A recently published study has analyzed half a century of data and observations on the state of the polar ice caps, identifying the melting of their glaciers as the main cause of the loss of ice in Greenland and Antarctica and of the rise in sea levels of over 3 centimeters on a global scale.
Since 1970, Greenland and Antarctica have lost a combined 11,3 trillion tons of ice, causing global sea levels to rise by more than 3 centimeters.: this is what emerges from the study “Mass balance of the Greenland and Antarctic ice sheets from the 1970s to 2023”, just published in the scientific journal Scientific data of Nature.
The work is the result of a vast international collaboration led by Northumbria University of Newcastle-upon-Tyne (UK) which involved, among others, theIstituto Nazionale di Geofisica e Vulcanologia (INGV), the European Space Agency (ESA) , NASA and used an extensive set of geophysical and geodetic data to analyze the longest time span ever considered in studies of this kind, obtaining the most complete picture ever of our planet's ice loss.
The team of polar scientists of theIce Sheet Mass Balance Inter-comparison Exercise (IMBIE) combined 42 independent satellite surveys, drawing on 27 satellite missions and going back to 1972 for Greenland and 1979 for Antarctica, using the archive of early Landsat imagery. The results show that The two ice sheets lost 11.309 billion tons of ice between 1979 and 2023, causing global sea levels to rise by 31,4 millimeters.Greenland contributed the largest share of this rise, while Antarctica contributed 13,3 millimeters.
INGV contributed to the study by developing numerical models of the deformation of the Earth's surface in response to the variation of the load exerted by glacial massesIndeed, following the last deglaciation that began about 20.000 years ago, the bedrock on which the Antarctic and Greenland glaciers rest is still slowly rising, and it is important to take these movements into account when analyzing satellite data to improve the precision of estimates of current melting rates.
An extremely relevant fact that emerged from the study shows that 84% of the overall ice loss was caused by accelerated glacier melt and increased ice flow into the ocean, while only 16% is due to the surface melting of the polar ice caps, responsible for about a quarter of global sea level rise.
“The data analyzed show that Ice loss has increased dramatically since the 90s: the Greenland, which in the 70s was nearly at equilibrium, has seen its rate of ice loss drop from about 60 billion tons per year lost in the 1980s to 264 billion tons in the first ten years of the 2000s, a decade characterized by repeated episodes of extreme summer melting”, explains Daniel Melini, researcher at INGV and co-author of the study. “At the same time, the rate of loss of theAntartide it is gone from about 48 billion tons per year in the 80s to 202 billion tons in the 2010s, with the entire net loss caused by the melting of its glaciers: ice outflow from West Antarctica, driven by Pine Island and Thwaites glaciers, has actually increased in every decade for which records are available.”.
The last few years (2020–2023) have brought about a temporary slowing of ice lossRecord snowfall in East Antarctica has partially offset the continent's ice loss elsewhere, while a series of milder summers in Greenland has roughly halved surface melt. However, researchers caution that this isn't a reversal in ice loss, but rather short-term fluctuations within a clear and distinct long-term trend.
“Our findings also underline the central role of polar ice caps in future sea level rise. Their response to global warming in fact represents the main source of uncertainty in future sea level projections: the highest estimates for global sea level rise by 2150 increase 2,6-fold when the risk of ice sheet instability is taken into account. A continuous series of data on the behavior of the ice sheets, collected over half a century, is therefore essential to anticipate the risks looming for the hundreds of millions of people living in coastal areas most exposed to flooding.he concludes melini.
Useful links:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Cover: Antarctica (Credit: Professor Andrew Shepherd)