scholarly journals Heterogeneous spatial and temporal pattern of surface elevation change and mass balance of the Patagonian icefields between 2000 and 2016

2018 ◽  
Author(s):  
Wael Abdel Jaber ◽  
Helmut Rott ◽  
Dana Floricioiu ◽  
Jan Wuite ◽  
Nuno Miranda
Keyword(s):  
Spatial Pattern ◽  
Mass Balance ◽  
Temporal Trend ◽  
Temporal Variations ◽  
Sar Interferometry ◽  
Surface Elevation ◽  
Radar Signal ◽  
Elevation Change ◽  
Mass Losses ◽  
Surface Elevation Change

Abstract. The Northern and Southern Patagonian icefields (NPI and SPI) have been subject to accelerated retreat during the last decades with considerable variability in magnitude and timing among individual glaciers. We derive spatially detailed maps of surface elevation change (SEC) of NPI and SPI from bistatic SAR interferometry data of SRTM and TanDEM-X for two epochs, 2000–2012 and 2012–2016 and provide data on changes in surface elevation and ice volume for the individual glaciers and for the icefields at large. We apply advanced TanDEM-X processing techniques allowing to cover 90 % and 95 % of the area of NPI and 97 % and 98 % of the area of SPI for the two epochs, respectively. Particular attention is paid to precisely coregistering the DEMs, assessing and accounting for possible effects of radar signal penetration through backscatter analysis, and correcting for seasonality biases in case of deviations in repeat DEM coverage from full annual time spans. The results show a different temporal trend between the two icefields and reveal a heterogeneous spatial pattern of SEC and mass balance caused by different sensitivities in respect to direct climatic forcing and ice flow dynamics of individual glaciers. The estimated volume change rates for NPI are −4.26 ± 0.20 km3 a−1 for epoch 1 and −5.60 ± 0.71 km3 a−1 for epoch 2, while for SPI these are −14.87 ± 0.51 km3 a−1 for epoch 1 and −11.86 ± 1.90 km3 a−1 for epoch 2. This amounts to 0.047 ± 0.005 mm a−1 eustatic sea level rise for both icefields during the epoch 2000–2016. On SPI the spatial pattern of surface elevation change is more complex than on NPI and the temporal trend is less uniform. On terminus sections of the main calving glaciers of SPI temporal variations of flow velocities are a main factor for differences in SEC between the two epochs. Striking differences are observed even on adjoining glaciers, such as Upsala Glacier with decreasing mass losses associated with slowdown of flow velocity between the two epochs, contrasting with acceleration and increase of mass losses on Viedma Glacier.

scholarly journals Heterogeneous spatial and temporal pattern of surface elevation change and mass balance of the Patagonian ice fields between 2000 and 2016

2019 ◽  
Vol 13 (9) ◽  
pp. 2511-2535 ◽  
Author(s):  
Wael Abdel Jaber ◽  
Helmut Rott ◽  
Dana Floricioiu ◽  
Jan Wuite ◽  
Nuno Miranda
Keyword(s):  
Spatial Pattern ◽  
Mass Balance ◽  
Temporal Trend ◽  
Sar Interferometry ◽  
Surface Elevation ◽  
Radar Signal ◽  
Elevation Change ◽  
Mass Losses ◽  
Digital Elevation ◽  
Surface Elevation Change

