"These abnormally warm pools of Pacific Ocean water have a large but poorly understood impact on global weather. Their effect on coral reefs is a key indicator of how these events relate to climate change," Gillespie said.
However, it's often difficult to determine which changes to corals are attributable to abnormal warming or human activity.
The undisturbed Phoenix Islands, of which Nikumaroro is a part, could provide an ideal research field. The problem is that the corals are impossible to reach without expensive deep-diving technology.
"We need to know how resilient coral atolls like Nikumaroro are to El Niño. The underlying structure, created by coral growth and volcanism, goes down thousands of feet, yet we have never been able to get below two hundred feet," Gregory Stone, executive vice president at Conservation International's Betty and Gordon Moore Center for Science and Oceans, was quoted as saying in the TIGHAR announcement.
Equipped with high-definition video, still cameras, mechanical arms and recovery baskets, the subs will search a mile-long underwater area down to a depth of more than 3,000 feet.
On their way down, they will encounter unique species of coral, such as the Gold Coral, which live at a depth of 1,300-1,600 feet and are among the oldest living organisms on the planet, with colonies as old as 5,000 years.
"We will be going where no one has ever gone before. Researchers will not want to damage the ancient corals, but they often grow so big that pieces break off," Gillespie said.
"Examining these broken-off pieces is a bit like dendrochronology of trees -- a record of climatic changes going back thousands of years. How frequently do these climate changes happen? Is this one unusual?," he said.
The 30-day expedition is expected to cost as much as $2 million. TIGHAR must raise $1.2 million by June 30, 2014. The group is now collecting donations and sponsorships through its website.
"The timing is perfect. We have known targets to investigate what may well be aircraft wreckage. And a major El Niño event is reportedly now developing in the region," Gillespie said. "The opportunity is unprecedented and, sadly, not likely to be repeated."