We will continue our comparative analysis of ecosystems by comparing ocean processes with those from other major ecosystem types. Oceans are much more than big pools of salt water. I. Ocean circulation is of the most important biogeophysical processes on Earth. As we saw in the beginning part of the course, ocean gyres created by the Coriolis effect are important for circulating warm tropical water to the poles and establishing global patterns of climate. However, ocean circulation is much more complicated than this simple 2-dimensional description suggests.
Oceans stratify just like lakes so that warm, light water sits on top of colder dense water.
However, unlike lakes where surface and bottom waters may mix during fall and spring turnover, oceans exhibit a specific pattern of mixing throughout the year that resembles a conveyer belt . This circulation pattern is called thermohaline circulation , and is caused by differences in temperature and salinity among surface water in the major oceans. We will see that this circulation pattern is extremely important in controlling the dynamics of carbon and nutrients. Here we see strong mixing of bomb materials into deep waters of the North Atlantic. Downwelling only occurs where surface water becomes as dense as the deep water.