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Earth & Climate

“New Orleans’ Sinking City: $15 Billion Flood Defenses Under Threat from Land Subsidence”

Parts of New Orleans are sinking at alarming rates — including some of the very floodwalls built to protect it. A new satellite-based study finds that some areas are losing nearly two inches of elevation per year, threatening the effectiveness of the city’s storm defenses.

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New Orleans is facing an unprecedented threat from its own foundation. A recent study by Tulane University researchers has revealed that parts of the city are gradually sinking, while the $15 billion post-Katrina flood protection system may need regular upgrades to outpace long-term land subsidence.

The study, published in Science Advances, used satellite radar data to track subtle shifts in ground elevation across Greater New Orleans between 2002 and 2020. The findings show that some neighborhoods, wetlands, and even sections of floodwalls are sinking by more than an inch per year – with some areas experiencing up to 47 millimeters (nearly 2 inches) of elevation loss annually.

“In a city like New Orleans, where much of the land is already near sea level, even minor drops in elevation can increase flood risk,” said Simone Fiaschi, lead author of the study and a former researcher with Tulane’s Department of River-Coastal Science and Engineering. “The findings underscore how both natural and human-driven forces are reshaping the city’s landscape.”

Causes of the sinking – known as subsidence – include natural soil compaction, groundwater pumping, industrial development, and the legacy of wetland drainage for urban growth. The study used a remote sensing technique called InSAR (Interferometric Synthetic Aperture Radar), which detects millimeter-scale changes in land surface elevation by comparing satellite radar images taken over time.

Among the most troubling findings: some of the concrete floodwalls and levees built to protect the city after Katrina are themselves sinking. In a few cases, parts of the Hurricane and Storm Damage Risk Reduction System (HSDRRS) are losing elevation faster than sea levels are rising, reducing their capacity to block storm surges.

“These results are a wake-up call,” said co-author Prof. Mead Allison, also of Tulane. “We need ongoing monitoring and maintenance to ensure that our flood defenses don’t lose their level of protection beneath us.”

The study also found pockets of sinking around industrial sites, the airport, and newer residential developments – areas where soil compression and groundwater withdrawal are likely contributors. In contrast, some areas such as parts of Michoud showed modest land uplift, likely due to the halt of industrial groundwater pumping and recovery of the water table.

Wetlands east of the city, long known for their ecological importance, are also sinking rapidly in places. In some spots, the loss of elevation could transform marshes into open water within a decade if trends continue. This has implications not just for wildlife but also for storm protection, as wetlands help buffer storm surges.

New Orleans, much of which lies below sea level, relies on an elaborate system of levees, pumps, and drainage canals to keep water out. As sea levels rise and the ground sinks, the margin for error narrows.

Experts say that without sustained monitoring, including satellite data and ground-based measurements, it’s difficult to know where to reinforce levees or how to plan for future storms.

“This research shows that land movement isn’t uniform, and understanding these patterns is crucial for protecting lives and property in a city where inches truly matter,” Fiaschi said. “However, it’s crucial to remember that our results still require careful ground-truthing. This is especially true for critical areas like the floodwalls, where on-site verification was not possible during this project.”

The study highlights the potential of satellite monitoring to guide infrastructure maintenance and urban planning, not just in New Orleans but in coastal cities worldwide facing similar challenges.

Air Quality

Greenland’s Glacial Runoff Fuels Explosive Growth in Ocean Life

NASA-backed simulations reveal that meltwater from Greenland’s Jakobshavn Glacier lifts deep-ocean nutrients to the surface, sparking large summer blooms of phytoplankton that feed the Arctic food web.

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Greenland’s glacial runoff is fueling an explosion in ocean life, according to a recent study supported by NASA. As the ice sheet melts, it releases massive amounts of freshwater into the sea, which then interacts with the surrounding saltwater and nutrients from the depths.

The researchers used a state-of-the-art computer model called Estimating the Circulation and Climate of the Ocean-Darwin (ECCO-Darwin) to simulate the complex interactions between biology, chemistry, and physics in one pocket along Greenland’s coastline. The study revealed that glacial runoff delivers nutrients like iron and nitrate, essential for phytoplankton growth, to the surface waters.

Phytoplankton are tiny plant-like organisms that form the base of the ocean food web. They take up carbon dioxide and produce oxygen as byproducts of photosynthesis. In Arctic waters, their growth rate has surged 57% between 1998 and 2018 alone. The study found that glacial runoff boosts summertime phytoplankton growth by 15 to 40% in the study area.

Increased phytoplankton blooms can have a positive impact on Greenland’s marine animals and fisheries. However, untangling the impacts of climate change on the ecosystem will take time and further research. The team plans to extend their simulations to the whole Greenland coast and beyond.

The study also highlights the interconnectedness of the ocean ecosystem, with phytoplankton blooms influencing the carbon cycle both positively and negatively. While glacial runoff makes seawater less able to dissolve carbon dioxide, the bigger blooms of phytoplankton take up more carbon dioxide from the air as they photosynthesize, offsetting this loss.

The researchers emphasize that their approach is applicable to any region, making it a powerful tool for studying ocean ecosystems worldwide. As climate change continues to reshape our planet, understanding these complex interactions will be essential for predicting and mitigating its impacts on marine life and ecosystems.

