PHOTOGRAPH BY MARIO TAMA/ GETTY
Something truly strange is happening in Greenland.
Back in Dec of 2018, a study published in Nature reported the following rather predictable observational consequence of Climate Change – a greatly increased rate of melting …
Nonlinear rise in Greenland runoff in response to post-industrial Arctic warming
…We find that the initiation of increases in Greenland ice sheet melting closely follow the onset of industrial-era Arctic warming in the mid-1800s, but that the magnitude of Greenland ice sheet melting has only recently emerged beyond the range of natural variability. Owing to a nonlinear response of surface melting to increasing summer air temperatures, continued atmospheric warming will lead to rapid increases in Greenland ice sheet runoff and sea-level contributions….
Via a new study we now have a deeper understanding of what is happening. Global Warming is not simply causing increasing rates of melt in Greenland, it is also transforming the very structure of the Greenland ice sheet. It is being changed in a manner that has very dire consequences for all of us.
Study: Rapid expansion of Greenland’s low-permeability ice slabs
Published in Nature last wednesday (18th Sept 2019), it lays out the latest insight step by step as follows …
What was known …
In recent decades, meltwater runoff has accelerated to become the dominant mechanism for mass loss in the Greenland ice sheet1,2,3.
The “snowcone” …
In Greenland’s high-elevation interior, porous snow and firn accumulate; these can absorb surface meltwater and inhibit runoff4, but this buffering effect is limited if enough water refreezes near the surface to restrict percolation5,6. However, the influence of refreezing on runoff from Greenland remains largely unquantified.
The “popsicle” …
Here we use firn cores, radar observations and regional climate models to show that recent increases in meltwater have resulted in the formation of metres-thick, low-permeability ‘ice slabs’ that have expanded the Greenland ice sheet’s total runoff area by 26 ± 3 per cent since 2001.
The Implications …
Although runoff from the top of ice slabs has added less than one millimetre to global sea-level rise so far, this contribution will grow substantially as ice slabs expand inland in a warming climate. Runoff over ice slabs is set to contribute 7 to 33 millimetres and 17 to 74 millimetres to global sea-level rise by 2100 under moderate- and high-emissions scenarios, respectively—approximately double the estimated runoff from Greenland’s high-elevation interior, as predicted by surface mass balance models without ice slabs. Ice slabs will have an important role in enhancing surface meltwater feedback processes, fundamentally altering the ice sheet’s present and future hydrology.
National Geographic also covers the Greenland ice slab story …
Published in conjunction with the study, “Unprecedented” is the term deployed …
To Poinar, the most significant contribution of the new study is that it will allow scientists to improve their projections of future sea level rise, giving coastal communities the information they need to prepare. At the same time, the study highlights the fact that the more carbon we spew into the atmosphere, the more we’re likely to transform Earth’s northern ice sheet in insidious and unexpected ways. And that could have consequences that are difficult to anticipate.
“We have never observed an ice sheet behaving this way before,” Poinar says. “It’s unprecedented in human scientific history.”
Often we think we understand and we believe we have a handle on how things will play out, then reality comes calling and knocks on our doors.
Further Reading
- Nature (Dec 2018) – Nonlinear rise in Greenland runoff in response to post-industrial Arctic warming
- Nature (18th Sept 2019) – Rapid expansion of Greenland’s low-permeability ice slabs
- National Geographic (18th Sept 2019) – Something strange is happening to Greenland’s ice sheet – What should be like a snowcone is becoming more like a popsicle, speeding up the runoff from the melting ice sheet.