In January 2023, Northern California witnessed an unusual high-tide event, known as a King Tide, leading to the flooding of a highway on-ramp. This occurrence, exacerbated by sea level rise and El Niño, serves as a stark reminder of the potential challenges ahead.
Typically, high-tide flooding that engulfs roads and structures along the western coast of the Americas is infrequent outside of El Niño years. However, a recent analysis conducted by NASA’s sea level change science team suggests that this could change by the 2030s.
El Niño, a periodic climate phenomenon characterized by elevated sea levels and warmer ocean temperatures in the equatorial Pacific, has far-reaching consequences along the western coasts of the Americas. This year’s El Niño, still in its developmental stages, could bring heightened rainfall to the U.S. Southwest while subjecting countries in the western Pacific, such as Indonesia, to drought conditions. Typically, these impacts occur from January to March.
The NASA analysis reveals that a robust El Niño this winter could lead to as many as five occurrences of a specific type of flooding referred to as a “10-year flood event” in cities like Seattle and San Diego. Meanwhile, places like La Libertad and Baltra in Ecuador could experience up to three such events. This type of flooding is rare outside of El Niño years. Astonishingly, the researchers project that by the 2030s, rising sea levels and the influence of climate change might cause these cities to witness similar numbers of 10-year floods annually, with no El Niño event required.
A 10-year flood signifies an event with a one in 10 chance of happening in any given year. The extent of flooding experienced by a specific city or community depends on various factors, including local topography and the proximity of infrastructure to the ocean. Ten-year floods, according to the National Oceanic and Atmospheric Administration, can result in moderate flooding, leading to road and building inundation and the potential need for evacuations or relocating belongings to higher ground.
NASA’s coastal flooding analysis suggests that by the 2030s, during strong El Niño years, west coast cities in the Americas could encounter up to 10 of these 10-year flood events. By the 2050s, strong El Niños may trigger as many as 40 such events in a single year.
The expansion of water as it warms leads to higher sea levels, making regions with warmer water more susceptible. Researchers and forecasters closely monitor ocean temperatures and water levels to detect the formation and development of El Niño events.
“Climate change is already altering the baseline sea level along coastlines worldwide,” explains Ben Hamlington, a sea level researcher at NASA’s Jet Propulsion Laboratory. This shift results from planetary warming, as both the Earth’s atmosphere and oceans heat up, and ice sheets and shelves undergo melting. Consequently, the number of high-tide or nuisance flooding days experienced by coastal cities has already increased. Events like El Niños and storm surges, which temporarily elevate sea levels, compound these challenges.
Satellite missions, such as the Surface Water and Ocean Topography (SWOT) satellite and Sentinel-6 Michael Freilich, play a vital role in monitoring sea levels and El Niños in the short term. SWOT, in particular, collects data on sea levels close to the coast, improving our ability to project sea level rise. This information can assist policymakers and planners in preparing communities for the rising seas anticipated in the coming decades.
“As climate change accelerates, some cities will experience flooding five to 10 times more frequently. SWOT will closely monitor these changes to ensure that coastal communities are well-prepared,” emphasizes Nadya Vinogradova Shiffer, SWOT program scientist and director of the ocean physics program at NASA Headquarters in Washington.
Table of Contents
Frequently Asked Questions (FAQs) about El Niño-Driven Flood Risks
What is El Niño, and how does it affect coastal areas?
El Niño is a periodic climate phenomenon characterized by elevated sea levels and warmer ocean temperatures in the equatorial Pacific. These conditions can extend poleward along the western coasts of the Americas. El Niño events can bring higher-than-normal rainfall to regions like the U.S. Southwest and drought to areas in the western Pacific, such as Indonesia. These impacts typically occur from January to March.
What did NASA’s sea level change science team discover in their analysis?
NASA’s analysis suggests that if a strong El Niño develops this winter, cities along the western coasts of the Americas could experience an increase in the frequency of high-tide flooding. This type of flooding can inundate roads and low-lying buildings. The analysis predicts that during a strong El Niño, cities like Seattle and San Diego could witness up to five instances of a 10-year flood event this winter. Ecuadorian cities like La Libertad and Baltra might experience up to three of these events.
What is a “10-year flood event,” and why is it significant?
A 10-year flood event has a one in 10 chance of occurring in any given year. It serves as a measure of how high local sea levels can rise. The extent of flooding depends on factors like topography and infrastructure proximity to the ocean. These events can result in moderate flooding, including road and building inundation, and may require evacuations or the relocation of belongings to higher ground.
How might the frequency of 10-year flood events change in the future?
The analysis indicates that by the 2030s, cities along the west coast of the Americas could experience up to 10 of these 10-year flood events during strong El Niño years. By the 2050s, this number could increase to as many as 40 such events in a single year due to the influence of climate change and rising sea levels.
What role does climate change play in these flooding risks?
Climate change is already altering baseline sea levels along coastlines globally. As the Earth’s atmosphere and oceans warm, and ice sheets and shelves melt, sea levels rise. This has led to an increase in high-tide or nuisance flooding days in coastal cities. Climate change, along with events like El Niños and storm surges, which temporarily elevate sea levels, exacerbates the risk of coastal flooding.
How are satellite missions like SWOT helping monitor and prepare for these challenges?
Satellite missions, including the Surface Water and Ocean Topography (SWOT) satellite and Sentinel-6 Michael Freilich, monitor sea levels and El Niños in the near term. SWOT, in particular, collects data on sea levels close to the coast, improving sea level rise projections. This information can assist policymakers and planners in preparing coastal communities for the rising seas anticipated in the coming decades.
More about El Niño-Driven Flood Risks
- NASA’s Sea Level Change Science
- El Niño and Climate
- National Oceanic and Atmospheric Administration (NOAA)
- Surface Water and Ocean Topography (SWOT) Satellite
- Sentinel-6 Michael Freilich
- NASA’s Jet Propulsion Laboratory
