Mass changes in Arctic ice caps and glaciers: implications of regionalizing elevation changes

Abstract. The mass balance of glaciers and ice caps is sensitive to changing climate conditions. The mass changes derived in this study are determined from elevation changes derived measured by the Ice, Cloud, and land Elevation Satellite (ICESat) for the time period 2003–2009. Four methods, based on interpolation and extrapolation, are used to regionalize these elevation changes to areas without satellite coverage. A constant density assumption is then applied to estimate the mass change by integrating over the entire glaciated region. The main purpose of this study is to investigate the sensitivity of the regional mass balance of Arctic ice caps and glaciers to different regionalization schemes. The sensitivity analysis is based on studying the spread of mass changes and their associated errors, and the suitability of the different regionalization techniques is assessed through cross-validation. The cross-validation results shows comparable accuracies for all regionalization methods, but the inferred mass change in individual regions, such as Svalbard and Iceland, can vary up to 4 Gt a−1, which exceeds the estimated errors by roughly 50% for these regions. This study further finds that this spread in mass balance is connected to the magnitude of the elevation change variability. This indicates that care should be taken when choosing a regionalization method, especially for areas which exhibit large variability in elevation change.

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Mass change of Arctic ice caps and glaciers: implications of regionalizing elevation changes

The Cryosphere Discussions ◽

10.5194/tcd-7-5889-2013 ◽

2013 ◽

Vol 7 (6) ◽

pp. 5889-5920 ◽

Cited By ~ 2

Author(s):

J. Nilsson ◽

L. Sandberg Sørensen ◽

V. R. Barletta ◽

R. Forsberg

Keyword(s):

Mass Balance ◽

Satellite Altimetry ◽

Mass Change ◽

The Arctic ◽

Elevation Change ◽

Ice Caps ◽

Annual Variability ◽

Change Pattern ◽

Elevation Changes ◽

Arctic Ice

Abstract. Recent studies have determined mass changes of Arctic ice caps and glaciers from satellite altimetry. Determining regional mass balance of ice caps and glaciers using this technique is inherently difficult due to their size and geometry. Furthermore these studies have mostly relied on one method or the same types of methods to determine the regional mass balance, by extrapolating elevation changes using their relation to elevation. This makes the estimation of mass balance heavily dependent on the method used to regionalize the elevation changes. Left without consideration large discrepancies can arise in the mass change estimates and the interpretation of them. In this study we use Ice, Cloud, and land Elevation Satellite (ICESat) derived elevation changes from 2003–2009 and determine the impact of different regionalizing schemes on the mass change estimates of the Arctic ice caps and glaciers. Four different methods, based on interpolation and extrapolation of the elevation changes were used to quantify this effect on the regional mass changes. Secondly, a statistical criteria was developed to determine the optimum method for each region in order to derive robust mass changes and reduce the need of external validation data. In this study we found that the range or spread of the estimated mass changes, for the different regions, was highly correlated to the inter-annual variability of the elevation changes, driven by the different climatic conditions of the regions. Regions affected by a maritime climate show a large range in estimated values, on average 1.5–2 times larger than the predicted errors. For regions in a continental regime the opposite was observed, and the range of the values lies well inside the error estimates. We also found that the extrapolation methods tend on average to produce more negative values than the interpolation methods and that our four methods do not fully reproduce the original histogram. Instead, they produce more negative distributions than the original which may indicate that previous and these current estimates using ICESat observations might be overestimate by as much as 4–19%, depending on region. This should therefore be taken into account when deriving regional mass balance from satellite altimetry in regions which show high inter-annual variability of elevation changes. In these regions several different independent methods should be used to capture the elevation change pattern and then analyzed to determine the most suitable method. For regions in a continental climate regime, and with low variability of elevation changes, a single method may be sufficient to capture the regional elevation change pattern and hence mass balance.

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Runaway thinning of the low-elevation Yakutat Glacier, Alaska, and its sensitivity to climate change

Journal of Glaciology ◽

10.3189/2015jog14j125 ◽

2015 ◽

Vol 61 (225) ◽

pp. 65-75 ◽

Cited By ~ 12

Author(s):

Barbara L. Trüssel ◽

Martin Truffer ◽

Regine Hock ◽

Roman J. Motyka ◽

Matthias Huss ◽

...

