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

Over the next few decades, rising sea levels will lead to increased storm surges and tides for millions of Americans in coastal communities. Norfolk, Virginia is pictured here with a flooded roadway. Credit: City of Norfolk

The new results show mean sea level rise approaching the 1-foot mark for most of the contiguous US coasts by 2050. The Gulf Coast and Southeast will see the greatest change.

By 2050, sea levels along the contiguous U.S. coasts could rise as much as 12 inches (30 centimeters) above today’s waterline, according to researchers who analyzed nearly three decades of satellite observations. Findings from NASA’s Sea Level Change Team could help refine near-term projections for coastal communities preparing for an increase in both catastrophic and nuisance flooding in the coming years.

Global sea levels have been rising for decades in response to global warming, and multiple lines of evidence indicate that the rise is accelerating. The new findings support higher-end scenarios outlined in an interagency report released in February 2022.

That report, developed by several federal agencies, including NASA, the National Oceanic and Atmospheric Administration (NOAA), and the US Geological Survey, predicts significant sea level rise over the next 30 years by region. They projected an average increase of 10 to 14 inches (25 to 35 centimeters) 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 Coast.

Building on the methods used in that earlier report, a team led by scientists at NASA’s Jet Propulsion Laboratory in Southern California took 28 years of satellite altimeter measurements of sea surface height and correlated them with tide gauge records. NOAA dating back to the distant 1920s. By continuously measuring the height of the surrounding water level, tide gauges provide a consistent record for comparison with satellite observations.

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

An illustration of the Sentinel-6 satellite Michael Freilich. Launched November 2020. Credit: NASA/JPL-Caltech

The researchers noted that the accelerating rate of sea level rise seen in satellite measurements from 1993 to 2020 – and the direction of those trends – suggest that future sea level rise will be in the higher range of estimates for all the regions. The trends along the US Southeast and Gulf coasts are substantially 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 land surface along different parts of the coast.

“A key point is that sea level rise along the US coast has continued to accelerate over the past three decades,” said JPL’s Ben Hamlington, leader of the NASA Sea Level Change Team and co-author of both new studies. published on Earth & Environment Communications and the previous report.

Hamlington noted that the team wanted to determine whether it was possible to refine sea level estimates for communities facing impending change. “We’ve heard from professionals and planners along the coasts that they need more information about shorter timescales, looking not 70 or 80 years into the future, but looking 20 or 30 years into the future,” she said. “The bottom line is that as we look ahead to what we might experience in the next few years, we need to consider these increased possibilities.”

visualization tool from NASA’s Sea Level Change Team makes data on future sea level rise from the Intergovernmental Panel on Climate Change easily accessible to the public. Credit: NASA/JPL-Caltech”>

L'innalzamento del livello del mare potrebbe superare le stime per le coste degli Stati Uniti, rileva uno studio della NASAdisplay tool by NASA’s Sea Level Change Team makes data on future sea level rise from the Intergovernmental Panel on Climate Change easily accessible to the public. Credit: NASA/JPL-Caltech”/>

A visualization tool from NASA’s Sea Level Change Team makes data on future sea level rise from the Intergovernmental Panel on Climate Change easily accessible to the public. Credit: NASA/JPL-Caltech

Displacement in case of flooding from high tide

The dangers of rising sea levels are magnified by natural variability on Earth.

For example, by the mid-2030s, every US coast will experience more intense high-water flooding due to a wobble in the Moon’s orbit that occurs every 18.6 years. Hamlington said this lunar cycle, in combination with sea level rise, is expected to worsen the impacts of high-water flooding during the 2030s and 2040s.

Year-to-year variability, such as the effects of El Niño and La Niña, can also make it difficult to predict 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’Études Spatiales (CNES) began jointly flying satellite altimeters in the early 1990s, initiating a continuous spatial recording of sea surface height with high accuracy and near coverage. global. This legacy continues with the 2020 launch 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 spanning more than three decades. The mission is a partnership between NASA, NOAA, ESA (European Space Agency), the European Organization for the Exploration of Meteorological Satellites and CNES.

NASA sea level researchers have long worked to understand how Earth’s changing climate affects the ocean. Along with launching satellites that provide data on the long-running global sea-surface height record, NASA-supported scientists seek to understand the causes of global and regional sea level change. Through testing and modeling they work to predict how much coastal flooding US 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. Federal, state and local level agencies use NASA data to inform their plans for adapting to and mitigating the effects of sea level rise.

More information:
Benjamin D. Hamlington et al, Observation-based trajectory of future sea level for US coastal traces near high-end model projections, Earth & Environment Communications (2022). DOI: 10.1038/s43247-022-00537-z

Citation: Sea level rise could exceed estimates for US coasts, NASA study finds (2022, Nov. 16) retrieved Nov. 16, 2022 from https://phys.org/news/2022-11- sea-exceed-coasts-nasa.html

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