A new for the Territory of American Samoa was released to the public, enabling the community to visualize how the shoreline is likely to change from coastal flooding, sea-level rise, hurricane storm surge and high tides.

The visualization tool will be an essential component in future planning to assess the short and long-term impacts of rising seas and to minimize the risks to coastal communities, infrastructure and the environment.

A partnership of organizations at the University of Hawaiʻi developed the American Samoa Sea Level Rise Viewer over the course of two years, with the (PacIOOS) preparing the platform for the (糖心Vlog官方SLC) using funding from the (PI-CASC) and local extension facilitation from (Hawaiʻi Sea Grant).

While there are other sea-level rise viewers throughout the continental U.S. and Hawaiʻi, this mapping tool is of particular importance to American Samoa. Local sea levels have been rising from climate change effects at rates 2.8 times faster than the global average. Beyond that, ever since a devastating 2009 earthquake and tsunami, American Samoa has been actively sinking. This sinking, called subsidence, contributes even more relative change in water levels, with estimates suggesting roughly twice as much total sea-level rise, for these islands, by 2060 than what is predicted from climate effects alone.

Kelley Anderson Tagarino, Hawaiʻi Sea Grant extension agent based at the , along with local colleagues began to notice a distinct increase of sea levels in tide gauge data, beginning at the time of the 2009 earthquake. She ultimately created a partnership to develop an interactive tool demonstrating sea-level rise projections, engaging Phil Thompson, director of 糖心Vlog官方SLC, and his PI-CASC graduate scholar Carla Baizeau and the PacIOOS team.

Tagarino said, “I sought funding for a sea-level rise viewer to empower our community to plan for our future. Now, everyone can use the viewer to zoom in to specific areas and even individual homes, which is critical to developing resilience plans at the village level.”

The sea-level rise viewer is already being used to inform the design of the new Pago Pago airport terminal buildings.

Threatening natural, cultural resources

Beyond critical infrastructure, the high rates of sea-level rise also threaten natural and cultural resources, agriculture, water resources, critical habitat and much more.

Alphina Liusamoa, a turtle biologist with the , is thrilled to find areas with important ecological zones included, like sea turtle nesting beaches on outer islands. “This is incredibly valuable as it allows us to comprehensively assess the risk of rising sea levels to these important nesting habitats. The tool鈥檚 interactive nature provides a valuable opportunity for education and outreach, and it can assist us in implementing conservation measures to protect these fragile ecosystems.”

Baizeau traveled from Hawaiʻi to join Tagarino and present the sea-level rise viewer to community leaders and other officials throughout the territory, and at Amerika Samoa鈥檚 2nd Annual Disaster Resilience Summit in September.

“I was lucky enough to go to American Samoa and meet with the village chiefs and students,” said Baizeau. “Everyone was very interested in learning how to use the viewer so they can start planning for their future. It has been really gratifying to be part of this project, and I hope to continue to improve on the work we鈥檝e started.”

Future plans for the tool include adding the effects of wind and wave activity.

For more information, contact: Kelley Anderson Tagarino (kelleyat@hawaii.edu); Cindy Knapman (lknapman@hawaii.edu); Rachel Lentz (rlentz@hawaii.edu) or info@PacIOOS.org.

A program supporting communities in the Pacific region to become more resilient to the effects of climate change received a five-year, $6.36 million research grant from the (NOAA).

The University of Hawaiʻi at M膩noa will work with the East-West Center, Arizona State University (ASU) and other stakeholders to kickoff the next phase of NOAA鈥檚 Pacific Regional Integrated Sciences and Assessments (Pacific RISA) program. Known as “Pacific RISA IV: Building Equitable and Just Climate Solutions for Pacific Island Resilience to Compound Disasters and Extreme Events,” this phase will address pressing regional and community-specific climate challenges in Hawaiʻi and the U.S.-Affiliated Pacific Islands (USAPI), encompassing the Territories of Guam and American S膩moa, the Commonwealth of the Northern Mariana Islands, and the Freely Associated States of the Republic of Palau, the Republic of the Marshall Islands and the Federated States of Micronesia.

