Nasa discovers how El Niño is changing saltiness of coastal waters across the world

NEW DELHI: In a significant breakthrough, scientists from Nasa’s Jet Propulsion Laboratory (JPL) have revealed how the El Niño phenomenon influences the saltiness, or salinity, of coastal waters around the globe. Utilizing satellite data over a decade, from 2011 to 2022, the team has provided new insights into the intricate relationship between the climate event and changes in coastal water chemistry.
The study, led by ocean physicist Severine Fournier at JPL, has shown that the El Niño Southern Oscillation (ENSO) – encompassing both El Niño and its cooler counterpart, La Niña – plays a significant role in altering salinity levels near coastlines.These changes are directly correlated with variations in rainfall and river discharge patterns caused by ENSO events. For instance, the exceptional El Niño of 2015 led to decreased precipitation over land, reducing river discharge and subsequently increasing salinity levels in coastal areas by a notable margin.
Coastal salinity: A bellwether for climate change
The JPL team’s findings highlight the dynamic nature of coastal zones, where salinity is more than 30 times as variable as in the open ocean. This variability is especially marked at the mouths of large rivers, such as the Mississippi and Amazon, where the influx of fresh water into the ocean can significantly alter salinity. With global warming altering the water cycle and increasing extreme precipitation events, coastal waters stand as key indicators of broader environmental changes. “Given the sensitivity to rainfall and runoff, coastal salinity could serve as a kind of bellwether, indicating other changes unfolding in the water cycle,” Fournier noted.
The pivotal role of satellite technology in tracking these phenomena is underscored by the use of missions such as Aquarius, SMOS (Soil Moisture and Ocean Salinity), and SMAP (Soil Moisture Active Passive). These instruments have enabled scientists to observe sea surface salinity with unprecedented detail and accuracy, even close to coastlines. The comprehensive data collected has shown that coastal water salinity reaches its highest and lowest global averages in March and September, respectively, influenced primarily by river discharge from the Amazon.
This groundbreaking study, published in the journal Geophysical Research Letters, opens up new avenues for understanding the intricate links between climate phenomena like El Niño and the Earth’s water cycle. As the planet faces the challenges of climate change, such research provides crucial insights into the mechanisms at play and the potential impacts on coastal ecosystems and communities.