Australian researchers have embarked on an expedition to explore previously undocumented deep-sea coral reefs off the country's north coast.

Australian Institute of Marine Science (AIMS) researchers departed Darwin on Friday bound for the Ashmore Reef Marine Park for a three-week expedition.

The "unknown and undocumented" mesophotic coral ecosystem will be explored with researchers hopeful their findings will help protect reefs around the world.

Karen Miller, the chief scientist on the voyage from the AIMS, said that equipment on board the Schmidt Ocean Institute's RV Falkor made studying the reef possible, according to a report by the Australian Broadcasting Corporation (ABC) on Sunday.

"It's not quite light and it's not quite dark, so it's like twilight. Because it's got a very different light regime to other areas of the ocean. What we expect to see is quite a different suite of species that are specialized," she said.

"It is very difficult to do this work and you don't get very many opportunities," she said. "We're excited to be able to study that unknown area and to see what species are living there that we don't necessarily know even exist yet. It's that technology that enables us to be able to go down and study these reefs in detail."

The biodiversity samples collected on the voyage will be coordinated by the Western Australia Museum.

Nerida Wilson from the museum said the findings could hold the key to conserving reefs amid global warming.

"If conditions change, with climate, then the kind of environmental conditions that shallow reefs need now are going to be in those deeper areas in the future," she said.

"We'll understand if they are providing a refuge for the shallow water animals, so we will also know to follow what happens to the animals that are currently only known in mesophotic areas.

"It's quite complex to try and figure out what happens in the future, and the more we understand now the easier our job will be then."