Up­date on the Larsen-C ice­berg break­away

Weekend Mirror - - CHILDREN’S CORNER -

largest re­main­ing ice shelf on the Antarc­tic Penin­sula lost 10% of its area when an ice­berg four times the size of Lon­don broke free ear­lier this month.

Since the 12 July 2017 break­away Dr Anna Hogg, from the Univer­sity of Leeds and Dr Hil­mar Gud­munds­son, from the Bri­tish Antarc­tic Sur­vey (BAS), have con­tin­ued to track the ice­berg -- known as A68 -- us­ing the Euro­pean Space Agency (ESA) and Euro­pean Com­mis­sion’s Coper­ni­cus Sen­tinel-1 satel­lite.

Their ob­ser­va­tions show that since the calv­ing event, the berg has started to drift away from the Larsen- C, with open ocean clearly vis­i­ble in the ~ 5 kilo­me­tre gap be­tween the berg and the ice-shelf.

A clus­ter of over 11 ‘smaller’ ice­bergs have also now formed, the largest of which is over 13 km long. These ‘bergy bits’ have bro­ken off both the gi­ant ice­berg and the re­main­ing ice-shelf.

Dr Hogg, an ESA Re­search Fel­low in the Cen­tre for Po­lar Ob­ser­va­tion and Mod­el­ling (CPOM) at Leeds said: “The satel­lite images re­veal a lot of con­tin­u­ing ac­tion on Larsen-C Ice Shelf. We can see that the re­main­ing cracks con­tinue to grow to­wards a fea­ture called Baw­den Ice Rise, which pro­vides im­por­tant struc­tural sup­port for the re­main­ing ice shelf.

“If an ice shelf loses con­tact with the ice rise, ei­ther through sus­tained thin­ning or a large ice­berg calv­ing event, it can prompt a sig- nif­i­cant ac­cel­er­a­tion in ice speed, and pos­si­bly fur­ther desta­bil­i­sa­tion. It looks like the Larsen-C story might not be over yet.”

Re­port­ing this week in the jour­nal Na­ture Cli­mate Change Dr Hogg and Dr Gud­munds­son, ex­am­ine the events lead­ing up to this dra­matic nat­u­ral phe­nom­e­non and dis­cuss how calv­ing of huge ice­bergs af­fects the sta­bil­ity of Antarc­tic ice shelves.

Their ar­ti­cle as­serts that a calv­ing event is not nec­es­sar­ily due to changes in en­vi­ron­men­tal con­di­tions and may sim­ply re­flect the nat­u­ral growth and de­cay cy­cle of an ice shelf.

Dr Gud­munds­son said: “Al­though f l oat­ing i ce shelves have only a mod­est im­pact on of sea-level rise, ice from Antarc­tica’s in­te­rior can dis­charge into the ocean when they col­lapse. Con­se­quently we will see in­crease in the ice-sheet con­tri­bu­tion to global sea-level rise.

“With this large calv­ing event, and the avail­abil­ity of satel­lite tech­nol­ogy, we have a fan­tas­tic op­por­tu­nity to watch this nat­u­ral ex­per­i­ment un­fold­ing be­fore our eyes. We can ex­pect to learn a lot about how ice shelves break up and how the loss of a sec­tion of an ice shelf af­fects the flow of the re­main­ing parts.”

Ice-shelf re­treat on the Antarc­tic Penin­sula, has been ob­served through­out the satel­lite era -- about 50 years. Large sec­tions of the Larsen Ice Shelf A and B, and the Wilkins1 ice-shelf col­lapsed in a mat­ter of days in 1995, 2002, and 2008, re­spec­tively.

Ge­o­log­i­cal ev­i­dence sug­gests that ice- shelf de­cay of this mag­ni­tude is not un­prece­dented, how­ever, prior to 2002 the Larsen- B ice shelf re­mained in­tact for the last 11,000 years. While Antarc­tic ice shelves are in di­rect con­tact with both the at­mos­phere and the sur­round­ing oceans, and thus sub­ject to changes in en­vi­ron­men­tal con­di­tions, they also go through re­peated in­ter­nally-driven cy­cles of growth and col­lapse.

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