Keyword(s):

Mass Loss ◽

Mass Balance ◽

Mass Change ◽

Balance Model ◽

Surface Mass Balance ◽

Elevation Change ◽

Southeast Alaska ◽

Surface Mass ◽

Climate Conditions ◽

Decadal Scale

AbstractLake-calving Yakutat Glacier in southeast Alaska, USA, is undergoing rapid thinning and terminus retreat. We use a simplified glacier model to evaluate its future mass loss. In a first step we compute glacier-wide mass change with a surface mass-balance model, and add a mass loss component due to ice flux through the calving front. We then use an empirical elevation change curve to adjust for surface elevation change of the glacier and finally use a flotation criterion to account for terminus retreat due to frontal ablation. Surface mass balance is computed on a daily timescale; elevation change and retreat is adjusted on a decadal scale. We use two scenarios to simulate future mass change: (1) keeping the current (2000–10) climate and (2) forcing the model with a projected warming climate. We find that the glacier will disappear in the decade before 2110 or 2070 under constant or warming climates, respectively. For the first few decades, the glacier can maintain its current thinning rates by retreating and associated loss of high-ablating, low-elevation areas. However, once higher elevations have thinned substantially, the glacier can no longer counteract accelerated thinning by retreat and mass loss accelerates, even under constant climate conditions. We find that it would take a substantial cooling of 1.5°C to reverse the ongoing retreat. It is therefore likely that Yakutat Glacier will continue its retreat at an accelerating rate and disappear entirely.

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Elevation changes measured on Svalbard glaciers and ice caps from airborne laser data

Annals of Glaciology ◽

10.3189/172756405781813131 ◽

2005 ◽

Vol 42 ◽

pp. 202-208 ◽

Cited By ~ 43

Author(s):

Jonathan L. Bamber ◽

William Krabill ◽

Vivienne Raper ◽

Julian A. Dowdeswell ◽

J. Oerlemans

Keyword(s):

Mass Balance ◽

Elevation Change ◽

Svalbard Archipelago ◽

Ice Caps ◽

Airborne Laser ◽

Air Temperatures ◽

Lower Elevation ◽

Elevation Changes ◽

The Mean ◽

Negative Balance

AbstractPrecise airborne laser surveys were conducted during spring in 1996 and 2002 on 17 ice caps and glaciers in the Svalbard archipelago covering the islands of Spitsbergen and Nordaustlandet. We present the derived elevation changes. Lower-elevation glaciers in south Spitsbergen show the largest thinning rates of ∼ 0.5 m a-1, while some of the higher, more northerly ice caps appear to be close to balance. The pattern of elevation change is complex, however, due to several factors including glacier aspect, microclimatological influences and the high natural annual variability in local accumulation and ablation rates. Anomalous changes were observed on Fridtjovbreen, which started surging in 1996, at the start of the measurement period. On this glacier, thinning (of > 0.6 m a-1) was observed in the accumulation area, coincident with thickening at lower elevations. Asymmetric thinning was found on two ice caps on Nordaustlandet, with the largest values on the eastern side of Vestfonna but the western slopes of Vegafonna. The mean elevation change for all ice masses was -0.19 m a-1 w.e., which is 1.6 times the net mass-balance value determined for the last 30 years. Using mass-balance sensitivity estimates for Svalbard suggests that the implied increase in negative balance is linked to warmer air temperatures in the late 1990s. Multiple linear regression suggests that mass balance is most closely correlated with latitude, rather than mean altitude or longitude.

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Surface elevation changes during 2007–13 on Bowdoin and Tugto Glaciers, northwestern Greenland

Journal of Glaciology ◽

10.1017/jog.2016.106 ◽

2016 ◽

Vol 62 (236) ◽

pp. 1083-1092 ◽

Cited By ~ 14

Author(s):

SHUN TSUTAKI ◽

SHIN SUGIYAMA ◽

DAIKI SAKAKIBARA ◽

TAKANOBU SAWAGAKI

Keyword(s):

Mass Balance ◽

Satellite Observations ◽

Surface Elevation ◽

Surface Mass Balance ◽

Elevation Change ◽

Predominant Role ◽

Ice Dynamics ◽

Surface Mass ◽

Elevation Changes ◽

Negative Surface

ABSTRACTTo quantify recent thinning of marine-terminating outlet glaciers in northwestern Greenland, we carried out field and satellite observations near the terminus of Bowdoin Glacier. These data were used to compute the change in surface elevation from 2007 to 2013 and this rate of thinning was then compared with that of the adjacent land-terminating Tugto Glacier. Comparing DEMs of 2007 and 2010 shows that Bowdoin Glacier is thinning more rapidly (4.1 ± 0.3 m a−1) than Tugto Glacier (2.8 ± 0.3 m a−1). The observed negative surface mass-balance accounts for <40% of the elevation change of Bowdoin Glacier, meaning that the thinning of Bowdoin Glacier cannot be attributable to surface melting alone. The ice speed of Bowdoin Glacier increases down-glacier, reaching 457 m a−1 near the calving front. This flow regime causes longitudinal stretching and vertical compression at a rate of −0.04 a−1. It is likely that this dynamically-controlled thinning has been enhanced by the acceleration of the glacier since 2000. Our measurements indicate that ice dynamics indeed play a predominant role in the rapid thinning of Bowdoin Glacier.

