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Climate Change and the European Water Dimension - Agri ...

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Nor<strong>the</strong>rn Hemisphere <strong>the</strong>rmohaline circulation (THC)<br />

THC is <strong>the</strong> circulation in <strong>the</strong> Atlantic of warm surface water flowing northwards <strong>and</strong><br />

cold saline water flowing southwards at depth. This ‘conveyor belt’ has an important<br />

influence on <strong>the</strong> temperature of <strong>the</strong> surface water in <strong>the</strong> North Atlantic <strong>and</strong> causes<br />

warming of <strong>the</strong> atmosphere that contributes to give <strong>the</strong> relatively mild winters in<br />

Western Europe. This circulation is driven by density differences that are caused by<br />

temperature <strong>and</strong> salinity differences. <strong>Change</strong>s in <strong>the</strong> buoyancies of surface waters<br />

can have an important impact on this mechanism, <strong>and</strong> such changes can in several<br />

ways be caused by <strong>the</strong> effects of global warming, e.g., by changes in precipitation<br />

<strong>and</strong> melting of sea-ice. Most models show a weakening of <strong>the</strong> THC, however none of<br />

<strong>the</strong>m predict a complete shutdown within <strong>the</strong> 21s t century. All models predict that <strong>the</strong><br />

increased greenhouse warming over Europe will more than compensate for <strong>the</strong><br />

reduced heat transport by <strong>the</strong> THC.<br />

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