Hexbyte Glen Cove Pine Island Glacier's ice shelf is ripping apart, speeding up key Antarctic glacier thumbnail

Hexbyte Glen Cove Pine Island Glacier’s ice shelf is ripping apart, speeding up key Antarctic glacier

Hexbyte Glen Cove

Pine Island Glacier ends in an ice shelf that floats in the Amundsen Sea. These crevasses are near the grounding line, where the glacier makes contact with the Antarctic continent. The photo was taken in January 2010 from the east side of the glacier, looking westward. This ice shelf lost one-fifth of its area from 2017 to 2020, causing the inland glacier to speed up by 12%. Credit: Ian Joughin/University of Washington

For decades, the ice shelf helping to hold back one of the fastest-moving glaciers in Antarctica has gradually thinned. Analysis of satellite images reveals a more dramatic process in recent years: From 2017 to 2020, large icebergs at the ice shelf’s edge broke off, and the glacier sped up.

Since floating ice shelves help to hold back the larger grounded mass of the glacier, the recent speedup due to the weakening edge could shorten the timeline for Pine Island Glacier’s eventual collapse into the sea. The study from researchers at the University of Washington and British Antarctic Survey was published June 11 in the open-access journal Science Advances.

“We may not have the luxury of waiting for slow changes on Pine Island; things could actually go much quicker than expected,” said lead author Ian Joughin, a glaciologist at the UW Applied Physics Laboratory. “The processes we’d been studying in this region were leading to an irreversible collapse, but at a fairly measured pace. Things could be much more abrupt if we lose the rest of that ice shelf.”

Pine Island Glacier contains approximately 180 trillion tons of ice—equivalent to 0.5 meters, or 1.6 feet, of . It is already responsible for much of Antarctica’s contribution to sea-level rise, causing about one-sixth of a millimeter of sea level rise each year, or about two-thirds of an inch per century, a rate that’s expected to increase. If it and neighboring Thwaites Glacier speed up and flow completely into the ocean, releasing their hold on the larger West Antarctic Ice Sheet, global seas could rise by several feet over the next few centuries.

These have attracted attention in recent decades as their thinned because warmer ocean currents melted the ice’s underside. From the 1990s to 2009, Pine Island Glacier’s motion toward the sea accelerated from 2.5 kilometers per year to 4 kilometers per year (1.5 miles per year to 2.5 miles per year). The glacier’s speed then stabilized for almost a decade.

Results show that what’s happened more recently is a different process, Joughin said, related to internal forces on the glacier.

From 2017 to 2020, Pine Island’s ice shelf lost one-fifth of its area in a few dramatic breaks that were captured by the Copernicus Sentinel-1 satellites, operated by the European Space Agency on behalf of the European Union. The researchers analyzed images from January 2015 to March 2020 and found that the recent changes on the ice shelf were not caused by processes directly related to ocean melting.

The ice shelf on Antarctica’s Pine Island Glacier lost about one-fifth of its area from 2017 to 2020, mostly in three dramatic breaks. The timelapse video incorporates satellite images from January 2015 to March 2020. For most of the first two years, the satellite took high-resolution images every 12 days; then for more than three years it captured images of the ice shelf every six days. Images are from the Copernicus Sentinel-1 satellites operated by the European Space Agency on behalf of the European Union. Credit: Joughin et al./Science Advances

“The ice shelf appears to be ripping itself apart due to the glacier’s acceleration in the past decade or two,” Joughin said.

Two points on the glacier’s surface that were analyzed in the paper sped up by 12% between 2017 and 2020. The authors used an ice flow model developed at the UW to confirm that the loss of the ice shelf caused the observed speedup.

“The recent changes in speed are not due to melt-driven thinning; instead they’re due to the loss of the outer part of the ice shelf,” Joughin said. “The glacier’s speedup is not catastrophic at this point. But if the rest of that ice shelf breaks up and goes away then this glacier could speed up quite a lot.”

It’s not clear whether the shelf will continue to crumble. Other factors, like the slope of the land below the glacier’s receding edge, will come into play, Joughin said. But the results change the timeline for when Pine Island’s ice shelf might disappear and how fast the glacier might move, boosting its contribution to rising seas.

