IELTS LISTENING-The Impact of Oceans on the World’s Climate S69T4
| IELTS listening The Impact of Oceans on the World’s Climate listening practice test has 10 questions belongs to the Environmental Science & Climate Studies subject.. |
You will hear a scientist talking about the effect that oceans have on the world’s climate. We’ve heard a lot about how increasing levels of atmospheric carbon dioxide will lead to a warmer world. However, there are some who believe, for Western Europe, the opposite may be true.
They suggest that global warming could lead to a weakening of the Gulf Stream and a considerable lowering of temperatures. But first, let’s remind ourselves what the Gulf Stream is, how it works, and what its effects are. Named after the Gulf of Mexico, it is a warm-water current, largely originating in the warm waters around Florida and the Caribbean, which travels to the northeast and the western shores of Europe. This is the reason locations such as the Isles of Scilly, off the UK coast, have frost-free winters, allowing palms to grow, in sharp contrast to the harsh winters on the same latitudes of the Atlantic’s west coast, such as New York and Boston.
As the waters of the Gulf Stream and its extension, the North Atlantic Drift, cool, they sink to depth and return south via the Labrador and Norwegian Seas. This is known as the Atlantic Meridional Overturning Circulation, commonly shortened to AMOC. Such circulation is largely driven by the Earth’s rotation, so is present in all the world’s oceans, including the Pacific, where places on the east coast of the ocean, such as Vancouver, have a comparable climate to those in Western Europe. However, it is believed the AMOC could weaken due to its increasing temperature and decreasing salinity and density, caused by the melting of the Arctic ice cap and the inflow of meltwaters, particularly from permafrost in the Siberian tundra, which could stop the surface flow of warm waters towards the north. There are a number of feedback loops which could intensify this warming.
First of all, as the Arctic ice sheets melt, less of the Sun’s radiation is reflected back into space, decreasing this cooling effect and increasing surface temperatures. The thawing of the permafrost of Siberia and Canada will flush even greater amounts of less dense freshwater into the Arctic area via rivers such as the Ob. Furthermore, this melting process will also release large amounts of methane previously trapped in the ice, which is a more powerful greenhouse gas than carbon dioxide, intensifying warming in another positive feedback loop. In fact, it is this massive freshwater input from ice melt, river flow and increased rainfall that could reduce the salinity of Arctic waters, greatly weakening the AMOC.
This process could weaken the entire North Atlantic circulation, either pushing the Gulf Stream and North Atlantic drift further south, reducing temperatures in Northwest Europe, or at its most extreme, resulting in the reversal of these flows and bringing freezing waters to these areas. However, others have suggested this is unlikely as they argue that it is the Earth’s rotation that chiefly powers the Gulf Stream and not the AMOC. Moving on, what has been the effect of global warming on the distribution of marine life, particularly plankton?
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