Coupled Spatial Variability in the Sea Ice-Ocean System: From Ice Growth to Internal Waves

Abstract

Changes in the extent, thickness, drift speed, and phenology of sea ice are altering atmosphere-ice-ocean interactions with the potential to modify climate feedback mechanisms. This thesis shows how spatial heterogeneities of the sea ice pack and the ocean mixed layer affect the coupled evolution of both media. Chapter 2 demonstrates how lateral variability in mixed layer properties feeds back into ice growth during the autumn freeze-up. Chapter 3 and Chapter 4 examine how sea ice variability impacts inertial oscillation development and internal wave generation. In Chapter 2, we used observations from autonomous vehicles, remote sensing, and a mixed layer model to show how advected sea ice meltwater cooled and restratified the mixed layer, causing earlier freeze-up than in adjacent waters. By demonstrating how melt-related temperature and stratification anomalies precondition freeze-up in predictable ways, our results can improve freeze-up forecasting. Chapter 3 used moored velocity observations, remote sensing, and an idealized ice-ocean slab model to demonstrate how sea ice lead opening permitted inertial oscillation development in winter despite persistently high ice concentrations, whereas an unfractured ice pack selectively filtered out near-inertial motions. Our results indicate that wintertime near-inertial motion predictions should account for the lateral scales of ice fracturing and cannot rely on free-drift proxies like ice concentration. Chapter 4 investigated ways in which sea ice affected the fate of energy contained in mixed layer inertial oscillations, including near-inertial internal wave generation. Moored observations, drifting buoys, and ice floe tracking in satellite imagery were used to quantify the spatial coherence scales of inertial oscillations in the marginal ice zone. Our results support the hypothesis that sea ice properties can promote spatially divergent inertial oscillations, resulting in internal wave generation. This research demonstrated reciprocal impacts between spatial variability in the sea ice and the ocean. In addition to the process-level conclusions described above, this dissertation also contributed methods for integrating data from distributed observational platforms, remote sensing, and simple models to generate system-level understanding of the coupled evolution of the atmosphere-ice-ocean system.