Negative Mass Budget Research Articles

Quantification of glacier mass budgets in the Karakoram region of Upper Indus Basin during the early twenty-first century

Water supply contributed by glacier and snow melt is of particular significance and play a key role for social stability in the Karakoram region of Upper Indus Basin (UIBKK). Based on the SRTM DEM, TerraSAR-X/TanDEM-X images and ZY3-02 stereo images, the spatiotemporal pattern of glacier mass budgets in the UIBKK have been estimated for the early 21st century (2000–2019) period in this study. A comparison of the total area in 2000 with that in 2019 shows that glacier area remained stable in the early 21st century, with a slight expansion of 56.3 km2 (0.4%). Glaciers in the UIBKK experienced a balanced or slight negative mass budget of −0.08 ± 0.07 m w.e. a−1 in the early 21st century. The spatial variability of mass budget in the UIBKK showed that glacier mass budgets shifted from negative to positive from West to East, respectively, along longitude. Glacier mass loss decelerated from −0.12 ± 0.16 m w.e. a−1 in 2000–2013 to −0.03 ± 0.21 m w.e. a−1 in 2013–2019. No significant differences were observed in thinning rates on debris-covered glaciers (≥19% area covered by debris) and clean-ice glaciers (<19% area covered by debris) in the early 21st century (−0.06 m a−1 vs −0.04 m a−1). The overall homogeneous mass budgets for surge and non-surge glaciers indicated that glacier surges seem not have a notable impact on glacier-wide mass budget over short time scales. The spatiotemporal variability of glacier mass budgets in the UIBKK are consistent with the tendencies of winter precipitation and summer temperature. Climate warming may play more important role in glacier changes in the UIBKK.

Evolution of Surface Characteristics of Three Debris-Covered Glaciers in the Patagonian Andes From 1958 to 2020

A number of glaciological observations on debris-covered glaciers around the globe have shown a delayed length and mass adjustment in relation to climate variability, a behavior normally attributed to the ice insulation effect of thick debris layers. Dynamic interactions between debris cover, geometry and surface topography of debris-covered glaciers can nevertheless govern glacier velocities and mass changes over time, with many glaciers exhibiting high thinning rates in spite of thick debris cover. Such interactions are progressively being incorporated into glacier evolution research. In this paper we reconstruct changes in debris-covered area, surface velocities and surface features of three glaciers in the Patagonian Andes over the 1958–2020 period, based on satellite and aerial imagery and Digital Elevation Models. Our results show that debris cover has increased from 40 ± 0.6 to 50 ± 6.7% of the total glacier area since 1958, whilst glacier slope has slightly decreased. The gently sloping tongues have allowed surface flow velocities to remain relatively low (&amp;lt;60 m a−1) for the last two decades, preventing evacuation of surface debris, and contributing to the formation and rise of the ice cliff zone upper boundary. In addition, mapping of end of summer snowline altitudes for the last two decades suggests an increase in the Equilibrium Line Altitudes, which promotes earlier melt out of englacial debris and further increases debris-covered ice area. The strongly negative mass budget of the three investigated glaciers throughout the study period, together with the increases in debris cover extent and ice cliff zones up-glacier, and the low velocities, shows a strong linkage between debris cover, mass balance evolution, surface velocities and topography. Interestingly, the presence of thicker debris layers on the lowermost portions of the glaciers has not lowered thinning rates in these ice areas, indicating that the mass budget is mainly driven by climate variability and calving processes, to which the influence of enhanced thinning at ice cliff location can be added.

