Walker circulation
Walker circulation refers to a large-scale system of air movement that occurs across the equatorial regions of the oceans, primarily the Pacific, Indian, and Atlantic Oceans. Discovered by Gilbert Walker, it consists of rising warm, moist air in the western parts of these oceans, resulting in wet climates, while cooler, drier air descends in the eastern regions, contributing to arid conditions. This pattern is accompanied by ocean currents that similarly flow from the eastern to the western sides.
The significance of Walker circulation extends into climate dynamics, particularly in the context of events like El Niño and La Niña. A weakening or reversal of the Walker circulation can lead to an El Niño phenomenon, marked by increased ocean temperatures that disrupt marine ecosystems and affect fisheries, particularly in Peru. Conversely, a stronger Walker circulation, known as La Niña, can lead to intensified rainfall and flooding in regions like Australia. Overall, changes in the Walker circulation can have widespread impacts, including variations in rainfall, temperature shifts, and alterations in storm patterns across the globe. Recent studies indicate that this circulation has been weakening, potentially linked to global warming, raising concerns about its future influence on climate.
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Walker circulation
Definition
The was discovered and named for Gilbert Walker. The Walker circulation is a cell of airflow across an ocean along the equator. The most well known cell is across the Pacific Ocean but cells also exist across the Indian and the Atlantic Oceans. In the western Pacific or Atlantic, hot air rises carrying moisture and creating a wet climate. As the air travels eastward, it cools and creates a cooler, drier climate in the eastern Pacific. An ocean current follows the same pattern. The water warmed by the Sun flows to the west. The Indian Ocean Walker cell flows in the opposite direction, making the eastern side the warm, moist climate.
Significance for Climate Change
When a Walker circulation weakens or reverses, an El Niño results. The ocean surface temperature is higher than normal and the normal upwelling of cold water is less if at all. This means that plankton are not brought up to the surface and the fishermen from Peru suffer from small catches of fish that eat plankton. A shift in the Walker cell has also been shown to cause drought and flooding in Australia. An El Niño year may cause the central or eastern region of the Pacific to be as warm as the western Pacific. The ocean around Australia is cooler with less moisture in the atmosphere, which causes a drier eastern and northern Australia. A stronger than normal Walker circulation, called La Niña, can cause severe flooding in Australia as the airflow carries more moisture, the ocean is warmer, and there is more rainfall. This also means more cyclones in Southeast Asia, droughts in South America, and colder winters in North America.
An El Niño year will have fewer hurricanes as strong western winds, normally blocked by the Walker circulation, form and disrupt hurricane formation. The drier western Pacific will include not only Australia but also Indonesia. The western Pacific region, such as Chile and Peru, will have greater rainfall. Canada will have colder temperatures but Europe will have wetter, milder winters. A study by the University of Toronto indicates that a weaker Walker cell has such wide-ranging effects as less summer rainfall in West Africa and in north China and a reduced snow accumulation in southern Himalaya. There is evidence that the Walker circulation has been weakening for most of the twentieth century. An article published in Nature, May, 2006, assets that global warming is the cause of the weakening of the Walker circulation. If the Walker circulation continues to weaken, it will change the world’s climate.
Toda, Masaki, et al. "Walker Circulation Strengthening Driven by Sea Surface Temperature Changes Outside the Tropics." Nature Geoscience, 29 Aug. 2024, doi.org/10.1038/s41561-024-01510-5. Accessed 21 Dec. 2024.
"What Is the Pacific Walker Circulation?" Climate Extremes, 19 Sept. 2023, climateextremes.org.au/what-is-the-pacific-walker-circulation/. Accessed 21 Dec. 2024.