Where do the Two Oceans meet?

There has always been controversy about the exact meeting point of the Atlantic and the Indian Ocean off the southern tip of Africa.

There is no particular place where the two oceans can be seen to meet in a line, but the coastline of the Western Cape is where they constantly mix and mingle, creating a wide variety of weather and sea life. The official southern most "Tip of Africa" is Cape Agulhas, 200km south east of Cape Point, see the "Map of the Western Cape & the "Map of South Africa" to see these areas in detail.

The South African coastline is more than 3'000km long, fringed by the Indian Ocean on the east and the Atlantic Ocean on the west coast.

Ocean Currents map The warm Agulhas Current (one of the most powerful in the world, moving at +/- 13km per hour), flows in a southerly direction down the east coast, bringing warm water down from the equatorial areas of the Indian Ocean. The cold Benguela current drifts broadly northwards up the west coast, bringing cold water up from the South Atlantic Ocean.

On the OCEAN TEMPERATURE map you can see the change in the ocean temperature - the Agulhas Retroflexion image shows the warm water red (25 °C) in colour and the cooler water green (16 °C) to light pink (12 °C). The warm Agulhas Current is steered by the continental shelf to approximately Cape Agulhas where, due to its speed and the earth spin, it begins to turn back on itself, either doing a u-turn and traveling back eastwards, or turning fully upon itself (in an anticlockwise direction) with an eddy being formed and breaking off drifting in a westerly direction. This eddy is known as the Agulhas Retroflexion, its position is not fixed, and often follows a cycle where it will occur south of Mossel Bay and then daily the position will move westwards, until it may be several hundred kilometres to the west of Cape Town. Then suddenly that whole section from Mossel Bay westwards will break off again and the current will retroflect again south of Mossel Bay.

On the west coast the warmer "pools / eddies" (indicated in green/yellow) are eddies of Agulhas water that have rounded Cape Point and are being carried northwards under the influence of the slow cold broad Benguela drift. These warm Agulhas eddies are very important to the maintenance of the South Atlantic heat budget, transporting heat from the Indian Ocean to the Atlantic, which has a heat imbalance, i.e. it loses more heat in the polar regions than it absorbs from the sun in the tropical regions.

Kommetjie_surfer_Hout_Bay_Chapmans_Peak_3_CapetourismThe Cape seawater is cold so surfers wear +5mm thick wetsuits to enjoy the water. Both coastlines have very powerful currents - due caution and care must be taken. The sea in False Bay in summer often reaches 22 °C (72 °F) due to the strong south easter wind blowing the warm Agulhas into False Bay. Whereas on the Atlantic beaches the same wind pulls the warm surface water away from the coast, and this is replaced by very cold water from great depths, usually 6 - 14 °C (45 - 57 °F - light pink area), also known as "upwelled" water, which is rich in nutrients and usually clear and blue.

The temperature contrast causes significant variations in the flora and fauna underwater. An outstanding feature of the icy Atlantic Ocean is the giant kelp forests (one of the fastest growing seaweeds) that can be seen along the rocky shorelines. It provides food and shelter to animals such as mussels, lobsters and perlemoen (abalone). While there are fewer species of fish and invertebrates on the West Coast, they occur in enormous numbers and this upwelled water temperature front zone supports a highly productive fishing industry. The fishing industry uses the "quota system" and needs to know the temperature of the sea on a daily basis, as fish are very temperature sensitive.Kalk_Bay_Yellow_Tail_fish_Capetourism

To see this daily change in sea temperature take a look at the satellite map of Africa to view the sea surface temperature image received by OSIS in Cape Town, scanned by the American NOAA14 Satellite.

Find out more about ocean currents and how they create our weather paterns - See RSMAS site:


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