What is sea level rise?

Imagine placing ice cubes in a glass of water on a hot summer day. The ice will melt faster than it would on a colder day. The same phenomenon is happening in the Arctic, where glaciers and polar ice caps have been turning from rock-solid structures to swelling liquid, resulting in huge volumes of water rushing into the sea.

What do historical data and projections tell us?

Models estimate that the world’s oceans have risen by as much as 0.2 m since the 1800s and will increase by up to 2 m by the end of this century. Unfortunately, evidence exists that this worst-case scenario is gaining momentum. While historical data reveals an annual sea-level rise (SLR) of 1.5mm between 1901 and 1990, this rate more than doubled to 3.6 mm per year from 2006 to 2015. An increase of less than half a meter may seem an insignificant growth over a period of 2 centuries, but a number of coastal cities and settlements around the world are already experiencing severe consequences from this rise.

What are the real-world implications of sea level rise?

In the latest UN Climate Change Conference (COP26), the president of the island country of Maldives made a global appeal to working to reverse this trend or “the Maldives will cease to exist by the end of the century.” True enough, reports published by the US Geological Survey (USGS) and the National Aeronautics and Space Administration (NASA) estimate that around 80% of Maldives will be uninhabitable by 2050. Another report released by a multi-agency effort headed by the National Oceanic and Atmospheric Administration (NOAA) predicts that the sea level along the US coastline is set to increase by 10-12 inches over the course of 30 years. The good news is that this estimate already incorporates land subsidence (another devastating result of the melting ice caps). The bad news, however, is that this 1-foot increase is enough to sink portions of major cities, altering life as we know it in this nation.

How do entire regions sink?

Land subsidence is the sinking of entire areas because of insufficient support from underlying earth materials. This phenomenon is commonly the result of excessive groundwater extraction. While groundwater pumping is vital to maintaining the water supply within communities, it depletes the water table and, over time, will cause subsidence above ground. In particular, coastal cities saw increasing rates of land subsidence due to unabated groundwater extraction. Jakarta, a major Southeast Asian city that is home to almost 11 million people, is the fastest sinking city in the world (mostly due to excessive groundwater pumping). Local experts estimate that the Indonesian capital sinks by as much as 6.7 inches annually and will be almost entirely below sea level by 2050 if this current rate holds. According to USGS and NASA, parts of the coastal cities of Houston, Texas, and New Orleans, Louisiana are sinking at a rate of 2 inches per year due to continuous groundwater withdrawal. Unfortunately, even with regulations that limit groundwater extraction, climate change is exacerbating these existing environmental woes. Glacial melting not only causes rising sea levels but also land subsidence, especially in areas along the coastline.

What is the Seesaw Analogy?

Picture kids playing on a seesaw. When one exerts weight on their side, they “sink,” while the other rises. A similar occurrence is happening to the lands surrounding the melting glaciers. During the last ice age, massive glaciers formed above some parts of the Earth’s surface and pushed the land underneath, while lifting the land along the coastlines. When these glaciers started to melt, inner land rebounded. Just as in a seesaw, the coastal areas that were raised with the forming of the glaciers will now sink. The Chesapeake Bay on the East Coast is a prime example of this seesaw phenomenon, where subsidence rates of up to ¹/₁₆ inches per year have been observed since the 1940s.

What do we do next?

The first step to solving a problem is recognizing the problem. Tackling a challenge like this will require unprecedented global commitments and collaborations. With the increasing number of studies, reports, and worldwide conferences to address these issues, we can see that both these undertakings (understanding the issue and brainstorming solutions) are in motion. Businesses and individuals have a duty to educate themselves on their own contributions to the changing climate and other sustainability concerns and follow this information up by making any necessary alterations to day-to-day activities.

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References

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USGS. (2013). Land Subsidence and Relative Sea-Level Rise in the Southern Chesapeake Bay Region. Reston: USGS. Retrieved from https://pubs.usgs.gov/circ/1392/pdf/circ1392.pdf Voiland, A. (2020). Preparing for Rising Seas in the Maldives. Earthobservatory.nasa.gov. Retrieved 19 April 2022, from https://earthobservatory.nasa.gov/images/148158/preparing-for-rising-seas-in-the-maldives