A groundbreaking study led by Dr. Kevin Trenberth reveals that the world’s oceans are heating up at an alarming rate in two distinctive bands near 40 degrees latitude in both the southern and northern hemispheres. These regions are experiencing rapid ocean warming. This is especially true around New Zealand and Tasmania. The North Atlantic and North Pacific are also affected.
Dr. Trenberth, a climate scientist from the University of Auckland and the National Center of Atmospheric Research (NCAR), explains that these warming patterns are highly unusual. They stand out in climate data.
- Southern Hemisphere: The area between 40 to 45 degrees south is warming at the fastest pace globally. The strongest effects are seen around New Zealand, Tasmania, and the Atlantic waters east of Argentina.
- Northern Hemisphere: The second warming band is around 40 degrees north. It affects waters to the east of the United States in the North Atlantic. It also impacts waters to the east of Japan in the North Pacific.
“This is very striking,” says Trenberth. “It’s unusual to discover such a distinctive pattern jumping out from climate data.”
WHY OCEAN HEATING MATTERS
Ocean warming is not just a matter of rising temperatures. It has far-reaching consequences for the planet:
- Marine ecosystems: The increase in temperature can upset marine life, affecting biodiversity and fish stocks.
- Atmospheric water vapour: Warmer oceans lead to more evaporation, which raises the amount of water vapour in the atmosphere. This, in turn, enhances the greenhouse effect, further driving climate change.
- Extreme weather: Increased ocean heat contributes to the intensification of storms, rainfalls, and other extreme weather events.
ROLE OF OCEAN CURRENTS AND THE JET STREAM
The heat bands have developed alongside shifts in the jet stream, which has moved poleward since 2005. The jet stream is a powerful band of winds above the Earth’s surface. It plays a crucial role in determining weather patterns and ocean currents.
These poleward shifts, along with changes in ocean currents, have contributed to the rapid warming of the oceans. This warming is notable in these two key zones.
The scientists processed an unprecedented volume of data. They used atmospheric and ocean measurements. They analyzed ocean heat content from 2000 to 2023. Their findings compare these changes with a baseline period from 2000 to 2004, revealing the extent of ocean warming.
ADDITIONAL FINDINGS: TROPICS AND SUBTROPICS
The study also found significant warming in the region between 10 degrees north and 20 degrees south. These areas are primarily located in the tropics. Yet, this warming was less consistent due to the influence of the El Niño-Southern Oscillation. It is a natural climate pattern that brings temporary changes in ocean temperatures.
Interestingly, the study found no significant warming in the subtropical regions near 20 degrees latitude in both hemispheres. This absence of warming in these areas is unusual and requires further investigation.
NATURAL VARIABILITY AND THE CLIMATE DEBATE
Dr. Trenberth, who has long been vocal about the impacts of greenhouse gases, emphasized the role of human-driven climate change. He highlighted its influence on ocean warming. “The climate is changing because of the build-up of greenhouse gases. Most of the extra heat ends up in the ocean,” he said, despite what some politicians think.
The study highlights clear trends in ocean warming. However, natural variability is also at play. This means that not all changes can be attributed directly to human activities.
COLLABORATIVE EFFORT AND FUTURE DIRECTIONS
The research, published in the Journal of Climate, was co-authored by Lijing Cheng and Yuying Pan of the Chinese Academy of Sciences, John Fasullo of NCAR, and Michael Mayer of the University of Vienna and the European Centre for Medium-Range Weather Forecasts.
Moving forward, researchers are keen to further explore the implications of these heat bands for marine life, climate systems, and extreme weather events. Understanding how ocean heating impacts global weather patterns will be crucial in predicting and mitigating future climate risks.
