Greenland
Climate Change Daily Earth Science Repost

Greenland rises while Miami sinks

Glaciers permanently disappear, fueling sea-level rise and isostatic rebound

The past two decades may turn out to be the tipping point, triggering a permanent meltdown of the Greenland ice sheet. A new study by scientists at Ohio State University (King et al.) used four decades of satellite data to trace Greenland’s ice-loss history. The study found that from 2000 forward, the continent lost more ice each year than was replaced by snow. Greenland is now the largest contributor on the planet to sea-level rise. Also, its glaciers are retreating, and eventually leaving more usable land for its citizens—a winning position. But Miami is one of the losers, with land disappearing as it slowly sinks below rising seas.

Ice loss across Greenland is accelerating, and these losses come in two varieties. The first, and most apparent, is summer meltwater flowing off the continent and into the North Atlantic Ocean. The second mechanism is glaciers calving ice into the sea. During the early 2000s, ice loss was evenly split between these two mechanisms. But more recently, melting became the dominant ice-loss pathway. 

During 2017 and 2018, Greenland lost a trillion tons of ice. Then, in 2019, a massive heatwave melted 55 billion tons of ice in just five days.  Researchers say the ice-loss rates identified by the new research “effectively shift the ice sheet to a state of persistent mass loss.” Yes, Greenland may actually be green in the future.

 Isostatic rebound

One of the tools used to review ice loss was gravity surveys. Researchers found ice loss was severe enough to affect the continent’s gravitational field.  While this is alarming in one sense, it also points to an interesting future. A future where Greenland physically rises higher, while Miami sinks below the ocean. Geologists call the effect “isostatic rebound.”

Thick ice sheets are heavy, and over time their extra weight causes the landmass underneath to sink. The entire continental crust is depressed by the weight of the ice. Removing the ice has the opposite effect, and the crust rebounds to its pre-glacial position.

The average thickness of the Greenland ice sheet is 5,000 feet, so the pressure at the base of this sheet is about 2200 pounds-per-square-inch (psi). For comparison, the pressure of the atmosphere at sea level is about 14.7 psi. Melting will lift a heavy load off the continent and put Miami 20 feet underwater.

Tipping points

One key conclusion from the Ohio State research was Greenland’s ice loss has reached a tipping point. Remember, a tipping point is a critical point in a system, beyond which unstoppable or irreversible change occurs. This critical point is also referred to as a threshold point. 

Envision a day at the water park. The sun is beating down, and you decide to venture up the winding stairs to the top of the water slide. After a wait, your time comes. You sit on your mat and inch forward towards the point where the slide starts to slope downward. You can still back out, hang your head in shame, and descend via the stairs. But you press on, and at a single point in the process, your fate is sealed. As you move past the flat entry zone, the slide picks up slope and gravity takes hold. Once you pass this point, there’s no going back.

The threshold point, where gravity overcomes friction, is the tipping point of this system. Once you pass this tipping point, you can thrash, holler, and flail your limbs erratically, but you are going to the bottom whether-or-not you want to. There is no stopping until gravity has converted all your potential energy into kinetic energy, and you splash into the receiving pool at the bottom of the slide.

Environmental tipping points are the same. We can move to net-zero carbon emissions or even zero carbon emissions, but the ice will still melt. We can’t stop the process. It must run its course until all the ice is gone. If the Ohio State researchers are correct, the world has just passed one of its first major tipping points. We are headed down the slide, whether we like it or not. It’s sort of scary stuff.

The future is here

Climate change is upon us. It’s not a dystopic vision of the future; it’s reality. We are moving towards a warmer planet, and our collective efforts to mitigate climate change can ease the transition, but massive environmental changes are already in motion. Events like the melting of the Greenland ice sheet reach tipping points, and changes cannot be stopped. However, the outlook is not all gloom and doom. Humans are smart, adaptable, and creative. We have the innate ability to create a sustainable, healthy environment, but only if we acknowledge the problem and collectively work together to solve it. The most challenging part is global problems require global solutions. But we are still mostly a collection of disparate regions seeking national solutions, not global ones.


ArcheanWeb:

Much ado about tipping points (Source: ArcheanWeb) – https://archeanweb.com/2020/01/10/much-ado-about-tipping-points/  Also

Sources:

Greenland’s ice sheet has melted to a point of no return, study finds (By  Max Claypool and Brandon Miller; CNN) – https://www.cnn.com/2020/08/14/weather/greenland-ice-sheet/index.html   Also:

Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat (By Michalea D. King, Ian M. Howat, Salvatore G. Candela, Myoung J. Noh, Seonsgu Jeong, Brice P. Y. Noël, Michiel R. van den Broeke, Bert Wouters & Adelaide Negrete; Nature – Communications Earth & Environment) –   https://www.nature.com/articles/s43247-020-0001-2  Also:

Greenland’s Melting Ice Sheet Has ‘Passed The Point of No Return’, Scientists Say, dooming it to disappear (By Morgan McFall-Johnsen; Business Insider) – https://www.businessinsider.com/greenland-melting-ice-sheet-past-tipping-point-2020-8 Also:

Greenland Ice Sheet (Modified) – By Christine Zenino from Chicago, US – Greenland Ice Sheet, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=16542472  

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.

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