981 resultados para sea level change
Resumo:
From the distribution of oceanographic data (temperature and salinity) in both Arabian Gulf and Gulf of Oman, the steric components (thermal, haline and steric heights) are calculated for the upper 50m layer during different seasons. The analysis reveals relevant evidence, that temperature variations (thermal component) play a role in the fluctuations of sea level within the investigated area. The salinity variations (haline component) is only significant near the entrance. The sea level variations due to density (steric component) is low during winter and spring and high during summer and autumn. The steric height is always lower in the northern and central regions of Arabian Gulf and higher in eastern region of Arabian Gulf and in the Gulf of Oman, i.e. the surface water must flow from the Gulf of Oman to the Arabian Gulf. The steric sea level gradient around the Strait of Hormuz are 0.04 cm/km in winter, 0.04 cm/km in spring, and 0.025 cm/km in summer and 0.014 cm/km in autumn.
Resumo:
National Natural Science Foundation of China (NSFC) ; [2007CB411600]; [30530120]
Resumo:
Based on more than 4000 km 2D seismic data and seismic stratigraphic analysis, we discussed the extent and formation mechanism of the Qiongdongnan deep sea channel. The Qiongdongnan deep sea channel is a large incised channel which extends from the east boundary of the Yinggehai Basin, through the whole Qiongdongnan and the Xisha trough, and terminates in the western part of the northwest subbasin of South China Sea. It is more than 570 km long and 4-8 km wide. The chaotic (or continuous) middle (or high) amplitude, middle (or high) continuity seismic facies of the channel reflect the different lithological distribution of the channel. The channel formed as a complex result of global sea level drop during early Pliocene, large scale of sediment supply to the Yinggehai Basin, inversion event of the Red River strike-slip fault, and tilted direction of the Qiongdongnan Basin. The large scale of sediment supply from Red River caused the shelf break of the Yinggehai Basin to move torwards the S and SE direction and developed large scale of prograding wedge from the Miocene, and the inversion of the Red River strike-slip fault induced the sediment slump which formed the Qiongdongnan deep sea channel.
Resumo:
This review paper provides a brief review on the development of ideas in the fields of the sea level change of the ECS (East China Sea), the history of the Yangtze River entering the sea and paleochannels in the shelf of the ECS since the Last Glacial Maximum (LGM). The paper summarizes two opposite theories about the Yangtze River entering the sea during the LGM. One theory is that the Yangtze River input a lacustrine in the north of Jiangsu province which was defunct in middle Holocene, and the river was once dry. The other was that the Yangtze River still existed and entered into the Okinawa Trough during the LGM, but scholars share different opinions on which course the river ran across and which place the river input the trough. This paper concludes future work is to study the evolution of the Yangtze River and the paleoclimate and the corresponding events as a whole from the view of regional and even global change, and more attention should be paid to the study on mud sediment, the Yangtze River's response to the changes in climate and sea-level, and the channel metamorphosis.
Resumo:
Satellite and in situ observations in the equatorial Atlantic Ocean during 2002-03 show dominant spectral peaks at 40-60 days and secondary peaks at 10-40 days in sea level and thermocline within the intraseasonal period band (10-80 days). A detailed investigation of the dynamics of the intraseasonal variations is carried out using an ocean general circulation model, namely, the Hybrid Coordinate Ocean Model (HYCOM). Two parallel experiments are performed in the tropical Atlantic Ocean basin for the period 2000-03: one is forced by daily scatterometer winds from the Quick Scatterometer (QuikSCAT) satellite together with other forcing fields, and the other is forced by the low-passed 80-day version of the above fields. To help in understanding the role played by the wind-driven equatorial waves, a linear continuously stratified ocean model is also used. Within 3 degrees S-3 degrees N of the equatorial region, the strong 40-60-day sea surface height anomaly (SSHA) and thermocline variability result mainly from the first and second baroclinic modes equatorial Kelvin waves that are forced by intraseasonal zonal winds, with the second baroclinic mode playing a more important role. Sharp 40-50-day peaks of zonal and meridional winds appear in both the QuikSCAT and Pilot Research Moored Array in the Tropical Atlantic (PIRATA) data for the period 2002-03, and they are especially strong in 2002. Zonal wind anomaly in the central-western equatorial basin for the period 2000-06 is significantly correlated with SSHA across the equatorial basin, with simultaneous/ lag correlation ranging from-0.62 to 0.74 above 95% significance. Away from the equator (3 degrees-5 degrees N), however, sea level and thermocline variations in the 40-60-day band are caused largely by tropical instability waves (TIWs). On 10-40-day time scales and west of 10 degrees W, the spectral power of sea level and thermocline appears to be dominated by TIWs within 5 degrees S-5 degrees N of the equatorial region. The wind-driven circulation, however, also provides a significant contribution. Interestingly, east of 10 W, SSHA and thermocline variations at 10 40- day periods result almost entirely from wind-driven equatorial waves. During the boreal spring of 2002 when TIWs are weak, Kelvin waves dominate the SSHA across the equatorial basin (2 degrees S-2 degrees N). The observed quasi-biweekly Yanai waves are excited mainly by the quasi-biweekly meridional winds, and they contribute significantly to the SSHA and thermocline variations in 1 degrees-5 degrees N and 1 degrees-5 degrees S regions.
