[Hayseed (OP)]

The cold ocean basins are a great mystery.  It's a huge capacity heat sink, for our climate to work with.  Almost all the water is consistently just above freezing.  It's energy state is minimal. This is much cooler than the soil and crust temperature of the cradles that hold them.  According to our understanding of heat flow, the oceans are probably being heated more from the cradles that hold them, thru conduction, than the sun that baths them with radiation.  And deep ocean currents are very slow.  I would think that the water needs to be constantly cooled.  I don't believe melt run off could do it.

What is the refrigerator?  Evaporation?

[Petrochemicals]

Refrigerant cycle, the hot moisture vapour rises up to the upper atmosphere where it falls below freezing to extremley cold supercooled temperatures. This water vapor then condenses, dumping its temperature difference and energy of vapourisation in the upper atmosphere far closer to the coolness of space. The water is far below zero and cooled to  supercooled temperatures, this then descends warming and removing energy from the atmosphere in the fall. The depositing of energy and water in the upper atmosphere allows a lower humidity level in the air and thus more evapouration.Thus a refrigerant cycle of the heat of vapourisation removes the energy and all balanced a4ound the triple point of water !

[evan_au]

Our oceans are heating.

Warm water carries heat away from the equator towards the poles, where it cools due to less sunlight.
In the process it melts ice.
The water is now denser; it sinks and flows back towards the equator, completing the cycle.
But tests with autonomous submersibles show that the water temperatures are warming.
See: https://en.wikipedia.org/wiki/Thermohaline_circulation

[MarkPawelek]

autonomous submersibles show that the water temperatures are warming

Due to the action of sunlight. The so-called greenhouse effect does not heat oceans.
1st. Because greenhouse gas climate warming is pseudoscience. As shown by Connolly's 5 years ago. (papers at "Open Peer Review Journal"). Summarized here.
2nd. Because even if the GHGE was not junk science, down-welling infrared from CO2 15µm band only penetrates mere micrometres into water. It can warm the surface skin. This surface skin readily cools by both of the atmospheric cooling mechanisms - evaporative cooling and black body emission.

So only sunlight warms the oceans. This is mostly absorbed in the top 5 metres. Sunlight penetrates no further than 100m. Ocean bottoms are warmed by nothing apart from tiny geological warming.

Add to that: the lightest water is pushed to the top by convection. The densest, coldest, saltiest sinks.

Nothing makes the oceans cold, apart from cooling. The explanation is: nothing is making oceans warm.

[evan_au]

only sunlight warms the oceans. This is mostly absorbed in the top 5 metres

But wind waves drives currents that take the warmth lower.

And ocean overturning currents take it much lower (over a period of decades), which keeps the surface waters relatively cool despite  the observed warming of the water column in the oceans.

[Petrochemicals]

autonomous submersibles show that the water temperatures are warming

Due to the action of sunlight. The so-called greenhouse effect does not heat oceans.
1st. Because greenhouse gas climate warming is pseudoscience. As shown by Connolly's 5 years ago. (papers at "Open Peer Review Journal"). Summarized here.
2nd. Because even if the GHGE was not junk science, down-welling infrared from CO2 15µm band only penetrates mere micrometres into water. It can warm the surface skin. This surface skin readily cools by both of the atmospheric cooling mechanisms - evaporative cooling and black body emission.

So only sunlight warms the oceans. This is mostly absorbed in the top 5 metres. Sunlight penetrates no further than 100m. Ocean bottoms are warmed by nothing apart from tiny geological warming.

Add to that: the lightest water is pushed to the top by convection. The densest, coldest, saltiest sinks.

Nothing makes the oceans cold, apart from cooling. The explanation is: nothing is making oceans warm.

Evapouration will only take place if the air allows ie the humidity and dew point.  If not the sea is forced to emit radiation.  Sea humidity is very high, water is slow to warm and sucks alot of the energy from the nearby air by means of conductive transmittance in airborn spray, keeping the air cool and lowering the dew point further. Warm spray, circulating ocean currents to the poles (undeniable no evidence needed widley known) remove heat.  The more humid the air is the more radiation is emmitted and less evapouration occours, at the poles with less sunlight, more energy is emmitted  than absorbed.

The specific heat of water and latent heat of evapouration are large which keeps the ambient temperature low. The temperature in the vecinity may not be of a high enough level to rise to allow cooling, thus water is largley held in the atmosphere until it hits the thermal risers of the land mass to cause rise and cooling then precipitation. I hypothesise if all water evapourated at sea the entire oceans would be a constant mass of cyclones (propper eye wall).