How to infer ocean freezing rates on icy satellites from measurements of ice thickness

TL;DR

This paper develops a scaling law to estimate ocean freeze and melt rates beneath icy satellite shells from ice thickness measurements, validated with Antarctic data, aiding understanding of subsurface ocean dynamics.

Contribution

It introduces a first-principles scaling law linking ice shell thickness to ocean freeze/melt rates, applicable to icy satellites.

Findings

Freeze/melt rates range from 0.1 to 0.00001 mm/year.

Validation with Antarctic radar data supports the model.

Scaling law enables estimation of ocean dynamics from ice measurements.

Abstract

Liquid-water oceans likely underlie the ice shells of Europa and Enceladus, but ocean properties are challenging to measure due to the overlying ice. Here, we consider gravity-driven flow of the ice shells of icy satellites and relate this to ocean freeze and melt rates. We employ a first-principles approach applicable to conductive ice shells in a Cartesian geometry. We derive a scaling law under which ocean freeze/melt rates can be estimated from shell-thickness measurements. Under a steady-state assumption, ocean freeze/melt rates can be inferred from measurements of ice thickness, given a basal viscosity. Depending on a characteristic thickness scale and basal viscosity, characteristic freeze/melt rates range from around O(10$^{-1}$) to O(10$^{-5}$) mm/year. Our scaling is validated with ice-penetrating radar measurements of ice thickness and modelled snow accumulation for Roosevelt Island, Antarctica. Our model, coupled with observations of shell thickness, could help estimate the magnitudes of ocean freeze/melt rates on icy satellites.