| Summary: | The annual expansion and contraction of sea ice in the Antarctic represents one of thebiggest natural changes on Earth. At its maximum annual extent in September/Octobersea ice cover extends about 19 million square kilometres of the ocean around Antarctica one and half times the size of the continent itself. In the summer sea ice shrinks toaround 3 million square kilometres. Antarctic sea ice plays a major role in the global climate system and in the ecology ofthe Southern Ocean. The sea ice region is the source of Antarctic Bottom Water, a majordriver of global ocean overturning circulation. Sea ice is important in reflecting solarenergy back into space. It is a habitat and a source of primary production for SouthernOcean ecosystems. Sea ice cover in the Antarctic is changing. In the west Antarctic Peninsula region, seaice extent has dramatically reduced, and the length of the sea ice season has alsoshortened. In the Ross Sea region of the Antarctic, however, the maximum annual extentof sea ice cover has increased and its season extended. Overall, the maximum annualextent of Antarctic sea ice has increased by around 1.5% per decade since 1979 (or byaround 285,000 square kilometres). This compares to a loss of 1.8 million square kilometresof sea ice maximum annual extent in the Arctic. One important aspect of Antarctic sea ice that we know very little about is change toits volume. While satellites can measure the aerial extent of sea ice, reliable methodsto remotely measure sea-ice thickness are only just emerging. In contrast, data fromsubmarines in the Arctic have allowed detailed monitoring of regional changes to Arcticsea-ice thickness over a number of decades. What is happening in the physical, chemical and biological systems beneath Antarcticsea ice is poorly understood. Because of the critical role of sea ice, it is vital that wedevelop a better understanding of the future trends in sea ice extent and volume, andconsequences for Antarctic and Southern ocean ecosystems. Australia is well placed to take a lead role in these studies - especially in the East Antarctic.Australia has a mature Antarctic research program that has demonstrated that it cancollaborate with other nations, and across scientific disciplines, to do the complexscience that is required to understand these important issues. Having the logistic andinfrastructure capabilities will be vital to ensuring that this important region of the planetis understood.
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