US Sea Level Rise: Why the Coasts Aren't Rising Equally

Global sea level is rising as the planet warms — but if you measure it at the shoreline, the numbers look wildly different from city to city. New York's relative sea level is up more than 30 centimeters since 1950, while Seattle's has actually fallen. The reason isn't that the ocean behaves differently in each place; it's that the land is moving too. This guide uses decades of tide-gauge records from four U.S. cities to show how much the sea has risen — and why local geology can matter as much as the global ocean.

How much has sea level risen?

The chart shows relative sea level — the height of the ocean measured against the local land — at four long-running tide gauges, expressed as centimeters above the roughly 1950 average. New York and the East Coast show the steepest rise, well over 30 cm in some places. The trend is unmistakably upward at most stations and, importantly, it has been accelerating: the rise in recent decades is faster than in the mid-20th century.

Why Seattle's sea level is falling

Seattle is the striking exception: its relative sea level has drifted down. That doesn't mean the Pacific is shrinking — it means the land there is rising faster than the water. The Pacific Northwest sits on a tectonically active margin where the ground is slowly being lifted, outpacing the ocean's rise. Relative sea level is a tug-of-war between rising water and moving land, and in Seattle the land is winning — for now.

The East Coast is sinking, the West is rising

The broad pattern: much of the U.S. East and Gulf coasts are slowly subsiding (sinking), which adds to the global rise and produces the fastest relative sea-level increases in the country. Parts of the West Coast and Alaska are being uplifted, partly offsetting the rise. This is why a national average is misleading for planning — what matters to a city is its own combination of global ocean rise plus local land motion.

What's driving the global rise

Underneath the local variation, the global ocean is rising for two main reasons: water expands as it warms (thermal expansion), and melting glaciers and ice sheets add more water to the sea. Both are accelerating as the climate warms. For low-lying coastal cities, even modest rises raise the baseline for storm surge and high-tide flooding — so the slow upward creep on these charts translates into more frequent coastal flooding over time.