首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Earth: Melting in the Heat? Glaciers are melting; the ice caps are disappearing into the oceans; sea levels may rise by man
Earth: Melting in the Heat? Glaciers are melting; the ice caps are disappearing into the oceans; sea levels may rise by man
admin
2010-09-25
22
问题
Earth: Melting in the Heat?
Glaciers are melting; the ice caps are disappearing into the oceans; sea levels may rise by many meters as a consequence. Indigenous (本土的) Arctic peoples will find their food stocks gone, while fresh water supplies in Asia and south America will disappear as the glaciers which provide them melt away; penguins, polar bears and seals will find their habitats gone, their traditional lives unlivable.
But how realistic is this picture? Is the world’s ice really disappearing, or is it unscientific hot air?
A European satellite named Cryosat was designed to provide definitive answers to some of these questions. A launcher fault destroyed the mission in October 2005, but the European Space Agency has approved a replacement. In the meantime, here is our global snapshot.
The Antarctic
Huge, pristine (质朴的), dramatic, unforgiving-the Antarctic is where the biggest of all global changes could begin.
There is so much ice here that if it all melted, sea levels globally would rise hugely—perhaps as much as 80m. Say goodbye to London, New York, Sydney, Bangkok … in fact, the majority of the world’s major cities.
But will it happen? Scientists divide the Antarctic into three zones: the east and west Antarctic ice sheets; and the Peninsula, the tongue of land which points up towards the southern tip of South America.
"Everybody thinks that the Antarctic is shrinking due to climate change, but the reality is much more complex," says David Vaughan, a principal investigator at the British Antarctic Survey in Cambridge, U.K. "Parts of it appear to be thickening as a result of snowfall increases, but the Peninsula is thinning at an alarming rate due to warming. The West Antarctic sheet is also thinning, and we’re not sure of the mason why."
On the Up
Temperatures in the Peninsula appear to be increasing at around twice the global average—about 2℃ over the last 50 years. Those figures are based on measurements made by instruments at scientific stations.
Earlier this year, David Vaughan’s group published research showing that the vast majority of glaciers along the Peninsula—87% of the 244 studied—are in retreat. The ice dumped into the ocean as the glaciers retreat should not make much difference to global sea levels—perhaps a few centimeters.
More worrying, potentially, are the vast ice sheets covering the rest of Antarctica. Making temperature measurements for the continent as a whole is difficult; it is a vast place--more than 2,000 km across--them are few research stations, and temperatures vary naturally by 2~3℃ from year to year. But measurements indicate that in the west, reciting is underway.
"About one-third of the West Antarctic ice sheet is thinning," says Dr. Vaughan, "on average by about 10cm per year, but in the worst places by 3~4m per year."
The rock on which the West Antarctic ice rests is below sea level, and British Antarctic Survey researchers believe the thinning could be due to the ice sheet melting on its underside.
"It may be that the ocean is warming and that’s causing the ice to melt, but there may be other reasons as well; for example, there’s lots of volcanism in that area and so that could change how much heat is delivered to the underside of the ice sheet."
Cryosat should help to pin down what is happening at the West Antarctic fringe. The radar altimeters on board its predecessors ERSI and ERS2 have been unable to map the steep slopes at the coast, whereas Cryosat’s instrument should be able to cope.
If the entire West Antarctic ice sheet did melt, sea levels globally would rise, by around 5m. But at the moment, there is no sign of that happening.
One recent scientific paper attempted to calculate probabilities for how much West Antarctic melting would contribute to global sea-level rises during this century. The conclusions: a 30% probability of a 20 cm rise, and a 5% chance of a 1m rise.
Eastern Mass
And what of the big monster, the much larger East Antarctic sheet? A recent study using altimeter data suggested it is getting thicker, by about 1.8 cm/yr; another, using the gravity satellite mission Grace indicates its mass remains stable. But could rising temperatures in time drain the ice away?
"It is net going to happen on any realistic human timescale," says David Vaughan. "It’s so cold that you could raise temperatures by 5~10℃ without having much of an impact; it’s on rock above sea level, so warming in the ocean can’t affect it."
Largely insulated from global trends and so big as to generate its own climatic systems, most of Antarctica appears to be immune to the big melt for now, though answers to what is happening in the west are eagerly awaited.
The Arctic
At the top of the world, the Arctic is a region built on water. Around the Noah Pole is ocean, with ice floes crowding in each winter and thinning again in the summers.
In September, we learned from scientists at the U.S. National Snow and Ice Data Center that the extent of ocean covered by ice is getting smaller each year, the current rate of shrinkage they calculate at around 8% per decade. Their projection is that within about 60 years, there will be no summer ice at all on the Arctic Ocean.
"Overall, the extent has been declining, with some oscillations (摆动), since the 1970s when satellites were able to map it," comments Peter Wadhams, Professor of Ocean Physics at Cambridge University, U.K., and currently at the Laboratoire Oce anographique in Villefranche-sur-mer, France. "There’s been a slow decline, but now the thinning appears to be more rapid. In the last two decades, not only has the area shrunk but the ice has got thinner by about 40%; the prediction is that it will vanish altogether during summers in the second half of this century."
Military Records
Measurements of thickness come mainly from military submarines, which spent long periods under the Arctic ice during the Cold War.
Peter Wadhams was one of the scientists who afterwards persuaded the authorities in Britain and the United States to declassify their data.
But as a method of measurement, it is far from perfect; and satellites have given only limited help. The existing satellite fleet gives good measurements of ice extent, but is not so good at detecting thickness, partly because the orbits of satellites with radar altimeters do not cover every portion of the ocean.
