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Climate Connections: Sea Level Rise

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Over half of all Americans live within 50 miles of the coastline. Most major cities are found near bodies of water. Small island nations—particularly in the central and south Pacific ocean basins—are under threat of flooding as a result of rising sea levels.


Rising sea levels can negatively affect people living in coastal regions through increased coastal erosion. Shorefront homes and businesses are particularly vulnerable to coastal flooding or wave damage (SF Fig. 3.6 A). Low-elevation coastal communities also face greater risk from storms as a result of rising sea levels (SF Fig. 3.6 B).

<p><strong>SF Fig. 3.6.</strong> (<strong>A</strong>) A satellite photo of Waikiki, Hawai‘i, has been modified to show potential flooding due to sea level rise. Red indicates saltwater intrusion predicted by 2050.</p><br />
<p><strong>SF Fig. 3.6.</strong>&nbsp;(<strong>B</strong>) Coastal storm surge damaged Casino Pier during Hurricane Sandy in Seaside Heights, New Jersey.</p><br />


Sea levels are rising due to global climate change. This is occurring through two mechanisms: thermal expansion of water and melting ice formations on land. As world ocean temperatures rise with climate change, seawater expands to a slightly larger volume. Warm water has a slightly larger volume than cold water. Global climate change has also caused increased melting of major ice formations on land.


Melting land ice flows into the ocean and increases the sea level. However, not all melting ice increases sea level. It is a misconception that melting icebergs and sea ice causes the sea level to rise. A melting iceberg is similar to an ice cube melting in a glass of water. The volume of the water in the glass does not change when the ice cube melts. Melting sea ice does not contribute to rising sea levels. However, the increased rate of sea ice melting is an indication of global climate change.


<p><strong>SF Fig. 3.7.</strong> Changes in sea level height over the last 200 years</p><br />

The earth’s sea levels remained relatively consistent from the first century AD until 1900. Since then, scientists have observed sea levels rising by one to two-and-a-half millimeters per year. The most recent data collected by satellite instruments estimates a rate of three millimeters increase in sea level per year. This rate of sea level rise is expected to increase in the future as global climate change progresses (SF Fig. 3.7).

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.