Antarc­tic ice’s in­sta­bil­ity con­cerns sci­en­tists

Honolulu Star-Advertiser - - WORLD - By Justin Gil­lis

ABOVE THE ROSS SEA, ANTARC­TICA >> En­gines droned as a mil­i­tary cargo plane sliced through the frigid air, mak­ing straight for the world’s largest chunk of float­ing ice.

In the belly of the plane, an en­gi­neer with a shock of white hair di­rected younger sci­en­tists as they threw switches. Grav­ity me­ters jumped to life. Radar pulses and laser beams fired to­ward the ice. On com­puter screens, in ghostly traces of data, the sur­face of the Ross Ice Shelf be­gan to yield se­crets hid­ing be­neath. Antarc­tica, an im­mense, frozen land, is hid­ing many of them. And some sci­en­tists are start­ing to think that noth­ing less than the fate of hu­man civ­i­liza­tion could hang on un­rav­el­ing those mys­ter­ies.

Many peo­ple re­gard Antarc­tica as un­chang­ing. But the ice moves from the land to the sea, bil­lions of tons ev­ery year, and has done so for eons. To­day the ice in parts of Antarc­tica seems to be ac­cel­er­at­ing. Some glaciers have been desta­bi­lized by warmer ocean wa­ters. Sci­en­tists fear that parts of the ice sheet may be in the early stages of an un­stop­pable dis­in­te­gra­tion. Be­cause the breakup of parts of the ice sheet could raise the sea level by many feet, the con­tin­ued ex­is­tence of vul­ner­a­ble ci­ties near the world’s coast­lines could de­pend on what hap­pens here. “We’re 9,000 miles from New York,” said the white­haired en­gi­neer, Ni­cholas Frear­son, a leader of a Columbia Univer­sity team that was study­ing Antarc­tica late last year. “But we are con­nected by the ocean.”

A rapid de­te­ri­o­ra­tion of Antarc­tica might, in the worst case, cause the sea to rise so fast that tens of mil­lions of coastal refugees would have to flee in­land, po­ten­tially strain­ing so­ci­eties to the break­ing point. Cli­mate sci­en­tists once re­garded that sce­nario as fit only for dis­as­ter films. Now they can­not rule it out. Yet as they try to de­ter­mine how se­ri­ous the sit­u­a­tion is, they con­front a frus­trat­ing lack of in­for­ma­tion.

Re­cent com­puter fore­casts sug­gest that if green­house emis­sions con­tinue at a high level, parts of Antarc­tica could break up rapidly, caus­ing the sea to rise 6 feet or more by the end of this cen­tury — twice the max­i­mum in­crease that an in­ter­na­tional cli­mate panel pro­jected four years ago. But the com­puter fore­casts were deemed crude even by the re­searchers who cre­ated them. “We could be decades too fast or decades too slow,” said one, Robert M. DeConto of the Univer­sity of Mas­sachusetts, Amherst. Alarmed by signs that parts of the ice sheet are desta­bi­liz­ing, the Na­tional Science Foun­da­tion in Wash­ing­ton and the Nat­u­ral En­vi­ron­ment Re­search Coun­cil in Bri­tain are join­ing forces to get bet­ter mea­sure­ments in the main trou­ble spots. The ef­fort could cost over $25 mil­lion and take years to yield clearer an­swers about the fate of the ice.

It is a race against time to pro­duce clearer fore­casts about the con­se­quences of emis­sions. Columbia sci­en­tists have spent the past two Antarc­tic sum­mers fly­ing over the Ross Ice Shelf, which helps to slow the flow of land ice into the sea. Com­puter fore­casts sug­gest that it may be vul­ner­a­ble to col­lapse in the next few decades. The project to map the shelf’s struc­ture and depth, funded by tax­pay­ers through the Na­tional Science Foun­da­tion, puts Columbia and its part­ner in­sti­tu­tions on the front lines of one of the world’s most ur­gent sci­en­tific and po­lit­i­cal prob­lems. Re­mote as Antarc­tica might seem, every­one who gets in a car, eats a steak or boards a plane con­trib­utes to emis­sions that put the con­ti­nent at risk. If those emis­sions go unchecked and the world is al­lowed to heat up enough, sci­en­tists have no doubt that large parts of Antarc­tica will melt into the sea.

