A staggering 12.5 trillion tons of polar ice has disappeared from Greenland and Antarctica since the 1970s, researchers have found.
The international team of scientists has assembled the longest satellite record in history, revealing the true extent of polar ice loss over the last 50 or so years. This comprehensive record looks at Greenland as early as 1972 and Antarctica as early as 1979 and stretches until 2023. The record also includes data from 42 different satellite surveys and 27 satellite missions. Of the 12.5 trillion tons (11.3 trillion tonnes) of ice loss observed, the majority of the damage comes from Greenland's ice sheets.
"By reaching back to the 1970s, we can now see how the ice sheets have changed across half a century," study lead Inès Otosaka of Northumbria University said in a statement.
The new record, known as the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE), gives us the most complete look at polar ice loss over past decades. This detailed look through the history of ice loss has also revealed over 1.18 inches (3 centimeters) of sea level rise over that period of time.
"Three centimetres of sea level rise may sound small, but that puts another six to nine million people at risk of coastal flooding and erosion. With the ice sheets set to lose much more ice in the decades ahead, global assessments like IMBIE are vital to protecting communities impacted by climate change," co-author Andrew Shephard, Head of the School of Geography and Natural Science at Northumbria University and founder of IMBIE, said in the statement.
The researchers found 84% of the recorded polar ice loss came from glaciers flowing faster over time, whereas only 16% of that loss is from surface-level ice melting.
And, unsurprisingly, the culprit behind this significant, long-term ice loss? Climate change and a warming planet.
"More than four-fifths of the ice lost was discharged into the ocean by faster-flowing glaciers, rather than melted at the surface — which tells us the long-term trend is being driven by the dynamic response of the ice sheets to a warming ocean," Otosaka said.
With this record, not only do we see the overall ice loss over the past decades, but we can see periods of time where ice loss has been more extreme. According to this data, starting in the 1990s, ice began disappearing more intensely. In 1980s Greenland, for instance, ice loss was taking place at about 66 billion tons (60 billion tonnes) per year. Fast forward to the 2010s, and suddenly it was about 291 billion tons (264 billion tonnes) of ice loss per year. A similar shift has been seen in Antarctica, with about 53 billion tons (48 billion tonnes) of ice lost per year in the 1980s and 222 billion tons (202 billion tonnes) lost in the 2010s.
Looking to the future
As polar ice disappears and sea levels continue to rise, concerns over the continuing and worsening repercussions of climate change continue to grow. In fact, recently, the United Nations put out a report that said within just the next few years, we are on track to exceed the 1.5 degree Celsius threshold (above preindustrial conditions) that nearly 200 nations pledged to work and stay under during the Paris Agreement in 2015.
Furthermore, while this ice loss record shows the stark reality of the situation in clear detail, it also demonstrates the power of space-based observations and how satellite data can help us to continue to monitor and better understand our changing planet in an effort to combat climate change. With climate change primarily driven by human activities like industrial manufacturing and agriculture, information like this can help scientists strengthen the case for making policy changes to alleviate the human impact on our warming planet.
"The added length of the record, the larger pool of participating teams and our improved ability to assess uncertainties make this the most robust assessment of ice sheet mass balance produced so far. Satellites give us continent-wide, year-on-year evidence of what is happening now, and that is exactly what we need to test models and narrow the uncertainties in projections of future sea level rise," co-study lead Tyler Sutterly of the University of Washington said in the statement.
"These findings show the fundamental importance of using satellites to monitor the ice sheets and to evaluate the models used to predict the effects of climate change. Sustaining missions such as CryoSat-2 and the Sentinels, and maintaining the long-term ice-sheet climate data record, is critical for the decades ahead," ESA scientist Diego Fernández added in the same statement.
This work, supported by NASA and the European Space Agency, is described in a new study published in the journal Scientific Data.
