Do Sea Levels Rise Equally? You’d Be Surprised To Know That They Don’t

by Madonna Watts D'Souza

Do Sea Levels Rise Equally? You’d Be Surprised To Know That They Don’t

May 16, 2021

Contrary to popular belief, sea levels do not rise equally around the world. As shocking as this may sound, scientists explain why sea levels don't grow in the way we thought.

It’s all over the news. Wherever you go, you will hear it. Even your explore pages will have at least one post talking about this. No, we aren’t talking about some latest phone drop or game being released. We’re talking about the rising sea levels.

Yes, we get it, you’ve been hearing it a lot, and you may be slightly annoyed by us reminding you again. But, just for a second, can you envision the sea level rise? If you can imagine the glaciers melting and the freshwater combining with the salty ocean water, have you ever wondered how will this water spread?

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There’s a chance of an ice-free September in the Arctic by 2100.

Alarmingly Rising Sea Levels

Think about it. The Earth is somewhat a sphere (it bulges at the equator and flattens at the poles). 71% of Earth is covered by water and is held together by strong gravity (Unless you’re a Flat Earther, then we’re sorry). It seems rational to say that the melted water will spread evenly across Earth and ensure a sea-level rise, right? Well, it doesn’t happen like that.

For most of the 20th Century, the average global sea level has been rising. As per the United Nations’ Intergovernmental Panel on Climate Change, the sea levels have been increasing by 0.05 inches (1.4 millimeters) annually. However, from 2005 to 2015, the levels rose by 0.1 inches (3.6 mm) annually. As baffling as it sounds, sea levels rise does not increase equally across the Earth’s surface.

Scientists On Unequal Sea Levels

Kathy McInnes, a senior principal researcher and the leader of Climate Extremes and Projections Group with the Commonwealth Scientific & Industrial Research Organisation (CSIRO)’s Climate Science Centre in Australia, says, “Sea level rise isn’t very uniform across the globe.” Several places on Earth are experiencing a sea-level rise. However, some areas on Earth are experiencing a fall in sea-levels!

“There’s not a place that’s immune from sea-level change,” remarked Jacky Austermann, an assistant professor of ‘Earth and Environmental Sciences’ at Columbia University’s Lamont-Doherty Earth Observatory in New York. So, what’s the reason that’s causing a change in the sea-levels globally? By now, most of us know the answer. It’s Climate change.

Despite Earth being somewhat of a sphere, what exactly is Climate Change affecting that sea levels rising unequally? Why doesn’t the water spread equally across the globe? There are two key reasons why this happens- the gravitational pull of the ice sheets and thermal expansion is responsible for the unequal distribution of water.

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As sea ice and ice caps at both of the Earth's poles continue to melt at unprecedented rates, rising sea levels can put coastal and island communities at risk of flooding and water damage. PHOTOGRAPH BY GEORGE STEINMETZ

Climate Change A Factor

Since the global temperature is rising, it warms the air and water, warm water fundamentally expands, and the warm air is also notorious for melting away ice sheets as Glaciers melt into the oceans, the temperature rises.

Austermann outlined, “In Antarctica, warming oceans are the biggest contributor to the disintegration of ice sheets.” Due to thermal expansion, the oceans’ currents spread the heat through warms waters by moving both warm and cold ocean currents globally.

According to McInnes, “If there’s greater heat in few areas and less heat in others, warmer marine areas will expand more, while colder places will have less expansion. Atmospheric winds can also deplete and raise oceans.”

Apart from this, wind patterns are also changing with global warming.

Gravity Too?

It could be something new for you to read that even ice sheets can exert a gravitational pull, but yes, it’s true. Ice sheets aren’t tiny or just floating above the water surface, but they are gigantic with tonnes and gigatonnes of weight. Therefore, due to their size, they can exert a gravitational pull on the waters around them.

The Antarctic and Greenland Ice layers are so huge that their pull on the waters is powerful. Due to this reason, the sea levels here are rising. But happens when glaciers and ice sheets melt away?

When they melt away, not only is the water combining with the ocean, but the mass of those ice bodies decreases—a decrease in mass results in a weaker gravitational pull. Now there’s nothing too powerful to hold the water close, and hence the sea level falls here.

A real-life example would be the sea-level near the Greenland ice sheets is falling, but on the opposite side of the world, the water levels near the Antarctic ice sheets are rising. According to Austermann, “This pattern of sea-level change on the globe called a sea-level fingerprint is distinct for that particular ice sheet.”

Most Common Culprits- Humans

Apart from this, human activities are also responsible for the unnatural rise in sea levels. Now that we know the natural cause of sea-levels, we need to understand the artificial ways in which sea levels are worsened. Activities like fossil fuel excavations, groundwater transport, etc., contribute to a rise in sea levels.

With the increase in sea levels, many coastal cities are on the verge of drowning completely. Cities built on deltas, however, like Tokyo and New Orleans are sinking faster than ever. McInnes warns, “Some of these large mega-deltas are sinking at a much faster rate than sea level is rising. That’s a double problem, where the land is going down, and sea levels are going up simultaneously.”

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Sea levels are rising and will continue to rise for centuries to come according to the IPCC's Special Report on the Ocean and Cryosphere in a Changing Climate. Julie G via

This and a rise in sea levels will cause more frequent and intensified water disasters like floods. While scientists search for ways to reduce glacier melting, we must keep in mind how quickly earth’s temperature rises. If everyone isn’t aware of these disastrous phenomena’ aftermath, we all will have a hefty price to pay.


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