scholarly journals Balanced conditions or slight mass gain of glaciers in the Lahaul and Spiti region (northern India, Himalaya) during the nineties preceded recent mass loss

2013 ◽  
Vol 7 (2) ◽  
pp. 569-582 ◽  
Author(s):  
C. Vincent ◽  
Al. Ramanathan ◽  
P. Wagnon ◽  
D. P. Dobhal ◽  
A. Linda ◽  
...  
Keyword(s):  
Mass Loss ◽  
Field Measurements ◽  
Mass Gain ◽  
Negative Mass ◽  
Northern India ◽  
Chhota Shigri Glacier ◽  
Digital Elevation ◽  
Recent Compilation ◽  
Spiti Region ◽  
Dem Differencing

Abstract. The volume change of the Chhota Shigri Glacier (India, 32° 20 N, 77° 30' E) between 1988 and 2010 has been determined using in situ geodetic measurements. This glacier has experienced only a slight mass loss between 1988 and 2010 (−3.8 ± 2.0 m w.e. (water equivalent) corresponding to −0.17 ± 0.09 m w.e. yr−1). Using satellite digital elevation models (DEM) differencing and field measurements, we measure a negative mass balance (MB) between 1999 and 2010 (−4.8 ± 1.8 m w.e. corresponding to −0.44 ± 0.16 m w.e. yr−1). Thus, we deduce a slightly positive or near-zero MB between 1988 and 1999 (+1.0 ± 2.7 m w.e. corresponding to +0.09 ± 0.24 m w.e. yr−1). Furthermore, satellite DEM differencing reveals that the MB of the Chhota Shigri Glacier (−0.39 ± 0.15 m w.e. yr−1) has been only slightly less negative than the MB of a 2110 km2 glaciarized area in the Lahaul and Spiti region (−0.44 ± 0.09 m w.e. yr−1) during 1999−2011. Hence, we conclude that the ice wastage is probably moderate in this region over the last 22 yr, with near equilibrium conditions during the nineties, and an ice mass loss after. The turning point from balanced to negative mass budget is not known but lies probably in the late nineties and at the latest in 1999. This positive or near-zero MB for Chhota Shigri Glacier (and probably for the surrounding glaciers of the Lahaul and Spiti region) during at least part of the 1990s contrasts with a recent compilation of MB data in the Himalayan range that indicated ice wastage since 1975. However, in agreement with this compilation, we confirm more negative balances since the beginning of the 21st century.

scholarly journals Mass gain of glaciers in Lahaul and Spiti region (North India) during the nineties revealed by in-situ and satellite geodetic measurements

2012 ◽  
Vol 6 (5) ◽  
pp. 3733-3755 ◽  
Author(s):  
C. Vincent ◽  
A. Ramanathan ◽  
P. Wagnon ◽  
D. P. Dobhal ◽  
A. Linda ◽  
...  
Keyword(s):  
Mass Loss ◽  
Volume Change ◽  
Western Himalaya ◽  
North India ◽  
Good Correspondence ◽  
Chhota Shigri Glacier ◽  
Geodetic Measurements ◽  
Spiti Region ◽  
Dem Differencing

Abstract. The volume change of Chhota Shigri Glacier (India, 32° N) between 1988 and 2010 has been determined using in-situ geodetic measurements. This glacier has experienced only a slight mass loss over the last 22 yr (–3.8 ± 1.8 m w.e.). Using satellite digital elevation models (DEM) differencing and field measurements, we measure a negative mass balance (MB) between 1999 and 2011 (–4.7 ± 1.8 m w.e.). Thus, we deduce a positive MB between 1988 and 1999 (+1.0 ± 2.5 m w.e.). Furthermore, satellite DEM differencing reveals a good correspondence between the MB of Chhota Shigri Glacier and the MB of an over 2000 km2 glaciarized area in the Lahaul and Spiti region during 1999–2011. We conclude that there has been no large ice wastage in this region over the last 22 yr, ice mass loss being limited to the last decade. This contrasts to the most recent compilation of MB data in the Himalayan range that indicates ice wastage since 1975, accelerating after 1990. For the rest of western Himalaya, available observations of glacier MBs are too sparse and discontinuous to provide a clear and relevant regional pattern of glacier volume change over the last two decades.

