Most of the world’s population lives in low-lying lands close to the sea, with some expected to be submerged at the end of the 21st century due to rising sea levels.
The most appropriate assessment of the impact of sea level changes on these communities is the relative sea level rise, the change in altitude between land level and sea level. For an observer standing on the shore edge, the relative rise in sea level is the net change in sea level, which also includes the rise and fall of the land rising below the observer’s feet.
A team of scientists at Arizona State University observed for the first time using accurate modern satellite interferometric synthetic aperture radar (InSAR) measurements that can detect the rise and fall of the earth’s surface with millimeter accuracy. the entire vertical land movement of the California coast.
They identified local declining coastal spots in the cities of San Diego, Los Angeles, Santa Cruz, and San Francisco. The total population of 4 to 8 million people suffers from rapid landfall, which will experience greater flooding. decades before the projected rise in sea levels.
“We have ushered in a new era of coastal maps with more than 1,000 times the detail and resolution of any time before,” said Manoochehr Shirzaei, chief investigator of a NASA-funded project. “The unprecedented detail and sub-millimeter accuracy addressed in our vertical earth movement dataset may change our understanding of natural and anthropogenic changes in relative sea levels and associated hazards.”
The results were announced in this week’s issue Scientific achievements.
The research team consisted of Emu Blackwell, a graduate and lead author of the ASU School of Earth and Space Exploration, and faculty members Manoochehr Shirzaei, Chandrakanta Ojha, and Susanna Werth (Werth has a double appointment at the School of Geography and Urbanism).
Em Blackwell was very interested in geology, and when Blackwell started graduating from school, InSAR applications encouraged them to continue this project. InSAR uses radar to measure changes in the distance between the satellite and the Earth’s surface and generates highly accurate maps of Earth’s deformation at 10 s resolution in 100 s km.
Earthquake can occur due to natural and anthropogenic processes or a combination of both. Natural processes include tectonics, glacial isostatic adjustment, sediment loading, and soil compaction. Anthropogenic causes include groundwater extraction and oil and gas extraction.
Since 2005 Some 40 million people have been at risk of one of the 100 years of coastal flooding, and by 2070. That number will more than triple. The value of flood-affected assets will rise to around 9% of projected global gross domestic product, with the US, Japan and the Netherlands facing the greatest risks. These impact assessments are often based only on forecasts of average global sea level rise and do not take into account vertical land movements.
The study measured the entire 1,350 km of California coastline from 2007 to 2018, consisting of 1,000 satellite images used for a vertical land motion map with a 35 million-pixel image with a resolution of 8080 m over a wide range. coastal elevation and level of descent. Coastal community politicians and the general public are free to download the data (link to additional data).
The four metropolitan areas with the greatest impact in these areas were San Francisco, Monterey Bay, Los Angeles, and San Diego.
“The vast majority of the perimeter of San Francisco Bay is shrinking to 5.9 mm a year,” Blackwell said. “It should be noted that San Francisco International Airport is accelerating faster than 2.0 mm per year. Monterey Bay Bay, including the city of Santa Cruz, is sinking quickly without any takeoff zones. The drop rate in this zone is 8.7 mm / Los Angeles area is showing a decline in small coastal areas, but most of the decline is on land “.
North of the San Francisco Bay Area (3-5 mm per year) and Central California (same rate) uplift area.
Due to future migration, the coastal population is expected to increase by 2050. It will grow to more than 1 billion people. The risk of future floods that these communities will face is largely controlled by the relative rise in sea level, ie sea level rise and vertical land movement. It is very important to include land degradations in the regional projections, which are used to determine the floodplains of the urbanized coast.
In addition to this study, the ASU research team hopes that other members of the scientific community will be able to draw on their findings to measure and identify coastal hazards more broadly in the U.S. and around the world.
The study says the seas could rise faster than expected
“Surveillance of California’s sunken coast from space: implications for relative sea level rise” Scientific achievements (2020). DOI: 10.1126 / sciadv.aba4551
Provided by Arizona State University
Citation: Satellite Survey Shows Sunken Coasts of California (July 31, 2020), Received in 2020 July 31 From https://phys.org/news/2020-07-satellite-survey-california-coastal-hotspots.html
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