What is the Meridional Overturning Circulation and why is it important?

<p>The Meridional Overturning Circulation (MOC) is a system of ocean currents that circulate water across the globe. Just as blood circulation transports oxygen, nutrients and heat throughout our bodies, the MOC moves oxygen, nutrients, heat and carbon throughout the oceans, regulating our climate and sustaining ocean life.</p> <p> </p> <p>The strength of the MOC depends on changes in seawater density, which is controlled by temperature and salinity – cold or salty water is denser and sinks, while fresh or warm water is less dense and tends to stay at the surface. The North Atlantic and the Southern Ocean are two key regions of the MOC where dense, cold, salty water sinks.</p> <p> </p> <p>However, with climate change and melting ice sheets in Antarctica and Greenland, significant amounts of freshwater are added to these regions, disrupting the formation of dense water and weakening the MOC. Climate and ocean model simulations alongside observations suggest that the MOC has weakened in both the North Atlantic and the Southern Ocean over the past several decades. </p> <p> </p> <p>The MOC is expected to keep slowing in the future and could weaken by nearly 50% within the coming century, with significant consequences for our climate. If the circulation were to shut down – which is unlikely to happen this century, but is projected to occur for unmitigated climate change beyond 2100 – these impacts could become even more severe.</p> <p> </p> <p>Here, we explore the importance of the MOC and discuss the implications of its weakening or potential shutdown under future climate change.</p>