Thomas Giambelluca, 糖心Vlog官方 Water Resources Research Center director and professor, said, “With all the recent news of catastrophic extreme weather globally, nationally and here in Hawaiʻi, the Pacific RISA project鈥檚 focus on climate-change-driven extreme weather events in Hawaiʻi and the USAPI is both timely and critically important to decision makers and communities in the region. The University of Hawaiʻi has a major responsibility, as the research center for the Pacific, to bring scientific expertise to bear on critical issues surrounding climate change adaptation.”

Researchers with the project have collaborated with natural resource managers, policymakers, local and national governments, and non-profit organizations to gather data, as well as advocate for regional climate needs at the national and international levels. They will now address the core question of Pacific RISA Phase IV: How can we support and develop sustainable, equitable, and just climate solutions that increase Pacific Island resilience to compound disasters and extreme events?

The USAPI is made up of more than 300,000 square miles of land and millions of square miles
of ocean, making the area culturally, geographically and economically diverse. There are a variety of factors that affect how individuals, communities and organizations prepare for and recover from what Pacific RISA researchers call compound events, which are seemingly isolated events that act in combination with one another to produce more serious negative consequences.

To work on building community resilience to these compound events, the Pacific RISA
Phase IV will host peer-to-peer exchanges among project participants in Hawaiʻi, the USAPI and the national RISA network that will help scale lessons learned and solutions discovered to the national level. This phase of the project will strive to maintain and expand Pacific RISA鈥檚 role as a source of use-inspired research and a trusted climate boundary organization.

More about Pacific RISA

Pacific RISA is led by a team based at ASU, in partnership with East-West Center and with researchers from 糖心Vlog官方鈥檚 Water Resources Research Center, , and .

This public impact research is an example of 糖心Vlog官方 M膩noa鈥檚 goals of (PDF) and (PDF), two of four goals identified in the (PDF), updated in December 2020.

This editorial by Assistant Professor Philip R. Thompson was posted in

Full moon, new moon. High tide, low tide. These are dependable rhythms of our planet. It is not surprising then, that news of a “wobble” in the moon鈥檚 orbit—one with implications for the growing problem of U.S. coastal flooding 鈥� has piqued the curiosity of many.

So, what exactly is this “wobble?” The word wobble suggests a breakdown in the regular and predictable motion of the moon and its influence on the tides. This is not the intended meaning, though. What the media has termed the ”wobble” is actually a cycle as regular as the seasons but occurring over decades rather than months. More specifically, the path of the moon鈥檚 orbit around Earth is tilted in space and rotates once every 18.6 years with a motion similar to the undulations of a spinning coin just before it falls flat. This motion is more precisely described as lunar nodal precession, and it is most certainly not a new discovery. Astronomers have observed this phenomenon for millennia by documenting gradual changes to the moon鈥檚 position in the night sky.

Precession of the moon鈥檚 orbit is not merely an astronomical phenomenon—it also affects ocean tides, which is how this esoteric “wobble” is connected to coastal flooding and made it into the headlines. The effect of precession on tides is not the same everywhere: To get an idea of the size of the effect, consider St. Petersburg, Florida, where the height of the highest tides changes over the lunar precession cycle by a little less than two inches. That may not seem like much, but keep in mind that the total amount of global average sea-level rise over the last decade is also a little less than two inches. That means that the “wobble” has roughly the same impact on the height of high tides as the most recent decade of global sea-level rise.

These seemingly small changes can have big consequences because high-tide flooding is a game of inches, where benign high water levels suddenly become impactful as the edge of a storm drain or sea wall is breached. Not to mention that the extent and frequency of such events increases rapidly with every incremental increase in the height of high tides. In St. Petersburg, for example, increasing the height of high tides by four inches (similar to the influence of the “wobble” plus a decade of sea-level rise) can produce an increase from 10 high-tide floods per year to 45 floods per year. That same four inches in Honolulu, Hawaii can produce an increase from 10 to almost 70 high-tide floods per year. Inches matter.

