Size specific steady-state accumulation-area ratio: an improvement for equilibrium-line estimation of small palaeoglaciers

2010 ◽  
Vol 29 (19-20) ◽  
pp. 2781-2787 ◽  
Author(s):  
Zoltán Kern ◽  
Péter László
Keyword(s):  
Steady State ◽  
Area Ratio ◽  
Equilibrium Line ◽  
Accumulation Area Ratio

scholarly journals Equilibrium-Line Altitudes and Paleoenvironment in the Merchants Bay Area, Baffin Island, N.W.T., Canada

1985 ◽  
Vol 31 (109) ◽  
pp. 205-213 ◽  
Author(s):  
Fred F. Hawkins
Keyword(s):  
Area Ratio ◽  
Equilibrium Line ◽  
Storm Tracks ◽  
Lateral Moraine ◽  
Baffin Island ◽  
Statistical Comparison ◽  
Bay Area ◽  
The North ◽  
Simple Geometry ◽  
Accumulation Area Ratio

AbstractThe fiordlands south of Merchants Bay contain an extensive, well-preserved moraine record of a late Foxe advance of local valley glaciers. This has allowed accurate reconstruction of former glacier margins and computation of former equilibrium-line altitudes (ELAs) by a variety of methods. Statistical comparison of three methods (maximum lateral-moraine elevation, median elevation, and accumulation area ratio (AAR)) shows that different techniques can give different results for the same glaciers. Lateral moraines gave estimates that were too low, probably due to post-glacial erosion or to non-deposition. Median elevations and the AAR method produced statistically similar results but only for glaciers of simple geometry. The median-elevation method fails to take into account variations in valley morphology and glaciological parameters, and so is not reliable in all situations. The AAR method is supported by empirical evidence and is the best of the three methods for estimating former ELAs.Analysis of trend surfaces of present and late Foxe ELAs shows changes in elevation and orientation through time due to changing environmental factors. Present ELAs are strongly influenced by local factors, southerly storm tracks, and warm maritime conditions. Paleo-ELAs do not show this influence, suggesting that Davis Strait may have been ice-covered during the late Foxe stade and that storm tracks were from the north.

scholarly journals Equilibrium-Line Altitudes and Paleoenvironment in the Merchants Bay Area, Baffin Island, N.W.T., Canada

1985 ◽  
Vol 31 (109) ◽  
pp. 205-213 ◽  
Author(s):  
Fred F. Hawkins
Keyword(s):  
Area Ratio ◽  
Equilibrium Line ◽  
Storm Tracks ◽  
Lateral Moraine ◽  
Baffin Island ◽  
Statistical Comparison ◽  
Bay Area ◽  
The North ◽  
Simple Geometry ◽  
Accumulation Area Ratio

AbstractThe fiordlands south of Merchants Bay contain an extensive, well-preserved moraine record of a late Foxe advance of local valley glaciers. This has allowed accurate reconstruction of former glacier margins and computation of former equilibrium-line altitudes (ELAs) by a variety of methods. Statistical comparison of three methods (maximum lateral-moraine elevation, median elevation, and accumulation area ratio (AAR)) shows that different techniques can give different results for the same glaciers. Lateral moraines gave estimates that were too low, probably due to post-glacial erosion or to non-deposition. Median elevations and the AAR method produced statistically similar results but only for glaciers of simple geometry. The median-elevation method fails to take into account variations in valley morphology and glaciological parameters, and so is not reliable in all situations. The AAR method is supported by empirical evidence and is the best of the three methods for estimating former ELAs.Analysis of trend surfaces of present and late Foxe ELAs shows changes in elevation and orientation through time due to changing environmental factors. Present ELAs are strongly influenced by local factors, southerly storm tracks, and warm maritime conditions. Paleo-ELAs do not show this influence, suggesting that Davis Strait may have been ice-covered during the late Foxe stade and that storm tracks were from the north.

scholarly journals The reaction of mountain glaciers to climatic change under continental conditions

