Ocean warming has accelerated dramatically since the 1990s, nearly doubling during 2010–2020 relative to 1990–2000, according to new UNSW Sydney-led research.
The study, published in Nature Communications, also shows some areas of the ocean are doing more of the work in heat uptake or absorption, which has implications for our understanding of sea-level rise and climate impacts.
Increasing concentrations of greenhouse gases in the atmosphere from human activity traps heat within the climate system, warming air, the land surface, the oceans, and melting polar ice. Oceans do by far the most work, absorbing more than 90 percent of the excess human-generated heat accumulated in the Earth’s climate system, moderating atmospheric temperature rises.
While ocean warming helps slow the pace of climate change, it is not without cost, says Scientia Professor Matthew England, co-author of the study from the UNSW Centre for Marine Science and Innovation.
“The world ocean, in 2023, is now the hottest ever recorded, and sea levels are rising because heat causes water to expand and ice to melt,” says Professor England. “Ecosystems are also experiencing unprecedented heat stress, and the frequency and intensity of extreme weather events are changing rapidly, and the costs are enormous.”
“Right now, the ocean is warming at a dramatically accelerating rate, nearly doubling during the 2010s relative to the 1990s,” says Dr. Zhi Li, lead author of the study from the UNSW Centre for Marine Science and Innovation. “What we wanted to do in this study was to figure out exactly where this ocean heat uptake has been occurring.”
Hotspots of Ocean Heat Uptake
For the study, the researchers evaluated all available observations of ocean warming activity spanning modern Argo float data—an international ocean research program that collects information using robotic instruments—to those taken in the 1950s when only sparse measurements were made from ship-borne devices. They then analyzed the heat uptake across water masses and quantified each water mass’s role in ocean heat content change.
They found oceanic warming has been pervasive worldwide, spreading from the surface to the deep-sea regions known as the abyssal layers and spanning each basin from the tropics to the polar regions. However, the distribution of ocean warming by region was far from uniform.
The Southern Ocean saw the largest increase in heat storage over the past two decades, holding almost the same excess anthropogenic heat as the Atlantic, Pacific, and Indian Ocean combined. This includes two large masses of water in the Southern Ocean that combine to fill a depth range of 300–1500 meters.
