Uplift of the nor­t­hern Ant­ar­c­tic Pen­in­su­la: result of tec­to­nics and ice loss

The pro­cess of land uplift as a con­se­quence of loss of lar­ge ice mas­ses is well known from nor­t­hern Scan­di­na­via and Spits­ber­gen, whe­re traces of such events inclu­ding rai­sed bea­ches can be seen in many places. In Ant­ar­c­ti­ca, it is more tri­cky as the­re is not much ice-free land.

Pre­cise GPS-mea­su­re­ments have reve­a­led recent uplift dyna­mics of the nor­t­hern Ant­ar­c­tic Pen­in­su­la. And not just that: while uplift was almost negli­gi­ble with 0.1 mm/year until 2002, the value jum­ped up to 8.8 mm/yr – an increase by a fac­tor of almost 90! This is remar­kab­le, both in terms of the deve­lo­p­ment and the abso­lu­te value of pre­sent land uplift: near­ly 1 cm/year is very fast, geo­lo­gi­cal­ly spea­king.

The col­lap­se of the Lar­sen B ice shelf in 2002 has been assu­med to be the main dri­ving force behind the land uplift: immense volu­mes of floa­ting shelf ice bro­ke off the east coast of the Ant­ar­c­tic Pen­in­su­la and floa­ted out into the Wed­dell Sea as lar­ge tabu­lar ice­bergs. The loss of form­er­ly land-based was a con­se­quence of the loss of the sta­bi­li­zing ice shelf. The result of such an immense loss of weight is iso­sta­tic rebound of the crust, lea­ding to land uplift.

Geo­phy­si­cal model­ling has now shown the ice loss to be insuf­fi­ci­ent to explain rate and deve­lo­p­ment of land uplift as obser­ved. Move­ments in the man­t­le, at 100 km depths and lower, need to be taken into account to explain the data ful­ly.

The Brans­field Strait, a small ocea­nic basin sepa­ra­ting the South Shet­land Islands from the nor­thwes­tern Ant­ar­c­tic Pen­in­su­la, is a tec­to­ni­cal­ly acti­ve area. The­re are seve­ral vol­ca­noes in the area that erupt­ed very recent­ly in geo­lo­gi­cal term, and seve­ral frac­tu­re zones and pla­te boun­da­ries.

Source: Earth and Pla­ne­ta­ry Sci­ence Let­ters