Sea Ice Discrete Element Modeling: Melt and Fracture of Floes and Sheets

• Main Author: Moncada Lopez, Rigoberto
• Format: Thesis
• Language: English
• Published: 2024
• Subjects: Arctic; Arctic Ocean; Baffin Bay; Baffin; Sea ice
• Online Access: https://thesis.library.caltech.edu/16133/; https://thesis.library.caltech.edu/16133/1/Moncada_Rigoberto_2024_revised.pdf; https://resolver.caltech.edu/CaltechTHESIS:07032023-235459528

Over the last 40 years, the Arctic Ocean has experienced a significant reduction in surface area and thickness of sea ice for its minimum summer and year-round values. Sea ice, existing both as continuous ice sheets and distinct broken floes or blocks, is disappearing earlier and faster over time. These changes are largely occurring within marginal ice zones, where ice is most vulnerable to thermal forcings from the sun, oceans, and atmosphere and wind and ocean currents. Given that sea ice plays a vital role in regulating climate by delaying global energy exchanges, its loss is a vital factor in increasing global temperatures and the frequency of extreme weather events. Understanding and projecting seasonal variations in sea ice is imperative to improve climate predictions. However, many of the processes in sea ice are not fully described by most existing models, due to the limitations of continuum sea ice approaches. As a result the use of discontinuum techniques on sea ice is a very active field. In this work, we combine discrete element methods with satellite image analysis to study changes in sea ice concentration and floe size distribution during the summer melt transition for ensembles of distinct floes decaying into open waters and continuous fast sea ice sheets breaking into multiple floes. For the pure floe-like behavior, we use the `Level Set Discrete Element Method for Sea Ice' or LS-ICE method. This model can resolve individual sea ice floes with realistic shapes, and represent their physical interactions by leveraging level-set functions to detect contacts. LS-ICE can also be coupled to atmospheric and oceanic heat and momentum forcings and simulate associated melt and breakage processes. With it, we are able to reproduce sea ice concentration decline for the summers of 2018 and 2020 at Baffin Bay. Using LS-ICE we also unveil the sensitivity of sea ice loss and floe size distribution to different intensities of fracturing and ocean/solar melt and how sea ice floe size determines which is more ...