Year: 2026
Type: article
Abstract: The melting of ice shelves into the ocean plays a major role, and is a key source of uncertainty, on sea level rise projections. Under ice shelves, meltwater moves upslope, setting up a stratified shear flow with the warmer, but critically saltier, ocean beneath, regulating the transfer of heat between ice and the ambient ocean. Such features are incredibly difficult to access in situ, and so most research has focussed on the use of numerical modelling, laboratory experiments and analytical models to understand these processes, each with their own assumptions, advantages and limitations. Here, we perform novel direct numerical simulations that approximate this flow where a tilted domain is forced with fixed densities at the upper and lower boundary to induce such a buoyant boundary shear current. These simulations and accompanying linear stability analysis (LSA) reveal that the shear flows under ice shelves form a unique mixed mode shear instability. The flow criticality is found to be well predicted by LSA, and dependent on diagnostic flow Reynolds and bulk Richardson numbers, and poorly captured by the local gradient Richardson number which is ill-posed for this problem. This instability consists of paired Kelvin Helmholtz and Holmboe instabilities, highly effective at mixing the water column, and due to the restoring effect of the boundary forcing, results in a cyclical instability. It is unclear how well this unusual route to turbulent mixing is represented in current models, highlighting the need for further investigation into their impact on turbulent heat transfer and ice shelf melting.
Source: Journal of Fluid Mechanics
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,550
Funders: Northumbria University, Leverhulme Trust
OpenAlex ID: W7170661173