FL - When will Florida be completely underwater? A look at the future of sea level rise

What causes sea levels to rise?

Sea levels have risen and fallen throughout Earth's history as it passed through its ice ages and other geological changes. We're in a rising stage, aided by human-induced climate change. NOAA says the ocean is absorbing "more than 90 percent of the increased atmospheric heat associated with emissions from human activity."

Sea levels have been nearly stable "over the last few thousand years," according to the Florida Climate Center at Florida State University, but the global average sea level has risen about 7 to 8 inches since 1900 and nearly half of that has happened since 1993. It's speeding up.

The main reasons for global sea levels are:

• The Earth and its oceans are getting hotter, and water expands when it heats up.
• Melting glaciers add fresh water into the ocean.

Local sea levels may be rising faster or more slowly depending on local factors such as erosion, regional ocean currents, sinking land (subsidence), upstream flood control, and more. For a state surrounded on three sides by water, that's not something we can ignore.

How fast is the sea level rising around Florida?

Globally, the sea level is currently rising at about 1/8 of an inch every year, according to the National Oceanic and Atmospheric Administration (NOAA).

NOAA also measures relative sea level (RSL) trends, which are local sea level measurements made with respect to a local fixed reference on land. Relative sea level along the U.S. coastline is projected to rise, on average, 10-12 inches in the next 30 years, which is the same amount of increase that we saw over the last 100 years.

At Port Canaveral, sandwiched between the Banana River and Atlantic Ocean in Brevard County, the RSL is rising twice as fast as the U.S. coastline average, a 1/4 of an inch (6.25mm) a year, which works out to 2.05 feet in 100 years if you assume nothing else changes. Other areas around the Florida coast are rising more slowly, according to RSL readings, but they're still rising.

This doesn't sound like much but it adds up, especially since Florida has the second-lowest elevation of the states, an average of 100 feet above sea level, tied with Louisiana and just above Delaware. Florida also has the lowest high point: Britton Hill reaches just 345 feet above sea level. There are buildings here taller than that.

The average elevation in the Keys runs between 3.17 feet and just under 5 feet. The elevation in Cape Coral, one of the fastest-growing cities in the U.S., averages around 3 feet. Other danger areas include Hialeah, Pembroke Pines, Miami Beach, Plantation, Miramar and Fort Lauderdale, but everywhere in the state will feel some effects.

In a worst-case scenario — human emissions increase, Earth heats up faster, more intense storms pound the coastline, etc. — a rise of over 6 or 7 feet is possible by 2100, NOAA said in the agency's 2022 projections.

Note that different agencies have different predictions based on the available data, predictions are regularly adjusted as conditions change and more data becomes available, and every area of coastline has its own variables. Here's what different experts have said we can expect.

'There are no winners': Climate change is bad for everyone. But this is where it's expected to be worst in the US.

Right now: Increased flooding, rising seas already an issue

About 90% of the land mass of the Florida Keys is around 5 feet above sea level and they're seeing rising seas as a problem right now. In 2015, freak weather and high tides caused streets in Key Largo to flood and stay flooded. Efforts to improve drainage and water collection have already cost Monroe County millions, and in 2021 it announced plans to raise the height of 150 miles of the roads in the Keys over the next 25 years, adding more drains, pump stations and vegetation to absorb the seawater, at a cost of $1.8 billion.

Rising sea levels also mean flooding from storms has nowhere to go because saltwater is absorbed into the state's limestone foundation, leaving no room for drainage. Weeks after Hurricane Ian devastated Southwest Florida last year areas of the state were still flooded. NOAA's Annual High Tide Flooding Outlook predicts an approximate 300% increase in flood days in 2023 compared to 2000.

Risk Factor: Look up the risks at your address for flooding, fire, wind and heat

By 2040: Expect more than a half-a-foot raise

In the next 20 years, we can expect an average of 7 inches in sea level rise, according to projections from Resources for the Future, a group of economists and other experts focused on environmental and natural resource issues. But that's if global greenhouse gas emissions rise by 1% annually. If they increase more than the organization says we might see sea level rises of 10-16 inches by then.

By 2050: Increased tidal flooding, more major flooding

General projections put sea level rise at about a foot by 2045-2050. Using NOAA's Sea Level Rise Viewer, which extrapolates from the current best-available data, the effects can be seen. A 1-foot rise in the sea level sends water over streets in the Keys, Miami Beach, barrier islands from Melbourne to Palm Coast, and at least part of every coastal city in Florida. And flooding will be worse.

"By 2050, 'moderate' (typically damaging) flooding is expected to occur, on average, more than 10 times as often as it does today," NOAA said. "'Major' (often destructive) flooding is expected to occur five times as often in 2050 as it does today."

In a study by the Union of Concerned Scientists (UCS) and the online real estate appraisal site Zillow, researchers concluded that by 2045 (roughly the span of a current 30-year mortgage) about 64,000 residential properties in Florida, representing a market value of about $26 billion, could see "chronic inundation" (regular tidal flooding not related to any storm).

‍