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In this study, we propose to estimate the steric sea-level variations over a < 2-year period (April 2002 through December
2003) by combining global mean sea level (GMSL) based on Topex/Poseidon (T/P) altimetry with time-variable geoid averaged
over the oceans, as observed by the GRACE (Gravity Recovery and Climate Experiment) satellite. In effect, altimetry-derived
GMSL changes results from two contributions: Steric (thermal plus salinity) effects due to sea water density change and ocean
mass change due to water exchange with atmosphere and continents. On the other hand, GRACE data over the oceans provide the
ocean mass change component only. The paper first discusses the corrections to apply to the GRACE data. Then the steric contribution
to the GMSL is estimated using GRACE and T/P data. Comparison with available thermal expansion based on in situ hydrographic
data is performed.
G. García: On leave from Space Geodesy Laboratory, Applied Mathematics Department, EPS, University of Alicante, Alicante,
Spain. 相似文献
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L. Snchez-Velasco M.F. Lavín M. Peguero-Icaza C.A. Len-Chvez F. Contreras-Catala S.G. Marinone I.V. Gutirrez-Palacios V.M. Godínez 《Continental Shelf Research》2009,29(14):1697-1710
The northern Gulf of California (NGC) is characterized by seasonal hydrography and circulation (cyclonic in summer and anticyclonic in winter), by intense tidal mixing in the midriff archipelago region (MAR), and by coastal upwelling on the eastern side from autumn to spring. We examined changes in larval fish assemblages (LFAs) in relation with hydrography and circulation during both phases of the seasonal circulation, as indicators of changes in the pelagic ecosystem. A canonical correspondence analysis defined LFAs (r>0.70), which were related with: (i) the coastal current on the mainland shelf, (ii) the central eddy and (iii) the MAR. In the early cyclonic phase, when the temperature and stratification were increasing and the coastal current was starting, demersal (Gobulus crescentalis, Lythrypnus dalli) and mesopelagic species (Benthosema panamense) dominated the NGC. The highest larval abundance was in the Current LFA area and the lowest in the MAR LFA area. In the mature cyclonic phase, the larval abundance increased in the NGC and species characteristic of eastern boundary current systems such as Opisthonema libertate and Engraulis mordax displaced the demersal species and became dominant, together with B. panamense in the Current LFA area; the latter species dominated in the Eddy LFA area. In the early anticyclonic phase, the direction of the coastal current reversed and the temperature and larval abundance decreased. E. mordax and B. panamense larvae continued dominating the NGC with higher abundance in the MAR than in the Current and Eddy LFA areas. In the mature anticyclonic phase, E. mordax larvae dominated in the Current and the Eddy LFA areas with the highest abundance in the former, while M. productus larvae (an eastern boundary current species) dominated in the Eddy LFA area. Results showed that in the NGC, the dramatically seasonal and predictable hydrographic and circulation features trigger the seasonal spawning of the dominant species. The biological richness of the coastal current area, in both circulation phases, suggested that this area has an important role in the pelagic ecosystem functionality of the NGC. 相似文献
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Hydrographical parameters, phytoplankton productivity and plankton composition were determined over a five-month period in the Bay of Plencia, a coastal area located in the mouth of the river Butron in Biscay, Basque Country. The water column was moderately mixed during most of the study period, which lasted from February to June 1985. Nutrient levels showed high temporal variability and were affected by both river runoff and seasonal biological processes. Nutrients were present most of the time in relatively high concentrations and most of them decreased in late spring. Phytoplankton size structure analysis showed that nanoplankton had the higher chlorophyll content and was responsible for most of the primary production. The phytoplankton showed changes in community composition resulting from the normal progression of the winter-spring conditions. Short-lived peaks of diatom concentration in the spring were followed by periods of low abundance, when maxima of Cladocera and Appendicularia occurred. Total zooplankton showed two peaks of abundance in mid-winter and mid-spring, respectively. Nauplii of Copepoda, juvenile stages of Calanoida and nauplii of Cirripedia were responsible for the two peaks, together with highly seasonal groups (Cladocera, Appendicularia and Cnidaria) in the spring maxima.Primary production seems to be driven by physical processes (temperature, short photoperiod and storms) in winter, whereas depletion of nutrients and grazing by zooplankton are responsible for phytoplankton minima between peaks of abundance in the growing season. Two temporal phases were apparent when the data were analysed by a principal component analysis. 相似文献
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