Of course, this is not the sort of extreme flooding that makes good fodder for a Hollywood climate-disaster film. Instead, high-tide flooding can occur on a sunny, otherwise normal day and result in impacts like minor erosion; backed up drainage and sewage systems; and/or standing water in roads, parking lots and basements.

We should be careful, though, not to confuse lack of total destruction for lack of importance. This is often a challenge in communicating the real-world, incremental impacts of ongoing climate change. High-tide flooding may not produce the next Atlantis, but it will cause an insidious accumulation of seemingly minor economic and infrastructural consequences. The impact will become acute as more and more events occur over increasingly narrow windows of time.

Planning for any aspect of climate change requires acknowledging and understanding the interplay between natural cycles and human-induced climate trends. Both exist, and the existence of one does not preclude the other. A decade-long global warming “pause,” for example, does not mean that a century-long warming trend is not happening.

Similarly, my research team has shown that precession of the moon鈥檚 orbit will at times act to slow (and perhaps even pause) increasing frequency of high-tide flooding due to sea-level rise. But we also know that the opposite will occur, and many U.S. coastal communities will experience periods of rapid increase in high-tide flooding when the cyclical “wobble” acts to enhance the effects of sea-level rise.

Our work specifically points to the mid-2030s as the onset of one such period of rapid change. Under the NOAA Intermediate scenario for sea-level rise, we project that a majority of coastal locations in the Gulf of Mexico, California and Hawaiʻi will experience at least a quadrupling and as much as a ten-fold increase in the frequency of high-tide floods over a 10-year period beginning in the 2030s. These communities will join the many places along the U.S. East Coast that already experience recurrent flooding at high tide, transforming a regional problem into a national issue.

To make matters worse, the onset of this rapid change will come on the heels of a period during which the cyclical “wobble” will suppress increases in high-tide flooding due to sea-level rise. It is essential that affected communities are not complacent during the period of slow change in order to avoid being caught off guard by the rapid change to follow. Fortunately, we can point to a specific natural cycle to predict and explain what is happening, but continued reminders will be necessary.

In Hawaiʻi, where I live, there is a proverb: I Kahiki ka ua, ako ʻ膿 ka hale, which means “while the rain is far away, thatch the house.” The mid-2030s are not all that far away, and the infrastructure projects needed to mitigate the impacts of increased high-tide flooding will take time and resources.

Now is the time to acknowledge the changes we are observing, to be realistic about what鈥檚 to come, and to get to work ensuring that our coastal communities are resilient and thrive in the coming decades.

—Philip R. Thompson, is an assistant professor in the Department of Oceanography at University of Hawaiʻi at M膩noa and director of the 糖心Vlog官方 Sea Level Center. He is the lead author of a recent study that generated headlines by showing how a natural cycle in the moon鈥檚 orbit affects future coastal flooding due to sea-level rise.

Multiple United States coastal regions may see rapid increases in the number of high-tide flooding days in the mid-2030s, according to a study led by the and published in . The combined effects of sea-level rise and natural fluctuations in tidal range are anticipated to cause tipping points in the frequency of high-tide flooding.

Coastal locations around the U.S., particularly along the Atlantic coast, are experiencing recurrent flooding at high tide. The impact of high-tide flooding accumulates over numerous, seemingly minor occurrences, which can exceed the impact of rare extremes over time. These impacts are subtle—for example, the loss of revenue due to recurrent road and business closures—compared with the physical damage of property and infrastructure associated with extreme storm-driven events.

“We expect the most rapid increases to be along the U.S. Pacific and Gulf of Mexico coastlines, which includes Hawaiʻi and other Pacific Islands. This is important, because this is the point at which high-tide flooding transitions from being primarily a local or regional issue and becomes a national issue affecting a majority of our nation鈥檚 coastlines,” said lead author Phil Thompson, director of the and assistant professor of oceanography in the 糖心Vlog官方 Mānoa (SOEST).

Research such as this provides sound, science-based information on which decision makers can base plans for adapting to sea-level rise and mitigating the impacts of local and regional flooding.

