Lagrangian analysis of sea-ice dynamics in the Arctic Ocean

Abstract

In this study, we present Lagrangian diagnostics to quantify changes in the dynamical characteristics of the Arctic sea-ice cover from 2006 to 2014. Examined in particular is the evolution in finite-time Lyapunov exponents (FTLEs), which monitor the rate at which neighbouring particle trajectories diverge, and stretching rates throughout the Arctic. In this analysis, we compute FTLEs for the Arctic ice-drift field using the 62.5 km daily sea-ice motion vector data from the European Organisation for the Exploitation of Meteorological Satellites Ocean and Sea Ice Satellite Application Facility. Results from the FTLE analysis highlight the existence of three distinct dynamical regions with strong stretching, captured by FTLE maxima or ridges. It is further shown that FTLE ridges are dominated by shear, with contributions from divergence in the Beaufort Sea. Localization of FTLE features following the 2012 record minimum in summertime sea-ice extent illustrates the emergence of an Arctic characterized by increased mixing. Results also demonstrate higher FTLEs in years when lower multi-year ice extent is observed.

• sea-ice dynamics
• FTLE
• Arctic Ocean
• Lagrangian diagnostics
• LAD

Acknowledgements

The authors would like to thank Professor George Haller for helpful advice and suggestions, and for facilitating this study. The authors would also like to thank two anonymous reviewers for their helpful advices. SS was funded by the Scientific Exchange Programme (project code 13.073). DGB was funded by the Canadian Networks of Centres of Excellence program and a Canada Research Chairs grant. The authors thank OSI SAF for providing sea-ice motion data.