The North Atlantic oscillation (NAO) is a phenomenon seen in the North Atlantic Ocean. Due to the shrinking angle of sunlight at the poles, a high pressure area at sea level with low heat energy, and in the equatorial regions, on the contrary, a low pressure area of the sea with high heat energy. As a reaction to these pressure zones, metastable pressure zones also occur in the subtropical and sub polar regions. A high pressure around the Azores islands - known as the Azores High Pressure, or Azores High, also around Iceland, a low pressure around Iceland - Iceland low or Iceland low pressure occurs at sea level.