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41.
Alix Lombard Anny Cazenave Pierre Yves Le Traon Stephanie Guinehut Cécile Cabanes 《Ocean Dynamics》2006,56(5-6):445-451
In this paper, we first discuss the controversial result of the work by Cabanes et al. (Science 294:840–842, 2001), who suggested that the rate of past century sea level rise may have been overestimated, considering the limited and heterogeneous
location of historical tide gauges and the high regional variability of thermal expansion which was supposed to dominate the
observed sea level. If correct, this conclusion would have solved the problem raised by the IPCC third assessment report [Church
et al, Cambridge University Press, Cambridge, pp 881, 2001], namely, the factor two difference between the 20th century observed sea level rise and the computed climatic contributions.
However, recent investigations based on new ocean temperature data sets indicate that thermal expansion only explains part
(about 0.4 mm/year) of the 1.8 mm/year observed sea level rise of the past few decades. In fact, the Cabanes et al.’s conclusion
was incorrect due to a contamination of abnormally high ocean temperature data in the Gulf Stream area that led to an overestimate
of thermal expansion in this region. In this paper, we also estimate thermal expansion over the last decade (1993–2003), using
a new ocean temperature and salinity database. We compare our result with three other estimates, two being based on global
gridded data sets, and one based on an approach similar to that developed here. It is found that the mean rate of thermosteric
sea level rise over the past decade is 1.5±0.3 mm/year, i.e. 50% of the observed 3 mm/year by satellite altimetry. For both
time spans, past few decades and last decade, a contribution of 1.4 mm/year is not explained by thermal expansion, thus needs
to be of water mass origin. Direct estimates of land ice melt for the recent years account for about 1 mm/year sea level rise.
Thus, at least for the last decade, we have moved closer to explaining the observed rate of sea level rise than the IPCC third
assessment report. 相似文献
42.
Records of hydrologic parameters, especially those parameters that are directly linked to air temperature, were analyzed to
find indicators of recent climate warming in Minnesota, USA. Minnesota is projected to be vulnerable to climate change because
of its location in the northern temperate zone of the globe. Ice-out and ice-in dates on lakes, spring (snowmelt) runoff timing,
spring discharge values in streams, and stream water temperatures recorded up to the year 2002 were selected for study. The
analysis was conducted by inspection of 10-year moving averages, linear regression on complete and on partial records, and
by ranking and sorting of events. Moving averages were used for illustrative purposes only. All statistics were computed on
annual data.
All parameters examined show trends, and sometimes quite variable trends, over different periods of the record. With the exception
of spring stream flow rates the trends of all parameters examined point toward a warming climate in Minnesota over the last
two or three decades. Although hidden among strong variability from year to year, ice-out dates on 73 lakes have been shifting
to an earlier date at a rate of −0.13 days/year from 1965 to 2002, while ice-in dates on 34 lakes have been delayed by 0.75
days/year from 1979 to 2002. From 1990 to 2002 the rates of change increased to −0.25 days/year for ice-out and 1.44 days/year
for ice-in. Trend analyses also show that spring runoff at 21 stream gaging sites examined occurs earlier. From 1964 to 2002
the first spring runoff (due to snowmelt) has occurred −0.30 days/year earlier and the first spring peak runoff −0.23 days/year
earlier. The stream water temperature records from 15 sites in the Minneapolis/St Paul metropolitan area shows warming by
0.11∘C/year, on the average, from 1977 to 2002. Urban development may have had a strong influence. The analysis of spring stream
flow rates was inconclusive, probably because runoff is linked as much to precipitation and land use as to air temperature.
Ranking and sorting of annual data shows that a disproportionately large number of early lake ice-out dates has occurred after
1985, but also between 1940 and 1950; similarly late lake ice-in has occurred more frequently since about 1990. Ranking and
sorting of first spring runoff dates also gave evidence of earlier occurrences, i.e. climate warming in late winter.
