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901.
902.
A. V. Vivchar K. B. Moiseenko R. A. Shumskii A. I. Skorokhod 《Izvestiya Atmospheric and Oceanic Physics》2009,45(3):302-313
The task of identifying climatically significant regional anthropogenic emissions and estimating their contribution to the variability of nitrogen oxides observed at a monitoring station is considered on the basis of NO and NO2 surface concentrations measured at the Zotino background observation station (60°26′ N, 89°24′ E, Krasnoyarsk Territory). The approach used is based on an estimation of the conditional probability of polluted air arriving from individual regions by using the results of calculating backward Lagrangian trajectories in the lower troposphere. It is established that the contribution of air masses supplied from industrial regions in the south of the Krasnoyarsk Territory to episodes of high concentrations of nitrogen oxides (>0.7 ppb) is larger than the contribution from cities and towns located in the south of Western Siberia. The results indicate that anthropogenic sources of pollution substantially affect the balance of minor gases in the lower troposphere on a regional scale and that this factor must be taken into account when observational data from the Zotino background station are analyzed and interpreted. 相似文献
903.
K.H. Brink R.C. Beardsley R. Limeburner J.D. Irish M. Caruso 《Progress in Oceanography》2009,82(3):191-223
In conjunction with the GLOBEC (Global Ocean Ecosystems Dynamics) program, measurements of moored currents, temperature and salinity were made during 1994–1999 at locations in 76 m of water along the southern flank of Georges Bank and at the Northeastern Peak. The measurements concentrate on the biologically crucial winter and spring periods, and coverage during the fall is usually poorer.Current time series were completely dominated by the semidiurnal M2 tidal component, while other tidal species (including the diurnal K1 component) were also important. There was a substantial wind-driven component of the flow, which was linked, especially during the summer, to regional–scale response patterns. The current response at the Northeast Peak was especially strong in the 3–4 days period band, and this response is shown to be related to an amplifying topographic wave propagating eastward along the northern flank. Monthly mean flows on the southern flank are southwestward throughout the year, but strongest in the summertime. The observed tendency for summertime maximum along-bank flow to occur at depth is rationalized in terms of density gradients associated with a near-surface freshwater tongue wrapping around the Bank.Temperature and salinity time series demonstrate the presence, altogether about 25% of the time, of a number of intruding water masses. These intrusions could last anywhere from a couple days up to about a month. The sources of these intrusions can be broadly classified as the Scotian Shelf (especially during the winter), the Western Gulf of Maine (especially during the summer), and the deeper ocean south of Georges Bank (throughout the year). On longer time scales, the temperature variability is dominated by seasonal temperature changes. During the spring and summer, these changes are balanced by local heating or cooling, but wintertime cooling involves advective lateral transports as well. Salinity variations have weak, if any, seasonal variability, but are dominated by interannual changes that are related to regional- or basin-scale changes.All considered, Georges Bank temperature and salinity characteristics are found to be highly dependent on the surrounding waters, but many questions remain, especially in terms of whether intrusive events leave a sustained impact on Bank waters. 相似文献
904.
Dissolved aluminium and the silicon cycle in the Arctic Ocean 总被引:1,自引:0,他引:1
Concentrations of dissolved (0.2 µm filtered) aluminium (Al) have been determined for the first time in the Eurasian part of the Arctic Ocean over the entire water column during expedition ARK XXII/2 aboard R.V. Polarstern (2007). An unprecedented number of 666 samples was analysed for 44 stations along 5 ocean transects. Dissolved Al in surface layer water (SLW) was very low, close to 1 nM, with lowest SLW concentrations towards the Canadian part of the Arctic Ocean and higher values adjacent to and in the shelf seas. The low SLW concentrations indicate no or little influence from aeolian dust input. Dissolved Al showed a nutrient-type increase with depth up to 28 nM, but large differences existed between the different deep Arctic basins. The differences in concentrations of Al between water masses and basins could largely be related to the different origins of the water masses. In the SLW and intermediate water layers, Atlantic and Pacific inflows were of importance. Deep shelf convection appeared to influence the Al distribution in the deep Eurasian Basin. The Al distribution of the deep Makarov Basin provides evidence for Eurasian Basin water inflow into the deep Makarov Basin. A strong correlation between Al and Silicon (Si) was observed in all basins. This correlation and the nutrient-like profile indicate a strong biological influence on the cycling and distribution of Al. The biological influence can be direct by the incorporation of Al in biogenic silica, indirect by preferential scavenging of Al onto biogenic siliceous particles, or by a combination of both processes. From the slope of the overall Al–Si relationship in the intermediate water layer (AIDW; ~ 200–2000 m depth), an Al/Si ratio of 2.2 atoms Al per 1000 atoms Si was derived. This ratio is consistent with the range of previously reported Al/Si uptake ratio in biogenic opal frustules of diatoms. In the deepest waters (>2000 m depth) a steeper slope of the Al–Si relationship of 7.4 to 13 atoms Al per 1000 atoms Si likely results from entrainment of cold shelf water into the deep basins, carrying the signal of dissolution of terrigenous particles with a much higher Al:Si ratio of crustal abundance. Only a small enrichment with such crustal Al and Si component may readily account for the higher Al:Si slope in the deepest waters. 相似文献
905.
