Abstract:
As Earth’s climate changes, rates of precipitation and evaporation are expected to accelerate, intensifying the pace of the water cycle. At the same time, the atmosphere’s
water-holding capacity will increase, allowing moisture to travel longer distances between evaporation source regions and precipitation sinks. The result is that many regions will shift their reliance from more local to more remote sources of moisture for their water supplies. Hydrogen and oxygen isotope ratios in water provide a rare way to track this shift since they record evaporation (E) and precipitation (P) along moisture transport paths, which ultimately define the length scales of moisture transport. Using two decades of isotopic data from satellite, we provide evidence that length scale changes may already be evident, especially over Earth’s landmasses. We will discuss the implications of this shift for the severity of weather, natural hazard risks, and the security of water resources.