Gulf Stream disruption, illustration. The Gulf stream and its associated currents are warm surface waters (red) that have a key influence on the climate of the northern Atlantic and north-western Europe. The normal flow between surface waters and cold deep waters (blue) is at left. The surface waters cool and sink into the depths at higher latitudes to form the southerly return flow (or North Atlantic Deep Water) that warms and rises further south. At right, this flow is disrupted by fresh water that has melted from the Greenland ice sheet. This North Atlantic warming hole is thought to be caused by climate change. This disruption of ocean currents could cause more extreme weather along with colder winters and summers in north-western Europe. For this illustration with labels, see images C047/4545 and C047/4546.