Specific oceanographic currents constitute the AMOC in the North Atlantic.
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Scientific literature confirms that the Atlantic Meridional Overturning Circulation (AMOC) consists of specific ocean currents that transport warm water northward in upper layers and cold water southward in deeper layers.
The North Atlantic Ocean is vital to Earth’s climate system. Scientific investigations have identified the Atlantic Meridional Overturning Circulation (AMOC) as a significant factor influencing global climate change. This circulation involves ocean currents that carry relatively warm, salty water northward in the upper layers, while transporting colder, less salty water southward in the deeper layers. The AMOC relies on descending water at deep convection sites in the high-latitude North Atlantic (NA), where warmer water cools, becomes denser, and sinks. A concern regarding the AMOC is that the freshening of the sea surface at these convection sites can slow it by inhibiting deep convection. Researchers have used oceanographic observations and models of Earth’s climate and ocean circulation to investigate decadal shifts in the AMOC and NA. We examined these findings to provide insights into these models, observational analyses, and palaeoceanographic reconstructions, aiming to deepen our understanding of AMOC variability and offer potential predictions for future climate change in the North Atlantic. While the influence of high-latitude freshwater is crucial and may slow the AMOC, evidence also shows a complex feedback mechanism. In this mechanism, the negative feedback from wind stress can stabilize the AMOC, partially counteracting the positive feedback effects of freshwater at high latitudes. Although some models predict significant shifts in AMOC dynamics, suggesting imminent and possibly severe deceleration, recent observational research presents a more cautious view. These data analysis studies acknowledge changes, but highlight the robustness of the AMOC, particularly in its upper arm within the Gulf Stream system. While it cannot be entirely dismissed that the AMOC may reach its tipping point within this century, an analysis of data concerning the decadal variability in the AMOC’s upper arm indicates that a collapse is unlikely within this timeframe, although significant weakening remains quite possible. Furthermore, deceleration of the AMOC’s upper arm could lead to less stable and more vulnerable North Atlantic Ocean climate patterns over extended periods.
water basins across the global ocean. Its better-known northern counterpart is the Atlantic meridional overturning circulation (AMOC). This circulation
Southern Ocean overturning circulation (sometimes referred to as the Southern Meridional overturning circulation (SMOC) or Antarctic overturning circulation) is the southern half of a global thermohaline circulation, which connects different water basins across the global ocean. Its better-known northern counterpart is the Atlantic meridional overturning circulation (AMOC). This circulation operat
Southern Ocean overturning circulation (sometimes referred to as the Southern Meridional overturning circulation (SMOC) or Antarctic overturning circulation) is the southern half of a global thermohaline circulation, which connects different water basins across the global ocean. Its better-known northern counterpart is the Atlantic meridional overturning circulation (AMOC). This circulation operates when certain currents send warm, oxygenated, nutrient-poor water into the deep ocean (downwelling), while the cold, oxygen-limited, nutrient-rich water travels upwards (or upwells) at specific points. Thermohaline circulation transports not only massive volumes of warm and cold water across the planet, but also dissolved oxygen, dissolved organic carbon and other nutrients such as iron. Thus, both halves of the circulation have a great effect on Earth's energy budget and oceanic carbon cycle, and so play an essential role in the Earth's climate system.
Southern ocean overturning circulation itself consists of two parts, the upper and the lower cell. The smaller upper cell is most strongly affected by winds due to its proximity to the surface, while the behaviour of the larger lower cell is defined by the temperature and salinity of Antarctic bottom water. The strength of both halves had undergone substantial changes in the recent decades: the flow of the upper cell has increased by 50–60% since 1970s, while the lower cell has weakened by 10–20%. This has been partly due to the natural cycle of Interdecadal Pacific Oscillation, and climate change has played a substantial role in both trends, as it had altered the Southern Annular Mode weather pattern, while the massive growth of ocean heat content in the Southern Ocean has increased the melting of the Antarctic ice sheets, and this fresh meltwater dilutes salty Antarctic bottom water.
As the formation of dense and cold waters weakens near the coast while the flow of warm waters towards the coast strengthens, the surface waters become less likely to sink downwards and mix with the lower layers. Consequently, ocean stratification increases. One study suggests that the circulation would lose half its strength by 2050…
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