Abstract
Saltwater intrusion is a critical challenge to coastal ecosystems, impacting
freshwater resources, biogeochemical cycles, and habitat stability. While
relevant studies often focus on the long-term trends of salinity, its episodic
variability and resulting ecological disturbance remains underexplored. Here,
we introduce the concept of "coastal salt waves" - periods of elevated salinity
anomalies, akin to heat waves - to better characterize extreme salinity events
and emphasize their significance. Using cases studies, we show that coastal
salt waves exhibit significant spatial and temporal variability based on their
duration, intensity, frequency, cumulation, and timing, with drivers and
impacts that may differ from gradual saltwater intrusion. In years with similar
average salinity, salt waves may still vary greatly in characteristics like
intensity, resulting in varying environmental impacts. Furthermore, systems
without rising average salinity may still face more frequent or intense salt
waves. This framework supports monitoring and management strategies to mitigate
coastal salinization risks.