The Arctic Ocean could become ice-free in the summer from as early as 2030 as a natural cycle in water temperature adds to man-made global warming, according to a new study.

Computer models currently expect the Arctic Ocean to be ice-free in the summer, more specifically in the month of September, between 2030 and 2050.

But a new study published late last month in the American Geophysical Union's (AGU) journal, Geophysical Research Letters, found that it is most likely to happen on the earlier end of the spectrum.

The acceleration is due to a natural cycle called the Interdecadal Pacific Oscillation (IPO) — long-term ocean surface temperature shifts in the Pacific of about 0.5 degree Celsius and lasting between 15 to 30 years.

Five years ago, the Pacific began to switch from the cold to the warm phase of the IPO.

The authors of the study plotted predictions of when an ice-free Arctic would occur in model experiments where the IPO was shifting in the same direction as the real world. These showed an earlier ice-free Arctic — by seven years on average — than those predictions that were out of step with reality.

"The trajectory is towards becoming ice-free in the summer but there is uncertainty as to when that's going to occur," James Screen from the University of Exeter in the UK and the study's lead author, said in a statement.

"You can hedge your bets," he added. "The shift in the IPO means there's more chance of it being on the earlier end of that window than on the later end."

The study does warn, however, that while IPO is one of the factors that will modulate the rate of Arctic sea-ice loss in coming decades, human-caused climate change remains the main factor.

"The timing of the first ice-free summer will also depend considerably on whether greenhouse gas emissions continue to rise or are curtailed," it states.