But they do not know the trig­ger tem­per­a­ture, or whether the ac­cel­er­a­tion of the ice means that Earth has al­ready reached it. The ques­tion, said Richard B. Al­ley, a sci­en­tist at Penn­syl­va­nia State Univer­sity, is eas­ier to ask than to an­swer: “How hot is too hot?”

Loom­ing floods

More than 60 per­cent of the fresh wa­ter on Earth is locked up in Antarc­tica’s ice sheets. The risk is clear: Even a par­tial col­lapse of the ice has the po­ten­tial to in­un­date coastal ci­ties across the globe.

The ice has been build­ing up for tens of mil­lions of years. Thin lay­ers of snow fall­ing were grad­u­ally pressed into ice, bury­ing moun­tain ranges and build­ing an ice sheet more than 2 miles thick. Un­der its own weight, that ice flows down­hill in slow-mov­ing streams that even­tu­ally drop icebergs into the sea.

If the ice sheet were to dis­in­te­grate, it could raise the sea level by more than 160 feet — a po­ten­tial apoc­a­lypse, de­pend­ing on how fast it hap­pened. Re­search sug­gests that if so­ci­ety burns all the fos­sil fu­els known to ex­ist, the col­lapse of the ice sheet will be in­evitable. Im­prob­a­ble as such a large rise might sound, some­thing sim­i­lar may have al­ready hap­pened, and re­cently enough to be lodged in col­lec­tive mem­ory. In the 19th cen­tury, ethno­g­ra­phers re­al­ized that vir­tu­ally ev­ery old civ­i­liza­tion had some kind of flood myth.

In the Epic of Gil­gamesh, wa­ters so over­whelm the mor­tals that the gods grow fright­ened, too. In In­dia’s ver­sion, Lord Vishnu warns a man to take refuge in a boat, car­ry­ing seeds. In the Bi­ble, God or­ders Noah to carry two of ev­ery liv­ing crea­ture on his ark.

“I don’t think the bib­li­cal del­uge is just a fairy tale,” said Ter­ence J. Hughes, a re­tired glaciol­o­gist. “I think some kind of ma­jor flood hap­pened all over the world, and it left an in­deli­ble im­print on the col­lec­tive mem­ory of mankind that got pre­served in these sto­ries.” That flood­ing would have oc­curred at the end of the last ice age. Ice ages oc­cur when wob­bles in Earth’s or­bit change the dis­tri­bu­tion of sun­light, al­low­ing huge ice sheets to build up. At the peak of the last ice age, about 50,000 years ago, the ice sheets grew so large and locked up so much wa­ter that the sea level fell by an es­ti­mated 400 feet. Per­haps 25,000 years ago, the ice sheets be­gan to melt, and the sea level be­gan to rise. Over sev­eral thou­sand years, coast­lines re­ceded in­land by as much as 100 miles.

Hu­man civ­i­liza­tion did not yet ex­ist, but early so­ci­eties of hunters and gath­er­ers liv­ing along the world’s shore­lines would have watched the in­un­da­tion claim their lands.

Rem­nants of that ice age re­main. A lit­tle bit of ice still clings to moun­tains, but the main sur­vivors are the two great ice sheets cov­er­ing Green­land and Antarc­tica. Sci­en­tists once thought that fur­ther de­struc­tion of those ice sheets was likely to take thou­sands of years. But, start­ing in the 1970s, some warned that the ice sheets could be vul­ner­a­ble much sooner if green­house emis­sions were not checked.

NEW YORK TIMES

Sci­en­tists are rac­ing to un­der­stand what is hap­pen­ing to the ice shelf as the planet warms around it. A mul­ti­ple-mile-long ice­berg broke off of the Ross Ice Shelf and be­came grounded in McMurdo Sound in Antarc­tica.

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