The Role of Islands in Sea Ice Transport Through Nares Strait

Nares Strait is an important export pathway of sea ice, where its transport is highly intermittent due to the formation and collapse of sea ice arches. The islands in the strait, especially Hans Island, contribute to heightened collision forces between distinct ice floes and the land. However, since even state-of-the-art climate models remain relatively coarse and use continuous sea ice rheology, the complexities of floe-scale sea ice interactions with small islands in the Nares Strait have not been sufficiently explored. Here, we use a novel discrete element model, SubZero, to identify the role of small islands in affecting intense summer-time sea ice transport in the Nares Strait. We show that SubZero can reproduce crucial sea ice characteristics, including observed area transport, intermittency of area fluxes, and floe size distribution (FSD) derived from satellite imagery. We find that the intermittency of sea ice fluxes is sensitive to the power-law exponent of the simulated FSD, and matching it to observations implies that the floe strength for fracturing must be inversely proportional to the square root of its length scale. Conducting sensitivity simulations with modified coastlines, we identified several islands as crucial pinning points that suppress sea ice transport and cause jamming, especially during low- to moderate-wind conditions. The momentum budget reveals the islands slow down sea ice through direct normal contact with colliding floes and by increasing tangential drag forces from lateral coastal boundaries. Our study emphasizes floe-scale interactions with islands and other coastlines in large-scale sea ice transport through narrow straits.