Marine Biology

How Sea Corals Reveal changes to Oceanic Currents

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"How Sea Corals Reveal changes to Oceanic Currents"
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Something strange is happening in the world’s oceans and seas. Extreme weather is happening in many parts of the world. Whilst some people believe that climate change is caused by human activity, others dispute this, saying that climate change is part of the world’s natural cycles. Scientists previously used tree rings and ice cores to study climate change. These have both proved useful but can only give limited information.

No one, who has ever seen an underwater nature documentary, can doubt that corals are beautiful, and they support much sea life, but they are proving to be useful in telling scientists what is happening with the world. Coldwater corals reefs are composed from millions of stationary animals. They feed on plankton, tiny animals and plants, floating within the coral reef. When the seawater around them gets too warm, the corals reject the plankton, if the waters stay warm; the corals effectively starve and die. The cold and warm ocean currents are, therefore, extremely important to corals, and the fish and other animals that depend upon them.  A recent study by Swiss, American and Canadian researchers found that corals reveal much about climate change and the oceans.

The Gulf Stream is a warm current, 10 degrees warmer than the surrounding water, originating in the Gulf of Mexico. The Gulf Stream current follows the winds north along the Gulf, through the Florida Straits and up the east coast of the United States and Canada to Newfoundland where it turns towards Europe. In the middle of the Atlantic, the Gulf Stream splits into the North Atlantic Drift. This moderates the climate in Europe and the effects of the cool Canary current. The Gulf Stream is the reason why London’s climate is not the same as Moscow although both cities lay on virtually the same degree latitude.  The Cold Labrador Current 30 degrees F meets the Gulf Stream off Newfoundland. It flows from Greenland via Baffin Bay and then south. Salt water freezes at a much lower temperature than fresh. The Hudson Bay system feeds fresh water into the Labrador Current and so it freezes more quickly than the salty Gulf Stream, usually freezing during winter, breaking up in May to become ice free in July. The Labrador Current carries icebergs from Greenland’s glaciers, which melt. 

By studying, the corals at the point where the two currents meet scientists have determined that the influence of the Labrador Current has been continually decreasing since the 1970’s. This is happening simultaneously with climate change. This means that the sea is getting warmer and saltier.

Coral reefs are very old and have growth rings within them, a bit like trees. The scientists have determined that the decrease in the Labrador Current is unique in the last 2000 years. The team of biochemists and marine biologists found changes within the corals indicating a “drastic” shift since the 1970’s, the currents affect the North Atlantic weather patterns. Climate change in the North Atlantic was partly responsible for the collapse of the Grand Banks cod fishery. Rising seawater temperatures disrupt oceanic food chains and the entire marine eco-system.

Warming seawater in the Arctic certainly means more and larger icebergs, in 2010, a hundred square mile iceberg broke off Northern Greenland. An iceberg this large causes rising sea levels, which is another factor exacerbated by climate change. Oceans store heat. Temperature and salinity drives The Thermohaline Circulation or the Global Conveyor, which connects the World’s oceans, combines the ocean currents and is important to World weather patterns. It distributes warmth around the Earth. Warm water evaporates more quickly but as water flows north, it cools. Cold water is denser than warm water and just off Norway, gravity pulls the salty cold water to the ocean floor. An undercurrent then pushes the water south to rise again in the Indian Ocean and travel along the coast of Africa. Interruption of one ocean current affects them all, thus affecting the World’s weather. It could cause an ice age and that is why the recent coral research is vital, to tell what is happening.

In a separate study, scientists are researching into the fossilized sea corals near the Great Barrier Reef. This research and other similar studies may tell more about the oceans’ salinity and movement much further back in time and build upon the findings of the joint Swiss, American, Canadian study.

More about this author: Maria C Collins

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