G. Arctic warming may influence the global climate in several ways. One is that huge amounts of methane, a particularly potent greenhouse gas, are stored in the permafrost of the tundra. Although a thaw would allow forests to invade the tundra, which would tend to ameliorate any global warming that is going on , a melting of the permafrost might also lead to a lot of trapped methane being released into the atmosphere, more than offsetting the cooling effects of the new forests.
H. Another worry is that Arctic warming will influence ocean circulation in ways that are not fully understood. One link in the chain is the salinity of seawater, which is decreasing in the north Atlantic thanks to an increase in glacial melt waters. Because fresh water and salt water have different densities, this freshening of the ocean could change circulation patterns. said Dr. Thomson, a British climate expert. The most celebrated risk is to the mid-Atlantic Conveyor Belt, a current which brings warm water from the tropics to north-western Europe, and which is responsible for that regions unusually mild winters, he added. Some of the ACIAs experts are fretting over evidence of reduced density and salinity in waters near the Arctic that could adversely affect this current.
I. The biggest popular worry, though, is that melting Arctic ice could lead to a dramatic rise in sea level. Here, a few caveats are needed. For a start, much of the ice in the Arctic is floating in the sea already. Archimedess principle shows that the melting of this ice will make no immediate difference to the seas level, although it would change its albedo. Second, if land ice, such as that covering Greenland, does melt in large quantities, the process will take centuries. And third, although the experts are indeed worried that global warming might cause the oceans to rise, the main way they believe this will happen is by thermal expansion of the water itself.
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