THE FUTURE OF LAKE ICE: DRIVERS, TRENDS, AND PROJECTIONS OF ICE PHENOLOGY AND ICE QUALITY

Abstract

Lake ice is changing rapidly due to climate warming, with significant ecological and societal impacts. Since lake ice provides vital ecosystem services and regulates lake conditions, understanding changing lake ice patterns is critical for managing future risks to ecosystems and communities. However, substantial knowledge gaps exist in lake ice research, including the underrepresentation of small lakes in large-scale ice phenology assessments, the lack of large-scale projections of lake ice quality, and a limited understanding of how locally and regionally altered human landscapes may influence ice dynamics. This thesis addresses these gaps by: (1) forecasting ice phenology with extensively involving representation of lakes (<1 km²) across the Northern Hemisphere (Chapter 2); (2) projecting ice quality, specifically black and white ice thickness, and implications for human safety (Chapter 3); and (3) assessing how local and regional drivers influence ice dynamics (Chapter 4). Chapter 2 reveals that lakes are losing ice faster than previously reported, with a sharp drop in ice-cover duration in the late twentieth century. Including abundant but underrepresented small lakes in predictive models improves forecasts of ice phenology under future climate scenarios. Chapter 3 extends this work by providing the first large-scale assessment of lake ice quality, indicating that warming will reduce total ice thickness and increase the proportion of weaker white ice, heightening hazards for winter travel and other activities. Chapter 4 systematically evaluates how landscape and human pressures affect ice phenology at regional and local scales, shaping ice dynamics in northern U.S. lakes. Collectively, this thesis advances our understanding of lake ice by projecting how both ice timing and ice structure are likely to change through the end of the century and clarifying the extent to which regional and local landscape characteristics may complement broader climate mitigation efforts. These findings highlight lake ice as both a sensitive indicator of climate change and a critical component of freshwater ecosystems and northern livelihoods, underscoring the urgent need for coordinated global, regional, and local responses to preserve the ecological and societal benefits of seasonal lake ice.