Six Decades (1958–2018) of Geodetic Glacier Mass Balance in Monte San Lorenzo, Patagonian Andes

A full understanding of glacier changes in the Patagonian Andes over decadal to century time-scales is presently limited by a lack of detailed and appropriate long-term observations. Here, we present geodetic mass and area changes of three valley glaciers from Monte San Lorenzo derived from stereo aerial photos, the Shuttle Radar Topography Mission (SRTM) and satellite imagery (SPOT5 and Pleiades) spanning four periods from 1958 to 2018. Our results indicate that net mass balance was negative throughout the six decades, with a mean mass loss of -1.35 ±0.08 m w.e. a-1 and a total glacier area loss of 14.2 ±0.7 km2 (23 ±1 % or 0.40 ±0.02 % a-1). The period 1981-2000 had the most negative mass budget, with an area-averaged mass loss of 1.67 ±0.11 m w.e. a-1 and a maximum loss of -2.23 ±0.07 m w.e.a−1 at San Lorenzo Sur glacier. Over the periods of 2000-2012 and 2012-2018, the mass budget of these three glaciers remained virtually unchanged at -1.37 ±0.06 m w.e. a-1 and –1.36 ±0.17 m w.e. a-1, respectively. To place these results into a broader geographical context, the mass balance of a further 15 glaciers from around the Monte San Lorenzo massif was determined from 2000 onwards. This wider analysis reveals a period of reduced mass loss of -0.13 ±0.21 m w.e.a−1 from 2012 to 2018 after a period of enhanced mass loss of -0.31 ±0.16 m w.e.a−1 between 2000 and 2012. We find that increasing air temperatures coupled with diminishing precipitation across the region explains the observed patterns and are the main drivers of the negative mass budget. Furthermore, increased calving and melting into recently formed proglacial lakes has further enhanced mass loss at some lake-terminating glaciers.

Quantifying mass balance of East-Karakoram glaciers using geodetic technique

The Karakoram Range comprises the heavily glaciated mountains outside the Polar regions. A comprehensive assessment of glaciers variation in this region is crucial to ascertain constant water supply under different scenarios of futuristic climate change. Lack of accessibility to the Karakoram region has limited the use of conventional methods in monitoring variations in thickness and mass of glaciers, alternatively promoting the use of remote sensing based methods. The present study quantifies changes in thickness and mass budget of 24 glaciers in East-Karakoram region using geodetic technique. The Digital Elevation Model (DEM) adjustments and comparisons were made between Shuttle Radar Topography Mission (SRTM) C-band DEM, year 2000 and recent DEMs of the years 2009 and 2014, which were generated using stereo pairs of Panchromatic Remote Sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS) and Cartosat-1 respectively. The vertical accuracy of recent DEMs was assessed using ICESat-1 laser points. Other biases such as elevation dependent, radar penetration, terrain curvature and seasonality were also rectified before computing the glacier mass balance. Geodetic esimates indicate an overall marginal thinning (−0.09 ± 0.16 m/yr) and negative mass budget (−0.08 ± 0.13 m.w.e./yr) during the years 2000–2014. Interestingly, one glacier showed surge-type activity (advancing and thickening terminus) during 2000-2014, with highest (0.59) Accumulation Area Ratio (AAR) amongst studied glaciers. Time series analysis of climate data (temperature and precipitation) recorded at field observatories depict overall warming in the East-Karakoram region. The higher rate of mass loss during 2009–2014 (−0.07 ± 0.13 m.w.e./yr) compared to 2000–2009 (−0.05 ± 0.12 m.w.e./yr) was found in agreement with the rise in temperature and decline in precipitation over the region during different years. The results thus indicate an insignificant mass loss in East-Karakoram glaciers and thus exhibit a nearly balanced state since the year 2000 in contrast to glacier mass loss in other Himalayan ranges.

Glacier variations at Aru Co in western Tibet from 1971 to 2016 derived from remote-sensing data

ABSTRACTTwin glaciers collapsed in 2016 near Aru Co, western Tibet and caused extreme loss to human beings. In this study, we attempted to track the dynamics of glaciers in the region, for example the glacier area and mass changes in Aru Co for the period 1971–2016, which were determined using topographic maps and Landsat images and ASTER-derived DEMs (2011–16), the Shuttle Radar Terrain Mission DEM (2000) and topographic maps (1971). Our results showed that the glacier area of Aru Co decreased by −0.4 ± 4.1% during 1971–2016. The geodetic mass-balance results showed that the glaciers in Aru Co lost mass at a rate of −0.15 ± 0.30 m w.e. a−1 during 1971–99, while they gained mass at a rate of 0.33 ± 0.61 m w.e. a−1 for the period 1999–2016. The twin glaciers experienced a larger negative mass budget than the others in the region before 1999. This process produced large amounts of meltwater, followed by a sustained increase in the meltwater on the pressure melting point, possibly in response to a period of positive mass balance (1999–2016) and then, transferred to the glacier bed until the glaciers collapsed.

