Ocean Dynamics and Ice Fractures

Abstract

Ice, a pervasive element across the Solar System, holds immense importance in understanding the response of the Earth to ongoing climate change as well as the dynamics of planetary bodies. This dissertation investigates ice fractures on terrestrial and planetary ice bodies, focusing on their impact on the melting of ice shelves in Antarctica and their dynamics on Europa, one of Jupiter’s moons.

The urgency to understand the behavior of terrestrial ice shelves under environmental forcing is driven by the ongoing climate crisis. Antarctica is experiencing a rapid loss of mass, primarily due to increasing ocean-induced melting at the base of its ice shelves in response to global warming. The release of glacier meltwater into the world’s oceans contributes to arising the global sea level. However, the rate and magnitude of sea-level rise are highly uncertain and the potential ice mass-loss from Antarctica could significantly accelerate sea-level rise throughout this century due to the instability of its ice shelves. Thus, accurately projecting Antarctica’s contribution to global sea level necessitates a better understanding of the processes behind the loss of its ice shelves.

In this dissertation, I examine the thinning of Antarctic ice shelves caused by enhanced melting at their base due to warming oceans. Intrusion of ocean heat beneath the ice shelves indeed plays a crucial role in projecting their future. Through idealized ocean modeling using the Massachussetts Institute of Technology general circulation model (MITgcm), I simulate ocean dynamics under the ice, investigating the impact of fractures and ice front retreat on the sub-shelf ocean circulation. Results indicate that fractures may act as barriers, inhibiting the intrusion of warm water towards the inland sections of the ice shelves, and thereby reducing basal melt. Furthermore, I examine the impact of the separation of iceberg A-68 from the Larsen C ice shelf in July 2017 on the sub-shelf ocean dynamics. This specific retreat event leads to the redistribution of heat under the ice, resulting in enhanced melting in specific sections of the ice shelf, suggesting future destabilisation of Larsen C. These findings highlight the importance of considering updated ice-shelf coastlines to accurately project ocean circulation and its implications for ice shelf stability.

Furthermore, this dissertation explores the dynamics of specific lineament features observed on the surface of Europa, which are identified as ice fractures. Although limited observations restrict our understanding of ice fracturing events on this moon, insights from studying terrestrial ice sheets provide valuable knowledge. By extend ing an existing terrestrial-based numerical model of fracture propagation on ice shelves, I show that some lineaments on the surface of Europa exhibit a behavior that is similar to ice fractures on Antarctic ice shelves. The model depicts the evolution of these lineament features as bursts of fracture propagation events interspersed with periods of inactivity, which is a typical behavior of fractures on terrestrial ice shelves.

Overall, this dissertation shows the potential for synergy between Earth and planetary science. By leveraging advances in our understanding of physical processes on Earth, terrestrial-based models and theories contribute to expanding our knowledge of physics on other celestial bodies. This interdisciplinary approach, supported and validated by remote sensing and in-situ missions, is fundamental in order to advance our understanding of ice fractures, their interaction with the surrounding environment and their dynamics throughout the Solar System. On Earth, a better understanding of the dynamics of Antarctic ice shelves is imperative to correctly project Antarctica’s contribution to global sea level.