Strong changes in englacial temperatures despite insignificant changes in ice thickness at Dôme du Goûter glacier (Mont Blanc area)

Abstract. The response of very-high-elevation glaciated areas on Mont Blanc to climate change has been analysed using observations and numerical modelling over the last 2 decades. Unlike the changes at low elevations, we observe very low glacier thickness changes, of about −2.6 m on average since 1993. The slight changes in horizontal ice flow velocities and submergence velocities suggest a decrease of about 10 % in ice flux and surface mass balance. This is due to less snow accumulation and is consistent with the precipitation decrease observed in meteorological data. Conversely, measurements performed in deep boreholes since 1994 reveal strong changes in englacial temperature reaching a 1.5 ∘C increase at a depth of 50 m. We conclude that at such very high elevations, current changes in climate do not lead to visible changes in glacier thickness but cause invisible changes within the glacier in terms of englacial temperatures. Our analysis from numerical modelling shows that glacier near-surface temperature warming is enhanced by increasing melt frequency at high elevations although the impact on surface mass balance is low. This results in a non-linear response of englacial temperature to currently rising air temperatures. In addition, borehole temperature inversion including a new dataset confirms previous findings of similar air temperature changes at high and low elevations in the Alps.

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Strong changes in englacial temperatures despite insignificantchanges in ice thickness at Dôme du Goûter glacier (Mont-Blanc area)

10.5194/tc-2019-158 ◽

2019 ◽

Author(s):

Christian Vincent ◽

Adrien Gilbert ◽

Bruno Jourdain ◽

Luc Piard ◽

Patrick Ginot ◽

...

Keyword(s):

Numerical Modeling ◽

Mass Balance ◽

Snow Accumulation ◽

Surface Mass Balance ◽

Near Surface ◽

Surface Mass ◽

Precipitation Decrease ◽

High Elevations ◽

The Impact ◽

Very High

Abstract. The response of very high elevation glaciated areas on Mont Blanc to climate change has been analyzed using observations and numerical modeling. Unlike the changes at low elevations, we observe very low glacier thickness changes, of about −2.6 m on the average since 1993. The slight changes in horizontal ice flow velocities and submergence velocities suggest a decrease of about 10 % in ice flux and surface mass balance. This is due to snow accumulation changes and is consistent with the precipitation decrease observed in meteorological data. Conversely, measurements performed in deep boreholes since 1994 reveal strong changes in englacial temperature reaching 1.5 °C at a depth of 50 m. We conclude that at such very high elevations, current changes in climate do not lead to visible changes in glacier thickness but cause invisible changes within the glacier in terms of englacial temperatures. Our analysis from numerical modeling shows that glacier near-surface temperature warming is enhanced by increasing melt-frequency at high elevations although the impact on surface mass balance is low. This results in a non-linear response of englacial temperature to currently rising air temperatures. In addition, borehole temperature inversion including a new dataset confirms previous findings of similar air temperature changes at high and low elevations in the Alps.

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Surface mass balance, ice velocity and near-surface ice temperature on Qaanaaq Ice Cap, northwestern Greenland, from 2012 to 2016

Annals of Glaciology ◽

10.1017/aog.2017.7 ◽

2017 ◽

Vol 58 (75pt2) ◽

pp. 181-192 ◽

Cited By ~ 8

Author(s):

Shun Tsutaki ◽

Shin Sugiyama ◽

Daiki Sakakibara ◽

Teruo Aoki ◽

Masashi Niwano

Keyword(s):