1997 ◽  
Vol 24 ◽  
pp. 415-420 ◽  
Author(s):  
M. G. Kunakhovitch ◽  
A. M. Sokalskaya
Keyword(s):  
Steady State ◽  
Mass Balance ◽  
Tien Shan ◽  
Equilibrium Line ◽  
Mountain Glaciers ◽  
Meltwater Runoff ◽  
Glacier Runoff ◽  
Major River ◽  
Accumulation Area Ratio ◽  
Line Positions

Data on the distribution of accumulation with elevation were used to calculate ablation, internal accumulation, annual mass balance and glacier runoff for the Tien Shan glaciers with a total area of about 15 500 km2. The altitudinal profile of normalized ablation is approximated by an exponential curve. Mass-balance components and glacier runoff are calculated for the whole possible range of glacier equilibrium-line positions in the major river and lake basins of the Tien Shan. For steady state it was found that the equilibrium line rises from 3600 m in western areas to 4400 m in the east, whilst the accumulation area ratio and glacier runoff increase eastward from 63% to 71%, and from 600 to 1200 mm, respectively. Losses of meltwater runoff for internal accumulation average 7% (5–11%). In abnormally warm years, mass balance may reach –2300 mm w. e. in the west and –855 mm in the east and in the internal Tien Shan (Khan Tengry massif). Glacier runoff volume in those years has been estimated at 40 km3 year–1, which is 2.5 times as large as for the steady state.

scholarly journals The reaction of mountain glaciers to climatic change under continental conditions

1997 ◽  
Vol 24 ◽  
pp. 415-420
Author(s):  
M. G. Kunakhovitch ◽  
A. M. Sokalskaya
Keyword(s):  
Steady State ◽  
Mass Balance ◽  
Tien Shan ◽  
Equilibrium Line ◽  
Mountain Glaciers ◽  
Meltwater Runoff ◽  
Glacier Runoff ◽  
Major River ◽  
Accumulation Area Ratio ◽  
Line Positions

Data on the distribution of accumulation with elevation were used to calculate ablation, internal accumulation, annual mass balance and glacier runoff for the Tien Shan glaciers with a total area of about 15 500 km2. The altitudinal profile of normalized ablation is approximated by an exponential curve. Mass-balance components and glacier runoff are calculated for the whole possible range of glacier equilibrium-line positions in the major river and lake basins of the Tien Shan.For steady state it was found that the equilibrium line rises from 3600 m in western areas to 4400 m in the east, whilst the accumulation area ratio and glacier runoff increase eastward from 63% to 71%, and from 600 to 1200 mm, respectively. Losses of meltwater runoff for internal accumulation average 7% (5–11%).In abnormally warm years, mass balance may reach –2300 mm w. e. in the west and –855 mm in the east and in the internal Tien Shan (Khan Tengry massif). Glacier runoff volume in those years has been estimated at 40 km3 year–1, which is 2.5 times as large as for the steady state.

scholarly journals Estimating the avalanche contribution to the mass balance of debris covered glaciers

2014 ◽  
Vol 8 (1) ◽  
pp. 641-657 ◽  
Author(s):  
A. Banerjee ◽  
R. Shankar
Keyword(s):  
Steady State ◽  
Mass Balance ◽  
Western Himalaya ◽  
Area Ratio ◽  
Systematic Bias ◽  
Specific Mass ◽  
Model Estimate ◽  
High Head ◽  
Accumulation Area Ratio ◽  
The Himalaya

Abstract. Avalanche from high head walls dominates the net accumulation in many debris covered glaciers in the Himalaya. These avalanche contributions are difficult to directly measure and may cause a systematic bias in glaciological mass balance measurements. In this paper we develop a method to estimate the avalanche contribution using available data, within the context of an idealised flowline model of the glacier. We focus on Hamtah glacier in Western Himalaya and estimate the magnitude of the avalanche accumulation to its specific mass balance profile. Our estimate explains the reported discrepancy between values of recent glaciological and geodetic net mass balance for this glacier. Model estimate of accumulation area ratio (AAR) for this glacier is small (0.1) even at a steady state. This shows that empirical mass balance–AAR relationships derived from glaciers which do not have a significant avalanche contribution will not apply to a large region containing a significant fraction avalanche fed ones.

scholarly journals Testing the area–altitude balance ratio (AABR) and accumulation–area ratio (AAR) methods of calculating glacier equilibrium-line altitudes

