Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau

Abstract. On the Antarctic Plateau, snow specific surface area (SSA) close to the surface shows complex variations at daily to seasonal scales which affect the surface albedo and in turn the surface energy budget of the ice sheet. While snow metamorphism, precipitation and strong wind events are known to drive SSA variations, usually in opposite ways, their relative contributions remain unclear. Here, a comprehensive set of SSA observations at Dome C is analysed with respect to meteorological conditions to assess the respective roles of these factors. The results show an average two-to-three-fold SSA decrease from October to February in the topmost 10 cm, in response to the increase of air temperature and absorption of solar radiation in the snowpack during spring and summer. Surface SSA is also characterised by significant daily to weekly variations, due to the deposition of small crystals with SSA up to 100 m2 kg−1 onto the surface during snowfall and blowing snow events. To complement these field observations, the detailed snowpack model Crocus is used to simulate SSA, with the intent to further investigate the previously found correlation between inter-annual variability of summer SSA decrease and summer precipitation amount. To this end, Crocus parameterizations have been adapted to Dome C conditions, and the model was forced by ERA-Interim reanalysis. It successfully matches the observations at daily to seasonal time scales, except for few cases when snowfalls are not captured by the reanalysis. On the contrary, the inter-annual variability of summer SSA decrease is poorly simulated when compared to 14 years of microwave satellite data sensititve to the near surface SSA. A simulation with disabled summer precipitation confirms the weak influence in the model of the precipitation on metamorphism, with only 6 % enhancement. However we found that disabling strong wind events in the model is sufficient to reconciliate the simulations with the observations. This suggests that Crocus reproduces well the contributions of metamorphism and precipitation on surface SSA, but that snow compaction by the wind might be overestimated in the model.

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Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau

The Cryosphere ◽

10.5194/tc-9-2383-2015 ◽

2015 ◽

Vol 9 (6) ◽

pp. 2383-2398 ◽

Cited By ~ 23

Author(s):

Q. Libois ◽

G. Picard ◽

L. Arnaud ◽

M. Dumont ◽

M. Lafaysse ◽

...

Keyword(s):

Specific Surface ◽

Interannual Variability ◽

Surface Area ◽

Specific Surface Area ◽

Summer Precipitation ◽

Strong Wind ◽

Near Surface ◽

Antarctic Plateau ◽

Wind Events ◽

The Antarctic

Abstract. On the Antarctic Plateau, snow specific surface area (SSA) close to the surface shows complex variations at daily to seasonal scales which affect the surface albedo and in turn the surface energy budget of the ice sheet. While snow metamorphism, precipitation and strong wind events are known to drive SSA variations, usually in opposite ways, their relative contributions remain unclear. Here, a comprehensive set of SSA observations at Dome C is analysed with respect to meteorological conditions to assess the respective roles of these factors. The results show an average 2-to-3-fold SSA decrease from October to February in the topmost 10 cm in response to the increase of air temperature and absorption of solar radiation in the snowpack during spring and summer. Surface SSA is also characterized by significant daily to weekly variations due to the deposition of small crystals with SSA up to 100 m2 kg−1 onto the surface during snowfall and blowing snow events. To complement these field observations, the detailed snowpack model Crocus is used to simulate SSA, with the intent to further investigate the previously found correlation between interannual variability of summer SSA decrease and summer precipitation amount. To this end, some Crocus parameterizations have been adapted to Dome C conditions, and the model was forced by ERA-Interim reanalysis. It successfully matches the observations at daily to seasonal timescales, except for the few cases when snowfalls are not captured by the reanalysis. On the contrary, the interannual variability of summer SSA decrease is poorly simulated when compared to 14 years of microwave satellite data sensitive to the near-surface SSA. A simulation with disabled summer precipitation confirms the weak influence in the model of the precipitation on metamorphism, with only 6 % enhancement. However, we found that disabling strong wind events in the model is sufficient to reconciliate the simulations with the observations. This suggests that Crocus reproduces well the contributions of metamorphism and precipitation on surface SSA, but snow compaction by the wind might be overestimated in the model.

