Sea ice covers 7% of the surface of our planet. It is highly variable and is thought to be key to resolving questions about the Earth’s energy balance. This month members of SAMS Physics, Sea Ice and Technology group are returning to the Arctic on a multi-pronged mission to trial custom-built gadgets as the quest continues to find out more about the physical processes in the polar seas that affect the global climate.
During a short but busy fieldtrip to the Arctic, Drs Jeremy Wilkinson and Keith Jackson will set up eight separate experiments to test equipment designed or adapted at SAMS specifically for projects in the Arctic and Antarctic. The experiments include ways to generate energy using temperature differentials between sea and air, ways to measure ice thickness, ice temperature, ice growth and melt, internal ice pressure, and a way to accurately measure the rise and fall of sea ice on the tides.
SAMS scientists have been working with Inuit hunters for over a decade to achieve best results on the ice thickness project by combining traditional knowledge and modern technology. The Inuit hunters of Qaanaaq, northwest Greenland, still largely depend on dogsleds for transport and hunting. By using an autonomous system attached to dog sleds, ice thickness data can be obtained over a wide area in a short time. In an early trial, sleds with mounted units covered 200 km in two days collecting readings that corresponded to 20,000 independent ice thickness measurements by electromagnetically measuring the conductivity of the sea ice. Now that the sled-mounted system has proved its worth and has been refined to include GPS, solar powering, better size and positioning on the sled and a motion sensor with auto-on and off capability, two other test projects are surveying the ice concurrently this month to get data coincident with the sled measurements so that the results can be compared and corroborated.
Woods Hole Oceanographic Institute is testing an unmanned airborne system (UAS), like a sophisticated model plane, to survey the ice and the fjords. NASA IceBridge team on the other hand is using manned aircraft to fly transects across the Arctic Basin to understand how glaciers are melting. In both cases the tracks flown will include following SAMS’s sled-mounted systems to ensure spatial and temporal consistency of collected data.
Other projects include SATICE – a buoy to measure Arctic tides – and an internal ice pressure experiment. The SATICE buoy is fixed on the sea ice and uses high precision GPS to measure vertical ice movement as the ice rises and falls on the tides. Tidal range is 3-4m and SATICE can measure accurately to 2 cm. Data is transmitted in real time and the equipment will be collected at the end of this field trip. The internal ice pressure experiment is in the early stages of testing instruments and sensors to measure the pressure of the sea ice, which depends on temperature, weather, wind and tides. This equipment will provide information to shipping across the Arctic as internal ice pressures affect the time and fuel required for travelling through the ice fields.
A major problem to overcome when deploying equipment in the Polar Regions is power supply. Solar power is out of the question during the dark winter months and anything with moving parts, like a wind turbine, is vulnerable to humidity and icing up. However, SAMS marine technology group has designed the “SEEBECK” to generate power using the thermoelectric effect: converting the temperature differential of ca. -2° C in the sea below the ice to -25° C in the air above into electricity. It depends on an enclosed copper tube containing methanol in a vacuum that vaporises at the bottom and condenses at the top to produce 100 watts of heat, which can be used to power equipment throughout the year, no matter the conditions.