除了热喷口附近深海通常被认为是非常酷。For instance, The Mariana Trench (~10 km deep) is 1-4 °C. However, the geothermal gradient runs counter to that, where the lithosphere at the same 10km depth would be around 250-300 °C. So, in a sense, water should be heated from beneath and only be able to release its energy into the atmosphere/space. Yet, we see the exact opposite of this, where the upper layers are the warmest. If we ignore convection and only allow for heat transfer due to conduction, then the heat would flow from the upper surface into the deep. And over billions of years equilibrium would only be maintained if the deep waters could shed their heat into a heat sink, i.e. the seafloor. But we know the geothermal heat is flowing up from below and so after billions of years with heat flowing from above (solar loading) and below (geothermal conduction) the temperatures would have risen. Convection remains the only pathway for cooling. However, convection also works from hot to cold, so for the deeps to be 1-4 °C the water would have to have been cooler before arriving there. This points toward circulation from the poles. Where did the thermal energy go? Is it really just the product of billions of years of ocean currents carrying the heat to the poles, or am I overlooking some other principle? (Hit me with the hard science and math, my masters focus was in thermodynamics and heat transfer.)