Results from a number of modeling studies suggest that the Atlantic meridional overturning circulation (AMOC) is enhanced by the volcano activities. The deepwater formation at the northern end of the Atlantic Ocean allows SST anomalies to be subducted into the deep ocean efficiently because the rate of overturning is altered by changes in salinity. The decreasing summer-time ice melting and precipitation due to the volcano cooling enhance the salinity near the Greenland Sea, and further reduces static stability, which means more surface water sinks into the deep ocean. The studies of Stenchikov et al. (2009) and Iwi (2012) suggest that both Krakatau and Pinatubo may have strengthened the overturning circulation. And the increase in AMOC seems to be strongest at about one decade after the volcano eruption, with a magnitude of about one sverdrup for Krakatau and Pinatubo.