the Laptev-East-Siberian seas. These anomalies create a quasi-annular, quasi-steady, positive gradient of sea-ice anomalies about coastal line (when leading the positive NAO phase) and force a cyclonic vorticity anomaly over the Arctic in the following winter. During recent decades in spite of slight shifts in the modes' spectral properties, the same leading mechanism remains valid. Encouraging, actual models appear to reproduce the same mechanism leading model's NAO, relative to model areas of persistent surface forcing. This indicates that the link between sea-ice and NAO could be exploited as a potential skill-source for multi-year prediction by addressing the key problem of initializing the phase of the NAO/AO (Arctic Oscillation).

Sea Spray Aerosol Production over the North Atlantic

NASA Astrophysics Data System (ADS)

Bates, T. S.; Quinn, P.

2017-12-01

Breaking waves on the ocean surface generate air bubbles that scavenge organic matter from the surrounding seawater. When injected into the atmosphere, these bubbles burst, yielding sea spray aerosol (SSA), a mixture of organic and inorganic compounds with the organic matter enriched relative to seawater. SSA mass is well documented as the dominant component of aerosol light scattering over the remote oceans. The importance of SSA number to marine boundary layer cloud condensation nuclei (CCN) is much less certain. During the Western Atlantic Climate Study cruises (WACS-1 - August 2012 and WACS-2 - May-June 2014) and the North Atlantic Aerosols and Marine Ecosystem Study cruises (NAAMES-1 - November 2015, NAAMES-2 - May 2016, and NAAMES-3 - September 2017), we generated and measured freshly emitted SSA using the Sea Sweep SSA generator. During the 2017 cruise we also generated SSA with a Marine Aerosol Reference Tank (MART). Using the data generated on these 5 cruises and a large database of remote marine boundary layer aerosol measurements we will address three questions during this presentation: 1 - Do phytoplankton ecosystems affect the organic enrichment of freshly emitted SSA?, 2 - Do plankton ecosystems affect the number production flux of SSA?, and 3 - Is SSA a significant source of atmospheric CCN?

Impacts of Interannual Ocean Circulation Variability on Japanese Eel Larval Migration in the Western North Pacific Ocean.

PubMed

Chang, Yu-Lin; Sheng, Jinyu; Ohashi, Kyoko; Béguer-Pon, Mélanie; Miyazawa, Yasumasa

2015-01-01

The Japanese eel larvae hatch near the West Mariana Ridge seamount chain and travel through the North Equatorial Current (NEC), the Kuroshio, and the Subtropical Countercurrent (STCC) region during their shoreward migration toward East Asia. The interannual variability of circulation over the subtropical and tropical regions of the western North Pacific Ocean is affected by the Philippines-Taiwan Oscillation (PTO). This study examines the effect of the PTO on the Japanese eel larval migration routes using a three-dimensional (3D) particle tracking method, including vertical and horizontal swimming behavior. The 3D circulation and hydrography used for particle tracking are from the ocean circulation reanalysis produced by the Japan Coastal Ocean Predictability Experiment 2 (JCOPE2). Our results demonstrate that bifurcation of the NEC and the strength and spatial variation of the Kuroshio affect the distribution and migration of eel larvae. During the positive phase of PTO, more virtual eels ("v-eels") can enter the Kuroshio to reach the south coast of Japan and more v-eels reach the South China Sea through the Luzon Strait; the stronger and more offshore swing of the Kuroshio in the East China Sea leads to fewer eels entering the East China Sea and the onshore movement of the Kuroshio to the south of Japan brings the eels closer to the Japanese coast. Significant differences in eel migration routes and distributions regulated by ocean circulation in different PTO phases can also affect the otolith increment. The estimated otolith increment suggests that eel age tends to be underestimated after six months of simulation due to the cooler lower layer temperature. Underestimation is more significant in the positive PTO years due to the wide distribution in higher latitudes than in the negative PTO years.

Geological evolution of the North Sea: a dynamic 3D model including petroleum system elements

NASA Astrophysics Data System (ADS)