Abstract. The northern and southern Patagonian ice fields (NPI and SPI) have been subject to accelerated retreat during the last decades, with considerable variability in magnitude and timing among individual glaciers. We derive spatially detailed maps of surface elevation change (SEC) of NPI and SPI from bistatic synthetic aperture radar (SAR) interferometry data of the Shuttle Radar Topography Mission (SRTM) and TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X) for two epochs, 2000–2012 and 2012–2016, and provide data on changes in surface elevation and ice volume for the individual glaciers and the ice fields at large. We apply advanced TanDEM-X processing techniques allowing us to cover 90 % and 95 % of the area of NPI and 97 % and 98 % of SPI for the two epochs, respectively. Particular attention is paid to precisely co-registering the digital elevation models (DEMs), accounting for possible effects of radar signal penetration through backscatter analysis and correcting for seasonality biases in case of deviations in repeat DEM coverage from full annual time spans. The results show a different temporal trend between the two ice fields and reveal a heterogeneous spatial pattern of SEC and mass balance caused by different sensitivities with respect to direct climatic forcing and ice flow dynamics of individual glaciers. The estimated volume change rates for NPI are -4.26±0.20 km3 a−1 for epoch 1 and -5.60±0.74 km3 a−1 for epoch 2, while for SPI these are -14.87±0.52 km3 a−1 for epoch 1 and -11.86±1.99 km3 a−1 for epoch 2. This corresponds for both ice fields to an eustatic sea level rise of 0.048±0.002 mm a−1 for epoch 1 and 0.043±0.005 mm a−1 for epoch 2. On SPI the spatial pattern of surface elevation change is more complex than on NPI and the temporal trend is less uniform. On terminus sections of the main calving glaciers of SPI, temporal variations in flow velocities are a main factor for differences in SEC between the two epochs. Striking differences are observed even on adjoining glaciers, such as Upsala Glacier, with decreasing mass losses associated with slowdown of flow velocity, contrasting with acceleration and increase in mass losses on Viedma Glacier.

scholarly journals Surface elevation change and mass balance of Icelandic ice caps derived from swath mode CryoSat-2 altimetry

2016 ◽  
Vol 43 (23) ◽  
pp. 12,138-12,145 ◽  
Author(s):  
L. Foresta ◽  
N. Gourmelen ◽  
F. Pálsson ◽  
P. Nienow ◽  
H. Björnsson ◽  
...  
Keyword(s):  
Mass Balance ◽  
Surface Elevation ◽  
Elevation Change ◽  
Ice Caps ◽  
Surface Elevation Change

scholarly journals Glacier mass-balance determination by remote sensing and high-resolution modelling

2000 ◽  
Vol 46 (154) ◽  
pp. 491-498 ◽  
Author(s):  
Alun Hubbard ◽  
Ian Willis ◽  
Martin Sharp ◽  
Douglas Mair ◽  
Peter Nienow ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Mass Balance ◽  
Mass Flux ◽  
Surface Elevation ◽  
Surface Velocity ◽  
Elevation Change ◽  
Flux Divergence ◽  
Flow Modelling ◽  
Surface Elevation Change ◽  
Divergence Field

AbstractAn indirect methodology for determining the distribution of mass balance at high spatial resolution using remote sensing and ice-flow modelling is presented. The method, based on the mass-continuity equation, requires two datasets collected over the desired monitoring interval: (i) the spatial pattern of glacier surface-elevation change, and (ii) the mass-flux divergence field. At Haut Glacier d’Arolla, Valais, Switzerland, the mass-balance distribution between September 1992 and September 1993 is calculated at 20 m resolution from the difference between the pattern of surface-elevation change derived from analytical photogrammetry and the mass-flux divergence field determined from three-dimensional, numerical flow modelling constrained by surface-velocity measurements. The resultant pattern of mass balance is almost totally negative, showing a strong dependence on elevation, but with large localized departures. The computed distribution of mass balance compares well (R2 = 0.91) with mass-balance measurements made at stakes installed along the glacier centre line over the same period. Despite the highly optimized nature of the flow-modelling effort employed in this study, the good agreement indicates the potential this method has as a strategy for deriving high spatial and temporal-resolution estimates of mass balance.

scholarly journals Antarctic firn compaction rates from repeat-track airborne radar data: I. Methods

2015 ◽  
Vol 56 (70) ◽  
pp. 155-166 ◽  
Author(s):  
B. Medley ◽  
S.R.M. Ligtenberg ◽  
I. Joughin ◽  
M.R. Van den Broeke ◽  
S. Gogineni ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Radar Data ◽  
Temporal Variations ◽  
Mass Change ◽  
Surface Elevation ◽  
Elevation Change ◽  
Compaction Rate ◽  
Thickness Change ◽  
Surface Elevation Change ◽  
Spatio Temporal

