Drop in Ocean Heat Content

OHC numbers for the second quarter of 2018 are in, and they show some significant (but not seriously anomalous) drops:

Numbers indicate exponents.

Reminder - the data are here: 0-700 meters, 0-2000 meters, and I calculate the global means per the area of the Earth (not per the ocean area only), since most (> 90%) of the "trapped heat" goes into the ocean.

Big drops. These have happened before, so it's not a big deal. But where did the heat go? (I know, it's a complicated question without any simple answer.)