Significant temporal changes in glacio isostatic adjustment in Iceland during the 1950s to present

2020 ◽  
Author(s):  
Halldór Geirsson ◽  
Gudmundur Valsson ◽  
Benedikt G. Ófeigsson ◽  
Erik Sturkell ◽  
Thora Arnadottir ◽  
...  
Keyword(s):  
Mass Balance ◽  
Vertical Motion ◽  
Mass Gain ◽  
Temporal Changes ◽  
Plate Motion ◽  
Glacier Mass Balance ◽  
Gps Measurements ◽  
Isostatic Adjustment ◽  
Regional Deformation ◽  
Uplift Rates

<p>The two most widespread geodynamic signals in Iceland are caused by glacio isostatic adjustment (GIA; up to 4.5 cm/yr vertical motion) and tectonic plate spreading (approximately 1.9 cm/yr horizontal motion). GPS measurements of crustal deformation started in Iceland in 1986 and annually tens to hundreds of benchmarks are re-measured. Many of these surveys are on local scales, but the ISNET campaigns in 1993, 2004, and 2016 are the only island-wide efforts. Continuous GPS (cGPS) measurements started in 1995 and now over 100 cGPS stations are running. The cGPS allows for excellent quantification of seasonal variations in position with amplitude up to several cm closest to the glaciers, driven mainly by seasonal snowload. Frequent observations also help to observe temporal changes in uplift rates and correlate to glacier mass balance. In recent years InSAR has been applied to obtain both local signals (e.g., due to glacial surges) and island-wide estimates of GIA and plate motion. However, InSAR does not work under the glaciers where we expect the largest uplift. Regular GPS measurements at several nunataks on Vatnajökull started in 2008 and provide the only intra-glacier GIA observations in Iceland. Going further backwards in time is a challenge and relies on local levelling where relative uplift rates can be compared to current relative uplift rates to infer the temporal evolution.</p><p>During 1993-2004 the average observed uplift rates reached at most around 2 cm/yr and were likely at its lowest in the early 1990s, lower than during 1959-1991. During 2004-2010 the uplift rates increased on average by 70% compared to the previous time period. A thin layer of ash from the 2010 Eyjafjallajökull eruption enhanced the melting rates and is clearly seen as enhanced uplift rates during 2010-2012. Until 2014 the uplift rates remained high. In 2014 the average uplift rates lowered by around 20%. Comparable changes are observed in the horizontal deformation field. Overall, recent changes in GIA broadly follow changes in climate and mass balance. The first part of the 90s was cold and glaciers in Iceland were overall in equilibrium or gaining a bit of mass. After 1995 the glaciers started losing considerable mass every year. From 2011 the mass loss decreased; in 2015 there was a net mass gain, and in 2017 and 2018 the mass balance was close to equilibrium. The highly variable deformation rates call for a re-evaluation of the current GIA models, working towards a time-dependent response that can be applied to regional deformation studies.</p>

scholarly journals Region-wide glacier mass balances over the Pamir-Karakoram-Himalaya during 1999–2011

2013 ◽  
Vol 7 (4) ◽  
pp. 1263-1286 ◽  
Author(s):  
J. Gardelle ◽  
E. Berthier ◽  
Y. Arnaud ◽  
A. Kääb
Keyword(s):  
Mass Balance ◽  
Western Himalaya ◽  
Mass Gain ◽  
Shuttle Radar Topography Mission ◽  
Eastern Himalaya ◽  
Glacier Mass Balance ◽  
Mass Balances ◽  
Grace Data ◽  
Stereo Imagery ◽  
Study Sites

