Influence of wind and buoyancy on ocean circulation in the North Atlantic Ocean: insights from turbulence and convection-resolving simulations*

In the Atlantic ocean, the Atlantic Meridional Overturning Circulation (AMOC) transports a huge volumes of water mass and regulates the global climate by transferring an estimated 1.25±0.25 petawatts of heat towards the North Pole. It is also a crucial mechanism in transporting nutrients and carbon dioxide. The Gulf Stream, a part of the North Atlantic gyre, broadly transports heat and large volumes of water northwards, impacting the climate and weather system of western Europe. However, it is still not clear the main driver of the global ocean circulation. Wind has long been regarded as the primary driver of the large scale ocean circulation. Surface buoyancy forcing has also been introduced as another parameter which is able to drive the ocean circulation. In the present work, we investigate the contribution of each wind and buoyancy in driving the meridional overturning and gyre circulations in the North Atlantic Ocean using direct numerical simulations of an idealised ocean concerning both wind and buoyancy forcing. We find out that the buoyancy forcing is the primary driver of the deep overturning circulation. It also contributes in driving the gyre circulation. Thus, weakening the surface buoyancy forcing can decrease the ocean circulation. This is the likely scenario which may happen due to the global warming and increasing the greenhouse effect. The global warming modifies the surface buoyancy forcing which can have significant impact on ocean circulation. It impacts the global climate system and stresses ecosystems.