It used to be thought that the volume of water flowing into the oceans from melting glaciers and icebergs in Antarctica was equal to the amount of water falling as snow onto the continent; and that this process was keeping the whole system in balance. But some glaciers in the Antarctic (and also in Greenland) are losing ice at a faster rate than they are being replaced. This affects sea level all over the world.
iSTAR is an ambitious scientific programme funded by NERC (Natural Environment Research Council). It brings together leading scientists from 11 UK universities and from the British Antarctic Survey (BAS).
The mission is to improve understanding of what’s happening to the area of the West Antarctic Ice Sheet where the greatest rates of ice loss over the last decades have been observed. New knowledge about the stability of this ice sheet is critical for making better predictions about how the ocean and ice will respond to environmental change, and what impact this may have on future sea level. Will ice loss carry on increasing at a faster and faster rate, or will it slow down or go back to equilibrium?
The six-year, £7.4 million programme is organised into four main research projects — each uses state-of-the art technologies to make new discoveries about the ocean or the ice.
Analysis of observations and measurements will create knowledge and understanding that will make a major contribution to the ongoing urgent international scientific effort to understand our changing world. The results of these investigations will bring many benefits to science, to policy and to economic decision-making — which will ultimately contribute to the well-being of our society.
Twin Otter aircraft (65p)
BAS operate four DHC-6 Twin Otter aircraft. Unlike the larger Dash 7 the Twin Otter is able to get supplies and personnel into the field away from groomed runways. With skis as well as wheels they will be used to take personnel to and from the tractor train (this consists of two Kässbohrer Pistonbully 300 Polar tractors, two long poly sleds with fuel bladders, and three metal cargo sledges, one of which carries an accommodation caboose) both during the deployment and science phases. They will also be used to allow a small team to visit remote rock outcrops (nunataks) to install GPS receivers and take rock samples. These aircraft are a vital part of Antarctic operations to support the iSTAR programme.
The Twin Otters are extremely versatile and can be modified to allow airborne surveying and other scientific equipment to be fitted. Remote sensors fitted to the aircraft provide scientists with data on land, ice and sea. Radar can decipher features under the ice or layers within the ice itself. Longer-term monitoring from the air can be used to record the break-up of ice sheets or atmospheric changes.
Surface Radar (75p)
The radar uses high frequency waves to penetrate 50-100 m deep into the snowy surface of the glacier. It can detect the fine layers of snow laid over the years, a little like a fuzzy snow-ring picture, and help scientists interpret information gained from other techniques such as ice-core drilling. The shape of the snow can tell scientists something about the rock underlying the glacier.
RRS James Clark Ross (£1.00)
The JCR, as it is commonly called, is the UK’s main ice-strengthened research vessel. Built in 1990 and measuring 99 m long, it has been specially designed both to bring supplies to BAS’s research stations and to have the endurance and facilities to support long research cruises in ice-covered waters. The JCR can plough her way through sea ice a meter thick at a steady two knots.
The standard instrumentation available on the ship includes multi-beam sonar, a long-range hull-mounted Acoustic Doppler Current Meter (ADCP), and a conductivity-temperature-depth (CTD) probe with additional sensors for other parameters such as dissolved oxygen, light transmission, and chlorophyll fluorescence. The CTD is mounted beneath a rosette of spring-loaded water sampling bottles, which can be triggered from the ship, capturing water samples that can be analysed on board, both to calibrate the sensors on the instrument and to measure additional parameters.
One of the aims of the JCR science cruise is to get more information about the ice shelf cavities beneath Pine Island and Thwaites Glaciers. One useful tool to do this is the autonomous underwater vehicle (AUV) Autosub-3. Autosub is no stranger to ice shelves: during the Autosub Under Ice project in 2001-2006 the unmanned vehicle was modified for use beneath sea ice and ice shelves. This is a notoriously risky environment, and in spite of all possible precautions being taken, Autosub-2 was lost beneath Fimbul Ice Shelf in 2005. However, Autosub-3 successfully carried out a series of missions beneath Pine Island Glacier in 2009, and in 2014 it is hoped that more data will be obtained from Pine Island Glacier as well as from Thwaites Glacier.
Autosub is launched and recovered from a special crane mounted on the stern of the JCR; it can be lifted from the water and retracted straight into its workshop container, where all work can be carried out in sheltered conditions.
Autosub-3 was designed, developed and built at the National Oceanography Centre in Southampton with funding from NERC. Autosub is 7 m long and weighs 3.5 tonnes. Travelling at 6 km per hour it is capable of diving up to 1,600 m deep, and can operate for 72 hours (400 km) between battery changes (it is powered by 5000 ordinary D-cell batteries). It will be used by the Ocean under ice project (iSTAR B) to create a 3-D map of the ice above and the seabed below using a multi-beam sonar system. It also carries precision instruments for measuring the salinity, temperature, and oxygen concentrations in the sea water beneath the ice shelf, which are vital to understanding the flow of water and the rate of melting.
FDC – iSTAR Caboose Module
The accommodation caboose is intended mainly as a shelter, work space, cooking area, and transportation area during the science traverses. It consists of a modified shipping container mounted on one of the Lehmann sledges, and is fitted out with a kitchen, snow melting system, generators, batteries, and communications equipment. While the caboose is a luxurious home for four people during the deployment phase, it will probably get a bit crowded if all twelve personnel are inside during the science traverses. During the science traverses tents will be erected when the tractors are stopped, both for accommodation and for additional working space, if required.
65p Rod Arnold, British Antarctic Survey.
75p David Vaughan, British Antarctic Survey.
£1.00 British Antarctic Survey.
£1.20 Pierre Dutrieux, British Antarctic Survey.
FDC David Vaughan, British Antarctic Survey.
Design: Bee Design
Printer: BDT International Security Printing
Stamp size: 28.45 x 42.58mm
Perforation: 14 per 2cms
Release date: Expected 16-19 November, 2014
Production Co-ordination: Creative Direction (Worldwide) Ltd