Sabine, Heim; Rüdiger, Lutz; Dirk, Kaufmann; Lutz, Reinhardt

2013-04-01

This study investigates the sedimentary basin evolution of the German North Sea with a focus on petroleum generation, migration and accumulation. The study is conducted within the framework of the project "Geoscientific Potential of the German North Sea (GPDN)", a joint project of federal (BGR, BSH) and state authorities (LBEG) with partners from industry and scientific institutions. Based on the structural model of the "Geotektonischer Atlas 3D" (GTA3D, LBEG), this dynamic 3D model contains additionally the northwestern part ("Entenschnabel" area) of the German North Sea. Geological information, e.g. lithostratigraphy, facies and structural data, provided by industry, was taken from published research projects, or literature data such as the Southern Permian Basin Atlas (SPBA; Doornenbal et al., 2010). Numerical modeling was carried out for a sedimentary succession containing 17 stratigraphic layers and several sublayers, representing the sedimentary deposition from the Devonian until Present. Structural details have been considered in terms of simplified faults and salt structures, as well as main erosion and salt movement events. Lithology, facies and the boundary conditions e.g. heat flow, paleo water-depth and sediment water interface temperature were assigned. The system calibration is based on geochemical and petrological data, such as maturity of organic matter (VRr) and present day temperature. Due to the maturity of the sedimentary organic matter Carboniferous layers are the major source rocks for gas generation. Main reservoir rocks are the Rotliegend sandstones, furthermore, sandstones of the Lower Triassic and Jurassic can serve as reservoir rocks in areas where the Zechstein salts are absent. The model provides information on the temperature and maturity distribution within the main source rock layers as well as information of potential hydrocarbon generation based on kinetic data for gas liberation. Finally, this dynamic 3D model offers a first

Rare earth elements in Japan Sea sediments and diagenetic behavior of Ce/Ce∗: results from ODP Leg 127

USGS Publications Warehouse

Murray, R.; Buchholtz ten Brink, Marilyn R.; Brumsack, Hans-Juergen; Gerlach, David C.; Russ III, G. Price

1991-01-01

Ce/Ce* profiles at all three sites increase monotonically with depth, and record progressive diagenetic LREE fractionation. The observed Ce/Ce* record does not respond to changes in oxygenation state of the overlying water, and Ce/Ce* correlated slightly better with depth than with age. The downhole increase in Ce/Ce* at Site 794 and Site 797 is a passive response to diagenetic transfer of LREE (except Ce) from sediment to interstitial water. At Site 795, the overall lack of correlation between Ce/Ce* and L(ln/Ybnsuggests that other processes are occurring which mask the diagenetic behavior of all LREEs. First-order calculations of the Ce budget in Japan Sea waters and sediment indicate that ~20% of the excess Ce adsorbed by settling particles is recycled within the water column, and that an additional ~38% is recycled at or near the seafloor (data from Masuzawa and Koyama, 1989). Thus, because the remaining excess Ce is only ~10% of the total Ce, there is not a large source of Ce to the deeply buried sediment, further suggesting that the downhole increase in Ce/Ce* is a passive response to diagenetic behavior of the other LREEs. The REE chemistry of Japan Sea sediment therefore predicts successive downhole addition of LREEs to deeply-buried interstitial waters.

Entering uncharted waters: Long-term dynamics of two data limited fish species, turbot and brill, in the North Sea

NASA Astrophysics Data System (ADS)

Kerby, Tina K.; Cheung, William W. L.; van Oosterhout, Cock; Engelhard, Georg H.

2013-11-01

In the North Sea, turbot (Scophthalmus maximus) and brill (Scophthalmus rhombus) represent highly valuable species in commercial fisheries. Still, available data for both species are limited, making stock assessment difficult. Long-term fisheries data have the potential to improve the understanding of stock dynamics such as long-term distribution changes or development in species' abundances. Historical British otter trawler lpue (landings-per-unit-effort) data from 1923 to 2009, and at the spatial scale of ICES rectangles, revealed that the distribution patterns of turbot and brill were different for most of the 20th century and only became similar in the recent decade. Further, between the 1920s and 1960s, turbot was commonly caught in the northern North Sea and in particular on Turbot Bank, at that time a turbot hotspot off the east coast of Scotland. Within a short time period turbot nearly disappeared from this region. Brill, in contrast, revealed a stable distribution in the southern and central North Sea with a slow expansion into the central North Sea. We used survey cpue (catch-per-unit-effort) from the International Bottom Trawl Survey (IBTS; 1970-2009) and the Beam Trawl Survey (BTS; 1985-2009), as well as British otter trawler lpue, as proxies for the abundance of adult turbot and brill. Commercial lpue suggested for brill and turbot a long-term decrease in abundance. IBTS cpue suggested an increase in abundance for turbot, but this was not confirmed by the BTS. For brill, both surveys did not show a clear trend.

Synoptic characteristics of heavy snowfalls at Busan of Korea caused by polar lows over the East/Japan Sea

NASA Astrophysics Data System (ADS)

Choi, Jae-Won; Cha, Yumi; Kim, Hae-Dong

2018-02-01

The results of the present study prove that snowfall occurred due to the polar low (PL) in the Korean Peninsula and six cases of snowfall exceeding a snow depth of 2 cm over the past 16 years in Busan, South Korea. A strong northwesterly air current with a cold outbreak at the lower level passed through the Korean Peninsula and penetrated into the East/Japan Sea causing the generation and characteristics of a PL. However, a northeasterly air current due to a synoptic low (SL) in East Japan approached the east coast via the East/Japan Sea, which generated a wind field with mesoscale cyclonic circulation. In the center of this cyclone, a strong positive vorticity region was revealed from the lower level to the upper level. The air temperature in the center of the PL was warmer than the surrounding areas at the lower level. As the PL developed and the air temperature decreased, a rapid tropopause drop followed due to the effect of the cold core along with the cutoff low at the mid-level or the higher level. As a result, the stratification became more unstable. The PL moved into Busan as the cold core at the upper level rapidly moved to the lower latitudes, which formed an unstable region around Busan. The PL decayed because the cutoff low, the cold core, and the positive vorticity region at the upper level quickly moved to the east, thereby causing the stratification to stabilize. Also, because the approach to the Japanese Archipelago caused an increase in surface friction, the original structure could no longer be maintained.

