When an iceberg reaches warm waters, the new climate attacks it from all sides. On the iceberg surface, warm air melts snow and ice into pools called melt ponds that can trickle through the iceberg and widen the cracks.
Most icebergs actually contain a lot of air. Far from being the solid blocks of ice many people imagine, icebergs are riddled with billions of tiny, trapped air bubbles, giving the huge bergs their white appearance. Another aspect is the salinity of the seawater. Icebergs are made from fresh water. Because of the dissolved salts in ocean water, it is denser than freshwater. Salty ocean water weighs 1.025 grams per cm3, making the iceberg even easier to float.
Icebergs are formed when few chunks of ice calve, or break off, from glaciers, ice shelves, or a larger iceberg. These icebergs travel with ocean currents, across the oceans or sometimes smashing up against the shore or getting caught in shallow waters.
Usually, when an iceberg reaches warm waters, the new climate attacks it from every side. On the surface of the iceberg, warm air (from the surroundings) melts the snow and trickles through the iceberg to widen the cracks. At the same time, warm water laps at the iceberg edges, melting the ice instantly and causing chunks of ice to break off. (Study "Change in states" here)