Moored observations of atmospheric variables and upper-ocean temperatu
res from the Long-Term Upper-Ocean Study (LOTUS) and the Frontal Air-S
ea Interaction Experiment (FASINEX) are used to examine the upper-ocea
n response to surface heating. FASINEX took place between January and
June 1986 at 27 degrees N, 70 degrees W while LOTUS took place between
May and October 1982 at 34 degrees N, 70 degrees W. The frequency-dom
ain transfer function between rate of change of heat and the net surfa
ce heat flux is consistent with a one-dimensional heat balance between
heating and convergence of vertical turbulent heat flux at timescales
longer than the inertial. The observations satisfy the vertically int
egrated one-dimensional heat equation and indicate that the response t
o surface heating has been successfully isolated. Within the internal
waveband, upward phase propagation in the response is inconsistent wit
h a one-dimensional balance and the vertically integrated heat balance
fails. The internal waveband response is explained as a balance betwe
en rate of change of heat, mixing, and vertical advection. A simple mo
del, which admits internal waves forced by an oscillatory surface buoy
ancy flux, illustrates the competition between these three terms. Stra
tification modulates the depth to which surface heating is mixed. The
estimated eddy diffusivity may be considered a linear function of freq
uency where the scaling constant reflects the mixed layer depth.