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An optimized method to calculate the geodetic mass balance of mountain glaciers

Journal of Glaciology ◽

10.1017/jog.2018.79 ◽

2018 ◽

Vol 64 (248) ◽

pp. 917-931 ◽

Cited By ~ 1

Author(s):

RUBÉN BASANTES-SERRANO ◽

ANTOINE RABATEL ◽

CHRISTIAN VINCENT ◽

PASCAL SIRGUEY

Keyword(s):

Spatial Variability ◽

Mass Balance ◽

Mean Difference ◽

Full Density ◽

Elevation Change ◽

Low Contrast ◽

Mountain Glaciers ◽

Elevation Changes ◽

Geodetic Mass Balance ◽

Similar Accuracy

ABSTRACTUnderstanding the effects of climate on glaciers requires precise estimates of ice volume change over several decades. This is achieved by the geodetic mass balance computed by two means: (1) the digital elevation model (DEM) comparison (SeqDEM) allows measurements over the entire glacier, however the low contrast over glacierized areas is an issue for the DEM generation through the photogrammetric techniques and (2) the profiling method (SePM) is a faster alternative but fails to capture the spatial variability of elevation changes. We present a new framework (SSD) that relies upon the spatial variability of the elevation change to densify a sampling network to optimize the surface-elevation change quantification. Our method was tested in two small glaciers over different periods. We conclude that the SePM overestimates the elevation change by ~20% with a mean difference of ~1.00 m (root mean square error (RMSE) = ~3.00 m) compared with results from the SeqDEM method. A variogram analysis of the elevation changes showed a mean difference of <0.10 m (RMSE = ~2.40 m) with SSD approach. A final assessment on the largest glacier in the French Alps confirms the high potential of our method to compute the geodetic mass balance, without going through the generation of a full-density DEM, but with a similar accuracy than the SeqDEM approach.

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CryoSat-2 delivers monthly and inter-annual surface elevation change for Arctic ice caps

The Cryosphere Discussions ◽

10.5194/tcd-9-2821-2015 ◽

2015 ◽

Vol 9 (3) ◽

pp. 2821-2865 ◽

Cited By ~ 2

Author(s):

L. Gray ◽

D. Burgess ◽

L. Copland ◽

M. N. Demuth ◽

T. Dunse ◽

...

Keyword(s):

Snow Accumulation ◽

Surface Elevation ◽

Radar Altimeter ◽

Elevation Change ◽

Ice Caps ◽

Ice Cap ◽

Winter Snow ◽

Surface Elevation Change ◽

Devon Ice Cap ◽

Arctic Ice

Abstract. We show that the CryoSat-2 radar altimeter can provide useful estimates of surface elevation change on a variety of Arctic ice caps, on both monthly and yearly time scales. Changing conditions, however, can lead to a varying bias between the elevation estimated from the radar altimeter and the physical surface due to changes in the contribution of subsurface to surface backscatter. Under melting conditions the radar returns are predominantly from the surface so that if surface melt is extensive across the ice cap estimates of summer elevation loss can be made with the frequent coverage provided by CryoSat-2. For example, the average summer elevation decreases on the Barnes Ice Cap, Baffin Island, Canada were 2.05 ± 0.36 m (2011), 2.55 ± 0.32 m (2012), 1.38 ± 0.40 m (2013) and 1.44 ± 0.37 m (2014), losses which were not balanced by the winter snow accumulation. As winter-to-winter conditions were similar, the net elevation losses were 1.0 ± 0.2 m (winter 2010/2011 to winter 2011/2012), 1.39 ± 0.2 m (2011/2012 to 2012/2013) and 0.36 ± 0.2 m (2012/2013 to 2013/2014); for a total surface elevation loss of 2.75 ± 0.2 m over this 3 year period. In contrast, the uncertainty in height change results from Devon Ice Cap, Canada, and Austfonna, Svalbard, can be up to twice as large because of the presence of firn and the possibility of a varying bias between the true surface and the detected elevation due to changing year-to-year conditions. Nevertheless, the surface elevation change estimates from CryoSat for both ice caps are consistent with field and meteorological measurements. For example, the average 3 year elevation difference for footprints within 100 m of a repeated surface GPS track on Austfonna differed from the GPS change by 0.18 m.

