The Arctic Ocean could experience an ice-free summer at some time in the next 20 years, according to a newly-published study. The thawing is due to a combination of a natural warming phase, coupled with the effects of human-induced climate change.

Multiple studies have predicted that the Arctic is trending towards an ice-free summer around the middle of the century. This would happen in the month of September. However, natural temperature fluctuations that occur within Earth's oceans, known as the Interdecadal Pacific Oscillation (IPO), make it hard to pin down exactly when it will occur.

Earth's oceans represent an incredibly dynamic environment, with shifts in temperature from day to day and month to month. Large-scale ocean processes, such as the IPO, can cause a relatively dramatic shift. The IPO occurs in the tropical Pacific, and goes through distinct cycles during which it shifts ocean temperature from warm to cold, and then from cold to warm.

Each cycle takes between 10 to 30 years, and sees the temperature shift by approximately 0.5°C (0.9°F). This may not sound like a lot, but it's enough to significantly influence the speed at which sea ice is disappearing.

Roughly five years ago, the IPO shifted phase, and began warming the ocean.

The computer model used in the new study, which is being led by Britain's University of Exeter, was able to take into account the effect that the IPO has on ocean temperature. The team plotted predictions as to when the Arctic Ocean would experience its first iceless summer with the IPO shifting from cold to warm, and then compared the results with simulations that had the IPO shifting in the opposite direction.

According to the results of the new simulations, the great Arctic Ocean thaw will occur some time between the year 2030 and 2050. The researchers discovered that, when the IPO is in a warming phase, as it is now in the real world, the projection of the first ice-free summer is brought forward by roughly seven years when compared to when the IPO is progressing through a cold phase.

Furthermore, the team believe that the first ice-free summer will occur much closer to the year 2030 than previously believed. Human-induced global warming is the leading cause of ice-loss in the Arctic Ocean, and so our willingness to reduce greenhouse gas emissions will be the determining factor in the timing of the thaw.

A paper detailing the findings has been published in the journal Geophysical Research Letters.