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Atmosphere

NASA’s SWOT Satellite Captures Kamchatka Megaquake Tsunami in Stunning Detail

When a massive 8.8 magnitude earthquake struck off Russia’s Kamchatka Peninsula, NASA and CNES’s SWOT satellite captured a rare and detailed picture of the tsunami that followed. Recorded just over an hour after the quake, the satellite revealed the wave’s height, shape, and path, offering scientists an unprecedented multidimensional view from space.

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The recent megaquake that struck off the coast of Russia’s Kamchatka Peninsula has been captured in striking detail by NASA’s SWOT satellite. Launched jointly with the French space agency CNES, the SWOT satellite is equipped with a unique radar system that can measure ocean topography and water levels across vast areas.

On July 30, at around 11:25 a.m. local time, an 8.8 magnitude earthquake struck off the coast of Kamchatka, generating a massive tsunami wave. The SWOT satellite captured the leading edge of this tsunami just 70 minutes after the quake hit. This remarkable footage has provided scientists with crucial data to improve tsunami forecast models.

The data collected by the SWOT satellite included measurements of the wave height exceeding 1.5 feet (45 centimeters), as well as a detailed look at the shape and direction of travel of the leading edge of the tsunami. These observations have been plotted against a forecast model produced by the U.S. National Oceanic and Atmospheric Administration (NOAA) Center for Tsunami Research.

Comparing these observations to the model helps forecasters validate their predictions, ensuring that they can provide accurate early warnings to coastal communities in the event of a tsunami. As Nadya Vinogradova Shiffer, NASA Earth lead and SWOT program scientist at NASA Headquarters, explained, “The power of SWOT’s broad, paintbrush-like strokes over the ocean is in providing crucial real-world validation, unlocking new physics, and marking a leap towards more accurate early warnings and safer futures.”

Ben Hamlington, an oceanographer at NASA’s Jet Propulsion Laboratory, highlighted the significance of the 1.5-foot-tall wave captured by SWOT, saying that what might seem like a small wave in open waters can become a massive 30-foot wave in shallower coastal areas.

The data collected by the SWOT satellite has already helped scientists improve their tsunami forecast models at NOAA’s Center for Tsunami Research. This is a crucial step towards enhancing operational tsunami forecasts and saving lives. As Josh Willis, a JPL oceanographer, noted, “The satellite observations help researchers to better reverse engineer the cause of a tsunami, and in this case, they also showed us that NOAA’s tsunami forecast was right on the money.”

This breakthrough has significant implications for coastal communities around the world. By providing more accurate early warnings, SWOT data can save lives and reduce damage caused by tsunamis. As Vasily Titov, the center’s chief scientist in Seattle, emphasized, “It suggests SWOT data could significantly enhance operational tsunami forecasts — a capability sought since the 2004 Sumatra event.” The devastating tsunami generated by that quake killed thousands of people and caused widespread destruction in Indonesia.

The SWOT satellite was jointly developed by NASA and CNES, with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. NASA JPL leads the U.S. component of the project, providing a Ka-band radar interferometer instrument, a GPS science receiver, a laser retroreflector, a two-beam microwave radiometer, and NASA instrument operations.

This groundbreaking technology has opened up new possibilities for scientists to better understand ocean dynamics and improve tsunami forecasting models. As SWOT continues to capture stunning images of our oceans, it will undoubtedly play a vital role in enhancing operational tsunami forecasts and saving lives around the world.

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Climate

The Ocean’s Fragile Fortresses: Uncovering the Impact of Climate Change on Bryozoans

Mediterranean bryozoans, including the “false coral,” are showing alarming changes in structure and microbiomes under acidification and warming. Field studies at volcanic CO₂ vents reveal that these stressors combined sharply reduce survival, posing risks to marine ecosystems.

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The Ocean’s Fragile Fortresses: Uncovering the Impact of Climate Change on Bryozoans

Bryozoans, small colonial invertebrates, play a vital role in forming marine habitats. However, their response to environmental changes has long been overlooked. A recent study published in Communications Biology sheds light on how ocean acidification and warming can affect bryozoan colonies, with crucial implications for marine conservation.

The researchers from the Institut de Ciències del Mar (ICM-CSIC) used a natural laboratory on the island of Ischia, Italy, to simulate the conditions projected for the end of the century. They analyzed the morphology, skeleton mineralogy, and microbiome of two bryozoan species exposed to these conditions. The findings revealed that the species exhibit some acclimation capacity, modifying their skeletal mineralogy to become more resistant.

However, a loss in functional microbial diversity was observed, with a decline in genera potentially involved in key processes such as nutrition, defense, or resistance to environmental stress. This suggests that even if colonies look externally healthy, changes in the microbiome could serve as early bioindicators of environmental stress.

The study also considered the effects of rising temperatures, another key factor in climate change. The models used indicate that the combination of these two stressors intensifies the effects observed, significantly reducing the coverage of the encrusting bryozoan and increasing mortality.

These findings have important implications for marine conservation. Habitat-forming species like bryozoans are not only vulnerable but their disappearance could trigger cascading effects on many other species that rely on them for shelter or food. The characterization of the microbiome and preliminary identification of potentially beneficial microorganisms open new research avenues to enhance the resilience of holobionts (host and its associated microbiome) through nature-based approaches.

The complexity of this issue demands integrated analyses, highlighting the importance of interdisciplinary approaches in anticipating future scenarios and protecting marine ecosystems.

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