Mass Balance ◽

Snow Accumulation ◽

Surface Mass Balance ◽

Outlet Glacier ◽

Near Surface ◽

Surface Mass ◽

Ice Cap ◽

In Situ Data ◽

Ice Velocity ◽

Surface Ice

ABSTRACT To better understand the processes controlling recent mass loss of peripheral glaciers and ice caps in northwestern Greenland, we measured surface mass balance (SMB), ice velocity and near-surface ice temperature on Qaanaaq Ice Cap in the summers of 2012–16. The measurements were performed along a survey route spanning the terminus of an outlet glacier to the upper reaches (243–968 m a.s.l.). The ice-cap-wide SMB ranged from −1.10 ± 0.29 to −0.13 ± 0.26 m w.e. a−1 for the years from 2012/13 to 2015/16. Mass balance showed substantially large fluctuations over the study period under the influence of summer temperature and snow accumulation. Ice velocity showed seasonal speedup only in the summer of 2012, suggesting an extraordinary amount of meltwater penetrated to the bed and enhanced basal ice motion. Ice temperature at a depth of 13 m was −8.0°C at 944 m a.s.l., which was 2.5°C warmer than that at 243 m a.s.l., suggesting that ice temperature in the upper reaches was elevated by refreezing and percolation of meltwater. Our study provided in situ data from a relatively unstudied region in Greenland, and demonstrated the importance of continued monitoring of these processes for longer timespans in the future.

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Reconstruction of historical surface mass balance, 1984–2017 from GreenTrACS multi-offset ground-penetrating radar

Journal of Glaciology ◽

10.1017/jog.2020.91 ◽

2020 ◽

pp. 1-10

Author(s):

Tate G. Meehan ◽

H. P. Marshall ◽

John H. Bradford ◽

Robert L. Hawley ◽

Thomas B. Overly ◽

...

Keyword(s):

Mass Balance ◽

Ground Penetrating Radar ◽

Greenland Ice Sheet ◽

Snow Accumulation ◽

Surface Mass Balance ◽

Snow Density ◽

Surface Mass ◽

Age Model ◽

Ground Penetrating ◽

Good Agreement

Abstract We present continuous estimates of snow and firn density, layer depth and accumulation from a multi-channel, multi-offset, ground-penetrating radar traverse. Our method uses the electromagnetic velocity, estimated from waveform travel-times measured at common-midpoints between sources and receivers. Previously, common-midpoint radar experiments on ice sheets have been limited to point observations. We completed radar velocity analysis in the upper ~2 m to estimate the surface and average snow density of the Greenland Ice Sheet. We parameterized the Herron and Langway (1980) firn density and age model using the radar-derived snow density, radar-derived surface mass balance (2015–2017) and reanalysis-derived temperature data. We applied structure-oriented filtering to the radar image along constant age horizons and increased the depth at which horizons could be reliably interpreted. We reconstructed the historical instantaneous surface mass balance, which we averaged into annual and multidecadal products along a 78 km traverse for the period 1984–2017. We found good agreement between our physically constrained parameterization and a firn core collected from the dry snow accumulation zone, and gained insights into the spatial correlation of surface snow density.

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Observationally constrained surface mass balance of Larsen C ice shelf, Antarctica

The Cryosphere ◽

10.5194/tc-11-2411-2017 ◽

2017 ◽

Vol 11 (6) ◽

pp. 2411-2426 ◽

Cited By ~ 7

Author(s):

Peter Kuipers Munneke ◽

Daniel McGrath ◽

Brooke Medley ◽

Adrian Luckman ◽

Suzanne Bevan ◽

...

Keyword(s):

Mass Balance ◽

Climate Model ◽

Regional Climate ◽

Snow Accumulation ◽

Airborne Radar ◽

Surface Mass Balance ◽

Spatial And Temporal Patterns ◽

Ice Shelf ◽

The West ◽

Surface Mass

Abstract. The surface mass balance (SMB) of the Larsen C ice shelf (LCIS), Antarctica, is poorly constrained due to a dearth of in situ observations. Combining several geophysical techniques, we reconstruct spatial and temporal patterns of SMB over the LCIS. Continuous time series of snow height (2.5–6 years) at five locations allow for multi-year estimates of seasonal and annual SMB over the LCIS. There is high interannual variability in SMB as well as spatial variability: in the north, SMB is 0.40 ± 0.06 to 0.41 ± 0.04 m w.e. year−1, while farther south, SMB is up to 0.50 ± 0.05 m w.e. year−1. This difference between north and south is corroborated by winter snow accumulation derived from an airborne radar survey from 2009, which showed an average snow thickness of 0.34 m w.e. north of 66° S, and 0.40 m w.e. south of 68° S. Analysis of ground-penetrating radar from several field campaigns allows for a longer-term perspective of spatial variations in SMB: a particularly strong and coherent reflection horizon below 25–44 m of water-equivalent ice and firn is observed in radargrams collected across the shelf. We propose that this horizon was formed synchronously across the ice shelf. Combining snow height observations, ground and airborne radar, and SMB output from a regional climate model yields a gridded estimate of SMB over the LCIS. It confirms that SMB increases from north to south, overprinted by a gradient of increasing SMB to the west, modulated in the west by föhn-induced sublimation. Previous observations show a strong decrease in firn air content toward the west, which we attribute to spatial patterns of melt, refreezing, and densification rather than SMB.

