New evidence collected by Arctic explorer Pen Hadow and his team suggests that the Arctic Ocean will be an open body of water by 2020. The results of Hadow’s study, which saw him trek 430 kilometres to the North Pole and take more than 1,500 measurements of the sea ice, were released on Wednesday.

The findings show that most of the ice floes in the northern part of the Beaufort Sea are only around 1,8 metres thick, meaning that it is first-year ice rather than a “multi-year” sheet that has built up over time. The University of Cambridge physics group that analysed the data stated: “”The area is now more likely to become open water each summer, bringing forward the potential date when the summer sea ice will be completely gone.”

The trend is seen by the World Wildlife Fund as “irreversible”, because water absorbs more of the sun’s heat than ice. The feedback loop created by this process speeds up global warming, and is expected by the Cambridge study group to result in an ice-free Arctic Ocean in the northern hemisphere summer of 2020. Weather patterns are also expected to be severely disrupted, as ocean currents change and more greenhouse gases are released into the atmosphere.

But while Hadow’s first-hand samples are taken by many scientists to be more reliable than the satellite and submarine measurements of other studies, the scientific world has come nowhere close to achieving consensus on the issue. As the New York Times reported last week, the latest measurements out of the US’s National Snow and Ice Data Center record a “substantial expansion” of the thickness of second-year ice in the Arctic, which is being interpreted as a reprieve in summer meltdowns.

Read more: Associated Press, Daily Telegraph, New York Times