Climate‐driven alterations of lake thermal regimes

Abstract

Temperate lakes are undergoing climate‐driven alterations in their thermal regimes, changing their ecology. Previous efforts to understand temperature changes have overlooked multi‐dimensional temperature dynamics, missing complex shifts at high spatiotemporal resolutions across landscapes. Here, we use simulated daily water temperature profiles from > 11,000 temperate lakes throughout the Midwestern United States to (1) quantify multivariate, landscape‐scale patterns in contemporary thermal regimes and (2) contextualize forecasted shifts and identify novel regimes that may emerge with climatic change. Hierarchical clustering and principal component analyses identified six lake clusters with distinct thermal regimes driven by differences in annual warming rates and spring–summer dynamics, with secondary influences from extreme heat events and seasonal variability. Annual temperature variations were influenced by lake‐specific physical characteristics, emphasizing distinct thermal profiles and seasonal variability patterns. Projected climate‐driven alterations in thermal regimes suggest a homogenization toward warmer and more variable conditions, with the majority of lakes characterized by higher temperatures and increased variability. Few lakes (n = 310), particularly in the southern and southeastern Midwest, may experience novel, non‐analog conditions by the late 21st century, while others will undergo shifts between clusters but remain within analogous regime frameworks. Projected changes in lake thermal regimes highlight concerns about ecological impacts on aquatic species and habitats, especially as extreme and variable growing season temperatures intensify and periods of stratification become prolonged. Furthermore, we identify thermal regimes that are likely to dominate the region by the late 21st century while identifying those likely to be lost. The ecological consequences of such changes remain unknown.