Dominion Post: Scientists fear a giant Antarctic ice shelf threatened by global warming will help spark a rise in sea levels if it collapses. The Wilkins Ice Shelf is being held together by a rapidly shrinking strip of ice, now just 500 metres wide at its narrowest point. Experts say it could break up at any time. Ice shelves are floating extensions of ice sheets, formed as a sheet hits the coast and spreads on top of the sea. As the ice hits an island or bay it becomes trapped. The Wilkins …