In 2015, two sites on the west coast of North America saw sea-level rise of around half a metre during a couple of strong atmospheric river events. Although the boosts lasted for only five to seven days, the average sea-level rise from January to March 2015 at Neah Bay in Washington would be 6 cm lower without the effect of atmospheric rivers, according to analysis.
The study suggests that any long-term changes in atmospheric rivers could impact sea-level variation along the coast.
Toshiaki Shinoda at Texas A&M University, US, and colleagues demonstrated that atmospheric rivers above the US west coast affect the ocean and fluxes between the ocean and atmosphere. The south-westerly winds associated with these atmospheric rivers, they found, generate surface ocean currents that pile up water along the west coast of North America, rapidly increasing sea level.
Atmospheric rivers are relatively long and narrow regions of the atmosphere that often release water vapour as precipitation when they move from above the ocean to the land. The most well-known is the “Pineapple Express”, which transports moisture from the central Pacific to the west coast of the US.
Research on these “rivers in the sky” has increased over recent years as their importance for global water transport has become apparent; they’re responsible for most of the poleward water vapour transport at middle and high latitudes as well as extreme weather such as heavy precipitation.
Shinoda and colleagues examined two strong atmospheric river events observed during the 2015 field campaign for the CalWater Precipitation, Aerosols and Pacific Atmospheric Rivers Experiment. They used data products including high-resolution ocean reanalysis and tide gauges.
To complement these case studies, the researchers analysed a dataset of 1584 atmospheric river events in the northeast Pacific from 2011-2015. This established that the oceanic processes found in the CalWater 2015 case studies are found in most atmospheric river events.
Shinoda and colleagues published their findings in Scientific Reports.
