Hovering more than 800 miles above Earth, farther than the distance from New York to Chicago, NASA satellites are powerful enough to measure sea level changes within a fraction of an inch. These measurements provide very accurate records of rising oceans.(1),(2) Using satellites and other tools, scientists observed nearly 7 inches of sea level rise since the 20th century.(1) According to historical records, sea levels are rising twice as fast in the last decade compared to the past 100 years.(3)
What 7 Inches of Water Can Do
While 7 inches of rising sea levels may not sound like a lot, NASA has found that every foot of sea level rise can cover 50-100 feet of beach.(4)
By mid-century, some areas will experience more than a foot of sea level rise, putting entire communities and countries underwater. The city of Norfolk, home of the world’s largest military base, anticipates a 1.5-foot increase by mid-century.(5)
Sea Levels Rise because Temperatures Are Rising
Due to extra greenhouse gases trapping heat in our atmosphere, the oceans and land are becoming warmer.(6),(7) This causes sea levels to rise in two ways:
First, the ocean absorbs 80 percent of the excess heat from greenhouse gases in the atmosphere, causing ocean temperatures to rise.(6),(7) When this happens, water expands as it warms up like mercury in a thermometer. As the water expands, it takes up more space and causes sea levels to rise.(8),(4) In other words, even without melting, sea levels would still rise because global temperatures are increasing.
Second, ice that sits on land, such as the Greenland Ice Sheet, is melting and flowing into the ocean. When it melts, this ice flows off the land into the ocean.(9)
Freshwater Ice Sheets Are Melting into the Ocean
Seventy-five percent of freshwater is frozen in sheets the total size of Russia. These sheets are melting into the ocean. Land ice sheets covering Greenland and Antarctica are already melting due to increased temperatures.(10),(11),(12) The Greenland Ice Sheet is about 2 miles high at its summit and covers 650,000 square miles. If it and the Antarctic ice sheet melted away completely, sea levels would rise by over 200 feet, according to the National Snow & Ice Data Center and the United States Geological Survey.(13) Though that’s unlikely in the foreseeable future, even a few inches of sea level rise could have a large impact on coastlines.(14)
National Infrastructure is Threatened
Our coasts are home to some of the nation’s most valuable infrastructure, from the ports that export our goods to the pillars of our energy system. These assets, designed for historic conditions, will be challenged by a more extreme climate. A government study projects that by 2030, nearly $1 trillion in energy assets will be at risk from climate change related impacts such as permanently higher sea levels and more intense hurricanes.(27)
Failure to protect one region can have national implications. The Gulf Coast, for example, produces about half of the nation’s oil and natural gas and is one of the most vulnerable regions to climate change.28 Companies across all industries are now reassessing their coastal infrastructure relative to projected increases, including Shell, Dow, and Merck.(29),(30),(31)
“Increases above 3ºC (5.4ºF) would…lead to sea level rises and disruptions in global supply chains due to severe weather events.”
— Nestle, one of the largest food and beverage companies
Flooding on a Sunny Day?
In some coastal cities, the sewer system relies on gravity to drain city streets. Rising sea levels have begun to cause sewer systems to back up, especially during high tides, causing flooding even when there’s no rain.(15)
What causes a sunny day flood?
In some coastal cities such as Miami, the sewer system relies on gravity to drain city streets. But rising sea levels have begun to cause sewer systems to flow backward, especially during high tides, causing flooding even when there’s no rain.
Seawater Is Contaminating Drinking Water Wells
As sea levels rise, ocean water travels farther under land and contaminates drinking water wells. The effects of this event, called saltwater intrusion, will also be felt in other states as sea levels rise another 9-24 inches by 2060.(16)
Saltwater intrusion happens when rising sea levels push ocean water toward fresh water and up through underground wells. Overpumping groundwater worsens these effects. As water is pumped from the ground, it sucks saltwater inland the way a vacuum sucks up dirt. This suction pulls salty water away from the ocean and toward land.
Just a little saltwater can make a huge difference
Adding just 7 tablespoons of salt to 55 gallons of water makes it too salty for drinking. Even a small amount of saltwater can contaminate drinking water – and ocean water contains much more salt than this hypothetical tub.(26)
Florida’s drinking water is at risk
Florida is particularly vulnerable to saltwater intrusion because of the porous limestone underneath much of the state. Limestone is like Swiss cheese, with plenty of holes that allow ocean water to seep in easily.(18) The Biscayne Aquifer, which supplies drinking water to more than 5 million Floridians — more than a quarter of the state — is already starting to be polluted by saltwater intrusion. At Fort Lauderdale, on the north end of the aquifer, saltwater has crept 6 miles inland.(16)
As saltwater moves inland (blue line), it is coming very close to South Florida’s freshwater wells (brown areas).
Saltwater will continue to shift farther inland and closer to the vulnerable freshwater fields with rising sea levels.(19) The resulting costs associated with sea level rise are not cheap. A suburb of Fort Lauderdale has had to spend $10 million for new wells and buy half its water from other countries due to saltwater intrusion.(20) If sea levels rise 2 feet higher, which could happen as early as 2060, the majority of Florida aquifers may be poisoned beyond recovery.(16)
Southeast Florida is already vulnerable to other impacts
- Southeast Florida’s sea level has risen 12 inches since 1870.(21)
- 12 inches of additional sea level rise would displace more than 19,000 Miami-Dade residents.(22)
- 9-24 inches of additional sea level rise will occur in Miami by 2060, according to the U.S. Army Corps of Engineers.(23)
- $400 million is being spent to upgrade Miami’s drainage system, more than it spends on its police and fire departments annually.(24),(25)
- NASA: How Do We Know?
- NASA: JASON-2 Overview
- National Geographic: Sea Level Rise
- NASA: What If It Keeps Rising This Fast?
- Hampton Roads Transportation Planning Organization
- NOAA: Ocean Stored Significant Warming Over Last 16 Years
- NOAA: Oceans of Climate Change
- NOAA: Is Sea Level Rising?
- National Geographic: West Antarctic Glaciers Collapsing
- NASA: Global Ice Viewer
- NASA: Satellites See Unprecedented Greenland Ice Sheet Surface Melt
- NASA: West Antarctic Glacier Loss Appears Unstoppable
- National Snow & Ice Data Center
- NOAA: Sea Level Rise Scenarios
- Washington Post
- National Geographic: Rising Seas
- Earth System Science Alliance
- Climate Central: The Time Is Now for Sea Level Rise in South Florida
- Environmental Protection Agency
- Palm Beach Post
- NOAA: Tides & Currents
- Climate Central: Surging Seas
- NASA: Impacts of Sea Level Rise on Florida’s Domestic Energy and Water Infrastructure
- City of Miami
- Miami Herald
- ESSEA: Salt Water Intrusion
- Department of Energy
- Government Accountability Office
- Dow Chemical
- Sea Level Rise – NASA
- South Florida Saltwater Encroachment – SFWMD