The Ocean Is Losing Its Ability to Store Heat as the Planet Warms Up

A New Era of Ocean Warming

The ocean has long acted as Earth’s giant thermal reservoir, soaking up the vast majority of the excess heat generated by greenhouse gas emissions. However, recent findings suggest that this vital cooling mechanism is rapidly deteriorating, setting the stage for prolonged marine heatwaves and escalating stress on marine ecosystems.

Tracking Four Decades of Change

Hajoon Song and his team at Yonsei University in Seoul have been tracking sea surface temperatures (SSTs) using four decades of satellite data. Their analysis has revealed a striking trend: the ocean’s capacity to draw down heat appears to be fundamentally shifting. Historically, about 90% of the planet’s excess heat was absorbed into the ocean’s depths. Now, this process is faltering, with SST anomalies—those brief periods of unusually high temperatures—persisting much longer than before.

“We were surprised not only by this increase in SST persistence, but by the magnitude and global reach of the trend,”
— Hajoon Song

The Prolonged Heat Signature

The persistence of these temperature anomalies means that the ocean is holding on to heat for extended periods. In the eastern North Pacific, for instance, researchers have documented an increase of about 2.5 days per decade in the duration of heat anomalies—a staggering 50% rise over the past 42 years. This “memory” of heat means that once a marine heatwave sets in, it lingers far longer than it used to.

Ripple Effects on Marine Ecosystems

This prolonged retention of heat spells trouble for marine life. Extended heatwaves can lead to more frequent coral bleaching events, disrupt fisheries, and alter ocean circulation patterns. The delicate balance that once moderated global warming by transferring surface heat to the deep ocean is now under threat, potentially accelerating climate change as the surface retains more heat.

Experts warn that as the ocean’s ability to dissipate heat diminishes, the consequences could be far-reaching. “If the heat memory of the ocean is increasing, marine heatwaves will get longer—and that’s going to have major impacts on biology,” notes Alex Sen Gupta at the University of New South Wales in Sydney.

A Shifting Climate System

The changing dynamics of ocean heat absorption are part of a broader shift in our climate system. Some evidence suggests that even the jet streams—those fast-moving bands of wind that circle the globe—are beginning to shift poleward in response to climate change. Such shifts could trigger dramatic changes in weather patterns, affecting regions from the western United States to the Mediterranean.

Adding to the complexity, the eastern Pacific Ocean is showing unexpected signs of cooling. This “cold tongue” phenomenon might reduce the warming effect of greenhouse gases by as much as 30%, but it could also pave the way for severe drought conditions, including the risk of megadrought in parts of the United States.

Stay informed on these critical developments and more at The Horizons Times, where we bring you the latest insights into our rapidly changing world.