Dynamics of the snow grain size in a windy coastal area of Antarctica from continuous in situ spectral-albedo measurements

• Published in: The Cryosphere
• Main Authors: S. Arioli, G. Picard, L. Arnaud, V. Favier
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Antarctic; The Antarctic; Antarc*; Antarctica; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-17-2323-2023; https://doaj.org/article/9121cd86c2e94c18993a40f852aefb39

The grain size of the superficial snow layer is a key determinant of the surface albedo in Antarctica. Its evolution is the result of multiple interacting processes, such as dry and wet metamorphism, melt, snow drift, and precipitation. Among them, snow drift has the least known and least predictable impact. The goal of this study is to relate the variations in surface snow grain size to these processes in a windy location of the Antarctic coast. For this, we retrieved the daily grain size from 5-year-long in situ observations of the spectral albedo recorded by a new multi-band albedometer, unique in terms of autonomy and described here for the first time. An uncertainty assessment and a comparison with satellite-retrieved grain size were carried out to verify the reliability of the instrument, and an RMSE up to 0.16 mm in the observed grain size was found. By relating these in situ measurements to time series of snow drift, surface temperature, snow surface height and snowfall, we established that the evolution of the grain size in the presence of snow drift is complex and follows two possible pathways: (1) a decrease in the grain size (about half of our measurements) resulting from the deposition of small grains advected by the wind (surprisingly, this decrease is often – 2 / 3 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="20pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="3496efcea5f297ee507fe8b4bd2d4fd4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-17-2323-2023-ie00001.svg" width="20pt" height="14pt" src="tc-17-2323-2023-ie00001.png"/></svg:svg> of the cases– associated with a decrease in the surface height, i.e., a net erosion over the drift episode), (2) an increase in the grain size (the other half) due to either the removal of the surface layer or metamorphism. However, we note that this increase is often limited with respect to the increase predicted by a theoretical metamorphism model, suggesting that a concomitant deposition of small ...