The Determination of the Snow Optical Grain Diameter and Snowmelt Area on the Greenland Ice Sheet Using Spaceborne Optical Observations

• Published in: Remote Sensing
• Main Authors: Baptiste Vandecrux, Jason E. Box, Adrien Wehrlé, Alexander A. Kokhanovsky, Ghislain Picard, Masashi Niwano, Maria Hörhold, Anne-Katrine Faber, Hans Christian Steen-Larsen
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2022
• Subjects: Greenland ice sheet; Sentinel-3; OLCI; optical remote sensing; snow optical grain diameter; surface melt; Science; Q; Greenland; Ice Sheet
• Online Access: https://doi.org/10.3390/rs14040932; https://doaj.org/article/5296e1f50b1d4dfd8847f0b031e6db26

The optical diameter of the surface snow grains impacts the amount of energy absorbed by the surface and therefore the onset and magnitude of surface melt. Snow grains respond to surface heating through grain metamorphism and growth. During melt, liquid water between the grains markedly increases the optical grain size, as wet snow grain clusters are optically equivalent to large grains. We present daily surface snow grain optical diameters ( <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>d</mi><mrow><mi>o</mi><mi>p</mi><mi>t</mi></mrow></msub></mrow></semantics></math> ) retrieved from the Greenland ice sheet at 1 km resolution for 2017–2019 using observations from Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A. The retrieved <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>d</mi><mrow><mi>o</mi><mi>p</mi><mi>t</mi></mrow></msub></mrow></semantics></math> are evaluated against 3 years of in situ measurements in Northeast Greenland. We show that higher <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>d</mi><mrow><mi>o</mi><mi>p</mi><mi>t</mi></mrow></msub></mrow></semantics></math> are indicative of surface melt as calculated from meteorological measurements at four PROMICE automatic weather stations. We deduce a threshold value of 0.64 mm in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>d</mi><mrow><mi>o</mi><mi>p</mi><mi>t</mi></mrow></msub></mrow></semantics></math> allowing categorization of ...