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Static sea level budget from June 2014 to May 2016. The green dash line and its 1-sigma envelope represent the static sea level estimated from the spherical harmonic solution (change in terrestrial water storage (TWS) expressed in equivalent sea level). The solid green curve represents the change in his TWS for the South American continent. The red curve represents the TWS contribution of North America, the pink curve represents Africa, the light green curve represents Europe, the brown curve represents Asia/Oceania, and the solid gray line represents the contribution of ice sheets to sea level. credit: Geophysical Research Letters (2023). DOI: 10.1029/2023GL104709
A group of oceanographers from the CNRS’s Brest University Institute of Oceanography and Spatial Studies has found evidence suggesting that the unexpected sea level rise between 2014 and 2016 was likely due to a series of El Niño events.
Their study was reported in the journal Geophysical Research LettersWilliam Llovel, Kevin Balem, Soumaia Tajouri, and Antoine Hochet analyzed satellite and ocean sensor data to learn more about the events that led to two years of unexpected sea level rise from 2014 to 2016.
Since 1993, global sea levels have risen by just over 9 centimeters, according to previous studies. Scientists who studied sea level rise during this period found that it was due to climate change and that polar ice was melting. They also use historical data and estimates of future climate change to estimate how much global sea levels will rise in the future.
These estimates suggest that global sea levels will rise by about 4 millimeters per year as ice continues to melt. But then something happened that cast doubt on those estimates. In his two-year period from 2014 to 2016, sea levels rose by about twice as much as expected, or 8 millimeters. Sea levels have since returned to previously estimated rates, suggesting that 2014-2016 was an anomaly. In this new effort, the research team set out to understand the cause of this huge and sudden rise in sea levels.
To learn more, researchers combed through data from the years leading up to the anomaly, the time of the sudden rise, and the years after. They looked at both satellite data and data from ocean sensors around the world. They point out that the data includes ocean temperatures, ocean mass, and water volume in basin systems such as the Amazon River Basin.
Researchers found that El Niño events occurred consecutively from 2014 to 2016. The researchers found that both of these phenomena led to decreased rainfall in the Amazon basin and increased rainfall in large parts of the Pacific Ocean and Argentina. Most of the extra rain that fell on Argentina ran off into the ocean. They concluded that the rapid rise in sea levels from 2014 to 2016 was likely due to changes in rainfall patterns caused by the El Niño phenomenon.
For more information:
William Llovel et al., Causes of global mean sea level rise from 2014 to 2016, Geophysical Research Letters (2023). DOI: 10.1029/2023GL104709
Magazine information:
Geophysical Research Letters
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