One of the big questions about global warming is when the Arctic will be ice-free each summer, scientists refer to this as a Blue Ocean Event (BOE).
As Arctic sea ice gets thinner, a blue ocean event looks more imminent every year. A BOE would allow the heat of the sun to fully penetrate the open waters of the Arctic.
Scientists define a blue ocean event as a complete absence of Arctic sea ice, a common threshold is less than an area of 1 million sq. km of sea ice.
In 1988, sea ice that was at least 4 years old accounted for 26% of all Arctic sea ice. By 2013, ice of at least 4 years old was only 7% of Arctic sea ice. It is thought that Arctic ice melt beyond a certain point will not regenerate. If all the sea ice melts, there will be nothing to prevent water temperatures from rising above freezing.
Melting ice reduces albedo, the solar reflectivity of Earth’s surface, and as a result, the rate of warming accelerates in the Arctic. The amount of energy absorbed by melting ice is the same amount of energy it takes to heat an equivalent mass of water from 0°C to 80°C.