Spatial and Temporal Characterization of Sea Ice Deformation

We investigate sea ice deformation observed with GPS–instrumented ice drifting buoys deployed during late winter through summer in the Beaufort Sea. The Sea Ice Experiment: Dynamic Nature of the Arctic (SEDNA) was designed to investigate the relationship between strain-rate, stress and thickness redistribution of Arctic pack ice. In this presentation we focus on one of the four objectives of SEDNA: "Characterize the relationship between, and coherence of, stress and strain rate at 10km and 100km". Two nested arrays of six GPS buoys each, which were deployed in late March 2007 served as a backbone for the experiment. The two arrays were hexagons with initial widths of 140km and 20km. We assess whether there is a scaling relationship between strain rate and the ice area over which the strain rate is measured. Our findings demonstrate localization of strain-rate, with increased variability in the strain-rate field as spatial resolution increases. There are changes in strain-rate power across scales related to the passage of weather systems. During quiescent, anti-cyclonic periods, there is more power at the small scale. With the passage of cyclones there is enhanced power at the large scale. Coherence of strain rate between the two arrays is investigated with cross wavelet analysis. This shows a seasonal evolution in the coherence, which is probably related to disconnection in the ice pack, reducing stress transfer during the progression through spring. Finally, we present a coordinated strain-rate and in-situ measured stress time series, and identify the coherence between strain-rate(at two spatial scales) and internal ice stress, and how this evolves in time. All these investigations provide information relevant to the characterization of sea ice rheological models and will be released as a data set designed for model validation.