Intermitted Occurrence of Millennial-scale Variability of East Asian Summer Monsoon before 1.45 Ma based on the High-resolution Br Record of the Japan Sea Sediments

NASA Astrophysics Data System (ADS)

Tada, R.; Seki, A.; Ikeda, M.; Irino, T.; Ikehara, K.; Karasuda, A.; Sugisaki, S.; Sagawa, T.; Itaki, T.; Kubota, Y.; Murayama, M.; Lu, S.; Murray, R. W.; Alvarez Zarikian, C. A.

2017-12-01

It is well-known that Dansgaard-Oeschger Cycles (DOC) and East Asian Summer Monsoon (EASM) are closely linked during the last glacial period, and that Atlantic Meridional Ocean Circulation (AMOC) played a key role to amplify and propagate the DOC signal. Climatic model studies also suggested that on and off of AMOC caused simultaneous north-south shifts of westerly jets (WJ) in both hemispheres and ITCZ. Since WJ over East Asia bounds the northern limit of EASM front, it is likely that N-S shifts of WJ caused millennial-scale variability of EASM precipitation distribution. This linkage can be traced back to ca. 0.4 Ma based on comparison of synthetic Greenland temperature record of Barker et al. (2011) with d18O record of Chinese speleothems, and back to 0.8 Ma based on comparison of synthetic Greenland temperature record with Br profile of the hemipelagic sediments of the Japan Sea (reflecting marine organic carbon content and considered as a proxy of EASM) retrieved from Site U1424 during IODP Exp. 346. Br profile of the Japan Sea sediments also implies that millennial-scale variability of EASM was persistent since ca. 1.45 Ma ago, which was probably linked with AMOC variability. However, presence/absence of millennial-scale variability of EASM and possibility of its linkage with AMOC variability are not known for the period before 1.45 Ma. Here we extend our Br record of Site U1424 back to ca. 3 Ma and demonstrate that there was intermitted occurrence of millennial-scale EASM variability since ca. 2.5 Ma when LR04 glacial d18O value first exceeded ca. 4 permil. This may suggest the presence of threshold of ice volume to cause millennial-scale variability of AMOC and EASM.

Microcrystalline dolomite within massive Japan Sea methane hydrate: origin and development ascertained by inclusions within inclusions.

NASA Astrophysics Data System (ADS)

Snyder, G. T.; Kakizaki, Y.; Matsumoto, R.; Suzuki, Y.; Takahata, N.; Sano, Y.; Tanaka, K.; Tomaru, H.; Imajo, T.; Iguchi, A.

2017-12-01

Microcrystalline dolomite grains were recently discovered as inclusions within relatively pure massive gas hydrate recovered from the Joetsu Basin area of the Japan Sea. These grains presumably formed as a consequence of the highly saline conditions in fluid inclusions which developed between coalescing grain boundaries within the growing hydrate. Stable carbon and oxygen isotopic composition of the dolomite is consistent with crystal growth occurring within such fluids. In addition to stable isotopes, we investigate trends in Mg/Ca ratios of the grains as well as the composition of inclusions which exist within the dolomites. Preliminary research shows that these inclusions retain valuable information as to the conditions which existed at the time of formation, as well as the dynamics of these extensive hydrate deposits over time. This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).

High-resolution IP25-based reconstruction of sea-ice variability in the western North Pacific and Bering Sea during the past 18,000 years

NASA Astrophysics Data System (ADS)

Méheust, Marie; Stein, Ruediger; Fahl, Kirsten; Max, Lars; Riethdorf, Jan-Rainer

2016-04-01

Due to its strong influence on heat and moisture exchange between the ocean and the atmosphere, sea ice is an essential component of the global climate system. In the context of its alarming decrease in terms of concentration, thickness and duration, understanding the processes controlling sea-ice variability and reconstructing paleo-sea-ice extent in polar regions have become of great interest for the scientific community. In this study, for the first time, IP25, a recently developed biomarker sea-ice proxy, was used for a high-resolution reconstruction of the sea-ice extent and its variability in the western North Pacific and western Bering Sea during the past 18,000 years. To identify mechanisms controlling the sea-ice variability, IP25 data were associated with published sea-surface temperature as well as diatom and biogenic opal data. The results indicate that a seasonal sea-ice cover existed during cold periods (Heinrich Stadial 1 and Younger Dryas), whereas during warmer intervals (Bølling-Allerød and Holocene) reduced sea ice or ice-free conditions prevailed in the study area. The variability in sea-ice extent seems to be linked to climate anomalies and sea-level changes controlling the oceanographic circulation between the subarctic Pacific and the Bering Sea, especially the Alaskan Stream injection though the Aleutian passes.

