Bistability in radiatively heated melt ponds

TL;DR

This paper reveals a bistability phenomenon in melt pond dynamics on ice surfaces, showing how solar radiation and initial conditions can cause abrupt transitions between frozen and melted states, with implications for Earth's heat balance.

Contribution

It introduces a combined numerical and theoretical analysis demonstrating bistability in melt ponds, linking phase transitions with turbulent convection and radiation effects.

Findings

Identification of a bistability transition in melt ponds

The heat flux model accurately predicts temperature and flow

Agreement between simulations and theoretical predictions

Abstract

Melting and solidification processes, intertwined with convective flows, play a fundamental role in geophysical contexts. One of these processes is the formation of melt ponds on glaciers, ice shelves, and sea ice. It is driven by solar radiation and is of great significance for the Earth's heat balance, as it significantly lowers the albedo. Through direct numerical simulations and theoretical analysis, we unveil a bistability phenomenon in the melt pond dynamics. As solar radiation intensity and the melt pond's initial depth vary, an abrupt transition occurs: This tipping point transforms the system from a stable fully frozen state to another stable equilibrium state, characterized by a distinct melt pond depth. The physics of this transition can be understood within a heat flux balance model, which exhibits excellent agreement with our numerical results. Together with the Grossmann-Lohse theory for internally heated convection, the model correctly predicts the bulk temperature and the flow strength within the melt ponds, offering insight into the coupling of phase transitions with adjacent turbulent flows and the interplay between convective melting and radiation-driven processes.