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Sea level rise refers to the increase in the height of the ocean’s surface, which affects coastlines around the world. Measuring this change is crucial for understanding the rate and effects of rising seas on both global and local scales. Scientists use two main tools to track sea level changes: tide gauges and satellites. Tide gauges, which provide us with data going back more than a century in some places, measure local or relative sea level by tracking water levels compared to the adjacent land. Over the last three decades, satellites equipped with radar altimeters started providing precise ocean heights from space across the globe. Tide gauges and satellites (altimetry data) together give us a comprehensive view of how sea levels are changing over time, offering insight into both regional and worldwide patterns.  

Climate change is the primary driver of contemporary sea level rise. Global warming due to anthropogenic emissions is contributing to sea level rise in two primary ways. First, higher temperatures cause the ocean water itself to expand - a process called thermal expansion. Approximately 90 percent of this additional heat is being absorbed by the oceans. Second, warming accelerates the melting of glaciers and polar ice sheets, adding large amounts of water to the oceans. Combined, these processes are pushing sea levels higher, making coastal flooding more frequent and intensifying the risks for communities and infrastructure near coasts. Rising sea levels not only creates stress on the physical coastline, but also on coastal ecosystems. For example, saltwater intrusions can contaminate freshwater aquifers, many of which sustain municipal and agricultural water supplies and natural ecosystems. As global temperatures continue to warm, sea level will keep rising long into the future due to the substantial lag to reaching an equilibrium.

Recent studies indicate that the pace of global sea level rise has doubled since the early 1990s (Hamlington et al., 2024), underscoring the extreme risk of coastal inundation due to sea level rise over the coming decades.   

Global and Regional Sea Level Change. While the overall rise in global sea level provides a broad measure, local sea level change can vary greatly due to regional factors. These factors include ocean currents, water temperature and salinity, vertical land movement (where land itself may rise or sink), and regional weather phenomena such as tropical cyclones or the El Niño-Southern Oscillation (ENSO). For example, the U.S. Gulf Coast is experiencing faster-than-average sea level rise due to a combination of sinking land and warmer ocean currents, while parts of Alaska have relatively stable or even decreasing sea levels (as measured by tide gauges) because the land is rising. This variability highlights that while global sea level rise is a universal trend, the effects and risks differ widely by region, posing unique challenges for each coastal community.  

CCKP is grateful for the support and expertise of NASA's Sea Level Change Team (N-SLCT). All data presented on this page is provided by N-SLCT. For additional details about the science behind sea level change, users are encouraged to visit: https://earth.gov/sealevel