An omi­nous oc­cur­rence in Antarc­tica

The Denver Post - - PERSPECTIVE - By Tim Ly­don

For­get for a minute that Pres­i­dent Don­ald Trump re­cently pulled us out of the Paris Cli­mate Ac­cord. Or that a bur­geon­ing list of cor­po­ra­tions and lo­cal gov­ern­ments are pro­ceed­ing with the agree­ment’s goals any­way, in­clud­ing Colorado, which this month be­came the fourth Western state to for­mally re­ject Trump’s move. In­stead, look at what just hap­pened in Antarc­tica.

On July 12, af­ter months of an­tic­i­pa­tion, one of the largest ice­bergs ever ob­served sheered away from the Larsen C Ice Shelf on the West Antarc­tica Penin­sula. The thing is over 2,000 square miles in size and nearly a quar­ter-mile deep in places. It’s the size of Glacier Na­tional Park, or the state of Delaware.

The first thing to ac­knowl­edge is sci­en­tists do not agree whether cli­mate change prompted the ice­berg’s re­lease. The dis­charge of some­times mas­sive bergs nat­u­rally oc­curs on Antarc­tica ice shelves, and signs of the even­tu­ally 120-mile fis­sure that pro­duced the berg were ob­served as early as the 1960s.

Nev­er­the­less, the event puts on dis­play the type of process cli­mate change can trig­ger. And it fore­shad­ows what sci­en­tists omi­nously warn will oc­cur in Antarc­tica if hu­man­ity does not quickly curb fos­sil fuel emis­sions.

It all has to do with the way Larsen C broke off, more than its im­pres­sive size. Peel­ing away from two bedrock an­chor points over 100 miles apart, sci­en­tists say it may have desta­bi­lized the en­tire Larsen C Ice Shelf, fourth-largest in Antarc­tica.

No one knows how long the ice shelf would take to break up, and it could take many years. On the other hand, Larsen B shat­tered like a gi­ant glass plate in just one month, star­tling Antarc­tica ob­servers be­cause it had been sta­ble for mil­len­nia.

Im­por­tantly, dis­in­te­gra­tion of the Larsen C would add vir­tu­ally noth­ing to global sea level rise, as its en­tire mass is al­ready afloat on the ocean. But ice shelves act like dams, hold­ing back some­times enor­mous land­based glaciers. If Larsen C goes, cur­rently sta­ble glaciers will be­gin pour­ing into the ocean. That new freshet would in­crease sea-level rise, which Euro­pean re­searchers re­cently showed tripled since 1990.

A re­lated process al­ready hap­pens across Alaska and Green­land. It’s easy to think of glaciers as sim­ply melt­ing be­cause tem­per­a­tures are ris­ing. And that’s cer­tainly hap­pen­ing. But glaciers ter­mi­nat­ing in oceans have an added vul­ner­a­bil­ity of cat­a­strophic col­lapse, which oc­curs when they be­come un­hinged from their an­chors. Whether it’s a pinch-point be­tween moun­tains or a bit of shal­low ocean floor, once a glacier loses its grip, it can quickly break apart, redefin­ing the no­tion of “glacial speed.”

In Alaska, we’ve watched this for years. Warm­ing likely nudged the Co­lum­bia Glacier in Prince Wil­liam Sound, the South Sawyer Glacier south of Juneau, and oth­ers from pre­vi­ously sta­ble po­si­tions, prompt­ing retreats so rapid that lo­cal maps quickly be­came ob­so­lete. The on­go­ing melt­ing adds to ris­ing seas.

A long-sim­mer­ing con­cern is that the same will be­gin hap­pen­ing in Antarc­tica, un­rav­el­ing its mas­sive store of ice and tip­ping pro­jec­tions of global sea-level rise to­ward worst-case sce­nar­ios. So in the wake of the gi­ant Larsen C berg, it’s worth not­ing two nearby ice shelves dis­ap­peared in the last two decades, and a third is now in po­ten­tial jeop­ardy. The pro­gres­sion has been south­ward, to­ward the con­ti­nent’s main body of ice. Even as cli­mate is not clearly im­pli­cated, it presents a warn­ing.

Al­ready, peo­ple are squeezed by sea-level rise. It con­trib­utes to the de­struc­tion of homes, roads and in­fra­struc­ture in sev­eral Alaska vil­lages, where U.S. cit­i­zens are los­ing liveli­hoods and cul­tural tra­di­tions and im­mi­nently ap­proach­ing cli­mate refugee sta­tus. Mean­while, the West’s low-ly­ing coastal cities are tak­ing stock of dam­age in Alaska. From San Diego to Seattle, mu­nic­i­pal­i­ties map where seas are pro­jected to in­un­date streets, wet­lands and neigh­bor­hoods in the years ahead. Re­gard­less of cli­mate’s role, un­fold­ing events in Antarc­tica will fur­ther in­form their work.

Science shows we are al­ready locked into some de­gree of cli­mate warm­ing and ris­ing seas in the years ahead. The ac­cel­er­a­tive ef­fect from Antarc­tica is yet uncer­tain. Nev­er­the­less, science shows global co­op­er­a­tion to­ward swift cuts to coal and oil can re­duce sur­face melt­ing of ice across the planet, eas­ing us back from worst-case sce­nar­ios. That must be why hun­dreds of U.S. cor­po­ra­tions and com­mu­ni­ties are scram­bling to sup­port the Paris Agree­ment.

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