Discharge of major global rivers in the late 21st century climate projected with the high horizontal resolution MRI-AGCMs

摘要

This study used an atmospheric general circulation model (AGCM) with a 20-km grid spacing and a global river routing model withn0.5u0001 grid resolution to project climatological mean river discharges in the late 21st century under a changing climate. We alsonperformed an ensemble simulation with the same AGCM except with a resolution of 60 km and forced with different lower boundarynconditions to quantify the level of confidence in the projections. By the late 21st century, projected annual mean river dischargesnincreased in the high latitudes and in India and the southeastern United States but decreased in broad regions of Europe, western Asia,nthewesternUnited States,CentralAmerica, and the southern half of theAmazonRiver basin. Projected future changes inmonthly riverndischarges include unique seasonal details not present in the annual discharge projections: in the Amazon River, for example, riverndischarges were projected to increase in the high-water season but decrease in the low-water season. These seasonal changes suggestnthat monthly river discharge projections should be useful for assessing the human impacts and risks in future planning of waternresources and flood control. We devised a way to measure the consistency between the various projections made by our 60-kmnensemble simulations and our standard 20-km high-resolution model. Wherever the projected changes were consistent, the futurenchanges also tended to be statistically significant in our high-resolution model. These results encourage a future projection of dischargenfor a specific river basin in the world. Copyright © 2013 John Wiley & Sons, Ltd.