The East Australian Current, or EAC, is a significant flow of warm ocean water moving south along Australia’s eastern coastline. Many recognize its name from the animated film Finding Nemo, where it was depicted as a marine highway. The EAC is a dominant feature of the region’s marine environment, influencing everything from local weather to the distribution of sea life. This powerful current is the largest to flow close to the Australian continent.
Formation and Physical Characteristics
The EAC originates in the warm, tropical waters of the Coral Sea. It forms when the westward-flowing South Equatorial Current meets the Australian continent and turns south, creating the western boundary current of the vast South Pacific Gyre. The current’s southward path is guided by prevailing trade winds and the Earth’s rotation, a phenomenon known as the Coriolis effect.
The current transports a large volume of water that is characteristically warm, salty, and low in nutrients. The EAC can be up to 100 kilometers wide and 500 meters deep, with a variable flow that can reach speeds of several knots. As it travels south, the main flow weakens and breaks away from the coast, often forming large, swirling bodies of water known as eddies.
Influence on Marine Ecosystems
The current distributes marine organisms by carrying the larvae of tropical species southward. This extends the habitat range for many fish, corals, and other invertebrates far beyond their typical tropical homes. The warm water it brings south also helps sustain ecosystems like the Great Barrier Reef by keeping coastal waters warmer year-round.
The large, rotating eddies created by the EAC are hotspots for marine life. These eddies trap and concentrate plankton and other nutrients, creating rich feeding grounds in the otherwise nutrient-poor waters of the Tasman Sea. This nutrient concentration supports a complex food web, attracting larger animals such as whales, dolphins, and southern bluefin tuna.
Impact on Regional Climate
The EAC notably affects the climate of Australia’s southeastern region. The large volume of warm water it carries acts as a heat reservoir, which is gradually released into the atmosphere. This process influences air temperatures along the coast.
This heat transfer results in a more moderate climate for coastal communities than expected for their latitude. Winters are generally milder and sea surface temperatures remain warmer throughout the year. This oceanic influence also contributes to local weather patterns, affecting rainfall and storm systems along the eastern seaboard.
A Current Under Pressure
Observations indicate the East Australian Current is changing. The current is strengthening and its warm waters are pushing further south than in past decades. This poleward extension is a consequence of shifts in large-scale climate patterns, which intensify the winds that drive the ocean gyre system.
This southward push is altering marine ecosystems in temperate zones through a phenomenon known as “tropicalisation.” This involves the displacement of cooler water species by those arriving from the north. For example, in the waters around Tasmania, long-spined sea urchins transported by the strengthening EAC are having a major impact. These urchins graze heavily on giant kelp forests, creating barren areas and changing the local marine habitat.