Antarc­tic ice melt­ing faster than ever, stud­ies show

The Guardian Australia - - Environment - Matthew Tay­lor

Ice in the Antarc­tic is melt­ing at a record-break­ing rate and the sub­se­quent sea rises could have cat­a­strophic con­se­quences for cities around the world, ac­cord­ing to two new stud­ies.

A re­port led by sci­en­tists in the UK and US found the rate of melt­ing from the Antarc­tic ice sheet has ac­cel­er­ated three­fold in the last five years and is now van­ish­ing faster than at any pre­vi­ously recorded time.

A sep­a­rate study warns that un­less ur­gent ac­tion is taken in the next decade the melt­ing ice could con­trib­ute more than 25cm to a to­tal global sea level rise of more than a me­tre by 2070.This could lead even­tu­ally to the col­lapse of the en­tire west Antarc­tic ice sheet, and around 3.5m of sea-level rise.

Prof An­drew Shep­herd, from Leeds Uni­ver­sity and a lead au­thor of the study on ac­cel­er­at­ing ice loss, said: “We have long sus­pected that changes in Earth’s cli­mate will af­fect the po­lar ice sheets. Thanks to our satel­lites our space agen­cies have launched, we can now track their ice losses and global sea level con­tri­bu­tion with con­fi­dence.”

He said the rate of melt­ing was “sur­pris­ing.”

“This has to be a cause for con­cern for the govern­ments we trust to pro­tect our coastal cities and com­mu­ni­ties,” Shep­herd added.

The study, pub­lished in Nature, in­volved 84 sci­en­tists from 44 in­ter­na­tional or­gan­i­sa­tions and claims to be the most com­pre­hen­sive ac­count of the Antarc­tic ice sheet to date. It shows that be­fore 2012, the Antarc­tic lost ice at a steady rate of 76bn tonnes per year - a 0.2mm per year con­tri­bu­tion to sea-level rise. How­ever since then there has been a sharp in­crease, re­sult­ing in the loss of 219bn tonnes of ice per year a 0.6mm per year sea-level con­tri­bu­tion.

The sec­ond study, also pub­lished in Nature, warns that time is run­ning out to save the Antarc­tic and its unique ecosys­tem - with po­ten­tially dire con­se­quences for the world.

The sci­en­tists as­sessed the prob­a­ble state of Antarc­tica in 2070 un­der two sce­nar­ios. The first in which ur­gent ac­tion on green­house gas emis­sions and en­vi­ron­men­tal pro­tec­tion is taken in the next few years, the sec­ond if emis­sions con­tinue to rise un­abated and the Antarc­tic is ex­ploited for its nat­u­ral re­sources.

The sce­nario which plays out largely de­pends on choices made over the next decade, on both cli­mate-change and on en­vi­ron­men­tal reg­u­la­tion, they con­clude.

Co-au­thor Profe Martin Siegert, from the Gran­tham In­sti­tute, said: “Some of the changes Antarc­tica will face are al­ready ir­re­versible, such as the loss of some ice shelves, but there is a lot we can pre­vent or re­verse.

“To avoid the worst im­pacts, we will need strong in­ter­na­tional co­op­er­a­tion and ef­fec­tive reg­u­la­tion backed by rig­or­ous science. This will rely on govern­ments recog­nis­ing that Antarc­tica is in­ti­mately cou­pled to the rest of the Earth sys­tem, and dam­age there will cause prob­lems ev­ery­where.”

As well as be­ing a ma­jor cause of sea-level rise, sci­en­tists say the oceans around Antarc­tica are a key “car­bon sink” - ab­sorb­ing huge amounts of green­house gases help­ing to mit­i­gate the im­pacts of cli­mate change.

Siegert said: “If the po­lit­i­cal land­scape of a fu­ture Antarc­tica is more con­cerned with ri­valry, and how each coun­try can get the most out of the con­ti­nent and its oceans, then all pro­tec­tions could be over­turned.

“How­ever, if we recog­nise the im­por­tance of Antarc­tica in the global en­vi­ron­ment, then there is the po­ten­tial for in­ter­na­tional co-oper­a­tion that uses ev­i­dence to en­act changes that avoid ‘tip­ping points’ – bound­aries that once crossed, would cause run­away change, such as the col­lapse of the west Antarc­tic ice sheet.”

Green­peace which is cam­paign­ing for a large tract of the ocean sur­round­ing the Antarc­tic to be made into the world’s big­gest ocean sanc­tu­ary, said gov­ern­ment’s must heed the warn­ing.

Louisa Cas­son, of Green­peace UK’s Pro­tect the Antarc­tic cam­paign, said: “Govern­ments can take a his­toric step for­ward in Oc­to­ber this year if they de­cide to cre­ate an Antarc­tic Ocean Sanc­tu­ary, pro­tect­ing 1.8 mil­lion square kilo­me­tres in what would be the largest pro­tected area on Earth.

“Ocean sanc­tu­ar­ies cre­ate havens for ma­rine life to build re­silience to a chang­ing ocean, but also cru­cially help us avoid the worst ef­fects of cli­mate change, by pre­serv­ing healthy ocean ecosys­tems that play a vi­tal role stor­ing car­bon.”

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