Gigantic iceberg altering natural processes

 C28 moves away from Mertz glacier while B09B remains grounded
20 March 2010 - C28 moves away from Mertz glacier while B09B remains grounded. (Photo: Neal Young)
C28 breaking up and B09B still grounded

The gigantic iceberg which calved from the Mertz Glacier in mid-February is altering natural processes in the surrounding ocean as it moves westward away from the glacier.

The iceberg, named C28, broke away from the glacier after another 97-kilometre long iceberg (B09B) collided with the glacier tongue.

C28 is now 250 kilometres from the glacier and moving very slowly parallel with the Antarctic coast, while B09B remains grounded near the glacier.

Australian Antarctic Division glaciologist, Dr Neal Young, said that initially C28 moved into the area of the Mertz polynya (an area of open water where sea ice forms rapidly) next to the glacier tongue.

It changed the shape and formation of the polynya, splitting it into several smaller sections.

"C28 disturbed the natural "ice factory" role of the polynya and while new sea ice was still forming, it appeared to be at a lower rate than before," Dr Young said.

A lower rate of production of new sea ice also affects the production of Antarctic Bottom Water (the coldest, saltiest and deepest water in the ocean).

C28 then drifted further to the west and split into two large sections when it collided with a submerged peak at the beginning of April.

It is now well out of the area of the polynya, near the edge of the continental shelf.

Changes in the polynya and the circulation of the water over the continental shelf may have wide-ranging impact on the biological communities that live in the region.

The Antarctic Division's plankton biologist, Dr Graham Hosie, said the change in ocean circulation patterns in the area will affect plankton distribution and production.

"If there is an increase or decrease in plankton production in the polynya, this could have a knock-on effect up the food chain, particularly on krill, fish, penguins and other predators," Dr Hosie said.

Further disturbance to the polynya can be anticipated when the other massive iceberg, B09B, starts to move again.

Antarctic Division scientists already have a base-line of information on the biology of the area from a 2008 Collaborative East Antarctic Marine Census (CEAMARC) voyage.

It’s hoped this "before" snapshot will help scientists accurately gauge the full impact of C28 on the biology of the region.