The isotopic signature of monsoon conditions,cloud modes,and rainfall type          下载免费PDF全文

Costijn Zwart  Niels C. Munksgaard  Alain Protat  Naoyuki Kurita  Dionisia Lambrinidis  Michael I. Bird 《水文研究》2018,32(15):2296-2303

This work provides a comprehensive physically based framework for the interpretation of the north Australian rainfall stable isotope record (δ¹⁸O and δ²H). Until now, interpretations mainly relied on statistical relationships between rainfall amount and isotopic values on monthly timescales. Here, we use multiseason daily rainfall stable isotope and high resolution (10 min) ground‐based C‐band polarimetric radar data and show that the five weather types (monsoon regimes) that constitute the Australian wet season each have a characteristic isotope ratio. The data suggest that this is not only due to changes in regional rainfall amount during these regimes but, more importantly, is due to different rain and cloud types that are associated with the large scale circulation regimes. Negative (positive) isotope anomalies occurred when stratiform rainfall fractions were large (small) and the horizontal extent of raining areas were largest (smallest). Intense, yet isolated, convective conditions were associated with enriched isotope values whereas more depleted isotope values were observed when convection was widespread but less intense. This means that isotopic proxy records may record the frequency of which these typical wet season regimes occur. Positive anomalies in paleoclimatic records are most likely associated with periods where continental convection dominates and convection is sea‐breeze forced. Negative anomalies may be interpreted as periods when the monsoon trough is active, convection is of the oceanic type, less electric, and stratiform areas are wide spread. This connection between variability of rainfall isotope anomalies and the intrinsic properties of convection and its large‐scale environment has important implications for all fields of research that use rainfall stable isotopes.  相似文献   

Systematic uncertainties in the analysis of star cluster parameters based on broad-band imaging observations     

R. de Grijs  P. Anders  H. J. G. L. M. Lamers  N. Bastian  U. Fritze-v. Alvensleben  G. Parmentier †  M. E. Sharina  S. Yi 《Monthly notices of the Royal Astronomical Society》2005,359(3):874-894

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Tribute to John Wasson     

Ed Anders  Derek Sears 《Meteoritics & planetary science》1992,27(1):2-2

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Sediment flux from a fjord during glacial periods, Isfjorden, Spitsbergen     

Roger LeB. Hooke  Anders Elverhi 《Global and Planetary Change》1996,12(1-4)

Sediment has accumulated in Isfjorden, a deep fjord in Spitsbergen, at a rate of 1.7 km³/k.y. during the past 13 k.y. Between 200 ka and 13 ka the fjord was free of ice for 120 k.y. Assuming a similar sediment delivery rate during this ice-free time, 200 km³ of sediment would have accumulated in the fjord. An alternative calculation based on erosion rates suggests that 400 km³ could have been delivered to Isfjorden during this 120 k.y.Seismic studies have identified a 330 km³ package of sediment on the continental shelf and slope west of Isfjorden. This sediment is believed to have accumulated between 200 ka and 13 ka. Herein we argue that this is sediment that was originally deposited in the fjord, and that it was transferred to the shelf by glaciers in the 70 ka during which the fjord was occupied by ice. Calculations using a steady-state numerical model suggest that the sediment could have been moved in a deforming layer of subglacial till and in subglacial melt streams at rates of 7.6 × 10⁶ m³ a⁻¹ and 0.3 × 10⁶ m³ a⁻¹, respectively, resulting in a total flux of 7.9 × 10⁶ m³ a⁻¹. It is unlikely that much sediment was moved in a basal layer of dirty ice, as intense basal melting would have inhibited sediment entrainment.Of the time that glaciers occupied the fjord, 60% would have been required to evacuate the accumulated sediment. During the remaining time, the ice could have been deepening the fjord.  相似文献   

