The East Pacific has been cooling for a couple of decades, it turns out. A “warming hole”, we have to call it. Persistent strong trade winds are part of the reason. Chinese researchers have also found that, in their words:
“a persistent cooling in the eastern Pacific is directly linked to an eastward displacement of the Southeast Pacific Subtropical Anticyclone (SPSA). Interactions between the Andes and an eastward shift of the SPSA generate greater pressure gradients in the eastern flank, in turn, stronger alongshore winds and more intense upwelling …”
Here’s the paper: https://iopscience.iop.org/article/10.1088/1748-9326/abd819/meta
One suspects that the ongoing cooling of the Humboldt current from Antarctica north along the western South America’s coast is also part of the cause:
Elsewhere, South African scientists studied the responses of Sparid reef fish to either warming or cooling outside of their normal water temperatures. They found that stress was encountered more quickly by cooling than by warming of their surrounding water:
Substantial sea surface cooling events associated with the Madden Julian Oscillation appear to be getting more frequent recently, such as the one in the Banda sea to the east of Indonesia in 2015:
Meanwhile the Southern ocean south of latitude 55 has cooled also in recent decades, associated with further wind driven spread of Antarctic sea ice. This adds a layer of fresher but cold water at the southern ocean surface, which reminds buoyant above warmer but more saline water deeper down. It’s been noted elsewhere that during glacial periods, warm water remains trapped under the greatly expanded sea ice.