scholarly journals A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus

2011 ◽  
Vol 5 (3) ◽  
pp. 525-538 ◽  
Author(s):  
A. Lambrecht ◽  
C. Mayer ◽  
W. Hagg ◽  
V. Popovnin ◽  
A. Rezepkin ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Measurements ◽  
Special Focus ◽  
European Alps ◽  
The Caucasus ◽  
The North ◽  
Glacier Melt ◽  
Significant Difference ◽  
Debris Cover ◽  
Caucasus Mountains

Abstract. The glacier coverage in the Caucasus Mountains underwent considerable changes during the last decades. In some regions, the observed reduction in glacier area is comparable to those in the European Alps and the extent of supra-glacial debris increased on many glaciers. Only a few glaciers in the Caucasus are monitored on a regular basis, while for most areas no continuous field measurements are available. In this study, regional differences of the conditions for glacier melt with a special focus on debris covered glacier tongues in the well-studied Adyl-su basin on the northern slope of the Caucasus Mountains (Russia) is compared with the Zopkhito basin which has similar characteristics but is located on the southern slope in Georgia. The paper focuses on the effect of supra-glacial debris cover on glacier summer melt. There are systematic differences in the distribution and increase of the debris cover on the glaciers of the two basins. In the Adyl-su basin an extensive debris cover on the glacier tongues is common, however, only those glacier tongues that are positioned at the lowest elevations in the Zopkhito basin show a considerable extent of supra-glacial debris. The observed increase in debris cover is considerably stronger in the north. Field experiments show that thermal resistance of the debris cover in both basins is somewhat higher than in other glaciated regions of the world, but there is also a significant difference between the two regions. A simple ablation model accounting for the effect of debris cover on ice melt shows that melt rates are considerably higher in the northern basin despite a wider debris distribution. This difference between the two regions can be attributed to different meteorological conditions which are characterised by more frequent cloud cover and precipitation in the south. Furthermore ablation is strongly influenced by the occurrence of supra-glacial debris cover in both basins, reducing the total amount of melt on the studied glaciers by about 25 %. This effect mitigates glacier retreat in the lower sectors of the ablation zones considerably. The sensitivity to moderate changes in the debris cover, however, is rather small which implies only gradual changes of the melt regime due to debris cover dynamics during the near future.

scholarly journals A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus

2011 ◽  
Vol 5 (1) ◽  
pp. 431-459 ◽  
Author(s):  
A. Lambrecht ◽  
C. Mayer ◽  
W. Hagg ◽  
V. Popovnin ◽  
A. Rezepkin ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Measurements ◽  
Special Focus ◽  
European Alps ◽  
The South ◽  
The Caucasus ◽  
Ice Melt ◽  
The North ◽  
Debris Cover ◽  
Southern Caucasus

Abstract. The glacier coverage in the Caucasus Mountains underwent considerable changes during the last decades. Besides a reduction in glacier area which in some areas is comparable to area changes in the European Alps, also the concentration of supra-glacial debris increased on many glaciers. Only a few glaciers in the Caucasus are monitored on a regular basis, while for most areas no field measurements are available on a continuous basis. In this study the regional differences between the well studied Adyl-su basin on the northern slope of the Caucasus is compared with a similar basin in the South (Zopkhito basin). Special focus is laid on the effect of supra-glacial debris cover on the melt conditions during the ablation season. Systematic differences can be shown for the distribution and temporal increase of the debris cover on the glaciers. While in the Adyl-su basin an extensive debris cover on the glacier tongues is common, only some low lying glacier tongues in the Zopkhito basin show considerable supra-glacial debris. Also the temporal increase in debris cover is decidedly stronger in the North. Field experiments show that the thermal resistance of the debris cover is somewhat higher than in other glacerised regions in the world. A simple ablation model which includes the effect of the debris cover on ice melt indicates considerably stronger melt rates in the northern basin, despite the much more widespread debris distribution. This is due to the different meteorological conditions with more frequent cloud cover and precipitation in the South. Still ablation is strongly influenced in both basins by the occurrence of supra-glacial debris cover, reducing the total amount of melt on the glacier by about 20%. Especially in the lower tongue areas this effect mitigates the area loss of the glaciers considerably.

scholarly journals Field Measurements of Surface and Near-Surface Turbulence in the Presence of Breaking Waves

2015 ◽  
Vol 45 (4) ◽  
pp. 943-965 ◽  
Author(s):  
Peter Sutherland ◽  
W. Kendall Melville
Keyword(s):  
Field Experiments ◽  
North Pacific Ocean ◽  
Large Fraction ◽  
Field Measurements ◽  
Breaking Waves ◽  
Sea Surface ◽  
Near Surface ◽  
Wave Energy Dissipation ◽  
Eddy Simulation ◽  
The North