What controls dead-ice melting under different climate conditions? A discussion     

Anders Schomacker   《Earth》2008,90(3-4):103-113

In the geological record, hummocky dead-ice moraines represent the final product of the melt-out of dead-ice. Processes and rates of dead-ice melting in ice-cored moraines and at debris-covered glaciers are commonly believed to be governed by climate and debris-cover properties. Here, backwasting rates from 14 dead-ice areas are assessed in relation to mean annual air temperature, mean summer air temperature, mean annual precipitation, mean summer precipitation, and annual sum of positive degree days. The highest correlation was found between backwasting rate and mean annual air temperature. However, the correlation between melt rates and climate parameters is low, stressing that processes and topography play a major role in governing the rates of backwasting. The rates of backwasting from modern glacial environments should serve as input to de-icing models for ancient dead-ice areas in order to assess the mode and duration of deposition.A challenge for future explorations of dead-ice environments is to obtain long-term records of field-based monitoring of melt progression. Furthermore, many modern satellite-borne sensors have high potentials for recordings of multi-temporal Digital Elevation Models (DEMs) for detection and quantification of changes in dead-ice environments. In recent years, high-accuracy DEMs from airborne laser scanning altimetry (LiDAR) are emerging as an additional data source. However, time series of high-resolution aerial photographs remain essential for both visual inspection and high-resolution stereographic DEM production.  相似文献   

Trends in age-composition, growth and reproductive parameters of Barents Sea harp seals, Phoca groenlandica     

Kjellqwist  Sten Anders; Haug  Tore; Oritsland  Torger 《ICES Journal of Marine Science》1995,52(2):197-208

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Editing the ICES Journal of Marine Science: a joy forever?     

Daan  Niels 《ICES Journal of Marine Science》2003,60(6):1167-1168

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Seabird numbers and prey consumption in the North Atlantic   总被引：1，自引：0，他引：1  

Barrett  Robert T.; Chapdelaine  Gilles; Anker-Nilssen  Tycho; Mosbech  Anders; Montevecchi  William A.; Reid  James B.; Veit  Richard R. 《ICES Journal of Marine Science》2006,63(6):1145-1158

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Modelling gastric evacuation without meal size as a variable. A model applicable for the estimation of daily ration of cod (Gadus morhua L.) in the field   总被引：1，自引：0，他引：1  

Temming  Axel; Andersen  Niels G. 《ICES Journal of Marine Science》1994,51(4):429-438

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Eddy Diffusion Coefficients of Suspended Particulate Matter: Effects of Wind Energy Transfer and Stratification     

Lars Chresten Lund-Hansen  Morten Pejrup  Jens Valeur  Anders Jensen 《Estuarine, Coastal and Shelf Science》1994,38(6)

Gross sedimentation rates (GSR) have been measured using sediment traps placed at nine different levels above the bed (0·3, 0·5, 0·8, 1·0, 2·0, 4·0, 6·0, 8·0 and 10·0 m). The sediment traps were deployed for 1·25 years and recovered 28 times during the study period. Low average GSR values of 5·5 g m^-2 day^-1 were obtained at 10·0 m, and high average GSR values of 114·8 g m^-2 day^-1 were obtained at 0·3 m. An expression for the eddy diffusion coefficient of suspended particulate matter (K_s), based on the measured GSR is given. The expression has been used for modelling of K_s at the different trap levels above the bed. High values (≈42 cm² s^-1) of K_s were obtained at the upper traps, whereas low values (≈2 cm² s^-1) were obtained near the bed. Comparison between level of turbulent energy in terms of shear stress at the boundaries of the water column, i.e. from the wind and the bed flow, showed that wind energy exceeded that of the bed flow by a factor 16. At 5·0 m K_s was positively correlated (r=0·66) to the eddy diffusion coefficient of momentum (K_m) derived from the wind energy transfer to the water, giving an average β of 0·5 for K_s =βK_m. The density difference between surface and bottom waters has been designated a parameter of stratification, and is discussed in relation to variations of K_s and K_m .  相似文献