Sensitivity of dynamical downscaling in the Northern Adriatic Sea

This study evaluates the performance of dynamical downscaling in the Northern Adriatic Sea, focusing on eddy kinetic energy spectra and dense water formation. Using the perfect model framework, a high-resolution (2 km) reference simulation of the entire Adriatic Sea serves as the benchmark for a series of one-way nesting downscaling experiments reaching the same horizontal resolution in the Northern Adriatic. Results show that a downscaling ratio of 1:3 effectively reproduces the local energy budget and multiscale features. However, the absence of feedback from small to large scales limits the downscaling performance. This limitation is evident in dense water formation, which is controlled by the interplay between local and remote drivers in the Northern Adriatic Sea. When local drivers, such as buoyancy fluxes, dominate, the dense water formation process is well reproduced. In contrast, when remote influences, particularly the inflow of salty Levantine Intermediate Water through the Otranto Strait, are not properly resolved by the parent model, reproducibility of dense water formation deteriorates. Our experiments indicate that a 2 km horizontal resolution effectively captures cross-scale interactions at the strait, while a 6 km resolution is insufficient. These interactions, particularly feedback from small scales to large scales, lead to changes in thermohaline dynamics that propagate toward the Northern Adriatic Sea.