Cabaña Verónica on the Picos the Europa massif in Northern Spain, once home to one of the paleoglaciers reconstructed by the study. Credit: Worldwide Picture Library / Alamy Stock Photo
An international research group has used 3D simulations of ancient glaciers to reconstruct, for the first time, precipitations over Europe during the Younger Dryas — a period of rapid climate cooling between 12,900 and 11,700 years ago. Because the resulting climate pattern looks similar to one that now happens over Northern Europe, the study can help improve existing climate models.
The team first plumbed the scientific literature to identify the sites of 120 glaciers that, during the Younger Dryas, spread over an area from Norway to Morocco, as well as to the Balkans and Turkey to the East. These glaciers have left geological traces on the mountains that once hosted them. Data about these traces was fed to a software that used them to reconstruct 3D models of the ice mass and surface. In particular, the researchers wanted to calculate each glacier’s equilibrium line altitude, the point where the amount of snowfall during a year equals the amount of snow or ice that melts over the same period. The modelled glaciers were then validated by comparing them with existing glaciers in Europe.
Because equilibrium lines depend on temperature and precipitations, the researchers could use them to reconstruct the atmospheric conditions at that time, in particular the movement of polar jet streams, powerful winds that control seasonal weather patterns.
The result, published in Science Advances1, is the clearest picture to date of atmospheric circulation at the end of the last glaciation, that began 115,000 years ago and ended with the Younger Dryas. Previous studies had used other methods to obtain information about air and sea-surface temperatures during the same period. “But those studies do not tell us much about atmospheric precipitations, or about where the humidity-bearing air masses were coming from,” says Adriano Ribolini, associate professor at the Università di Pisa, a co-author of the study who defined the physical and mechanical parameters used to automatically reconstruct the shape of paleoglaciers.
Reconstructed winds and precipitations for the Younger Dryas closely resemble a circulation pattern that is now observed over Scandinavia, known as SCAND by climatologists, although the ancient pattern was shifted south. "The high pressure and the topographical barrier formed by the polar ice cap existing over Scandinavia diverted the polar jet stream from the North Atlantic to the south, thus reaching western Europe and the Mediterranean," explains Ribolini. The study provides data to validate and fine-tune simulations of current climate. In particular, it helps model the effects of shifts in polar jet stream that could be caused by global warming.
