In deep: Australian research in the Southern Ocean

This edition of the Australian Antarctic Magazine features the Southern Ocean. Formed 130 million years ago when the supercontinent Gondwana broke up and Africa, South America, India and Australia moved northwards, the Southern Ocean surrounds Antarctica. Its major current, the Antarctic Circumpolar Current, rotates clockwise around the continent and mixes the waters from the southern parts of the Earth’s three great oceans – the Atlantic, Pacific and Indian. Its cold waters hold much oxygen, and the rich nutrients of the surrounding oceanic abyss, coupled with the short but intense spring and summer growth periods, support vast populations of krill, fish, seabirds, penguins, seals and whales.

Despite its remoteness, the Southern Ocean has been overexploited on a truly vast scale. As Steve Nicol showed in his article in the last edition of Australian Antarctic Magazine 3:6 first seals then whales, fish and krill were subject to intense and unregulated harvesting with many species being brought to the brink of extinction. Andrew Constable reviews the key international instruments that are now in place to govern the sustainable management of the region, and talks about our recently established Southern Ocean Taskforce and our attempts to develop strategic approaches to the conservation of Antarctic marine living resources and their sustainable use, as well as to the growing problem of illegal, unreported and unregulated fishing. There is much to be done, and little time remaining.

The Southern Ocean touches the lives of us all. The rotation of the Earth generates air movements that travel to the north east from the edge of the Antarctic continent. The steady march of cold fronts that flick across southern Australia indicates how much our weather is influenced by what is going on down south. Our work in the Cooperative Research Centre for the Antarctic and Southern Ocean, based at the University of Tasmania, has taught us much about how ice, water and atmosphere interact in the generation of the world’s weather. Steve Rintoul and John Church point out that the Southern Ocean functions as a huge heat sink, storing and transporting heat from one part of the Earth to another. The release of heat into the atmosphere influences temperature and rainfall far to the north. Nathan Bindoff and Helene Banks show us that change is happening in the Southern Ocean and that it is warming and becoming less salty in parts. These changes affect the sinking of cold, dense salty water and influence not only our climate and weather patterns but also the circulation patterns of the Earth’s ocean currents.

It is not only heat that the Southern Ocean stores. Carbon dioxide – the greenhouse gas given off during combustion of organic materials – is stored in huge amounts by the ocean. It is incorporated by marine plants into their tiny skeletons (see pictures by Harvey Marchant on p. 21) and eventually finds its way to the sea bed. Here it can remain for thousands of years, locked away in the ooze and detritus that coats the ocean floor. As humans produce increasing quantities of carbon dioxide we need to better understand how the oceans can help to strip this gas from the atmosphere. Bill Budd and Roland Warner from the Antarctic Cooperative Research Centre have developed models incorporating carbon dioxide levels higher than we currently experience into long-term models of the stability of Antarctic ice-shelves. They suggest that the great ice-shelves of Filchner-Ronne and the Ross Sea will disappear within a few centuries under an enhanced warming regime. By the time two millennia have passed it may be possible to navigate a ship from the Ross Sea into the Weddell Sea! Our models are only as good as our data, and the Southern Ocean has been less studied than the Earth’s other oceans, but the predicted changes to ice abundance and sea-level rise are of great concern to the future management of coastal Australia and elsewhere in our region.

The Southern Ocean is a living, breathing, organic body of water that embraces us and nurtures us in ways we cannot yet fully appreciate. The articles in the pages that follow reveal some of its challenges and delights.

Fittingly, we begin this 2002–03 Antarctic season with a major marine research voyage. Deep ocean moorings with automated sediment traps will be deployed and the contents analysed to help us understand the role of the Southern Ocean in controlling atmospheric CO2 levels. Scientists will also be studying the primary productivity of sea ice microbial communities – a vital link in the Southern Ocean food web – in the region of the Mertz Glacier polynya, and the melt rate of giant iceberg B9B. Later in the season another major marine program will investigate the distribution and abundance of krill in the part of the ocean where our Béchervaise Island Adélie penguins feed, and continue the study on the effects of UV radiation on aquatic micro-organisms. On the latter part of that voyage scientists will examine the structure and flow of the Antarctic Circumpolar Current, a key to understanding the global climate system.

Also in this edition you will find news of the current season’s field-based activities, and of a number of interesting developments that have occurred during the past six months. We have a big season to manage this year: the work in the Southern Prince Charles Mountains, being conducted jointly with Germany’s Bundesanstalt für Geowissenschaft und Rohstoffe (Geological Survey) is a major undertaking that will provide valuable information about the geological and glaciological histories and past climates of eastern Antarctica. At Casey we are continuing with work on cleaning up the Thala Valley tip site, and at Mawson we are building a wind turbine farm. Davis should see the installation of a VHF radar array, and upgrades to the LIDAR. Again at Casey, we are undertaking preliminary work on a blue-ice runway. At Cape Denison we will continue vital conservation work on the wooden huts used by the Australasian Antarctic Expedition 1911–1914 led by Douglas Mawson. And in addition we have very many other terrestrial and marine projects in many places to complete!

I wish you and your families well for Christmas and I hope your New Year will be as rich and fulfilling as ours promises to be.

Tony Press
Australian Antarctic Division