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GEOENGINEERING DOWNWELLING OCEAN CURRENTS: A COST ASSESSMENT
S. ZHOU1 and P. C. FLYNN2
1Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, Canada
2Poole Chair in Management for Engineers, Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta T6G 2G8, Canada
E-mail: [email protected]
Abstract. Downwelling ocean currents carry carbon into the deep ocean (the solubility pump), and play a role in controlling the level of atmospheric carbon. The formation of North Atlantic Deep Water (NADW) also releases heat to the atmosphere, which is a contributor to a mild climate in Europe. One possible response to the increase in anthropogenic carbon in the atmosphere and to the possible weakening of the NADW is modication of downwelling ocean currents, by an increase in carbon concentration or volume. This study assesses the costs of seven possible methods of modifying downwelling currents, including using existing industrial techniques for exchange of heat between water and air. Increasing carbon concentration in downwelling currents is not practical due to the high degree of saturation of high latitude surface water. Two of the methods for increasing the volume of downwelling currents were found to be impractical, and four were too expensive to warrant further consideration. Formation of thicker sea ice by pumping ocean water onto the surface of ice sheets is the least expensive of the methods identied for enhancing downwelling ocean currents. Modifying downwelling ocean currents is highly unlikely to ever be a competitive method of sequestering carbon in the deep ocean, but may nd future application for climate modication.
1. Introduction
Oceans play a major role in climate by two primary mechanisms. First, surface currents transport heat from lower to higher latitudes, where it is released to the atmosphere. In particular, the cooling of surface currents in the North Atlantic contributes to the formation of North Atlantic Deep Water (NADW), and the associated heat release is one factor in the mild climate in northern Europe that enables population at a higher latitude than on other continents (see, for example, Broecker (1997)). The extent to which European climate is inuenced by ocean storage, ocean transport, and atmospheric transport has been the focus of recent studies that suggest the impact of ocean transport mechanisms have been overestimated in the past (see,...