Rapid change of snow surface properties at Vostok, East Antarctica, revealed by altimetry and radiometry

We present results of snow surface properties using the ENVISAT dual frequency altimeter at S (3.2 GHz) and Ku (13.6 GHz) bands and the AMSR-E microwave radiometer at frequencies ranging between 6 and 36 GHz in the Vostok region, East Antarctica. The altimetric time series observed between 2002 and 2008 show variations at 3 different time scales (daily, seasonal and inter-annual), that correlate directly with variations in the snow surface properties. In this study we focus on the analysis of the rapid daily event, occurring on February 14th 2005, that created a jump of the backscatter coefficient of up to 5.3 dB at the S band and 2.5 dB at the Ku band. The ratio of V/H-polarization brightness temperature slowly decreased in December and January 2005, and suddenly increased on February 14th 2005. The origin of this rapid event is investigated using AWS data from Vostok station, altimetric and radiometric data simultaneously. Both snow surface density and roughness are found to vary during this event. This event is shown to be synchronous with strong wind occuring during a period of anomalous wind direction, and the presence of surface hoar. These particular conditions certainly modified the snow surface roughness and thus impacted the altimetric signal. We finally investigate the impact of this event on the calculation of the regional ice-sheet mass-balance using different corrections of height with echo shape variations. It is shown to be negligible only if the full echo shape correction (Legresy et al., 2006) is used.

[1]  B. Legrésy,et al.  Ice Sheet And Satellite Altimetry , 2001 .

[2]  Li Jun,et al.  Modeled seasonal variations of firn density induced by steady-state surface air-temperature cycle , 2002, Annals of Glaciology.

[3]  K. C. Partington,et al.  A model of satellite radar altimeter return from ice sheets , 1988 .

[4]  David G. Long,et al.  Azimuth variation in microwave scatterometer and radiometer data over Antarctica , 2000, IEEE Trans. Geosci. Remote. Sens..

[5]  R. Alley,et al.  Spatial and temporal characterization of Hoar Formation in central Greenland using SSM/I brightness temperatures , 1993 .

[6]  Monique Dechambre,et al.  On the use of the dual-frequency ENVISAT altimeter to determine snowpack properties of the Antarctic ice sheet , 2008 .

[7]  V. Masson‐Delmotte,et al.  The changes in isotope composition and accumulation of snow at Vostok station, East Antarctica, over the past 200 years , 2004, Annals of Glaciology.

[8]  Norman C. Grody,et al.  Relationship between snow parameters and microwave satellite measurements: Theory compared with Advanced Microwave Sounding Unit observations from 23 to 150 GHz , 2008 .

[9]  V. Masson‐Delmotte,et al.  Spatial and temporal variability in isotope composition of recent snow in the vicinity of Vostok station, Antarctica: implications for ice-core record interpretation , 2002, Annals of Glaciology.

[10]  R. Arthern,et al.  Controls on ERS altimeter measurements over ice sheets: Footprint-scale topography, backscatter fluctuations, and the dependence of microwave penetration depth on satellite orientation , 2001 .

[11]  Monique Dechambre,et al.  Dual-frequency altimeter signal from Envisat on the Amery ice-shelf , 2007 .

[12]  Christian Mätzler,et al.  Polarization effects in seaice signatures , 1984 .

[13]  Frédérique Rémy,et al.  Altimetric observations of surface characteristics of the Antarctic ice sheet , 1997 .

[14]  A. Hachikubo,et al.  Effect of wind on surface hoar growth on snow , 1997 .

[15]  P. Mazzega,et al.  Mapping of the Topography of Continental Ice by Inversion of Satellite-altimeter Data , 1989, Journal of Glaciology.

[16]  Richard K. Moore,et al.  Radar remote sensing and surface scattering and emission theory , 1986 .

[17]  H. Zwally,et al.  Microwave Emissivity and Accumulation Rate of Polar Firn , 1977 .

[18]  Sylviane Surdyk,et al.  Using microwave brightness temperature to detect short-term surface air temperature changes in Antarctica: An analytical approach , 2002 .

[19]  Jack L. Saba,et al.  Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002 , 2005 .

[20]  Refined analysis of radar altimetry data applied to the region of the subglacial Lake Vostok/Antarctica , 2007 .

[21]  Frédérique Rémy,et al.  Using the temporal variability of satellite radar altimetric observations to map surface properties of the Antarctic ice sheet , 1998 .

[22]  M. R. van den Broeke,et al.  Elevation Changes in Antarctica Mainly Determined by Accumulation Variability , 2008, Science.

[23]  Fabien Blarel,et al.  Along Track Repeat Altimetry for Ice Sheets and Continental Surface Studies , 2006 .

[24]  A. Sihvola,et al.  The complex dielectric constant of snow at microwave frequencies , 1984 .

[25]  J G Marsh,et al.  Growth of Greenland Ice Sheet: Measurement , 1989, Science.

[26]  S. Colbeck,et al.  Theory of metamorphism of dry snow , 1983 .

[27]  H. Zwally,et al.  Modeling the density variation in the shallow firn layer , 2004, Annals of Glaciology.

[28]  M. Fily,et al.  Surface melting derived from microwave radiometers: a climatic indicator in Antarctica , 2007, Annals of Glaciology.

[29]  Fabrice Papa,et al.  ENVISAT radar altimeter measurements over continental surfaces and ice caps using the ICE-2 retracking algorithm , 2005 .

[30]  R. Scharroo,et al.  Antarctic elevation change from 1992 to 1996 , 1998, Science.