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The challenge

Projected ocean changes

The temperature of the waters around Australia is projected to warm by 1 to 2 °C by the 2030s and 2 to 3 °C by the 2070s, with the greatest warming off south-east Australia in the Tasman Sea.

Changes in ocean conditions and processes affect life in the ocean and on land as these changes feedback into the climate system.

The projected warming is a consequence of a strengthening of the East Australian Current and increased southward flow as far south as Tasmania.

The projected Tasman Sea warming is also driven by a southward migration of the high westerly wind belt south of Australia in the future. The westerly wind belt in the Southern Hemisphere has already shifted southward over the last several decades.

There is no obvious strengthening of the Leeuwin Current on the west coast of Australia, although there is a stronger westward flow along the southern coast through the Great Australian Bight. This has implications for the distribution of marine species and links between different regional marine populations.

Our response

Understanding impacts on marine species and ecosystems

Our scientists are investigating a range of impacts of our changing climate on marine life.

Changing ranges

The disruption of marine ecosystems in the Australian region due to global warming is likely to be greatest in our temperate waters. The east-west orientation of the temperate Australian coastline means there are few opportunities for species to move south along the coastal perimeter as water temperatures increase.

In general, bottom and mid-water species are extending their range southward as the warmer waters of the East Australian Current are pushed further south with potential impacts on the local ecology.

Native and introduced species are extending their range to the east coast of Tasmania.

The long-spined sea urchin, a species formerly endemic to New South Wales (NSW), is establishing communities on the east coast of Tasmania, upsetting the balance between kelp species, abalone, rock lobsters and the native urchin.

The European shore crab, a pest species thought to have been introduced to Tasmania in the 1990s, now inhabits the entire eastern coast.

Blooms of planktonic algae off Tasmania in 1998–2004 have been more extensive than previous blooms, but comparable with blooms observed off NSW in the late 1990s.

Sub-tropical marine species are tracking southward across Bass Strait, travelling with the warm streams of the East Australian Current.

Mixing: changes in the marine food chain

Most Australian waters are nutrient poor and reliant on processes such as upwelling to introduce nutrients to the food chain, especially in the tropics and sub-tropics.

In the Australian region, the dominant mechanism of delivering nutrients to the upper ocean is called mixing and occurs in winter due to cooling of the surface water.

The projected surface ocean warming would result in a more stable ocean, with less mixing and therefore a reduced supply of nutrients to the upper ocean, resulting in declining primary (phytoplankton) and secondary (zooplankton) productivity.

These plankton form the basis of the marine food chain. Their decline will significantly affect all marine species.

Ocean acidification

As ocean acidity increases there is a decrease in concentrations of calcium carbonate, the main component of coral reefs and the shells of many marine animals.

This decrease is expected to affect marine species in polar and sub-Antarctic marine ecosystems, in particular marine organisms with external skeletons and shells built from calcium carbonate.

Marine life and our changing climate case study

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