Friday 5 March 2010, 11:30 AM (AAD Theatrette)

Science in the Spotlight - 15 min showcase presentation from three science programs

Neal Young

Ice Ocean Atmosphere and Climate

CRAC(K) went the Mertz Glacier Tongue

A massive iceberg has calved from the Mertz Glacier Tongue in mid-February 2010. It has an area of 2550 sq km, length of 78 km, and width between 33 and 39 km. It represents almost 80% of the length of the glacier tongue. It is the first major calving from the Mertz in more than 50 years. The previous calving took place sometime after Mawson's expeditions to Commonwealth Bay, so between 50 and 90 years ago.

Rifts have been developing and cutting across the tongue over many years, so a calving event was anticipated. These developments and studies of the iceberg and glacier that would follow a calving are the subject of a joint Australian-French study of the system. But another culprit came on the scene. Iceberg B9B, a similarly massive iceberg, that has been grounded to the east of the Mertz began to move again in December. In January it rotated around and in early February gave the tongue a powerful nudge. The two icebergs are around 800 Gigatonnes a piece, so that is quite a nudge. The collision caused part of the tongue to shear through releasing the new iceberg, which is itself now rotating into the area of the Mertz polynya.

The glacier tongue formed one side of the Mertz polynya, an area where high a production rate of sea ice leads to production of dense water. This dense water fills and then spills out of a deep depression in the continental shelf (Adelie Depression) to become Antarctic Bottom Water. The Mertz polynya is a major source of AABW, perhaps 25% of the total Antarctic production. Thus the Mertz Polynya is a key element in the processes driving the deep overturning circulation of the global ocean. There is the potential for major changes.

The Mertz Glacier is located almost due south of Hobart, and east of Dumont d'Urville. 

Graeme Ewing

Southern Ocean Ecosystems

Impacts of demersal fishing on benthic habitats in antarctic and sub antarctic waters – an AAD Southern Oceans Ecosystems project update

Demersal fishing interactions with marine benthos in the Australian EEZ of the Southern Ocean: an assessment of the vulnerability of benthic habitats to impact by demersal gears is a FRDC funded project being undertaken by AAD in partnership with FRDC, AFMA and the commercial fishing industry. The project commenced in August 2006, is due to be completed in July 2011, and arose out of the need to better understand the impacts of demersal fishing on benthic ecosystems and habitats. To date, project outputs have included the development and use of autonomous, submersible, and compact digital camera technologies for deployment on fishing gear from commercial fishing boats to directly observe gear/benthos interactions; an assessment of the benthic habitats in the Heard Island and MacDonald Island region; and an Aurora Australis based assessment in east Antarctica to compare the vulnerability of antarctic and sub-antarctic benthic habitats.

Piotr Kuklinski

Environmental Protection and Change

Institute of Oceanology, Polish Academy of Sciences and Natural History Museum, London, UK.

Patterns in skeletal minerology of Bryozoans

Bryozoans are major carbonate-producers in some ancient and recent benthic environments, including parts of the polar marine environments. The large mineralogical and geochemical spectrum exhibited by bryozoans makes them a good group for investigating the differential effects of oceanic acidification (OA) and increase in seawater temperature caused by global warming. Decreased carbonate saturation state caused by OA can be predicted to lead to reduced calcification rates, a shift towards organisms that secrete calcite (which is less soluble than aragonite), and competitive advantages for those organisms without calcified skeletons. To assess the vulnerabilities of different species to climate change we desperately need more information on the skeletal mineralogy and chemistry of the numerous species that inhabit shallow waters, especially in areas most influenced by climate change. In this study we investigate the skeletal mineralogy of bryozoans in latitudinal context and reveal existing patterns of their skeletal mineralogical properties.