Observations from moored buoys during spring of 1998--2000 suggest that the warming of the mixed layer (~20 m deep) of the north Indian Ocean warm pool is a response to net surface heat flux Qnet (~100 W m-2) minus penetrative solar radiation Qpen (~45 W m-2). A residual cooling due to vertical mixing and advection is indirectly estimated to be about 25 W m-2. The rate of warming due to typical values of Qnet minus Qpen is not very sensitive to the depth of the mixed layer if it lies between 10 m and 30 m.