Global sea level rise and implications

What is Sea Level Rise? What are the factors leading to Global sea level rise? What’s the difference between global and local sea levels? What are the Island Countries’ Sea Rise Vulnerabilities? What efforts are being made to combat sea level rise? Read further to know more.

Climate action is urgently needed, as stated in the newly released IPCC Assessment Report from Working Group I, “Climate Change 2021: The Physical Scientific Basis.” It offers one of the most thorough scientific analyses of the causes, effects, and science of climate change.

Sea levels have risen 15 to 25 cm (6 to 10 inches) since 1900, and the rate of rise is quickening, particularly in some tropical regions, according to UN climate experts.

The World Meteorological Organization just released the paper “Global Sea-level Rise and Consequences” (WMO). By the end of the century, the oceans could have risen by approximately one metre (39 inches) around the islands in the Pacific and Indian Oceans if current warming trends continue.

What is Sea Level Rise?

• Sea level rise is an increase in ocean depth brought on by climate change, particularly global warming, and is primarily caused by three things: thermal expansion, glacier melting, and the loss of Greenland and Antarctica’s ice sheets.
• Tide stations and satellite laser altimeters are the main tools used to measure sea level.
• Less than a centimetre has been added to the sea’s average height annually over the past century, but those tiny increases add up.
  It is anticipated that in 2016, the rate will be 3.4 millimetres per year, up from roughly 3.2 millimetres per year in 2000.
• Throughout the past century, the sea level has been rising, and recently, the rate has quickened. Between 1880 and 2015, the average worldwide sea level increased by 8.9 inches. Compared to the previous 2,700 years, that is substantially faster.
• SLR varies from country to country. Due to subsidence, upstream flood control, erosion, regional ocean currents, changes in land height, and compressive weight of Ice Age glaciers, regional SLR may be higher or lower than global SLR.
• The Special Report on the Ocean and Cryosphere in a Changing Climate, published by the IPCC, highlighted the catastrophic changes occurring in oceans, glaciers, and ice deposits on land and at sea. According to the analysis, oceans should rise between 10 and 30 inches by 2100 and temperatures should rise 1.5 degrees.

Why is the Global sea level rise a Major Concern?

• Because oceans warm slowly, sea level rise will continue even after emissions stop growing.
  Even in the low emissions scenarios, sea level rise has consequences for the future because it is irreversible on a century scale.
• Warm ocean waters expand, land-based glaciers melt, and the ice sheets in Greenland and Antarctica melt, all of which contribute to sea level rise.
• Projections based on organised expert opinions suggest that a sea level rise of up to 2.3 metres by 2100 cannot be completely ruled out.
• The world is expected to see a temperature increase of more than 3°C this century, according to the UN Environment Programme Emissions Gap Report (double the Paris Agreement aspiration). Also, predictions of sea level rise for warming exceeding 3°C are incredibly questionable.
• It is essential to comprehend the threats posed by climate change and sea level rise in the twenty-first and twenty-second centuries.

Factors leading to Global sea level rise

Experts concur that human activity is substantially to blame for the climate changes that are currently being seen and that climate change is what is causing sea levels to increase. There are three main causes of the change in sea levels, all of which are brought on by ongoing global climate change:

Thermal Expansion:

• Water expands as a result of a rise in temperature, which causes oceans to occupy more area and the sea level to rise.
• Water expands as it warms up. Warmer oceans simply take up more space, which accounts for around half of the sea level rise over the past 25 years.

Global Warming:

• Global warming has grown as a result of the ice sheets in West Antarctica and Greenland melting. This process is harmed by freshwater seepage from the surface because it causes the ice streams to slide more quickly by acting as a lubricant.
• In other words, the ice sheets are pumped with clean, fresh water, which causes the ice to melt, weaken, and collapse into the sea, raising the sea level.
• Large ice structures like glaciers and ice caps are subject to melting but do not reform. During the summer, these enormous frozen formations frequently partially decomposed, but when winter temperatures arrived, they resumed their solid form.
• Due to global warming, snowfall is softer, winters last longer, and springtime arrives earlier, causing ice to not recombine as frequently or in the same amount.