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The impact of a seasonally ice free Arctic Ocean on the climate and surface mass balance of Svalbard

The Cryosphere Discussions ◽

10.5194/tcd-5-1887-2011 ◽

2011 ◽

Vol 5 (4) ◽

pp. 1887-1920

Author(s):

J. J. Day ◽

J. L. Bamber ◽

P. J. Valdes ◽

J. Kohler

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Mass Balance ◽

21St Century ◽

Surface Mass Balance ◽

Surface Mass ◽

Sea Ice Decline ◽

Ice Edge ◽

Sea Ice Edge ◽

The Impact

Abstract. General circulation models (GCMs) predict a rapid decrease in Arctic sea ice extent in the 21st century. The decline of September sea ice is expected to continue until the Arctic Ocean is seasonally ice free, leading to a much perturbed Arctic climate with large changes in surface energy flux. Svalbard, located on the present day sea ice edge, contains many low lying ice caps and glaciers which are extremely sensitive to changes in climate. Records of past accumulation indicate that the surface mass balance (SMB) of Svalbard is also sensitive to changes in the position of the sea ice edge. To investigate the impact of 21st Century sea ice decline on the climate and surface mass balance of Svalbard a high resolution (25 km) regional climate model (RCM) was forced with a repeating cycle of sea surface temperatures (SSTs) and sea ice conditions for the periods 1961–1990 and 2061–2090. By prescribing 20th Century SSTs and 21st Century sea ice for one simulation, the impact of sea ice decline is isolated. This study shows that the coupled impact of sea ice decline and SST increase results in a decrease in SMB, whereas the impact of sea ice decline alone causes an increase in SMB of similar magnitude.

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The impact of a seasonally ice free Arctic Ocean on the temperature, precipitation and surface mass balance of Svalbard

The Cryosphere ◽

10.5194/tc-6-35-2012 ◽

2012 ◽

Vol 6 (1) ◽

pp. 35-50 ◽

Cited By ~ 21

Author(s):

J. J. Day ◽

J. L. Bamber ◽

P. J. Valdes ◽

J. Kohler

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Mass Balance ◽

21St Century ◽

Arctic Sea Ice ◽

Lower Atmosphere ◽

The Arctic ◽

Surface Mass Balance ◽

Surface Mass ◽

The Impact

Abstract. The observed decline in summer sea ice extent since the 1970s is predicted to continue until the Arctic Ocean is seasonally ice free during the 21st Century. This will lead to a much perturbed Arctic climate with large changes in ocean surface energy flux. Svalbard, located on the present day sea ice edge, contains many low lying ice caps and glaciers and is expected to experience rapid warming over the 21st Century. The total sea level rise if all the land ice on Svalbard were to melt completely is 0.02 m. The purpose of this study is to quantify the impact of climate change on Svalbard's surface mass balance (SMB) and to determine, in particular, what proportion of the projected changes in precipitation and SMB are a result of changes to the Arctic sea ice cover. To investigate this a regional climate model was forced with monthly mean climatologies of sea surface temperature (SST) and sea ice concentration for the periods 1961–1990 and 2061–2090 under two emission scenarios. In a novel forcing experiment, 20th Century SSTs and 21st Century sea ice were used to force one simulation to investigate the role of sea ice forcing. This experiment results in a 3.5 m water equivalent increase in Svalbard's SMB compared to the present day. This is because over 50 % of the projected increase in winter precipitation over Svalbard under the A1B emissions scenario is due to an increase in lower atmosphere moisture content associated with evaporation from the ice free ocean. These results indicate that increases in precipitation due to sea ice decline may act to moderate mass loss from Svalbard's glaciers due to future Arctic warming.

