Will Rising Sea Levels Drown Our Future?
I lived a good portion of my adult life in Larchmont, a small waterfront community about 20 miles from New York City. The town is nestled against Long Island Sound and most of the land is at sea level. My house was on a small hill, about 30 feet above sea level. Whenever it rained and the tide was high, the small turnabout at the end of the street would flood to a depth of four or five feet. It would take days for the sewage-infested salt water to recede. Some of the residents at the end of the block owned rowboats with which to navigate this pond. If their houses were unfortunate enough to be situated at that circle, they had to maintain powerful pumps in their basements.
One afternoon in the 1970s my wife and a few neighbors took their small children to look at a 50-foot-diameter pond which had appeared the night before. A man in a suit and tie and carrying a leather briefcase walked up to the edge of the pond. “Excuse me, ladies,” he said, He then took off his pants and carefully folded them across one arm. “Need to get home, you know, “he said with a smile and waded into the pond toward his flooded front yard. The water reached up to his waist. The women cheered!
How Did We Get All This Water?
Geophysicists believe that the atmosphere and the oceans began to accumulate about 3.8 billion years ago as gases escaped from the Earth’s interior.
The early atmosphere was saturated with vapor-rich fluids and gases emitted by volcanoes in the molten crust of the Earth. This water vapor was held in place by the Earth’s gravity. As the planet’s surface temperature fell below the boiling point of water, the water vapor condensed, and rain began to fall. This went on for millions of years. As the rainwater filled the hollows in the Earth’s surface, the primeval oceans formed.
The Changing Global Temperatures
Our planet has endured many glaciations — periods when the earth was covered by glaciers or ice sheets. The most recent occurred about 120,000 years ago. In some places, the ice was 10,000 feet thick. In the Northeast, a giant glacier carved out the Hudson Valley and its 315-mile-long Hudson River. Since then, our planet has existed in an interglacial period called the Holocene.
A 1.0 C (1.80 F) global temperature increase doesn’t sound like much. But 20,000 years ago, when global temperature dropped by 50 C, it caused an ice age large enough to bury large parts of North America.
According to the United States Geological Survey, during what’s known as the Glacial Maximum, permanent summer ice covered about 8% of the entire Earth’s surface, including 25% of its land area.
The enormous volume of water that was locked into glaciers and ice sheets caused sea levels to drop 125 meters (410 feet.) Until recently, glaciers and ice sheets continued to hold an enormous amount of fresh water.
Today, we are in a period of increasing global temperature. As the Earth continues to warm, the glaciers and ice sheets are melting at a runaway rate. NASA’s chart of global warming in the past few decades shows that since the 1960s, the Earth’s atmospheric temperature has increased nearly 10 C.
History of the Rise in Sea Levels
Global sea levels rise because of three factors: (1) thermal expansion of sea water as it warms (2) melting of land ice (glaciers, ice sheets) (3) decreases in the amount of water stored on land.
The Earth is now losing 1.2 trillion tons of ice each year. This loss will continue to accelerate as atmospheric temperatures rise. If all the ice now locked up in glaciers and ice sheets were to melt, sea levels would rise 216 feet. This would cause much of the inhabited land on Earth to disappear.
Average sea levels have risen over 8 inches (23 cm) since 1880. The last 3 inches were gained in just the last 25 years. Every year, the sea rises another 0.13 inches (3.2 mm). Rising sea levels inundate low-lying wetlands, erode shorelines, contribute to coastal flooding, and increase the flow of salt water into estuaries and nearby groundwater aquifers. Higher sea levels also make coastal infrastructures more vulnerable to damage from storms.
The sea level changes that affect coastal systems involve more than just expanding oceans, because the Earth’s continents can also rise and fall relative to the oceans. Ocean currents such as the Gulf Stream affect sea levels by pushing more water against some coastlines and pulling it away from others, raising or lowering sea levels accordingly.
Rising Sea Levels are Flooding Coastal Areas
If the current temperature rises by only 1.5 C, the sea levels will rise by 8 feet. When this happens, the following American cities will be underwater by 2100: Houston; Hoboken; Los Angeles; New York; New Orleans; Charleston; Seattle; Galveston; Key West; Atlantic City; Miami.
It no longer takes a hurricane to flood Miami. When the sun and moon align, the extreme resulting tides (called “king tides”) cause “sunny day” coastal flooding in the late fall and early winter. Under a full or new moon, the tide combines with the rising sea level to drive salt water through the drains and flood the downtown area. In 2020, Miami set daily high tide records for the weeks between late July and early August. No storms occurred during this period. The flooding consisted of salt water mixed with sewage.
Reviewing the situation, geospatial analyst Keren Prize Bolter notes that, “This [global warming] is the greatest threat humanity has ever faced. In South Florida, the water is coming in not just at the sides; it also comes up from below ground. Not even seawalls will stop the flow of water. This is bigger than the government.”
The problem in not just in Florida. The year 2020 set a new record for ocean heating. As humanity continues to pour greenhouse gases into the atmosphere, the oceans have absorbed more than 90% of the heat from these gases. This causes sea levels to rise as the water warms, because warm water occupies more volume than cold water. Higher sea levels are causally linked with severe hurricanes and typhoons. Because they move slowly, these deadly winds can cause storm that destroy everything in their paths.
Many coastal cities are seeking solutions to cope with the long-term threat of higher sea levels. Vulnerable communities need stronger seawalls and more water-absorbing vegetation to repel or capture encroaching sea water.
As sea levels rise, flood concerns in Miami have tripled since 1996. The Washington Post reported a 5.9-inch sea-level rise in Miami during this time period. Because Miami floods at just 16 inches above the flood stage. That increase — due to both sea-level rise and land subsidence — is highly significant. And as glaciers continue to melt, adding water to already swelling seas, the 85,000 Miami residents who live 3 feet below sea level must reconsider their situation and take action before it is too late.
Flooding Will Cause Millions to Flee Their Homes
By the end of the century, an estimated 630 million people will live on land below the projected annual flood levels. In the next few centuries, rising sea levels can create a world where flooding causes hundreds of millions of people to flee their homes and countries.
Sea level rise can dramatically increase migration by permanently destroying irrigated coastal agriculture and fresh drinking water supplies. Populations of coastal cities will be the first to evacuate their homelands. Food, shelter, and medical treatment will be scarce and fought over. Sea level rise can disrupt human systems, reduce property values, destroy infrastructure, and threaten such coastal livelihoods as tourism, aquaculture and fisheries. It also indirectly encourages migration by threatening job security.
The Army Corps of Engineers to the Rescue
What about our floods in Larchmont? After years of pleading, our community was able to get the Army Corps of Engineers to fix the drains and sewers in the area. The flooding abated somewhat, but the the most important outcome was that there was no more sewage in the floodwater. Eventually, the Corps fixed the drains and the waters receded, stabilizing the property values of the previously flooded houses.
In light of today’s rising sea level issues, the pond on our block was just a trickle. Yet it had a significant impact on the quality of life for those homeowners affected by the flooding. It also lowered their property values until the problem disappeared.
But what if the problem returns in the form of higher sea levels in Long Island Sound? Flooding will impact the lives of hundreds of thousands of people living along the coastline from New York City to Maine. Monetary losses will be in the trillions of dollars.
Yet the Federal government continues to look away and deny the problem as the seas continue to rise.