Seasonal Change:

• An important factor in the intra-annual rise in sea level is the annual warming/cooling cycle, which occurs in each hemisphere and causes the seas to warm and expand in the summer before cooling and contracting in the winter.
• Because of this, sea levels in both hemispheres are higher in the summer and early autumn and lower in the winter and early spring.
• Moreover, more water is held on land during the Northern Hemisphere winter than in the ocean, which lowers the global average sea level at this time of year.

Impact of Global sea level rise

A significant economic, social, and humanitarian challenge is the sea level rising. According to the research, it endangers human life and means of subsistence as well as coastal farmlands, water reserves, and infrastructure resilience.

Coastal Flooding:

• Eight of the top ten largest cities on the planet are located close to a shoreline, which is at risk from coastal flooding.
• Jakarta (Indonesia) is renowned as the city that sinks into the ground at the quickest rate in the entire globe, roughly 25 centimetres every year.
• Guangzhou, Jakarta, Miami, Mumbai, and Manila are more cities that frequently appear on lists of cities at risk from climate change.

Destruction of Coastal Biodiversity:

• SLR may result in severe erosion, inundation of wetlands, salt pollution of aquifers and agricultural soil, and loss of biodiversity habitat.

Dangerous Storm Surges:

• Hurricanes and typhoons are becoming more dangerous due to rising sea levels, which is resulting in loss of life and property.

Lateral and Inland Migration:

• People are being displaced and evicted due to flooding in low-lying coastal areas, which is contributing to a global refugee crisis.

Effect on Communications Infrastructure:

• Basic services like internet connectivity are in danger due to the possibility of rising coastal water levels.

Threat to Inland Life:

• Increasing sea levels might endanger life further inland by contaminating soil and groundwater with salt.

Tourism and Military Preparedness:

• A rise in SLR will also have a severe impact on military readiness and coastal tourism.

Submergence:

• Although the sea-level rise is not uniform globally and differs locally, the report warns that prolonged and increasing sea-level rise would encroach on coastal infrastructure and settlements and expose low-lying coastal ecosystems to submersion and destruction.

Food insecurity:

• Increases in the frequency, intensity, and severity of droughts, floods, and heatwaves, as well as continued sea level rise, will increase risks to food security in vulnerable regions. Climate change will also put increasing pressure on food production and access, particularly in vulnerable regions, undermining food security and nutrition.

What’s the difference between Global sea level rise and local sea levels?

• The relative sea level trend and the global sea level trend are two distinct metrics. In the same way that the Earth’s surface is not flat, neither is the ocean’s surface; as a result, worldwide sea level changes do not occur at the same rate.
• Due to a variety of local factors, such as subsidence, upstream flood control, erosion, regional ocean currents, variations in land height, and whether the land is still recovering from the compressive weight of Ice Age glaciers, sea level rise at particular locations may be greater or less than the global average.
• Tide stations and satellite laser altimeters are the main tools used to measure sea level. The height of the sea as measured along the shore about a particular place on land is what tide stations all around the world tell us about what is happening locally.
• We can determine the average height of the entire ocean from satellite readings.
• These resources, when combined, show us how our ocean sea levels are altering throughout time.

Vulnerability to Island Nations due to Global sea level rise

• The IPCC report noted that the global mean sea level in the Indian Ocean is rising at a rate of 3.7 metres per year and that extreme sea level events, which were previously seen roughly every year, will now be more common and severe, leading to coastal flooding in low-lying areas and coastal erosion.
• For the Indian Ocean’s low-lying island nations like the Maldives and others, this poses a serious concern.
  Sea level rise poses a serious threat to even the coastal regions of countries like India and Africa.
• The coasts will be the hardest damaged by sea level rise. If we don’t reduce the quantity of carbon dioxide in the atmosphere, land that is currently home to between 470 and 760 million coastal dwellers will be submerged by sea level rise related to a 4-degree Celsius warming in the next centuries. This group resides largely in urban areas.
• Storms are already more dangerous due to sea level rise, which also increases flooding and damage in populated areas. Also, it will have varying effects around the globe, with some regions of the planet being particularly heavily struck.