A relationship of changes in hydrologic parameters with trends in air temperature records was demonstrated. Ice-out dates
were shown to correlate most strongly with average March air temperatures shifting by −2.0 days for a 1°C increase in March air temperature. Spring runoff dates also show a relationship with March air temperatures; spring runoff
dates shift at a rate of −2.5 days/1°C minimum March air temperature change. Water temperatures at seven river sites in the Minneapolis/St Paul metropolitan area
show an average rise of 0.46°C in river temperature/1°C mean annual air temperature change, but this rate of change probably includes effects of urban development.
In conclusion, records of five hydrologic parameters that are closely linked to air temperature show a trend that suggests
recent climate warming in Minnesota, and especially from 1990 to 2002. The recent rates of change calculated from the records
are very noteworthy, but must not be used to project future parameter values, since trends cannot continue indefinitely, and
trend reversals can be seen in some of the long-term records. 相似文献
43.
The pressure dependence of the zirconium-in-rutile thermometer 总被引:19,自引:1,他引:19
The solubility of ZrO2 in rutile is strongly temperature-dependent and has been identified as a potentially powerful thermometer when the rutile coexists with an appropriate buffer assemblage, e.g. zircon + quartz. In combination with experimental data at 10 kbar, previous consideration of data on natural rutile has not identified a pressure dependence for the thermometer. However, the expected volume change as a result of substitution of the larger Zr4+ cation for Ti4+ suggests that the Zr content of rutile should decrease with increasing pressure. To investigate the pressure dependence of the thermometer, piston cylinder (at 10, 20 & 30 kbar) and 1 atm furnace experiments were performed in the system ZrO2 -TiO2 -SiO2 . The solubility of ZrO2 in rutile, in the presence of zircon and quartz was reversed at each pressure value. From these experiments, the thermodynamics of the end-member reaction ZrSiO4 = SiO2 + ZrO2 (in rutile) have been determined. There is a secondary pressure effect accompanying the primary temperature dependence of the Zr content of rutile. New thermometer equations are, in the α -quartz field: in the β -quartz field and in the coesite field in which φ is ppm Zr, P is in kbar and R is the gas constant, 0.0083144 kJ K−1 . Thermometric results using these equations are shown for a range of geological settings. 相似文献
44.
Accepted practice dictates that waterflooding of gas reservoirs should commence, if ever, only when the reservoir pressure has declined to the minimum production pressure. Analytical proof of this hypothesis has yet to appear in the literature however. This paper considers a model for a gas-water reservoir with a variable production rate and enhanced recovery with waterflooding and, using an initial dynamic programming approach, confirms the above hypothesis. 相似文献
45.
D. J. Ellis J. W. Sheraton R. N. England W. B. Dallwitz 《Contributions to Mineralogy and Petrology》1980,72(2):123-143
The pre-Cambrian granulites of Enderby Land Antarctica, contain coexisting spinel-quartz, sapphirine-quartz, hypersthene-sillimanite-quartz and osumilite on a regional extent. Osumilite is present in a variety of mineral assemblages, most of which are documented in granulites for the first time. The mineral assemblages, reactions and compositional zoning in minerals are discussed in terms of continuous and discontinuous reactions in response to changing conditions of metamorphism. The development of many of the mineral coronas can be explained by continuous rather than discontinuous reactions, due to the effects of Mg-Fe and (Mg,Fe)-2Al exchange equilibria with decreasing temperature. The highest P-T conditions of metamorphism (8–10 kb, 900 °–980 ° C, Ellis, in preparation) were beyond the stability limit of coexisting garnet-cordierite. Secondary cordierite has developed through a large number of mineral reactions in response to cooling of these granulites.A theoretical analysis of the phase relations involving osumilite in the chemical systems K2O-MgO-Al2O3-SiO2 and K2O-MgO-FeO-Al2O3-SiO2 is presented. In the pure Mg-system the lower temperature stability limit of Mg-osumilite is inferred to be defined with increasing pressure by the reactions OsCd+En+Kfeld+Qtz, OsSa+En+Kfeld+Qtz, OsSill+En+Kfeld+Qtz. In iron-bearing systems an important reaction involving osumilite is Os+GtCd+Hy+Kfeld+Qtz.At moderate temperatures and pressures, osumilite is limited to rocks which lie on the Mg-rich side of the Cd-Hy stable tie line on an AFM diagram. At higher pressures and temperatures osumilite occurs in a widerrange of rock compositions because of the stability of coexisting garnet and osumilite. Petrographic data, as well as chemographic relations indicate that for many common rock compositions, garnet, cordierite, hypersthene, sapphirine and sillimanite cannot coexist with both osumilite and K-feldspar.Published with the permission of the Director, Bureau of Mineral Resources 相似文献
46.
