Patagonia Is Rapidly Rising Up in The Largest Glacial Adjustment Ever Recorded

Some of the fastest- melting glaciers on the planet are in the Patagonian ice fields. The earth that used to be beneath the glaciers is quickly returning to its former state.

A gap in the plates that formed 18 million years ago underneath the ice fields is believed to be the cause of the recent rapid rock movement in the area.

Variations in the size of glaciers, as they grow and shrink, combined with the mantle structure that we have imaged in this study, are driving rapid and spatially variable uplift in this region.

When glaciers melt, the earth that once lay beneath them recovers and rises, no longer being weighed down by ice sheets.

This isostatic adjustment occurs over thousands of years, not decades, and it appears to be happening in Patagonia. It affects how much global sea levels will rise under future climate warming scenarios that scientists are busy modeling.

The ice fields in the north and south are just a fraction of what they used to be.

A toe-length rise is an extreme, unusual, and sudden change on a continental scale, and the largest present-day glacier adjustment ever recorded.

Mark and his colleagues recorded data around the ice fields that straddle the Andes Mountains in southern Chile and Argentina to map what was happening below the surface.

The data collection was 10 months longer than planned because the instruments were trapped in the first year of the COVID-19 epidemic.

A gap in the down-going tectonic plate has allowed hotter, less viscous mantle material to flow underneath the continent.

If the estimates are correct, these lower-than-usual viscosities in the mantle beneath the ice fields could quicken the continental uplift associated with melting ice for decades or centuries.

The mantle responds to deglaciation on the time scale of tens of years, rather than thousands of years, as we observe in Canada, says seismologist Douglas Wiens of Washington University in St Louis.

This explains why the loss of ice mass has caused large uplift.

Douglas installs a device. Weins is from Washington University.

Washington University seismologist Douglas Weins and his team detected very slow seismic velocity, 8 percent slower than the global average.

The warm mantle temperatures likely eroded the overlying lithoosphere which is thin underneath the ice fields.

Estimates of mantle velocities are uncertain and sensitive to mantle temperatures, so the more measurements the better.

The study found that parts of the mantle were close to the gap, or slab window, below the part of the Patagonia ice fields that had opened up recently.

This suggests to us that the mantle dynamics associated with the slab window have intensified over time, or that the continental plate in the south started out thicker and colder, and so was less affected by the slab window than the part of the plate farther north.

As glaciers melt, they will contribute to global sea-level rise that already threatens low-lying communities.

A better understanding of the shifting land mass can improve predictions of sea-level rise, and what scientists learn about glaciers in one part of the world can aid studies of ice mass elsewhere.

Understanding the evolution of glaciers helps us understand what glaciers will look like in a warmer climate.

With better Earth models, we can do a better job of reconstructing recent changes in the Patagonian ice sheets.

The study was published in a journal.