Does the ice sheet in East Ant­arc­tica shrink or grow un­der warm­ing cli­mate?

In­ter­na­tional ex­ped­i­tion in­vest­ig­ates how the Ant­arc­tic ice sheet has changed in the course of thou­sands to mil­lions of years.

The Ant­arc­tic re­search sea­son has be­gun 15 Decem­ber, when re­search­ers in the in­ter­na­tional re­search pro­ject MA­GIC-DML re­turned to Dron­ning Maud Land in Ant­arc­tica to in­vest­ig­ate how ice sheet volume has changed.

Dron­ning Maud Land in Ant­arc­tica is al­most en­tirely covered by the East Ant­arc­tic Ice Sheet. Even though a re­duc­tion in ice sheet volume since the last ice age has been con­firmed here, it is one of the least stud­ied areas in Ant­arc­tica.

Un­der­neath the ice sheet is a land­scape com­posed of hills, val­leys, moun­tains, and planes, sim­ilar to land­scapes on other con­tin­ents. When the ice sheet shrinks, this land­scape be­comes gradu­ally ex­posed and the first parts of the land­scape to emerge from the ice are the sum­mits of the highest moun­tains, known as nun­ataks. Nun­ataks con­tain a wealth of in­form­a­tion that can show how thick the ice sheet was dur­ing vari­ous peri­ods of the past when global cli­mate was colder than present and how much it has thinned un­til today. Nun­ataks also re­veal unique in­form­a­tion on the fluc­tu­ations of the ice sur­face dur­ing past warm peri­ods, such as the mid-Plio­cene warm in­ter­val dated back to about 3 mil­lion years ago. Dur­ing this re­mote period of glob­ally warmer cli­mate in­land parts of the East Ant­arc­tic ice sheet re­ceived more snow­fall and were thicker than today. Such in­form­a­tion is es­pe­cially im­port­ant in the light of the on­go­ing cli­mate change and its po­ten­tial im­pacts on the East Ant­arc­tic ice sheet and the global sea level.

“Un­der­stand­ing how the ice has thinned is very im­port­ant in or­der to un­der­stand how the en­tire ice sheet might change in the long run. We know very little about this when it comes to Dron­ning Maud Land,” says Ar­jen Stro­even, Pro­fessor in Phys­ical Geo­graphy at Stock­holm Uni­versity, and Prin­cipal In­vest­ig­ator of the pro­ject.

Earth is con­stantly bom­barded by cos­mic ra­di­ation which con­sists of ex­tremely en­er­getic particles from space. The ice sheet acts as a shield, but when the ice sheet shrinks and nun­ataks are ex­posed, min­er­als in ex­posed rock, such as quartz, be­come en­riched in cos­mo­genic nuc­lides. By meas­ur­ing the con­cen­tra­tion of such cos­mo­genic nuc­lides in er­ratic rocks on the slopes of nun­ataks, we can cal­cu­late how long these rocks have been ex­posed to cos­mic ra­di­ation. As a res­ult, re­search­ers can as­cer­tain how much, and at what rate, the volume of the East Ant­arc­tic Ice Sheet has changed.

Samples from the nun­ataks will, to­gether with satel­lite im­agery and to­po­graphic mod­els, be util­ised to im­prove ice sheet and cli­mate mod­els and yield in­form­a­tion on how the East Ant­arc­tic Ice Sheet and sea level are af­fected by cli­mate change; both his­tor­ic­ally and in the fu­ture. “In Ant­arc­tica dir­ect re­con­struc­tions of past cli­mate con­di­tions and ice changes are lim­ited to few loc­a­tions of deep ice cores and do not ex­tend far enough to shed light on the ice sheet re­sponse to the mid-Plio­cene warm­ing,” says Dr. Ir­ina Ro­gozh­ina, the leader of the mod­el­ing team in the MA­GIC-DML pro­ject at the Cen­ter for Mar­ine En­vir­on­mental Sci­ences, Uni­versity of Bre­men. “Nu­mer­ous im­prints left on nun­ataks by thicker pre­de­cessors of the mod­ern East Ant­arc­tic Ice Sheet do no only reach much fur­ther into the Earth’s his­tory but also provide in­valu­able in­form­a­tion on the im­pacts of warmer-than-mod­ern cli­mate on the ice sheet mar­gins.”

About the re­search ex­ped­i­tion

Last sea­son, MA­GIC-DML worked in areas close to the Swedish re­search sta­tions Wasa and Svea. This sea­son, the start­ing point for field work is the South African re­search sta­tion SANAE IV. The re­search­ers will work along a tran­sect across the Ahl­mann Ridge, the Borg Mas­sif and the Kir­wan Es­carp­ment, a moun­tain area near SANAE IV. Dur­ing the ex­ped­i­tion, the re­search­ers are provided with sup­port and ex­pert as­sist­ance from the Swedish Po­lar Re­search Sec­ret­ari­at’s lo­gist­ics staff, which are re­spons­ible for trans­port, tech­no­logy, safety and health­care.

The field team that will work in Ant­arc­tica dur­ing the ex­ped­i­tion con­sists of sci­ent­ists from the uni­versit­ies in Glas­gow (UK), Stock­holm (Sweden) and West La­fay­ette (USA). The ex­ped­i­tion has star­ted in Decem­ber 2017 and ends 10 Feb­ru­ary 2018.

Source

MARUM | Ulrike Prange 2018