Atmospheric Rivers Have Moved Closer to the Poles in 40 Years. Scientists Reveal How This Impacts Weather

The adverse effects of climate change and global warming can be most dramatically observed on the extreme poles of Earth– the North and South polar regions in the Arctic Ocean and Antarctica, respectively. Even minor shifts in the global temperature result in ice melt and disbalances in the delicate polar ecosystem. Now, scientists have discovered that atmospheric rivers above the Earth’s surface have moved closer to the poles in the past 40 years. They fear such changes may impact the weather patterns and rainfall across the globe leading to unprecedented events, as per the study published in the journal Science Advances.

For those unversed, atmospheric rivers are long, narrow regions in the atmosphere, resembling rivers, that transport water vapor. According to NOAA, they can be over 1,000 miles long and up to 375 miles wide, flow in the direction of air, and carry the same amount of water vapor as the Mississippi River at their mouth. Atmospheric rivers take up water vapor from tropical regions and carry it across the world affecting rain and snowfall levels, particularly in cooler regions. However, the study stated that warming climates due to global warming over the years have contributed to the frequency and intensity of extreme weather patterns, which also include the movement of atmospheric rivers. 

Researchers at the University of California, Santa Barbara have estimated a 6- to 10-degree shift of the atmospheric rivers toward the poles over a time span of four decades. As a result, the areas affected by the water vapor of these rivers have also moved farther downstream, meaning farther north in the Northern Hemisphere and farther south in the Southern Hemisphere. The scientists are not sure about the chain of events that may have caused the shift, however, suggest that cooling in the eastern tropical Pacific over time is an underlying cause of the rivers moving polewards. The world’s oceans are likely to withstand unprecedented consequences due to the AR shifts.

Pineapple Express is one of the famously known atmospheric rivers that play a pivotal role in the moisture levels of the West. It is responsible for fifty percent of the rain and snow on the US West Coast. The Pineapple Express delivers moisture from the tropical Pacific around Hawai’i towards the west coast of the US and Canada, causing heavy rainfall in regions including California, Oregon, Washington, and British Columbia. As a matter of concern, the atmospheric rivers moving closer to the poles can have a drastic impact on global weather patterns as several regions rely on the precipitation from these atmospheric water vapor streams. 

Droughts and heatwaves could turn into a common phenomenon in those areas whereas others may witness heavy rainfalls leading to floods and cyclones. Besides rain and flooding, the Pineapple Express also has a positive effect on snowpack increases. For instance, the winter storms caused by a series of ARs on the US West Coast in December 2010 also contributed to the snowpack in Sierras, per the NOAA report. To surmise, dry regions will have even scarce rainfall while wetter regions will experience even wetter weather. Therefore, it is essential and a need of the hour to deduce the causes behind these poleward shifts of the ARs and prepare for the adjacent consequences incoming.