The wind sea and swell waves climate in the Nordic seas

NASA Astrophysics Data System (ADS)

Semedo, Alvaro; Vettor, Roberto; Breivik, Øyvind; Sterl, Andreas; Reistad, Magnar; Soares, Carlos Guedes; Lima, Daniela

2015-02-01

A detailed climatology of wind sea and swell waves in the Nordic Seas (North Sea, Norwegian Sea, and Barents Sea), based on the high-resolution reanalysis NORA10, developed by the Norwegian Meteorological Institute, is presented. The higher resolution of the wind forcing fields, and the wave model (10 km in both cases), along with the inclusion of the bottom effect, allowed a better description of the wind sea and swell features, compared to previous global studies. The spatial patterns of the swell-dominated regional wave fields are shown to be different from the open ocean, due to coastal geometry, fetch dimensions, and island sheltering. Nevertheless, swell waves are still more prevalent and carry more energy in the Nordic Seas, with the exception of the North Sea. The influence of the North Atlantic Oscillation on the winter regional wind sea and swell patterns is also presented. The analysis of the decadal trends of wind sea and swell heights during the NORA10 period (1958-2001) shows that the long-term trends of the total significant wave height (SWH) in the Nordic Seas are mostly due to swell and to the wave propagation effect.

The distribution of deep-sea sponge aggregations in the North Atlantic and implications for their effective spatial management

NASA Astrophysics Data System (ADS)

Howell, Kerry-Louise; Piechaud, Nils; Downie, Anna-Leena; Kenny, Andrew

2016-09-01

Sponge aggregations have been recognised as key component of shallow benthic ecosystems providing several important functional roles including habitat building and nutrient recycling. Within the deep-sea ecosystem, sponge aggregations may be extensive and available evidence suggests they may also play important functional roles, however data on their ecology, extent and distribution in the North Atlantic is lacking, hampering conservation efforts. In this study, we used Maximum Entropy Modelling and presence data for two deep-sea sponge aggregation types, Pheronema carpenteri aggregations and ostur aggregations dominated by geodid sponges, to address the following questions: 1) What environmental factors drive the broad-scale distribution of these selected sponge grounds? 2) What is the predicted distribution of these grounds in the northern North Atlantic, Norwegian and Barents Sea? 3) How are these sponge grounds distributed between Exclusive Economic Zones (EEZs) and High Seas areas? 4) What percentage of these grounds in High Seas areas are protected by the current High Seas MPA network? Our results suggest that silicate concentration, temperature, depth and amount of particulate organic carbon are the most important drivers of sponge distribution. Most of the sponge grounds are located within national EEZs rather than in the High Seas. Coordinated conservation planning between nations with significant areas of sponge grounds such as Iceland, Greenland and Faroes (Denmark), Norway (coastal Norway and Svalbard), Portugal and the UK, should be implemented in order to effectively manage these communities in view of the increasing level of human activity within the deep-sea environment.

Potential Impacts of Offshore Wind Farms on North Sea Stratification

PubMed Central

Carpenter, Jeffrey R.; Merckelbach, Lucas; Callies, Ulrich; Clark, Suzanna; Gaslikova, Lidia; Baschek, Burkard

2016-01-01

Advances in offshore wind farm (OWF) technology have recently led to their construction in coastal waters that are deep enough to be seasonally stratified. As tidal currents move past the OWF foundation structures they generate a turbulent wake that will contribute to a mixing of the stratified water column. In this study we show that the mixing generated in this way may have a significant impact on the large-scale stratification of the German Bight region of the North Sea. This region is chosen as the focus of this study since the planning of OWFs is particularly widespread. Using a combination of idealised modelling and in situ measurements, we provide order-of-magnitude estimates of two important time scales that are key to understanding the impacts of OWFs: (i) a mixing time scale, describing how long a complete mixing of the stratification takes, and (ii) an advective time scale, quantifying for how long a water parcel is expected to undergo enhanced wind farm mixing. The results are especially sensitive to both the drag coefficient and type of foundation structure, as well as the evolution of the pycnocline under enhanced mixing conditions—both of which are not well known. With these limitations in mind, the results show that OWFs could impact the large-scale stratification, but only when they occupy extensive shelf regions. They are expected to have very little impact on large-scale stratification at the current capacity in the North Sea, but the impact could be significant in future large-scale development scenarios. PMID:27513754

Potential Impacts of Offshore Wind Farms on North Sea Stratification.