AbstractWhile measurements of ice-sheet surface elevation change are increasingly used to assess mass change, the processes that control the elevation fluctuations not related to ice-flow dynamics (e.g. firn compaction and accumulation) remain difficult to measure. Here we use radar data from the Thwaites Glacier (West Antarctica) catchment to measure the rate of thickness change between horizons of constant age over different time intervals: 2009–10, 2010–11 and 2009–11. The average compaction rate to ~25 m depth is 0.33 m a−1, with largest compaction rates near the surface. Our measurements indicate that the accumulation rate controls much of the spatio-temporal variations in the compaction rate while the role of temperature is unclear due to a lack of measurements. Based on a semi-empirical, steady-state densification model, we find that surveying older firn horizons minimizes the potential bias resulting from the variable depth of the constant age horizon. Our results suggest that the spatio-temporal variations in the firn compaction rate are an important consideration when converting surface elevation change to ice mass change. Compaction rates varied by up to 0.12 m a−1 over distances <6 km and were on average >20% larger during the 2010–11 interval than during 2009–10.

scholarly journals Modeling of firn compaction for estimating ice-sheet mass change from observed ice-sheet elevation change

2011 ◽  
Vol 52 (59) ◽  
pp. 1-7 ◽  
Author(s):  
Jun Li ◽  
H. Jay Zwally
Keyword(s):  
Accumulation Rate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Temporal Variations ◽  
Mass Change ◽  
Surface Elevation ◽  
Effective Density ◽  
Elevation Change ◽  
Surface Elevation Change ◽  
Elevation Changes

AbstractChanges in ice-sheet surface elevation are caused by a combination of ice-dynamic imbalance, ablation, temporal variations in accumulation rate, firn compaction and underlying bedrock motion. Thus, deriving the rate of ice-sheet mass change from measured surface elevation change requires information on the rate of firn compaction and bedrock motion, which do not involve changes in mass, and requires an appropriate firn density to associate with elevation changes induced by recent accumulation rate variability. We use a 25 year record of surface temperature and a parameterization for accumulation change as a function of temperature to drive a firn compaction model. We apply this formulation to ICESat measurements of surface elevation change at three locations on the Greenland ice sheet in order to separate the accumulation-driven changes from the ice-dynamic/ablation-driven changes, and thus to derive the corresponding mass change. Our calculated densities for the accumulation-driven changes range from 410 to 610 kgm–3, which along with 900 kgm–3 for the dynamic/ablation-driven changes gives average densities ranging from 680 to 790 kgm–3. We show that using an average (or ‘effective’) density to convert elevation change to mass change is not valid where the accumulation and the dynamic elevation changes are of opposite sign.

scholarly journals Thinning of the Monte Perdido Glacier in the Spanish Pyrenees since 1981

2016 ◽  
Vol 10 (2) ◽  
pp. 681-694 ◽  
Author(s):  
Juan Ignacio López-Moreno ◽  
Jesús Revuelto ◽  
Ibai Rico ◽  
Javier Chueca-Cía ◽  
Asunción Julián ◽  
...  
Keyword(s):  
Mass Balance ◽  
Laser Scanning ◽  
Airborne Lidar ◽  
Surface Elevation ◽  
Aerial Photographs ◽  
Climate Data ◽  
Elevation Change ◽  
Factors Affecting ◽  
Digital Elevation ◽  
Surface Elevation Change

Abstract. This paper analyzes the evolution of the Monte Perdido Glacier, the third largest glacier in the Pyrenees, from 1981 to the present. We assessed the evolution of the glacier's surface area by analysis of aerial photographs from 1981, 1999, and 2006, and changes in ice volume by geodetic methods with digital elevation models (DEMs) generated from topographic maps (1981 and 1999), airborne lidar (2010) and terrestrial laser scanning (TLS, 2011, 2012, 2013, and 2014) data. We interpreted the changes in the glacier based on climate data from nearby meteorological stations. The results indicate that the degradation of this glacier accelerated after 1999. The rate of ice surface loss was almost three times greater during 1999–2006 than during earlier periods. Moreover, the rate of glacier thinning was 1.85 times faster during 1999–2010 (rate of surface elevation change  = −8.98 ± 1.80 m, glacier-wide mass balance  = −0.73 ± 0.14 m w.e. yr−1) than during 1981–1999 (rate of surface elevation change  = −8.35 ± 2.12 m, glacier-wide mass balance  = −0.42 ± 0.10 m w.e. yr−1). From 2011 to 2014, ice thinning continued at a slower rate (rate of surface elevation change  = −1.93 ± 0.4 m yr−1, glacier-wide mass balance  = −0.58 ± 0.36 m w.e. yr−1). This deceleration in ice thinning compared to the previous 17 years can be attributed, at least in part, to two consecutive anomalously wet winters and cool summers (2012–2013 and 2013–2014), counteracted to some degree by the intense thinning that occurred during the dry and warm 2011–2012 period. However, local climatic changes observed during the study period do not seem sufficient to explain the acceleration of ice thinning of this glacier, because precipitation and air temperature did not exhibit statistically significant trends during the study period. Rather, the accelerated degradation of this glacier in recent years can be explained by a strong disequilibrium between the glacier and the current climate, and likely by other factors affecting the energy balance (e.g., increased albedo in spring) and feedback mechanisms (e.g., heat emitted from recently exposed bedrock and debris covered areas).

