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The Best-Case Scenario for Greenlands Ice Sheet CONTINUES TO BE Pretty Awful

Im standing at the edge of the Greenland ice sheet, mesmerized by way of a mind-blowing scene of natural destruction. A mile-wide portion of glacier front has fractured and is collapsing in to the ocean, calving an immense iceberg.

Seracs, giant columns of ice the height of three-story houses, are increasingly being tossed around like dice. And the previously submerged part of this immense block of glacier ice just breached the oceana frothing maelstrom flinging ice of several tons high in to the air. The resulting tsunami inundates all in its path since it radiates from the glaciers calving front.

Fortunately, Im watching from the clifftop a few miles away. But even here, I could have the seismic shocks through the bottom.

Regardless of the spectacle, Im keenly aware that spells yet more unwelcome news for the worlds low-lying coastlines.

As a field glaciologist, Ive done ice sheets for a lot more than 30 years. For the reason that time, I’ve witnessed some gobsmacking changes. Recent years specifically have already been unnerving for the sheer rate and magnitude of change underway. My revered textbooks taught me that ice sheets respond over millennial time scales, but thats not what were seeing today.

A report published Aug. 29, 2022, demonstratesfor the initial timethat Greenlands ice sheet is currently so out of balance with prevailing Arctic climate that it no more can sustain its current size. It really is irreversibly focused on retreat by at the very least 59,000 square kilometers (22,780 square miles), a location considerably bigger than Denmark, Greenlands protectorate state.

Even though all of the greenhouse gas emissions driving global warming ceased today, we discover that Greenlands ice loss under current temperatures will raise global sea level by at the very least 10.8 inches (27.4 centimeters). Thats a lot more than current models forecast, and its own an extremely conservative estimate. If each year were like 2012, when Greenland experienced a heat wave, that irreversible commitment to sea level rise would triple. Thats an ominous portent considering that they are climate conditions we’ve already seen, not just a hypothetical future scenario.

Our study requires a new approachit is founded on observations and glaciological theory instead of sophisticated numerical models. The existing generation of coupled climate and ice sheet models used to forecast future sea level rise neglect to capture the emerging processes that people see amplifying Greenlands ice loss.

An iceberg floats in Baffin Bay in the Arctic Ocean on July 20, 2022 near Pituffik, Greenland.

Kerem Yucel/AFP via Getty

The Greenland ice sheet is really a massive, frozen reservoir that resembles an inverted pudding bowl. The ice is in constant flux, flowing from the interiorwhere it really is over 1.9 miles (3 kilometers) thick, cold and snowyto its edges, where in fact the ice melts or calves bergs.

In every, the ice sheet locks up enough fresh water to improve global sea level by 24 feet (7.4 meters).

Greenlands terrestrial ice has existed for approximately 2.6 million years and contains expanded and contracted with two dozen roughly ice age cycles lasting 70,000 or 100,000 years, punctuated by around 10,000-year warm interglacials. Each glacial is driven by shifts in Earths orbit that modulate just how much solar radiation reaches the Earths surface. These variations are then reinforced by snow reflectivity, or albedo; atmospheric greenhouse gasses; and ocean circulation that redistributes that heat round the planet.

We have been currently enjoying an interglacial periodthe Holocene. For days gone by 6,000 years Greenland, just like the remaining planet, has benefited from the mild and stable climate having an ice sheet in equilibriumuntil recently. Since 1990, because the atmosphere and ocean have warmed under rapidly increasing greenhouse gas emissions, Greenlands mass balance went in to the red. Ice losses because of enhanced melt, rain, ice flow and calving now far exceed the web gain from snow accumulation.

The critical questions are, how fast is Greenland losing its ice, and what does it mean for future sea level rise?

Greenlands ice loss has been contributing about 0.04 inches (1 millimeter) each year to global sea level rise in the last decade.

This net loss is split between surface melt and dynamic processes that accelerate outlet glacier flow and so are greatly exacerbated by atmospheric and oceanic warming, respectively. Though complex in its manifestation, the idea is easy: Ice sheets dont like the sunshine or baths, and heat is on.

What the near future provides is trickier to answer.

The models utilized by the Intergovernmental Panel on Climate Change predict a sea level rise contribution from Greenland of around 4 inches (10 centimeters) by 2100, with a worst-case scenario of 6 inches (15 centimeters).

But that prediction reaches odds using what field scientists are witnessing from the ice sheet itself.

In accordance with our findings, Greenland will eventually lose at the very least 3.3% of its ice, over 100 trillion metric tons. This loss has already been committedice that has to melt and calve icebergs to re-establish Greenlands balance with prevailing climate.

Were observing many emerging processes that the models dont take into account that raise the ice sheets vulnerability. For instance:

  • Increased rain is accelerating surface melt and ice flow.
  • Large tracts of the ice surface are undergoing bio-albedo darkening, which accelerates surface melt, and also the impact of snow melting and refreezing at the top. These darker surfaces absorb more solar radiation, driving yet more melt.
  • Warm, subtropical-originating ocean currents are intruding into Greenlands fjords and rapidly eroding outlet glaciers, undercutting and destabilizing their calving fronts.
  • Supraglacial lakes and river networks are draining into fractures and moulins, bringing using them vast levels of latent heat. This cryo-hydraulic warming within and at the bottom of the ice sheet softens and thaws the bed, thereby accelerating interior ice flow right down to the margins.

Area of the problem is that the models useful for forecasting are mathematical abstractions offering only processes which are fully understood, quantifiable and deemed important.

Meltwater flows from the Greenland ice sheet in to the Baffin Bay.

Kerem Yucel/AFP via Getty

Models reduce reality to a couple of equations which are solved repeatedly on banks of extremely fast computers. Anyone into cutting-edge engineeringincluding meknows the intrinsic value of models for experimentation and testing of ideas. However they are no replacement for reality and observation. It really is apparent that current model forecasts of global sea level rise underestimate its actual threat on the 21st century. Developers are making constant improvements, but its tricky, and theres a dawning realization that the complex models useful for long-term sea level forecasting aren’t fit for purpose.

Additionally, there are unknown unknownsthose processes and feedbacks that people dont yet realize and that models can’t ever anticipate. They may be understood only by direct observations and literally drilling in to the ice.

Thats why, instead of using models, we base our study on proven glaciological theory constrained by 2 decades of actual measurements from weather stations, satellites and ice geophysics.

Its an understatement that the societal stakes are high, and the chance is tragically real in the years ahead. The results of catastrophic coastal flooding as sea level rises remain unimaginable to a lot of the billion roughly people who reside in low-lying coastal zones of the earth.

Personally, I remain hopeful that people can get on the right track. I dont believe weve passed any doom-laden tipping point that irreversibly floods the planets coastlines. Of what I am aware of the ice sheet and the insight our new study brings, its not too late to do something.

But fossil fuels and emissions should be curtailed now, because time is short and the water risesfaster than forecast.

Alun Hubbard is really a professor of glaciology and Arctic Five Chair at the University of Troms

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