Humans are significantly changing ocean surface temperatures and seasons

Human activity is no longer subtly influencing the ocean’s rhythm. According to the results of a new study, humans are dramatically reshaping how ocean seasons change throughout the year. Scientists have found a clear human imprint on the seasonal cycle of sea surface temperature.

The ocean temperatures in 2023 broke all-time records. This unprecedented heat isn’t just about rising numbers; it’s fundamentally altering the ocean, its seasons and the delicate balance of life upon which we all depend.

What is ocean surface temperature?

Sea surface temperature (SST) refers to the temperature of the ocean’s top layer. It’s a crucial component of understanding our climate because the ocean absorbs about 90% of the excess heat.

SST impacts weather patterns, marine ecosystems, and the ocean’s ability to continue soaking up carbon dioxide from the atmosphere.

Disrupted ocean season rhythm

This research by Woods Hole Oceanographic Institution (WHOI) shows that the seasonal swings in sea surface temperature are amplifying. Summers are getting significantly hotter compared to winters.

This isn’t happening everywhere in the same way. Researchers observed the following patterns:

Northern hemisphere

Critically, the warming impact is most dramatic during summer months, especially in the Northern Hemisphere. Scientists found that shallower summertime “mixed layers” (the top, actively mixed part of the ocean) are trapping more heat.

Southern hemisphere

Shifting wind patterns, themselves caused by warming, are the main culprits behind changing ocean temperatures.

More than ‘just nature’

Skeptics try to downplay the seriousness of climate change by suggesting the warming is ‘just nature.’ This finding offers a powerful counterargument.

“This research rebuts claims that recent temperature changes are natural, whether due to the Sun or due to internal cycles in the climate system. A natural explanation is virtually impossible in terms of what we are looking at here: changes in the seasonal temperatures of the ocean,” stated Dr. Jia-Rui Shi, a researcher at the WHOI.

“This research further rules out the claim that we don’t need to treat climate change seriously because it is natural.”

Consequences of changing ocean temperatures and seasons

“This robust human fingerprint in the seasonal cycle of ocean surface temperature is expected to have wide-ranging impacts on marine ecosystems. This can dramatically influence fisheries and the distribution of nutrients,” said Shi. “Gaining insight into the anthropogenic influence on seasonality is of scientific, economic, and societal importance.”

More extreme summer temperatures will affect crucial food sources for countless species, disrupt migration patterns, and throw marine life cycles out of balance.

This has profound implications for fisheries, which many communities around the world depend upon for their livelihoods.

Additionally, warmer water holds less carbon dioxide. As the ocean gets hotter, its ability to act as a buffer against the full force of climate change may falter, leading to even faster warming of the planet as a whole.

Insights from changing ocean seasons

As Benjamin Santer, a leading climate scientist from the Woods Hole Oceanographic Institute, points out, decisions about tackling climate change must be based on the best possible scientific understanding.

“We now face important decisions, in the United States and globally, on what to do about climate change. Those decisions should be based on our best scientific understanding of the reality and seriousness of human effects on average climate and on the seasons,” noted Santer.

The seasons of the ocean are changing due to our actions, and those changes are accelerating. This research is a stark reminder that climate change is real, it’s here, and it demands our urgent attention.

The study is published in Nature Climate Change.

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