Atlantic heat conveyor
The Atlantic heat conveyor, also known as the Meridional Overturning Circulation (MOC), is a crucial oceanic system that transfers heat from the equatorial regions of the Atlantic Ocean northward to the polar areas. This phenomenon is largely driven by the Gulf Stream, a significant surface current that originates in the Gulf of Mexico and flows along the eastern coast of the United States before splitting into the North Atlantic Drift and the Azores current. The movement of water within the Gulf Stream transports vast amounts of heat, influencing climate patterns, particularly in northern Europe, which experiences milder temperatures than other regions at similar latitudes.
The Atlantic heat conveyor is integral to understanding global climate dynamics, especially in the context of climate change. Concerns have been raised about the potential impact of global warming on this system, particularly the influx of freshwater from melting Arctic glaciers, which could disrupt the northward flow of the Gulf Stream. This disruption might lead to a cooling effect in the Northern Hemisphere, particularly in Europe, despite the overall trend of global warming. Scientists are divided on the current status of the MOC, with some suggesting it has slowed down while others present conflicting data. Overall, the future of the Atlantic heat conveyor is pivotal for predicting climate-related changes, including altered precipitation patterns and increased storm intensity.
Atlantic heat conveyor
Definition
The Atlantic heat conveyor transfers heat from the equator northward to the polar region of the Atlantic Ocean, through the Meridional overturning circulation (MOC). Because the Earth is a sphere, incoming solar radiation heats the surface of the Earth unevenly, with the equator receiving a greater amount of heat per surface area than the polar regions. This uneven heating creates temperature gradients that drive atmospheric currents (wind) and surface currents in the ocean.
In the Atlantic Ocean, the is the surface current that transports heat from the equator to the polar region. The Gulf Stream is a western boundary current that originates in the Gulf of Mexico and travels north along the east coast of the United States and Newfoundland. Near 50° north, the Gulf Stream splits into two branches: the (or North Atlantic current) and the Azores current. The North Atlantic drift (NAD) flows northeastward toward northern Europe, while the Azores current flows east toward the Azores and then south as the Canary current. The Gulf Stream is a large, fast-moving current, transporting between 30 million and 150 million cubic meters of water per second. This flow of water transports approximately 1.4 petawatts (1.4 1015 watts) of heat per year. As the Gulf Stream moves north and mixes with cooler from the poles, it releases this heat.
The Atlantic heat conveyor may be responsible for maintaining a milder climate in northern Europe, as compared to Newfoundland, which is located at the same latitude. However, this idea has been challenged by scientists, who hypothesize that atmospheric heat transport is more important in maintaining a mild climate in northern Europe than is oceanic heat transfer.
Significance for Climate Change
The Atlantic heat conveyor delivers a large amount of heat to the Arctic region from the equator, making it an important component of the global climate system and of any changes in that system. One consequence of global warming is the melting of glaciers in the Arctic, which would lead to a large of freshwater into the surface waters of the Greenland Sea. This cap of freshwater could serve as a barrier to the northward flow of the Gulf Stream, thereby blocking the Atlantic MOC and the heat conveyor. Thus, according to this conceptual model, projected global warming would actually lead to a localized cooling of the Northern Hemisphere, particularly Europe.
In 2005, scientists from the National Oceanography Center presented data to suggest that the Atlantic MOC had slowed during the late twentieth century. These data were subsequently challenged by other scientists, who presented different data sets that showed no MOC slowdown. Despite the controversy regarding whether such a slowdown has occurred, computer models consistently indicate that a shutdown of the Atlantic heat conveyor could lead to a lesser warming or even cooling in the Northern Hemisphere as a result of global warming. Geologic evidence suggests that the Younger Dryas, a time of that lasted from 12,800 to 11,500 years before present, may have been caused by MOC collapse in the Atlantic because of a large influx of freshwater to the North Atlantic from the emptying of glacial Lake Agassiz.
The hypothesis of the Atlantic heat conveyor has been criticized by scientists from the Lamont-Doherty Earth Observatory, who believe that the atmospheric transport of heat and the slow response time of the ocean are the main reasons for Europe’s mild climate. Additionally, they point to long waves in the atmosphere, created as air masses flow around the Rocky Mountains, as a third potential cause of a mild European climate. According to this hypothesis, global warming will not stop the Atlantic heat conveyor, nor will it lead to a cooling of Europe. This view, however, was not widely held among climate scientists or policymakers. According to the National Centers for Environmental Information in 2024, climate scientists were concerned that the Atlantic heat conveyor was substantially weakening and could result in catastrophic climate change. This weakening could affect precipitation patterns, result in stronger storms, and increase sea levels along the Atlantic Coast. Some scientists speculated that the Atlantic heat conveyor could shut down as early as 2025.
Bibliography
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"Decades of Data on a Changing Atlanta Circulation." National Centers for Environmental Information, 24 Apr. 2024, https://www.ncei.noaa.gov/news/decades-data-changing-atlantic-circulation. Accessed 11 Dec. 2024.
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