Coupled ADCIRC+SWAN simulations of Lake Superior with surface ice cover in February 2020

The analyses of the Great Lakes Environmental Research Laboratory's (GLERL) historical ice cover data during 1973–2021 indicate that warmer winters with reduced surface ice cover have become more frequent in the last two decades (1995–2021) compared to the previous decades (1973–1995) in the Great Lakes. In the past two decades, for example, years with lower-than-normal ice cover have become more frequent in Lake Superior, which has a history of freezing almost completely. These observations suggest a possible regime shift to a lower-ice state for this lake. It is hypothesized that the transition to a lower-ice state in the next decades may have significant implications for coastal hazards such as wave-induced coastal erosion and flooding, depending on surface ice-wave interactions and their possible effects on Lake Superior's hydrodynamics. The literature; however, lacks any effort that analyzes Lake Superior’s surface ice-wave interactions, resulting in limited knowledge on the dynamics of these interactions within this and similar lakes. In this regard, a set of numerical simulation were carried out using the coupled circulation and spectral wave model, ADCIRC (v55.01) +SWAN (41.31AB), to investigate the contribution of surface ice to lake-wide hydrodynamics, wave power, and wave runup in Lake Superior. Simulations specifically focused on the year 2020, known for its comparatively reduced surface ice cover in recent years, and the ice-wave interactions were quantified for February, the month with the largest surface ice cover. The coupled model was forced with Great Lakes Coastal Forecasting System (GLCFS) hourly wind field data, National Centers for Environmental Prediction Forecast System, version 2 (CFSv2) atmospheric pressure, GLER surface ice concentration, and U.S. National Ice Center (USNIC) thickness. The lake bathymetry used in the simulations was obtained from NOAA GLERL.

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