Dense water formation on the Antarctic continental shelf is the main process by which Antarctic Bottom Waters form and is fundamental to the abyssal overturning circulation. However, most ocean models fail to simulate Antarctic dense water formation on the continental shelf and flow down the continental slope (i.e., overflow) due to resolution constraints. While the impact of horizontal and vertical resolution on the overflows has been previously studied, the effect of surface vertical resolution on dense water formation remains unexplored. To address this gap, we vary the surface ocean grid cell of two dense water-forming models from 1.1 m to 5.1 m thickness. We used the ACCESS-OM2-01 and the Pan-Antarctic ocean and sea ice models, each employing a different boundary layer parameterisation. Thickening the surface cell to 5.1 m in ACCESS-OM2-01 decreased the dense water formation by 64% and ceased its overflow after 10 years of simulation. In the Pan-Antarctic, thickening the surface cell reduced the dense water formation by 32% and its overflow by 67% after 10 years. The dense water formation reduction in the experiments with thicker surface grid cells is explained by a southward shift in the surface Ekman transport, which brings light offshore waters to the coast and limits dense water formation at the continental shelf. These results highlight that a high vertical resolution at the ocean surface is required to form Antarctic dense waters.