47.
Marianne Holmer Ole Pedersen Dorte Krause-Jensen Birgit Olesen Malene Hedegrd Petersen Stephanie Schopmeyer Marguerite Koch Bente Aa. Lomstein Henning S. Jensen 《Estuarine, Coastal and Shelf Science》2009,85(2):319-326
Sulfur and oxygen dynamics in the seagrasses Thalassia testudinum and Syringodium filiforme and their sediments were studied in the US Virgin Islands (USVI) in order to explore sulfide intrusion into tropical seagrasses. Four study sites were selected based on the iron concentration in sediments and on proximity to anthropogenic nutrient sources. Meadow characteristics (shoot density, above- and below-ground biomass, nutrient content) were sampled along with sediment biogeochemistry. Sulfide intrusion was high in T. testudinum, as up to 96% of total sulfur in the plant was derived from sediment-derived sulfides. The sulfide intrusion was negatively correlated to the turnover of sulfides in the sediments regulated by both plant parameters and sediment sulfur pools. Sediment iron content played an indirect role by affecting sulfide turnover rates. Leaf production was negatively correlated with sulfide intrusion suggesting that active growth reduced sulfide intrusion. Sulfide intrusion was lower in S. filiforme (up to 44%) compared to T. testudinum consistent with a higher internal nighttime oxygen concentrations found for S. filiforme. When S. filiforme can take advantage of its ability to maintain high internal oxygen concentrations, as was the case on the USVI, it could increase its success in colonizing unvegetated disturbed sediments with potentially high sulfide concentrations. 相似文献
48.
Richard Massey Chris Stoughton Alexie Leauthaud Jason Rhodes Anton Koekemoer Richard Ellis Edgar Shaghoulian 《Monthly notices of the Royal Astronomical Society》2010,401(1):371-384
Charge Transfer Inefficiency (CTI) due to radiation damage above the Earth's atmosphere creates spurious trailing in Hubble Space Telescope ( HST ) images. Radiation damage also creates unrelated warm pixels – but these happen to be perfect for measuring CTI. We model CTI in the Advanced Camera for Surveys (ACS)/Wide Field Channel and construct a physically motivated correction scheme. This operates on raw data, rather than secondary science products, by returning individual electrons to pixels from which they were unintentionally dragged during readout. We apply our correction to images from the HST Cosmic Evolution Survey (COSMOS), successfully reducing the CTI trails by a factor of ∼30 everywhere in the CCD and at all flux levels. We quantify changes in galaxy photometry, astrometry and shape. The remarkable 97 per cent level of correction is more than sufficient to enable a (forthcoming) reanalysis of downstream science products and the collection of larger surveys. 相似文献
49.
Charles F. Rabeni Kevin J. Collier Stephanie M. Parkyn Brendan J. Hicks 《新西兰海洋与淡水研究杂志》2013,47(5):693-700
We evaluated several capture and analysis techniques for estimating abundance and size structure of freshwater crayfish (Paranephrops planifrons) (koura) from a forested North Island, New Zealand stream to provide a methodological basis for future population studies. Direct observation at night and collecting with baited traps were not considered useful. A quadrat sampler was highly biased toward collecting small individuals. Handnetting at night and estimating abundances using the depletion method were not as efficient as handnetting on different dates and analysing by a mark‐recapture technique. Electrofishing was effective in collecting koura from different habitats and resulted in the highest abundance estimates, and mark‐recapture estimates appeared to be more precise than depletion estimates, especially if multiple recaptures were made. Handnetting captured more large crayfish relative to electrofishing or the quadrat sampler. 相似文献
50.