This data deficit has led to a rival theory—that the ice is not melting at ail; it is simply piling up in another part of the ocean, perhaps along the north Canadian coast.
Peter Wadhams believes he has now disproved this idea. "We did an experiment where we installed a set of buoys (浮标) in that region which measure the thickness of the ice and transmit it back via satellite," he says. "The buoy sits on the ice, and as waves pass under it they make it rise and fall, just by a millimeter or two; measuring this allows you to calculate the thickness of the ice."
The preliminary results, announced at a scientific meeting in April 2005, show that the extra ice is not there; it really has melted away.
Wider Impact
To people living, in the region, the melting brings mixed news. Current lifestyles and staple foods will almost certainly change, but the open ocean may permit new opportunities for trade and agriculture.
A bigger question is what it means for the rest of the planet. Ice reflects the sun’s radiation; water absorbs it. More water and less ice—a lower albedo (反照率)—mean that the pace of warming could increase. In this scenario, the Earth would be losing one of its "natural checks and balances" against warming—another positive feedback mechanism.
The Arctic is intimately tied to the global climate system, and disruptions here have the potential to create worldwide changes—albeit (虽然) over long timescales. Possibly the most powerful link is via the thermohaline (热盐的) circulation, the global conveyor taking warm water along ocean surfaces and returning colder water at depth.
"One very sensitive place is the middle of the Greenland Sea," says Peter Wadhams. "That has been ice-free in the summer, but usually in winter it would be covered by a lobe of ice growing out from the Greenland coast. AS it formed, it rejected salt back into the water, making the water heavier and helping it to sink. Since 1997, the ice tongue has never termed. That will be having an impact on the thermohaline circulation."
Back in geological history, about 55 million years ago, the Arctic was a warm (possibly 20~C) shallow sea that would have been ice-free without the intervention of a human-enhanced greenhouse effect.
Natural variations may be playing a role in the picture seen now; hut, as with other parts of the planet, it is the speed of change that alarms many researchers as much as the change itself.
Fresh water supplies in Asia and south America is disappearing as the glaciers melt away.
选项
A、Y
B、N
C、NG
答案
C
解析
根据题干中的信息词fresh water supplies和glaciers定位到原文第一段,可知北极当地人将发现自己的食物储备不见了,而亚洲和南美洲的淡水供应也将随着提供淡水的冰川的融化而消失,再结合下文可知,这只是一种假设,而原文并没有对该假设给出具体解释。
转载请注明原文地址:https://jikaoti.com/ti/1teFFFFM
0
大学英语六级
相关试题推荐
Whileitcan’tyetbesaidthateverymouthfuloffoodhasbeenchangedthroughgeneticengineering,itislikelythatalmostev
Whileitcan’tyetbesaidthateverymouthfuloffoodhasbeenchangedthroughgeneticengineering,itislikelythatalmostev
Noonereallythrivesinawhollyinstitutionalized(制度化的)environmentorinapurelyintellectualcareer.Thistruthmighthave
Noonereallythrivesinawhollyinstitutionalized(制度化的)environmentorinapurelyintellectualcareer.Thistruthmighthave
Noonereallythrivesinawhollyinstitutionalized(制度化的)environmentorinapurelyintellectualcareer.Thistruthmighthave
A、Hisschoolmates.B、Peopleofdifferentages.C、Peopleinthehallofresidence.D、Hisfriendsattheuniversity.C
Itisdifficulttoimaginewhatlifewouldbelikewithoutmemory.Themeaningsofthousandofeverydayperceptions,
WorldPopulationGrowthandDistributionTheUnitedNations,anacceptedauthorityonpopulationlevelsandtrends,estimate
Thousandsofteachersattheelementary,secondary,andcollegelevelscantestifythattheirstudents’writingexhibitsatende
Earth:MeltingintheHeat?Glaciersaremelting;theicecapsaredisappearingintotheoceans;sealevelsmayrisebymany
随机试题
属于C类的抗心律失常的药物是()。
曹某因诈骗罪被公安机关立案侦查后移送人民检察院审查起诉,人民检察院审查后认为曹某没有作案时间。对此,下列表述中正确的是()
股票或债券上市交易的公司,应当在每一会计年度的上半年结束之日起()个月内,向国家证券监督管理机构和证券交易所提交中期报告。
甲公司向乙公司转让其软件的使用权,期限为10年,一次性收取使用费100000元,双方达成协议,甲公司在未来10年内需提供与该软件使用权相关的后续服务,款项已经收回。假定不考虑相关税费,则甲公司本期应确认的使用费收入为()元。
某玻璃制品厂是增值税一般纳税人,2012年6月采购材料取得的增值税专用发票上注明增值税12万元,其中20%的原材料用于不动产修缮;当月销售产品取得不含增值税销售额100万元;初次购买增值税税控系统专用设备,取得增值税专用发票,不含税价款0.8万元;支付技术
一词当然可以多义,但一词的多义应当是相近的。例如,“帅”可以解释为“元帅”,也可以解释为“杰出”,这两个含义是相近的。由此看来,把“酷(cool)”解释为“帅”实在是英语中的一种误用,应当加以纠正,因为“酷”在英语中的初始含义是“凉爽”,和“帅”丝毫不相及
ARM处理器在大端模式下从0x60000000到0x60000003存储一个字数据0x32303134,R2=0x60000000,以下说法正确的是()。
开发大型软件时,产生困难的根本原因是()。
Eventhoughthesurveywasdesignatedasaninter-disciplinarycourse,itinvolvednoreal______ofsubjectmatter.
Hotmetalshrinksasitbecomescool.
最新回复
(
0
)