Probabilistic Forecasts of Sea Ice Trajectories in the Arctic: Impact of Uncertainties in Surface Wind and Ice Cohesion

Sukun Cheng,Alberto Carrassi,Ali Aydoğdu,Pierre Rampal,Laurent Bertino

doi:10.5194/egusphere-egu21-5141

Abstract

&lt;p&gt;We evaluate the impact of uncertainties in surface wind and sea ice cohesion on sea ice forecasts by the neXtSIM sea ice model. neXtSIM includes the Maxwell-elasto-brittle rheology describing the ice dynamics. Ensemble forecasts are done every 10 days from January to April 2008. The ensembles are generated by perturbing the wind forcing and ice cohesion field both separately and jointly. The wind forcing, an external forcing of the model, is perturbed continuously during the forecast. While the sea-ice cohesion, an internal parameter of the model, is randomized on the initial field of each sea ice forecast. The model uncertainties are assessed statistically using ensemble forecasts, in which virtual drifters are seeded over the Arctic Ocean. We analyze the spread of Lagrangian sea ice trajectories of the ensemble of virtual drifters and compare them with the IABP buoys. We demonstrate that the wind perturbations usually contribute more to the forecast uncertainty, but the ice cohesion perturbations significantly increase the degree of anisotropy in the spread and become occasionally important during strong wind events.&lt;/p&gt;

Highlights

Sea ice covering the polar oceans is an important component of the Earth System
Note that neXt generation Sea Ice Model (neXtSIM) only tracks the positions of virtual drifters when the concentration within a model grid cell is greater than 15%
Results hRWIND iS,for forall all t, so time is dropped from the notation for clarity

Summary

Introduction

Sea ice covering the polar oceans is an important component of the Earth System. The dramatic changes in sea ice extent and volume in the Arctic have been regularly reported in recent decades [1–3].It is, crucial to understand the new state and characteristics of Arctic sea ice and how it impacts the regional and global weather and climate [4]. Sea ice covering the polar oceans is an important component of the Earth System. The dramatic changes in sea ice extent and volume in the Arctic have been regularly reported in recent decades [1–3]. It is, crucial to understand the new state and characteristics of Arctic sea ice and how it impacts the regional and global weather and climate [4]. Reliable sea ice forecasting systems are demanded for both operational and academic purposes [5]. A thinner sea ice cover offers opportunities to exploit trans-Arctic shipping routes but its faster dynamics challenge the safety of operations [6]. One specific and important aim of sea ice models is to represent small-scale dynamics such as the formation of leads and ridges, together with the large-scale drift patterns of big ice plates and small ice Oceans 2020, 1, 326–342; doi:10.3390/oceans1040022 www.mdpi.com/journal/oceans

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Discussion

Conclusion