WHY FLOATING HOMES MIGHT BE YOUR NEXT HOME
A long-term solution for projected flood prone areas and costal living
Pine Island Glacier, in the Antarctic, is changing quickly due to warming water. In 2013 satellites captured the calving of a large iceberg from the glacier. The iceberg was estimated to be 35 to 20 kilometers (22 by 12 miles) wide. (NASA Earth Observatory)
A sediment plume snakes from the south of the Mississippi River. The brown water of the Mississippi mixes into the blue water of the Gulf of Mexico. (Liam Gumley, Space Science and Engineering Center, University of Wisconsin-Madison and the MODIS science team)
Sea walls must be mantained consistently and will need to be built higher and higher as sea levels rises. This type of man-made barrier also has applications for the natural coastline. (Falcon Photography, Flickr)
The Portage Glacier near Anchorage, Alaska has retreated so much that it is no longer visible from the visitor center built for its viewing in 1986. (US EPA)
Flooding in Florida from a “King tide”. (Florida Sea Grant)
The ocean never stops moving
- When you visit the beach, waves roll in and recede and the tides rise and fall. These are small daily changes that balance out over time.
- But over the past century, the average height of the sea has risen more consistently—less than a centimeter every year, but those small additions add up. Today, sea level is 5 to 8 inches (13-20 centimeters) higher on average than it was in 1900.
- That's a pretty big change: for the previous 2,000 years, sea level hadn't
changed much at all.
The rate of sea level rise has also increased over time
- Between 1900 and 1990 studies show that sea level rose between 1.2 millimeters and 1.7 millimeters per year on average.
- By 2000, that rate had increased to about 3.2 millimeters per year and the
rate in 2016 is estimated at 3.4 millimeters per year.
Sea level is expected to rise even more quickly by the end of the century
- Scientists agree that the changes in climate that we are seeing today are largely caused by human activity, and it's climate change that drives sea level
- Sea level started rising in the late 1800s, soon after we started burning coal, gas and other fossil fuels for energy. When burned, these high-energy fuel sources send carbon dioxide up into the atmosphere. Carbon dioxide absorbs heat from the sun and traps it, warming the atmosphere and the planet.
- As the planet gets warmer, sea level rises for two reasons.
- First, warmer temperatures cause ice on land like glaciers and ice sheets to melt, and the meltwater flows into the ocean to increase sea level.
- Second, warm water expands and takes up more space than colder water, increasing the volume of water in the sea.
Sea level rise will hit the coasts the hardest
- Over the coming centuries, land that is today home to between 470 and 760 million coastal residents will be inundated by sea level rise associated with a 4 degree Celsius warming that will occur if we fail to curb the amount of carbon dioxide in the atmosphere.
Much of this population lives in cities
- Sea level rise already makes storms more dangerous, causing more flooding and damage in areas crowded with people. And it will affect different parts of the world differently, with some parts of the planet being particularly hard hit.
- Earth's most recent glacial period peaked about 26,500 years ago. At that time, around 10 million square miles (26 million square kilometers) of ice covered the Earth.
- The Laurentide ice sheet covered Canada and the American Midwest, stretching over Minnesota and Wisconsin south to New York and the Rocky Mountains. Across the Atlantic, ice blanketed Iceland and stretched down over the British Isles and northern Europe, including Germany and Poland.
- The Patagonian ice sheet crept north from Antarctica to cover parts of Chile and Argentina.
- The climate was colder and drier globally; rain was scarce, but pockets of rainforest survived in the tropics.
With so much of the planet's water tied up in ice, global sea level was more than 400 feet lower than it is today
- Over the past 20,000 years or so, sea level has climbed some 400 feet (120 meters). As the climate warmed as part of a natural cycle, ice melted and glaciers retreated until ice sheets remained only at the poles and at the peaks of mountains. Early on, the sea rose rapidly, sometimes at rates greater than 10 feet (3 meters) per century, and then continued to grow in spurts of rapid sea level rise until about 7,000 years ago. Then, the climate stabilized and sea level rise slowed, holding largely steady for most of the last 2,000 years, based on records from corals and sediment cores.
- Now, however, sea level is on the rise again, rising faster now than it has in the past 6,000 years.
- One property of water is that warm water takes up more space than cold water.
- So as the ocean warms from climate change, seawater expands to fill a greater volume and takes up more space.
- This is called thermal expansion, and it is responsible for one-third of sea level rise to date.
