The rise in sea level is one of the most worrying effects of global warming. Millions of people live on the shores and on low-lying islands, so if action is not taken, There will undoubtedly be massive migrations within a few decades.
Until now, it was thought that the average ocean level was rising at a rate of 1,3-2 mm per year; however, new research has shown that it rises faster.
During the last century The information scientists obtained about sea level rise came from a network of tide gauges that are located along the coasts. These instruments are very useful if you want to know how much has increased in these areas, but they will not give you an overall result since they will be determined, as explained by the lead author of the study, Sönke Dangendorf, by the vertical movement of land in the Earth's crust and by the regional variability patterns resulting from changes in ocean circulation, wind redistribution, or by the gravitational effects of the redistribution of water and ice masses on Earth.
Now scientists have altimeters that, on board satellites, monitor sea levels in all oceans.
So, to find out exactly how fast sea level has risen since the XNUMXth century, what they did was select the longest and highest quality records, and correct for any factors that could give an erroneous result, then arrive at a global average. In this way, they were able to discover that until 1990, sea level had risen 1,1 mm per year, but since the 1970s, it has increased considerably due to human impact on the environment.
With the rise in the global average temperature, the melting of the poles makes the coasts less and less unprotected.
We can read the full study here.
What is sea level rise?
Rising sea levels are linked to three factors, all caused by this persistent global climate change:
1. Thermal expansion:
When water warms, it expands. About half of the sea level rise of the last century is attributed to the fact that This phenomenon is attributable to ocean warming, which caused them to take up more space. For more information on how these changes affect the environment, you can visit the article on the adaptation of plants to climate change.
2. Shrinking glaciers and ice caps:
Every summer, large ice formations, such as glaciers and ice caps, gradually melt naturally. Normally, precipitation in the form of snow, which comes from seawater, is sufficient to balance the melting. However, persistently high temperatures caused by climate change have led to more ice melts than usual in summerIn addition to Decreased snowfall due to late winters and early springsThis imbalance causes an increase in water runoff into the oceans, which contributes to sea level rise. For a broader view of this phenomenon, see the article on the new study of sea level rise.
3. The loss of ice from Greenland and West Antarctica:
As with glaciers and ice caps, rising temperatures are causing the huge glacial mounds that cover Greenland and West Antarctica melting at a rapid pace. Scientists believe that the melting of the surface ice and the seawater that flows inland are seeping under the mounds, creating ice streams that move very quickly out to sea. Rising sea temperatures are causing the enormous ice shelves extending from Antarctica to melt from below, become brittle, and eventually break up.
When sea levels rise as rapidly as they have been, even the smallest increase can have dire consequences for people living on the coast. As seawater moves inland, it can cause soil erosion, flooding of wetlands, contamination of agricultural land and aquifers, contributing to the loss of ecosystem services. habitat for fish, birds and plants. In addition, global warming worsens the situation, as explained in the article on the effects of climate change in Germany.
Rising sea levels coincide with more dangerous typhoons and hurricanes, as they move more slowly and leave more rain, contributing to more powerful storm surges that can devastate everything in their path. One study found that between 1963 and 2012, nearly half of the deaths caused by Atlantic hurricanes were caused by storm surges.
Flooding on low-lying coasts is already forcing people to migrate to higher ground, and millions of people are threatened by flood risks and other effects of climate change, flood risk has increased globally, as mentioned in the article on floods in the coming yearsThe projected retreat of the coastline threatens basic services such as internet access, as much of the underground telecommunications infrastructure is in the path of rising sea levels.
Adapting to the threat
As a result of these risks, many coastal cities are already planning adaptation measures to cope with long-term projections of rising sea levels, which typically entail considerable costs. Build dikes, redesign roads, and plant mangroves or other water-absorbing vegetation. These are options that are already in operation. A broader focus on these adaptations can be found in the article on investment in green infrastructure.
In Jakarta, Indonesia, a project worth more than €35,000 billion aims to protect the city with a nearly 25-meter-high levee. Rotterdam, Netherlands, home to the Global Adaptation Center, has offered other cities a model for combating flooding and land loss. The Dutch city has built barriers, drains, and innovative architectural structures, such as a "water plaza" featuring temporary ponds.
Of course, communities vulnerable to sea level rise have limited options in the face of rising tides. In the Marshall Islands, where rising sea levels are forcing a choice between relocating or raising land levels, residents will need help from other countries if they choose the latter. Therefore, community adaptation is crucial, as mentioned in Cities that could disappear due to global warming.
It is also relevant to mention that rising sea levels put cities like London and Los Angeles at risk, something that is detailed further in This studio.
How has sea level risen in recent decades?
According to the US National Oceanic and Atmospheric Administration (NOAA), Sea level has risen between 21 and 24 centimeters since 1880This growth, in addition to contributing to the coastal erosion, increases the flood riskA clear example is Spain, specifically the Ebro Delta, one of the regions most threatened by flooding caused by rising sea levels. Other areas at risk include Doñana, La Manga del Mar Menor, and some municipalities in Cádiz.
In relation to this, it is important to mention that upload speed is increasing and has doubled over the course of the 20th century. According to NOAA, approximately one-third of this increase has occurred in the last two and a half decades.
And the worst may be yet to come, because the forecasts are no more optimistic. This organization estimates that sea level is likely to rise by 2100. increase at least 30 centimeters compared to the level at the beginning of the century, "even if greenhouse gas emissions continue on a relatively low path in the coming decades." In this context, population adaptation is key, as mentioned in the article on the effects of climate change.
