In the coming decades, rising sea levels driven by climate change pose a significant threat to millions of Americans living along the nation's extensive coastline. This environmental shift, exacerbated by global warming, is expected to escalate the frequency and intensity of flooding, coastal erosion, and the deterioration of critical infrastructure.
Doug Marcy, a Senior Coastal Hazard Specialist at the National Oceanic and Atmospheric Administration's (NOAA) Office for Coastal Management, explained to Newsweek, "Generally, sea levels are going up globally due to increased ocean temperature, which actually expands as it gets warmer, and then contributions from glaciers, mostly the big continental glaciers."
This comprehensive statement underscores the interconnected factors contributing to sea level rise, emphasising both thermal expansion and ice melt as primary drivers.
Causes and Projections
The increase in global temperatures due to climate change has a direct impact on sea levels. As the atmosphere warms, so do the oceans, causing the water to expand. Additionally, glaciers and ice sheets are melting at an accelerated rate, contributing to the rise. Carbon dioxide (CO2) emissions are a significant factor in this process. These emissions trap heat in the atmosphere, which in turn warms the oceans and causes ice to melt. As Marcy pointed out, "As we go farther out, CO2 emissions will become more and more important, if we reduce them or not." This indicates the critical importance of addressing CO2 emissions to manage future sea level rise.
According to NOAA projections, sea levels along the U.S. coastline are expected to rise by an average of 10 to 12 inches by 2050. This is a considerable increase, especially when compared to the total rise measured over the entire last century, from 1920 to 2020. The extent of this rise depends on various factors, including the rate at which ice sheets melt and the global reduction of CO2 emissions. Marcy emphasised that the projections vary, particularly based on how ice sheets will melt—whether gradually or all at once—and the global efforts to reduce emissions.
Differential Impacts Across States
Not all coastal states will experience the effects of rising sea levels equally. Some regions will be disproportionately affected due to a combination of rising sea levels and land subsidence. Land subsidence, the gradual sinking of land, exacerbates the impact of rising sea levels and is particularly problematic along the East Coast. This phenomenon occurs due to natural geological processes and human activities, such as groundwater extraction. As a result, states on the East Coast and Gulf Coast, such as Florida, Virginia, North Carolina, and Louisiana, are expected to face the most severe consequences.
Peter Girard, spokesperson for Climate Central, a nonprofit organisation, told Newsweek, "People living on low-lying coastal land, like river mouths, are already facing higher flood risks because of the 20-40 cm [7.9—15.7 inches] of sea level rise measured along U.S. coasts over the past few decades. Their communities can expect the worst of the impacts as water levels continue to climb." This highlights the immediate and ongoing threats faced by coastal communities.
Immediate and Future Consequences
As sea levels rise, the U.S. coastline will gradually be inundated with water, leading to the submergence of low-lying areas. This will result in increased nuisance flooding, also known as tidal flooding or sunny day flooding, where flooding occurs even on clear days due to high tides exceeding normal levels. Furthermore, higher water levels will intensify storm surges during hurricanes and other major storms, causing more devastating coastal flooding.
The rising water tables also create additional problems, such as saltwater intrusion into agricultural lands and freshwater supplies. This contamination affects crop production and makes it difficult to obtain clean drinking water. Moreover, the rising water tables can overwhelm wastewater systems, leading to potential health hazards.
Economic Fallout
The economic impact of rising sea levels is substantial. According to NOAA's Office for Coastal Management, around 129 million people, or about 40% of the U.S. population, live in coastal areas. These regions hold a significant percentage of the nation's economy. If coastal counties were considered an individual country, they would rank third globally in gross domestic product (GDP), behind the entire U.S. and China. Margaret Walls, director of the Climate Risks and Resilience Program at the nonprofit Resources for the Future, explained to Newsweek that rising sea levels would have widespread economic impacts across the country.
This economic disruption could manifest in various ways. Local workers may find it challenging to reach their workplaces due to flooding, retail businesses could suffer from decreased customer access, and damage to roads and buildings could escalate. Walls elaborated, "It's not that businesses, especially big businesses, can't figure out a way to adapt. But there's all the folks who live and work in those locations who might not be able to still live and work in those locations. How are we going to deal with that?" This statement highlights the broader societal implications, emphasising the need for comprehensive adaptation strategies.
Additionally, rising sea levels could displace people, leading to internal migration within the country. This migration would have significant impacts on the coastal economies left behind and could strain infrastructure and social services in areas where displaced populations relocate. Flood damage is also costly. Girard noted that more than $8 billion of the flood damage caused by Hurricane Sandy in the New York area—about 13% of the total—could be directly attributed to sea level rise.
To mitigate these risks, states are implementing various adaptive measures. These preparations are highly location-specific and include constructing sea walls, storm barriers, and improving stormwater drainage systems. States are also elevating roads and critical infrastructure to make them more resilient to flooding and implementing land-use planning strategies to manage future risks.