- The idea that water expands when heated seems strange, but it is a property of most objects that occurs at the molecular level. When water molecules are heated, they absorb energy. That energy causes the molecules and atoms to move around more and, in the process, take up more space. If you heat up a cup of water, the small molecular expansions don't add up to a difference we can detect by eye. But when you have vast numbers of water molecules, like in the ocean, the tiny expansions add up to something we can see.
- Thermal expansion is an ongoing contributor to sea level rise as long as ocean water continues to increase in temperature.
- Glaciers and ice sheets, large land-based formations of ice, are melting as global temperatures rise.
- That meltwater drains into the sea, increasing the ocean's water volume and global sea level.
- Melting ice has caused about two-thirds of the rise in sea level to date, one- third from land ice in Greenland and Antarctica and one third from melting ice on mountains.
Ice sheets and glaciers in Greenland and Antarctica melt three ways:
- From above due to warming air,
- from the sides as they break off into the sea,
- from below due to warming ocean water where the ice extends over the sea.
- Because of this, the rate of ice melt varies from place to place as conditions change.
- The Arctic is warming more quickly than the Antarctic, which explains why the ice there is thinning more quickly.
- However, recent research suggests that the melting of Antarctica’s ice shelves may be unstoppable—although the process may take centuries.
New discoveries about sea level change are made all the time
- In the future, the melting of ice sheets will dominate sea level rise.
- Warming has already caused major changes in the ice sheets, continental masses of ice which hold a greater volume of ice than glaciers and ice caps combined.
- These changes are irreversible in the short term, says NASA's Eric Rignot, and it would take centuries to reverse the trail of ice retreat. In addition to polar ice, the melting of mountain glaciers, like those in the Andes and Himalayas, has caused an equal amount of sea level rise to date. However, because mountain glaciers include only one percent of all land ice, polar ice will eventually greatly surpass their contributions to global sea-level rise.
- As sea level rises, ocean waves won’t roll onshore and submerge houses and communities all at once like in a summer blockbuster. The first signs of sea level rise will be increased damage from hurricanes and other storms and even high tides. Minor and major flooding will become more frequent. Coastlines will erode and creep backward almost imperceptibly. In fact, all of these impacts are already happening.
- As the waterline creeps up along coasts, storms and flooding will happen more frequently and dramatically.
Think of the ocean as the launching pad for storms and floods:
- the closer the sea is to human communities, the easier it is for floods to reach homes, roads and towns.
- Flooding over roads, which is already becoming more common in some places during high tides, can cause traffic jams and block emergency vehicles from reaching flooded areas.
- Imperceptibly to us, flooding is already becoming more common along the eastern United States.
- A 2014 Reuters analysis found that, before 1971, water reached flood levels no more than five days every year (on average) in several U.S. east coast cities.
- Since 2001, however, that number has risen to 20 days or more (on average). At this point, each of these floods is a relatively minor event, maybe closing a few roads, some home damage or causing businesses to close for a period of time.
- But as they become more frequent, these inconveniences will add up and make people's lives harder, not to mention cost money because of damages.
- Likewise, flooding during storms—sometimes called storm surges—will reach farther inland as sea level rises.
- During hurricanes and other large storms (like Nor’easters), strong winds push water beyond the normal high tide mark; beach houses are often built on stilts to protect against these storm surges.
- They are likely to get worse as sea level rises due to increased flooding danger across the board.
- Additionally, as the ocean warms from climate change, it will provide more energy to hurricanes, potentially making them stronger.
- Over the next century, hurricanes are estimated to grow between 2 and 11 percent stronger on average, according to NOAA. Combined, these are the "one-two punch of rising seas," say researchers at Columbia University, increasing the reach and power of storm surges.
- Storm surges already present the biggest danger to human communities whenever a hurricane hits.
- During Hurricane Katrina in 2005, storm surges of 10 to 28 feet destroyed buildings in Louisiana and Mississippi, flooded parts of New Orleans, and killed (directly or indirectly) around 1,200 people.
- In 2012, 9-foot storm surges caused by Hurricane Sandy flooded parts of New York City's subway system and destroyed homes along the New Jersey coast. As sea level rises, dangerous storm surges will become more frequent and powerful.
- The strength of any given storm can't currently be directly linked to climate change.
As sea level rises, bigger floods will become more frequent.
- A few times a year, when the pull of the sun and the moon align to join forces, coasts are hit with extra-high tides called King Tides. While King Tides are normal, their recent impacts are not.
