Author ORCID Identifier:
Date of Graduation
7-2026
Document Type
Thesis
Degree Name
Master of Science in Geology (MS)
Degree Level
Graduate
Department
Geosciences
Advisor/Mentor
Cheng, Linyin
Committee Member
Ruhl-Whittle, Laura
Second Committee Member
Feng, Song
Keywords
Climate extremes; Dissolved oxygen; Lake heatwaves; Lake morphology; Lake surface water temperature; Spatial clustering
Abstract
Lakes function as sentinels of climate change, integrating atmospheric forcing into measurable physical, chemical, and biological responses. Global warming has caused lakes in many parts of the world to experience severe hot extremes, significantly affecting the flora and fauna of these ecosystems. One of the most concerning extremes is the occurrence of lake heatwaves. Proposed in recent years, the term lake heatwave refers to prolonged episodes of anomalously high surface temperatures that can exceed the physiological thresholds of aquatic organisms. Although lake heatwaves are a relatively new concept in lacustrine ecosystems, they have received increasing research attention. However, existing studies have primarily focused on large, deep lakes, while the smaller, morphologically diverse lakes that make up the vast majority of standing water bodies remain largely unstudied. This gap is especially pronounced in the southeastern United States, a region previously identified in global syntheses as warming more slowly than many other parts of the world. Although this is true, it overlooks regional variations that influence ecosystem functioning at regional scale. This study provides the first systematic, regional-scale analysis of lake heatwaves, its controls and consequences, across 4,590 lakes in Arkansas from 1980 to 2020. This was achievable by combining daily surface-temperature reconstructions from an entity-aware deep-learning model, morphological attributes and modelled dissolved oxygen records. Heatwaves detection in this study was based on previously established percentile-based threshold, long-term trends were quantified with the modified Hamed-Rao Mann-Kendall test and the Theil-Sen slope estimator, spatial structure was assessed through global Moran’s I and the Getis-Ord Gi* hotspot statistic with false-discovery-rate control, and physical and ecological controls were examined through hierarchical and panel regression. The results revealed that lake surface water warming was positive at all lakes (statewide mean +0.208 °C decade⁻¹) and was strongest in winter and spring rather than summer. Heatwave activity intensified chiefly through longer events (+0.515 days yr⁻¹) rather than more intense ones, although the annual maximum intensity rose significantly. Spatial hotspot analysis showed two distinct spatial regimes with complementary patterns. Shallow lakes in the eastern lowland areas experienced intense but infrequent heatwaves, whereas deeper lakes in northwestern highlands exhibited frequent but less severe events. This spatial contrast was confirmed by a significant negative bivariate Moran’s I between the two metrics. Lake surface area alone explained 53.6% of the variance in mean heatwave intensity, and terrain slope was found to be the leading additional morphological control. Across nine lakes with dissolved oxygen records, heatwave intensity metrics were associated with oxygen saturation and solubility, while the secular warming trend dominated the long-term decline in oxygen concentration. By resolving the spatial, morphological, and ecological dimensions of lake heatwaves in a previously overlooked region, this study demonstrates that even modest regional warming can produce ecologically impactful thermal extremes. In addition, the study provides a transferable framework for identifying vulnerable lakes, thereby supporting targeted water-resource management.
Citation
Das, S. K. (2026). A Regional-Scale Assessment of Lake Heatwaves in Arkansas: Spatial Variability, Morphological Controls, and Ecological Consequences. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/6376