scholarly journals Examining geodetic glacier mass balance in the eastern Pamir transition zone

2020 ◽  
Vol 66 (260) ◽  
pp. 927-937
Author(s):  
Mingyang Lv ◽  
Duncan J. Quincey ◽  
Huadong Guo ◽  
Owen King ◽  
Guang Liu ◽  
...  
Keyword(s):  
Mass Balance ◽  
Statistical Difference ◽  
Mass Gain ◽  
High Mountain ◽  
Glacier Mass Balance ◽  
Negative Mass ◽  
Glacier Surface ◽  
Digital Elevation ◽  
Elevation Changes ◽  
Individual Scale

AbstractGlaciers in the eastern Pamir have reportedly been gaining mass during recent decades, even though glaciers in most other regions in High Mountain Asia have been in recession. Questions still remain about whether the trend is strengthening or weakening, and how far the positive balances extend into the eastern Pamir. To address these gaps, we use three different digital elevation models to reconstruct glacier surface elevation changes over two periods (2000–09 and 2000–15/16). We characterize the eastern Pamir as a zone of transition from positive to negative mass balance with the boundary lying at the northern end of Kongur Tagh, and find that glaciers situated at higher elevations are those with the most positive balances. Most (67% of 55) glaciers displayed a net mass gain since the 21st century. This led to an increasing regional geodetic glacier mass balance from −0.06 ± 0.16 m w.e. a−1 in 2000–09 to 0.06 ± 0.04 m w.e. a−1 in 2000–15/16. Surge-type glaciers, which are prevalent in the eastern Pamir, showed fluctuations in mass balance on an individual scale during and after surges, but no statistical difference compared to non-surge-type glaciers when aggregated across the region.

scholarly journals Brief communication: Unabated wastage of the Juneau and Stikine icefields (southeast Alaska) in the early 21<sup>st</sup> century

2018 ◽  
Author(s):  
Etienne Berthier ◽  
Christopher Larsen ◽  
William Durkin ◽  
Michael Willis ◽  
Matthew Pritchard
Keyword(s):  
Mass Loss ◽  
Field Measurements ◽  
Radar Signal ◽  
Srtm Dem ◽  
Laser Altimetry ◽  
Southeast Alaska ◽  
Early 21St Century ◽  
The North ◽  
Digital Elevation ◽  
Geodetic Mass Balance

Abstract. The large Juneau and Stikine icefields (Alaska, JIF and SIF) lost mass rapidly in the second part of the 20th century. Laser altimetry, gravimetry and sparse field measurements suggest continuing mass loss in the early 21st century. However, two recent studies based on time series of SRTM and ASTER digital elevation models (DEMs) indicate a slowdown in mass loss after 2000. Here, the ASTER-based geodetic mass balance is recalculated, carefully avoiding the use of the SRTM DEM because of the unknown penetration depth of the C-Band radar signal. We find strongly negative mass balances from 2000 to 2016 (−0.68 ± 0.15 m w.e. a-1 for JIF and −0.83 ± 0.12 m w.e. a-1 for SIF), in agreement with laser altimetry, confirming that mass losses are continuing at unabated rates for both icefields. The SRTM DEM should be avoided or used very cautiously to estimate glacier volume change, especially in the North Hemisphere and over timescales of less than ~ 20 yrs.

scholarly journals Glacier Surface Mass Balance in the Suntar-Khayata Mountains, Northeastern Siberia

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1949 ◽  
Author(s):  
Yong Zhang ◽  
Xin Wang ◽  
Zongli Jiang ◽  
Junfeng Wei ◽  
Hiroyuki Enomoto ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
Surface Mass Balance ◽  
Negative Mass ◽  
Glacier Surface ◽  
Surface Mass ◽  
Northeastern Siberia ◽  
Response To Temperature ◽  
Rapid Mass