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Temporal and spatial variability of surface mass balance at Dome Fuji, East Antarctica, by the stake method from 1995 to 2006

Journal of Glaciology ◽

10.3189/002214308784409062 ◽

2008 ◽

Vol 54 (184) ◽

pp. 107-116 ◽

Cited By ~ 60

Author(s):

Takao Kameda ◽

Hideaki Motoyama ◽

Shuji Fujita ◽

Shuhei Takahashi

Keyword(s):

Mass Balance ◽

Ice Core ◽

Snow Accumulation ◽

East Antarctica ◽

Surface Mass Balance ◽

Surface Mass ◽

Frequency Distributions ◽

Temporal And Spatial Variability ◽

The Antarctic ◽

Height Data

AbstractThe surface mass balance (SMB) at Dome Fuji, East Antarctica, was estimated using 36 bamboo stakes (grid of 6 × 6, placed at 20 m intervals) from 1995 to 2006. The heights of the stake tops from the snow surface were measured at 0.5 cm resolution twice monthly in 1995, 1996, 1997 and 2003, and once a year for the rest of the study period. To account for snow settling, the average snow density at the stake base during the measurements was used for converting the stake-height data to SMB. The annual SMB from 1995 to 2006 at Dome Fuji was 27.3 ± 1.5 kg m−2 a−1. This result agrees well with the annual SMB from AD 1260 to 1993 (26.4 kg m−2 a−1) estimated from volcanic signals in the Dome Fuji ice core. Over the period 1995–2006, there were 37 (8.6% of the measurements) negative or zero annual SMB results. Variation in the multi-year averages of annual SMB decreased with the square root of the number of observation years, and 10 years of observations of a single stake allowed the estimation of annual SMB at ±10% accuracy. The frequency distributions of annual and monthly SMB were examined. The findings clarify the complex behavior of the annual and monthly SMB at Dome Fuji, which will be common phenomena in areas of low snow accumulation of the interior of the Antarctic ice sheet.

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An Evaluation of Surface Climatology in State-of-the-Art Reanalyses over the Antarctic Ice Sheet

Journal of Climate ◽

10.1175/jcli-d-19-0030.1 ◽

2019 ◽

Vol 32 (20) ◽

pp. 6899-6915 ◽

Cited By ~ 6

Author(s):

A. Gossart ◽

S. Helsen ◽

J. T. M. Lenaerts ◽

S. Vanden Broucke ◽

N. P. M. van Lipzig ◽

...

Keyword(s):

Relative Humidity ◽

Surface Temperature ◽

Mass Balance ◽

Ice Sheet ◽

Surface Mass Balance ◽

Antarctic Ice Sheet ◽

Near Surface ◽

Surface Mass ◽

Atmospheric Rivers ◽

The Antarctic

Abstract In this study, we evaluate output of near-surface atmospheric variables over the Antarctic Ice Sheet from four reanalyses: the new European Centre for Medium-Range Weather Forecasts ERA-5 and its predecessor ERA-Interim, the Climate Forecast System Reanalysis (CFSR), and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). The near-surface temperature, wind speed, and relative humidity are compared with datasets of in situ observations, together with an assessment of the simulated surface mass balance (approximated by precipitation minus evaporation). No reanalysis clearly stands out as the best performing for all areas, seasons, and variables, and each of the reanalyses displays different biases. CFSR strongly overestimates the relative humidity during all seasons whereas ERA-5 and MERRA-2 (and, to a lesser extent, ERA-Interim) strongly underestimate relative humidity during winter. ERA-5 captures the seasonal cycle of near-surface temperature best and shows the smallest bias relative to the observations. The other reanalyses show a general temperature underestimation during the winter months in the Antarctic interior and overestimation in the coastal areas. All reanalyses underestimate the mean near-surface winds in the interior (except MERRA-2) and along the coast during the entire year. The winds at the Antarctic Peninsula are overestimated by all reanalyses except MERRA-2. All models are able to capture snowfall patterns related to atmospheric rivers, with varying accuracy. Accumulation is best represented by ERA-5, although it underestimates observed surface mass balance and there is some variability in the accumulation over the different elevation classes, for all reanalyses.

