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1.
Data collected every 20 minutes for 18 months by a meteorological buoy moored on Lake Sempach in Switzerland (maximum depth
86 m, surface area 14.1 km2) are used to calculate different processes contributing to the net heat flux between water and atmosphere. The processes
considered are shortwave and longwave radiation, evaporation/condensation and sensible heat transfer. The temporal resolution
of the measurements allows the evaluation of the processes occurring on three different time scales: diurnal variations, weather
events of a few days and yearly cycles. The heat content of the lake is calculated from quasi-continuous measurements of water
temperature at different depths. The yearly amplitude of the heat content is 1100·106 J/m2. Short-time variations of the heat flux determined from water temperature analysis agree well with the flux variations modeled
using meteorological data. However, the latter generally underestimates the measured net heat flux in the long term. Wind
measurements, together with the net heat flux, are used to calculate the Flux Richardson Number and the Monin-Obukov Length.
Examples are given to show the predominant influence of the wind on the stratification of the upper water column and thus
on the surface water temperature.
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2.
Jürg W. Schlatter Alfred Wüest Dieter M. Imboden 《Aquatic Sciences - Research Across Boundaries》1997,59(3):225-242
The artificial tracer sulphur hexafluoride (SF6) has been used to study the density-driven deep water exchange between two sill-separated basins of Lake Lucerne, Gersauersee and Urnersee. The sources of the density gradients between the two basins are (1) salinity differences between the major inlets due to the different geology of their drainage areas, and (2) temperature differences due to spatial variation of wind forcing. Wind speeds are generally larger in Urnersee, especially in spring during the so-called Föhn events, when winds blow from the south. In contrast, Gersauersee is protected form these winds. In spring 1989, a total of 630 g of SF6 was released at 80 to 120 m depth in the small Treib Basin located between Urnersee and Gersauersee. During about 100 days the distribution of SF6 in the lake was determined by gaschromatography. Two models are used to quantify the exchange flow, (1) a one-box mass balance model for SF6 in the deep part of Treib Basin, and (2) a one-dimensional diffusion/advection model describing the temporal and vertical temperature variation in Urnersee. According to the first model, the flow into the deep hypolimnion of Urnersee, decreases from 21·106 m3·d?1 at the end of March to about 8·106 m3·d?1 in late April. The second model yields similar flow rates. The decrease of the flow rate during spring, confirmed by both approaches, is consistent (1) with the decreasing strength of the density gradient above the sill during spring and early summer, and (2) with hydrographic information collected in Lake Lucerne during other years. 相似文献
3.
David M. Livingstone Dieter M. Imboden 《Aquatic Sciences - Research Across Boundaries》1989,51(4):351-369
The mean heat budget of Lake Aegeri, Switzerland, is 950 MJ·m–2, comparable to that of neighbouring lakes. The annual variation in the net heat flux can be adequately described using a six-term heat balance equation based on 12 years of monthly mean meteorological and surface temperature data. Although the magnitude of the net heat flux is dominated by the radiative terms of the equation, the one-month backward shift of the net flux and total heat content extrema from the solstices and equinoxes respectively is due to the phase shift of the non-radiative with respect to the radiative terms. A linear approximation was used to express the net heat flux in terms of a heat exchange coefficient and an equilibrium temperature. The former varies from 17 to 28 W·m–2·K–1 in the course of a year; fluctuations in the latter are found to depend mainly on fluctuations in cloud cover and relative humidity, whilst the effect of fluctuations in air temperature and wind speed is slight. 相似文献
4.
Mögliche Massnahmen zur Restaurierung des Sempachersees 总被引：1，自引：1，他引：1
R. Gächter D. Imboden H. Bührer P. Stadelmann 《Aquatic Sciences - Research Across Boundaries》1983,45(1):246-266
Since 1954 average orthophosphate and total phosphorus concentrations have increased twenty and eightfold respectively in
Lake Sempach. It is demonstrated that the lake is not in steady state with its phosphorus loading and that the net deposition
rate of phosphorus is not linearly related to the phosphorus content of the lake. This implies that linear steady state one-box
models are unsuitable to describe the phosphorus balance of this lake. Applying a nonlinear dynamic lake model we predict
that the defined water quality goals ([P] ⩽30 mg m−3, [O2 ⩾4 mg m−3]) can only be achieved within the next 15 years if the external phosphorus loading is reduced by at least 50% and simultaneously
lake-internal measures, such as hypolimnion areation or hypolimnion siphoning are carried into effect.
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5.
Stephan Klump Yama Tomonaga Wolfgang Kinzelbach Dieter M. Imboden 《Geochimica et cosmochimica acta》2007,71(6):1385-1397
Gas exchange between seepage water and soil air within the unsaturated and quasi-saturated zones is fundamentally different from gas exchange between water and gas across a free boundary layer, e.g., in lakes or rivers. In addition to the atmospheric equilibrium fraction, most groundwater samples contain an excess of dissolved atmospheric gases which is called “excess air”. Excess air in groundwater is not only of crucial importance for the interpretation of gaseous environmental tracer data, but also for other aspects of groundwater hydrology, e.g., for oxygen availability in bio-remediation and in connection with changes in transport dynamics caused by the presence of entrapped air bubbles. Whereas atmospheric solubility equilibrium is controlled mainly by local soil temperature, the excess air component is characterized by the (hydrostatic) pressure acting on entrapped air bubbles within the quasi-saturated zone. Here we present the results of preliminary field experiments in which we investigated gas exchange and excess air formation in natural porous media. The experimental data suggest that the formation of excess air depends significantly on soil properties and on infiltration mechanisms. Excess air was produced by the partial dissolution of entrapped air bubbles during a sprinkling experiment in fine-grained sediments, whereas similar experiments conducted in coarse sand and gravel did not lead to the formation of excess air in the infiltrating water. Furthermore, the experiments revealed that the noble gas temperatures determined from noble gases dissolved in seepage water at different depths are identical to the corresponding in situ soil temperatures. This finding is important for all applications of noble gases as a paleotemperature indicator in groundwater since these applications are always based on the assumption that the noble gas temperature is identical to the (past) soil temperature. 相似文献
6.
