North Atlantic's Major Current System - Threatened by Climate Change

The Atlantic Meridional Overturning Circulation (AMOC) is a crucial element in the Earth’s climate system and is influenced by both atmospheric and thermohaline factors. In this article, Pitamber Kaushik highlights how increased ocean heat content and greater cold freshwater inputs from melting Arctic ice sheets caused by climate change threaten the AMOC. In the event of an AMOC collapse, more pronounced extreme weather events including heat waves, cold waves, drought, and flooding are anticipated, which would create a vicious cycle of climate crisis. Keep reading to learn more…

The ocean’s thermohaline circulation, a system of various ocean currents and water-mass conveyors, is crucial for distributing heat, salinity, minerals, dissolved gases, and nutrients around the globe, sustaining a habitable planet. In the Atlantic, this circulation, a continuous conveyor-belt of interconnected currents, is known as the Atlantic Meridional Overturning Circulation (AMOC).

The AMOC is a vital component of the Earth’s global ocean circulation, and it encompasses a network of surface and deep currents within the Atlantic Ocean. It is characterized by the northward movement of warm, saline surface waters and the southward flow of colder, deep waters. These two distinct limbs constituting the circulation are connected by overturning processes occurring in the Nordic and Labrador Seas as well as the Southern Ocean. The warm, salty, and dense northbound water from the tropics cools as it slowly loses heat to the atmosphere and gradually descends as it approaches the northern reaches of the Atlantic, moving back south past the equator into the southern torrid zone where it starts to heat up again, thus completing the cycle. This is made possible by an intricate interplay of temperature and salinity which have counteracting effects on density leading to layering. The AMOC thus transports heat northward from the tropics, preventing overheating in those regions, thus maintaining climate balance. This circulation system has been instrumental in maintaining Europe’s climate stability over millennia. The AMOC is a crucial element in the Earth’s climate system and is influenced by both atmospheric and thermohaline factors. Like other oceanographic systems, it exhibits variations on annual, decadal, and centennial timescales.