Torrential rains, abnormal and violent hailstorms, variations in ocean temperature and tsunami waves caused by rising sea levels: all due to a devastating change in climatic conditions which determines, as if that were not enough, the detachment of a Rhode Island-sized portion of the Antarctic ice shelf.
These are the premises with which "The day after tomorrow" opens, a 2004 box office box office hit and "cult" film of the catastrophic genre which, however, as expected, has aroused more than a few controversies in the world of research in due to the numerous and sometimes gross scientific inaccuracies on which it is based.
Cinematography and fiction aside, however, the theme of climate change and its present and future consequences has been on the agenda for several years, not only in Italy. One of the latest studies to deal with sea level rise caused by the melting of polar ice was "Mass balance of the Atlantic Ice Sheet from 1992 to 2017", published last year in the journal Nature. Daniele Melini, an INGV researcher who took part in the study together with an international team of colleagues from 44 other countries around the world, answered some of our questions.
Is the hypothesis of a complete (or almost complete) melting of the Antarctic ice caps plausible or are we once again in the field of fiction?
Surely a complete melting of the Antarctic ice caps in the immediate future is unlikely. The dynamics of Antarctic glaciers is very complex: for example, a study published last year in the journal "Science" demonstrated that the melting of the ice cap in Amundsen Bay caused an uplift of the earth's crust on which the glacier rests, with the result of moving the continental glaciers away from sea level, favoring their stability. However, if we imagine a scenario of complete melting of the Antarctic ice caps, it is estimated that this would lead to a rise in mean sea level of 58 meters.
What is the most important news to emerge from the research published in Nature?
Our research has yielded the most accurate picture we have today of the health of Antarctic glaciers. The data showed that, in the 25 years between 1992 and 2017, a total of 2.700 trillion tons of ice were lost from Antarctica, corresponding to an average sea level rise of about 8 mm. In addition, the data indicate a significant acceleration in the melt rate, which went from about 49 billion tons per year lost between 1992 and 1997 to 219 billion tons melted between 2012 and 2017.
As we have seen, the study offers an estimate of the real rate of melting of the Antarctic ice over the last quarter of a century: how did this result come about and what was the contribution offered by INGV to the international research team?
The team behind this study combined satellite observations and geophysical models of Antarctic ice dynamics to obtain the most accurate estimate available today of the rate of ice melt in that region. As far as INGV is concerned, together with Giorgio Spada of the University of Urbino, we participated by elaborating the models of the uplift of the earth's crust on which the glaciers rest in response to their melting. These movements, in fact, contribute to the measured deformations and must be removed to isolate the data relating only to the melting of the ice.
Considering the acceleration of the melt rate indicated by the collected data, is it possible to make any "predictions" for the future?
The increase of greenhouse gases in the atmosphere, such as carbon dioxide and methane, has long been a source of concern for climate trends in this century. This increase is matched by climate scenarios which see a global rise in temperature, an increase in the melting of the polar ice caps and a consequent rise in sea level. The scenarios examined in the latest report published by the Intergovernmental Panel on Climate Change (IPCC) indicate that in 2100 average global temperatures will be 1 to 4 major degrees Celsius higher than today, resulting in sea levels rising between 40 and 60 cm. Considering that around 40% of the world's population lives in coastal areas, developing multidisciplinary research on climate change and sea level variations is of fundamental importance for developing precise scenarios on the future evolution of the climate and the consequent impacts on human societies.
Image - Fracture in Pine Island Glacier due to calving of iceberg B-46, West Antarctica, November 7, 2018
Credits: Kate Ramsayer/NASA