PubMed

Carpenter, Jeffrey R; Merckelbach, Lucas; Callies, Ulrich; Clark, Suzanna; Gaslikova, Lidia; Baschek, Burkard

2016-01-01

Advances in offshore wind farm (OWF) technology have recently led to their construction in coastal waters that are deep enough to be seasonally stratified. As tidal currents move past the OWF foundation structures they generate a turbulent wake that will contribute to a mixing of the stratified water column. In this study we show that the mixing generated in this way may have a significant impact on the large-scale stratification of the German Bight region of the North Sea. This region is chosen as the focus of this study since the planning of OWFs is particularly widespread. Using a combination of idealised modelling and in situ measurements, we provide order-of-magnitude estimates of two important time scales that are key to understanding the impacts of OWFs: (i) a mixing time scale, describing how long a complete mixing of the stratification takes, and (ii) an advective time scale, quantifying for how long a water parcel is expected to undergo enhanced wind farm mixing. The results are especially sensitive to both the drag coefficient and type of foundation structure, as well as the evolution of the pycnocline under enhanced mixing conditions-both of which are not well known. With these limitations in mind, the results show that OWFs could impact the large-scale stratification, but only when they occupy extensive shelf regions. They are expected to have very little impact on large-scale stratification at the current capacity in the North Sea, but the impact could be significant in future large-scale development scenarios.

Estimation of the isotopic composition and origins of winter precipitation over Japan using a regional isotope circulation model

NASA Astrophysics Data System (ADS)

Tanoue, M.; Ichiyanagi, K.; Yoshimura, K.; Shimada, J.; Hirabayashi, Y.

2017-12-01

Understanding the dynamics of the origins of precipitation (i.e., vapor source regions of evaporated moisture) is useful for long-term forecasting and calibration of water isotope thermometer. In the Asian monsoon region, vapor source regions are identified by the deuterium excess (d-excess; defined as δD - 8 • δ18O) of precipitation because its values mainly reflect humidity conditions during evaporation at the source regions. In Japan, previous studies assumed the Sea of Japan to be the dominant source of winter precipitation when the d-excess value in winter is >20‰ or higher than the average value in summer. Because this assumption is based on an interpretation that the high d-excess value is due to an interaction between the continental winter monsoon (WM) and warm sea surface at the Sea of Japan, it may not be appropriate for winter precipitation caused by extratropical cyclones (EC). Here, we utilized a regional isotope circulation model and then clarified local patterns of isotopic composition and the origins of precipitation in the WM and EC types over Japan. The results indicated that moisture originating from the Sea of Japan made the highest contribution to precipitation on the Sea of Japan side of Japan in the WM type, whereas the Pacific Ocean was the dominant source of precipitation over Japan in the EC type. Because d-excess values were higher in the WM than in the EC type, we can assume that the Sea of Japan was the dominant source of precipitation on the Sea of Japan side when the d-excess value was high. Because precipitation on the Pacific Ocean side and the Kyushu island of Japan was mainly caused by the EC type, we could not identify the dominant source of precipitation as the Sea of Japan from only the d-excess values in these regions. We also found that WM activity could be estimated from observed d-excess values due to a clear positive correlation between simulated d-excess values and the activity.

Sea Ice and Hydrographic Variability in the Northwest North Atlantic

NASA Astrophysics Data System (ADS)

Fenty, I. G.; Heimbach, P.; Wunsch, C. I.

2010-12-01

Sea ice anomalies in the Northwest North Atlantic's Labrador Sea are of climatic interest because of known and hypothesized feedbacks with hydrographic anomalies, deep convection/mode water formation, and Northern Hemisphere atmospheric patterns. As greenhouse gas concentrations increase, hydrographic anomalies formed in the Arctic Ocean associated with warming will propagate into the Labrador Sea via the Fram Strait/West Greenland Current and the Canadian Archipelago/Baffin Island Current. Therefore, understanding the dynamical response of sea ice in the basin to hydrographic anomalies is essential for the prediction and interpretation of future high-latitude climate change. Historically, efforts to quantify the link between the observed sea ice and hydrographic variability in the region has been limited due to in situ observation paucity and technical challenges associated with synthesizing ocean and sea ice observations with numerical models. To elaborate the relationship between sea ice and ocean variability, we create three one-year (1992-1993, 1996-1997, 2003-2004) three-dimensional time-varying reconstructions of the ocean and sea ice state in Labrador Sea and Baffin Bay. The reconstructions are syntheses of a regional coupled 32 km ocean-sea ice model with a suite of contemporary in situ and satellite hydrographic and ice data using the adjoint method. The model and data are made consistent, in a least-squares sense, by iteratively adjusting several model control variables (e.g., ocean initial and lateral boundary conditions and the atmospheric state) to minimize an uncertainty-weighted model-data misfit cost function. The reconstructions reveal that the ice pack attains a state of quasi-equilibrium in mid-March (the annual sea ice maximum) in which the total ice-covered area reaches a steady state -ice production and dynamical divergence along the coasts balances dynamical convergence and melt along the pack’s seaward edge. Sea ice advected to the

On the colour types in Lycodes nakamurae (Tanaka, 1914) and species composition of the subgenus Furcimanus (Perciformes: Zoarcidae: Lycodes) in the sea of Japan.

