Why the Ocean off Australia’s East Coast Is Warming Faster
A clear, science-based explainer for a general audience
More than 90% of the extra heat trapped by greenhouse gases ends up in the ocean, but this heat does not spread evenly. It concentrates in certain regions depending on winds, currents, and large-scale atmospheric circulation. Recent research shows that the South Pacific, especially between about 20°S and 40°S, has warmed faster than many other parts of the global ocean. Australia’s east coast sits right inside this band.
Australia’s east coast lies between roughly 10°S and 38°S, bordering the Tasman Sea and South Pacific rather than the Southern Ocean, which generally begins much farther south around 50–60°S. Even though the Southern Ocean is crucial for global heat uptake, the waters off eastern Australia are mainly shaped by subtropical Pacific processes, not direct Antarctic influence.
The Hadley circulation
The Hadley circulation is a planet-scale system that moves heat from the equator toward the subtropics. Strong sunlight heats the equator, causing warm air to rise. This air flows poleward high in the atmosphere, then sinks around 20–35° latitude in each hemisphere. Surface winds return air toward the equator as the trade winds. Where air sinks, skies are clearer, rainfall is suppressed, and the surface warms more efficiently.
Climate change is pushing the Hadley circulation poleward, especially in the Southern Hemisphere. The tropics are warming faster than higher latitudes, the upper atmosphere is cooling, and the Southern Hemisphere westerly winds are strengthening and shifting south. For eastern Australia, this means more persistent high-pressure systems, fewer clouds, more sunlight reaching the ocean, and less cooling from evaporation—all of which accelerates surface ocean warming.
The Walker circulation and ENSO
The Walker circulation is an east–west circulation along the equator across the Pacific Ocean. Warm water piles up in the western Pacific near Indonesia and northern Australia, where warm air rises to produce clouds and rain. Air flows eastward aloft and sinks over the eastern Pacific, with trade winds completing the loop.
El Niño shifts warm water eastward and often dries eastern Australia, while La Niña strengthens trade winds and cools the central Pacific. However, La Niña also pushes heat into the subtropics, meaning waters off eastern Australia can continue warming even during La Niña years.
Why the east coast is a marine warming hotspot
Eastern Australia lies in a subtropical warming band between 20–40°S, where the expanding Hadley circulation, ENSO heat redistribution, and the East Australian Current all concentrate warmth along the coast. Meanwhile, the Southern Ocean—though it absorbs more heat than any other ocean—influences wind patterns and circulation that set the background conditions for this subtropical warming.
The ocean off Australia’s east coast is warming faster because it sits at the intersection of expanding atmospheric circulation, shifting Pacific heat patterns, and strong ocean currents that funnel heat toward the coast. This is a structural, long-term change—not a short-term fluctuation.
