Disruption of Arctic Staircases by Shear

Abstract

AbstractThough thermohaline staircases exist in a large fraction of the Arctic halocline, the interactions of such staircases with shear and turbulence are still largely unexplored. We perform a series of three‐dimensional Direct Numerical Simulations with and without shear and demonstrate the capacity of shear to disrupt Arctic staircases. We force an oscillating shear throughout the domain in order to represent the effects of passing internal waves of wavelengths much larger than the simulated domain. Shear is shown to disrupt staircases when the Richardson number falls below 1/4 for small layer heights (0.5 m thick), but larger layers (1 m thick) are more resistant. We determine the presence and strength of the layers using measures of steppiness from the literature, finding that a metric based on the rms temperature gradient proves most accurate. This work demonstrates that double‐diffusive interfaces can be surprisingly robust, sometimes even maintaining their structure in strong, dynamically unstable shears.