Phil Klotzbach has graciously permitted me to post an update on upper ocean heat content in the equatorial upper ocean. He writes
“The Climate Prediction Center recently released its equatorial upper ocean heat content for April 2010. One of the primary areas that they focus on is the equatorial heat content averaged over the area from 180-100W. The decrease in upper ocean heat content from March to April was 1C, which is the largest decrease in equatorial upper ocean heat content in this area since the CPC began keeping records of this in 1979. The upwelling phase of a Kelvin wave was likely somewhat responsible for this significant cooling. It seems like just about every statistical and dynamical model is calling for ENSO to dissipate over the next month or two as well, so it’s probable that we will see a transition to neutral conditions shortly. I have attached a spreadsheet showing upper ocean heat content data from CPC since 1979. In case you’re interested, the correlation between April upper ocean heat content from 180-100W and August-October Nino 3.4 is an impressive 0.75 over the years from 1979-2009.
He has plotted the data below. An interesting question is to where this heat has gone. It could have moved north and south in the upper ocean, however, to the extent the sea surface temperature anomalies map to the upper ocean heat content, there is no evidence of large heat transfers except, perhaps, in the tropical Atlantic [see].
The heat could have been transferred deeper into the ocean. However, if this is true, this heat would have been seen moving to lower levels, but, so far, there is no evidence of such a large vertical heat transfer.
The heat could, of course, be lost to space. This appears to be the most likely explanation.