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Surface mass balance of the Greenland ice sheet from climate-analysis data and accumulation/runoff models

Annals of Glaciology ◽

10.3189/172756402781816744 ◽

2002 ◽

Vol 35 ◽

pp. 67-72 ◽

Cited By ~ 31

Author(s):

Edward Hanna ◽

Philippe Huybrechts ◽

Thomas L. Mote

Keyword(s):

Mass Balance ◽

Satellite Data ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Snow Accumulation ◽

Surface Elevation ◽

Great Promise ◽

Surface Mass Balance ◽

Ice Dynamics ◽

Surface Mass

AbstractWe used surface climate fields from high-resolution (~0.5660.56˚) European Centre for Medium-RangeWeather Forecasts (ECMWF) operational analyses (1992–98), together with meteorological and glaciological models of snow accumulation and surface meltwater runoff/retention, to produce novel maps of Greenland ice sheet (GIS) net accumulation, net runoff and surface mass balance (SMB). We compared our runoff maps with similar-scaled runoff (melt minus refreezing) maps based on passive-microwave satellite data. Our gross spatial/temporal patterns of runoff compared well with those from the satellite data, although amounts of modelled runoff are likely too low. Mean accumulation was 0.287 (0.307)ma–1, and mean runoff was 0.128 (0.151)ma–1, averaged across the W. Abdalati (T. L. Mote) GIS mask. Corresponding mean SMB was 0.159 (0.156)ma–1, with considerable interannual variability (standard deviation ~0.11ma–1) primarily due to variations in runoff. Considering best estimates of current iceberg calving, overall the GIS is probably currently losing mass. Our study shows great promise for meaningfully modelling SMB based on forthcoming ``second-generation’’ ECMWF re-analysis (ERA-40) data, and comparing the results with ongoing laser/radarmeasurements of surface elevation. This should help elucidate to what extent surface elevation changes are caused by short-term SMB variations or other factors (e.g. ice dynamics).

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Impact of coastal East Antarctic ice rises on surface mass balance: insights from observations and modelling

10.5194/egusphere-egu2020-20370 ◽

2020 ◽

Author(s):

Thore Kausch ◽

Stef Lhermitte ◽

Jan T.M. Lenaerts ◽

Nander Wever ◽

Mana Inoue ◽

...

Keyword(s):

Mass Balance ◽

Wind Erosion ◽

Ice Core ◽

Ice Cores ◽

Snow Accumulation ◽

Windward Side ◽

Leeward Side ◽

Surface Mass Balance ◽

Surface Mass ◽

Local Erosion

About 20% of all snow accumulation in Antarctica occurs on the ice shelfs and ice rises, locations within the ice shelf where the ice is locally grounded on topography. These ice rises largely control the spatial surface mass balance (SMB) distribution by inducing snowfall variability due to orographic uplift and by inducing wind erosion due altering the wind conditions. Moreover these ice rises buttress the ice flow and represent an ideal drilling locations for ice cores.In this study we assess the connection between snowfall variability and wind erosion to provide a better understanding of how ice rises impact SMB variability, how well this is captured in the regional atmospheric climate model RACMO, and the implications of this SMB variability for ice rises as an ice core drilling side. By combining ground penetrating radar profiles from two ice rises in Dronning Maud Land with ice core dating we reconstruct spatial and temporal SMB variations across both ice rises from 1982 to 2017. Subsequently, the observed SMB is compared with output from RACMO, SnowModel to quantify the contribution of the different processes that control the spatial SMB variability across the ice rises. Finally, the observed SMB is compared with Sentinel-1 backscatter data to extrapolate spatial SMB trends over larger areas.Our results show snowfall-driven differences of up to ~ 0.24 m w.e./yr between the windward and the leeward side of both ice rises as well as a local erosion driven minimum at the peak of the ice rises. RACMO captures the snowfall-driven differences, but overestimates their magnitude, whereas the erosion on the peak can be reproduced by SnowModel with RACMO forcing. Observed temporal variability of the average SMBs calculated for 4 time intervals in the 1982-2017 range are low at the peak of the easternmost ice rise (~ 0.03 m w.e./yr), while being three times higher (~ 0.1 m w.e./yr) on the windward side of the ice rise. This implicates that at the peak of the ice rise, higher snowfall, driven by regional processes, such as orographic uplift, is balanced out by local erosion. &#160;Comparison of the observed SMB gradients with Sentinel-1 data finally shows the potential of SAR satellite observations to represent spatial variability in SMB across ice shelves and ice rises.

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