Abstract. The recent evolution of Pamir-Karakoram-Himalaya (PKH) glaciers, widely acknowledged as valuable high-altitude as well as mid-latitude climatic indicators, remains poorly known. To estimate the region-wide glacier mass balance for 9 study sites spread from the Pamir to the Hengduan Shan (eastern Himalaya), we compared the 2000 Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) to recent (2008–2011) DEMs derived from SPOT5 stereo imagery. During the last decade, the region-wide glacier mass balances were contrasted with moderate mass losses in the eastern and central Himalaya (−0.22 ± 0.12 m w.e. yr−1 to −0.33 ± 0.14 m w.e. yr−1) and larger losses in the western Himalaya (−0.45 ± 0.13 m w.e. yr−1). Recently reported slight mass gain or balanced mass budget of glaciers in the central Karakoram is confirmed for a larger area (+0.10 ± 0.16 m w.e. yr−1) and also observed for glaciers in the western Pamir (+0.14 ± 0.13 m w.e. yr−1). Thus, the "Karakoram anomaly" should be renamed the "Pamir-Karakoram anomaly", at least for the last decade. The overall mass balance of PKH glaciers, −0.14 ± 0.08 m w.e. yr−1, is two to three times less negative than the global average for glaciers distinct from the Greenland and Antarctic ice sheets. Together with recent studies using ICESat and GRACE data, DEM differencing confirms a contrasted pattern of glacier mass change in the PKH during the first decade of the 21st century.

scholarly journals An evaluation of mass-balance methods applied to Castle creek Glacier, British Columbia, Canada

2014 ◽  
Vol 60 (220) ◽  
pp. 262-276 ◽  
Author(s):  
Matthew J. Beedle ◽  
Brian Menounos ◽  
Roger Wheate
Keyword(s):  
Mass Balance ◽  
Vertical Component ◽  
Glacier Mass Balance ◽  
Gps Measurements ◽  
Mountain Glacier ◽  
Temperature Index ◽  
Detailed Understanding ◽  
Index Model ◽  
Photogrammetric Method ◽  
Ice Velocity

AbstractWe estimate the glacier mass balance of a 9.5 km2 mountain glacier using three approaches for balance years 2009, 2010 and 2011. The photogrammetric, GPS and glaciological methods yielded sampling densities of 100, 5 and 2 points km-2, with measurement precisions of ± 0.40, ± 0.10 and ± 0.10 m w.e. respectively. Our glaciological measurements likely include a positive bias, due to omission of internal and basal mass balance, and uncertainty in determining the interface between snow and firn with a probe (±0.10 m w.e.). Measurements from our photogrammetric method include a negative bias introduced by the manual operator and our temperature index model used to correct for different dates of imaging (0.15 m w.e.), whereas GPS measurements avoid these biases. The photogrammetric and GPS methods are suitable for estimating glacier-wide annual mass balance, and thus provide a valuable measure that complements the glaciological method. These approaches, however, cannot be used to estimate mass balance at a point or mass-balance profiles without a detailed understanding of the vertical component of ice velocity.

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 Reduced ice mass loss and three-dimensional viscoelastic deformation in northern Antarctic Peninsula inferred from GPS

2020 ◽  
Vol 222 (2) ◽  
pp. 1013-1022 ◽  
Author(s):  
Nahidul Hoque Samrat ◽  
Matt A King ◽  
Christopher Watson ◽  
Andrew Hooper ◽  
Xianyao Chen ◽  
...  
Keyword(s):  
Mass Loss ◽  
Antarctic Peninsula ◽  
Upper Mantle ◽  
Three Dimensional ◽  
Plate Motion ◽  
Viscoelastic Deformation ◽  
Lithospheric Thickness ◽  
Isostatic Adjustment ◽  
Wide Range ◽  
Uplift Rates