Clustering patterns of volume change to classify glacier states and fates

2021 ◽  
Author(s):  
Lea Hartl ◽  
Kay Helfricht ◽  
Martin Stocker-Waldhuber ◽  
Bernd Seiser ◽  
Andrea Fischer
Keyword(s):  
Mass Balance ◽  
In Situ Monitoring ◽  
Surface Elevation ◽  
Elevation Change ◽  
Surface Change ◽  
Mountain Ranges ◽  
Digital Terrain ◽  
Terrain Models ◽  
Surface Elevation Change

&lt;div&gt; &lt;p&gt;Historically unprecedented glacier retreat rates are observed in&amp;#160;mountain ranges all over the world.&amp;#160;These high recession rates are expected to continue&amp;#160;during the next decades.&amp;#160;There is&amp;#160;currently a&amp;#160;window of opportunity to learn from&amp;#160;the&amp;#160;first vanishing Alpine glaciers&amp;#160;and&amp;#160;develop&amp;#160;monitoring strategies to track&amp;#160;the&amp;#160;pace and extent of a deglaciation phase.&amp;#160;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;Austria has a long history of in-situ mass balance monitoring at select glaciers, as well as a rich data basis of regional glacier inventories and multi-temporal digital terrain models from aerial surveys. As such, monitoring programs are in an ideal position to track the ongoing, rapid changes and place them in a historical context. With increasing rates of change it becomes all the more important to leverage the specific advantages&amp;#160;of&amp;#160;different data sets and combine them for a complete picture of regional changes and local processes.&amp;#160;&amp;#160;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;To this end, we compare long time series of annual mass balance data measured in-situ via the direct glaciological method at select&amp;#160;monitoring sites in western Austria with results derived from remote sensing based&amp;#160;digital terrain models. We use the latter to extract histograms of surface elevation change at hundreds of individual glaciers, over multiple time periods. This allows us to quantify the variability of surface elevation change and how it has changed in the past decades,&amp;#160;and provides&amp;#160;a basis for discussions of regional representativity of in-situ monitoring sites.&amp;#160;&amp;#160;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;Additionally, we use a&amp;#160;self-organizing&amp;#160;maps algorithm to cluster the individual &amp;#8220;profiles&amp;#8221; of surface elevation change into groups. This helps to visualize recurring patterns of change in specific geographic regions or elevation zones while preserving the characteristics of different, individual glaciers and their response to climatic forcing, and gives us a sense of&amp;#160;the state of disequilibrium of certain mountain ranges.&amp;#160;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;All available data indicates that recent years have been characterized by large area and volume losses, strongly negative mass balance values, and disintegration especially of&amp;#160;low-lying&amp;#160;glacier tongues.&amp;#160;Firn&amp;#160;cover has been strongly depleted so that some glaciers effectively no longer have accumulation zones. Variability of surface elevation change has generally increased at lower elevations and remained mostly constant at higher elevations, but this varies significantly between individual glaciers. The long-term in-situ monitoring sites skew to very large glaciers compared to the regional average.&amp;#160; Larger glaciers, including most of the monitoring sites, tend to exhibit a strong elevation gradient of surface change, with large losses at low elevations. Small glaciers typically have a less pronounced gradient, if any, and especially very small glaciers at lower elevations have significantly less negative elevation change values as large glaciers, in the same elevation zone. When clustering individual glaciers into types, we find a clear shift to surface change distribution curves that suggest processes of disintegration. This tendency is strongest in the most recent time period. At current rates of mass loss, glaciers are projected to retreat entirely to above 2800m in the &amp;#214;tztal and Stubai ranges by 2050.&amp;#160;&lt;/p&gt; &lt;/div&gt;

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