The effects of salinity and inclination on the morphology of melting ice

TL;DR

This study investigates how salinity and inclination affect ice melt morphology and rate, revealing five distinct surface regimes and a complex salinity-dependent melt behavior through detailed experiments.

Contribution

It introduces a comprehensive experimental analysis of melting ice morphology influenced by salinity and inclination, identifying five surface regimes and their underlying mechanisms.

Findings

Five surface morphologies identified: scalloped, channelized, top-melting, bottom-melting, incurved.

Salinity affects scallop size, depth, and uniformity.

Melt rate exhibits non-monotonic dependence on salinity.

Abstract

The salinity of water and the slope of ice significantly influence the melt rate and surface morphology of ice, both highly relevant in the context of glacier and iceberg melting in oceanic environments. In this study, we conducted experiments on vertical and sloped ice blocks melting in quiescent saline water. Through the use of fringe projection profilometry, we measured the morphology of the ice's front face. In particular, we combine the spatio-temporal phase shifting and orthogonal sampling moire methods. The far field salinity in the experiments ranged from 0 g/kg to 35 g/kg, and angles were between -18{\deg} and 50{\deg}. The ice block sizes were 32 cm $\times$ 23 cm $\times$ 12 cm high, wide, and long respectively, leading to Ra = $\mathcal{O}(10^7)$. We identified and classify five surface morphologies and regimes arising from the flow regimes imposed by salinity and inclination, namely scalloped, channelized, top-melting, bottom-melting, and incurved. The channelized morphology consists of vertical channels carved along the ice surface, whose development originates from a Rayleigh--B\'enard type instability, and which are enhanced by bubbles released from the melting ice and rising along the interface. The scalloped regime is characterize by a rough dimpled pattern commonly referred to as scallops. We observe that increasing the salinity leads to scallops that are smaller, shallower, and more uniform in size. Additionally, a salinity dependence of the melt rate is found, showing a non-monotonic behavior, while the inclination angle shows little influence on the overall melt rate.