Sea ice covers an area of almost 16 million square kilometers of the Arctic seas during its maximum extent in winter. ⬛ Each summer the pack ice (Arctic ice cover)melts and shrinks in area,and,at a minimum,extends over about 9 million square kilometers. ⬛ The sea ice is an important part of the climate of the Arctic,and indeed of the whole world,because it has a large effect on the way the surface of the Arctic is heated. ⬛ Sea ice is highly reflective-we see this by the need to wear sunglasses when walking over snow or ice. ⬛ Water,on the other hand,appears rather dark by comparison.Where sea ice covers the Arctic seas,much radiation from the Sun is reflected back into the atmosphere.However,where open water is present,most of that radiation is absorbed and acts to heat the water.As the water heats up,more ice can be melted,and so on.This is called a positive feedback effect and is one of the key reasons why scientists are monitoring both the extent and the thickness of Arctic sea ice today.If sea ice covers a progressively smaller part of the Arctic seas in a world that may be affected by greenhouse gases,then this positive feedback could be critical to the rate at which our planet warms up.
1.The word"progressively"in the passage is closest in meaning to
2.In paragraph 1,why does the author compare the appearance of water to that of snow and ice?
A To illustrate how the sea ice cover affects surface heating
B To suggest that sea ice may melt more rapidly than some scientists have assumed
C To contrast the appearance of the Arctic in the winter with its appearance in the summer
D To support the point that sea ice covers a smaller area in the summer than it does in the winter
Another important aspect of the formation of sea ice is that when water freezes,a large proportion of its salt content is rejected (forced out into the surrounding water).Indeed,it is possible to melt old sea ice and drink the water.However,the seawater produced in areas where sea ice forms is both very cold and also of high salinity (salt content).The presence of so much salt produces some of the densest water found in the world's oceans,and this water sinks to ths seafloor as a result.In fact,the very dense waters produced by sea ice freezing in the Arctic are a vital factor in driving the circulation of the oceans,because these waters flow to the deepest parts of the ocean floor.Some areas of the Arctic seas are places of intense sea ice production,where upwelling (the movement of above-freezing water from the lower depths of the ocean to the surface)or strong winds consistently keep the sea open year-round.One example is the North Water at the head of Baffin Bay.New sea ice can,therefore, continue to form throughout the winter in such open-water areas, which are known as polynyas,from the Russian language.
3.Paragraph 2 provides which of the following explanations for the high salt content of Arctic waters?
O When water freezes,most of its salt is pushed out into the surrounding waters.
O Cold Arctic water sinks to the ocean floor,but most of its salt remains at the ocean surface.
O A large amount of salt is brought to the Arctic by the circulation of the oceans.
O Highly salty water moves to the Arctic because of upwelling.