2014/03/10 by Nathan Martin, Martin, Nathan, Jérôme Monnier +1
Earth and Planetary Sciences · Environmental Science · Mathematics · Medicine · Physics and Astronomy · #Classical Physics (physics.class-ph) #Climate change and permafrost #Cryospheric studies and observations #FOS: Mathematics #FOS: Physical sciences #Landslides and related hazards #Optimization and Control (math.OC) #Winter Sports Injuries and Performance #math.OC #physics.class-ph
paper · pdf · doi:10.48550/arxiv.1403.2148
Accepted to The Cryosphere (2014)
arxiv created 2014/03/10 · openalex publication_date 2014/03/10 · arxiv updated 2014/03/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
This work focuses on the numerical assessment of the accuracy of an adjoint-based gradient in the perspective of variational data assimilation and parameter identification in glaciology. Using noisy synthetic data, we quantify the ability to identify the friction coefficient for such methods with a non-linear friction law. The exact adjoint problem is solved, based on second order numerical schemes, and a comparison with the so called "self-adjoint" approximation, neglecting the viscosity dependency to the velocity (leading to an incorrect gradient), common in glaciology, is carried out. For data with a noise of 1%, a lower bound of identifiable wavelengths of 10 ice thicknesses in the friction coefficient is established, when using the exact adjoint method, while the "self-adjoint" method is limited, even for lower noise, to a minimum of 20 ice thicknesses wavelengths. The second order exact gradient method therefore provides robustness and reliability for the parameter identification process. In other respect, the derivation of the adjoint model using algorithmic differentiation leads to formulate a generalization of the "self-adjoint" approximation towards an incomplete adjoint method, adjustable in precision and computational burden.