High-tide flooding episodes

Thompson and researchers from around the country analyzed tide gauge data from 89 coastal locations around the U.S., including 10 locations from Hawaiʻi and U.S.-Affiliated Pacific Islands, and developed a novel statistical technique that combined changes in tidal range with NOAA (National Oceanic and Atmospheric Administration) sea-level rise scenarios for the 21st century to produce the projections of high-tide flooding.

Continued sea-level rise will exacerbate the issue where present, and many more locations will begin to experience recurrent high-tide flooding in the coming decades. Additionally, the research team found that annual cycles in tides and sea level can combine with oceanographic anomalies to produce many high-tide flooding episodes over a short amount of time—creating extreme months with clustered events.

The results of the study directly address how coastal communities could plan for the future.
“Scientists, engineers and decision-makers are accustomed to thinking about rare high-impact events, for example, a 100-year storm, but we demonstrate that it is important to plan for extreme months or seasons during which the number of flooding episodes, rather than the magnitude, is exceptional,” said Thompson.

This research is an example of 糖心Vlog官方 Mānoa鈥檚 goal of (PDF), one of four goals identified in the (PDF), updated in December 2020.

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–By Marcie Grabowski

A new tool to help decision makers and others assess how sea-level rise and other factors will affect the frequency of high-tide flooding in U.S. coastal locations in the next 50–100 years has been developed by Director Phil Thompson with funding from NASA鈥檚 Earth Science Division.

High-tide flooding, also known as “sunny day” or nuisance flooding, is an increasingly frequent occurrence in coastal areas around the United States. The is an online dashboard that projects the number of high-tide flooding days per year for 97 U.S. cities, based on National Oceanic and Atmospheric Administration (NOAA) impact thresholds. These thresholds provide a safety gap between regular high-tide water levels and conditions that result in flooding. Coastal communities are built at a certain elevation above sea-level with these natural fluctuations in mind.

The tool is based on projections of sea-level rise and the height of the highest astronomical tides, which vary on a predictable 18.6-year cycle that鈥檚 determined by the Moon鈥檚 orbit around Earth. Over multiple decades, changes in the Moon鈥檚 orbit cause cyclical variations in the height of high and low tides in certain regions. These changes occur slowly.

“Tides aren鈥檛 as constant as people think they are,” said Thompson, who is also an assistant professor in the 糖心Vlog官方 Manoa School of Ocean and Earth Science and Technology (SOEST) . “They change on long time scales.”

When high tides get lower, the net effect of sea-level rise on flooding is reduced. The tool predicts this will happen in many U.S. locations from the mid-2020s until the mid-2030s, when high tides will once again get higher. When increases in high tides sync up with increases in global or regional sea-level rise and other factors that cause sea levels to vary, there鈥檚 a potential for rapid increases in coastal water levels and associated impacts. For regions where the rate of sea-level rise is already accelerating, such as along the , the cycle will exacerbate those impacts.

“We鈥檒l observe a rapid increase in high-tide flooding days for regions around the globe,” Thompson said. “For a place like California, the height of high tides will increase 3 to 5 centimeters over 10 years, on top of a similar increase from sea-level rise that鈥檚 driven by climate change.”

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A global tendency for future sea levels to become more variable this century as oceans warm, due to increasing greenhouse gas emissions was identified by a team of researchers at the University of Hawaiʻi at Mānoa (SOEST). Sea-level variability alters tidal cycles and enhances the risks of coastal flooding and erosion beyond changes associated with sea-level rise.

Sea-level rise is occurring as Earth warms due to two main factors: melting of land-based ice such as glaciers and ice sheets, and the expansion of seawater as it warms鈥攖ermed thermal expansion. Previously unknown was whether the rate of thermal expansion, which accelerates with warming, will also affect the variability of sea level.

In a , a team led by Matthew Widlansky, associate director of the , assessed future sea-level projections from global climate models. The team found that while future sea-level variability changes are uncertain in many locations, nearly all of the 29 models they analyzed agreed on an overall tendency for the variability to increase on seasonal-to-interannual timescales.

