Diel Surface Temperature Range Scales with Lake Size

Ecological and biogeochemical processes in lakes are strongly dependent upon water temperature. Long-term surface warming of many lakes is unequivocal, but little is known about the comparative magnitude of temperature variation at diel timescales, due to a lack of appropriately resolved data. Here we quantify the pattern and magnitude of diel temperature variability of surface waters using high-frequency data from 100 lakes. We show that the near-surface diel temperature range can be substantial in summer relative to long-term change and, for lakes smaller than 3 km2, increases sharply and predictably with decreasing lake area. Most small lakes included in this study experience average summer diel ranges in their near-surface temperatures of between 4 and 7°C. Large diel temperature fluctuations in the majority of lakes undoubtedly influence their structure, function and role in biogeochemical cycles, but the full implications remain largely unexplored.Additional co-authors: Martin Kernan, Jan Krokowski, Alon Rimmer, Kevin C Rose, James A. Rusak, David B. Ryves, Daniel R. Scott, Ewan M. Shilland, Robyn L. Smyth, Peter A. Staehr, Rhian Thomas, Susan Waldron, Gesa A. Weyhenmeye