Oceanic Heat Content

[Dave R]

Can someone explain to me the difference between oceanic heat content and the ocean temperature? Now, I understand that a hurricane needs warm water to a certain depth, but what I don't understand is why shallow water does not contain the oceanic heat content as deeper water. When the water is deep, doesn't upwelling become a factor as the storm churns up the cooler water from deep below the surface? With shallow water, there is no deep cool water to bring to the surface.

[Wthrman13]

In shallow water, however, even though it may be warm all the way to the bottom, there isn't much of it, so basically what is happening is that turbulence from a hurricane is mixing all that warm water around repeatedly, and will quickly extract all the energy from the water through multiple overturnings, provided the hurricane stays over the shallow water long enough. The key thing to keep in mind here is that hurricanes cool the ocean surface layer not only through mixing with cooler waters from below, but also through evaporative cooling (as water evaporates from the sea surface, called the "latent heat flux", it cools the sea surface off accordingly). So, you can get ocean cooling even without underlying cold water.

In the case of shallow warm water overlying cooler water, not only is the energy from the warm water extracted quickly, as in the above case, it is also mixed and diluted by cool water dredged up from underneath. Thus, for a hurricane that is moving slow enough, the deeper the layer of warm water (which determines the oceanic heat content in this context), the more energy can be extracted (in the form of latent heat flux from the ocean surface) before the water is cooled or mixed with cooler water.

Hope that helps.

[Dave R]

Thanks for the explanation. Now, I understand. Doesn't the actual rain from the hurricane cool the ocean surface in addtion to the processes that you described?