Downstream Hydrology Reduces Glaciers' Direct Contribution to Sea‐Level Rise

Abstract Glacier mass loss is a primary contributor to sea‐level rise. All prior assessments assume all glacial melt water reaches the ocean, but many mountain glaciers are located far from oceans and may be affected by the downstream systems. Here we track future glacier runoff through the hydrological system and estimate ∼95% directly reaches the ocean through the river systems for all emissions scenarios, while the remaining 5% is lost (consumed) via evapotranspiration or stored on land. Endorheic basins in High Mountain Asia account for 76%–82% of the glacier runoff that does not directly reach the ocean. The remaining 18%–24% is lost or stored in exorheic basins, including those with considerable anthropogenic water use like the Indus and Ganges. While the percentage of glacier runoff reaching the ocean differs between basins, the percentages are roughly constant over time for most basins.