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51.
52.
In a recent paper, Nof et al. (J Paleolimnol 35:417–439, 2006) suggest a physical mechanism which could account for the formation
of ice on Lake Kinneret (Sea of Galilee) in northern Israel. Based on the sea surface temperature record of sediment cores
from the Mediterranean Sea the authors argue that centennial-scale cold events had the potential to trigger local ‘springs
ice’ formation on the lake in the past. Here, we demonstrate that a closer inspection of the paleoceanographic record in combination
with correlation and regression analyses of meteorological data provides no evidence for such cold events in the lake region
during the last 10,000 years. Thus, the formation of ‘springs ice’ on Lake Kinneret was unlikely at least since the beginning
of the Neolithic. 相似文献
53.
The mechanical denudation rates of 81 large lake basins (lake area > 500 km2) were determined from long-term river loads and erosion maps. Using the drainage area/lake area ratios the mean sedimentation rates of the lakes were calculated for a porosity of 0.3. The mean sedimentation rates of different lake types vary between 0.1 mm/a (glacial lakes, lowland) and 5.4 mm/a (mostly sag basin lakes). The calculated lifetimes of the lakes are based on the lake volumes and mean sedimentation rates, assuming steady-state conditions and solely clastic material. On average, glacial lakes in highlands and fault-related lakes show the shortest lifetimes (c. 70 ka), glacial lakes in lowlands and rift lakes have the longest lifetimes (c. 1 Ma). Some lakes remain unfilled for very long time spans due to rapid subsidence of their basin floors. The calculated lifetimes are compared with those derived from sediment core studies. Most core studies indicate lower mechanical sedimentation rates than the calculated ones because a major part of the incoming sediment is trapped in deltas. However, a number of lakes (e.g., the Great Lakes of North America) show the opposite tendency which is largely caused by extensive shoreline erosion and resuspension. The lifetimes of large glacial lakes often exceed the duration of interglacials. Hence, their lifetimes are restricted by glaciation and not by sediment infill. Rift lakes persist for long time periods which exceed the calculated lifetimes in some cases. Time-dependent subsidence, basin extension, as well as the impact of climate change are briefly described. 相似文献
54.
Conservative tracers are necessary to obtain groundwater transport velocities at the field scale. Deuterated water is an
effective tracer for this purpose due to its similarity to water, chemical stability, non-reactivity, ease of handling and
sampling, relatively neutral buoyancy, and reasonable price. Reliable detection limits of 0.1 mg deuterium/L may be obtained
in field tests. A field example is presented in which deuterated water, bromide, and pentafluorobenzoic acid are used as groundwater
tracers. Deuterated water appeared to be transported conservatively, producing almost identical breakthrough curves as that
of other soluble tracers.
Electronic Publication 相似文献
55.
56.
57.
Matthias Kuhle 《GeoJournal》1995,37(4):431-449
58.
59.
The search for exoelectron emission from Apollo 12 materials usually produced negative results, suggesting that the concentration of naturally occurring traps is very low. Weak exoelectron activity was found scattered inhomogeneously within a pigeonite basalt rock and in a deep core tube sample. Its erratic appearance and intensity makes any interpretation of radiation history most difficult and is attributed to the activity being carried by only a few scattered crystals. The thermally stimulated emission of exoelectrons is judged an unsuitable technique for tracing the radiation histories of these samples. 相似文献
60.
Dr. Matthias Tomczak Jr. 《Ocean Dynamics》1968,21(4):145-151
Zusammenfassung Für winderzeugte interne Wellen wird gezeigt, daß bei der Trägheitsperiode in erster Näherung Resonanz eintritt, die in zweiter Näherung in zwei symmetrisch zur Trägheitsperiode liegende Resonanzen zerfällt. Der Effekt wächst mit zunehmender Schichtung und ist außerdem abhängig vom virtuellen Austauschkoeffizienten und der WellenlängeL der internen Wellen. Die Näherung erfolgt in Termen des Verhältnissesd
2
H
2
(d=Dicke der winderzeugten Grenzschicht,H=Wassertiefe).
On internal waves near the inertia period
Summary Wind-generated internal waves are shown to have a resonance at the inertia period to first order of an analytical approximation which, to second order, splits into two resonances lying symmetrically to the inertia period. The effect is large for strong stratification and depends also on the Austausch coefficient and the wave lengthL of the internal waves. The approximation is done in terms ofd 2 H 2 whered=thickness of the wind-generated boundary layer andH=water depth.
Sur les ondes internes près de la période d'inertie
Résumé On montre que pour les ondes internes dues au vent, il se produit en première approximation, à la période d'inertie, une résonance qui, en deuxième approximation, se décompose en deux résonances symétriques par rapport à la période d'inertie. L'effet augmente avec une stratification croissante et dépend en outre du coefficient de turbulence virtuel et de la longueur d'ondeL des ondes internes. L'approximation s'obtient en termes du rapportd 2 H 2 (d=épaisseur de la couche-limite due au vent,H=profondeur de l'eau).相似文献