The latest report from the Intergovernmental Panel on Climate Change (IPCC) indicates a concerning development in our world’s oceans. The Atlantic Meridional Overturning Circulation (AMOC), a significant part of the ocean’s interconnected current system, is predicted to lose stability and likely decline throughout the 21st century. This report has far-reaching implications for global climate and weather patterns, raising concerns among scientists worldwide.
About AMOC
The AMOC is a large system of ocean currents and a vital component of the Ocean Conveyor Belt or ThermoHaline Circulation (THC). The AMOC plays an essential role in distributing heat and nutrients across the globe’s ocean basins.
The AMOC operates by transporting warm surface water from the tropics towards the Northern Hemisphere. Upon reaching the North, this water cools and sinks, returning to the tropics and then to the South Atlantic as a bottom current. The Antarctic Circumpolar Current (ACC) then distributes this water to all the ocean basins.
It’s important to note that the ACC is the most substantial current in the Southern Ocean and the only current that flows entirely around the Earth.
Implications of AMOC Decline
A decline or shutdown of the AMOC could have serious consequences for global climates. For instance, without the Gulf Stream (a component of the AMOC), Europe could become significantly colder. This is because the Gulf Stream is responsible for maintaining mild climates on the Eastern coast of North America and Europe.
Additionally, an AMOC shutdown could cool the northern hemisphere, decrease rainfall over Europe and impact the El Nino climate pattern, which describes unusual warming of surface waters in the eastern tropical Pacific Ocean. This could potentially shift monsoon patterns in South America and Africa.
Causes of AMOC Decline
Climate models have consistently predicted that global warming can cause a weakening of the world’s major ocean systems. The AMOC decline has also been linked to the melting of the Greenland ice sheet and increasing freshwater inflow.
In July 2021, scientists noted that an area of the Arctic’s ice, dubbed the “Last Ice Area”, had also melted. The introduction of this fresh water reduces the salinity and density of the seawater, preventing it from sinking and subsequently weakening the AMOC flow.
The Indian Ocean may also contribute to the AMOC slowdown, as could increasing precipitation and river run-off.
Importance of AMOC
AMOC plays a critical role in redistributing heat and regulating global weather patterns. Its potential decline is concerning and likely indicates the approach of a critical threshold beyond which this circulation system could collapse.
About Ocean Currents
Ocean currents exist both at the ocean’s surface and in deep water below 300 meters. These currents can move water horizontally and vertically and occur on both local and global scales. They’re primarily driven by global wind systems powered by solar energy, but other factors like the Earth’s rotation and landform positions also influence these patterns.
Surface Currents and Deep Water Currents
Surface currents like the Gulf Stream or the California Current are responsible for maintaining regional climates. Furthermore, a vast circular system made up of ocean currents, known as a Gyre, spirals around a central point and helps regulate global temperatures.
Unlike surface currents, deep-water currents are caused by density differences in water masses due to temperature and salinity variations, a process known as thermohaline circulation. These currents transport nutrients, oxygen, and heat through the deep ocean.
The Global Conveyor Belt
Density differences also contribute to a global-scale circulation system, referred to as the global conveyor belt. This system encompasses both surface and deep ocean currents that circulate the globe in a 1,000-year cycle. The global conveyor belt’s circulation plays a key role in distributing heat energy, regulating weather and climate, and cycling vital nutrients and gases.