2021 ◽  
pp. 1-12
Author(s):  
Rachel P. Oien ◽  
Brice R. Rea ◽  
Matteo Spagnolo ◽  
Iestyn D. Barr ◽  
Robert G. Bingham
Keyword(s):  
Time Series ◽  
Mass Balance ◽  
Area Ratio ◽  
Summer Temperature ◽  
Equilibrium Line ◽  
Field Observations ◽  
Median Difference ◽  
Accumulation Area Ratio

Abstract In this study, we compare equilibrium-line altitudes (ELAs) calculated using the area–altitude balance ratio (AABR) and the accumulation–area ratio (AAR) methods, with measured ELAs derived from direct field observations. We utilise a GIS toolbox to calculate the ELA for 64 extant glaciers by applying the AABR and AAR methods to DEMs and polygons of their geometry. The calculated ELAs (c-ELAs) are then compared to measured zero-net balance ELAs (znb-ELAs) obtained from mass-balance time series held by the WGMS for the same glaciers. The correlation between znb-ELAs and AABR (1.56)/AAR (0.58) c-ELAs is very strong, with an r2 = 0.99. The smallest median difference between znb-ELAs and c-ELAs (i.e. 65.5 m) is obtained when a globally representative AABR of 1.56 is used. When applied to palaeoglacier-climate applications, this difference translates to ~0.42°C, well within the uncertainty of palaeotemperature proxies used to determine mean summer temperature at the ELA. The more widely used mean AABR of 1.75 is shown to be statistically invalid due to the skewness of the dataset. On this basis, when calculating glacier ELAs, we recommend the use of a global AABR value of 1.56.

scholarly journals Altitudinal variations of temperature, equilibrium line altitude, and accumulation-area ratio in Upper Indus Basin

2016 ◽  
Vol 48 (1) ◽  
pp. 214-230 ◽  
Author(s):  
Biswajit Mukhopadhyay ◽  
Asif Khan
Keyword(s):  
Hydrological Modeling ◽  
Area Ratio ◽  
Temperature Data ◽  
Equilibrium Line ◽  
Indus Basin ◽  
Lapse Rate ◽  
Equilibrium Line Altitude ◽  
Upper Indus Basin ◽  
Temperature Equilibrium ◽  
Accumulation Area Ratio

Quantitative measures of adiabatic lapse rate, equilibrium line altitude (ELA), and accumulation-area ratio (AAR) are important to understand the hydrological processes and conduct hydrological modeling in a highly glaciated watershed. We present a detailed analysis of temperature data from 21 climatic stations, hypsometric analyses of glacier distributions, and a method to analyze ablation gradients and runoff curves concurrently to quantify these parameters for the watersheds of the Upper Indus Basin (UIB), with 15,062 km2 of glacierized area and an elevation range of 361–8,611 m. We show that the ELA varies considerably from one watershed to another, implying a highly variable upper elevation limit up to which melting of snows and glaciers takes place throughout the basin. This is in sharp contrast to the assertions made by previous researchers. We show that the ELA is as low as 4,840 m in Astore watershed and it is as high as 6,200 m in Shyok watershed. In accordance with the variation of ELA, the AAR also varies considerably from one watershed to another. It is as low as 0.10 in Gilgit and as high as 0.65 in Zanskar watersheds. We ascribe 15–20% uncertainty to these estimates of ELA and AAR in UIB.

scholarly journals Hypsometry and sensitivity of the mass balance to changes in equilibrium-line altitude: the case of the Southern Patagonia Icefield

2014 ◽  
Vol 60 (219) ◽  
pp. 14-28 ◽  
Author(s):  
Hernán De Angelis
Keyword(s):  
Mass Balance ◽  
Rate Sensitivity ◽  
Area Ratio ◽  
Area Fraction ◽  
Equilibrium Line ◽  
Equilibrium Line Altitude ◽  
First Order ◽  
Southern Patagonia ◽  
Accumulation Area Ratio ◽  
Balance Functions

