Sea ice diffusion in the Arctic ice pack: a comparison between observed buoy trajectories and the neXtSIM and TOPAZ-CICE sea ice models

• Published in: The cryosphere 2016-01, Vol.2016 (1), p.1
• Main Authors: Rampal, Pierre, Bouillon, Sylvai, Bergh, Jon, Ólason, Eina
• Format: Article
• Language: English
• Subjects: Analysis; Sea ice
• ISSN: 1994-0416; 1994-0424

Due to the increasing activity in Arctic, sea ice--ocean models are now frequently used to produce operational forecasts, for oil spill trajectory modelling and to assist in offshore operations planning. In this study we propose a method based on a Lagrangian diffusion analysis to evaluate the sea ice drift properties simulated by two sea ice models, TOPAZ-CICE and neXtSIM, used in two different sea ice--ocean systems developed for such applications. We compare their results to the buoy trajectories of the International Arctic buoy Program (IABP) data set and we find that neXtSIM performs better than TOPAZ-CICE in simulating the mean and fluctuating sea ice velocities over the central Arctic in winter. Our analyses indicate that both TOPAZ-CICE and neXtSIM are able to simulate two distinct sea ice diffusion regimes depending on the time scale considered, similarly to what is predicted by the steady and homogenous turbulent flow theory. However, the basin-averaged absolute diffusion computed from the analysis of drifters trajectories simulated with TOPAZ-CICE is almost twice as high as the value estimated from both the corresponding drifters trajectories simulated with neXtSIM and from observed buoy trajectories. Also, the mean Arctic pattern of absolute diffusion obtained from TOPAZ-CICE shows large differences from the one obtained from the observed buoy trajectories, while the neXtSIM results are much more consistent with the results from the buoy trajectories. The information on the mean drift and diffusivity fields provided by our analysis can be used in an advection/diffusion equation or with Lagrangian passive tracers models to study the drift of e.g. pollutants or micro-organisms moving with the ice. More generally, the analysis presented in this paper should be seen as a useful evaluation metric of coupled sea ice--ocean models that aim at being used in operational forecasting platforms, for process and climate studies.