The research work of the Sea Ice and Polar Oceanography Group is concerned with air-sea-ice interaction processes in polar oceans and their role in climate, and also with the dynamics and mechanics of sea ice. Activities during 1994-95 focused on research projects in the Greenland Sea, especially in the central gyre region where winter convection occurs; in the Beaufort Sea with studies of ice deformation; and in the Weddell Sea in the Antarctic.

The largest research programme with which the group is involved is ESOP, the European Subpolar Ocean Programme. This is funded by the Commission for the European Communities under the MAST-II (Marine Science and Technology) Programme, and is the fourth largest of the 70 projects in MAST-II. The research involves 21 partners in seven countries (Denmark, France, Germany, Iceland, Norway, Sweden, and the UK) and the project is co-ordinated from SPRI. The purpose is to study ice-ocean interaction in the Greenland Sea with special reference to the role of sea ice in winter convection. In the central Greenland Sea, the ice cover of the East Greenland pack frequently develops an eastward tongue in the latitude range 72-76°N, where the Jan Mayen Polar Current diverts cold water to the east. The tongue is due to local ice growth, which occurs in the form of frazil and pancake ice owing to extreme sea states. Salt rejected from the growing sea ice contributes to the overturning of the surface water, leading to convective plumes that carry water down to the deep ocean. Evidence from tracers suggests that since 1982 convection has failed to reach the deep waters and is now terminating at depths of 1500m and, latterly, less than 1000m. This is having a profound effect on the Greenland Sea deep water, which is becoming warmer and more saline, and may also accelerate global warming, since the convection process acts as a sink for carbon dioxide carried down from the surface waters.

During 1994-95 the Group was involved in the analysis and interpretation of data from field experiments, in continued work with remote sensing imagery of the ice cover, in modelling studies, and in synthesis of the results. Modelling work was carried out using ice-ocean modelling of the Greenland Sea interacting with the Meteorological Office GCM (General Circulation Model) of the atmosphere, for which purpose a computer link was established between SPRI and the Met Office Cray computer. Remote sensing analysis involved interpretation of ERS-1 SAR (synthetic aperture radar) imagery and SSM/I (Special Sensor Microwave Imager) passive microwave data from the Odden ice tongue in relation to data from field observations.

In the Greenland Sea, a second MAST-II project has been carried out by the group, a collaboration between SPRI and IMGA-CNR, Modena. The aim of this project is to spectrally analyse SAR imagery of the Odden region to measure the wavelengths and propagation vectors of the dominant ocean wave species entering the frazil-pancake ice cover from the open sea. Theory developed by Dr Wadhams predicts that wavelength should decrease in ice (and thus refraction will occur if waves are incident obliquely) to an extent that depends on the thickness of the frazil-pancake layer. By examining successive subscenes it is possible to map the thickness of the ice in Odden and thus achieve a better insight into the likely flux of salt into the upper ocean.
The main field work undertaken by the Group during 1994-95 was in the Weddell Sea, Antarctica, where a sea-ice research programme was run from HMS Endurance during February 1995. The project was designed to match surface observations of sea ice properties with aerial photographic swathes and satellite SAR imagery, in order to elucidate the nature of the Antarctic ice edge in late summer and its signature on SAR. The ship sailed from Punta Arenas, with the SPRI participants being Dr Wadhams and Stephen Wells his Research Assistant. After a call at O'Higgins Base on the Antarctic Peninsula in order to co-ordinate data acquisition with the German SAR receiving station there, the ship entered the northwest Weddell Sea through Antarctic Sound and carried out a series of experiments during a seven-day period. On each day the ship would run into the ice along a line that was being covered by an ERS-1 SAR orbit, using her Lynx helicopters to land the SPRI team on a succession of ice floes. On each floe the party took an ice core, measured snow and ice physical properties, recorded strain and accelerations due to ocean waves, and took CTD (conductivity-temperature-depth) profiles through the uppermost 80m of the water column to measure melt water effects. Meanwhile the ship was carrying out CTD profiles at 5-10 nml intervals. As near as possible to the exact time of the satellite overflight a helicopter would carry out a 100 nml aerial photography flight along the line of the orbit. By matching these datasets from three levels (satellite, air borne, surface) we have been able to gain new insight into the radar response of Antarctic sea ice, also making the discovery that late summer sea ice in the Weddell Sea is covered with melt pools, a phenomenon previously thought to be confined to the Arctic. Strain and acceleration measurements were also carried out on two tabular icebergs. The team disembarked at Port Stanley.

HMS Endurance, the Royal Navy's Ice Patrol Ship
A Class 1 Ice Breaker she was originally built in Norway in 1990 as MV Polar Circle. The RN chartered her in 1991 before she commissioned as HMS Polar Circle on 21 November 1991. She was subsequently renamed HMS Endurance. Her Mission is "To patrol and survey the Antarctic and South Atlantic, maintaining Sovereign Presence with Defence Diplomacy and supporting the global community of Antarctica". This involves close links with the Foreign Office, United Kingdom Hydrographic Office and the British Antarctic Survey. She deploys annually to the Antarctic, her operating area for 7 months of the year. Her base port is Portsmouth, which is also the ship's affiliated town. The Ship's motto is "Fortitudine Vinvimus" ~ 'By Endurance We Conquer' The motto originates from that of the great Antarctic explorer, Sir Ernest Shackleton who made history in his ship, 'Endurance' in his expedition south in 1914-15.

HMS Endurance Statistics
Displacement: 6500tons; Length: 91metres; Beam: 17.9metres; Draught: 8.5metres; Top speed: 14 knots; Cruising speed: 12 knots; Complement: 112 plus 14 Royal Marines; Aircraft: 2 x Lynx helicopters; Propulsion: 2 Bergen BRM8 diesels, 8160hp, 1 shaft with controllable pitch prop and bow and stern thrusters.

This Commemorative Cover
This cover was flown to the Falkland Islands in a Tristar of No 216 Squadron and the covers were then flown aboard HMS Endurance aboard one of her Lynx helicopters. The cover has been signed by Captain DA Phillips, Commanding Officer of HMS Endurance and also by the HMS Endurance Flight Commander who flew the covers. The cover bears two cachet the first being the HMS Endurance Commanding Officers handstamp and the second for HMS Endurance Antarctica.

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