8,000 Years ago, The Northwest Passage was Ice Free

In the summers of 8,000 years ago, when the planet's temperature was about two degrees higher than it is currently, The Northwest Passage was ice free. This discovery is the result of an analysis of ice cores extracted in Greenland, through which it was possible to estimate the extent of Arctic ice cover over the past 10 thousand years. The research, published in Scientific Reports, was conducted by scientists at the Ca’ Foscari University of Venice, the National Council of Research and the Niels Bohr Institute in Copenhagen.

This comes as the first reliable reconstruction of the history of Arctic sea ice, observed from satellites from 1970 onwards. Thanks to the intuition of scientists, bromine traces found in Greenland ice indicate the amount of marine ice formed in winter hundreds of kilometers away from the drilling site.

"In the spring, a chemical reaction triggers the release of large amounts of bromine, that are naturally present in sea ice, into the atmosphere - explains Andrea Spolaor, glaciologist at the Department of Environmental Sciences, Informatics and Statistics at Ca’ Foscari. The wind carries it and it settles with the snow over vast kilometers of Greenland's icy crust. In our laboratories in Venice, we are able to measure the amount of bromine stored in the layers of ice for thousands of years and consequently consider the amount of sea ice by season."

The discovery opens the door to both analysis that can reconstruct 120 thousand years of history of Arctic ice cover, and also improvement of future climate projections, calculated, until now, without precise data regarding sea ice, the extent of which it affects the reflection of solar radiation, ocean currents, habitats, but also trade routes between Europe and North America.

“Global warming could lead to climate conditions that took place on the planet 8-10 thousand years ago, with an Arctic Ocean warmer by 2-3 degrees in the summer and thus with no ice. It remains to be seen when we will reach these conditions, today triggered by greenhouse gases - comments Carlo Barbante, co-writer of the research, director of the Institute for the dynamics of environmental processes of the National Research Council (CNR-IDPA) and professor at Ca’ Foscari. This newly discovered method of reconstructing the history of sea ice will help us to better understand its future relationship with the climate, with relevant implications for the environment and economy.”