Intensification of the global water cycle and evidence from ocean salinity: a synthesis review

The ocean plays a dominant role in the global water cycle. It is the center of action for global evaporation and precipitation and supplies the moisture that falls as continental precipitation. It also acts to some extent as nature's rain gauge, as it tells us about the long-term changes in the global water cycle through monitoring of the changes in ocean surface salinity. As climate warms, the global water cycle is expected to intensify as a result of the strong nonlinear dependence of water vapor pressure (moisture-holding capacity) on temperature. Such change is of great concern, as it has profound socioeconomic impacts throughout the globe. Despite the evidence of an intensified global water cycle, two important questions remain: What is the pattern of the warming-induced intensification of the water cycle? and What is the rate of intensification? Our article provides a synthesis review of recent progress in diagnosing and understanding the changes in both the global water cycle and ocean salinity in recent decades. Targeted numerical ocean model experiments are also reviewed to provide insights into the response of salinity to the changes in evaporation-minus-precipitation flux, meltwater runoff, and ocean warming.