evidence: They are drilling a hole in the sea-ice that naturally forms in winter, and pumping around 1,000 litres of seawater per minute across the surface. [...] The Arctic Ocean is likely to be effectively free of sea-ice by the end of summer at least once by 2050, and possibly even sooner. As the graph below shows, it's already experienced steep declines since the 1980s. [...] "We have to reduce emissions, but even if we do them as quickly as possible, the Arctic is still going to melt."