As massive atmospheric rivers set their sights on the West Coast, the impacts they bring are far from uniform. While some events deliver much-needed rainfall and snowfall, others unleash devastating floods and landslides. It has become increasingly clear that climate change will play a significant role in shaping the behavior of these moisture-laden phenomena as they make landfall, with effects varying along the coast.
Atmospheric rivers, characterized by long plumes of moisture carried by tropical winds spanning thousands of miles, play a crucial role in supplying roughly half of the annual precipitation in the Western United States. These phenomena can generate staggering amounts of precipitation, with the potential to dump up to 100 inches of snow in the Cascades and Sierra Mountains within a mere week. The sheer volume of water they transport is astounding – a robust atmospheric river can move as much water vapor as 15 times the average flow of liquid water at the mouth of the Mississippi River.
Contrary to popular belief, atmospheric rivers are not confined solely to the West Coast of the U.S. – they occur worldwide, with an average of four to five active atmospheric rivers existing simultaneously across the globe. However, during a typical winter, around 24 atmospheric rivers make landfall along the U.S. West Coast, underscoring their significant impact on the region.
A recent study spearheaded by scientists at the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR) has shed light on how climate change is reshaping atmospheric river events, particularly in and around Southern California. In a warming climate, heightened evaporation of ocean waters is set to substantially influence atmospheric rivers in these regions. Along the northern stretches of the West Coast, rising temperatures in both the ocean and atmosphere will exert the greatest influence on atmospheric river behavior.
Christine Shields, a scientist at NSF NCAR and co-lead author of the study, highlighted the contrasting responses expected between the Southern California coast and the Pacific Northwest. She emphasized the nuanced regional impacts of climate change on atmospheric rivers, emphasizing that a one-size-fits-all approach does not apply to these dynamic phenomena.
Forecasts indicate a marked shift in atmospheric river patterns, with potential consequences for the millions of residents who regularly face these events. By the year 2100, experts predict that atmospheric rivers along the Pacific Northwest could amplify flooding risks by significantly elevating ocean water levels if greenhouse gas emissions continue at current rates. Southern California, on the other hand, is projected to experience heightened storm-driven water surges, though less drastic than those anticipated for the Pacific Northwest.
The influence of climate change on storm systems, as evidenced by increasingly intense hurricanes, extends to atmospheric rivers. In a warming world, storms have the capacity to hold more moisture, a phenomenon mirrored in atmospheric rivers. This increased moisture content in powerful weather systems like atmospheric rivers poses a heightened threat to communities, necessitating proactive adaptation and planning measures.
Weather.com’s Jennifer Gray, a seasoned weather and climate writer, has been at the forefront of
