The new Tulane University study questions the way in which the sea level rise in low-lying coastal areas, such as the south of Louisiana, is being measured, and suggests that the current method does not assess the seriousness of the problem. This study is in the newsletter published this week's magazine Science.
The relative increase in sea level, which is a combination of rising water levels and ground land, is traditionally measured with tide gauges. But researchers at Molly Keogh and Torbjörn Törnqvist say that on the coast of Louisiana, tide gauges indicate only a part of the story.
Tidal gauges in such areas are fixed at an average of 20 meters on the ground and not on the ground. "As a result, the tide gauges are not recorded in the shallow ground, and thus do not appreciate the relative sea level rise," said Keogh, the fifth year of the Ph.D. student and research manager.
"This study shows that we need to rethink completely how we measure rising sea levels in fast-paced coastal lowlands," said Törnqvists, Professor of Geology at Vokes Geological School of Science and Engineering.
Study published in an open journal Ocean Sciencesays that although tide gauges can accurately measure the downwardness that occurs under their foundation, they remain past the shallow submerged components. If at least 60 percent of the low precipitation occurs in the upper 5 meters of sediment columns, the tide meters do not include the primary relative sea level rise.
An alternative approach is to measure shallow landslides using surface height tables, cheap mechanical tools that record changes in surface elevation in wetlands. There are already over 300 of these tools in the coastal Louisiana network. The data can then be combined with measurements related to GPS data and sea level rise satellite measurements, Keogh said.
The relative sea level rise rates obtained from this approach are significantly higher than those resulting from tide measurement data. "That's why we conclude that low-rise offshore areas may be at greater risk of flooding, and in a shorter period than previously," said Keogh.
She said that the study affects coastal communities around the world.
"Across the world, communities in low coastal areas may be more vulnerable to flooding than we understood. It affects coastal management, city planners and emergency planners. a problem. "
The new map highlights the Louisiana coastline
Molly E. Keogh et al. Measurement Indicators for Modern Relative Sea Level Increases in Low-rise Coastal Zones: Critical Assessment Ocean Science (2019). DOI: 10.5194 / os-15-61-2019