Dr. Dieter M. Imboden 《Aquatic Sciences - Research Across Boundaries》1973,35(1):29-68
Physical as well as biochemical processes have a significant influence on the material balance of a lake. Mathematical concepts
are developed to treat transport phenomena with which a comparison of different lakes under certain systematic aspects becomes
possible. A two-box model consisting of the subsystems epilimnion and hypolimnion, for lakes with one specific limiting nutrient
factor (e.g., phosphorus) is employed to evaluate eutrophication processes. In particular, a theoretical basis forVollenweider's [3] empirical relation between specific phosphorus loading and the trophic state is presented. Finally, the inhomogeneous
O2-consumption in the deep part of the lake during summer stagnation is calculated with diffusion theory.
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7.
K. Wuhrmann Peter Perret Ch. Imboden H. R. Bürgi F. Klötzli Jürg Bloesch R. Koblet H. Bührer R. Koblet 《Aquatic Sciences - Research Across Boundaries》1977,39(1):104-108
Ohne Zusammenfassung 相似文献
8.
Irena Hajdas Susan D Ivy Jürg Beer Georges Bonani Dieter Imboden André F Lotted Michael Sturm Martin Suter 《Climate Dynamics》1993,9(3):107-116
For the extension of the radiocarbon calibration curve beyond 10000 14C y BP, laminated sediment from Lake Soppensee (central Switzerland) was dated. The radiocarbon time scale was obtained using accelerator mass spectrometry (AMS) dating of terrestrial macrofossils selected from the Soppensee sediment. Because of an unlaminated sediment section during the Younger Dryas (10000–11000 14C y BP), the absolute time scale, based on counting annual layers (varves), had to be corrected for missing varves. The Soppensee radiocarbon-verve chronology covers the time period from 6000 to 12000 14C y BP on the radiocarbon time scale and 7000 to 13000 calendar y BP on the absolute time scale. The good agreement with the tree ring curve in the interval from 7000 to 11450 cal y BP (cal y indicates calendar year) proves the annual character of the laminations. The ash layer of the Vasset/Killian Tephra (Massif Central, France) is dated at 8230±140 14C y BP and 9407±44 cal y BP. The boundaries of the Younger Dryas biozone are placed at 10986±69 cal y BP (Younger Dryas/Preboreal) and 1212±86 cal y BP (Alleröd/Younger Dryas) on the absolute time scale. The absolute age of the Laacher See Tephra layer, dated with the radiocarbon method at 10 800 to 11200 14C y BP, is estimated at 12350 ± 135 cal y BP. The oldest radiocarbon age of 14190±120 14C y BP was obtained on macrofossils of pioneer vegetation which were found in the lowermost part of the sediment profile. For the late Glacial, the offset between the radiocarbon (10000–12000 14C y BP) and the absolute time scale (11400–13000 cal y BP) in the Soppensee chronology is not greater than 1000 years, which differs from the trend of the U/Th-radiocarbon curve derived from corals. 相似文献
9.
Exploring the link between climate change and migration 总被引：1，自引：1，他引：0
Previous research has postulated that climate change will lead to mass migration. However, the linkages postulated between the two have not been explicitly demonstrated but have rather been derived from ‘common sense’. In this paper, the connection between climate change and migration via two mechanisms, sea level rise and floods, is investigated and depicted in conceptual models. In both cases, a connection can be traced and the linkages are made explicit. However, the study also clearly shows that the connection is by no means deterministic but depends on numerous factors relating to the vulnerability of the people and the region in question. 相似文献
10.
C.P. Holzner D.F. McGinnis C.J. Schubert R. Kipfer D.M. Imboden 《Earth and Planetary Science Letters》2008,265(3-4):396-409
Dissolved noble gases and tritium were analyzed at a series of high-intensity methane gas seeps in the Black Sea to study the transport and gas exchange induced by bubble-streams in the water column. These processes affect marine methane emissions to the atmosphere and are therefore relevant to climate warming. The seep areas investigated are located in the Dnepr paleo-delta, west of Crimea, and in the Sorokin Trough mud volcano area, south-east of Crimea. Noble gas concentration profiles at active seep sites revealed prominent anomalies compared to reference profiles that are unaffected by outgassing. Supersaturations of the light noble gases helium and neon observed relatively close to the sea floor are interpreted as effects of gas exchange between the water and the rising bubbles. Depletions of the heavy noble gases argon, krypton and xenon that were detected above an active, bubble-releasing mud volcano appear to be related to the injection of fluids depleted in noble gases that undergo vertical transport in the water column due to small density differences. In both cases, the noble gas anomalies clearly document seep-specific processes which are difficult to detect by other methods. Helium is generally enriched in the deep water of the Black Sea due to terrigenic input. Although exceptionally high helium concentrations observed in one seep area indicate a locally elevated helium flux, most of the seeps studied seem to be negligible sources of terrigenic helium. Noble gas analyses of sediment pore waters from the vicinity of a mud volcano showed large vertical gradients in helium concentrations. The helium isotope signature of the pore waters points to a crustal origin for helium, whereas the deep water of the Black Sea also contains a small mantle-type component. 相似文献