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Home* Antarctic News → Vol­ca­nic acti­vi­ty under Thwai­tes Gla­cier con­tri­bu­tes to mel­ting

Vol­ca­nic acti­vi­ty under Thwai­tes Gla­cier con­tri­bu­tes to mel­ting

The Thwai­tes Gla­cier in West Ant­arc­ti­ca has recent­ly attrac­ted con­si­derable media atten­ti­on, as sci­en­tists have pre­dict it to col­laps lar­ge­ly in the future. It is up to 4 kilo­me­tres thick and lar­ge enough to con­tri­bu­te with 1-2 metres to glo­bal sea level rise – a dra­ma­tic value. So far, warm sea water has been made respon­si­ble for gla­cier mel­ting on the coast, but now the­re is evi­dence that a signi­fi­cant part of mel­ting actual­ly takes place at the gla­cier base, away from the coast. Thwai­tes Gla­cier is lar­ge­ly based well below sea level, as is the case for lar­ge parts of the West Ant­arc­tic ice shield, a fact that con­tri­bu­tes to its lack of sta­bi­li­ty.

Timing and dura­ti­on of a col­laps are, howe­ver, cur­r­ent­ly unknown, even though it seems wide­ly accep­ted amongst sci­en­tists that a col­laps is very likely. But one of the main influ­en­ces on gla­cier dyna­mics were so far unknown: the geo­ther­mal heat flux from the under­ly­ing crust to the gla­cier ice. Until now, it has been belie­ved that geo­ther­mal heat trans­fer is even­ly dis­tri­bu­t­ed over the area of the under­ly­ing crust.

Sci­en­tists of the Insti­tu­te for Geo­phy­sics of the Uni­ver­si­ty of Texas at Aus­tin have now reve­a­led that this is anything but the case. Sub­gla­cial meltwa­ter move­ment under the Thwai­tes Gla­cier was map­ped with radar-based methods. The result is that meltwa­ter pro­duc­tion is very uneven­ly dis­tri­bu­t­ed. This can be used to cal­cu­la­te the geo­ther­mal heat flux under the gla­cier, which reaches values up to 200 mil­li­watts per squa­re met­re while aver­aging near 100 over the who­le area. In com­pa­ri­son, the average value for all con­ti­nents on Earth is just near 65 mil­li­watts per squa­re met­re.

The­se values of geo­ther­mal heat flux are con­si­de­red “signi­fi­cant” for gla­cier and ice sheet dyna­mics. The Thwai­tes Gla­cier is accord­in­gly loo­sing lar­ge volu­mes of ice due to mel­ting at its base. The geo­ther­mal heat flux is not influ­en­ced by cli­ma­te chan­ges, as oppo­sed to mel­ting that takes place near the coast, in the con­ta­ct zone with sea water which is get­ting incre­a­singly war­mer.

It is the geo­lo­gy which is respon­si­ble for sub-gla­cial mel­ting. Wes­tern Ant­arc­ti­ca is geo­lo­gi­cal­ly acti­ve. Sci­en­tists belie­ve the­re is a rift sys­tem under the ice, simi­lar to the Rift Val­ley of east Afri­ca. This rift sys­tem invol­ves incre­a­sed mag­ma move­ments in the crust and pos­si­b­ly vol­ca­nism at the gla­cier base, simi­lar to vol­ca­noes in Ice­land.

Don Blan­kenship, sci­en­tists of the Uni­ver­si­ty of Texas and one of the aut­hor of a recent­ly publis­hed stu­dy, descri­bed the Thwai­tes Gla­cier as fol­lows: The gla­cier “sits on some­thing more like a mul­ti-bur­ner sto­ve­top with bur­ners put­ting out heat at dif­fe­rent levels at dif­fe­rent loca­ti­ons. … And then you plop the most cri­ti­cal dyna­mi­cal­ly unsta­ble ice sheet on pla­net Earth in the midd­le of this thing, and then you try to model it. It’s vir­tual­ly impos­si­ble.”

But of cour­se sci­en­tists are try­ing to model the Thwai­tes Gla­cier to pre­dict its future dyna­mics. The new know­ledge about geo­ther­mal heat flux under the gla­cier will be a very valu­able con­tri­bu­ti­on to new models.

Gla­cier in the Ant­arc­tic Pen­in­su­la: a dwarf com­pa­red to the Thwai­tes Gla­cier.

Glacier, Antarctic Peninsula

Source: Uni­ver­si­ty of Texas

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last modification: 2014-06-12 · copyright: Rolf Stange
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