Guest Blog: What’s the Deal with Sea Level Rise?

Shannon Hulst Jarbeau is a Certified Floodplain Manager with the Cape Cod Cooperative Extension / Woods Hole Sea Grant, and recipient of the 2017 James Lee Witt Local Award for Excellence in Floodplain Management from the national Association of State Floodplain Managers (ASFPM). She provides technical assistance on floodplain and coastal management issues, with a special focus on the National Flood Insurance Program’s Community Rating System.

Here’s a question many of us in coastal management get asked a lot:

What’s the problem with sea level rise? Hasn’t sea level changed drastically since the start of our planet? Will we even notice if it increases a few millimeters a year?

Sea level has indeed changed substantially over geologic timescales. However, over the past 2,000 years or so, when civilizations developed, sea level remained relatively constant. During that time, those civilizations grew into the modern world that we tend to see as static, rooted in one location.

Sea level rise has remained relatively stable over the past several centuries, but has been steadily rising since the late 1800s and is expected to continue at an even more accelerated rate. Image: IPCC

Sea level rise is caused by two main factors related to increases in global temperature:

  • As the earth warms, the oceans warm and molecules spread out, causing the water to expand
  • The melting of land-based glaciers increases the volume of water in our oceans.

The rate at which sea level is rising globally is under constant study. However, on average, the projections have landed around 3 feet by 2100. This has varying effects on different coastlines, as each part of the world has its own set of factors that affect these rates of change.

Sea level rise is typically measured in millimeter increases per year. That’s a small amount annually, but those millimeters add up over time. In particularly low-lying areas, formerly dry roads have become impassable with just slightly above average high tides.

Image: NOAA National Ocean Service

This means that people can’t come and go from their homes and workplaces, supply chains are interrupted, school buses must be re-routed…nothing major, but enough to cause some serious headaches.

In some areas wetlands are starting to drown, because the water is rising so fast that the plants cannot grow quickly enough to keep up. Drowned wetlands mean a loss of fish and shellfish habitat that drive coastal fishing economies.

Flooded salt marsh on Plum Island, Massachusetts. This wetland is frequently flooded, smothering plants with water and sediments. Image: Matt Kirwan

Beaches typically migrate inland over time as sea levels rise, but beaches that have houses, roads, and seawalls behind them are unable to migrate, so some of these beaches have begun to shrink or disappear at high tide. As beaches shrink, they may draw fewer people to those communities, reducing tourism income.

Common tourist attractions, developed beaches will shrink with sea level rise. Image: Dave via Flickr Creative Commons

A major concern with sea level rise comes with coastal storms. When a storm hits at high tide, it can cause significant flooding both on the immediate coast and far inland. That flooding can knock homes off foundations or simply saturate a house in enough water that it becomes unlivable.

A house on the North Carolina Outer Banks destroyed in Hurricane Isabel Image: Mark Wolfe/FEMA

Floodwaters pick up all manner of pollutants, from motor oil and household hazardous waste, to raw sewage from facilities overwhelmed by the volume of water, to even carcasses of animals unable to escape the flood.

Sea level rise can cause major storms to be more devastating than they would have been in the past.

These changes have the ability to affect all kinds of people and places in different ways. Scientists and politicians are aware of sea level rise and the changes it can bring and many communities are making changes today to adapt to sea level rise. While there is no clear solution yet, an entire economic sector of Water Management is emerging, creating jobs and seeking solutions to ensure that our communities can continue to thrive.


For more information about sea level rise, check out Surging Seas

Learn about how communities are adapting to sea level rise at the EPA’s Climate Change Adaptation Resource Center, and how you can adapt with the U.S. Climate Resilience Toolkit.

And lastly, check out how sea level rise could affect your communities with this interactive map and this rendering of major U.S. cities.

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