Abstract:

Polar ice sheets hold the largest freshwater reserves and profoundly impact global climate change and sea level rise. Ice sheet models are important technical tools for modeling and predicting ice sheet movement. The basal friction distribution is a key boundary condition for solving the ice flow dynamics equations, which is crucial for modeling ice sheet dynamics and predicting future changes. Numerical inversion technology has been widely used in the study of polar ice sheet dynamics to estimate basal friction coefficients in ice sheet models. However, there has not yet been a dedicated review on basal friction inversion methods for polar ice sheets. This paper first reviews recent advances in basal friction inversion of polar ice sheets, and summarizes the commonly used basal friction inversion methods. On this basis, it points out the problems of overfitting and solution instability in the inversion process. Introducing explicit regularization is an effective way to solve the above problems, but the key lies in how to select a reasonable regularization parameter. Then, the latest method for determining the optimal regularization parameter of inversion is introduced in detail, which is based on automatically identifying the inflection point of the L-curve. This method helps to obtain an accurate and reasonable basal friction distribution. Finally, the uncertainty of the basal friction inversion problem is analyzed, and the advantages and limitations of determining the optimal regularization parameter through L-curve analysis in solving the inversion overfitting problem and improving the solution stability are discussed. This paper is expected to provide methodological support for accurately modeling the basal environment of ice sheets and further understanding the connection and interaction mechanisms between subglacial conditions and ice sheet dynamics.

Key words: ice sheet model, inversion, basal friction, regularization, L-curve