PubMed

Saveliev, Pavel A; Balanov, Andrey A; Kukhlevskii, Andrey D

2014-05-30

Two colour types were revealed in a zoarcid fish of the subgenus Furcimanus, genus Lycodes, in the Sea of Japan. A comparison of morphometric, meristic and genetic characters in dark coloured and light coloured individuals suggests that the two colour morphs represent a single species, determined to be Lycodes nakamurae (Tanaka, 1914). Variability in colouration within L. nakamurae and a lack of morphological or molecular characters distinguishing L. nakamurae from L. nishimurai Shinohara & Shirai, 2005 suggest that the latter should be considered a synonym of L. nakamurae (Tanaka, 1914). A record of L. pectoralis in the waters of the Republic of Korea is regarded as a misidentification. Thus, we conclude that only one species of the Lycodes subgenus Furcimanus, L. nakamurae, with dark and light colour morphs as well as specimens of intermediate colouration, inhabits the Sea of Japan.

Climate change and fishing: a century of shifting distribution in North Sea cod

PubMed Central

Engelhard, Georg H; Righton, David A; Pinnegar, John K

2014-01-01

Globally, spatial distributions of fish stocks are shifting but although the role of climate change in range shifts is increasingly appreciated, little remains known of the likely additional impact that high levels of fishing pressure might have on distribution. For North Sea cod, we show for the first time and in great spatial detail how the stock has shifted its distribution over the past 100 years. We digitized extensive historical fisheries data from paper charts in UK government archives and combined these with contemporary data to a time-series spanning 1913–2012 (excluding both World Wars). New analysis of old data revealed that the current distribution pattern of cod – mostly in the deeper, northern- and north-easternmost parts of the North Sea – is almost opposite to that during most of the Twentieth Century – mainly concentrated in the west, off England and Scotland. Statistical analysis revealed that the deepening, northward shift is likely attributable to warming; however, the eastward shift is best explained by fishing pressure, suggestive of significant depletion of the stock from its previous stronghold, off the coasts of England and Scotland. These spatial patterns were confirmed for the most recent 3½ decades by data from fisheries-independent surveys, which go back to the 1970s. Our results demonstrate the fundamental importance of both climate change and fishing pressure for our understanding of changing distributions of commercially exploited fish. PMID:24375860

Recent evolution of 129I levels in the Nordic Seas and the North Atlantic Ocean.

PubMed

Vivo-Vilches, Carlos; López-Gutiérrez, José María; Periáñez, Raúl; Marcinko, Charlotte; Le Moigne, Frédéric; McGinnity, Paul; Peruchena, Juan Ignacio; Villa-Alfageme, María

2018-04-15

Most of the anthropogenic radionuclide 129 I released to the marine environment from the nuclear fuel reprocessing plants (NFRP) at Sellafield (England) and La Hague (France) is transported to the Arctic Ocean via the North Atlantic Current and the Norwegian Coastal Current. 129 I concentrations in seawater provides a powerful and well-established radiotracer technique to provide information about the mechanisms which govern water mass transport in the Nordic Seas and the Arctic Ocean and is gaining importance when coupled with other tracers (e.g. CFC, 236 U). In this work, 129 I concentrations in surface and depth profiles from the Nordic Seas and the North Atlantic (NA) Ocean collected from four different cruises between 2011 and 2012 are presented. This work allowed us to i) update information on 129 I concentrations in these areas, required for the accurate use of 129 I as a tracer of water masses; and ii) investigate the formation of deep water currents in the eastern part of the Nordic Seas, by the analysis of 129 I concentrations and temperature-salinity (T-S) diagrams from locations within the Greenland Sea Gyre. In the Nordic Seas, 129 I concentrations in seawater are of the order of 10 9 at·kg -1 , one or two orders of magnitude higher than those measured at the NA Ocean, not so importantly affected by the releases from the NFRP. 129 I concentrations of the order of 10 8 atoms·kg -1 at the Ellet Line and the PAP suggest a direct contribution from the NFRP in the NA Ocean. An increase in the concentrations in the Nordic Seas between 2002 and 2012 has been detected, which agrees with the temporal evolution of the 129 I liquid discharges from the NFRPs in years prior to this. Finally, 129 I profile concentrations, 129 I inventories and T-S diagrams suggest that deep water formation occurred in the easternmost area of the Nordic Seas during 2012. Copyright © 2017 Elsevier B.V. All rights reserved.