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Vertical profiles of the specific surface area of the snow at Dome C, Antarctica

The Cryosphere Discussions ◽

10.5194/tcd-4-1647-2010 ◽

2010 ◽

Vol 4 (3) ◽

pp. 1647-1708 ◽

Cited By ~ 7

Author(s):

J.-C. Gallet ◽

F. Domine ◽

L. Arnaud ◽

G. Picard ◽

J. Savarino

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Austral Summer ◽

Radiative Transfer Model ◽

Integrating Sphere ◽

Transfer Model ◽

Vertical Profiles ◽

Antarctic Plateau ◽

The Antarctic

Abstract. The specific surface area (SSA) of snow determines in Part the albedo of snow surfaces and the capacity of the snow to adsorb chemical species and catalyze reactions. Despite these crucial roles, almost no value of snow SSA are available for the largest permanent snow expanse on Earth, the Antarctic. We have measured the first vertical profiles of snow SSA near Dome C (DC: 75°06´ S, 123°20´ E, 3233 m a.s.l.) on the Antarctic plateau, and at seven sites during the logistical traverse between Dome C and the French coastal base Dumont D'Urville (DDU: 66°40´ S, 140°01´ E) during the Austral summer 2008–2009. We used the DUFISSS system, which measures the IR reflectance of snow at 1310 nm with an integrating sphere. At DC, the mean SSA of the snow in the top 1 cm is 38 m2 kg−1, decreasing monotonically to 14 m2 kg−1 at a depth of 15 cm. Along the traverse, the snow SSA profile is similar to that at DC in the first 600 km from DC. Closer to DDU, the SSA of the top 5 cm is 23 m2 kg−1, decreasing to 19 m2 kg−1 at 50 cm depth. This is attributed to wind, which causes a rapid decrease of surface snow SSA, but forms hard windpacks whose SSA decrease more slowly with time. Since light-absorbing impurities are not concentrated enough to affect albedo, the vertical profiles of SSA and density were used to calculate the spectral albedo of the snow for several realistic illumination conditions, using the DISORT radiative transfer model. A preliminary comparison with MODIS data is presented for use in energy balance calculations and for comparison with other satellite retrievals. These calculated albedos are compared to the few existing measurements on the Antarctic plateau. The interest of postulating a submillimetric, high-SSA layer at the snow surface to explain measured albedos is discussed.

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The growth of sublimation crystals and surface hoar on the Antarctic plateau

The Cryosphere Discussions ◽

10.5194/tcd-7-5971-2013 ◽

2013 ◽

Vol 7 (6) ◽

pp. 5971-5999

Author(s):

J.-C. Gallet ◽

F. Domine ◽

J. Savarino ◽

M. Dumont ◽

E. Brun

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Temperature Drop ◽

Antarctic Plateau ◽

Snow Crystal ◽

Time Variations ◽

Frost Flowers ◽

Snow Model ◽

The Antarctic

Abstract. On the Antarctic plateau, the budget of water vapor and energy is in part determined by precipitation, but these are so low that the dynamic of snow crystal growth and sublimation at the surface can be important factors. At Dome C (75° S, 123° E), we have frequently observed the growth of crystals on the snow surface under calm sunny weather. Here, we present the time variations of specific surface area and density of these crystals. Using the detailed snow model Crocus, we conclude that these crystals were very likely due to the nighttime formation of surface hoar crystals and to the daytime formation of sublimation crystals. These latter crystals form by processes similar to those involved in the formation of frost flowers on young sea ice. The formation of these crystals impact the albedo, mass and energy budget of the Antarctic plateau. In particular, the specific surface area variations of the surface layer can induce an instantaneous forcing of up to −10 W m−2 at noon, resulting in a surface temperature drop of 0.45 K.

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Strong-wind events and their impact on the near-surface climate at Kohnen Station on the Antarctic Plateau

Antarctic Science ◽

10.1017/s095410200700065x ◽

2007 ◽

Vol 19 (4) ◽

pp. 507-519 ◽

Cited By ~ 16

Author(s):

Dirk van As ◽

Michiel R. van den Broeke ◽

Michiel M. Helsen

Keyword(s):

