Oh, my goodness! Let's analyse bit by bit -as Jack the Ripper used to say-. The oceans are not the main source of radiation back to the space, I mean, more that being the 70% of the total surface.
It's also difficult to conceive an ocean that has 10 or 20°C at the surface, in contact with the atmosphere and in optimal conditions to radiate into space and yet having waters at -3000m at 1, 2 or 3°C that would be cold because they radiate heat into space passing through a thick layer of cloudy and warmer waters? This doesn't pass the most simple reality check we can do. [Homer: «Lisa! In this house we obey the laws of thermodynamics!»]
About all the circulations and the reference, you are basically speaking of the 0-400m layer, so it's another subject.
Let me explain as, if you don't know, probably most participants here also don't know.
The origin of so low temperature in deep waters lies mostly in both polar sea ice areas. Every year some 32,000 km3 of ice are formed -by surface water and the atmosphere radiating heat into space when they are in the dark or almost in the dark- and as a result some 20,000 km3 of brine at -2°C are created. A brine that has all the salts of 52,000 km3 of sea water, so it's cold, it's extremely heavy and it's going down quickly in virtual columns similar to pipes. Of course this heavily concentrated brine takes some of the already cold polar winter waters and the concentration decreases, but not enough to stop the process of an increasing volume reaching the sea bottom. Some roughly 100,000 km3 reach the bottom every year. Let say, for the sake of our arithmetic, that 100,000 km3 or "sea water" at -1°C reaches the bottom. This mass has to neutralize the heat of the crust. How much is it? Almost all the geothermal energy reaches the oceans, so, let say 40 terawatt have to be absorbed by those 100 teratons of chilly water, what gives us a temperature of +2°C.
The question is, how many years does the Earth need to have -700m-to-bottom waters at this temperature if it started today? About 10,000 years! That's a lot of time. What does that say? First, this is a permanent feature of the planet, a much needed anchor. Second, temperatures are as average a few degrees above that figure, so some ocean mixing has occurred, but not much [This is the right/wrong supposition that has put deep oceans in a marginal climatic role]
This answers much roughly my first question. My second question goes towards that ocean mixing and why temperatures are not raising as "expected".
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