Future projections of total snowfall and heavy snowfall in Japan simulated by large ensemble regional climate simulations.

NASA Astrophysics Data System (ADS)

Kawase, H.; Sasaki, H.; Murata, A.; Nosaka, M.; Ito, R.; Dairaku, K.; Sasai, T.; Yamazaki, T.; Sugimoto, S.; Watanabe, S.; Fujita, M.; Kawazoe, S.; Okada, Y.; Ishii, M.; Mizuta, R.; Takayabu, I.

2017-12-01

We performed large ensemble climate experiments to investigate future changes in extreme weather events using Meteorological Research Institute-Atmospheric General Circulation Model (MRI-AGCM) with about 60 km grid spacing and Non-Hydrostatic Regional Climate Model with 20 km grid spacing (NHRCM20). The global climate simulations are prescribed by the past and future sea surface temperature (SST). Two future climate simulations are conducted so that the global-mean surface air temperature rise 2 K and 4 K from the pre-industrial period. The non-warming simulations are also conducted by MRI-AGCM and NHRCM20. We focus on the future changes in snowfall in Japan. In winter, the Sea of Japan coast experiences heavy snowfall due to East Asian winter monsoon. The cold and dry air from the continent obtains abundant moisture from the warm Sea of Japan, causing enormous amount of snowfall especially in the mountainous area. The NHRCM20 showed winter total snowfall decreases in the most parts of Japan. In contrast, extremely heavy daily snowfall could increase at mountainous areas in the Central Japan and Northern parts of Japan when strong cold air outbreak occurs and the convergence zone appears over the Sea of Japan. The warmer Sea of Japan in the future climate could supply more moisture than that in the present climate, indicating that the cumulus convections could be enhanced around the convergence zone in the Sea of Japan. However, the horizontal resolution of 20 km is not enough to resolve Japan`s complex topography. Therefore, dynamical downscaling with 5 km grid spacing (NHRCM05) is also conducted using NHRCM20. The NHRCM05 does a better job simulating the regional boundary of snowfall and shows more detailed changes in future snowfall characteristics. The future changes in total and extremely heavy snowfall depend on the regions, elevations, and synoptic conditions around Japan.

Satellite tracking of the migration of Whooper Swans Cygnus cygnus wintering in Japan

USGS Publications Warehouse

Shimada, Tetsuo; Yamaguchi, Noriyuki M.; Hijikata, N.; Hiraoka, Emiko N.; Hupp, Jerry W.; Flint, Paul L.; Tokita, Ken-ichi; Fujita, Go; Uchida, Kiyoshi; Sato, F.; Kurechi, Masayuki; Pearce, John M.; Ramey, Andy M.; Higuchi, Hiroyoshi

2014-01-01

We satellite-tracked Whooper Swans Cygnus cygnus wintering in northern Japan to document their migration routes and timing, and to identify breeding areas. From 47 swans that we marked at Lake Izunuma-Uchinuma, Miyagi Prefecture, northeast Honshu, and at Lake Kussharo, east Hokkaido, we observed 57 spring and 33 autumn migrations from 2009-2012. In spring, swans migrated north along Sakhalin Island from eastern Hokkaido using stopovers in Sakhalin, at the mouth of the Amur River and in northern coastal areas of the Sea of Okhotsk. They ultimately reached molting/breedmg areas along the Indigirka River and the lower Kolyma River in northern Russia. In autumn, the swans basically reversed the spring migration routes. We identified northern Honshu, eastern Hokkaido, coastal areas in Sakhalin, the lower Amur River and northern coastal areas of the Sea of Okhotsk as the most frequent stopover sites, and the middle reaches of the Indigirka and the lower Kolyma River as presumed breeding sites. Our results are helpful in understanding the distribution of the breeding and stopover sites of Whooper Swans wintering in Japan and in identifying their major migration habitats. Our findings contribute to understanding the potential transmission process of avian influenza viruses potentially carried by swans, and provide information necessary to conserve Whooper Swans in East Asia.

First JECSS Workshop

NASA Astrophysics Data System (ADS)

Ichiye, Takashi

The first Japan and East China Seas Study (JECSS) workshop convened at Tsukuba University, about 60 km north of Tokyo, Japan, June 1-4, 1981, to assess hydrographic data, review descriptive and theoretical Work, and promote future cooperation for studying the Japan Sea and East China Sea and marginal seas of the Western North Pacific Ocean. The conveners were Takashi Ichiye of Texas A&M University and Kenzo Takano of Tsukuba University, and the workshop was funded by the Hidaka Foundation, which was founded by Koji Hidaka, patriarch of dynamic oceanography in Japan.There were 41 participants: seven from the United States, six from Korea, one from the Peoples Republic of China, and 27 from Japan. Twenty-four papers were presented, and topics included the Japan Sea, the East China Sea, and marginal seas in general. Subjects concerned descriptive physical oceanography; internal waves, tides, and shelf waves; circulation modeling; data assessment; remote sensing; and sedimentology and marine chemistry. The seasonal change of the Tsushima Current, a branch of the Kuroshio in the Japan Sea, was determined by the Tohoku University group; preliminary results of the NOAA R/V Oceanographer cruise in Spring 1980 were presented; and the numerical modeling of the Japan Sea circulation, the tides of the Yellow Sea, and the barotropic current of the East China Sea were discussed. The papers presented will be published in 1982 in La Mer, a journal of the Japanese-French Oceanographical Society.

