An analytical model of iceberg drift

TL;DR

This paper presents an analytical model of iceberg drift that captures key physical processes, deriving a formula for iceberg movement and explaining the empirical drift rule, with applications to Arctic and Antarctic icebergs.

Contribution

An idealized analytical model of iceberg drift is developed, providing physical insights and a formula for iceberg trajectories based on wind and ocean currents.

Findings

Icebergs drift at about 2% of wind speed relative to ocean current in strong wind conditions.

In weak winds or with large icebergs, drift aligns with ocean surface currents.

Wind strength determines whether icebergs move with wind or ocean currents.

Abstract

Iceberg drift and decay and the associated freshwater release are increasingly seen as important processes in Earth's climate system, yet a detailed understanding of their dynamics has remained elusive. Here, an idealized model of iceberg drift is presented. The model is designed to include the most salient physical processes that determine iceberg motion while remaining sufficiently simple to facilitate physical insight into iceberg drift dynamics. We derive an analytical solution of the model, which helps build understanding and also enables the rapid computation of large numbers of iceberg trajectories. The long-standing empirical rule of thumb that icebergs drift at 2% of the wind velocity, relative to the ocean current, is derived here from physical first principles, and it is shown that this relation only holds in the limit of strong winds or small icebergs, which approximately applies for typical icebergs in the Arctic. It is demonstrated that the opposite limit of weak winds or large icebergs approximately applies for typical Antarctic tabular icebergs, and that in this case the icebergs simply move with the ocean surface current. It is furthermore found that when winds are strong, wind drag drives icebergs in the direction the wind blows, whereas weak winds drive icebergs at a 90 degree angle to the wind direction.