Has Time Run Out to Stop Greenland's Ice Sheet Melting?

ON 05/18/2021 AT 03:15 AM

A new research paper suggests the melting of Greenland’s ice sheet may have already gone far enough that, even if carbon emissions halted immediately, the globe is in for a minimum 3 to 6 feet (several meter) sea level rise because of it.

Jacobshavn Glacier, Greenland

The Jacobshavn Glacier calving front, in Greenland. Photo: NASA

The new study, conducted by Niklas Boers of the Potsdam Institute for Climate Impact Research, Germany, and Martin Rypdal of the Arctic University of Norway, focused its analysis on Greenland’s Jakobshavn basin, the fastest melting of the five largest ice basins in the country.

The research investigated 140 years of data on the Jakobshavn. Those records include documented temperature records, current-day ice core samples from the ice sheet, and advanced modeling techniques to understand what is happening there. What they discovered was evidence of a new tipping point, caused by a melting feedback loop that begins with the melting on the top of the ice sheet narrowing the ice sheet thickness. Though the effect may seem small, the ice height dropping now brings the top of the sheet to a lower altitude than before, a height where higher average air temperatures exist. Those higher temperatures then accelerate the melting process.

The concept of this cycle is well understood. What is new is the discovery that there is now zero chance for this feedback loop to slow down, under current conditions. As the researchers noted, there could be a smaller ice sheet size that could survive, provided global warming were to slow, but that still leaves the planet with a major mess on its hands just from this one ice sheet alone.

That mess predicts a one-to-two-meter (3.3 to 6.6 feet) sea level rise just from the currently calculated melting of the Jakobshavn basin. Based on current temperatures and the existing concentrations of carbon emissions in the atmosphere to trap solar energy close to the planet, even if carbon emissions were never to increase any more – an impossibility, of course – that sea level rise is locked in.

As the researchers note in their paper, “the western Greenland Ice Sheet has been losing stability in response to rising temperatures.” This stability loss, the paper explains, comes from long-term shifts in the North Atlantic Oscillation (NAO) and East Atlantic Pattern atmospheric movements and temperature changes. The atmospheric shifts have, the authors continued, “led to a weakening and southward shift of the jet stream, and more persistent blocking over Greenland during the summer.” These changes, combined with overall higher temperatures present because of overall anthopogenic (human-caused) global warming trends, show the ice sheets on Greenland are already contributing “solid ice discharge into the North Atlantic and surface melting” at alarming rates.

The surface melting alone, the authors write, “has increased from 42% before 2005 to 68% between 2009 and 2012.”

What these scientists learned after performing more accurate measurements of how the ice sheet feedback loop is operating in practice, suggests there is already an accelerating cycle of more ice mass reduced on the top and flowing into the ocean. The combination of general global heating increases initially caused by carbon emissions concentration increases, plus oceanic and atmospheric shifts, appears to have kicked Greenland’s Ice Sheet destabilization to a point of no return.

As multiple scientific studies have reported, if all the ice in Greenland were to melt – as now seems to be more likely than not – there will be some 7 meters (23 feet) sea level rise. It will engulf billions of people in its wake, putting cities such as Miami, Shanghai, Manila, Jakarta, Singapore, and Kolkata, India, for example, under water forever.

The scientists continue their warnings, explaining that, “Continued melting of the GrIS has been suggested to potentially lead to a collapse of the Atlantic Meridional Overturning Circulation via increased freshwater flux into the North Atlantic, which may, in turn, trigger a cascade of transitions in additional tipping elements such as the Amazon rainforest and the tropical monsoon systems.”

Other researchers have noted that the Gulf Stream ocean current will also begin to slow as the Greenland ice melt changes the temperature mix in the northern Atlantic. That will change weather patterns proceeding all the way across to England and Europe, with likely far lower-than-normal temperatures showing up there in the near future, as the warming currents of the Gulf Stream are no longer present to moderate the climate.

As the melting has accelerated, other scientists have now realized previous climate models had grossly underestimated the impact of melting permafrost underneath ice sheets such as those in Greenland. When that permafrost is exposed, previously trapped stores of carbon in multiple forms, including methane, are now being released into the atmosphere at high rates. What this points to is a soon-to-be far faster carbon emissions concentration increase rate in the atmosphere, which in turn will heat the planet even faster.

What is happening in Greenland is being mirrored in multiple other locations around the world.

The Arctic, which saw unheard-of high temperatures just a little under a year ago, has a high likelihood of being ice-free by mid-summer. When that happens, the oceans at the pole will heat rapidly, likely releasing previous frozen methane hydrate from deep underneath. This is already being measured and tracked by Russian-Scandinavian research teams trolling along the northern Siberian coast. The permafrost along the edge of the Arctic is also being exposed, just as it is in Greenland.

The heat bubble over the Arctic which has resulted is contributing to the destabilization of the jet stream. That destabilization manifested in a huge shift of polar air southwards in February 2021 over the North American continent, making some think perhaps the climate crisis had reversed. The truth was the opposite: the presence of such rapid cooling was directly tied to a superheated Arctic.

The Antarctic ice sheets are also cascading towards their own tipping points. Scientists there have in recent years discovered, via advanced satellite reconnaissance data, that the bottom of those ice sheets are melting faster than previously known. That, plus higher temperatures, and the region’s own increasingly unusual mix of oceanic and stratospheric vortices, will likely release one or more of the polar ice sheets into the ocean. When it floats northward, it will melt rapidly and also contribute to sea level rise.

The last of the major cryospheric contributions which are also contributing to ice mass release is in the Himalayan Mountain ranges, extending across Asia north of India. That ice melt is now proceeding at twice the rate of just twenty years ago. In countries such as Bhutan, which depends on the Himalayas for a continually replenished level of snow and ice on glaciers to feed summer ice melts, which in turn support hydroelectric power in the region, the effects once thought to be decades away are here and present right now.

In commenting about the new study, Professor Andrew Shepherd of the University of Leeds in the United Kingdom, had a sobering commentary.

“It’s great that we have satellites to track the pulse of our planet and models to perform a health check, but the diagnosis is shocking clear: our climate is sick and needs urgent,” he said.

“If Greenland has shifted into a new unstable state of heightened melting,” Shepherd continued, “then that’s big news.”