Advancing Sea Ice Modeling for a Coupled Storm Surge–Wave–Ice Forecast System for Alaska’s Western Coasts

Storm surges and their associated flooding events are hazardous phenomena along Alaska’s western coasts. Regional forecasters and communities in this region have challenges to assess threats, to determine risk and the potential impacts of storms, or to evaluate safe evacuation routes and locations. In addition to complicated interactions among atmosphere, waves, and ocean circulation, the unique factor that brings further complexity to this region is sea ice. Sea ice alters the air-sea momentum transfer, accelerates/slows ocean currents, and dampens waves. All these processes collectively impact the intensity of storm surges and flooding.

A recent collaborative work, funded by the National Oceanic and Atmospheric Administration (NOAA) National Ocean Service’s (NOS) U.S. Integrated Ocean Observing System (IOOS), is underway to build an integrated storm surge, wave, and sea ice model system for the coasts of Western Alaska. The prototype system will be hosted by the Alaska Ocean Observing System (AOOS) to provide a real time operational forecasting products for forecasters and local communities. The product suite will include a coupled model system based on the Advanced Circulation coastal ocean model (ADCIRC), the WAVEWATCH III model (WWIII), and the Los Alamos Sea Ice model (CICE).

In this presentation, we present the ongoing development of the stand-alone sea ice model based on the CICE version 6 as a concurrent effort with other model development components (ADCIRC, WWIII) within the larger collaborative framework. The sea ice model domain covers the Gulf of Alaska, Bering, Chukchi, Beaufort, and East Siberian Seas. The model has 3-km spatial resolution and currently forced by the atmospheric data from the operational analysis of the Climate Forecast System (CFS) version 2 and the ocean data from the Global Ocean Forecasting System (GOFS) 3.1. Verification of the model results is conducted in comparison with the sea ice extent analysis from the National Ice Center, the ice thickness measurements from satellite missions including the Soil Moisture and Ocean Salinity (SMOS) and the Ice, Cloud and land Elevation Satellite-2 (ICESat-2), and the freeze-up measurements from the IOOS-Ocean Technology Transition Ice Detection Buoy (IDB). We conduct a series of numerical experiments to test different parameterizations for the air-ice and ice-ocean drag coefficients, including the constant values and the form drag parameterizations based on recent theoretical developments (Lüpkes et al. 2012, J. Geophys. Res., Tsamados et al. 2014, J. Phys. Oceanogr.). The aim is to evaluate how these parameterizations impact the momentum transfer between the atmosphere and the ocean during the storm events, as well as the overall ice motion, concentration and thickness. After rigorous verification of the model results and evaluation of the numerical experiments, the sea ice model will be integrated into the coupled storm surge and wave model system based on ADCIRC and WWIII using the Earth System Modeling Framework (ESMF).