AbstractWave breaking removes energy from the surface wave field and injects it into the upper ocean, where it is dissipated by viscosity. This paper presents an investigation of turbulent kinetic energy (TKE) dissipation beneath breaking waves. Wind, wave, and turbulence data were collected in the North Pacific Ocean aboard R/P FLIP, during the ONR-sponsored High Resolution Air-Sea Interaction (HiRes) and Radiance in a Dynamic Ocean (RaDyO) experiments. A new method for measuring TKE dissipation at the sea surface was combined with subsurface measurements to allow estimation of TKE dissipation over the entire wave-affected surface layer. Near the surface, dissipation decayed with depth as z−1, and below approximately one significant wave height, it decayed more quickly, approaching z−2. High levels of TKE dissipation very near the sea surface were consistent with the large fraction of wave energy dissipation attributed to non-air-entraining microbreakers. Comparison of measured profiles with large-eddy simulation results in the literature suggests that dissipation is concentrated closer to the surface than previously expected, largely because the simulations did not resolve microbreaking. Total integrated dissipation in the water column agreed well with dissipation by breaking for young waves, (where cm is the mean wave frequency and is the atmospheric friction velocity), implying that breaking was the dominant source of turbulence in those conditions. The results of these extensive measurements of near-surface dissipation over three field experiments are discussed in the context of observations and ocean boundary layer modeling efforts by other groups.

scholarly journals Late-20th-century changes in glacier extent in the Caucasus Mountains, Russia/Georgia

2006 ◽  
Vol 52 (176) ◽  
pp. 99-109 ◽  
Author(s):  
Chris R. Stokes ◽  
Stephen D. Gurney ◽  
Maria Shahgedanova ◽  
Victor Popovnin
Keyword(s):  
Field Measurements ◽  
Thematic Mapper ◽  
Ice Age ◽  
Late 20Th Century ◽  
The Caucasus ◽  
Central Caucasus ◽  
Caucasus Mountains ◽  
1960S And 1970S ◽  
Colour Composite ◽  
The 1960S

AbstractGlaciers occupy an area of ~1600km2 in the Caucasus Mountains. There is widespread evidence of retreat since the Little Ice Age, but an up-to-date regional assessment of glacier change is lacking. In this paper, satellite imagery (Landsat Thematic Mapper and Enhanced Thematic Mapper Plus) is used to obtain the terminus position of 113 glaciers in the central Caucasus in 1985 and 2000, using a manual delineation process based on a false-colour composite (bands 5, 4, 3). Measurements reveal that 94% of the glaciers have retreated, 4% exhibited no overall change and 2% advanced. The mean retreat rate equates to ~8ma–1, and maximum retreat rates approach ~38 m a–1. The largest (>10 km2) glaciers retreated twice as much (~12ma–1) as the smallest (<1 km2) glaciers (~6ma–1), and glaciers at lower elevations generally retreated greater distances. Supraglacial debris cover has increased in association with glacier retreat, and the surface area of bare ice has reduced by ~10% between 1985 and 2000. Results are compared to declassified Corona imagery from the 1960s and 1970s and detailed field measurements and mass-balance data for Djankuat glacier, central Caucasus. It is concluded that the decrease in glacier area appears to be primarily driven by increasing temperatures since the 1970s and especially since the mid-1990s. Continued retreat could lead to considerable changes in glacier runoff, with implications for regional water resources.

scholarly journals OPTIMUM PLOT SIZE AND NUMBER OF REPLICATIONS IN PAPAYA FIELD EXPERIMENT

2016 ◽  
Vol 38 (2) ◽  
Author(s):  
EDILSON ROMAIS SCHMILDT ◽  
OMAR SCHMILDT ◽  
COSME DAMIÃO CRUZ ◽  
LAERCIO FRANCISCO CATTANEO ◽  
GERALDO ANTÔNIO FERREGUETTI
Keyword(s):  
Field Experiments ◽  
Optimal Number ◽  
Optimum Size ◽  
Plot Size ◽  
Maximum Curvature ◽  
The North ◽  
Significant Difference ◽  
Different Seasons ◽  
Planting Season

ABSTRACT The aim of this study was to estimate the optimum plot size and number of replications in papaya field experiments. Eleven variables were evaluated in four cultivars of papaya with planting in different seasons between 2011 and 2013 in the north of the Espírito Santo state. Analysis were made from blank test applied to 240 selected for planting season and cultivate plants in commercial fields. The determination of optimum plot size was performed by applying the methodologies of modified maximum curvature and maximum curvature of coefficient of variation. The determination of the number of repetitions was taken from the least significant difference in average 20% and 30%. The optimum plot size proved the same by the two methods studied for most evaluations. The optimum size required differs among cultivars, between variables and between planting seasons, with the largest number of plants was required for the variables number of fruits per plant and yield per plant. We conclude that the optimal number of papaya plants planted in the field is six plants per plot using three replications.

scholarly journals Prediction of groundwater drawdown using artificial neural networks

