Laboratory experiments on Dense Shelf Water formation

Polynyas-ice-free regions within sea ice-play a critical role in the sea ice production and the formation of Dense Shelf Water (DSW) in Antarctica. This dense water, formed as salt is expelled from freezing saline water (the so-called brine rejection), descends the continental slope, contributing to the formation of Antarctic Bottom Water, a key component of global thermohaline circulation. Despite the significance of polynyas and their influence on climate regulation, clear experimental evidence that brine rejection alone is capable of inducing DSW currents is lacking. This study aims to fill that gap by conducting controlled laboratory experiments simulating polynya-like conditions. Using particle image velocimetry, the velocity field in a water tank was measured under conditions of brine rejection. Experiments show that brine rejection does indeed induce gravity currents. Their flow rate was found to be dependent on the opening size of the polynya and on the geometry of the slope on which the current flows. These preliminary experiments offer a new experimental framework for studying gravity currents driven by brine rejection.