Arctic Sea Ice Dynamics: Drift and Ridging in Numerical Models and Observations

• Main Author: Martin, Torge
• Other Authors: Lemke, Peter, Dethloff, Klaus
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2007
• Subjects: sea ice; sea ice drift; ridging; laser profiling; numerical modeling; Arctic; 530; 530 Physics; ddc:530; Arktis*; Sea ice
• Online Access: https://media.suub.uni-bremen.de/handle/elib/2394; https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000107733

The Arctic sea ice cover is constantly in motion driven by the wind and ocean currents. The transport of freshwater and latent heat is associated with the ice drift. Furthermore, the drift causes deformation of the sea ice cover under compressive and shear forces and pressure ridges form. Ridges in turn affect the momentum and---to a minor degree---the heat exchange between sea ice and atmosphere and ocean because they strongly increase the local surface roughness and thickness of the ice. Therefore, the sea ice drift and deformation interact with the climate system and its changes, and it is a key issue to both the remote-sensing and modelling community to provide products of good quality. The present thesis splits into three parts: a study of modelled and observed drift estimates, an analysis of sea ice ridge quantities derived from laser altimeter and airborne electromagnetic measurements and an investigation of different numerical algorithms for the representation of ridges in a large-scale sea ice model.The study of sea ice drift focuses on the comparison of different sea ice-ocean coupled models and the validation with buoy and remote-sensing data of the period 1979--2001 on the basis of monthly averages. According to drift speed distributions the group of models, which matches best the observations, has a mode at drift speeds around 0.03 m/s and a short tail towards higher speeds. However, there are also models with much larger drift speeds. In general, all models are capable of producing realistic drift pattern variability although differences are found between models and observations. Reasons for these differences are manifold and lie in discrepancies of wind stress forcing as well as sea ice model characteristics and sea ice-ocean coupling.The investigation of sea ice ridges is based on Arctic-wide in situ measurements of the period 1995--2005 which include different sea ice roughness regimes. While sail density is found to emphasise local deformation events sail height features a large-scale, positive ...