Vulnerability in India due to Global sea level rise

• India’s coastal communities are at risk from storms and sea level rise.
• The frequency and severity of storms will increase due to climate change. Flooding, torrential rain, and storm surges will accompany them.
• Even the 0.1 to 0.2-metre rise projected for India over the next few decades has the potential to often flood the shore.

Various steps are taken to tackle Global sea level rise

In particular, at the coast, urban systems are essential, interconnected areas for enabling climate-resilient development. Given that, as of 2020, 896 million people resided in the Low Elevation Coastal Zone worldwide, and that number may rise to more than 1 billion by 2050, coastal towns and communities are crucial to the transition to more climate-resilient development.

These individuals, along with related coastal development and ecosystems, confront growing climate-related hazards, such as sea level rise.

Relocation:

• Relocation has been planned as a mitigation technique in many coastal cities. For instance, Kiribati Island intends to move to Fiji, whereas Jakarta, the capital of Indonesia, is being moved to Borneo.

Building Sea Wall:

• To shield the city from floods, the Indonesian government started a coastal construction project in 2014 known as the Big Sea Wall, or “Giant Garuda.”

Using Beaches as Barriers:

• Like seawalls, beaches and dunes can serve as a natural barriers to block storm surges.
• More water can be prevented from reaching homes and highways the bigger the beach or the bigger the dune. Sand can be added by towns to expand beaches or stop them from eroding.
• It is possible to prevent flooding while protecting public beaches by using this kind of natural infrastructure.

Building Enclosures:

• To shield 15 countries in Northern Europe from rising sea levels, researchers have proposed the Northern European Enclosure Dam (NEED), which would completely enclose the North Sea.
• It was also determined that such gigantic enclosures could be beneficial in the Persian Gulf, Mediterranean, Baltic, Irish, and Red Seas.

Creating Natural Infrastructure:

• Restoration of natural infrastructure by coastal towns can serve as a safeguard against storms and coastal flooding.
• Barrier islands, oyster and coral reefs, mangroves, seagrass beds, and salt marshes are examples of natural structures that can absorb storm surges on their own or in conjunction with man-made structures like seawalls.

Architecture to Steer Flow of Water:

• Barriers, drainage, and avant-garde architectural elements like a “water square” with temporary ponds were constructed by Dutch City Rotterdam.

Global Plans to reduce the impacts of Sea Level rise:

• A $40 billion project in Jakarta aims to build an 80-foot seawall to safeguard the city.
• The Global Center on Adaptation is located in Rotterdam, which has provided other cities looking to fight flooding and land loss with a model.
• The Dutch city has constructed barriers, drainage systems, and avant-garde architectural elements like Water Square with its temporary ponds.

Way Forward

• Uncertainty about a metre or more of sea level rise before 2100 is due to ignorance and the inability to run models accurately enough. It can be risky to ignore the unknowns.
• Many actions must be taken in addition to stronger coastal management as part of the adaptation to sea-level rise.
• Coastal populations should be warned and safeguarded during extreme weather conditions.
• To preserve some susceptible places, natural and other barriers should be taken into consideration in a restricted way.
• For some very low-lying places, retreat should be a part of the adaptive methods.

Conclusion

Changes in sea level are a key indicator of global warming. Sea levels increased during the twentieth century at a rate of up to 0.06 m every ten years. The rate of sea-level rise has accelerated every decade since the 1950s. Model trials show that natural processes alone are insufficient to account for the rise in sea level over the 20th century.

The artificial forcing of greenhouse gases is the main factor causing the current sea-level rise. The geological history of the last three glacial-interglacial cycles shows a substantial positive correlation between atmospheric CO2 concentrations and sea levels.

Communities working together to tackle sea level rise are coming up with creative and ingenious solutions that are being seen around the world. Such solutions may serve as a model for other cities.

Article written by Aseem Muhammed