Record heat of 2024 triggered a surge in sea level rise

Oceans never stay still. They shift, churn, breathe – responding to forces seen and unseen. Tides roll in and out, currents snake across the globe, and deep waters keep ancient secrets. Yet, in recent decades, something has changed. Sea levels are rising at an accelerating pace.

Scientists expected this rise. What they didn’t expect was just how fast it would happen. The year 2024 delivered a sharp wake-up call, showing a spike that outpaced predictions.

Coastal cities, fragile ecosystems, even the way storms form – all are being reshaped by the relentless expansion of the sea.

Sea level rise is accelerating

In 2024, global sea levels rose at a rate of 0.23 inches (0.59 centimeters) per year. That may sound small, but when spread across the vastness of Earth’s oceans, it’s staggering.

Scientists had expected a rise of 0.17 inches (0.43 centimeters) per year. Instead, the increase came faster, driven largely by the expansion of warming seawater.

“The rise we saw in 2024 was higher than we expected,” said Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California.

“Every year is a little bit different, but what’s clear is that the ocean continues to rise, and the rate of rise is getting faster and faster.”

Three decades of satellite data confirm the trend: rising waters, increasing speed, and an undeniable pattern. Year by year, the ocean gains height, swallowing more shoreline, shifting ecosystems, and creeping further inland.

Changing forces behind rising seas

For years, the biggest driver of sea level rise was melting ice. Glaciers and ice sheets shed their frozen mass into the ocean, accounting for about two-thirds of the increase. The rest came from thermal expansion – ocean water growing in volume as it absorbs heat.

Then, in 2024, the balance flipped. Ocean warming took the lead. Now, two-thirds of sea level rise comes from thermal expansion alone.

“With 2024 as the warmest year on record, Earth’s expanding oceans are following suit, reaching their highest levels in three decades,” said Nadya Vinogradova Shiffer, head of physical oceanography programs at NASA Headquarters in Washington.

This shift signals a deeper problem. Even if glaciers stopped melting tomorrow, oceans would still rise. The heat already absorbed will keep expanding water for years, if not centuries.

Satellites watching from above

Tracking the rise of the sea requires precision. Satellites provide that view, giving scientists the ability to measure ocean height down to mere centimeters.

Since 1993, satellites have kept a constant eye on Earth’s waters. The data they collect reveals a clear upward trend – sea levels have climbed approximately 4 inches (10 centimeters) since the early 1990s.

The mission began with TOPEX/Poseidon in 1992. Today, Sentinel-6 Michael Freilich carries the torch, delivering data with unparalleled accuracy.

Soon, its twin, Sentinel-6B, will take over, ensuring that these vital observations continue for decades to come.

What these satellites record is more than just numbers. Their measurements help researchers forecast storm surges, predict flooding risks, and refine climate models. Without them, the world would be flying blind into an uncertain future.

How heat moves through the ocean

Oceans don’t heat up evenly. They aren’t like a pot of water on a stove, warming from the bottom up. Instead, heat seeps in through the surface, where it can linger – or sink deep, depending on conditions.

In most places, ocean water settles into layers. Warm, lightweight water stays near the top, while colder, heavier water sinks. This layering slows the spread of heat. But sometimes, nature disrupts the system.

Powerful winds can stir the ocean, dragging warm surface waters downward. Massive currents – like those in the Southern Ocean – tilt the layers, allowing heat to slip into deeper waters.

The result? A slow but steady infusion of warmth, fueling thermal expansion and rising sea levels higher.

El Niño and the heat shuffle

Then there’s El Niño. Every few years, a vast pool of warm water in the western Pacific sloshes eastward, shifting weather patterns across the globe.

When El Niño shifts warm water across the Pacific, ocean heat moves with it. Surface temperatures fluctuate, deep currents realign, and while some regions face rising waters, others see temporary declines.

El Niño doesn’t just affect sea levels in the moment – it adds to long-term warming. More heat in the ocean means more expansion. And more expansion means more water creeping up shorelines, year after year.

What comes next?

The acceleration of sea level rise in 2024 is more than just a statistic. It’s a warning. A reality check. A glimpse of what’s to come.

For coastal cities, the stakes couldn’t be higher. Higher seas mean stronger storm surges, flooded streets, and disappearing shorelines. Communities will need stronger defenses – sea walls, drainage systems, and emergency plans for when the waters come.

Scientists will keep watching, tracking every fraction of an inch. The satellites will keep measuring. But the ocean? It will keep rising.

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