Orbital time scale records of Asian eolian dust from the Sea of Japan since the early Pliocene

NASA Astrophysics Data System (ADS)

Zhang, Wenfang; De Vleeschouwer, David; Shen, Ji; Zhang, Zeke; Zeng, Lin

2018-05-01

A high-resolution potassium content record of sediments from Integrated Ocean Drilling Program (IODP) Site U1422 drilled in the northern Sea of Japan was employed to yield an astronomical timescale for this ∼205 m thick sedimentary archive. The K content was quantified using the natural gamma radiation (NGR) data routinely measured on DV JOIDES Resolution. The U1422 K (wt.%) series shows an increasing trend with time, which parallels the growth of North Hemisphere ice sheets since ∼4 Ma, as revealed by the global benthic foraminifer's oxygen isotope stack (LR04). We propose that K content variations reflect changes in the relative contributions of Asian eolian dust and volcanic weathering products, in response to changes in global ice volume. Using the shipboard age model, constrained by palaeomagnetism and nanofossils datums, we tuned the U1422 K content variations to the LR04 stack. Our tuned age model for site U1422 goes back to 3.9 Ma. The studied record indicates that Asian dust generation is enhanced during periods of global cooling. The synchronous variations between the U1422 K record and the LR04 stack also suggest that global cooling played a dominant role in promoting the central Asian aridification since ∼3.9 Ma, while the uplift of Tibetan Plateau plays a secondary role, considering many disagreements still exists between the timing and amplitude of the Qinghai-Tibetan uplift and the evolution of central Asian aridity since the early Pliocene.

Effects of Large-Scale Releases on the Genetic Structure of Red Sea Bream (Pagrus major, Temminck et Schlegel) Populations in Japan.

PubMed

Blanco Gonzalez, Enrique; Aritaki, Masato; Knutsen, Halvor; Taniguchi, Nobuhiko

2015-01-01

Large-scale hatchery releases are carried out for many marine fish species worldwide; nevertheless, the long-term effects of this practice on the genetic structure of natural populations remains unclear. The lack of knowledge is especially evident when independent stock enhancement programs are conducted simultaneously on the same species at different geographical locations, as occurs with red sea bream (Pagrus major, Temminck et Schlegel) in Japan. In this study, we examined the putative effects of intensive offspring releases on the genetic structure of red sea bream populations along the Japanese archipelago by genotyping 848 fish at fifteen microsatellite loci. Our results suggests weak but consistent patterns of genetic divergence (F(ST) = 0.002, p < 0.001). Red sea bream in Japan appeared spatially structured with several patches of distinct allelic composition, which corresponded to areas receiving an important influx of fish of hatchery origin, either released intentionally or from unintentional escapees from aquaculture operations. In addition to impacts upon local populations inhabiting semi-enclosed embayments, large-scale releases (either intentionally or from unintentional escapes) appeared also to have perturbed genetic structure in open areas. Hence, results of the present study suggest that independent large-scale marine stock enhancement programs conducted simultaneously on one species at different geographical locations may compromise native genetic structure and lead to patchy patterns in population genetic structure.

Detection of low numbers of microplastics in North Sea fish using strict quality assurance criteria.

PubMed

Hermsen, Enya; Pompe, Renske; Besseling, Ellen; Koelmans, Albert A

2017-09-15

We investigated 400 individual fish of four North Sea species: Atlantic Herring, Sprat, Common Dab, and Whiting on ingestion of >20μm microplastic. Strict quality assurance criteria were followed in order to control contamination during the study. Two plastic particles were found in only 1 (a Sprat) out of 400 individuals (0.25%, with a 95% confidence interval of 0.09-1.1%). The particles were identified to consist of polymethylmethacrylate (PMMA) through FTIR spectroscopy. No contamination occurred during the study, showing the method applied to be suitable for microplastic ingestion studies in biota. We discuss the low particle count for North Sea fish with those in other studies and suggest a relation between reported particle count and degree of quality assurance applied. Microplastic ingestion by fish may be less common than thought initially, with low incidence shown in this study, and other studies adhering to strict quality assurance criteria. Copyright © 2017 Elsevier Ltd. All rights reserved.

Field Geometry During the Iceland Basin Event Observed from the North Atlantic Ocean, North Pacific Ocean and the South China Sea