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

Geophysical Research Letters ◽

10.1002/2016gl071485 ◽

2016 ◽

Vol 43 (23) ◽

pp. 12,138-12,145 ◽

Cited By ~ 32

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

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

Annals of Glaciology ◽

10.3189/172756411799096321 ◽

2011 ◽

Vol 52 (59) ◽

pp. 1-7 ◽

Cited By ~ 40

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.

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Contrasting glacier variations of Glaciar Perito Moreno and Glaciar Ameghino, Southern Patagonia Icefield

Annals of Glaciology ◽

10.3189/2015aog70a020 ◽

2015 ◽

Vol 56 (70) ◽

pp. 26-32 ◽

Cited By ~ 12

Author(s):

Masahiro Minowa ◽

Shin Sugiyama ◽

Daiki Sakakibara ◽

Takanobu Sawagaki

Keyword(s):

Mass Balance ◽

Area Ratio ◽

Elevation Change ◽

Climate Conditions ◽

Altitude Profile ◽

The Past ◽

Surface Elevation Change ◽

Southern Patagonia ◽

Accumulation Area Ratio ◽

Strong Control

AbstractGlaciar Perito Moreno (GPM) and Glaciar Ameghino (GA), Southern Patagonia Icefield, are in contact in the accumulation area, but have shown contrasting frontal variations in the past few decades. To investigate recent changes of the two glaciers and processes controlling the different responses to similar climate conditions, we measured surface elevation change from 2000 to 2008 and terminus positions from 1999 to 2012 using several types of satellite data. GPM shows no significant changes in terminus position and 0.4 ± 0.3 m a–1 thickening over the period, whereas GA retreated 55 ± 2 m a–1 and thinned 2.6 ± 0.3 m a–1. Mass-balance measurements over the period 1999/2000 show that accumulation at GPM was ten times greater than that at GA, but ablation was only three times greater. The mass-balance–altitude profile is similar for the two glaciers; differences in the mass-balance distribution are caused by differences in the accumulation–area ratio (AAR). Our results suggest that the AAR and the calving flux exert strong control on the evolution of glaciers in the region.

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Numerical modelling assessment of glacier surge impact on observed elevation change signals

10.5194/egusphere-egu21-14874 ◽

2021 ◽

Author(s):

Andreas Vieli

Keyword(s):

Large Population ◽

Regional Scale ◽

Mass Gain ◽

Climate Forcing ◽

Mass Change ◽

Elevation Change ◽

Elevation Changes ◽

Glacier Surges ◽

The Mean ◽

The Impact

Glacier surges periodically move ice masses to lower elevations and hence produce dynamic patterns of substantial thinning and thickening, but the net mass change over a typical time period of elevation change assessment of a few years to decades is not obvious. &#160;Surging glaciers may therefore affect regional scale elevation change assessments as acquired from differencing of remotely sensed elevations, as for example for the observed Karakoram mass gain anomaly.In this study I synthetically model glacier surges for a range of glacier sizes (slopes, thicknesses) and investigate the impact on the surface elevation change and total mass change for a typical range of surge durations, intensities and periods.When keeping the climate forcing constant I find that the mean glacier elevation (or volume) is almost symmetric around the surge phase. Hence, when sampling elevation change over a large population of glaciers with randomly occurring surges there is little impact on the detected average elevation changes over all glaciers. The exceptions are steep glaciers which produce very short advance phases and much more extended phases of mass recovery. When sampling elevation change over a couple of years to decades, it is therefore much more likely to detect a thickening and therefore the population mean is biased to positive elevation change values.When assessing mean elevation change on a regional scale, usually one fixed glacier outline is chosen for masking the data. However, for surging glaciers the extent can undergo large fluctuations. I therefore further assess the mean elevation change for glaciers extent masks that are varying between the maximum and minimum values of a surge. Despite a constant climate, the mean elevation change turns out to be increasingly biased towards detecting a thickening signal the further upstream the glacier extent is taken. This implies that for minimizing this thickening bias from glacier surges in assessing regional elevation change, glacier outline masks from their most extensive extents should be used.Further modelling experiment showed that, the results are still valid when prescribing a variable climate forcing, but the surging effect is slightly subdued. &#160;

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