Unlike Coleridge’s Ancient Mariner, unwillingly blown there by a tyrannous storm-blast, the modern day seafarers aboard the JOIDES Resolution traveled to the Antarctic coast very much on purpose, following many years of preparatory work to identify the best sites to drill and retrieve sediment cores from beneath the sea floor.
In early January, after wowing the curious youngsters of the GNS Science educational program Discover Ancient Worlds, the Resolution left New Zealand waters and navigated the increasingly sea ice-littered Southern Ocean to reach the polynya coast of Wilkes Land. Cold, dense katabatic winds flowing off the East Antarctic Ice sheet push free sea ice away from this coast and deliver iron-rich terrestrial dusts to the resultant open waters, which fertilise massive algal blooms.
But getting there is only half the challenge. Once the Resolution arrives at its desired drilling location, there is the problem of itinerant icebergs that care little for the logistical conveniences of scientists. If need be the Resolution can pause drilling operations (that run 24/7 by the way), lift the drill pipe free of the sea floor, graciously make way for the icy behemoth bearing down on the site, and then find and re-enter the hole in the sea floor to continue drilling. Carrying out such engineering gymnastics in 4000 metre-deep water is no small feat.
By observing signals in marine sediments deposited during past warm extremes and times of abrupt climatic warming, the investigators will be better placed to make predictions about what kind of environmental change we can expect in Antarctica in association with anthropogenic global warming.
The classical view of Antarctic ice sheet evolution has been of unstable ice sheets beginning to form around 35 million years ago, with continental ice sheets becoming relatively stable around 13.5 million years ago. However, as Rob McKay of the Antarctic Research Centre points out, this view is based mainly on evidence from deposits at high elevation sites in the Transantarctic Mountains and McMurdo Dry Valleys. The initial results of ANDRILL suggest that there have been significant fluctuations of the marine margin of the generally sub-sea-level-grounded West Antarctic Ice Sheet during the last 14 million years. Extensive parts of the marine margin of the East Antarctic Ice Sheet are also grounded below sea level.
What was happening on the coasts of East Antarctica during this time? How do the climate, ice sheets and ocean currents interact? What does the sedimentary record from coastal Antarctica tell us about conditions in the greenhouse worlds of the past? With the research cruise successfully completed, these questions and more can now begin to be answered by Rob and others in the international science team.
Photos (c) Rob McKay 2010