挪威近海Storegga滑坡侧翼麻点的成因及烟囱构造

1 Storegga滑坡崖地质背景 挪威的陆缘形态以Storegga滑坡崖为标志,该滑坡崖是由一系列巨大的全新世陡坡崩塌形成的.14C测年证实,最近一次崩塌出现在约7.2 ka以前.     

Investigation of the mechanism of the long-term evolution of the carbon cycle in the ecosystem of the Sevastopol bay

We analyze the components of the carbon system of the Sevastopol bay waters and the balance of main sediment-forming substances using the data of field investigations in 1998–2008. The interannual variations of total inorganic carbon and the equilibrium partial pressure of carbon dioxide in the bay water are noted. An increase in the flux of carbon dioxide into the bay and in the content of organic carbon in bottom sediments is revealed, and an explanation of this phenomenon is given. The priority accumulation of organic carbon in the sediments of the bay is established. We assess the interannual variation in the relative abundances of organic and inorganic carbon as an index of the carbon cycle stability.     

Numerical studies of methane production from Class 1 gas hydrate accumulations enhanced with carbon dioxide injection

Class 1 gas hydrate accumulations are characterized by a permeable hydrate-bearing interval overlying a permeable interval with mobile gas, sandwiched between two impermeable intervals. Depressurization-induced dissociation is currently the favored technology for producing gas from Class 1 gas hydrate accumulations. The depressurization production technology requires heat transfer from the surrounding environment to sustain dissociation as the temperature drops toward the hydrate equilibrium point and leaves the reservoir void of gas hydrate. Production of gas hydrate accumulations by exchanging carbon dioxide with methane in the clathrate structure has been demonstrated in laboratory experiments and proposed as a field-scale technology. The carbon dioxide exchange technology has the potential for yielding higher production rates and mechanically stabilizing the reservoir by maintaining hydrate saturations. We used numerical simulation to investigate the advantages and disadvantages of using carbon dioxide injection to enhance the production of methane from Class 1 gas hydrate accumulations. Numerical simulations in this study were primarily concerned with the mechanisms and approaches of carbon dioxide injection to investigate whether methane production could be enhanced through this approach. To avoid excessive simulation execution times, a five-spot well pattern with a 500-m well spacing was approximated using a two-dimensional domain having well boundaries on the vertical sides and impermeable boundaries on the horizontal sides. Impermeable over- and under burden were included to account for heat transfer into the production interval. Simulation results indicate that low injection pressures can be used to reduce secondary hydrate formation and that direct contact of injected carbon dioxide with the methane hydrate present in the formation is limited due to bypass through the higher permeability gas zone.     

Relative dispersion in the Liguro-Provençal basin: From sub-mesoscale to mesoscale

Relative dispersion in the Liguro-Provençal basin (a subregion of the Mediterranean Sea) is investigated using clusters of surface drifters deployed during two Marine Rapid Environment Assessment (MREA) experiments covering different months in 2007 and 2008, respectively. The clusters have initial radii of less than 1 km, or an order of magnitude below a typical deformation radius (approximately 10-20 km). The data set consists of 45 original pairs and more than 50 total pairs (including chance ones) in the spatial range between 1 and 200 km. Relative dispersion is estimated using the mean square separation of particle pairs and the Finite Scale Lyapunov Exponents (FSLEs). The two metrics show broadly consistent results, indicating in particular a clear exponential behaviour with an e-folding time scale between 0.5 and 1 days, or Lyapunov exponent ?? in the range of 0.7-1 days⁻¹. The exponential phase extends for 4-7 days in time and between 1 and 10-20 km in separation space. To our knowledge, this is only the third time that an exponential regime is observed in the world ocean from drifter data. This result suggests that relative dispersion in the Liguro-Provençal basin is nonlocal, namely controlled mainly by mesoscale dynamics, and that the effects of the sub-mesoscale motions are negligible in comparison. NCOM model results are used to complement the data and to quantify errors arising from the sparse sampling in the observations.     

Formation rates of Subantarctic mode water and Antarctic intermediate water within the South Pacific

The formation of Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) significantly contributes to the total uptake and storage of anthropogenic gases, such as CO₂ and chlorofluorocarbons (CFCs), within the world's oceans. SAMW and AAIW formation rates in the South Pacific are quantified based on CFC-12 inventories using hydrographic data from WOCE, CLIVAR, and data collected in the austral winter of 2005. This study documents the first wintertime observations of CFC-11 and CFC-12 saturations with respect to the 2005 atmosphere in the formation region of the southeast Pacific for SAMW and AAIW. SAMW is 94% and 95% saturated for CFC-11 and CFC-12, respectively, and AAIW is 60% saturated for both CFC-11 and CFC-12. SAMW is defined from the Subantarctic Front to the equator between potential densities 26.80-27.06 kg m⁻³, and AAIW is defined from the Polar Front to 20°N between potential densities 27.06-27.40 kg m⁻³. CFC-12 inventories are 16.0×10⁶ moles for SAMW and 8.7×10⁶ moles for AAIW, corresponding to formation rates of 7.3±2.1 Sv for SAMW and 5.8±1.7 Sv for AAIW circulating within the South Pacific. Inter-ocean transports of SAMW from the South Pacific to the South Atlantic are estimated to be 4.4±0.6 Sv. Thus, the total formation of SAMW in the South Pacific is approximately 11.7±2.2 Sv. These formation rates represent the average formation rates over the major period of CFC input, from 1970 to 2005. The CFC-12 inventory maps provide direct evidence for two areas of formation of SAMW, one in the southeast Pacific and one in the central Pacific. Furthermore, eddies in the central Pacific containing high CFC concentrations may contribute to SAMW and to a lesser extent AAIW formation. These CFC-derived rates provide a baseline with which to compare past and future formation rates of SAMW and AAIW.     

