neXtWIM: Waves in a next-generation sea ice model

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2015

End date

12/31/2019

Budget

674,901 EUR

Fundings

Abstract

With increasing temperatures worldwide, the Arctic is experiencing rapid changes in sea ice conditions. In particular, the sea ice extent has experienced several record lows in the last decade, producing more open water in the Arctic ocean, and consequently more waves. At the same time many industries - both in Norway and other countries - such as tourism, fishing, shipping and the oil and gas industry are seeking to take advantage of the reduced ice cover to expand their operations. However, accidents in the Arctic could have enormous (and unpredictable) repercussions on the environment, human lives, the economy and the society in general. The hazards of operating in the Arctic was exemplified by the grounding of the Northguider fishing vessel in the Hinlopen Strait (Svalbard) in December 2018. In this incident the 14-member crew had to be evacuated by the Norwegian coast-guard and the vessel's 300,000L of diesel had to drained, presumably at considerable expense. In this project, we have set up a forecast system (neXtSIM-F, based on the neXt-generational Sea Ice Model, neXtSIM) to provide information about sea ice conditions in the Arctic. This may both prevent such accidents and assist response teams should they occur. This forecast system was verified to be giving realistic predictions of sea ice drift, concentration, thickness and extent. To build this forecast system involved a significant amount of work from all members (past and present) of the Sea Ice Modelling group at NERSC. First the performance of the model had to be improved by translating the code behind it from the desktop application Matlab to C++. It then needed to be sped up further by enabling it to run in parallel (Samaké et al, 2017). Moreover several new physical and diagnostic components of the model had to be developed simultaneously. A waves-in-ice component was also implemented inside neXtSIM and was used in a study of the effect of the wave radiation stress and the potential impact of ice fragmentation due to waves on the sea ice dynamics. In an idealised study (in a rectangular box domain, without thermodynamic effects) it found that wind effects were dominating the wave ones overall, since the wind was acting over a larger area, while the waves were mostly acting at the ice edge (Williams et al, 2017). However, this conclusion still needs to be tested in a more realistic setting. Unfortunately this waves-ice module proved to be too costly computationally to run and we were unable to implement it fully in the parallelised version of the model, where it might have been able to run faster. However, we have tried another approach where neXtSIM has been coupled to the wave model Wavewatch III (WW3) through the coupler OASIS. Since WW3 already runs in parallel, this has enabled simulations over the whole Arctic to be done at a resolution of about 12km, which indicate that there is some effect on the sea ice drift and thickness in areas broken by waves (Boutin et al, in prep). References: Boutin, G., T. D. Williams, P. Rampal, E. Ólason & C. Lique, in prep. Wave-ice interactions in a brittle sea ice rheological framework. Samaké, A., P. Rampal, S. Bouillon, and E. Ólason, 2017. Parallel implementation of a Lagrangian-based model on an adaptive mesh in C++: Application to sea-ice. J. Comp. Phys., 2017, 350, 84-96. https://doi.org/10.1016/j.jcp.2017.08.055. Williams, T., P. Rampal, and S. Bouillon. "Wave?ice interactions in the neXtSIM sea-ice model." The Cryosphere 11.5 (2017): 2117-2135. https://doi.org/10.5194/tc-11-2117-2017. Williams, T., A. Korosov, P. Rampal, and E. Ólason, under review. Presentation and evaluation of the Arctic sea ice forecasting system neXtSIM-F. The Cryosphere Discussions. https://doi.org/10.5194/tc-2019-154.