Overestimation and adjustment of Antarctic ice flow velocity fields reconstructed from historical satellite imagery

• Published in: The Cryosphere
• Main Authors: R. Li, Y. Cheng, H. Cui, M. Xia, X. Yuan, Z. Li, S. Luo, G. Qiao
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: geo; envir; Antarctic; David Glacier; Pine Island Glacier; The Antarctic; Totten Glacier; Antarc*; Ice Sheet; Ice Shelf; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-16-737-2022; https://tc.copernicus.org/articles/16/737/2022/tc-16-737-2022.pdf; https://doaj.org/article/cabf7f96df8c433296eb9f695e649ba4

Antarctic ice velocity maps describe the ice flow dynamics of the ice sheet and are one of the primary components used to estimate the Antarctic mass balance and contribution to global sea level changes. In comparison to velocity maps derived from recent satellite images of monthly to weekly time spans, historical maps, from before the 1990s, generally cover longer time spans, e.g., over 10 years, due to the scarce spatial and temporal coverage of earlier satellite image data. We found velocity overestimations (OEs) in such long-span maps that can be mainly attributed to velocity gradients and time span of the images used. In general, they are less significant in slow-flowing grounded regions with low spatial accelerations. Instead, they take effect in places of high ice dynamics, for example, near grounding lines and often in ice shelf fronts. Velocities in these areas are important for estimating ice sheet mass balance and analyzing ice shelf instability. We propose an innovative Lagrangian velocity-based method for OE correction without the use of field observations or additional image data. The method is validated by using a set of ground truth velocity maps for the Totten Glacier and Pine Island Glacier which are produced from high-quality Landsat 8 images from 2013 to 2020. Subsequently, the validated method is applied to a historical velocity map of the David Glacier region from images from 1972–1989 acquired during Landsat 1, 4, and 5 satellite missions. It is demonstrated that velocity overestimations of up to 39 m a−1 for David Glacier and 195 m a−1 for Pine Island Glacier can be effectively corrected. Furthermore, temporal acceleration information, e.g., on basal melting and calving activities, is preserved in the corrected velocity maps and can be used for long-term ice flow dynamics analysis. Our experiment results in the Pine Island Glacier (PIG) show that OEs of a 15-year span can reach up to 1300 m a−1 along the grounding line and cause an overestimated grounding line (GL) flux of 11.5 Gt a−1 if ...