2021 ◽  
Author(s):  
Vahid Gholami ◽  
Hossein Sahour
Keyword(s):  
Neural Network ◽  
Field Experiments ◽  
Accuracy Assessment ◽  
Field Measurements ◽  
Training Data ◽  
Validation Data ◽  
The North ◽  
Groundwater Drawdown ◽  
Ann Models ◽  
Artificial Neural

Abstract Groundwater drawdown is typically measured using pumping tests and field experiments; however, the traditional methods are time-consuming and costly when applied to extensive areas. In this research, a methodology is introduced based on artificial neural network (ANN)s and field measurements in an alluvial aquifer in the north of Iran. First, the annual drawdown as the output of the ANN models in 250 piezometric wells was measured, and the data were divided into three categories of training data, cross-validation data, and test data. Then, the effective factors in groundwater drawdown including groundwater depth, annual precipitation, annual evaporation, the transmissivity of the aquifer formation, elevation, distance from the sea, distance from water sources (recharge), population density, and groundwater extraction in the influence radius of each well (1000 m) were identified and used as the inputs of the ANN models. Several ANN methods were evaluated, and the predictions were compared with the observations. Results show that, the modular neural network (MNN) showed the highest performance in modeling groundwater drawdown ​​(Training R-sqr = 0.96, test R-sqr = 0.81). The optimum network was fitted to available input data to map the annual drawdown ​​across the entire aquifer. The accuracy assessment of the final map yielded favorable results (R-sqr = 0.8). The adopted methodology can be applied for the prediction of groundwater drawdown in the study site and similar settings elsewhere.

Field measurements of wave-induced pressure over wind-sea and swell

1991 ◽  
Vol 230 ◽  
pp. 391-428 ◽  
Author(s):  
Dieter Hasselmann ◽  
Jens Bösenberg
Keyword(s):  
North Sea ◽  
Field Experiments ◽  
Field Measurements ◽  
The North ◽  
Wave Decay ◽  
The North Sea ◽  
Mean Water Level ◽  
The Mean ◽  
Wind Sea ◽  
Wave Induced

Results of two field experiments in the North Sea are presented. Pressure was measured at two fixed heights above the mean water level and correlated with simultaneous wave height measurements. Roughly 90 hours of data have been analysed and the results are in agreement with earlier results obtained by Snyder et al. (1981). Measurements over swell give no indication of wave decay or growth for waves travelling faster than the wind or against the wind.

scholarly journals Brief communication: Supraglacial debris-cover changes in the Caucasus Mountains

2019 ◽  
Author(s):  
Levan G. Tielidze ◽  
Tobias Bolch ◽  
Roger D. Wheate ◽  
Stanislav S. Kutuzov ◽  
Ivan I. Lavrentiev ◽  
...  
Keyword(s):  
Morphological Type ◽  
Ice Age ◽  
Slope Aspect ◽  
Glacier Mass Balance ◽  
The Caucasus ◽  
Greater Caucasus ◽  
Time Period ◽  
Covered Area ◽  
Debris Cover ◽  
Caucasus Mountains

Abstract. Debris cover on glaciers can significantly alter melt, and hence, glacier mass balance and runoff. Debris coverage typically increases with shrinking glaciers. Here, we present data on debris cover and its changes for 559 glaciers located in different regions of the Greater Caucasus mountains based on 1986, 2000 and 2014 Landsat and SPOT images. Over this time period, the total glacier area decreased from 691.5 km2 to 590.0 km2 (0.52 % yr−1). Thereby, the debris covered area increased from ~ 11 to ~ 24 % on the northern, and from ~ 4 to 10 % on the southern macro-slope between 1986 and 2014. Overall, we found 18 % debris cover for the year 2014. With the glacier shrinkage, debris-covered area and the number of debris-covered glaciers increased as a function of elevation, slope, aspect, glacier morphological type, Little Ice Age moraines, and lithology.

To the North and the South, through the Great Caucasus Mountains

Antiquity ◽  
2021 ◽  
pp. 1-4
Author(s):  
Paul D. Wordsworth
Keyword(s):  
Archaeological Research ◽  
The South ◽  
The Caucasus ◽  
Interdisciplinary Work ◽  
The North ◽  
Linguistic Barriers ◽  
Caucasus Mountains

The publication of the British-Georgian exploration of Dariali Gorge (2013–2016) represents a substantial benchmark for the archaeology of the Caucasus, above all else for its multi-faceted approach. While numerous international and local projects continue a well-established tradition of archaeological research in the region, few have attempted the breadth of interdisciplinary work presented in this book. The result is a remarkably rich resource, illustrating to Anglophone academia in particular the archaeology of a region often portrayed as marginal. At the same time, the inclusion of a full synopsis in Georgian at the end of the volume (Naskidashvili) underscores the continued importance of collaboration across linguistic barriers.

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