The North Atlantic Ocean can be defined as the waterbody that stretches from southern Iceland in the north to the equator in the south. It is bordered in the north by the Arctic Ocean, as well as many other smaller water bodies including the North, Labrador, Sargasso and Caribbean Seas. The surface waters of the North Atlantic Ocean have a higher salinity than any other ocean in the world.
The Mid-Atlantic Ridge, the longest mountain range in the world, runs through the centre of the Atlantic Ocean from Iceland to the Bouvet Islands. The Mid-Atlantic Ridge is the separation point of the tectonic plates that once held the supercontinent Pangaea together around 180 million years ago. The movement of these tectonic plates caused the initial separation of the continental landmasses and created the space between North and South America and Europe and Africa that is now the Atlantic Ocean. Located in the western Caribbean is the deepest point in any of the world’s oceans, the Puerto Rico Trench, which reaches depths of around 8,648 metres.
The origins of the North Atlantic islands are diverse, with some forming from tectonic plate movements that separated the islands from the main continental landmass, some from the accumulation of volcanic material and many from the build-up of dead coral and other organic matter. From the biodiverse tropical Caribbean islands in the south-west to the barren Arctic islands of the north-east, the islands of the North Atlantic Ocean are extremely varied in their appearance, geographical features and biological richness. As with other islands around the world, the isolated nature of many of the North Atlantic islands has facilitated the evolution of numerous endemic species, although some younger islands have very low levels of endemism. The climate of marine areas in the North Atlantic varies greatly between the tropical coral reefs and warm waters of the south to the sub-zero Arctic conditions of the north.