ISSM-SESAW v1.0: mesh-based computation of gravitationally consistent sea level and geodetic signatures caused by cryosphere and climate driven mass change

Abstract

Abstract. A classical Green's function approach to computing gravitationally consistent sea level variations, following mass redistribution on the earth surface, employed in contemporary state-of-the-art sea-level models naturally suits the spectral methods for numerical evaluation. The capability of these methods to resolve high wave number features such as small glaciers is limited by the need for large numbers of pixels and high-degree (associated Legendre) series truncation. Incorporating a spectral model into (components of) earth system models that generally operate on an unstructured mesh system also requires cumbersome and repetitive forward and inverse transform of solutions. In order to overcome these limitations of contemporary models, we present a novel computational method that functions efficiently on a flexible mesh system, thus capturing the physics operating at kilometer-scale yet capable of simulating geophysical observables that are inherently of global scale with minimal computational cost. The model has numerous important geophysical applications. Coupling to a local mesh of 3-D ice-sheet model, for example, allows for a refined and realistic simulation of fast-flowing outlet glaciers, while simultaneously retaining its global predictive capability. As an example model application, we provide time-varying computations of global geodetic and sea level signatures associated with recent ice sheet changes that are derived from space gravimetry observations.