In 2012, the Bri­tish Ant­ar­c­tic Sur­vey had built an ultra-modern rese­arch sta­ti­on, on the eas­tern side of the Wed­dell sea: Hal­ley
VI. The five pre­vious sta­ti­ons were eit­her cover­ed in snow or not safe to use any­mo­re. Simi­lar to the Ger­man rese­arch sta­ti­on­Neu­may­er III, whe­re rese­ar­chers moved in for the first time in 2009, Hal­ley VI is situa­ted on the shelf ice. Alre­a­dy Neu­may­er III was per­fect­ly con­s­truc­ted for the pre­vai­ling con­di­ti­ons. It should be able to with­stand the local­ly strong winds and drif­ting snow should not accu­mu­la­te to the buil­dings. Sin­ce ice is moving, shear forces would act on the con­s­truc­tion, too. Fore the­se reasons the buil­ding was erec­ted on hydrau­lic legs, which gra­du­al­ly could lift it to the level of the cur­rent snow lay­er. Howe­ver, the Ger­man base is fixed to the ice below. At the pre­sent loca­ti­on the sta­ti­on is drif­ting to the shelf ice edge
with a speed of 157 met­res per year. The Bri­tish impro­ved their new con­s­truc­tion, and in Febru­ary 2012, a modu­lar buil­ding on ski was rea­dy to move in on the Brunt ice shelf. It can also be lifted hydrau­li­cal­ly. Each year, 1.5 met­res of snow accu­mu­la­te due to eit­her snow fall or snow drift. The appro­xi­m­ate­ly 150 met­re thick ice shelf below Hal­ley VI moves with a speed of more than 400 meters per year. To pre­vent the loss of the base over the years, hea­vy vehic­les are able to move the indi­vi­du­al modu­les on their ski from its loca­ti­on.

When Hal­ley VI was used for the first time in 2012, seve­ral chasms in the shelf ice South of the sta­ti­on were alre­a­dy known. Almost one year later, after 35 years of inac­ti­vi­ty, the chasms star­ted to grow again. The crack clo­sest to the sta­ti­on increased by appro­xi­m­ate­ly 1.7 kilo­me­t­res per year. Last Octo­ber, rese­ar­chers detec­ted a new fis­su­re in the North. They worried about the sta­ti­on to be cut off from the main­land. The­r­e­fo­re, BAS deci­ded for the relo­ca­ti­on of the Hal­ley VI, and the sta­ti­on would not be available for rese­arch for 3 years. Within that time, the trans­fer of the buil­dings should be
com­ple­ted. During the Ant­ar­c­tic sum­mer of 2015/16 sci­en­tists sur­vey­ed the area for a new loca­ti­on and a safe rou­te for trans­port. It is about 23 kilo­me­t­res fur­ther inland. Camps for fieldwor­kers and engi­neers will be build and the first modu­les are get­ting on the road during the cur­rent sum­mer. The rese­ar­chers hope that the base will be rea­dy for work for the 2017 sum­mer team. The sup­p­ly rou­te over the shelf-ice edge would then be exten­ded to 40 kilo­me­t­res. Bet­ter safe than sor­ry!

In the begin­ning of Janu­ary, Bri­tish rese­ar­chers noti­fied on the cur­rent situa­ti­on of the Lar­sen C Ice Shelf. This ice shelf is loca­ted on the East side of the Ant­ar­c­tic Pen­in­su­la. A well known and obser­ved crack has grown quick­ly lar­ger during 2016. The Ger­man Alfred Wege­ner Insti­tu­te repor­ted about that topic during the last few months on its Ice Blog. Bet­ween May and August 2016 the sci­en­tists obser­ved an exten­si­on of a crack by 25 km. In Decem­ber this crack expan­ded ano­ther 18 km. The ante­rior part of the Ice Shelf is now only con­nec­ted to the remai­ning Shelf by a 20 km wide “bridge”.

The Bri­tish Ant­ar­c­tic Sur­vey experts sup­po­se a pos­si­ble break-off sce­na­rio of the appro­xi­m­ate­ly 50,000 km² shelf ice area alre­a­dy later this year. In recent years, rese­ar­chers have given spe­cial atten­ti­on to the “Lar­sen C” ice shelf. The ear­lier col­lap­ses of the Lar­sen A (1995) and Lar­sen B (2002) Ice Shel­ves had cle­ar­ly shown one effect: The floa­ting ice acts as a bar­ri­er and slows down land based gla­ciers behind. The loss of such a bar­ri­er results in the acce­le­ra­ti­on of gla­ciers behind it. Lar­sen C covers an area about 15 times lar­ger than the 2002 lost ice of Lar­sen B. Thus it also holds back lar­ger gla­ciers mas­ses. Two ques­ti­ons are inte­res­t­ing in that con­text: What cau­ses the break-off of the ice shelf? And what are the con­se­quen­ces of the ice loss?

