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Variability and climate sensitivity of fast ice extent in the north-eastern Kara Sea 总被引:1,自引:0,他引:1
This work investigates the temporal and spatial variation of shore-fast ice extent in the north-eastern part of the Kara Sea during 1953-1990 and its sensitivity to interannual variability of the regional climate. The area of fast ice in spring months shows a bimodal distribution. This indicates the existence of two different regimes of fast ice formation driven by the system of prevailing winds. The westward wind transport during the cold season gives larger fast ice extent while the eastward wind transport suppresses the expansion of fast ice. There is a significant correlation (ca. −0.55) between the average winter temperature and the area of fast ice. Linear trends for time records of shore-fast ice area in spring show a decrease during 1953-1990. This decrease is most pronounced in April: the mean fast ice area in April is 12% lower in 1988-1990 compared to 1953-55. A comparison of fast ice regimes for two particular years–1979 and 1985–revealed a significant influence of cyclone activity on fast ice development over the course of the cold season. It is shown that partial break-ups of fast ice in spring 1985 are associated with the passage of cyclones across the area of fast ice. 相似文献
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The present estimates of ice drift in the Arctic include utilization of satellite imagery data (special sensor microwave/imager) and a reconstruction of air pressure for the period 1899-1998. A significant part of the sea ice in the Arctic Ocean has its origin in the Kara Sea and melts in the Greenland and the Barents Sea (BS). Consequently there may be a particular risk of pollutants in the Kara Sea entering the food webs of the Greenland and BS. The ice export from the Kara Sea between 1988 and 1994 was about 208,000 km2 (154 km3) per year. The import of ice into the BS was during the same period 161,000 km2 (183 km3) per year while the ice drift through the Fram Strait into the Greenland Sea was 583,000 km2 (1859 km3) per year. Ice which formed adjacent to the Ob and Yenisey rivers in early January, drifted into the BS within two years (with a probability of about 50%. 相似文献
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L’Her Alexandre Reinert Markus Prants Sergey Carton Xavier Morvan Mathieu 《Ocean Dynamics》2021,71(5):601-612
Ocean Dynamics - The Eastern Kamchatka Current (EKC) is the western boundary current of the North Pacific subpolar gyre. Southeast of the Kamchatka Peninsula lies a large anticyclonic eddy, the... 相似文献
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Mechanical properties of high porosity chalks are strongly dependent on the type of fluid in the pores. Dry chalk is considerably stronger than water-saturated chalk, and this phenomenon is often referred to as the water-weakening effect. To address the problem of chalk–fluid interactions, several series of tests have been performed with glycol and high concentration brines as saturating fluids. Glycol is a fluid that in many aspects resembles oil, except that glycol is miscible with water. Glycol-saturated chalk turns out to have properties very similar to oil-saturated chalk. Compared to dry chalk, both oil and glycol make the chalk somewhat weaker, but this weakening effect is much less than with water. Several series of tests with brines with high concentrations of calcium chloride or sodium chloride show that the water-weakening effect is considerably reduced in high ionic strength solutions. Most tests were performed as quasi-hydrostatic tests, with a constant stress ratio of 0.9. In such tests, the yield point marks the onset of accelerated pore collapse, and the yield value is close to the hydrostatic yield stress. In addition to these compressive tests, a series of Brazilian tests were performed, revealing the same trend. The variations in mechanical strength have been correlated with the activity of water in the brines. Within the experimental accuracy of the compressive tests, there is a linear trend between reduction of water activity and the corresponding increase in strength. This leads to the hypothesis that the water activity may be a key parameter in the water-weakening mechanism. But this conclusion also indicates that water weakening may be a special case of general chalk–fluid interactions where the degree of weakening depends on the strength of adsorption of the fluid molecules to the calcite surfaces. 相似文献
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Remote sensing of the ice cover in Storfjorden (Svalbard) revealed the persistence and evolution of latent heat polynyas during the winter of 1997/98. Latent heat polynyas open mechanically under wind stress or ocean currents that transport the ice cover away. In the present work we used mathematical modelling to simulate the Storfjorden polynya size and geometry caused by wind stress, measured at the meteorological station on the island of Hopen in winter 1997/98. The dependence of the polynya outlines on the wind velocity is presented. Two approaches were used: quasi-static and dynamic. Quasi-static simulations are based on a time-independent, linear ice stress-strain relationship valid for the low strain rates only. Time dependence of the ice cover fracture is joined with stress-strain nonlinearity caused by ice delayed-elastic recovery and viscosity. Results are compared to satellite observations from the synthetic aperture radar (SAR) of ERS-2. The simulation results show that a northern wind opens a larger polynya (ca. 30%) than does a north-eastern wind with the same speed. The results also indicate that the bathymetry and geometry of the fjord might have a stronger influence on the polynya opening and development than the location of individual islands and reefs. 相似文献
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Daniel Reinert Volkmar Wirth Joachim Eichhorn Walter-Georg Panhans 《Boundary-Layer Meteorology》2007,125(1):109-132
This paper presents the dry version of a new large-eddy simulation (LES) model, which is designed to simulate air flow and
clouds above highly complex terrain. The model is three-dimensional and nonhydrostatic, and the governing equations are sound
filtered by use of the anelastic approximation. A fractional step method is applied to solve the equations on a staggered
Cartesian grid. Arbitrarily steep and complex orography can be accounted for through the method of viscous topography. The
dynamical model core is validated by comparing the results for a spreading density current against a benchmark solution. The
model accuracy is further assessed through the simulation of turbulent flow across a quasi two-dimensional ridge. The results
are compared with wind-tunnel data. The method of viscous topography is not restricted to moderately sloped terrain. Compared
to models using curvilinear grids, it allows this model to be applied to a much wider range of flows. This is illustrated
through the simulation of an atmospheric boundary-layer flow over a surface mounted cube. The results show that the dry model
version is able to accurately represent the complex flow in the vicinity of three-dimensional obstacles. It is concluded that
the method of viscous topography was successfully implemented into a micrometeorological LES model. As will be shown in Part
II, this allows the detailed study of clouds in highly complex terrain. 相似文献
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