Atmospheric rivers form around the world as narrow bands of moisture that bring heavy rain and storms. It is noteworthy that these rivers move towards higher latitudes, changing weather conditions all over the world. Over the past four decades, atmospheric rivers have moved about 6-10 degrees toward either pole. When these systems reach the Arctic, melting sea ice affects climate worldwide.
How do atmospheric rivers affect our world?
From the fertile lands of California and Southeast Asia to the coasts of Spain and Portugal, atmospheric rivers provide more than half of the annual flow. They can provide up to 50% of annual precipitation in California. A series of winter storms from these rivers could bring enough rain and snow to end the drought, as seen in parts of the region in 2023. These rivers absorb moisture from the tropics by bending towards the poles due to the displacement of the jet stream.
Behavior of atmospheric rivers
As with all natural phenomena, no two atmospheric rivers are alike. But their collective behavior is of great interest to climate scientists who study these patterns closely. These systems generally occur in the extratropics between 30 and 50 degrees latitude in both the northern and southern hemispheres.
Over the last four decades, river activity has changed from 30 degrees, and more intense activity is now observed at 50 degrees latitude. Specifically, this change means an increase in atmospheric rivers that bring heavy rain to places like British Columbia and Alaska, increasing the risk of flooding and altering local weather patterns.
Displacement of atmospheric rivers
So why do atmospheric rivers move towards the poles? The main reason for this is the cooling trend in sea surface temperatures in the eastern tropical Pacific since 2000. This cooling effect associated with La Niña conditions affects atmospheric circulation worldwide, pushing rivers poleward.
When atmospheric rivers drift towards the poles, they significantly affect the local climate. In subtropical regions where these rivers become less common, longer droughts and water shortages may become the norm. At the same time, more intense rains and floods may occur in higher latitudes. If atmospheric rivers visit the Arctic more frequently, we could witness rapid melting of sea ice, which would increase global warming and affect Arctic fauna.
Preparation for what’s to come
Although the changes mainly reflect natural events, human-caused global warming also plays a role. As the Earth warms, the atmosphere can hold more moisture, causing atmospheric rivers to form more frequently and with greater intensity.
These future changes are difficult to predict, largely because it is difficult to predict the oscillations between El Niño and La Niña, which strongly affect where these atmospheric rivers flow. Scientists such as Tsinghua Ding at the University of California at Santa Barbara have closely studied the poleward shift of atmospheric rivers. By understanding these changes, they hope to improve climate models and better predict future rainfall and water supplies. Consequences for wildlife
The shift of atmospheric rivers towards the poles affects not only humans but also ecosystems and wildlife. As more rainfall reaches northern regions, plants and animals unaccustomed to such heavy rainfall may face great difficulties. For example, in polar regions, a change in rainfall can alter plant growth, disrupting the local natural balance. This change could also threaten animals that need fixed habitats for nesting and feeding, such as migratory birds.
Unpredictable ecosystem changes
In regions where atmospheric rivers become rare, long periods of drought may occur in ecosystems that depend on continuous rainfall. For example, forests in warmer regions may experience more droughts, increasing the likelihood of wildfires and harming biodiversity. Aquatic habitats may also be damaged as less reliable water sources make it harder for fish and other creatures to thrive.
To protect nature, conservation efforts must adapt to these changes. Protecting sensitive plants and animals in areas undergoing change is vital to preserving biodiversity. Ongoing research will play an important role in understanding these impacts and developing strategies to help ecosystems cope with climate change. The study was published in the journal Science Developments.
Source: Port Altele