On the wind conditions of a shallow as a factor of the formation of satellite images of the Sea (Using the example of the South Caspian Sea)

Based on the scatterometer QuickScat wind data and the water-leaving radiances from the ocean color scanner SeaWiFS data for 2000–2004, we composed a pair of mean annual images of a testing site in the South Caspian Sea under conditions of west-bound and east-bound winds corresponding to the offset and onset state of the shallows in the east of the testing site. It was established that both the “offset” and “onset” radiances grow shorewards, but the former becomes about twice as large as the latter in the middle of the shallows with 10–15 m of water, while their difference tends to zero at the seaward and coastal boundaries of the shallow. These and other findings are hypothetically attributable to the inclination of the sea floor of the shallows, due to which the surfacing of bottom sediments resuspended by the drift current takes less time under the “offset” wind conditions than under the “onset” ones. The study’s results indicate that the effect of the bottom sediments resuspension upon the structure of the images of the marine shallows is universal in character and needs to be taken into account to improve the bio-optical algorithms for estimating the admixtures in the thickness of the shallows from the satellite data.     

Reference sediment core and paleogeography of the underwater Slupsk river foredelta in the Baltic Sea

Core Psd-590 (length 947 cm, water depth 124 m) penetrated the entire sequence of marine (Littorina) mud (730 cm) and stopped in gray lacustrine (Ancylus) clays with hydrotroilitic films. The Littorina mud is gray-colored, microlaminated in the interval of 730 to 700 cm, and dark gray with hydrotoilitic films and obscure microlamination higher in the section. According to the diatom data, typical marine sediments begin at the level of 620 cm, while the lithological-geochemical data indicate this change at the level of 730 cm. This level is marked by a considerable increase in the concentrations of SiO_2amorph, CO₂, C_org, and Mn in the sediments. In the interval of 730 to 620 cm, diatoms are represented by both freshwater and brackish-water species. The Littorina transgression began in the form of individual flows of saline North Sea waters into the Baltic Sea, which is evident from the microlamination and sharp peaks in the concentrations of the chemical elements. The transgression exhibits two weakening and one strengthening (core interval of 380 to 220 cm) stages; the latter was marked by the maximal water salinity. The post-Littorina mud contains molluscan shells and fish bones and is enriched in the fraction of 0.05–0.01 mm. The microlaminated Littorina mud was deposited during periods with stagnant conditions in the bottom water layer, while the homogenous sediments accumulated during periods of its aeration.     

A high-resolution,multi-channel,over-sea-ice seismic reflection survey over the Mackay Sea Valley,Granite Harbor,Antarctica

In the austral summer of 2007, 20.5 km of high-resolution over-sea-ice seismic reflection data were collected in the Granite Harbor region of southern McMurdo Sound over the Mackay Sea Valley. The goal of the survey was to image thin pelagic sediment deposited in the Mackay Sea Valley after the Last Glacial Maximum. A generator–injector air gun was lowered beneath the sea ice through holes drilled by an auger drill system. The recording system was a 60 channel snow streamer with vertically oriented gimbaled geophones spaced 25 m apart. Unique problems in the over-sea-ice seismic reflection survey—noise from the ice column flexing and timing delays caused by trapped air at previous shot points—were overcome to improve the quality of the seismic data. The Mackay Sea Valley survey produced seismic data with a vertical resolution of 6.3 m. The processed seismic data show pelagic sediment thickness of up to 50 m within the Mackay Sea Valley with some locations showing possible older sediments beneath the pelagic sediment layer.     

Habitability analyses of aquatic bacteria

Habitability is defined as an ability of an organism to inhabit different environments. Habitability of organisms, however, cannot be inferred from analyses such as a whole genome or community structures. A recently developed database, the MetaMetaDB, gives us information from what kind of environments one particular 16S rRNA sequence data has ever been obtained, and thus enables us to infer the habitability of the bacterium in question. In order to check the applicability of this database to study the habitability of aquatic bacteria, samples collected at two Naka River stations, one estuarine station from Naka River Estuary, two coastal stations at Oarai in Ibaraki Prefecture, Japan and one station in the Kuroshio Current of the western North Pacific were examined. The phylotypes were tracked against the MetaMetaDB and it was reasonably found that the low-salinity stations were dominated by sequences with “freshwater and groundwater”, “human” and “wastewater” habitat identities, while the high-salinity stations were dominated by those with a “marine” identity. The phylotypes of low-salinity stations with a particular habitat identity were absent or rare in the high-salinity stations and vice versa. The MetaMetaDB also showed that sequences of Cyanobacteria or related phylogenetic groups may be present in the human gut, as well as the probable distribution of the relatives (ancestors/descendants/siblings) of some bacteria. These overall findings proved that the MetaMetaDB is useful as a new tool to infer microbial habitability and it gives us new information on the possible origin and ecology of microorganisms in the environments.