SUMMARY We consider the viscoelastic rheology of the solid Earth under the Antarctic Peninsula due to ice mass loss that commenced after the breakup of the Larsen-B ice shelf. We extend the previous analysis of nearby continuous GPS time-series to include five additional years and the additional consideration of the horizontal components of deformation. They show strong uplift from ∼2002 to 2011 followed by reduced uplift rates to 2018. Modelling the GPS-derived uplift as a viscoelastic response to ongoing regional ice unloading from a new ice model confirms earlier estimates of low upper-mantle viscosities of ∼0.3–3 × 1018 Pa s in this region but allows a wide range of elastic lithosphere thickness. The observed and modelled north coordinate component shows little nonlinear variation due to the location of ice mass change to the east of the GPS sites. However, comparison of the observed and modelled east coordinate component constrains the upper-mantle viscosity to be less than ∼9 × 1018 Pa s, consistent with the viscosity range suggested by the uplift rates alone and providing important, largely independent, confirmation of that result. Our horizontal analysis showed only marginal sensitivity to modelled lithospheric thickness. The results for the horizontal components are sensitive to the adopted plate rotation model, with the estimate based on ITRF2014 suggesting that the sum of residual plate motion and pre-2002 glacial isostatic adjustment is likely less than ∼±0.5 mm yr−1 in the east component.

scholarly journals Antarctic ice-mass balance 2003 to 2012: regional reanalysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment based on GPS uplift rates

2013 ◽  
Vol 7 (5) ◽  
pp. 1499-1512 ◽  
Author(s):  
I. Sasgen ◽  
H. Konrad ◽  
E. R. Ivins ◽  
M. R. Van den Broeke ◽  
J. L. Bamber ◽  
...  
Keyword(s):  
Mass Balance ◽  
Regional Scale ◽  
Mass Movement ◽  
Glacial Isostatic Adjustment ◽  
Glacial Cycle ◽  
Amundsen Sea ◽  
Satellite Gravimetry ◽  
Isostatic Adjustment ◽  
Uplift Rates ◽  
Grace Satellite Gravimetry

Abstract. We present regional-scale mass balances for 25 drainage basins of the Antarctic Ice Sheet (AIS) from satellite observations of the Gravity and Climate Experiment (GRACE) for time period January 2003 to September 2012. Satellite gravimetry estimates of the AIS mass balance are strongly influenced by mass movement in the Earth interior caused by ice advance and retreat during the last glacial cycle. Here, we develop an improved glacial-isostatic adjustment (GIA) estimate for Antarctica using newly available GPS uplift rates, allowing us to more accurately separate GIA-induced trends in the GRACE gravity fields from those caused by current imbalances of the AIS. Our revised GIA estimate is considerably lower than previous predictions, yielding an estimate of apparent mass change of 53 ± 18 Gt yr−1. Therefore, our AIS mass balance of −114 ± 23 Gt yr−1 is less negative than previous GRACE estimates. The northern Antarctic Peninsula and the Amundsen Sea sector exhibit the largest mass loss (−26 ± 3 Gt yr−1 and −127 ± 7 Gt yr−1, respectively). In contrast, East Antarctica exhibits a slightly positive mass balance (26 ± 13 Gt yr−1), which is, however, mostly the consequence of compensating mass anomalies in Dronning Maud and Enderby Land (positive) and Wilkes and George V Land (negative) due to interannual accumulation variations. In total, 6% of the area constitutes about half the AIS imbalance, contributing 151 ± 7 Gt yr−1 (ca. 0.4 mm yr−1) to global mean sea-level change. Most of this imbalance is caused by ice-dynamic speed-up expected to prevail in the near future.

Non-climatic factors affecting glacier mass balance (on the example of avalanche nourishment)

2020 ◽  
Author(s):  
Alla Turchaninova ◽  
Sergey Sokratov ◽  
Yury Seliverstov ◽  
Dmitry Petrakov ◽  
Anton Lazarev ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climatic Factors ◽  
Mass Gain ◽  
Snow Accumulation ◽  
Tien Shan ◽  
Snow Avalanche ◽  
Glacier Mass Balance ◽  
Field Observations ◽  
Snow Avalanches ◽  
The Caucasus

