Sea Levels on the Move


National Geodetic Survey

Tides and Currents

National Office for Integrated and Sustained Ocean Observations


NOAA National Geodetic Survey

NOAA Center for Operational Oceanographic Products and Services

NOAA National Marine Sanctuaries Program, National Marine Sanctuaries Foundation

University of Wisconsin

Integrated Ocean Observing System

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The earth's climate is changing – and it's causing sea levels to change too. Even small changes in sea levels can dramatically alter coastal landscapes all across the world.

So continuously measuring sea level changes over the long term is the best way for scientists to understand and project how and when this will affect our communities.

High-tech instruments are used to take height measurements of the ocean and land. 

Measurements from tide gauges and satellites are combined together to get precise water height readings.  Data from land surveys using benchmark elevations and a high-precision GPS and global satellite system together provide accurate land height measurements.

Scientists combine the water and land height data to study and figure out two important things:
1. The average amount of sea level change that is happening on a global scale; and
2. The amount of sea level change that is happening at specific locations – like coastal cities and towns and why it varies in different areas of the world.

Scientists project sea levels will rise 8–17 inches this century, and this is faster than ever before in recorded human history. Coastal communities will lose farmland, fresh water supplies, and natural barriers against flooding.

Continually measuring and studying water height and land elevation changes is crucial to helping us plan and prepare for whatever a changing ocean brings our way.