Resumo:
Long-wave dynamics of the interannual variations of the equatorial Indian Ocean circulation are studied using an ocean general circulation model forced by the assimilated surface winds and heat flux of the European Centre for Medium-Range Weather Forecasts. The simulation has reproduced the sea level anomalies of the Ocean Topography Experiment (TOPEX)/Poseidon altimeter observations well. The equatorial Kelvin and Rossby waves decomposed from the model simulation show that western boundary reflections provide important negative feedbacks to the evolution of the upwelling currents off the Java coast during Indian Ocean dipole (IOD) events. Two downwelling Kelvin wave pulses are generated at the western boundary during IOD events: the first is reflected from the equatorial Rossby waves and the second from the off-equatorial Rossby waves in the southern Indian Ocean. The upwelling in the eastern basin during the 1997-98 IOD event is weakened by the first Kelvin wave pulse and terminated by the second. In comparison, the upwelling during the 1994 IOD event is terminated by the first Kelvin wave pulse because the southeasterly winds off the Java coast are weak at the end of 1994. The atmospheric intraseasonal forcing, which plays an important role in inducing Java upwelling during the early stage of an IOD event, is found to play a minor role in terminating the upwelling off the Java coast because the intraseasonal winds are either weak or absent during the IOD mature phase. The equatorial wave analyses suggest that the upwelling off the Java coast during IOD events is terminated primarily by western boundary reflections.
Resumo:
Ochotona curzoniae and Microtus oeconomus are the native mammals living on the Qinghai-TibetanPlateau of China. The molecular mechanisms of their acclimatization to the Plateau-hypoxia remain unclear. Expressions of hepatic hypoxia-inducible factor (HIF)-1 alpha, insulin-like growth factor-I (IGF-I)/IGF binding protein (BP)-1(IGFBP-1; including genes), and key metabolic enzymatic genes [lactate dehydrogenase (LDH)-A/isocitrate dehydrogenase (ICD)] are compared in Qinghai-Tibetan- Plateau mammals andsea- level mice after injection of CoCl2 (20, 40, or 60 mg/ kg) and normobaric hypoxia (16.0% O-2, 10.8% O-2, and 8.0% O-2) for 6 h, tested by histochemistry, Western blot analysis, ELISA, and RT-PCR. Major results are CoCl2 markedly increased 1) HIF-1 alpha only in mice, 2) hepatic and circulatory IGF-I in M. oeconomus, 3) hepatic IGFBP-1 in mice and O. curzoniae, and 4) LDH-A but reduced ICD mRNA in mice (CoCl2 20 mg/kg) but were unchanged in the Tibetan mammals. Normobaric hypoxia markedly 1) increased HIF-1 alpha and LDH-A mRNA in mice and M. oeconomus (8.0% O-2) not in O. curzoniae, and 2) reduced ICD mRNA in mice and M. oeconomus (8.0% O-2) not in O. curzoniae. Results suggest that 1) HIF-1 alpha responsiveness to hypoxia is distinct in lowland mice and plateau mammals, reflecting a diverse tolerance of the three species to hypoxia; 2) CoCl2 induces diversities in HIF-1, IGF-I/IGFBP-1 protein or genes in mice, M. oeconomus, and O. curzoniae. In contrast, HIF-1 mediates IGFBP-1 transcription only in mice and in M. oeconomus (subjected to severe hypoxia); 3) differences in IGF-I/IGFBP-1 expressions induced by CoCl2 reflect significant diversities in hormone regulation and cell protection from damage; and 4) activation of anaerobic glycolysis and reduction of Krebs cycle represents strategies of lowland-animals vs. the stable metabolic homeostasis of plateau- acclimatized mammals.
Resumo:
The strength of the North Atlantic Current (NAC) (based on sea-surface elevation sloped derived from altimeter data) is correlated with westerly winds (based on North Atlantic Oscillation [NAO] Index data over a nine year period [1992-2002] with 108 monthly values). The data time window includes the major change in climate forcing over the last 100 years (1995 to 1996). It is shown that the NAO Index can be used for early earning of system failure for the NAC. The correlation response or early warning time scale for western Europe and south England is six months. The decay scale for the NAC and Subtropical Gyre circulation is estimated as three years. Longer period altimeter elevation/circulation changes are discussed. The sea-surface temperature (SST) response of the North Sea to negative and positive NAO conditions is examined. The overall temperature response for the central North Sea to NAO index forcing, reflecting wind induced inflow, shelf circulation and local climate forcing, is similar to 5 months. In years with strong North Atlantic winter wind induced inflow, under marked NAO positive conditions, mean temperatures ( similar to 10.5 degree C) are about 1 degree C warmer than under negative conditions. In 1996 under extreme negative winter NAO conditions, the North Sea circulation stopped, conditions near the Dogger Bank became more continentally influenced and the winter (March) temperature fell to 3.1 degree C whereas in 1995 under NAO positive winter conditions the minimum temperature was 6.4 degree C (February). Seasonal advance of North Atlantic and North Sea temperature is derived in relation to temperature change. Temperature change and monthly NAO Index are discussed with respect to phytoplankton blooms, chlorophyll-a measurements, ocean colour data and the anomalous north-eastern Atlantic 2002 spring/summer bloom SeaWiFS chlorophyll concentrations.
Resumo:
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.
Resumo:
The paper Bereavement: A behavioural process (Dillenburger & Keenan, 1994) was first published within a vacuum of behaviour analytic thinking or research in this field. The paper was meant to be a first step in stimulating others to contribute to the understanding of one of the most complex, yet most universal, human behavioural processes. The only behaviour analyst addressing the issues directly was Calkin (1990). Recently, after reading our original 1994 paper, Beth Sulzer-Azaroff suggested that we should solicit comments directly from the behaviour analytic community. This we did with the help of Erik Arntzen and now the reprint and the commentaries in this edition of the European Journal of Behaviour Analysis (EJBA) fully embrace and extend the contribution of behaviour analysis to the understanding of the behavioural process that is bereavement.