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Overview

The Future of Sea Level Rise

Sea Level Rise Is Speeding Up

Sea level has risen over 6 inches nationally since 1950, but recently, its rate of increase has accelerated. In the last five years, sea level has risen 66% faster than the historical rate, and is now rising by an average of one inch every five years.1 While it took 60 years for the sea level to rise about 6 inches nationally,2 scientists now forecast that in just the next 20 years, the sea will have risen by another 6 inches.3

The rate of sea level rise is not the same all over the country. In some towns, the sea level is rising much faster than the national average. On the East Coast and the Gulf Coast, the sea is rising by one inch every three years due to sinking land and a slowing Gulf Stream. On the West Coast, the sea level is increasing at a slower pace than the national average because the land is actually rising due to shifting tectonic plates.

While it took 60 years for the sea level to rise about 6 inches nationally, scientists now forecast that in just the next 20 years, the sea will have risen by another 6 inches.
While it took 60 years for the sea level to rise about 6 inches nationally, scientists now forecast that in just the next 20 years, the sea will have risen by another 6 inches.

Forecast Curves

What Is the Forecast for Sea Level Rise?

Scientists are uncertain how fast the ocean will warm and the ice will melt. They expect water levels to continue to rise faster, but are not sure just how fast. Scientists from the National Oceanic and Atmospheric Administration (NOAA) use a global forecast which offers six projection curves.4 The two lower curves do not account for the recent increase in ice melt, so they are unlikely scenarios.

The graph below shows the range of the other four curves. Since the sea is rising by an inch every five years, we’re closest to the forecast shown in darkest red.1

Created with Highcharts 6.2.0National Sea Level Rise Forecasts

City officials need these projections

With these projections, officials can decide how houses should be built, where roads should be laid, and what must be done to protect against flooding from sea level rise. Local communities have already identified billions of dollars in projects needed to protect against sea level rise. Click here to see what kind of solutions are available to local communities.

Measurement

How Do Scientists Measure Sea Level?

Scientists have three tools to measure the sea level

Buoys
Buoys

Buoys off the coast float on top of the water and measure its depth. Scientists track high and low tides and then take an average of the sea level every day.5 The type of buoy used to measure sea level is called a moored buoy, and it comes in different types and sizes, depending on its location and what kind of measurements it needs to take. In addition to measuring sea level rise, these buoys can measure and transmit information such as wind direction and speed, air and sea temperature, and wave energy.

Satellites
Satellites

Satellites are able to measure sea level from outer space as they orbit the Earth and can accurately calculate the depth of the ocean within an inch. Since 2002, NASA has been taking gravity measurements of sea level and ice with the help of two GRACE satellites. In May 2018, the GRACE-FO was launched to continue the work of the previous GRACE mission.6 This new satellite pair will take measurements and test new technology for improving the precision of the measurements even more.7

Tidal Guages
Tidal Guages

A tidal gauge is a large tube in the ocean, like an upside down measuring cup, which measures how high the water moves up the tube. The measurements are taken by seeing how long an audio signal takes to bounce off the water’s surface and back up the tube. Though the mechanics of how the gauges work have changed with time and technology, these gauges have been measuring the height of the ocean every six minutes for over 20 years.8

Ice Impact

Why Is the Future Dependent on Ice?

The sea level is rising due to a number of causes, including warming waters that are expanding, a slowing Gulf Stream, and sinking land. However, melting ice from the North and the South Poles is the biggest contributor to sea level rise. Determining when and how much the ice will melt can be difficult. Scientists worry about Antarctica the most, because it contains 90% of Earth’s ice, and the rate of Antarctic ice melt has tripled from 2012 to 2017.9 Click here to learn more about the causes of sea level rise.

Created with Highcharts 6.2.0
Antarctica and Greenland Ice Melt Since 1992