"The East Australian Current sets the whole structure of the Tasman Sea," CSIRO scientist and voyage leader Dr Bernadette Sloyan said.
"It influences our climate, the ecosystem, commercial and recreational fishing, much of what we see on the coast.
"If the current wasn't there, we'd have a very different Tasman Sea."
Dr Sloyan said the current was also a key component of global ocean circulation, moving heat, freshwater and nutrients around the South Pacific.
It moves massive amounts of water – each second transporting more than 25 million cubic metres of water, or 10,000 Olympic swimming pools, southwards.
"The voyage will deploy six large moorings, from the continental slope to the deep ocean off Brisbane," Dr Sloyan said.
"This is where the East Australian Current approaches its maximum strength and its flow is relatively uniform so we can measure the current's average flow and how it varies over time."
The collaboration between CSIRO, the Marine National Facility and the Integrated Marine Observing System (IMOS) will enable the maintenance of multi-year monitoring of the current.
"The East Australian Current shows variations over a range of timescales from seasonal to decadal," IMOS Director Tim Moltmann said.
"Much of what we know about the current has come from irregularly distributed observations collected over many decades.
"What is lacking is a sustained time-series of observations of the East Australian Current across its entire extent and of sufficient duration to understand seasonal, interannnual and decadal signals.
"The IMOS observations will provide significant new insights into the variable nature of the East Australian Current."
Dr Sloyan said the current had important implications for Australia's weather and climate.
"It is the dominant mechanism for the redistribution of tropical Pacific Ocean heat between the ocean and atmosphere in the Australian region," she said.
The waters in the Tasman Sea have warmed by more than 2oC, faster than other parts of the world's oceans.
"Western boundary current regions, such as the EAC system, are highly variable and linked to large-scale ocean changes," Dr Sloyan said.
"Monitoring the EAC therefore, provides information of the large-scale drivers of regional ocean change.
These changes may result in subtropical marine species moving into temperate waters, altering the habitat of many species."
Investigator is a 94 metre purpose-built research vessel, capable of travelling 10,000 nm in a single voyage, carrying up to 40 scientists and support staff, from the equator to the Antarctic ice-edge. The Marine National Facility is a blue-water research capability funded by the Australian Government. Under direction of an independent Steering Committee, it is owned and operated by CSIRO on behalf of the nation.