“Whereas it is well understood that the rate of global mean sea-level rise will accelerate with future warming, in part due to the oceans expanding faster at higher temperatures, it was previously unexplored how this nonlinear thermal expansion property of seawater will affect future sea-level variability,” said Widlansky.

“Following thermodynamic laws, sea-level variability increases in a warmer climate because the same temperature variations, for example related to the seasonal cycle, cause larger buoyancy and sea-level fluctuations,” added Fabian Schloesser, a researcher at the 糖心Vlog官方 Sea Level Center who collaborated on the study.

In places where changes due to ocean thermodynamics and other climate variability processes align, the team found the largest increases in future sea-level variability.

Coastal flooding occurs increasingly often due to a combination of slowly rising sea levels and ocean variability. The new findings therefore further emphasize the importance of sea-level monitoring and forecasting.

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–By Marcie Grabowski

As sea level continues to rise, extreme high tide events cause Honolulu to experience flooding not just from water washing directly over the shoreline, but also from groundwater inundation as the water table is pushed toward the surface, and reverse flow through the municipal drainage system. , researchers at the University of Hawaiʻi at Mānoa (SOEST), found in the next few decades, sea-level rise will likely cause large and increasing percentages of land area to be impacted simultaneously by the three flood mechanisms.

Further, they found that groundwater inundation represents the most extensive flood source, while direct marine inundation represents the least extensive—only three percent of the predicted flooding.

“This is significant because many people think that sea level rise can be mitigated by seawalls,” said Shellie Habel, lead author of the study and coastal geologist and extension agent with the and . “But a seawall will not stop groundwater inundation. Our results highlight the need to readjust our thinking regarding the flooding that accompanies sea level rise. We want to be sure to implement flood management strategies that will be effective at mitigating flooding.”

This requires that all types of flooding be thoroughly assessed.

Identifying vulnerable locations, infrastructure

Habel and co-authors developed a method that identified the various flood types and their extent. Flood maps were produced by simulating flood locations and depths generated by each of the three mechanisms and by overlapping the simulations to identify areas vulnerable to combined flooding over the coming decades.

Colleagues at the then developed a statistical model that considers predicted tide and projected magnitudes of local sea-level rise to establish the frequency with which flooding is likely to occur in given locations. With these flood simulations, the research team assessed critical infrastructure that is likely to fail and cause direct impacts, such as dangerous or impassable roadways, storm drainage inlets likely to fail or act as pathways for additional flooding, and non-functional or flooded cesspools.

The impacts were found to be widespread among Honolulu鈥檚 heavily densified primary urban center. This work along with planned collaborations will provide information that can inform the development of short-, mid- and long-term flood management strategies.

For more see .

—By Marcie Grabowski

The received $477,079 from the National Oceanic and Atmospheric Administration (NOAA) for the International Research and Applications Project, designed to support international, decision-based research on climate-sensitive health risks in partnership with the (RISA) program.

The grant will support collaboration between the Pacific RISA program, NOAA and the to conduct research on climate-induced migration from the Marshall Islands to Hawaiʻi and the U.S. mainland.

Changing temperatures, rainfall and sea levels threaten the habitability of small islands and atolls, with associated health impacts such as gastrointestinal illnesses, kidney disease and vector-borne diseases.

The Marshall Islands鈥� healthcare systems are unprepared to confront the impacts of climate change, which exacerbate overcrowding and poor sanitary conditions. In response to these complex factors, many Marshall Islands residents are relocating to other areas.

The project will expand the knowledge about vulnerability to climate change in the Marshall Islands, particularly where climate stressors lead to health impacts. It aims to improve the use of climate information to better serve migrant communities from the Marshall Islands, informing health professionals, policy makers and community organizations in sending and receiving locations about the climate-related health risks that migrants are experiencing now or expected to face in the future.

Although 糖心Vlog官方 and the East-West Center are separate institutions, they have long been close partners and neighbors.

New estimates derived from an international effort that includes researchers predict that many low-lying atoll islands throughout the Pacific and beyond may become uninhabitable by mid-century. The combination of rising sea levels and wave-driven flooding will cause frequent damage to infrastructure and will irreversibly contaminate island freshwater resources by 2030-2060, according to a .