<p>Glacier mass balance is affected by non-climatic factors such as topography, debris cover and geometric parameters of glaciers themselves, avalanche activity, volcanism, etc. The contribution of snow avalanches to the snow accumulation on a glacier is still among the least studied components of the glacier’s mass balance. We propose a possible approach for the numerical assessment of snow avalanche contribution to accumulation at mountain glaciers. The approach consists on the following steps: terrain analysis; weather data analysis; snow avalanche volume assessment during an analyzed balance year; numerical simulation of snow avalanches using RAMMS; evaluation of snow avalanche contribution to glacier accumulation. The proposed methodology was tested on three glaciers (Batysh Sook, № 354, Karabatkak) with an area up to 6,5 km<sup>2</sup> in the Inner Tien Shan and Kolka glacier with an area 1,2 km<sup>2</sup> in the Central Caucasus. To evaluate snow avalanche contribution to the winter accumulation, we reconstructed avalanche release zones that were most probably active during the analyzed balance year and corresponding snow fracture height in each zone. The numerical simulations of most probable released snow avalanches during the analyzed year using avalanche dynamics RAMMS software were performed and compared with the field observations and UAV orthophoto images. The outlines of avalanches deposits were realistically reproduced by RAMMS according to the results of field observations. The estimated contribution of snow avalanches to the accumulation on the studied glaciers during the analyzed balance year was as follows: Batysh Sook – 7,4±2,5%; № 354 – 2,2±0,7%; Karabatkak– 10,8±3,6% of the winter mass balance. In strong contradiction to the benchmark glaciers in the Tien Shan, the Kolka glacier demonstrates rapid mass gain in the Caucasus. It might be explained by significant, up to 80% share of avalanche nourishment to glacier mass gain. We note that avalanche-fed glaciers seem to be more stable at current stage of regional warming observed both in the Caucasus and the Tian Shan. The obtained results show the importance of the non-climatic factors for glacier surface mass balance control.</p>

Prediction of decadal slope changes in Canada by glacial isostatic adjustment modellingThis article is one of a series of papers published in this Special Issue on the theme GEODESY.

2009 ◽  
Vol 46 (8) ◽  
pp. 587-595 ◽  
Author(s):  
Wouter van der Wal ◽  
Alexander Braun ◽  
Patrick Wu ◽  
Michael G. Sideris
Keyword(s):  
North America ◽  
Land Surface ◽  
Lake Michigan ◽  
Vertical Motion ◽  
Glacial Isostatic Adjustment ◽  
Uplift Rate ◽  
Isostatic Adjustment ◽  
Uplift Rates ◽  
The Difference ◽  
Differential Uplift

In Canada, glacial isostatic adjustment (GIA) is the dominant process to cause vertical motion of the land surface. A GIA model is presented herein that can be used to predict slope changes at given locations in North America where GIA is the primary cause for vertical motion. Uncertainty in Pleistocene ice cover and viscosity in the Earth’s mantle prevent one from picking a single GIA model from the literature to predict uplift rates in the region. Therefore, in this study, a range of mantle viscosity values as well as two different ice-loading histories are used in a forward model of the GIA process. The combination of viscosities and ice model that gives the best fit to recently available continuous and episodic GPS observations is assumed to provide the best prediction of slope changes in North America. This model can be used to quantify GIA-induced vertical deformation in local geomorphologic studies. We show that the predicted differential uplift rate in the Nelson River with respect to Lake Winnipeg reaches 1 mm/year over a 200 km distance using the model that best fits the GPS data whereas the ICE-5Gv1.2/VM2 model gives a slightly larger value. The difference in uplift rate between the northern and southern shore of Lake Michigan amounts up to 3 mm/year (slightly larger than the ICE-5Gv1.2/VM2 model), which could lead to a change in shorelines of tens of metres horizontally over a period of 100 years.

scholarly journals Slight glacier mass loss in the Karakoram region during the 1970s to 2000 revealed by KH-9 images and SRTM DEM

