Global sea levels spiked dramatically in 2023

The ocean’s rhythm now echoes with a rising urgency – a stark warning delivered by recent NASA analysis. Global sea levels spiked dramatically in 2023, a consequence of both relentless climate change and a powerful El Niño event.

This revelation sounds an alarm for coastal communities globally, particularly island cities like Honolulu. Here, the advancing ocean poses a real, immediate threat. It’s not just a looming danger, but a current reality, altering daily life for many.

How do scientists chart sea levels?

Scientists use a range of advanced tools to calculate ocean height:

• Radar altimeters on satellites: Special instruments on satellites send microwave signals down to the ocean and measure how long it takes the signal to bounce back.
• Tide gauges: These instruments located along coastlines provide historic long-term data for comparison.
• Other satellites: Scientists use information on ocean temperature, ice loss, and even Earth’s gravity field, which all affect sea level measurements.

How fast are oceans rising?

Satellite observations spanning the past 30 years present a clear picture: global average sea levels have risen by a shocking 4 inches (9.4 centimeters) since 1993.

To make matters worse, the rate of this rise is accelerating. In 1993, sea levels increased by approximately 0.07 inches (0.18 centimeters) per year. Now, the annual increase is more than double, at 0.17 inches (0.42 centimeters) per year.

“Current rates of acceleration mean that we are on track to add another 20 centimeters of global mean sea level by 2050,” said Nadya Vinogradova Shiffer, the director for NASA’s sea level change team. That would mean doubling the amount of sea level rise in the next 30 years compared to the last 100 years.

Sea levels: A thermometer for Earth

Sea level rise isn’t random. It’s a direct response to our warming planet and acts almost like a giant thermometer. They tell us exactly how much extra heat is trapped in the Earth’s climate system by greenhouse gases. There are two main ways climate change drives this rise:

Melting ice

As glaciers and ice sheets melt due to rising temperatures, the water makes its way into the ocean, adding to the global volume. Think about ice cubes melting in your glass – the water level rises as the ice disappears.

Expanding water 

Warmer water takes up more space than cooler water, a phenomenon known as thermal expansion. This is similar to how liquids in a thermometer expand when it’s hot.

2023: A year of global sea level rise

A large part of the recent spike in sea level observed in 2023 is related to the switch between two naturally occurring climate patterns, La Niña and El Niño.

During La Niña years, like 2021-2022, rainfall patterns shift, leading to more rain over land and temporarily suppressing sea level rise. However, a strong El Niño event in 2023 did the opposite–dumping much of that land-based rainfall back into the ocean, raising levels.

“In El Niño years, a lot of the rain that normally falls on land ends up in the ocean, which raises sea levels temporarily,” explained Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory.

Role of climate change

Importantly, while climate patterns play a role in year-to-year variation in sea level, the long-term trend is entirely unmistakable: Sea levels are rising because of human-caused climate change.

“Long-term datasets like this 30-year satellite record allow us to differentiate between short-term effects on sea level, like El Niño, and trends that let us know where sea level is heading,” said Ben Hamlington, who leads NASA’s sea level change team.

Study significance

Rising sea levels directly threaten coastal communities around the globe, increasing the risk of flooding, erosion, and saltwater intrusion into freshwater sources.

As sea levels rise, even moderate storms become capable of causing significant damage and displacement.

Unfortunately, many of the most populous cities and essential infrastructure are located near the coast, making them particularly vulnerable. While the news about sea level rise is sobering, it’s critical to recognize that the future is yet to be written.

The importance of being alert

We are moving through times of change. Long-term data, international teamwork, and scientific breakthroughs are crucial. They help us tell short-lived trends from lasting shifts, guiding us towards insight and action.

In a time when sea levels are rising, the urgency is unmistakable. Our oceans call for our focus, respect, and proactive measures. This call encourages us to discover more about the deep, life-giving oceans that cover our world.

Science and curiosity drive us forward. We’re learning and adjusting in a constantly evolving environment. Water, life, and the quest for knowledge connect us all, reminding us of the continuous cycle that shapes our existence.

Read more about sea level and climate change here.

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