Sea Levels May Be Rising Twice as Fast as We Thought

A recent study by NASA researchers suggests that sea levels are rising faster than previously believed. Until now, scientists assumed their measurements of global sea levels were basically accurate, leading them to estimate an increase in 4.7 inches over the past 100 years.

However, the new study, published in Geophysical Research Letters in October, suggests that these historical measurements may be dramatically inaccurate. In some areas, scientists may have underestimated sea level changes by a staggering 28 percent. Global sea levels may be higher than estimated as well, probably between 5.9 and 7.8 inches in the last century, although regional differences complicate this calculation.

So why, exactly, have existing measurements been so wrong? Simply put, it’s because the Earth’s oceans are huge, and accurately measuring sea level around the world is an incredibly challenging task. If sea levels rose evenly around the planet, the measurements would be easy, but NASA has found that the meltwater from the Earth’s major ice sheets tends to flow toward the southern hemisphere.

The problem isn’t that the technology is inaccurate or unreliable. We already have accurate and time-tested technology that can help us measure changes in the waterline: called coastal tide gauges, these instruments have been used for decades to monitor ocean conditions near major ports. In some places, these gauges have been continuously recording since 1700. The problem is where these tide gauges are located – mostly near North Atlantic coastal cities.

This may not make sense on the surface, but as Hakai magazine explains, it has to do with the Earth’s rotation and surprisingly inconsistent gravitational field. The Earth’s ice sheets are extremely heavy, so the Earth’s poles actually have stronger gravity than the rest of the planet. When the ice sheets melt, they shrink and that gravity is reduced, causing water to flow away from the area. The areas directly beside melting ice actually experience a small drop in sea levels as a result.

The authors of the new study were able to identify this pattern using NASA satellites to monitor shifts in the world’s oceans. The new climate model proposed in the paper takes this redistribution of ocean mass into account when measuring sea levels.

In other words, we’ve been looking in the wrong places. The regions experiencing the fastest rates of sea level rise are the ones with the least infrastructure to measure changes. This means our current data can’t accurately predict the changes likely to affect Australia, Africa, and equatorial Pacific Island nations.

Fortunately, this oversight is easy enough to solve. The readings climate scientists are currently using come mostly from 15 gauges in North America and Europe. By adding more of these gauges around the globe, we’ll have better insight into both global sea level rise and regional differences. As the oceans continue to shift in the coming decades, this will allow cities in threatened regions to begin planning how to address future flooding.

Photo Credit: Thinkstock

169 comments

Marie W.
Marie W9 months ago

Thank you for sharing.

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Robert N.
Rob Chloe Sam N10 months ago

It's scary what is happening to this world, If we do not change what future does our children have.

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Sam Dyson
Past Member 10 months ago

Tyfs

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Sam Dyson
Past Member 10 months ago

Tyfs

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Sam Dyson
Past Member 10 months ago

Tyfs

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Sam Dyson
Past Member 10 months ago

Tyfs

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Siyus Copetallus
Siyus C10 months ago

Thank you for sharing.

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Sherene Lambert
Sherene Lambert10 months ago

change needs to happen now

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bob Petermann
bob Petermann10 months ago

We need to make sure all climate deniers get this information. Thanks

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Angela K.
Angela K10 months ago

thanks for sharing

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