2017 ◽  
Vol 63 (238) ◽  
pp. 331-342 ◽  
Author(s):  
YUSHAN ZHOU ◽  
ZHIWEI LI ◽  
JIA LI
Keyword(s):  
Climate Change ◽  
Mass Loss ◽  
Mass Balance ◽  
Average Rate ◽  
Stable State ◽  
Mass Gain ◽  
Glacier Mass Balance ◽  
Glacier Change ◽  
Srtm Dem ◽  
Global Average

ABSTRACTAn anomalously slight glacier mass gain during 2000 to the 2010s has recently been reported in the Karakoram region. However, to date, no investigations of the region-wide glacier mass balance in the Karakoram prior to 2000 have been reported, leaving a knowledge gap for assessing glacier responses to climate change. We calculated elevation and mass change using DEMs generated from KH-9 images acquired during 1973–1980 and the 1 arc-second SRTM DEM. We find a slight mass loss of −0.09 ± 0.03 m w.e. a−1 (12 366 km2) for 1973–2000, which is less negative than the global average rate for 1971–2009 (−0.31 ± 0.19 m w.e. a−1). Within the Karakoram, the glacier change patterns are spatially and temporally heterogeneous. In particular, a nearly stable state in the central Karakoram (−0.04 ± 0.05 m w.e. a−1 during the period 1974–2000) implies that the Karakoram anomaly dates back to the 1970s. Combined with the previous studies, we conclude that the Karakoram glaciers as a whole were in a nearly balanced state during the 1970s to the 2010s.

scholarly journals A Joint Inversion Estimate of Antarctic Ice Sheet Mass Balance Using Multi-Geodetic Data Sets

2019 ◽  
Vol 11 (6) ◽  
pp. 653 ◽  
Author(s):  
Chunchun Gao ◽  
Yang Lu ◽  
Zizhan Zhang ◽  
Hongling Shi
Keyword(s):  
Mass Balance ◽  
Joint Inversion ◽  
Ice Sheet ◽  
Mass Change ◽  
West Antarctica ◽  
Amundsen Sea ◽  
Antarctic Ice Sheet ◽  
Forward Models ◽  
Uplift Rates ◽  
The Antarctic

Many recent mass balance estimates using the Gravity Recovery and Climate Experiment (GRACE) and satellite altimetry (including two kinds of sensors of radar and laser) show that the ice mass of the Antarctic ice sheet (AIS) is in overall decline. However, there are still large differences among previously published estimates of the total mass change, even in the same observed periods. The considerable error sources mainly arise from the forward models (e.g., glacial isostatic adjustment [GIA] and firn compaction) that may be uncertain but indispensable to simulate some processes not directly measured or obtained by these observations. To minimize the use of these forward models, we estimate the mass change of ice sheet and present-day GIA using multi-geodetic observations, including GRACE and Ice, Cloud and land Elevation Satellite (ICESat), as well as Global Positioning System (GPS), by an improved method of joint inversion estimate (JIE), which enables us to solve simultaneously for the Antarctic GIA and ice mass trends. The GIA uplift rates generated from our JIE method show a good agreement with the elastic-corrected GPS uplift rates, and the total GIA-induced mass change estimate for the AIS is 54 ± 27 Gt/yr, which is in line with many recent GPS calibrated GIA estimates. Our GIA result displays the presence of significant uplift rates in the Amundsen Sea Embayment of West Antarctica, where strong uplift has been observed by GPS. Over the period February 2003 to October 2009, the entire AIS changed in mass by −84 ± 31 Gt/yr (West Antarctica: −69 ± 24, East Antarctica: 12 ± 16 and the Antarctic Peninsula: −27 ± 8), greater than the GRACE-only estimates obtained from three Mascon solutions (CSR: −50 ± 30, JPL: −71 ± 30, and GSFC: −51 ± 33 Gt/yr) for the same period. This may imply that single GRACE data tend to underestimate ice mass loss due to the signal leakage and attenuation errors of ice discharge are often worse than that of surface mass balance over the AIS.

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