“The loss of Pine Island’s ice shelf now looks like it possibly could occur in the next decade or two, as opposed to the melt-driven subsurface change playing out over 100 or more years,” said co-author Pierre Dutrieux, an ocean physicist at British Antarctic Survey. “So it’s a potentially much more rapid and abrupt change.”

Pine Island’s ice shelf is important because it’s helping to hold back this relatively unstable West Antarctic glacier, the way the curved buttresses on Notre Dame cathedral hold up the cathedral’s mass. Once those buttresses are removed, the slow-moving glacier can flow more quickly downward to the ocean, contributing to rising seas.

“Sediment records in front of and beneath the Pine Island indicate that the glacier front has remained relatively stable over a few thousand years,” Dutrieux said. “Regular advance and break-ups happened at approximately the same location until 2017, and then successively worsened each year until 2020.”

More information:
Ice-shelf retreat drives recent Pine Island Glacier speedup, Science Advances (2021). DOI: 10.1126/sciadv.abg3080 , advances.sciencemag.org/content/7/24/eabg3080

Pine Island Glacier’s ice shelf is ripping apart, speeding up key Antarctic glacier (2021, June 11)
retrieved 12 June 2021
from https://phys.org/news/2021-06-island-glacier-ice-shelf-ripping.html

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Hexbyte Glen Cove Retreating glaciers threaten herbs used to make iconic alpine liqueurs thumbnail

Hexbyte Glen Cove Retreating glaciers threaten herbs used to make iconic alpine liqueurs

Hexbyte Glen Cove

Saxifrage oppositifolia, or purple mountain saxifrage, grows directly on a rock face in the Alps. Credit: Appollonio Tottoli

Alpine landscapes are irrevocably changing: scientists estimate that the Alps may be glacier-free by the end of this century. As the ice melts, the unique ecosystems that exist at their edges are also fading. New research published in Frontiers in Ecology and Evolution untangled what changing flora might mean for the ecology, economy and culture of the region.

The Alps, known for their meadows brimming with wildflowers in the spring and summer, are home to many that are specialized for glacial growing conditions. Many of these plants are fragrant herbs, some of which have been used to make medicines and liqueurs for centuries. These distinctive, have become an important part of the culture and economy of the mountains. The herbs are part of a landscape that hosts a dynamic, evolving system of plants that scientists are watching shift in real-time.

As glaciers retreat, they expose new land which is readily colonized by plants. “The retreat of glaciers is a double-edged sword,” said lead author Gianalberto Losapio in an interview with GlacierHub. “There is an initial increase in biodiversity because the retreating glaciers are making space available. If today there is ice and the glacier is retreating, it means that tomorrow there might be new terrain because the ice is gone, which means that seeds can grow.”

At the fringes of a glacier, the soil that is exposed is often not well-suited to hosting plant life. There is often more rocky debris than soil, and the soil that is present is not always rich in the nutrients that plants need. Many native Alpine herbs have carved out a niche for themselves in these proglacial areas. These plants, which survive where others cannot, are called “pioneers” by ecologists. “The initial plants, the pioneers, are adapted to living in this harsh environment,” said Losapio.

The pioneer species are often small and low to the ground. They don’t need much in the way of soil or nutrients to grow. In the past, these were the only plants able to survive at the edges of a glacier. Now, with year-round ice-free ground, the proglacial habitats are narrowing.

Ranunculus glacialis, or Arctic Buttercup, is a pioneer species. Credit: Gianalberto Losapio

The pioneer species not only establish themselves, but also prime the land for new plants to thrive by building up biomass and providing nutrients. “These early plants improve the environment in such a way that other plants can benefit from,” said Losapio. “The higher the colonization, the more this facilitation and mutualistic interaction take place, which increases biodiversity.”

After the early plants have done the work of stabilizing the landscape, other plants move in. The later species that enter are not as well-suited for the difficult initial growing conditions as the pioneer plants are, but thrive on the land primed by them. In the past, the ice returned after a few short months and later species did not have time to establish. But now, with many glaciers disappearing and the annual period of snow cover shrinking, the later species have a new opening.

As the later species move in, the dynamic of the area changes. “The arrival of the late species increases the competition,” said Losapio. “They require more organic matter and they also reproduce vegetatively, not with seeds, so they occupy much more of the space.”

The later plants piggy-back off the conditions that the hardy, early species help create. And then, they take over. The later species reproduce much faster than the , and take up more resources, leaving little space for the slower-growing plants that came before them.