Active tectonic morphology and submarine deformation of the northern Gulf of Eilat/Aqaba from analyses of multibeam data 总被引:1,自引:0,他引:1
Gideon Tibor Tina M. Niemi Zvi Ben-Avraham Abdallah Al-Zoubi Ronnie A. Sade John K. Hall Gal Hartman Emad Akawi Abdelrahmem Abueladas Rami Al-Ruzouq 《Geo-Marine Letters》2010,30(6):561-573
A high-resolution marine geophysical study was conducted during October-November 2006 in the northern Gulf of Aqaba/Eilat,
providing the first multibeam imaging of the seafloor across the entire gulf head spanning both Israeli and Jordanian territorial
waters. Analyses of the seafloor morphology show that the gulf head can be subdivided into the Eilat and Aqaba subbasins separated
by the north-south-trending Ayla high. The Aqaba submarine basin appears starved of sediment supply, apparently causing erosion
and a landward retreat of the shelf edge. Along the eastern border of this subbasin, the shelf is largely absent and its margin
is influenced by the Aqaba Fault zone that forms a steep slope partially covered by sedimentary fan deltas from the adjacent
ephemeral drainages. The Eilat subbasin, west of the Ayla high, receives a large amount of sediment derived from the extensive
drainage basins of the Arava Valley (Wadi ’Arabah) and Yutim River to the north–northeast. These sediments and those entering
from canyons on the south-western border of this subbasin are transported to the deep basin by turbidity currents and gravity
slides, forming the Arava submarine fan. Large detached blocks and collapsed walls of submarine canyons and the western gulf
margin indicate that mass wasting may be triggered by seismic activity. Seafloor lineaments defined by slope gradient analyses
suggest that the Eilat Canyon and the boundaries of the Ayla high align along north- to northwest-striking fault systems—the
Evrona Fault zone to the west and the Ayla Fault zone to the east. The shelf–slope break that lies along the 100 m isobath
in the Eilat subbasin, and shallower (70–80 m isobaths) in the Aqaba subbasin, is offset by approx. 150 m along the eastern
edge of the Ayla high. This offset might be the result of horizontal and vertical movements along what we call the Ayla Fault
on the east side of the structure. Remnants of two marine terraces at 100 m and approx. 150 m water depths line the southwest
margin of the gulf. These terraces are truncated by faulting along their northern end. Fossil coral reefs, which have a similar
morphological appearance to the present-day, basin margin reefs, crop out along these deeper submarine terraces and along
the shelf–slope break. One fossil reef is exposed on the shelf across the Ayla high at about 60–63 m water depth but is either
covered or eroded in the adjacent subbasins. The offshore extension of the Evrona Fault offsets a fossil reef along the shelf
and extends south of the canyon to linear fractures on the deep basin floor. 相似文献
906.
Regularities of oxygen and hydrogen sulfide are examined, using the method of spatial isopycnic analysis. The contribution
that ventilation of winter-time surface waters over the domes of cyclonic gyres makes to the transfer of O2 towards the upper boundary of the constant pycnocline and to the oxicline layer is demonstrated. The paper provides spatial
scales of this phenomenon and indicates the areas where the upper boundary of the anoxic layer in the Black Sea, relative
to the conventional density, is located much higher compared with the rest of the sea. The suboxic zone is shown to be a specific
feature of the O2/H2S distribution in the Black Sea waters, typical, at least, of the northern part of the basin. Analysis of the suboxic spatial
variability in the vertical has been conducted.
Translated by Vladimir A. Puchkin. 相似文献
907.
- In order to employ cost effective frequency domain analysis for off-shore structures treatment of hydrodynamic loading is essential. Drag and inertia dominated, resonating and antiresonating cases under random sea states are analyzed to highlight the implications and relative merits of four salient linearization techniques. 相似文献
908.
On the southwestern Barents Sea shelf, sediments containing gas hydrates that overlie free gas have been inferred from multichannel
seismic data. The volume of suspected gas hydrate is tentatively estimated to about 1.9×108 m3. The gas hydrate zone probably formed from thermogenic gas leaking from a deeper source. The hydrate zone may have thickened
during the Neogene by including gas originally trapped as free gas below the hydrate following a significant downward migration
of the isotherms caused by erosion and/or subsidence. Within the present oceanographic conditions, gas hydrate is suspected
to be stable or slowly decomposing.
Received: 20 December 1996 / Revision received: 20 August 1997 相似文献
909.
In this paper the probability of green water occurrence is investigated by taking into account the threshold of the vertical relative motion exceeding the freeboard. The number of wetting of the unit/vessel is predicted using probabilistic method. This paper compares the significant load, due to shipping of green water with the works of other researchers, and the loads are found to be close with the results presented in this paper. There is no direct relation between the velocities in the waves and the water velocity over the deck. The water velocities around the bow are heavily distributed by the presence of the bow. This scenario makes the flow very complex for schematic modelling. 相似文献
910.
Laurence P. Madin Stephen M. Bollens Erich Horgan Mari Butler Jeffrey Runge Barbara K. Sullivan Grace Klein-Macphee Edward Durbin Ann G. Durbin Donna Van Keuren Stphane Plourde Ann Bucklin M. Elizabeth Clarke 《Deep Sea Research Part II: Topical Studies in Oceanography》1996,43(7-8)
Hydroids are typically attached, benthic cnidarians that feed on a variety of small prey. During sampling on Georges Bank in spring 1994, we found huge numbers of hydroids suspended in the plankton. They fed on young stages of copepods that are an important prey for fish, as well as on young fish themselves. Two independent methods were used to estimate feeding rates of the hydroids; both indicate that the hydroids are capable of consuming from 50% to over 100% of the daily production of young copepods. These results suggest that hydroids can have a profound effect on the population dynamics of zooplankton and young fish on Georges Bank. 相似文献