Sci­en­tists have gai­ned a lot of new know­ledge about the under­lay­ing pro­ces­ses of the loss of shelf ice during the last years. The col­lap­se of Lar­sen B was most likely the result of the increased annu­al tem­pe­ra­tures on the pen­in­su­la over the past 50 years. During that peri­od of time the rese­ar­chers have shown an avera­ge increase of 2.5 degrees. As a con­se­quence of the warm­ing, the snow lay­er and the firn lay­er on the ice shelf vanis­hed more rapidly during sum­mer. Thus melt water ponds evol­ved more fre­quent­ly. The­se lakes fro­ze during win­ter. Ice of this ori­gin is war­mer and sof­ter than the sur­roun­ding ice, which has been for­med by the trans­for­ma­ti­on of snow to firn to gla­cier ice. The melt water zones in the gla­cial ice chan­ge the struc­tu­re of the enti­re ice shelf. The fol­lo­wing sum­mer the­se zones will start to melt ear­lier. This effect cau­sed the sud­den col­lap­se in Lar­sen B in 2002.

For the detach­ment of Lar­sen C this effect is not the only reason. The results of the BAS stu­dies show a decli­ning firn lay­er and a decre­asing thic­k­ness of the snow lay­er, due to an increased annu­al air tem­pe­ra­tu­re of the area. Fur­ther ice loss occurs at the bot­tom of the ice shelf by war­mer water curr­ents. The warm­ing of the earth’s atmo­sphe­re and the Ant­ar­c­tic ozone hole streng­then the West wind curr­ents and thus the cir­cum­po­lar cur­rent. This gives enough ener­gy to swa­sh up war­mer and sal­tier water mas­ses from the oce­an depths to the con­ti­nen­tal shelf. The sci­en­tists cal­cu­la­ted the thin­ning of the ice to 4 meters, in the peri­od of 1998 and 2012.

What would be the con­se­quen­ces, when Lar­sen C will dis­ap­pear? The shelf ice its­elf has no impact on the sea-level, sin­ce shelf ice is floa­ting ice. Howe­ver, the­re would not be any other bar­ri­er for the land based gla­ciers behind. They will increase their speed. In the case of Lar­sen B the sur­roun­ding land based gla­ciers acce­le­ra­ted five times their pre­vious velo­ci­ty. The­se gla­ciers lost a lot of ice, cra­cked, thin­ned, and retrea­ted. Melt­wa­ter ponds on top of the gla­ciers, drai­ned into the new cracks and wea­k­en­ed the gla­cier ice. In a simi­lar sce­na­rio for Lar­sen C, the rese­ar­chers pre­dict a con­tri­bu­ti­on to the glo­bal sea level rise of 50 cm until the year 2100, which will be a chall­enge for many coas­tal cities.

http://www.nature.com/articles/ncomms11897

Lan­tern fruits in Ant­ar­c­ti­ca? Toma­toes, pota­toes and tob­ac­co from the big ice?

Accor­ding to the online news sec­tion of the maga­zi­ne Sci­ence, US-Ame­ri­can and Argen­ti­ni­an rese­ar­chers have found fos­sils in Pata­go­nia, Argen­ti­na, that belong to the nights­ha­de fami­ly, as today’s toma­toes, pota­toes and toma­til­los.

The­se plants lived more than 50 mil­li­on years ago in a warm, humid cli­ma­te, when South Ame­ri­ca was still very clo­se situa­ted to the Ant­ar­c­tic Pen­in­su­la. The Dra­ke Pas­sa­ge did not yet exist. Ins­tead, a shal­low shelf sea sepa­ra­ted the Paci­fic Oce­an from the Atlan­tic and South Ame­ri­ca from Ant­ar­c­ti­ca. At the same time, the bor­der bet­ween the sub­tro­pi­cal cli­ma­te zone and the tem­pe­ra­te cli­ma­te zone went across the Ant­ar­c­tic Pen­in­su­la. Befo­re the Ant­ar­c­tic con­ti­nent got cover­ed by snow and ice, it might well have been that the­se anci­ent ground-cher­ries also grew in Ant­ar­c­ti­ca.

With the dra­stic cli­ma­te chan­ge towards the ice con­di­ti­ons alre­a­dy on the hori­zon, Ant­ar­c­ti­ca did not beco­me a lan­tern fruit place. In con­trast, it is by far the most hosti­le con­ti­nent on the pla­net and not your place at all if you are a toma­to.

Source: Sci­ence Dai­ly