Earth Institute News
Contact: Mary Tobin
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Reports From the Field
The Antarctic AnSlope Expedition,
February 25 through April 11, 2003
This week's report: 04/07/03 (final installment)
Dr. Arnold L. Gordon, of the Lamont-Doherty Earth Observatory, is aboard the Research Vessel Nathaniel B. Palmer in Antarctic’s northwestern Ross Sea. Gordon is the principal investigator leading a study to build on scientific understanding of global climate and the crucial, but not well understood role played by a frontal zone known as the Antarctic Slope Front (ASF) occurring near the upper continental slope of much of Antarctic’s perimeter. This research, part of a multi-expedition project called AnSlope, seeks to unravel the dynamics of cold water transport into the intermediate and deep layers of the deep ocean.
In the Ross Sea, and in other areas around Antarctica’s coast, the interactions between air, sea, and ice form very cold, dense water that descends into the deep ocean to the north, spreading and chilling the lower 2 km of the world ocean. As a result, resident deep and bottom water, which has been diluted and warmed over time, is displaced upward towards the sea surface, a process known as “ocean overturning.” Ocean overturning allows rising waters to mix and sink with dense polar near-surface waters, which take up greenhouse gases such as carbon dioxide that can then be ‘stored’ in the deep ocean. Some think that this process, because of its sensitivity to the temperature and salinity of seawater, and the formation rate of sea ice, might be impacted by rapid climate change, leaving surface waters too light (warm and fresh) to participate in this deep overturning.
Reports from the Field:
Reports from past weeks: March 4, 2003
Reports from past weeks: March 11, 2003
Reports from past weeks: March 18, 2003
Reports from past weeks: March 24, 2003
Reports from past weeks: March 31, 2003
AnSlope Cruise 1, Week 6 [Final]
Monday, April 7, 2003, from Arnold L. Gordon, Chief Scientist
Aboard the R/V NATHANIEL B. PALMER, Ross Sea, Antarctica...
This is my final "Report from the Field" for the AnSlope NBP0302 cruise. We are presently in the open ocean, en route to Port Lyttelton New Zealand after what seemed like an endless field of sea ice within the Ross Sea. Today we are over the Campbell Plateau just south of New Zealand. Luckily we are under the influence of a high-pressure system with fair weather. Two days ago we were in the midst of a storm, not very intense, but enough to lower the attendance at meals. We expect to arrive in port early in the morning of 9 April. We have achieved our science objectives despite much heavier than expected sea ice conditions. The sea ice offered wonderful views, a more challenging environment, and a greater consumption of ship fuel than anticipated. We deployed the moorings in the configuration we sought; we surveyed the stratification of the Ross Sea continental margins from Pennell Trough to Cape Adare to the detailed intended.
We come away from the work with a much-improved view of the characteristics over the continental slope of the Ross Sea. Upon analysis of these data, those to be collected by the next two AnSlope cruises, and of the time series data obtained by the moored instruments (to be retrieved in one year on the third AnSlope cruise), we will be able to meet the objectives of the AnSlope program: to build a quantitative understanding of the processes that ventilate (overturn) the deep ocean along the margins of Antarctica.
Southern Ocean ventilation has global ocean impact and, on some time scale, global climate impact. At issue are the questions: will the Southern Ocean overturning process weaken, strengthen, or remain the same as the global climate changes in response to natural and anthropogenic forces?
Our broader goal is to build a climate model that faithfully simulates the real world. To do so requires that the model properly include the governing ocean processes that move mass, heat, freshwater, and chemical properties within the ocean and between the ocean and atmosphere. With such a tool we can better assess the extent of natural and anthropogenic forced climate change at the regional and global levels; we can project into the future with 'what if' questions. Building such a model requires close working relationships with many different types of scientists, from those who observe the real thing with instruments at sea, to those who strive to simulate the real thing in computer models. There are now more individuals that do both, a healthy sign.
While we still have a ways to go, I have seen ocean and climate models developed from toys to models that "look" pretty good. But how good? A new level of detailed observations of specific parts and processes within the real ocean, using the latest technologies, is needed to answer these questions. When I began my career, I did so because I love to observe things in the ocean that no one else has yet discovered. I still love the exploration aspect of going to sea, but I've become increasingly aware that the research really is important if we are to develop the tools to insure a sustainable and pleasant future.