Increased sea level can affect coastal cities, experts say

Brazil is preparing to host the 30th UN Conference on Climate Change (COP30) expected to take place in November 2025, in the city of Belém, Pará. One of the topics covered during the event will be the impact of sea level increase on the planet .

With the advancement of climate change over the years, the oceans have become one of the main topics of debate between organizations seeking to understand Earth’s climate future.

Even this theme involves the entire climate change ecosystem that influences the planet. For example, increased global temperatures contributes to ocean heating, which consequently causes the sea ​​level rise .

In an interview with CNN Eduardo Siegle, deputy director of the Oceanographic Institute (IO) of the University of São Paulo (USP), explains that there are two main causes for increasing sea level: thermal expansion of water and melting glaciers . He points out that current observations point out that sea level rose more than 20 cm in the last century.

“From the early projections, the observed sea level has reached or even overcome the worst projection scenarios. That is, the worst projections have been confirmed so far. For 2050, when compared to 2000, the sea level should rise between 15 and 35 cm globally . In specific regions, in which subsidence processes are present, these values ​​can be up to 30% higher, ”he points out.

Increased sea level affects coastal cities?

Any low altitude coastal region in Brazil or other parts of the world will be impacted by increasing sea level.

As a result, Professor Siegle states that many of these areas will face erosion processes caused by water and the disappearance of coastal environments such as beaches.

Currently, Brazilian cities such as Recife are already facing floods caused by Maré. However, experts warn that these Coastal floods tend to become more frequent by increasing sea level.

In addition, the invasion of saltwater in the coastal areas can compromise freshwater reserves of the water table and alter soil characteristics.

César Barbedo Rocha, professor at the USP Oceanographic Institute Department of Physical Oceanography, says avenues, ports, drainage systems and all coastal infrastructure are designed based on past decades level. I.e, Erosion caused by water elevation may affect this infrastructure.

“It is important to highlight that the ocean has absorbed about 90% of the extra heat generated by global warming in recent decades. This has helped to limit the increase in terrestrial surface temperature, but also increases the level of the sea and alters oceanic circulation patterns,” Rocha told Rocha to CNN .

Main causes of sea level increase

• Thermal Expansion of Water: In the first case, USP’s deputy director of the Oceanographic Institute (IO) clarifies that the increase in temperature causes water to expand, taking up more space in the oceans and raising its level;
• Continental melting: The second cause is related to the melting of terrestrial glaciers, which adds more volume of water in the oceans.

How does science measure the level of the sea?

Science monitors changes in sea level through different complementary technologies. According to Siegle, Marégraphs are one of the most common methods. Installed in coastal areas, these equipment records tidal behavior, allowing you to identify local variations at sea level over time.

Since the early 1990s, satellites also began to monitor sea level on a global scale with high accuracy to provide consistent data on ocean elevation. There are also GPS stations, which can provide information to correct variations.

Rocha adds that ocean heating is monitored through sensors installed on ships and autonomous buoys. With the combination of this data, it is possible to observe that The average global sea level has risen about 10 centimeters in the last 30 years – A trend that should continue to grow.

Sea elevation in Recife and Santa Catarina

In an analysis released by the US space agency (NASA), scientists identified an increase rate of 0.59 centimeters at sea level by 2024. Previous models foresaw a 0.43 centimeters increase, confirming that this elevation is occurring faster than expected.

According to Osvaldo Girão, professor of the postgraduate degree in Geography at the Federal University of Pernambuco (UFPE), Recife is in a geographical position favorable to the occurrence of floods. That’s why, It is one of the Brazilian regions most vulnerable to climate change, especially the increase in sea level.

“In considering the elevation of sea level, the city of Recife will be susceptible to the elevation that would initially threaten coastal areas of the center and the neighborhoods of Brasilia Stubborn, Pina and Boa Viagem, threatened by increased intensity and recurrence of river, coastal, and coastal erosion,” he said.

Girão also states that densely populated regions of the southern, such as the center of Florianópolis, have already faced these effects more often and intensity.

A recent example was the flood recorded in Porto Alegre, Rio Grande do Sul, in May 2024, caused by the large volume of rain and aggravated by weather tides and coastal winds.

Professor César Rocha points out that, in southern Brazil, especially in Santa Catarina, extreme natural events also aggravate cases of flooding and flooding.

For example, extratropical cyclones and hangovers cause strong winds, higher waves and drop in atmospheric pressure. Factors that contribute to the elevation of the sea and more coastal floods.

How to adapt to the increase in sea level

Dealing with the climate consequences of a planet is not simple, so there is no easy answer to solve sea level increase. But experts say there are techniques for reducing extreme scenarios.

Some of the ways are:

• Relocate infrastructure and residents: Removing construction and residents of the risk range can improve the protection of coastal areas;
• Restore coastal ecosystems: Recover mangroves, dunes and shellfies dissipate the energy of the waves and capture carbon;
• Rebuild dunes and restinga vegetation: The reconstruction of these areas returns sediment stocks, reinforces the beach and reduces erosion;
• Punctual rigid works: Coastal protection works are recommended only when indispensable to protect critical infrastructures.

In any case, the accumulated impacts of climate change are enough to maintain sea level rise for the next centuries.

Our current actions can accelerate or slow down this elevation. It all depends on how we will face climate change. There is still time, and a significant reduction in greenhouse gas emissions is critical to containing this advance .

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This content was originally published in sea level increase can affect coastal cities, experts say on CNN Brazil.

Source: CNN Brasil