The ocean current known as the Gulf Stream carries warm water from the Caribbean up along the shores of North America and Europe. If a large mass of warm water currently trapped beneath the ice of the Arctic were to mix with salt water below it, its influence on ocean temperatures would be unpredictable, say scientists, potentially disrupting the favorable ecosystems provided for by the Gulf Stream. The warm water mass is thought to be caused by melting glaciers due global warming, the phenomenon of rising sea and air temperatures during the last half century.