Sea level rise

The ocean is getting higher.

This happens for two main reasons. First, ice on land is melting. This extra water flows into the sea.

Second, the water is getting warmer. Warm water takes up more space. This makes the sea rise even more. Rising seas can cause floods near the shore. They can also hurt plants like mangrove swamps.

People are finding ways to stay safe.

The ocean level is rising around the world.

This change is happening faster than it has in 3,000 years. Since 1901, the average sea level rose by about 20 centimeters. Between 2013 and 2022, the rise sped up even more.

Two main things cause this rise. First, ice sheets and glaciers are melting. This adds new water to the ocean. This caused 44% of the rise between 1993 and 2018.

Second, the water is getting warmer. This leads to thermal expansion. This means warm water takes up more space. This caused 42% of the rise in that same time.

Rising seas bring many changes. They can cause floods and hurt coastal plants like mangrove swamps.

People live in places that might flood every year by 2050. Many people live on low islands in the Pacific. Some of these islands may become hard to live on. People can try to stay safe. They might build seawalls to block the water. They might also work to fix sand dunes on beaches.

The ocean level is rising all around our planet.

This change is a big deal for everyone living near the coast. Since 1901, the average sea level has risen by about 20 centimeters. This rise is actually speeding up lately. Between 2013 and 2022, the rate reached 4.5 millimeters per year. This is much faster than it has been for at least 3,000 years.

Scientists study this to help people prepare for the future.

There are two main ways this happens. One way is through melting ice. Ice sheets and glaciers are melting into the sea. This added water accounted for 44% of the rise between 1993 and 2018.

The second way is called thermal expansion. This happens when water gets warmer. Warm water takes up more space than cold water. This expansion caused 42% of the rise during that same time.

Many groups work to understand these changes. The Intergovernmental Panel on Climate Change, or IPCC, is a very important group. They have shared many reports since 1990. These reports help us see different ways the sea might rise. They use many tools to make their guesses. Some use math models of ice melting. Others use expert judgment from many scientists.

These models help us see what might happen by the year 2100.

Rising seas can change many things on land. They can cause more floods and higher storm surges. This can hurt coastal ecosystems like mangrove swamps.

It can also make it harder to grow crops. This happens when salt from the sea gets into the water used for farms. Many people live in places that might flood every year by 2050. This includes tens of millions of people. Twelve of the twenty most at-risk countries are in Asia. These include Indonesia, Bangladesh, and the Philippines.

Communities can take different steps to stay safe. Some people build hard structures like seawalls.

Others use soft ways to help. They might fix sand dunes or add more sand to beaches. This is called beach nourishment. Some people might even move away from the coast. This is called managed retreat. Different countries have different ways to handle these hard jobs.

The goal is to protect people and the places they call home.

Sea level rise refers to the increase in the average height of the world's oceans. This phenomenon is a critical indicator of global environmental change. It affects every coastal population on Earth through various mechanisms. These include increased flooding, higher storm surges, and more frequent king tides. Rising seas can also make tsunamis more dangerous for coastal residents.

The process of rising sea levels is driven by two primary physical mechanisms. The first is the melting of land-based ice, such as glaciers and ice sheets. Between 1993 and 2018, this melting accounted for 44% of the observed rise. The second mechanism is thermal expansion. This occurs because water expands as it absorbs heat. Thermal expansion was responsible for 42% of the rise during that same period.

Scientists use several different approaches to project future sea level changes. Process-based modeling uses ice-sheet models to compute melting. It also uses general circulation models to track rising sea temperatures and expansion. Another method is the semi-empirical approach. This uses statistical techniques and historical paleoclimate data to predict trends. Some researchers also use structured expert judgement (SEJ). This method combines the informed opinions of many different scientists to reach a consensus.

Historical data shows that sea level rise is accelerating. Between 1901 and 2018, the average sea level rose by approximately 20 centimeters. This rate has increased significantly in recent decades. For the decade between 2013 and 2022, the rate reached 4.5 millimeters per year. This is the fastest rate of rise in at least the last 3,000 years. Some recent studies suggest it is the fastest in at least 4,000 years.

Future projections depend heavily on human greenhouse gas emissions. The Intergovernmental Panel on Climate Change (IPCC) provides various scenarios for the year 2100. In a low-emission scenario, like SSP1-1.9, sea level rise might be limited to a range of 0.28 to 0.55 meters. However, high-emission scenarios could lead to much higher levels. Under these conditions, the sea could rise by 0.5 meters or even 1.9 meters by 2100. In the very long run, warming could cause a rise of over 20 meters in the next 2,000 years.

Rising seas create significant challenges for ecosystems and human infrastructure. Coastal ecosystems, such as mangrove swamps, may be lost to the water. In agriculture, rising salt levels in irrigation water can reduce crop yields. Damage to ports can also disrupt global sea trade. By 2050, tens of millions of people may face annual flooding. This number could grow to hundreds of millions later in the century.

Different regions experience sea level rise in different ways. Local factors like land subsidence, or sinking land, can make the rise feel much worse. For example, sea level rise in the United States may be two to three times the global average. Of the twenty countries most exposed to these changes, twelve are in Asia. These include Indonesia, Bangladesh, and the Philippines. Low-lying Pacific and Caribbean islands are also at risk of becoming uninhabitable.

Societies use various strategies to adapt to these changing conditions. Hard approaches include building seawalls to block the water. Soft approaches include beach nourishment, which adds sand to shores, or rehabilitating dunes. Some communities may practice managed retreat, which involves moving away from the coast.

These choices often depend on a nation's wealth and resources. While richer states may build large defenses, poorer nations may face greater difficulties in adapting.