Researchers from the U.S. Geological Survey (USGS), National Oceanic and Atmospheric Administration, 糖心Vlog官方‘s (IPRC) and other entities improved estimates of atoll habitability by considering not just sea level rise, but also the effects of wave activity that flood low-lying islands with elevations of less than two meters.

Previous studies have considered only the hazard from the rise in average sea level gradually inundating the atolls and estimated that the islands would still be livable until 2100 or later. This study, however, focusing on Roi-Namur Island of Kwajalein Atoll in the Republic of the Marshall Islands, includes the additional effects of waves, which begin to have serious consequences far sooner.

With multi-meter-high waves riding a higher average sea level, active flooding can occur more frequently as seawater breaches coastal berms, damaging coastal infrastructure and soaking into the shallow freshwater lens, contaminating the limited aquifer. Subsequent rainfall can replenish the freshwater of the aquifer over time, but if a second flooding event occurs too soon, salinity levels in the aquifer will remain too high for safe drinking.

“The tipping point when potable groundwater on the majority of atoll islands will be unavailable is projected to be reached no later than the middle of the 21st century,” said Curt Storlazzi, USGS geologist and lead author of the new report.

Accurate climate models for the area were key to establishing this timeline. of IPRC and of the evaluated 41 global climate models for those that best simulated recent conditions and trends (precipitation, sea surface temperatures, wind variability, etc.) in the Pacific and Indian ocean regions. From this pool, they selected five models that best captured past patterns and used them to project future conditions, particularly storm activity, each decade until 2100.

“The worldwide teamwork is the beauty of this project, with all the different modeling aspects—climate, wave dynamics, groundwater hydrology—all brought together so smoothly and efficiently,” said Annamalai. He emphasized that the wave-driven flooding, compounding sea level rise, is the key to this new story, as the wave hazard “adds flame to the fire.”

Storlazzi notes that their results are applicable to low-lying islands throughout the Pacific and beyond, underlying the urgency to evaluate which islands are most vulnerable and to begin exploring possible political and engineering solutions. Annamalai plans to expand on this work by applying the same techniques to island groups in the Indian Ocean (the Seychelles and the Maldives) where communities are already suffering greatly from increased cyclone activity.

—By Rachel Lentz

Over the next three years, the 聽in the at the and聽its partners will receive more than $5 million from聽the in the Oceanic and Atmospheric Research line for sea level rise research.

One aspect of the new funding supports Multi-Model Seasonal Sea Level Forecasts for the U.S. Coast. It聽will combine several different models to produce experimental regional sea level outlooks months in advance for Pacific Islands聽including Hawaiʻi, Puerto Rico and the entire continental U.S. Given that no seasonal prediction of coastal high water events currently exists on a national scale, this project will be invaluable to community members and community planners for long- and short-term decision-making. Ultimately, the research team will develop a web portal to provide the regional sea level outlooks to the public, including high-water alerts, which could be used for new or existing NOAA coastal flood products.

“The occurrence, duration聽and amplitude of coastal flooding events are increasing with rising sea levels,” said Mark Merrifield, lead investigator of the new seasonal sea level forecasts project and former director of the Sea Level Center. “The ability to assess when high regional sea levels are likely to occur will benefit managers and decision makers involved in coastal flooding mitigation.”

The other aspect of funding provides ongoing support for the Sea Level Center聽to collect and quality control tide gauge data from around the world through a cooperative agreement between NOAA and the . The Sea Level Center聽is the only group in the world that provides the public with up-to-date hourly sea level data from a global tide gauge network. These data are essential for studying sea level extremes and monitoring long-term global sea level rise.

“Support from NOAA enables the Sea Level Center聽to serve as a data center for sea level observations and maintain tide gauges in the Global Sea Level Observing System,” said Acting Director聽Philip Thompson. “With this substantial investment in sea level research and observations via the聽Sea Level Center, and with sea level rise being a big issue for the state, we are proud to be taking the lead on these new and continued efforts.”

—By Marcie Grabowski