New Zealand in Fastest-Warming Ocean Zone, Study Finds

Recent studies on global warming have discovered two regions in the world's oceans that are warming faster than the rest, and New Zealand is located in one of the most affected regions. The study, conducted by Dr. Kevin Trenberth of the University of Auckland and the National Center for Atmospheric Research (NCAR), contrasted ocean heat trends over 23 years. It found that oceans worldwide are warming at their fastest rates in two bands of latitude—one south between 40 and 45 degrees south, and another close to 40 degrees north. The alterations are reorganizing ocean ecosystems, increasing atmospheric moisture, and strengthening weather patterns.

The strongest warming is at the 40–45°S latitude zone and extends over New Zealand, Tasmania, and regions of the South Atlantic east of Argentina. It is an area where there has been the hotspot for increasing ocean heat content. It is the northern area off 40°N and has areas in the North Atlantic east of America and the North Pacific east of Japan. These areas have demonstrated persistent and severe heat deposition into the upper 2000 meters of the ocean since 2005 according to long-term climatic variability and natural change.

The study was based on a large data set that quantified one-degree strips of the ocean to depths of as much as 2000 meters. It contrasted heat content observations from 2000 to 2023 with the 2000–2004 control period. The analysis determined an astronomical build-up of energy in the oceans, in units of zettajoules. The observations show a patchy distribution of warming oceans with some regions warming at considerably higher rates than others.

One of the key discoveries is that they are connected with shifts in atmospheric jet streams and oceanic currents. The jet streams—powerful, rapid air streams high above the surface of the earth—have moved poleward in each of the two hemispheres, altering patterns of ocean circulation and bringing about the warming in these mid-latitude regions. These changes are believed to be a main driver of redistributing heat in the oceans, rather than allowing it to spread equitably around the globe.

The study also identified significant warming in the 10°N-20°S tropical belt. But temperature trends in this region are controlled by the El Niño-Southern Oscillation (ENSO), a natural climate cycle that produces irregular temperature fluctuation across the Pacific. As a result, although the belt has seen increases in warming, warming trend is less consistent and more variable than over the two mid-latitude belts.

As against the expectations, the researchers recorded an absence of appreciable warming in the subtropics at 20° latitude in both hemispheres. The observation is contrary to the theory that global warming influences oceanic regions simultaneously and illustrates the complexity of ocean-climate processes.

The consequences of this asymmetric ocean warming are deep. Warmer oceans not only disrupt ocean biodiversity and ecosystems but also increase humidity due to increased evaporation. Water vapor is an extremely potent greenhouse gas, so this feedback mechanism could amplify climatically driven changes such as more intense and more frequent storms, more intense rainfall, and coastal flooding.

New Zealand's location in the region of the fastest-warming southern ocean places it at greater risk from climate-induced marine and atmospheric impacts. These may include changes in fish, shifts in weather patterns, and more frequent episodes of extreme weather events. Its location is imperative to identify as a point for future climate resilience and marine management strategies.

The study was spearheaded by scientists from across the globe including Lijing Cheng and Yuying Pan of the Chinese Academy of Sciences, John Fasullo of NCAR, and Michael Mayer of the University of Vienna and European Centre for Medium-Range Weather Forecasts. Peer-reviewed, the paper was released in the Journal of Climate, an American Meteorological Society journal.

The study identifies the importance of high-resolution climate observation and advanced modeling for tracking small but meaningful changes in the Earth's climate system. The study adds to growing evidence the climate crisis is unfolding asymmetrically with some regions being hotspots of speeding up change. For scientists, policy-makers, and affected communities in the relevant places—such as New Zealand—these findings can inform adaptation, conservation, and long-term climate planning decision-making.

The research is a wake-up call to be cautious on regional climate patterns as well as world means. It is sounding an alarm for regional investigation of data so that one would be in a place to comprehend and prepare for regional impacts. Ongoing ocean warming continues to shape future environmental status, and research like this provides vital facts for strategic planning in sectors like fisheries, coastal development, as well as for disaster risk mitigation.

Source/Credits:
Faculty of Science, Environment, Science and Technology, University of Auckland
Research by Dr. Kevin Trenberth, University of Auckland and NCAR
Co-authors: Lijing Cheng, Yuying Pan (Chinese Academy of Sciences); John Fasullo (NCAR); Michael Mayer (University of Vienna, ECMWF)
Published in Journal of Climate