SOUTHAMPTON OCEANOGRAPHY CENTRE

SOC measures deep Atlantic currents for first time
Southampton Oceanography Centre scientist Dr. John Gould has recently worked with scientists in the United States and Europe to map sub-surface water circulation in the north eastern North Atlantic. The results were published in the 10th October issue of ‘Nature’. This was their first measurement of the currents of the northern North Atlantic below the ocean surface. Circulation in this part of the Atlantic is important not only to the local climates of America and Europe but affects the global climate and climate change.

Some 200 floats drifting with the currents took measurements at two depths, near 1km and 2km, their positions acoustically tracked by sound signals transmitted from moored sources. At depths of 1km, the ocean is influenced by water from the Mediterranean, at 2km by water from the Labrador Sea west of Greenland. A key finding was how the seafloor topography constrains circulation patterns well above the bottom, in particular the eastward flow from the Labrador Sea is confined to fracture zones, narrow gaps in the mid-Atlantic Ridge.

8 November 02

Autosub heads for Antarctica
In February this year Dr David Vaughn of the British Antarctica Survey will be using Southampton Oceanography Centre's Autosub to investigate under the cavity beneath Pine Island Glacier, one of the fastest Antarctic ice streams. Satellites show that the grounded portion of the glacier thinned by up to 1.6m per year from 1992 to 1999. A large iceberg, 42 by 17 kilometres, broke off the Pine Island Glacier in early November 2001.

Ice shelves are the floating edges of the ice sheets that cover Greenland and Antarctica. These shelves are involved in the waxing and waning of the ice sheets as climate changes. They contain over 70% of the world's freshwater - enough to increase sea level by 80m if they melted entirely. But what takes place in the vast water cavities beneath ice shelves - which can be a thousand metres thick - is largely unknown.

Autosub's unique capabilities will allow Vaughn to make the first direct measurements of the newly exposed bed of a retreating ice stream. The AUV will be diving to depths below 1000m to gain access to the glacier cavity. On previous research missions in the open ocean, Autosub has been programmed to surface if she gets into difficulties. The engineering team at SOC designed a completely novel navigation system to overcome the dangers of working in an enclosed space. This research project is the first in the Autosub ‘Under Ice Program’ funded by the UK Natural Environment Research Council.