Recent mass balance of the Purogangri Ice Cap, central Tibetan Plateau, by means of differential X-band SAR interferometry

Abstract. Due to their remoteness, altitude and harsh climatic conditions, little is known about the glaciological parameters of ice caps on the Tibetan Plateau. This study presents a geodetic mass balance estimate of the Purogangri Ice Cap, Tibet's largest ice field between 2000 and 2012. We utilized data from the actual TerraSAR-X mission and its add-on for digital elevation measurements and compared it with elevation data from the Shuttle Radar Topography Mission. The employed data sets are ideal for this approach as both data sets were acquired at X-band at nearly the same time of the year and are available at a fine grid spacing. In order to derive surface elevation changes we employed two different methods. The first method is based on differential synthetic radar interferometry while the second method uses common DEM differencing. Both approaches revealed a slightly negative mass budget of −44 ± 15 and −38 ± 23 mm w.eq. a−1 (millimeter water equivalent) respectively. A slightly negative trend of −0.15 ± 0.01 km2 a−1 in glacier extent was found for the same time period employing a time series of Landsat data. Overall, our results show an almost balanced mass budget for the studied time period. Additionally, we detected one continuously advancing glacier tongue in the eastern part of the ice cap.

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

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.

Programme for Monitoring of the Greenland Ice Sheet (PROMICE): first temperature and ablation records

The Greenland ice sheet is reacting to climate change. Yet, mass-budget estimates differ considerably, partly due to climatic variability and partly to uncertainties in the techniques of assessing mass change (IPCC 2007). Nevertheless, all recent estimates agree that the ice sheet is losing mass (e.g. 286 Gt/yr; Velicogna 2009) at an accelerating rate (Rignot et al. 2011). On top of this, the area with a negative mass budget is expanding rapidly (Khan et al. 2010). The mass loss is attributed equally to increases in both iceberg production and melting of the ice sheet (Van den Broeke et al. 2009). The increasing mass loss in recent years has caught public attention and given rise to concern worldwide due to its potential impact on sea level. In the light of this, the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) was initiated in 2007 (Ahlstrøm &amp; PROMICE project team 2008), lead by the Geological Survey of Denmark and Greenland (GEUS). PROMICE undertakes surface mass-budget measurements using automatic weather stations, quantifies the mass loss by iceberg calving using remotely sensed data from satellites and airborne surveys and tracks changes in the extent of glaciers. In this paper, we focus on weather station measurements, which are crucial in calculating the energy exchange between the atmosphere and the ice sheet, and in validating model calculations of the surface mass budget. In particular, we present the observed temperatures and investigate how their high 2010 values affected ablation in southern Greenland

Über glaziale Erosion und Übertiefung

Abstract. Glacial erosion and overdeepening is - as can be shown by the longitudinal profile of every valley formed by glaciers - not a process active on the whole longitudinal extension of the glacier in the same way, but is characterized by marked discontinuities. The reasons have been discussed for nearly a century, but the problem remained unsolved until now. It can - as H. Louis (1952) has demonstrated - be solved only when the motion mechanism of the glaciers is known. The present paper demonstrates on the base of observations in the area of the Iller glacier of the last glaciation that Pleniglacial glaciers with positive mass budget (advancing glaciers) have moved in another way than present-day glaciers with their - mostly - negative mass budget. Furthermore it is demonstrated that this particular motion mechanism can actually be observed at advancing outlet glaciers of the Vatnajökull in Iceland. It is characterized by a summation of numerous push movements of flat ice-shields on shear-planes over stagnant-ice of preceding advances, all of them of relatively short duration and range. They originated in precipitation-caused mass surpluses in the feeding area. This motion mechanism implies that an impact on the underground is possible only where (and when) the glacier advances beyond its stagnant-ice basement, i. e. immediately behind the front of the advancing glacier. A larger amount of glacial erosion can be expected only when the glacier after the advance remained in the maximum position reached for a longer time and, additionally, (snow)meltwater under hydrostatic pressure could affect the underground. Further observations on meltwater movement within the glacier are presented from Iceland, on meltwater impact on the underground (mainly) from the German Alpine Foreland. To sum up, the discontinuities of glacial erosion and overdeepening can be explained by the motion mechanism of advancing glaciers described, the protective effect of the overridden stagnant-ice basement of preceding advances, and the characteristic movement of (snow)meltwater in, below and along the glacier. Because the erosion processes described take place (mainly) immediately behind the front of the advancing glacier, they are a phenomenon restricted in space as well as in time, but therefore must be of extraordinary intensity.

