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Noel Perez Rolando Cardenas Osmel Martin Leiva-Mora Michel 《Astrophysics and Space Science》2013,346(2):327-331
We perform a quantitative assessment for the potential for photosynthesis in hydrothermal vents in the deep ocean. The photosynthetically active radiation in this case is from geothermal origin: the infrared thermal radiation emitted by hot water, at temperatures ranging from 473 up to 673 K. We find that at these temperatures the photosynthetic potential is rather low in these ecosystems for most known species. However, species which a very high efficiency in the use of light and which could use infrared photons till 1300 nm, could achieve good rates of photosynthesis in hydrothermal vents. These organisms might also thrive in deep hydrothermal vents in other planetary bodies, such as one of the more astrobiologically promising Jupiter satellites: Europa. 相似文献
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Observations indicate that since the 1970s Equatorial Atlantic sea surface temperature (SST) variations in boreal summer tend to modulate El Niño in the following seasons, indicating that the Atlantic Ocean can have importance for predicting the El Niño–Southern Oscillation (ENSO). The cause of the change in the recent decades remains unknown. Here we show that in the Bergen Climate Model (BCM), a freshwater forced weakening of the Atlantic meridional overturning circulation (AMOC) results in a strengthening of the relation between the Atlantic and the Pacific similar to that observed since the 1970s. During the weakening AMOC phase, SST and precipitation increase in the central Equatorial Atlantic, while the mean state of the Pacific does not change significantly. In the Equatorial Atlantic the SST variability has also increased, with a peak in variability in boreal summer. In addition, the characteristic timescales of ENSO variability is shifted towards higher frequencies. The BCM version used here is flux-adjusted, and hence Atlantic variability is realistic in contrast to in many other models. These results indicate that in the BCM a weakening AMOC can change the mean background state of the Tropical Atlantic surface conditions, enhancing Equatorial Atlantic variability, and resulting in a stronger relationship between the Tropical Atlantic and Pacific Oceans. This in turn alters the variability in the Pacific. 相似文献
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Future climate trends for the Southwestern US, based on the climate models included in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report, project a more arid climate in the region during the 21st century. However, future climate variability associated with El Niño Southern Oscillation (ENSO)—an important driver for winter climate variability in the region—have not been addressed. In this work we evaluate future winter ENSO projections derived from two selected IPCC models, and their effect on Southwestern US climate. We first evaluate the ability of the IPCC coupled models to represent the climate of the Southwest, selecting the two models that best capture seasonal precipitation and temperature over the region and realistically represent ENSO variability (Max Planck Institute’s ECHAM5 and the UK Met Office HadCM3). Our work shows that the projected future aridity of the region will be dramatically amplified during La Niña conditions, as anomalies over a drier mean state, and will be characterized by higher temperatures (~0.5°C) and lower precipitation (~3 mm/mnt) than the projected trends. These results have important implications for water managers in the Southwest who must prepare for more intense winter aridity associated with future ENSO conditions. 相似文献
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Without detailed reconnaissance, consistent representation of hurricane-like vortices in initial conditions for operational prediction and research simulations still remains elusive. It is thus often necessary, particularly for high-resolution intensity forecasting, to use synthetic tropical cyclone circulations to initialize forecast models. Variants on three commonly used surface pressure profiles are evaluated for possible use. Enhancements to the original profiles are proposed that allows definition of both the inner-core and outer circulation. The latter improvement creates a vortex more consistent with the estimated outer structure which sometimes appears to be crucial to the evolving intensity of the storm. It also allows smoother merging of the synthetic vortex with the environment. Comparisons of the profiles against (a) structure estimates, (b) each other, (c) structures obtained via conservation of angular momentum, and (d) observed vorticity structures, suggest that a new enhanced Fujita profile best represents real TC structures. Student-t tests indicate that improved fitting to the observations is statistically significant. 相似文献
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Observations indicate that the Atlantic zonal mode influences El Ni?o Southern Oscillation (ENSO) in the Pacific, as already suggested in previous studies. Here we demonstrate for the first time using partial coupled experiments that the Atlantic zonal mode indeed influences ENSO. The partial coupling experiments are performed by forcing the coupled general circulation model (ECHAM5/MPI-OM) with observed sea surface temperature (SST) in the Tropical Atlantic, but with full air-sea coupling allowed in the Pacific and Indian Ocean. The ensemble mean of a five member simulation reproduces the observational results well. Analysis of observations, reanalysis, and coupled model simulations all indicate the following mechanism: SST anomalies associated with the Atlantic zonal mode affect the Walker Circulation, driving westward wind anomalies over the equatorial Pacific during boreal summer. The wind stress anomalies increase the east-west thermocline slope and enhance the SST gradient across the Pacific; the Bjerknes positive feedback acts to amplify these anomalies favouring the development of a La Ni?a-like anomalies. The same mechanisms act for the cold phase of Atlantic zonal mode, but with opposite sign. In contrast to previous studies, the model shows that the influence on ENSO exists before 1970. Furthermore, no significant influence of the Tropical Atlantic on the Indian Monsoon precipitation is found in observation or model. 相似文献
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The Gulf of Cadiz spans the plate boundary between Africa and Eurasia west of the Betic-Rif mountain belt. A narrow east dipping subduction zone descends beneath the Gulf of Cadiz and the straits of Gibraltar. The deep crustal structure of the Gulf and the adjacent SW Iberian and Moroccan margins is constrained by numerous multi-channel seismic reflection and wide-angle seismic surveys. A compilation of these existing studies is presented in the form of depth to basement, sediment thickness, depth to Moho and crustal thickness maps. These structural maps image an E-W trending trough, with thin (< 10 km) crust beneath the Gulf of Cadiz. This trough is filled by an eastward thickening wedge of sediments, reaching a thickness of 10-15 km in the eastern Gulf. These sediments are tectonically deformed, primarily along a series of westward-vergent thrust faults and represent a 200-250 km wide accretionary wedge. The northern and especially the southern limits of the accretionary wedge are marked by sharp morphological lineaments showing evidence of recent deformation. These tectonic limits are situated in an internal position with respect to the Miocene deformation front (external Betic and Rif allocthons), which has been abandoned. At the western boundary of the accretionary wedge, near the adjacent Seine and Horseshoe abyssal plains, an E-W trending basement high (Coral Patch Ridge) can be seen indenting the deformation front in an asymmetric manner. Analog modeling is performed using granular materials accreted against a semicircular backstop (representing the basement of the Rif and Betic mountain belts). The modeling initially produces a symmetric, arcuate accretionary wedge. The ensuing collision of an oblique rigid indenter retards accretion on one side, resulting in an embayment and a locally steeper deformation front. The deformation pattern observed in morphology and high-resolution seismic profiles suggests the accretionary wedge and underlying subduction system is still active. The implications of active subduction for the source region of the 1755 Lisbon earthquake and the regional seismic hazard assessment are discussed. 相似文献