Influences of Freshwater from Major Rivers on Global Ocean Circulation and Temperatures in the MIT Ocean General Circulation Model

Responses of global ocean circulation and temperature tofreshwater runoff from major rivers were studied by blockingregional runoff in the global ocean general circulation model (OGCM)developed at the Massachusetts Institute of Technology. Runoff intothe tropical Atlantic, the western North Pacific, and the Bay ofBengal and northern Arabian Sea were selectively blocked. Theblocking of river runoff first resulted in a salinity increase nearthe river mouths (2 practical salinity units). The saltier and,therefore, denser water was then transported to higher latitudes inthe North Atlantic, North Pacific, and southern Indian Ocean by themean currents. The subsequent density contrasts between northern andsouthern hemispheric oceans resulted in changes in major oceancurrents. These anomalous ocean currents lead to significanttemperature changes (1^oC--2^oC) by the resultinganomalous heat transports. The current and temperature anomaliescreated by the blocked river runoff propagated from one ocean basinto others via coastal and equatorial Kelvin waves. This studysuggests that river runoff may be playing an important role inoceanic salinity, temperature, and circulations; and that partiallyor fully blocking major rivers to divert freshwater for societalpurposes might significantly change ocean salinity, circulations,temperature, and atmospheric climate. Further studies are necessaryto assess the role of river runoff in the coupled atmosphere-oceansystem.