Last week, the world was given two more harsh reminders of what the future holds as residents of Italy’s Aosta valley were told to evacuate fearing that a huge portion of the Mont Blanc glacier, the equivalent size of Milan’s cathedral, might collapse. Then the last intact ice shelf in the Canadian Arctic, the Milne Ice Shelf, collapsed losing a chunk of ice bigger than Manhattan to the Arctic ocean.
In April, a study published in The Cryosphere suggested that atmospheric circulation patterns contributed in a significant way to Greenland’s rapid loss of ice and as such the future melting predictions could be underestimated by half.
Now, according to a new paper published in the journal Nature Communications Earth and Environment, Greenland’s glaciers have shrunk so much that even if global warming were to stop right now, the ice sheet would continue shrinking.
Satellite data from the last 40 years shows that Greenland’s glaciers have passed a tipping point of sorts, where the snowfall that replenishes the ice sheet each year cannot keep up with the ice that is flowing into the ocean from glaciers.
“We’ve been looking at these remote sensing observations to study how ice discharge and accumulation have varied,” said Michalea King, a researcher at Ohio State University’s Byrd Polar and Climate Research Center and a lead author of the study. “What we’ve found is that the ice that’s discharging into the ocean is far surpassing the snow that’s accumulating on the surface of the ice sheet.”
The researchers analyzed satellite data from more than 200 large glaciers that are draining into the ocean around Greenland and measured how much ice breaks off or melts from the glaciers and flows into the ocean. They then contrasted that with the amount of snowfall each year, which is the way these glaciers get replenished.
They discovered that during the 1980s and 90s, the size of the ice sheet was maintained by a combination of snowfall accumulation and ice melting or calving from glaciers, retaining an equilibrium of sorts. Throughout this two decade period, the researchers found that the ice sheets lost on average about 450 billion tons of ice each year from flowing outlet glaciers, which was replaced with snowfall.
“We are measuring the pulse of the ice sheet — how much ice glaciers drain at the edges of the ice sheet — which increases in the summer,” King said in the researchers’ statement. “And what we see is that it was relatively steady until a big increase in ice discharging to the ocean during a short five- to six-year period.”
About 20 years however, ice melt started increasing, while snowfall remained the same; a pattern that has persisted throughout the last 10 years. Consequently, even if climate change to halted, suddenly, enough damage has been done that the glaciers would continue to disappear into the oceans and there would not be enough snowfall by far to rebuild them during the winter. Glacier retreat has knocked the dynamics of the whole ice sheet into a constant state of loss.
Obviously this is catastrophic, not only for the wildlife in the region – which is already suffering – but also because of the resulting rise of sea level, gradual though it may be, the effects will be noticeable.
The Greenland ice sheet is about the same size as the state of Alaska and 10,000 feet thick in places. It contains enough ice to raise sea levels by 23 feet (7 meters). In the 20th century, Greenland has lost around 9,000 billion tons of ice in total, accounting for 25 millimeters of sea-level rise. (It takes approximately 360 billion tons of ice to produce one millimeter of global sea-level rise.)
In 2012, category two Hurricane Sandy clipped New York City, causing $70 billion in damage, flooding subway tunnel and the Brooklyn-Battery tunnel – and that was a 14 foot storm surge.
Study co-author Ian Howat, professor of earth sciences and distinguished university scholar at Ohio State said, “Even if the climate were to stay the same or even get a little colder, the ice sheet would still be losing mass.”
The paper was coincidentally released on the same day that the US National Oceanic and Atmospheric Administration reported that July 2020 was the second-warmest July on record and that Arctic ice is currently at a record low for summer – the lowest in 42 years of record-keeping.