number of factors, ocean currents and water movements play a big role. Some currents take warm water away from the equator, influencing coastal climates near the poles. Others take colder water from the poles or the deep ocean and move it towards the equator, creating cooler coastal climates.
The main driver of ocean surface currents is wind. However, the earth’s rotation and continental positioning also play a big role. Deep sea currents are mainly induced by density differences between the surface water and the deep water. A lot of continents or large landmasses have coastal currents which transport nutrients and heat, while the deep oceans have various currents which differ depending on their location and the surrounding geography¹.
Oceanic currents influence the climate due to their ability to transport heat. The ocean itself acts as a vital climate buffer, as it absorbs the majority of the excess atmospheric heat which is trapped by climate change. Some figures suggest that around 90% of the excess heat trapped through global warming is absorbed by the ocean, with negligible temperature changes². North or South moving currents have the ability to transport water huge distances. This water can then cool or warm the surrounding air, which indirectly influences the temperature of the nearby land. For example, the climate of coastal areas of Western Europe are a lot milder than would be expected for this altitude. This is due to the ‘Gulf Stream’, which carries warm water from the Atlantic Ocean in a northerly direction¹.
Due to various factors, including evaporation and surface cooling, surface water can often become denser than the deeper water. This can create vertical, circular currents which are often referred to as “convective currents” or “convective turning”³. Often, this type of current acts in a way that it takes warm water from the equator, moves it poleward, where it cools and sinks, completing the circular current. This disperses heat from near the equator towards the poles, making some areas a lot warmer than they would otherwise be.
Without circular currents like these, may of the northern and southern extremities of human habitation would be rendered too cold to live in. Additionally, without this method of heat dispersal, areas near the equator would become a lot hotter, and perhaps even become inhabitable. This would drastically change the world as we know it¹.
An Example of the Huge Impact Even a Small Change in Currents Could Have
In a study by Manabe and Stouffer (1993), the impact of increasing atmospheric carbon dioxide concentrations was analysed. They found that with significant CO2 concentration increases, the impact of the Atlantic convective currents was significantly decreased. With a four-fold increase in CO2, it was predicted that the current would begin to slow, and eventually stop over a period of 100 to 200 years. This would cause the climate of much of Western Europe to change, and would impact billions of people world-wide. This little known fact about global warming gives just one more example of its hidden effects and the associated unexplored issues⁴.