# Ocean tides trigger ice shelf rift growth and calving

## TL;DR

Ocean tides play a key role in triggering iceberg calving from ice shelves, as shown by a 2023 event on the Brunt Ice Shelf in Antarctica.

## Contribution

The study demonstrates that ocean tides directly influence the timing of rift propagation and calving events in ice shelves.

## Key findings

- Rift propagation on the Brunt Ice Shelf was influenced by ocean tides, wind, and an iceberg collision.
- A viscoelastic model identified a critical stress threshold for fracture, exceeded in early 2019.
- The 2023 calving event coincided with a peak spring tide, confirming tides' direct influence on timing.

## Abstract

Tabular iceberg calving reduces ice-shelf extent, affecting ocean circulation and ice-sheet stability. Here we present detailed observations of a rift on the Brunt Ice Shelf, East Antarctica, from 2017-2023 and its behaviour in the lead up to calving in January 2023. The timing of rift propagation was controlled by the rate of change of ocean tide height, wind speed, and an iceberg collision in August 2021, as well as the long-term ice dynamics. A viscoelastic rheological model is used to estimate the relative magnitude of stresses acting on the rift and to determine a critical threshold for fracture, which was exceeded during a sequence of propagation events in early 2019. The eventual calving on 22nd January 2023 occurred at the peak of a spring tide, supporting the conclusion that tides directly influenced the timing.

Timing of fracture is a major uncertainty in ice sheet models. Here the authors show ocean tides can create peaks in stress, enabling crack growth. Calving of a 1500 km2 iceberg from the Brunt Ice Shelf in 2023 coincided with a peak spring tide.