Topography and Buoyancy in Polar
Atmosphere and Ocean
Programme Background
Following the appointment of Dr. Daniel Feltham as BAS Reader in Polar Oceanography on 1 Sept 2005, this programme is being recast as a programme in theoretical and computational physical polar oceanography. By explicit design, the programme will make use of the data and expertise in BAS and CPOM relating to oceanic conditions, sea ice, and ice shelf melting.
The ocean absorbs most of the solar energy input to the Earth and its large specific heat capacity and the long duration of its major circulations make its impact on the global climate system significant and complex. The global circulation of the ocean is dominated by the circulation of deep water over decades to millenia.
Deep water formation occurs in polar latitudes and the densification of surface waters to produce deep water due to changes in temperature (cooling) and changes in salinity typically involve interactions with ice. In both the Arctic and Antarctic, the ocean is weakly stratified so that small changes in surface conditions can cause downwelling. In the Labrador and Greenland Seas, cold winds densify surface waters, which have been modified by sea ice export from the Arctic Ocean, to form North Atlantic Deep Water (NADW). In the Antarctic, and particularly the Weddell and Ross Seas, the interactions between sea ice, ice shelves, and surface waters are intricate and result in the formation of Antarctic Bottom Water (AABW).
The densification of Arctic continental shelf waters due to sea ice production is believed to play an important role in the formation and maintenance of the Arctic halocline. The halocline provides a barrier to warm Atlantic water melting the underside of sea ice in the Arctic, and is a source of relatively fresh water that may weaken deep water formation in the Greenland and Norwegian Seas. A reduction in deep water formation would reduce the intensity of the Northern Drift, with a concomitant lowering of temperatures in Western Europe. Understanding and predicting changes in deep water formation requires a detailed understanding of the relationships between the polar ocean, sea ice, ice shelves, and freshwater sources such as river discharges, ice bergs, and ice sheet melt.
The ocean affects the sea ice cover and ice shelves. The oceanic mixed layer determines conditions under which sea ice forms, melts, and moves, and plays a complex role in polynyas and leads. The presence of warm waters is believed to be responsible for the rapid melting of the Pine Island shelf system in Antarctica, but in other locations interactions between the ocean and ice shelves result in the formation of Ice Shelf Water, an important component of AABW.
Understanding the observed rapid changes in the Arctic sea ice cover, and the West Antarctic Ice Sheet (see the related programmes) requires knowledge of the role played by the ocean.
The programme's focus is to investigate the role of topography, buoyancy and phase change in determining the dynamics of the polar ocean and its interaction with ice shelves, sea ice and the atmosphere. These investigations will be performed using primitive equation ocean models, with and without coupling to other climate components, analysis of oceanographic data, and process studies designed to elucidate fundamental mechanisms and interactions. The modelling activities will focus on particular regions of the Arctic and Antarctic observed to be rapidly changing, and where data is available, in order to provide calibration and validation of the models.
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