A vast section of the Indian Ocean has become too dangerous for scientific vessels because of armed raiders attacking ships off the coast of Somalia.

It means that the international program for measuring ocean temperature and sea level rise, with robotic buoys, is missing data which would help scientists better understand not only global warming but also Australian weather patterns.

''There is a large hole in the area that we can cover, due to the pirates,'' Ann Thresher, a senior scientist in the CSIRO's Division of Marine and Atmospheric Research, said. ''We normally deploy the devices off cargo ships, but these vessels are now avoiding the area and sailing along coasts to avoid the pirates.''

After aborted attempts to send a chartered sailing vessel into the pirate zone, an operation to deploy the research buoys from a US Navy warship is now under way.

The Royal Australian Navy will join the research operation later this year, with an Anzac frigate deploying a series of CSIRO buoys across the Indian Ocean on its way to a tour of duty in the Persian Gulf.

Pirate attacks have taken place almost every week this year, and last week three accused pirates who had been detained and brought to the US were charged with murder after four people aboard a cruise were killed in February.

Australian researchers play a central part in the international ocean monitoring effort known as Argo, under which thousands of buoys are deployed around the world.

The buoys, which cost about $15,000 each, sink to a depth of one or two kilometres, gathering data about water temperature and salinity. They surface every 10 days and broadcast their findings to a satellite, providing updates on currents and weather, as well as changes in ocean chemistry used to measure climate change.

''The problem for us is that the floats leak, or they could hit the bottom, or they could get picked up by people, so they have to be replenished if we are going to have broad scale coverage of the ocean,'' Dr Thresher said.

The pirate danger area, reaching out about 2000 kilometres from the Somali coast, is a key zone for determining Australian weather, Dr Thresher said.

The Indian Ocean Dipole is a sea temperature oscillation thought to function in a similar way to the El Nino-La Nina oscillation, which was partly responsible for the wild weather that hit the Queensland coast earlier this year.