Linear Ice Fraction: Sea Ice Concentration Estimates from the ICESat-2 Laser Altimeter

• Main Authors: Horvat, Christopher, Buckley, Ellen, Stewart, Madelyn, Yoosiri, Poom, Wilhelmus, Monica M.
• Format: Text
• Language: English
• Published: 2023
• Subjects: Sea ice
• Online Access: https://doi.org/10.5194/egusphere-2023-2312; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2312/

Sea ice coverage is a key indicator of changes in the global climate. Estimates of sea ice area and extent are primarily derived from satellite measurements of surface microwave emissions, from which local sea ice concentration (SIC) is derived. Passive microwave (PM) satellite sensors remain the sole global product for understanding SIC variability. Using a dataset of more than 27,000 high-resolution airborne optical images, we first examine biases in commonly-used products that emerge from challenges in sampling thin sea ice fractures and melt ponds on the sea ice surface. We show that the ICESat-2 (IS2) laser altimeter effectively samples these surface features and we develop a new, independent SIC product, which we term the Linear Ice Fraction (LIF). On monthly timescales, we show using an emulator that the LIF product offers an independent estimate of sea ice concentration over 60 % of the Arctic sea ice cover with similar-or-better error qualities compared to PM data. IS2 and its high-precision measurements of the sea ice surface  should be considered for augmenting PM-SIC measurements in the future.