AbstractWe study the relation between glacier hypsometry and sensitivity of mass-balance rate to changes in equilibrium-line altitude (ELA) to assess whether hypsometry can reliably be used to estimate the sensitivity of unmeasured glaciers to changes in ELA. We express the sensitivity of mass-balance rate to ELA, dḂ/ dELA, as a function of accumulation–area ratio (AAR), its derivative against altitude, dAAR/dELA, and mass-balance functions of ELA. We then apply the concept to 139 glaciers in the Southern Patagonia Icefield for which we derive hypsometry and AAR, and analyze the influence of hypsometry on their mass-balance rate sensitivity. We confirm that glaciers where the bulk of area is located above (below) the ELA are the least (most) sensitive. Glaciers with unimodal hypsometric curves where the peak of area fraction is around the present ELA, and glaciers with bi-or multimodal area distributions, with the ELA located approximately between the bulges, have intermediate sensitivities. We conclude that hypsometry can be used as a first-order estimator of mass-balance rate sensitivity to ELA change.

Equilibrium-line Altitudes of Late Quaternary Glaciers in the Southern Alps, New Zealand

1975 ◽  
Vol 5 (1) ◽  
pp. 27-47 ◽  
Author(s):  
Stephen C. Porter
Keyword(s):  
Late Holocene ◽  
Drainage Basin ◽  
Late Quaternary ◽  
Active Faults ◽  
Vertical Movement ◽  
Area Ratio ◽  
Southern Alps ◽  
Equilibrium Line ◽  
Accumulation Area Ratio ◽  
Geologic Data

AbstractEquilibrium-line altitudes (ELA's) of former glaciers in the Tasman River-Lake Pukaki drainage basin of the Southern Alps were reconstructed from glacial-geologic data on former ice limits by using an assumed accumulation-area ratio of 0.6 ± 0.05. Late Holocene (Neoglacial) ELA's were depressed 140 m below present levels, whereas those of four late Pleistocene ice advances were depressed 500 m (Birch Hill), 750 m (Tekapo), 875 m (Mt. John), and 1050 m (Balmoral). Reconstructed ELA gradients are approximately parallel to one another and range from 19 to 23 m km−1. Although vertical movement on active faults and isostatic tilting due to deglaciation have both contributed to modification of reconstructed ELA gradients from their original values, the maximum resulting effect probably amounts to less than 2.0 m km−1 and is undetectable from present data.

scholarly journals Characterization of Snow and Ice Reflectance Zones On Glaciers Using Landsat Thematic Mapper Data

1987 ◽  
Vol 9 ◽  
pp. 104-108 ◽  
Author(s):  
D.K. Hall ◽  
J.P. Ormsby ◽  
R.A. Bindschadler ◽  
H. Siddalingaiah
Keyword(s):  
Surface Temperature ◽  
Area Ratio ◽  
Thematic Mapper ◽  
Landsat Thematic Mapper ◽  
Ablation Area ◽  
Thematic Mapper Data ◽  
Glacier System ◽  
Accumulation Area Ratio ◽  
Snow And Ice

Landsat Thematic Mapper (TM) data have been analyzed to study the reflectivity characteristics of three glaciers: the Grossglockner mountain group of glaciers in Austria and the McCall and Meares Glaciers in Alaska, USA. The ratio of TM band 4 (0.76–0.90 μm) to TM band 5 (1.55–1.75 μm) was found to be useful for enhancing reflectivity differences on the glaciers. Using this ratio, distinct zones of similar reflectivity were noted on the Grossglockner mountain group of glaciers and on the Meares Glacier; no distinct zones were observed on the McCall Glacier. On the TM subscene containing the Grossglockner mountain group of glaciers, 28.2% of the glacierized area was determined to be in the zone corresponding most closely to the ablation area, and 71.8% with the location of the accumulation area. Using these measurements, the glacier system has an accumulation area ratio (AAR) of approximately 0.72. Within the accumulation area, two zones of different reflectivity were delineated. Radiometric surface temperatures were measured using TM band 6 (10.4–12.5 μm) on the Grossglockner mountain group of glaciers and on the Meares Glacier. The average radiometric surface temperature of the Grossglockner mountain group of glaciers decreased from 0.9 ± 0.34 °C in the ablation area, to −0.9 ± 0.83 C in the accumulation area.

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