Glacioclimatological features in the Tanggula mountains, China

Air temperature and precipitation data have been obtained from the Geladandong region at the headwaters of the Yangtze River. At the equilibrium line altitude of the glaciers, mean annual and summer air temperatures are –10 to –12.0°C and 1.0 to –1.0°C, respectively. Accumulation on the glaciers on the south side of the Tanggula mountains depends mainly on water vapour transported from the south and southeast. The moisture source for the glaciers on the north side is from the east. Precipitation increases with altitude in the glaciated areas. An estimated annual accumulation in the firn areas is about 400 to 600 mm of water equivalent. The Geladandon region has a cold, dry climate and the glaciers in the region can be classified as continental. The present climatic conditions result in a negative mass budget for most glaciers.

Glacioclimatological features in the Tanggula mountains, China

Air temperature and precipitation data have been obtained from the Geladandong region at the headwaters of the Yangtze River. At the equilibrium line altitude of the glaciers, mean annual and summer air temperatures are –10 to –12.0°C and 1.0 to –1.0°C, respectively. Accumulation on the glaciers on the south side of the Tanggula mountains depends mainly on water vapour transported from the south and southeast. The moisture source for the glaciers on the north side is from the east. Precipitation increases with altitude in the glaciated areas. An estimated annual accumulation in the firn areas is about 400 to 600 mm of water equivalent. The Geladandon region has a cold, dry climate and the glaciers in the region can be classified as continental. The present climatic conditions result in a negative mass budget for most glaciers.

An analysis of surface energy during the ablation season on Lemon Creek Glacier, Alaska

The purpose of the present study has been to perform an empirical investigation of the energy transfer at an isothermal, melting snow surface and its relationship to observed meteorological parameters, using more refined instrumentation and methods of observation than were available in earlier, similar investigations by H. U. Sverdrup and C. C. Wallen.The thickness of the surface layer of snow through which absorption of solar radiation occurs is determined from measurements of intensities of visible radiation within the snow. Albedo values for the snow are computed from measurements of incoming and reflected solar radiation over the snow surface. The snow albedo is found to vary with solar altitude and cloudiness as well as with changes in physical characteristics of the snow. When long‐wave radiation is considered along with solar radiation, it is found that during the ablation season, the diurnal net transfer of radiant energy to the melting snowpack is often greater when skies are overcast than when skies are clear. A comparison is made between the radiative energy transfer at the surface of a model glacier in the Juneau Ice Field, and a model glacier in the Alps.It is shown that energy transfer to the snow by rain falling on an isothermal melting snowpack is an insignificant part of the total energy transfer.From measured and calculated values of net energy transfer at the snow surface, energy transfer by radiation, and energy transfer by rain, values of energy transfer by turbulence are determined for a series of selected observation periods. These values are used to calculate exchange coefficients. It is shown that by making a slight modification in the functional expression for heat transfer by turbulence from that used by Sverdrup and Wallén, it is possible to obtain a nearly invariant relationship between the heat transfer by turbulence, windspeed, and the vertical temperature distribution above the surface when an inversion is present.It is found that turbulent transfer of heat is the most important factor in causing ablation on the Lemon Creek Glacier. This turbulent transfer of energy becomes very large during summer storm periods. As a result, the number of warm storms passing over the glacier in a single ablation season can largely determine whether the glacier will end the season with a positive or negative mass budget.