With weaker easterly winds, the ocean cooling effect was also limited. The ocean temperature response was quite strong. Low-pressure areas spin counter-clockwise, so this forces an opposite wind pattern, weakening the easterly winds and their cooling effect. Going into mid-April, the low-pressure area in the subtropics intensified. The low-pressure system in the subtropics has weakened the trade winds, limiting its usual cooling effect, and allowing for higher than normal temperatures. Warmer than normal waters emerged around the coast of Spain and northwest Africa.
Looking at the ocean temperature anomalies for this period, we can see the onset of an oceanic warming event in the image below. The pressure systems are reversed, with a dominant high now in the far North Atlantic, and a low-pressure system down in the subtropics. You can see that this looks quite different from the average pressure map we have shown earlier up in the article. On the image below we have the early April pressure anomalies in the North Atlantic. This way, it will be easier to understand how pressure changes can affect ocean temperatures. Winds are driven by the changes in air pressure, so it is important that we look at the pressure patterns in the North Atlantic since April. As a result, the trade winds were weaker across the subtropical North Atlantic ocean, allowing an onset of a stronger than usual warming of the ocean surface. In April 2021, changes in pressure patterns have initiated a change in the strength of the trade winds. Notice the strong warm ocean current up the eastern coast of the United States. The trade winds cool the ocean surface from West Africa down towards the tropical Atlantic.
Notice how the ocean temperatures are quite cooler in the eastern Atlantic, compared to the western side. SPRING 2021 ATLANTIC PRESSURE AND WARMINGīelow you can see the ocean surface temperature analysis from around a week ago. But weaker trade winds can mean the opposite, leaving calmer waters with less mixing, allowing the ocean temperatures to rise. But more importantly, they also affect the ocean currents and can cause the deeper, colder water to upwell to the surface of the ocean. As they blow across the ocean, they can cool the surface of the ocean, by transport cooler air. The trade winds are easterly/northeasterly winds. Especially noticeable is the warmup from April into May. There you can see fast changes in temperature anomalies, due to the changes in the strength of the trade winds. Be aware of the ocean area from the southeast United States to western Europe. We produced a high-resolution video, which shows the Atlantic ocean temperature anomalies from late winter to May 2021. This helps to explain the direction of the trade winds, as a high-pressure system spins clockwise. There is a low-pressure dominant in the subpolar North Atlantic. The image shows the persistent high-pressure system in the subtropical North Atlantic. We produced another 40-year average, this time for sea level pressure in the late winter to spring period. You can also see the clockwise circulation in the North Atlantic. This nicely reveals the prevailing easterly trade winds. In the North Atlantic, the circulation pattern is clockwise, as a high-pressure system is present in that region.īelow you can see an image that shows the average surface winds in the past 40 years. The image below shows the main near-surface wind directions, with global trade winds in yellow and red color. The trade winds were named by the crews of sailing ships that depended on the winds during westward ocean trade crossings. Its average speed is about 5 to 6 meters per second (11 to 13 miles per hour) but can increase to speeds of 13 meters per second (30 miles per hour) or more. Trade winds often produce partly cloudy sky conditions, characterized by shallow cumulus clouds, or clear skies that make trade-wind islands popular tourist resorts. They are stronger and more consistent over the oceans than over the land. Trade winds are the prevailing easterly winds that circle the Earth near the equator.
All of this motion is caused by pressure changes and winds, which play a crucial role in the connection between the oceans and the atmosphere. Using satellites, we can track the motion of clouds and pressure systems around the world. Global weather is in a constant flow, connected through space and time. In the past weeks, warmer than normal ocean waters were detected in the subtropical North Atlantic ocean, which is known historically to have an important connection to the Atlantic hurricane season. The Atlantic Ocean is one of the key global areas, that greatly affects the weather and climate in the United States and Europe.