Vertical Mixing ◽

Longwave Radiation ◽

Weddell Sea ◽

Shortwave Radiation ◽

Strong Wind ◽

The South ◽

Near Surface ◽

Antarctic Plateau ◽

Wind Events ◽

The Antarctic

AbstractStrong-wind events occur 10–20 times per year at Kohnen Station, East Antarctica (75°00′S, 0°04′E, 2892 m above sea level), and are often caused by warm-core cyclones in the north-eastern Weddell Sea. An uncommon event occurred in January 2002, when blocking both in the south Atlantic Ocean and in the south Tasman Sea caused a split-up of the circumpolar vortex, and large amounts of heat and moisture were transported onto the Antarctic Plateau. During strong-wind events over the plateau the near-surface temperature can increase by tens of degrees, which is partly caused by the advection of heat, but for an important part by the destruction of the stable temperature-deficit layer by enhanced vertical mixing. The temperature rise is larger during the winter/night than during the summer/day, due to a better-developed temperature deficit. Snowdrift during the January 2002 event linearly increased surface roughness for momentum with friction velocity, for values over about 0.18 m s-1. The cloud cover during the event reduced down-welling solar radiation by 32%, and increased the albedo from about 0.86 to 0.92. Changes in longwave radiation largely cancelled the daytime changes in shortwave radiation, thus net radiation was most affected at night.

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Impact of radiation penetration on Antarctic surface melt and subsurface snow temperatures in RACMO2.3p3

10.5194/tc-2021-298 ◽

2021 ◽

Author(s):

Christiaan Timo van Dalum ◽

Willem Jan van de Berg ◽

Michiel Roland van den Broeke

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Ice Sheet ◽

Antarctic Ice Sheet ◽

Surface Mass ◽

Surface Melt ◽

The Antarctic ◽

The Impact ◽

Snow Temperature

Abstract. This study investigates the sensitivity of modeled surface melt and subsurface heating on the Antarctic ice sheet to a new spectral snow albedo and radiative transfer scheme in the Regional Atmospheric Climate Model (RACMO2), version 2.3p3 (Rp3). We tune Rp3 to observations by performing several sensitivity experiments and assess the impact on temperature and melt by changing one parameter at a time. When fully tuned, Rp3 compares well with in situ and remote sensing observations of surface mass and energy balance, melt, temperature, albedo and snow grain specific surface area. Furthermore, the introduction of subsurface heating in Rp3 significantly improves the snow temperature profile. Near surface snow temperature is especially sensitive to the prescribed fresh snow specific surface area and fresh dry snow metamorphism. These processes, together with the refreezing grain size and subsurface heating, are important for melt around the margins of the Antarctic ice sheet. Moreover, small changes in the albedo and the aforementioned processes can lead to an order of magnitude overestimation of melt, locally leading to runoff and a reduced surface mass balance.

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Vertical profile of the specific surface area and density of the snow at Dome C and on a transect to Dumont D'Urville, Antarctica – albedo calculations and comparison to remote sensing products

The Cryosphere ◽

10.5194/tc-5-631-2011 ◽

2011 ◽

Vol 5 (3) ◽

pp. 631-649 ◽

Cited By ~ 41

Author(s):

J.-C. Gallet ◽

F. Domine ◽

L. Arnaud ◽

G. Picard ◽

J. Savarino

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Extensive Study ◽

Radiative Transfer Model ◽

Integrating Sphere ◽

Transfer Model ◽

Vertical Profiles ◽

Modis Data ◽

The Antarctic

Abstract. The specific surface area (SSA) of snow determines in part the albedo of snow surfaces and the capacity of the snow to adsorb chemical species and catalyze reactions. Despite these crucial roles, almost no value of snow SSA are available for the largest permanent snow expanse on Earth, the Antarctic. We report the first extensive study of vertical profiles of snow SSA near Dome C (DC: 75°06' S, 123°20' E, 3233 m a.s.l.) on the Antarctic plateau, and at seven sites during the logistical traverse between Dome C and the French coastal base Dumont D'Urville (DDU: 66°40' S, 140°01' E) during the Austral summer 2008–2009. We used the DUFISSS system, which measures the IR reflectance of snow at 1310 nm with an integrating sphere. At DC, the mean SSA of the snow in the top 1 cm is 38 m2 kg−1, decreasing monotonically to 14 m2 kg−1 at a depth of 50 cm. Along the traverse, the snow SSA profile is similar to that at DC in the first 600 km from DC. Closer to DDU, the SSA of the top 5 cm is 23 m2 kg−1, decreasing to 19 m2 kg−1 at 50 cm depth. This difference is attributed to wind, which causes a rapid decrease of surface snow SSA, but forms hard windpacks whose SSA decrease more slowly with time. Since light-absorbing impurities are not concentrated enough to affect albedo, the vertical profiles of SSA and density were used to calculate the spectral albedo of the snow for several realistic illumination conditions, using the DISORT radiative transfer model. A preliminary comparison with MODIS data is presented and our calculations and MODIS data show similar trends.

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