What Greenland and Antarctica look like without ice | Polarjournal
The Greenland Ice Sheet, with its approximately 1.7 million square kilometers, is the second largest ice sheet in the world and comprises about 2.85 million cubic kilometers of ice. The weight is so great that the lowest point of the island is over a hundred meters below sea level, while the highest point is over 3,600 meters above sea level. Image: Michael Wenger

One of the biggest fears surrounding the effects of global climate change is the melting of the ice sheets covering Greenland and Antarctica. The masses of frozen water are so enormous that not only would sea levels rise by about 66 meters if they melted. Rather, the two land masses lying under the ice would also lose a lot of weight and come back to the surface like a cork (only slower). Three researchers from Columbia University have found out how the appearance of Greenland and Antarctica will change in the process.

Guy Paxman, Jacqueline Austermann and Andrew Hollyday, all of Columbia University’s Lamont-Doherty Earth Observatory, calculated that the center of Greenland will rise 783 meters and that of Antarctica as much as 936 meters when all the ice masses are gone. In contrast, the researchers said, regions at the ice margins would sink by as much as 123 meters, a somewhat surprising finding. The results of the study were published in the latest issue of the journal Scientific Reports.

The team published maps of what Greenland and Antarctica would look like if the ice were gone but the landmasses were still pushed into the Earth’s crust, and how the isostatic rebound would then raise the land masses while lowering the coastal regions due to sea-level rise, collapse of the marginal bulges, and water accumulation. The maps also show the different elevation ranges of the land masses (in brown). Maps: Paxman et al (2022) Scie Rep, Video: Michael Wenger

The weight of the ice masses, which total about 2.8 million cubic kilometers in Greenland and about 26.5 million cubic kilometers in Antarctica, is so great that the land masses are pushed deep into the earth’s crust. When the ice melts away, a process that takes several thousand years, the landmasses lift out of the Earth’s crust like a cork that had been pushed under water. This process is called isostatic rebound. However, the rate and how the land masses will change depends on numerous factors. The study’s research team used a complex model in which the elasticity of the Earth’s crust, the viscoelastic properties due to self-gravity, and also the lateral variations in the Earth’s structure, an aspect that, according to the team, has often been ignored in previous models. The team also used the most recent and detailed data on ice thickness in the different regions. The data was entered into a program and divided into fields, allowing the team to create high-resolution maps. The results show that Greenland’s terrain, which is currently below sea level, would experience the greatest uplift, rising between three hundret and eight hundret meters in elevation. In Antarctica, where two large ice sheets cover the continent, the rise can exceed more than nine hundret meters.

Not all land masses would rise. Many coastal areas of Greenland and Antarctica (here the Ross Sea area) are not covered by ice and would be inundated by sea level rise, while marginal bulges could collapse. Image: Michael Wenger

However, the results of the study showed not only an increase in land mass heights. At the margins, according to the model calculations, the collapse of the marginal bulges that formed at the ice sheet margins and the rise in sea level would cause the land masses to sink by about 100 meters, thus changing the coastal region, the team explained in its paper. However, the study did not provide information on the time horizon for how long these changes to the landscapes would last. As a result, factors such as erosion, sedimentation and tectonic deformation were not included in the calculations. But the team is convinced that their study makes an important contribution in the field of ice sheet dynamics and landscape evolution, even if the latter is likely to take several thousand years.

Dr. Michael Wenger, PolarJournal

Link to the study: Paxman et al (2022) Sci Rep 12 (11399) Total isostatic response to the complete unloading of the Greenland and Antarctic Ice Sheets, https://doi.org/10.1038/s41598-022-15440-y

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