Comparing Arctic Sea Ice Model Simulations to Satellite Observations by Multiscale Directional Analysis of Linear Kinematic Features

Abstract

Sea ice models have become essential components of weather, climate, and ocean models. A realistic representation of sea ice affects the reliability of process representation, environmental forecast, and climate projections. Realistic simulations of sea ice kinematics require the consideration of both large-scale and finescale geomorphological structures such as linear kinematic features (LKF). We propose a multiscale directional analysis (MDA) that diagnoses the spatial characteristics of LKFs. The MDA is different from previous analyses in that it (i) does not detect LKFs as objects, (ii) takes into account the width of LKFs, and (iii) estimates scale-dependent orientation and intersection angles. The MDA is applied to pairs of deformation fields derived from satellite remote sensing data and from a numerical model simulation with a horizontal grid spacing of ~4.5 km. The orientation and intersection angles of LKFs agree with the observations and confirm the visual impression that the intersection angles tend to be smaller in the satellite data compared to the model data. The MDA distributions can be used to compare satellite data and numerical model fields using conventional metrics such as a Euclidean distance, the Bhattacharyya coefficient, or the Earth mover’s distance. The latter is found to be the most meaningful metric to compare distributions of LKF orientations and intersection angles. The MDA proposed here provides a tool to diagnose if modified sea ice rheologies lead to more realistic simulations of LKFs.

Deformation lines in Arctic sea ice: intersection angles distribution and mechanical properties

“…LKFs-tracking algorithms show that the current VP models overestimate the intersection angles, with an IAD peaking at 90 • Hutter and Losch, 2020). This behavior is shared by all other rheological models as a recent comparison of state-of-the-art models revealed (Hutter et al, 2022), and is also observed using MDA (Mohammadi-Aragh et al, 2020). To improve the IAD in high-resolution sea ice models, the observed IAD could be used to improve the definition of weakly constrained sea ice rheological parameters: the yield curve and the plastic potential.…”

“…Recent work based on an LKFs tracking algorithm report an intersection angles distribution (IAD) between 0 • and 90 • with a peak between 40 • to 50 • (Hutter and Losch, 2020). Multi-scale directional analysis (MDA) on the RGPS dataset also shows that small intersection angles are dominant (Mohammadi-Aragh et al, 2020).…”

The 2020 International Verification Methods Workshop Online: Major Outcomes and Way Forward

“…Sea ice verification. Sea ice verification research has flourished in the context of the Polar Prediction Project, and several new spatial verification methods have been developed in recent years (Dukhovskoy et al 2015;Melsom et al 2019;Goessling et al 2016;Goessling and Jung 2018;Mohammadi-Aragh et al 2020;Linow and Dierking 2017). At the workshop A. Cheng presented a novel symmetric distance metric for the verification of ice-edge.…”

SubZero: A Sea Ice Model With an Explicit Representation of the Floe Life Cycle

“…Under this assumption, the floe interactions can be represented statistically (Feltham, 2008; Hibler, 1977). Nonetheless, high‐resolution numerical simulations can generate discontinuities that resemble observed linear kinematic features (Hutter & Losch, 2020; Hutter et al., 2022; Mehlmann et al., 2021; Mohammadi‐Aragh et al., 2020). But despite the major progress of continuous modeling of large‐scale sea ice and the ongoing developments in pushing their applicability limits by increasing the resolution, the rheological models are not meant to represent the scales of motion at which individual floes start to affect dynamics (Coon et al., 2007).…”