Sea level rise | 1 of 2

Also, if you are interested in listening to this episode instead, here is the link to it: Sea Level Rise|1 of 2

Now when people think of the sea level rising, they do not see it as a grave problem. They believe it is caused by global warming and all it can do is raise the sea level by a couple of inches and that’s all. But what if I told you the consequences are much more serious. What if I tell you that if we do not do anything to solve the crisis, we will be living in a world where the Netherlands does not exist, where Shanghai is underwater, and most of the world’s coastal metropolises flooded? Now before we jump to solving the problem, we need to first understand the basic concepts of sea-level rise.

What is Sea-level rising and What Caused it?

Sea level rise is a term for describing how the sea level would rise, mostly because of human activity, but also sometimes because of natural factors.

The three main reasons warming causes global sea level to rise are: oceans expand, ice sheets lose ice faster than it forms from snowfall, and glaciers at higher altitudes also melt. Sea level rise since the start of the 20th century has been dominated by the retreat of glaciers and expansion of the ocean, but the contributions of the two large ice sheets (Greenland and Antarctica) are expected to increase in the 21st century. The ice sheets store most of the land ice (∼99.5%), with a sea-level equivalent (SLE) of 7.4 m (24 ft) for Greenland and 58.3 m (191 ft) for Antarctica. Each year about 8 mm (0.31 in) of precipitation (liquid equivalent) falls on the ice sheets in Antarctica and Greenland, mostly as snow, which accumulates and over time forms glacial ice. Much of this precipitation began as water vapor evaporated from the ocean surface. Some of the snow is blown away by wind or disappears from the ice sheet by melt or by sublimation (directly changing into water vapor). The rest of the snow slowly changes into ice. This ice can flow to the edges of the ice sheet and return to the ocean by melting at the edge or in the form of icebergs. If precipitation, surface processes, and ice loss at the edge balance each other, sea levels remain the same. However, scientists have found that ice is being lost and at an accelerating rate.

How sea-level rise is measured?

Sea level changes can be driven either by variations in the amount of water in the oceans, the volume of the ocean, or by changes in the land compared to the sea surface. The different techniques used to measure changes in sea level do not measure the same level. Tide gauges can only measure relative sea level, whilst satellites can also measure absolute sea-level changes. To get precise measurements for sea level, researchers studying the ice and the oceans on our planet factor in ongoing deformations of the solid Earth, in particular, due to landmasses still rising from past ice masses retreating, and also the Earth’s gravity and rotation. There are two main ways to measure, and they are satellites and tide gauges.

Satellites are useful for measuring mass regions at sea level, such as the substantial rise between 1993 and 2012 in the western tropical Pacific. This sharp rise has been linked to increasing trade winds, which occur when the Pacific Decadal Oscillation (PDO) and the El Niño–Southern Oscillation (ENSO) change from one state to the other. The PDO is a basin-wide climate pattern consisting of two phases, each commonly lasting 10 to 30 years, while the ENSO has a shorter period of 2 to 7 years.

Tide gauge data are used for regional differences. Some of the recorded regional differences are due to differences in the actual sea level, while others are due to vertical land movements. In Europe for instance, considerable variation is found because some land areas are rising while others are sinking. Since 1970, most tidal stations have measured higher seas, but sea levels along the northern Baltic Sea have dropped due to post-glacial rebound.

From the above two methods, we can see how sea-level rise is measured using different techniques. These sophisticated techniques can help us better understand what we have done to the world and can help us understand when it is the time of no return and what we can do about it.

The Severeness of the Problem

Now before the solution to the problem, I believe it is important for us to know the severity of it. In his article from the Guardian, Harold R Wanless states that there will be 3 feet of sea-level rise in 2050 if we leave the problem untended. Still a vague concept, well, Shanghai’s average altitude is 4 meters, with most of it even lower. The Netherlands has an altitude in the minus. Cities like Miami; countries like the Maldives would be completely underwater, and many state’s freshwater systems would crash. Also, because the altitude is always lower and fluctuates less along with costs, the five urban agglomerations are all coastal cities. This means if the sea level rises drastically in the next 2 to 3 decades, all of the world’s most prized city clusters would become aquariums. According to Scott A. Kulp and Benjamin H. Strauss from the magazine of Nature Communications, 200 million people in the world will live below the sea level line by 2100. An additional 160 million will be affected by higher annual flooding due to rising ocean levels.

As we can see that the consequences are severe, but we are still about 2 decades away from no return, and in the next episode, I am going to inform you on how countries are combating sea-level rise and what we can do to be of some help.