On our second day in the Lakes Region, we saved the Sunday to see the beauties of the area, called ‘Brazilian diving capital’. We went out with the guys from Personal Dive to Ilha dos Porcos and Saco do Cardeiro, famous diving spots in Arraial do Cabo. The day was sunny and hot, but the water was close to sixteen degrees celsius, much like on our Saturday dive. The people who dive in this area is prepared to face the cold waters here, but why is the water temperature in Arraial do Cabo and Cabo Frio so low?
The marine waters in Cabo Frio and Arraial do Cabo are famous for being clear and crystalline, for having a very rich and diverse marine life and for presenting many diving spots, but there is also a unique characteristic to these waters: they present temperatures much lower than the rest of the Brazilian southeastern coast. What makes these waters so cold?
The answer is it is the result of the oceanographic phenomena called UPWELLING, characterized by the motion of deep waters towards the surface in specific areas of the oceans, waters which are cold and rich in nutrients. It is a phenomena more common on the west borders of continents, but on the Brazilian coast it occurs in a few specific spots, the most well known one being in Arraial do Cabo, on the east of the Rio de Janeiro state. In this area, the upwelling happens as a result of the dominant wind’s motion in the upper right quadrant combined with the Earth’s rotation, which provokes the distancing of the warm waters of the Brazil Current that descends along the northeastern coast towards the south. When these waters distance themselves from the coast, there is an upwards motion of the cold waters of the Malvinas Current, which runs in the opposite direction to the Brazil Current, moving from the south towards the northeast.
One of the characteristics of upwelling is that it generates high primary productivity, which in consequence benefits the entire food chain, making these areas very important for the fishing industry. The nutrients present in these waters that rise to the surface, when reaching the illuminated layers of water, are used by the microscopic algae which, through the process of photosynthesis, generate an “explosion” of microalgae (phytoplanktons), these being the start of the marine food chain. These phytoplanktons are food for small marine organisms (zooplanktons) which in its turn will serve as food for small fish that will feed bigger fish and so forth. For this reason, Arraial do Cabo and Cabo Frio are very rich in fishery. The central area of the upwelling is in Praia do Focinho in Ilha de Cabo Frio, more commonly known as Ilha do Farol.
When the predominant winds change with the arrival of a cold front, the opposite phenomena occurs, called DOWNWELLING, which here is the downward motion of the cold waters of the Malvinas Current and the return of the warm waters of the Brazil Current. Since in Cabo Frio and Arraial do Cabo the predominant winds are those of the upper right quadrant, the most frequent situation here is the upwelling.
In other words, a semi-dry wetsuit, boots and gloves – and some hot chocolate – help in enjoying everything even more and not letting the cold waters be a reason not to dive.