A new study published in Advances in Atmospheric Sciences has found that ocean warming in 2024 has led to new record high temperatures. The ocean is the hottest it has ever been, not only at the surface level but also deep in the upper 2000 meters. The findings of the study are used to update several Copernicus Marine Service Ocean Monitoring Indicators concerning ocean heat.
“The broken records in the ocean have become a broken record,” said Prof. Lijing Cheng with the Institute of Atmospheric Physics at the Chinese Academy of Sciences. He led a team of 54 scientists from 7 countries for this study. He recently discussed how a hotter ocean affects our lives on land and what this means for our future.
The ocean is a critical part of the Earth’s climate. Most of the excess heat (nearly 90%) from global warming is stored in the ocean, and the ocean covers 70% of the Earth’s surface. Because of this, the ocean drives our weather patterns by transferring heat and moisture into the atmosphere. The ocean also controls how fast climate change happens. “To know what is happening to the climate, the answer is to be found in the ocean,” said Prof. John Abraham at the University of St. Thomas, coauthor of the study.
Results from three international teams who collaborated on this project were consistent – the ocean is warming, and 2024 was a record. The next image shows one set of results for the upper 2000 m ocean heat content (from the Institute of Atmospheric Physics). Blue and red colors refer, respectively, to whether a particular year was colder or hotter than the 1981-2010 period. This period is used as a basis for scientists to compare against reference conditions. The central message is that the values have been increasing year after year after year.
From 2023 to 2024, the global upper 2000 meters ocean heat content (OHC) increased by 16 zettajoules (1021 Joules), which was approximately 40 times the world’s total electricity generation in 2023. “OHC has increased steadily by approximately 15 to 20 zettajoules over the past five years despite the La Niña and El Niño cycles,” said Prof. Michael Mann from the University of Pennsylvania. The ocean surface temperature is also setting records. The surface refers to where the ocean waters and the atmosphere meet. And the rise in mean sea surface temperature since the late 1950s has been staggering.
The changes are not uniform though and regional variations can be substantial. The Atlantic is warming along with the Mediterranean Sea, and across the mid-latitude Southern Ocean. While parts of the Northern Pacific Ocean have warmed rapidly, other areas (the tropical region, for instance) have not, mostly due to the La Nina/El Nino cycle. The heat has accumulated even near both the North and South Poles.
A warmer ocean affects marine life and results in major damage. “The main way the ocean continuously influences the climate is by increasing water vapor, a powerful greenhouse gas, in the atmosphere to dangerous extremes,” said Dr. Kevin Trenberth, a senior scientist at National Center for Atmospheric Research (USA) and another research team member. “Increased warming leads to higher risks of drought and wildfires, and fuels risks of flooding and storms of all sorts, including hurricanes and typhoons.”
Over the past 12 months, a staggering 138 countries have recorded their hottest temperatures ever. Droughts, heat waves, floods, and wildfires have impacted Africa, Southern Asia, the Philippines, Brazil, Europe, the USA, Chile, and the Great Barrier Reef among many others. Since 1980 for instance, climate disasters have cost the USA nearly 3 trillion dollars.
Ocean heat is the best measurement to monitor climate change. “The ocean is our sentinel for global warming, acting as the biggest sink of surplus heat accumulating in Earth climate system as a result of anthropogenic greenhouse gas emissions,” said Dr. Karina von Schuckmann, Senior advisor for ocean science for policy Mercator Ocean International and leader of the Copernicus Marine Ocean Monitoring Indicators activities, who is a coauthor of the study. If nothing is done to slow climate change, the disruption, unprecedented change, and its costs, loss, and damages will continue to increase.