To illustrate the intensity and severity of the rise, it is important to mention that UN Secretary-General António Guterres has visited the Pacific Ocean nations of Tonga and Samoa in recent days, where he has met with local communities to discuss this critical issue. As this progresses, it becomes crucial to understand how sea level rise affects the region, as detailed in the article on differences between climate change and global warming.
What are the consequences of rising sea levels?
As we've seen, climate change and rising sea levels go hand in hand. But what are the consequences of this rise?
Climate change is widespread, rapid, and intensifying, according to a 2021 report by the Intergovernmental Panel on Climate Change (IPCC), and this will continue to translate into further sea level rise. Coastal areas will experience continued sea level rise throughout the XNUMXst century, contributing to the coastal erosion since the coastal flooding are more frequent and severe in lowland areas. This phenomenon also affects arid areas, as explained in the article on deserts threatened by climate change.
In this sense, IPCC experts assure that the phenomena related to extreme sea level that used to occur once every 100 years could be recorded every year by the end of this century. This increase in the frequency of extreme events is also related to the situation of the mammals and birds that adapt to climate change.
On the other hand, several studies predict an increase in flooding in the coming years in various parts of the world. It should not be overlooked that between 1993 and 2015, the risk of coastal flooding increased by almost 50% on a global scale, according to an article published in Nature Communications.Furthermore, another study published by the same journal indicates that, starting in 2050, coastal areas where 300 million people currently live could be flooded every year.
As indicated by Margarita Eulalia García, marine geologist and scientific researcher at the Oceanographic Center of Cádiz, "the most immediate impact will be produced by the marine invasion of coastal areas, where a very high population and many infrastructures are concentrated.”
In addition, rising sea levels threaten multiple infrastructures, according to NOAA: “Roads, bridges, subways, water supplies, oil and gas wells, power plants, wastewater treatment plants, landfills—the list is virtually endless—are all at risk from sea level rise.” In the natural world, “Rising sea levels create stress on coastal ecosystems that provide recreation, storm protection, and habitat for fish and wildlife.”. This is in line with what is mentioned in the article about medium-sized carnivores and climate change.
What causes sea level rise?
The rise in sea level is mainly due to thawing favored by global warmingThe Antarctic and Greenland ice caps and continental glaciers are the most important ice masses. What happens is that, as the temperature of the air and ocean water masses with which the ice caps come into contact increases, "these They merge and cause a rise in the level sea".
On the other hand, the expert in maritime climate and global warming, Màrius Tomé i Covelo, explains that the Increased temperature is associated with the thermal expansion of waterIn his own words: “Thermal expansion was responsible for about a third of the global sea level rise that occurred in the 1990th century up to XNUMX, and since then, melting from glaciers, continental ice sheets, and polar ice caps has been much more significant.”
The two main causes of sea level rise are:
- The melting of glaciers: Global warming is causing melting in Antarctica, Greenland and continental glaciers.
- Thermal expansion of water: Rising ocean temperatures cause the water to expand, contributing to sea level rise.
How does global warming affect the ocean?
Global warming has led to a significant increase in ocean temperatures, resulting in various consequences for the environment and humans. The oceans are responsible for absorbing much of the additional heat generated by human activities, and their warming not only affects sea level but also impacts marine and coastal ecosystems. To learn more about how marine life is affected, you can read the article on marine life and global warming.
Ocean temperatures have risen considerably since the 70s, and this has led to an increase in phenomena such as marine heat waves, which are episodes of abnormal ocean temperatures that can last for days or weeks. The IPCC has stated that human influence has been the primary cause of increased ocean heat, and this is harming marine life, including the loss of critical habitats such as coral reefs. To better understand the relationship between global warming and the ocean, you can consult the article on Antarctic krill and climate change.
Rising ocean temperatures also affect the marine biodiversityIt is estimated that more than half of marine species could be on the brink of extinction by 2100 if current levels of warming continue. With a 1.5°C increase, between 70% and 90% of coral reefs are projected to disappear, affecting thousands of species that depend on these ecosystems.
As the ocean warms, the acidity of the water also increases due to the absorption of CO2, which can lead to the death of sensitive marine species. Coastal areas are the most affected, where approximately 500 dead zones have been reported, with almost no marine life left due to the decrease in oxygen content.
Future projections of sea level rise
Sea level rise forecasts continue to be alarming. According to the IPCC, if greenhouse gas emissions are not drastically reduced, sea levels could rise between 30 and 130 cm by 2100 compared to 2000. This rise, in addition to causing damage to infrastructure, will also affect agriculture and food production due to saltwater intrusion into the soil. For more specific information on sea level rise, see the article on its acceleration.
As temperatures are projected to continue rising, rising sea levels could result in a migration crisis. Coastal communities, especially those in developing countries, will face the greatest challenges as populations are forced to move to safer areas. This could lead to social and economic tensions in already vulnerable regions, an issue that is also being studied. atypical cyclones.
What measures are being taken?
Faced with the looming sense of urgency, cities and countries around the world are taking steps to mitigate and adapt to the impacts of sea level rise. Some of these measures include:
- Building resilient infrastructure: Seawalls and barriers are being designed to protect coastal areas. For example, the project in Jakarta aims to build a seawall nearly 25 meters high.
- Improving urban planning: Coastal cities are updating their building codes to include stricter standards that take sea level rise into account.
- Restoration of natural ecosystems: Mangrove and coral reef restoration projects are underway to help protect the coast.
- Controlled migration: In some cases, relocating entire communities is being considered, such as in the Marshall Islands, where the population faces imminent flooding.
In this context, it is crucial that countries work together to address one of the greatest challenges of our time. International coordination is essential to share resources, technology, and effective strategies that ensure the survival of coastal communities and the protection of the ecosystems that sustain life on Earth.
