Assessment of compound hot-dry events in lakes across global drylands

Lake hot events (months with abnormally high lake surface water temperature) and dry events (months with abnormally low lake surface extent) can individually cause significant stress to lake ecosystems. When these events occur simultaneously, as compound hot-dry events, their impacts can be even more severe, particularly in dryland regions. Yet, their frequency, long-term dynamics, and driving factors remain poorly understood. Here, we leverage model-derived lake surface water temperature and satellite-derived surface area datasets to identify and analyze hot events, dry events, and compound hot-dry events in 2,338 lakes across global drylands from 1985 to 2020. We find that the occurrence of compound hot-dry event has significantly increased in 520 lakes, while 240 lakes have shown a significant decrease. Hot events and dry events individually increased in 1007 and 767 lakes, respectively. Furthermore, in most lakes, the temporal changes in compound hot-dry events are primarily driven by changes in dry event frequency, rather than hot events or their co-occurrence. These findings underscore the growing compound stress on dryland lake systems and emphasize the need for targeted adaptation and resilience strategies.