Jargon Buster – Thermocline
If you dive frequently, you may have heard the term Thermocline (thermal = temperature/ heat, cline = layer). For someone who has never dived like me, the closest term I know is thermometer. If you are among the non-divers, this info may be of some use when you decide to go diving.
The first time I encountered the word Thermocline was in the PADI Open Water course manual (that I have waded through diligently so that I can start my first Open Water course with Blue Season Bali). In simple English, a thermocline is a layer that separates colder water below from warmer water above. That term alone already fascinates me. I have known water for my whole life.. drinking it, bathing in it.. even our body is 70% water. Never would I have thought that it could come in two separate flavors in one container. How does this happen?
Here’s the theory .. (inhale) Ocean water is exposed directly to the sun. The heat makes the temperature on the surface warm. The lower part of ocean remains colder, since less sunlight reaches it. Cold water is denser than warm water, because its molecules are more tight (remember your physics lessons?), gravity keeps the layers separated so well, that the book says you can swim in the warmer layer of water, extend your hand below and feel the difference in temperature. (exhale.. very techie talk.. you okay there?)
In practice I heard that a thermocline isn’t really just a thin layer, but it actually can have thickness up to a few meter (as diagram above). I snorkeled once before, and to me sea water in itself is enough to make me shiver. With a thermocline, I can only imagine how cold it can be down there. So, if you have dived, and you know more about thermoclines, please share your experience by leaving some comments on this post. Stay tuned for other newbie friendly posts to add to your knowledge repository.