Improved Parameterizations of Vertical Ice‐Ocean Boundary Layers and Melt Rates

Abstract

Buoyancy fluxes and submarine melt rates at vertical ice‐ocean interfaces are commonly parameterized using theories derived for unbounded free plumes. A Large Eddy Simulation is used to analyze the disparate dynamics of free plumes and wall‐bounded plumes; the distinctions between the two are supported by recent theoretical and experimental results. Modifications to parameterizations consistent with these simulations are tested and compared to results from numerical and laboratory experiments of meltwater plumes. These modifications include 50% weaker entrainment and a distinct plume‐driven friction velocity in the shear boundary layer up to 8 times greater than the externally‐driven friction velocity. Using these updated plume parameter modifications leads to 40 times the ambient melt rate predicted by commonly used parameterizations at vertical glacier faces, which is consistent with observed melt rates at LeConte Glacier, Alaska.

Turbulent Dynamics of Buoyant Melt Plumes Adjacent Near‐Vertical Glacier Ice

“…where ν is the kinematic viscosity. This estimate of τ w is found to be consistent with laboratory and numerical simulations of turbulent flow from a vertically oriented source of distributed buoyancy (Parker et al, 2021;Zhao et al, 2024). We find τ w which is 0.0098 and 0.0053 Pa for cases 1A and 1B respectively, two to five times larger than τ w = 0.0022 Pa for case 2.…”

“…Much of what we have learned about melt comes from idealized cases of weakly turbulent laboratory experiments (Cenedese & Straneo, 2023;Josberger & Martin, 1981;McConnochie & Kerr, 2017), idealized numerical modeling (Gayen et al, 2016;Zhao et al, 2024), measurements under horizontal sea ice (McPhee et al, 1987), or…”