How will sea level rise affect coastal cities?

Sea level rise will reshape coastal cities by increasing chronic flooding, worsening storm impacts, and altering the availability of land and freshwater. The principal physical drivers are thermal expansion of warming oceans and the accelerated loss of land ice, especially from Greenland and Antarctica. Eric Rignot at the NASA Jet Propulsion Laboratory has documented increasing ice-sheet mass loss that contributes directly to the global rise in mean sea level. The Intergovernmental Panel on Climate Change describes this trend as an accelerating global process that will continue for centuries without deep reductions in greenhouse gas emissions.

Physical drivers and regional variability
Local outcomes vary because sea level change combines global mean rise with regional factors such as vertical land movement, ocean circulation shifts, and gravitational changes as ice mass redistributes. Land subsidence from groundwater extraction or sediment compaction can amplify relative sea level rise in many delta cities. Coastal upwellings or changes in currents can produce regional departures from the global mean, so some ports face faster practical change than the worldwide average. Benjamin Strauss at Climate Central has produced maps and analyses showing how these combined effects create hotspots of exposure in places with dense populations and low elevation.

Consequences for infrastructure, communities, and ecosystems
Infrastructure designed for historical water levels will increasingly fail to provide reliable protection. More frequent nuisance flooding undermines roads, sewers, and transit systems and raises maintenance costs. Extreme sea level events compounded by storms will inundate critical facilities such as power plants, hospitals, and ports, disrupting services with economic ripple effects. Saltwater intrusion into groundwater and soils threatens drinking water supplies and urban agriculture, with long-term consequences for health and food security in coastal neighborhoods.

Socially, impacts concentrate on marginalized communities that often occupy lower-lying land with weaker political influence and fewer financial resources to adapt. Cultural and territorial losses can occur when heritage sites, burial grounds, or Indigenous coastal territories are flooded or forced to relocate. Wetlands and nearshore habitats that provide natural buffers and support fisheries face habitat loss, reducing biodiversity and the ecosystem services that many coastal communities depend on for livelihoods and cultural practices.

Adaptation choices and trade-offs
Cities will face choices among hard defenses, nature-based solutions, and managed retreat, each with technical and ethical trade-offs. Hard seawalls can protect dense urban cores but may deflect water and harm adjacent shorelines, while restoration of marshes and dunes can moderate wave energy and support biodiversity but requires space and time. Managed retreat avoids repeated reconstruction costs but raises complex questions about compensation, continuity of livelihoods, and loss of place. Institutions such as the National Oceanic and Atmospheric Administration and the National Academies emphasize integrated planning that accounts for long-term projections, equity, and the cascading risks to infrastructure and services.

Long-term governance and land-use decisions will determine whether coastal cities can maintain their populations and economies or must transform their form and function. Science from researchers and institutions provides the evidence base, but outcomes will hinge on policy choices, financing, and community engagement that balance environmental realities with social justice and cultural preservation.