Arctic glaciers comprise a small fraction of the world’s land ice area, but their ongoing mass loss currently represents a large cryospheric contribution to the sea level rise. In the Suntar-Khayata Mountains (SKMs) of northeastern Siberia, in situ measurements of glacier surface mass balance (SMB) are relatively sparse, limiting our understanding of the spatiotemporal patterns of regional mass loss. Here, we present SMB time series for all glaciers in the SKMs, estimated through a glacier SMB model. Our results yielded an average SMB of −0.22 m water equivalents (w.e.) year−1 for the whole region during 1951–2011. We found that 77.4% of these glaciers had a negative mass balance and detected slightly negative mass balance prior to 1991 and significantly rapid mass loss since 1991. The analysis suggests that the rapidly accelerating mass loss was dominated by increased surface melting, while the importance of refreezing in the SMB progressively decreased over time. Projections under two future climate scenarios confirmed the sustained rapid shrinkage of these glaciers. In response to temperature rise, the total present glacier area is likely to decrease by around 50% during the period 2071–2100 under representative concentration pathway 8.5 (RCP8.5).

Correspondence between Site Amplification and Topographical, Geological Parameters: Collation of Data from Swiss and Japanese Stations, and Neural Networks-Based Prediction of Local Response

2021 ◽  
Author(s):  
Paolo Bergamo ◽  
Conny Hammer ◽  
Donat Fäh
Keyword(s):  
Frequency Response ◽  
Large Scale ◽  
Site Response ◽  
Low Frequency ◽  
Field Measurements ◽  
Site Amplification ◽  
Local Response ◽  
Regional Variability ◽  
Individual Site ◽  
Digital Elevation

ABSTRACT We address the relation between seismic local amplification and topographical and geological indicators describing the site morphology. We focus on parameters that can be derived from layers of diffuse information (e.g., digital elevation models, geological maps) and do not require in situ surveys; we term these parameters as “indirect” proxies, as opposed to “direct” indicators (e.g., f0, VS30) derived from field measurements. We first compiled an extensive database of indirect parameters covering 142 and 637 instrumented sites in Switzerland and Japan, respectively; we collected topographical indicators at various spatial extents and focused on shared features in the geological descriptions of the two countries. We paired this proxy database with a companion dataset of site amplification factors at 10 frequencies within 0.5–20 Hz, empirically measured at the same Swiss and Japanese stations. We then assessed the robustness of the correlation between individual site-condition indicators and local response by means of statistical analyses; we also compared the proxy-site amplification relations at Swiss versus Japanese sites. Finally, we tested the prediction of site amplification by feeding ensembles of indirect parameters to a neural network (NN) structure. The main results are: (1) indirect indicators show higher correlation with site amplification in the low-frequency range (0.5–3.33 Hz); (2) topographical parameters primarily relate to local response not because of topographical amplification effects but because topographical features correspond to the properties of the subsurface, hence to stratigraphic amplification; (3) large-scale topographical indicators relate to low-frequency response, smaller-scale to higher-frequency response; (4) site amplification versus indirect proxy relations show a more marked regional variability when compared with direct indicators; and (5) the NN-based prediction of site response is the best achieved in the 1.67–5 Hz band, with both geological and topographical proxies provided as input; topographical indicators alone perform better than geological parameters.

scholarly journals Glacier topography and elevation changes from Pléiades very high resolution stereo images

2014 ◽  
Vol 8 (5) ◽  
pp. 4849-4883 ◽  
Author(s):  
E. Berthier ◽  
C. Vincent ◽  
E. Magnússon ◽  
Á. Þ. Gunnlaugsson ◽  
P. Pitte ◽  
...  
Keyword(s):  
Field Measurements ◽  
Ground Control ◽  
European Alps ◽  
Control Points ◽  
Mass Balances ◽  
Ground Control Points ◽  
Digital Elevation ◽  
Stereo Imagery ◽  
Elevation Changes ◽  
Very High

