Global sea levels rose at an alarming rate in 2024 surpassing previous predictions due to an unusual spike in ocean warming and melting land-based ice. According to a NASA led analysis the rate of rise last year was 0.23 inches (0.59 cm) per year, significantly higher than the expected 0.17 inches (0.43 cm) per year.
Scientists attribute this sharp increase primarily to the thermal expansion of seawater process where ocean water expands as it warms. In a surprising shift, two-thirds of last year’s sea level rise came from thermal expansion reversing the usual trend where melting glaciers and ice sheets were the dominant contributors.
Josh Willis sea level researcher at NASA Jet Propulsion Laboratory in Southern California say “The rise we saw in 2024 was higher than we expected, 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.”
Record-Breaking Heat and Its Impact on the Oceans
Last year was officially the warmest on record and Earth’s oceans responded accordingly. Warmer oceans are not only expanding but also reaching their highest levels in three decades. Nadya Vinogradova Shiffer head of physical oceanography programs at NASA, emphasized the significance of this shift.
She say “With 2024 as the warmest year on record, Earth’s expanding oceans are following suit reaching their highest levels in three decades”.
Since satellite records of ocean height began in 1993, the annual rate of sea level rise has more than doubled. In total, global sea levels have risen by approximately 4 inches (10 cm) over the past 30 years, with 2024 marking one of the sharpest increases in recent history.
Understanding Ocean Heat and Vertical Mixing
Ocean warming does not occur evenly across the planet. Normally, seawater forms layers based on temperature and density, with warmer, lighter water staying on top while cooler, denser water remains below. This layering slows down the process of heat transfer into the deep ocean.
However, strong winds and powerful ocean currents such as those in the Southern Ocean can disrupt this balance, causing vertical mixing that pushes surface heat deeper into the ocean. Additionally, the massive movement of warm water during El Niño events plays a role in redistributing heat, further influencing ocean expansion and sea level rise.
NASA has been tracking sea level changes using satellite observations for over three decades, starting with the TOPEX/Poseidon mission in 1992. The current satellite, Sentinel-6 Michael Freilich, launched in 2020, continues to monitor sea surface height with remarkable precision. Its upcoming twin satellite, Sentinel-6B, will ensure that global sea level measurements remain accurate into the next decade.
What This Means for the Future
The acceleration of sea level rise has far-reaching consequences for coastal communities, ecosystems, and global weather patterns. Scientists warn that if ocean temperatures continue to increase at this rate, low-lying regions around the world will face more frequent flooding, stronger storm surges, and irreversible habitat loss.
The findings reinforce the urgent need for global climate action to curb greenhouse gas emissions and slow the warming of the planet. Without immediate intervention, rising sea levels could reshape coastlines and threaten millions of lives in the decades to come.