Positive h stores subsurface heat. Through coupling c, it can push the SST tendency upward before the largest surface anomaly appears.
Guided Experiment / ENSOBuild a
Build a
recharge oscillator.
Surface temperature + ocean memory
A deliberately small model shows how subsurface heat can lead, support, and eventually reverse a surface-temperature anomaly.
The question
How can the ocean remember what the surface has forgotten?
Let T represent an eastern-Pacific sea-surface temperature anomaly and h an upper-ocean heat-content or thermocline anomaly. The atmosphere–ocean coupling allows stored heat to reinforce surface warming. The surface response then discharges that heat reservoir, producing a delayed negative feedback.
dT/dt = 0.42T − 0.18T³ + c h
dh/dt = −d h − 0.62T
dh/dt = −d h − 0.62T
This conceptual oscillator exposes one ENSO mechanism. It is not an operational forecast model and omits seasonal forcing, spatial structure, weather noise, and model error.
Change the mechanism
Try this
Increase d. Does shorter ocean memory weaken or accelerate the oscillation? Reverse h(0). Which variable changes sign first?
Time series · blue SST T · red heat content h
Phase plane · the state cycles through T–h space
Warm SST drives h downward through the −0.62T term. The reservoir is depleted and the initial warming loses support.
Observing both T and h is more informative than observing SST alone. But unresolved forcing and imperfect parameters still broaden the range of possible futures.