Abstract. In response to climate change, most glaciers are losing mass and hence contribute to sea-level rise. Repeated and accurate mapping of their surface topography is required to estimate their mass balance and to extrapolate/calibrate sparse field glaciological measurements. In this study we evaluate the potential of Pléiades sub-meter stereo imagery to derive digital elevation models (DEMs) of glaciers and their elevation changes. Our five validation sites are located in Iceland, the European Alps, the Central Andes, Nepal and Antarctica. For all sites, nearly simultaneous field measurements were collected to evaluate the Pléiades DEMs. For Iceland, the Pléiades DEM is also compared to a Lidar DEM. The vertical biases of the Pléiades DEMs are less than 1 m if ground control points (GCPs) are used, but reach up to 6 m without GCPs. Even without GCPs, vertical biases can be reduced to a few decimetres by horizontal and vertical co-registration of the DEMs to reference altimetric data on ice-free terrain. Around these biases, the vertical precision of the Pléiades DEMs is ±1 m and even ±0.5 m on the flat glacier tongues (1-sigma confidence level). We also demonstrate the high potential of Pléiades DEMs for measuring seasonal, annual and multi-annual elevation changes with an accuracy of 1 m or better. The negative glacier-wide mass balances of the Argentière Glacier and Mer de Glace (−1.21 ± 0.16 and −1.19 ± 0.16 m.w.e. yr−1, respectively) are revealed by differencing SPOT5 and Pléiades DEMs acquired in August 2003 and 2012 demonstrating the continuing rapid glacial wastage in the Mont-Blanc area.

scholarly journals Calving event size measurements and statistics of Eqip Sermia, Greenland, from terrestrial radar interferometry

2020 ◽  
Vol 14 (3) ◽  
pp. 1051-1066 ◽  
Author(s):  
Andrea Walter ◽  
Martin P. Lüthi ◽  
Andreas Vieli
Keyword(s):  
Mass Loss ◽  
Greenland Ice Sheet ◽  
Model Fit ◽  
Simple Relationship ◽  
Outlet Glacier ◽  
Bed Topography ◽  
Digital Elevation ◽  
Global Sea Level ◽  
Log Normal ◽  
Observation Period

Abstract. Calving is a crucial process for the recently observed dynamic mass loss changes of the Greenland ice sheet. Despite its importance for global sea level change, major limitations in understanding the process of calving remain. This study presents high-resolution calving event data and statistics recorded with a terrestrial radar interferometer at the front of Eqip Sermia, a marine-terminating outlet glacier in Greenland. The derived digital elevation models with a spatial resolution of several metres recorded at 1 min intervals were processed to provide source areas and volumes of 906 individual calving events during a 6 d period. The calving front can be divided into sectors ending in shallow and deep water with different calving statistics and styles. For the shallow sector, characterized by an inclined and very high front, calving events are more frequent and larger than for the vertical ice cliff of the deep sector. We suggest that the calving volume deficiency of 90 % relative to the estimated ice flux in our observations of the deep sector is removed by oceanic melt, subaquatic calving, and small aerial calving events. Assuming a similar ice thickness for both sectors implies that subaqueous mass loss must be substantial for this sector with a contribution of up to 65 % to the frontal mass loss. The size distribution of the shallow sector is represented by a log-normal model, while for the deep sector the log-normal and power-law model fit well, but none of them are significantly better. Variations in calving activity and style between the sectors seem to be controlled by the bed topography and the front geometry. Within the short observation period no simple relationship between environmental forcings and calving frequency or event volume could be detected.

scholarly journals Non-rainfall Moisture: A Key Driver of Microbial Respiration from Standing Litter in Arid, Semiarid, and Mesic Grasslands

Ecosystems ◽  
2019 ◽  
Vol 23 (6) ◽  
pp. 1154-1169 ◽  
Author(s):  
Sarah Evans ◽  
Katherine E. O. Todd-Brown ◽  
Kathryn Jacobson ◽  
Peter Jacobson
Keyword(s):  
Mass Loss ◽  
Litter Decomposition ◽  
Tallgrass Prairie ◽  
Field Measurements ◽  
High Humidity ◽  
Microbial Response ◽  
Improve Model ◽  
Arid Desert ◽  
Physical Features ◽  
Standing Litter