- Thanks to sea level rise, King Tides reach higher and further inland now than they did 20 years ago, causing flooding in Miami and along Florida's coast.
- To some, it's a preview of how sea level rise will cause more frequent and higher flooding on coastlines around the world. It's also a staging ground for how to protect against rising seas; already, new pumps are restraining the ever-higher King Tides—for now
- Not only King Tides, but everyday tides are also already causing nuisance flooding. Climate Central calculated that “roughly three-quarters of the tidal flood days now occurring in towns along the East Coast would not be happening in the absence of the rise in the sea level caused by human emissions.”Florida is the U.S. state facing the gravest consequences from sea level rise. According to NASA, three feet of water will ultimately inundate land along Florida's coast based only on the warming humans have caused so far.
Sea level is threatening Florida more profoundly than elsewhere for two main reasons:
- 1. First, its elevation is very low; like many areas along the U.S. Gulf Coast, much of the land sits within a few feet of high tide, ensuring that a small change in sea level is noticeable. 2. Second is that Florida sits on a bed of limestone, which is a very porous kind of rock.
- Saltwater readily infiltrates and erodes the limestone, driving flooding.
- Seawater is also likely to push its way into freshwater systems and drinking water reservoirs in these areas.
The U.S. National Climate Assessment, for example, estimates that:
- Sea level will rise between 2 and 6 feet by 2100.
- Sea level rise is a reality we will have to face
- There is some debate, but according to one study every 1°C of warming will cause sea level to rise by about 2.3 meters.
- So the sooner we can slow our warming trend, the easier it will be for future generations to adapt.
Holding Back The Sea
- Can walls hold the water back? Some seem to think so, at least in the short-term.
- Coastal barriers have been used for thousands of years, dating as far back as the ancient Roman Empire. Whether to make man-made harbors for shipping needs or simple walls in order to stop erosion, humans have attempted to engineer coastlines for a long time.
- The response to sea level rise is no different, and many communities plan to build barriers in order to protect homes and cities from the rising tide.
- With the predicted increase in storms (both their intensity and frequency) physical walls can act to reduce flooding that is extremely costly—more costly than building the walls themselves one study says.
This type of adaptation will likely increase as the costs of not building walls becomes more apparent over time.
- Building barriers won’t reduce sea level rise or even completely remove the impacts, but could greatly reduce costs and buy coastal residents some more time.
- Sea walls aren’t a one-and-done fix, however. They must be maintained consistently, as waves and salt quickly erode concrete, and as sea level rises they will need to be built higher and higher. This type of man-made barrier also has implications for the natural coastline. They can render sandy beaches useless for both humans and the animals that call it home—causing erosion and disrupting the natural movement of sand and waves.Some countries, like the Netherlands, have been dealing with these types of water issues for centuries.
The Dutch have found success at adapting to changing sea levels by using involved water management systems, encouraging the use of floating homes and generally incorporating adaptations into city planning. New plans involve
- “Room for the River,” which involve adaptations that allow for flooding, rather then simply trying to stop the water with dams and dikes.
NASA Climate page NASA - Visualization of regional patterns of sea level change Surging Seas - Climate Central NASA Images of Change NASA Climate Time Machine Tide gauge history Fifth Assessment Report from the Intergovernmental Panel on Climate Change News Articles: Rising Waters: How Fast and How Far Will Sea Levels Rise? Rising Sea Level Will Slow Earth's Rotation 3.2 Millimeters: A Troubling Rise in Sea Level Pacific Islands Take Steps to Counter Rising Sea Levels Scientific Papers: Links between climate and sea levels for the past three million years - Kurt Lambeck, Tezer M. Esat and Emma- Kate Potter Sea-Level Rise from the Late 19th to the Early 21st Century – John Church and Neil White Temperature-driven global sea-level variability in the Common Era – Robert Kopp, Andrew Kemp, et al. Probabilistic reanalysis of twentieth-century sea-level rise – Carling C. Hay, Eric Morrow, Robert E. Kopp and Jerry X. Mitrovica The multimillennial sea-level commitment of global warming – Anders Levermann, Peter U. Clark, et al.
BY THE OCEAN PORTAL TEAM REVIEWED BY DR. JOSHUA K. WILLIS, NASA-JPL, DR. ANDREW KEMP, TUFTS UNIVERSITY, AND DR. BENJAMIN H. STRAUSS, CLIMATE CENTRAL
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