Sea level rise could exceed estimates for US coastlines, NASA study finds

New results show average sea level rise approaching the 1-foot mark for most coasts of the contiguous United States by 2050. The Gulf Coast and the Southeast will see the most change.

By 2050, sea levels along contiguous U.S. coastlines could rise up to 12 inches (30 centimeters) above the current waterline, according to researchers who analyzed nearly three decades of observations. by satellite. Findings from NASA’s Sea Level Change Team could help refine short-term projections for coastal communities bracing for an increase in catastrophic and damaging flooding in years to come.

Global sea levels have been rising for decades in response to global warming, and multiple data sources indicate that the rise is accelerating. The new results support the higher scenarios described in an interagency report published in February 2022.

This report, compiled by several federal agencies, including NASA, the National Oceanic and Atmospheric Administration (NOAA) and the US Geological Survey, projects significant sea level rise over the next 30 years by region. They predicted 10 to 14 inches (25 to 35 centimeters) of rise on average for the East Coast, 14 to 18 inches (35 to 45 centimeters) for the Gulf Coast, and 4 to 8 inches (10 to 20 centimeters) for the ‘West. Coast.

Building on the methods used in this previous report, a team led by scientists from NASA’s Jet Propulsion Laboratory in Southern California took 28 years of satellite altimetry measurements of sea surface height and updated them. Correlated with records from NOAA tide gauges dating as far back as 1920. Continuously measuring the height of the surrounding water level, tide gauges provide a consistent record to compare with satellite observations.

The researchers noted that the rate of acceleration of sea level rise detected in satellite measurements from 1993 to 2020 – and the direction of these trends – suggest that future sea level rise will be in the upper range of estimates for all regions. Trends along the Southeast and Gulf Coasts of the United States are significantly higher than for the Northeast and West Coasts, although the range of uncertainty for the Southeast and Gulf Coasts is also larger . This uncertainty is caused by factors such as the effects of storms and other climatic variations, as well as the natural subsidence or displacement of the Earth’s surface along different parts of the coast.

“A key takeaway is that sea level rise along the U.S. coast has continued to accelerate over the past three decades,” said Ben Hamlington of JPL, leader of the change team. NASA sea level gauge and co-author of the new study published in Earth & Environment Communications and the previous report.

Hamlington noted that the team wanted to determine if they could refine sea level estimates for communities facing impending change. “We’ve heard from practitioners and planners along the coasts saying they need more information on shorter timescales – not looking 70 or 80 years into the future, but 20 or 30 years into the future. future,” he said. “The bottom line is that when we consider what we might experience in the years to come, we need to consider these higher possibilities.”

Change in flooding at high tide

The hazards of sea level rise are amplified by the Earth’s natural variability.

For example, by the mid-2030s, all US coasts will experience more intense high-tide flooding due to a swing in the Moon’s orbit that occurs every 18.6 years. Hamlington said this lunar cycle, combined with rising sea levels, is expected to worsen the impacts of high tide flooding during the 2030s and 2040s.

Year-to-year variabilities such as the effects of El Niño and La Niña can also complicate predicting how high and how fast sea levels will rise each year. Hamlington said the predictions will continue to be refined as satellites provide more data over time.

NASA and the French space agency Center National d’Etudes Spatiales (CNES) began jointly piloting satellite altimeters in the early 1990s, beginning a continuous spatial record of sea surface height with high accuracy and near-global coverage. This legacy continues with the launch in 2020 of the joint US-European Sentinel-6 Michael Freilich mission and its altimeter, which will provide scientists with an uninterrupted satellite record of sea level exceeding three decades. The mission is a partnership between NASA, NOAA, ESA (European Space Agency), European Organization for the Exploration of Meteorological Satellites and CNES.

NASA sea level researchers have long worked to understand how Earth’s changing climate is affecting the ocean. Along with launching satellites that provide data for the world’s longest record of sea surface height, NASA-supported scientists seek to understand the causes of sea level change on a global and regional scale. Through testing and modeling, they work to predict the extent of coastal flooding that U.S. communities will experience by the mid-2030s and provide an online visualization tool that allows the public to see how specific areas will be affected by sea level rise. Agencies at the federal, state and local levels use NASA data to inform their plans for adapting to and mitigating the effects of sea level rise. sea.