Abstract Models assume that rainfall is the major moisture source driving decomposition. Non-rainfall moisture (NRM: high humidity, dew, and fog) can also induce standing litter decomposition, but there have been few measurements of NRM-mediated decomposition across sites and no efforts to extrapolate the contribution of NRM to larger scales to assess whether this mechanism can improve model predictions. Here, we show that NRM is an important, year-round source of moisture in grassland sites with contrasting moisture regimes using field measurements and modeling. We first characterized NRM frequency and measured NRM-mediated decomposition at two sites in the Namib Desert, Namibia (hyper-arid desert), and at one site in Iowa, USA (tallgrass prairie). NRM was frequent at all sites (85–99% of hours that litter was likely to be wet were attributed to NRM) and tended to occur in cool, high-humidity periods for several hours or more at a time. NRM also resulted in CO2 release from microbes in standing litter at all sites when litter became sufficiently wet (> 5% gravimetric moisture for fine litter and > 13% for coarse), and significantly contributed to mass loss, particularly in the western Namib site that received almost no rain. When we modeled annual mass loss induced by NRM and rain and extrapolated our characterization of NRM decomposition to a final semiarid site (Sevilleta, New Mexico), we found that models driven by rainfall alone underestimated mass loss, while including NRM resulted in estimates within the range of observed mass loss. Together these findings suggest that NRM is an important missing component in quantitative and conceptual models of litter decomposition, but there is nuance involved in modeling NRM at larger scales. Specifically, temperature and physical features of the substrate emerge as factors that affect the microbial response to litter wetting under NRM in our sites, and require further study. Hourly humidity can provide an adequate proxy of NRM frequency, but site-specific calibration with litter wetness is needed to accurately attribute decomposition to periods when NRM wets litter. Greater recognition of NRM-driven decomposition and its interaction with other processes like photodegradation is needed, especially since fog, dew, and humidity are likely to shift under future climates.

scholarly journals Mapping glaciers in Jotunheimen, South-Norway, during the "Little Ice Age" maximum

2009 ◽  
Vol 3 (2) ◽  
pp. 231-243 ◽  
Author(s):  
S. Baumann ◽  
S. Winkler ◽  
L. M. Andreassen
Keyword(s):  
Little Ice Age ◽  
18Th Century ◽  
Field Measurements ◽  
Geographical Information ◽  
Ice Age ◽  
Inventory Data ◽  
Digital Elevation ◽  
Remote Sensing Techniques ◽  
Southern Norway ◽  
Elevation Model

Abstract. The maximum glacier extent during the "Little Ice Age" (mid 18th century AD) in Jotunheimen, southern Norway, was mapped using remote sensing techniques. Interpretation of existing glaciochronological studies, analysis of geomorphological maps, and own GPS-field measurements were applied for validation of the mapping. The length of glacier centrelines and other inventory data were determined using a Geographical Information System (GIS) and a Digital Elevation Model. "Little Ice Age" maximum extent for a total of 233 glaciers comprising an overall glacier area of about 290 km2 was mapped. Mean length of the centreline was calculated to 1.6 km. Until AD 2003, the area and length shrank by 35% and 34%, respectively, compared with the maximum "Little Ice Age" extent.

Assessing Freeze-Thaw Damage in Segmental Retaining Walls Units by Mass Loss, Moisture Gain, and Relative Dynamic Modulus

2019 ◽  
Vol 2673 (11) ◽  
pp. 309-318
Author(s):  
Cesar T. Chan ◽  
Kenneth C. Hover
Keyword(s):  
Moisture Content ◽  
Mass Loss ◽  
Dynamic Modulus ◽  
Moisture Absorption ◽  
Surface Damage ◽  
Mass Gain ◽  
Retaining Walls ◽  
Freeze Thaw ◽  
Cast Concrete ◽  
The Relationship

Segmental retaining walls (SRWs) constructed of dry-cast concrete masonry units are used in transportation-related applications for which freeze-thaw (FT) durability is evaluated on the basis of percent mass-loss accumulated after multiple FT cycles as per ASTM C1262. This study compared mass loss, mass gain owing to absorption during (FT) exposure, and relative dynamic modulus (RDM) as per ASTM C215. Application of RDM required accounting for the influence of the shape and moisture content of SRW coupons on resonant frequency, with corrections that are likewise applicable to ASTM C666 for ordinary concrete. It was demonstrated that mass loss does not exclusively indicate surface damage, and the relationship between mass loss and RDM is unique to each specimen. Mass gain (as moisture absorption) during testing emerged as a key index of damage, with rapid escalation of mass loss and reduction in RDM at the number of FT cycles required to increase the moisture content of the residual coupon by about 1%.

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