Many of the early species, including Arctic buttercup, saxifrage, and wormwood, simply cannot compete with these fast-growing newcomers. Eventually, the later species might be all that is left on high-elevation Alpine land. “The area is going to be much more dominated by grasslands,” said Losapio. “This is going to decrease biodiversity in general.”

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Artemisia genipi growing in the Alps. Credit: Cyril Gros

These effects extend beyond just the plants; insect populations could suffer, too. “We also observed a decline in insect-pollinated species,” explained Losapio “[Insect] populations are very high in pioneer and initial stages, but the plants in grasslands are not usually pollinated by insects.”

In addition to changing the appearance and biodiversity of the area, the shifts due to deglaciation could also have economic and cultural impacts. Among the pioneer plants that are being squeezed out is Artemisia genipi, often called simply genipi, genepy or black wormwood. “Artemisia genipi is a very rare, iconic plant. Already, after 100 years of glacier retreat, it has been declining,” said Losapio. “Its distribution is very narrow. It grows only in the northwestern Alps. Culturally it is super important. Hikers up in the mountains go and they stop at a hut, they have a piece of cake and a shot of genepi.”

Varieties of Artemisia have been used throughout Europe since Roman times as a key ingredient in medicines. “Genepi varieties have historically been used in folk and because of their bioactivity,” said Alessio Anselmo, an herbal technician with Italian Alpine liqueur producer Bordiga, in an interview with GlacierHub. “They were known and used as thermogenic agents against the common cold, in infusions against fever, and in aromatic wines and liqueurs to stimulate appetite and digestion.”

Centuries of production of Artemisia genipi–infused drinks has led the flavor to become an emblem of the region. “To produce genepi liqueur, the aerial parts and flowers are introduced into a hydroalcoholic solution and rest lightless at ambient temperature for 40 days,” explains Anselmo. “Then the solid parts are pressed with a hydraulic press and the infusion rests for some months. Finally, the infusion is mixed with alcohol, water and sugar, filtered and bottled.”

Traditional recipes for absinthe, Chartreuse, amari and various other alpine liqueurs use Artemisia genipi as a key ingredient. “Artemesia genepi is a type of wormwood and as such, adds a bitter vegetal flavor to the spirit,” said David Curiel, spirits specialist with the importer Oliver McCrum Wines & Spirits in an interview with GlacierHub. “It’s a distinct alpine flavor that embodies the sense of place.”

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A selection of beverages that feature Alpine herbs. Credit: Alpe & Bordiga

Today, producers throughout the Alps continue to make liqueurs and fortified wines using Artemisia and other Alpine herbs. Once primarily consumed by chilly mountain hikers as a respite from Alpine snow and ice, Artemisia genipi has found a new home in cocktail bars across the world.

“Most people [in the United States] tend to be familiar with these flavors because of Chartreuse, possibly the biggest commercial exporter of genepi, but the category is actually quite broad in Europe,” said Curiel. “[In the Alps,] Artemisia genipi commonly finds itself being consumed during the colder months, maybe in a ski lodge, sitting by a fire. Here in the U.S., the craft cocktail scene seems to lean into using it in refreshing citrus-driven cocktails that you might consume in the summer while sitting on a patio, or poolside.”

Even American producers have been trying their hand at Artemisia genipi–based liqueurs. At Forthave Spirits in Brooklyn, New York co-founders Aaron Sing Fox and Daniel de la Nuez have been making botanical liqueurs since 2013. “Genepi has a very complex, enchanting and difficult to describe flavor,” Fox told GlacierHub. “We wanted to make something that highlighted the delicate aspects of this botanical so we used it to make a wine-based aperitif.”

Fox and de la Nuez source their Artemisia genipi not from the wild, but from a grower in the Alps who cultivates a very limited crop each year. Still, the loss of wild genipi looms large. “The loss of wild genepi would be heartbreaking,” said Fox. “There is much more to learn and explore from the many wild genepi that are out there.”

More information:
Gianalberto Losapio et al. The Consequences of Glacier Retreat Are Uneven Between Plant Species, Frontiers in Ecology and Evolution (2021). DOI: 10.3389/fevo.2020.616562

This story is republished courtesy of Earth Institute, Columbia University http://blogs.ei.columbia.edu.

Retreating glaciers threaten herbs used to make iconic alpine liqueurs (2021, March 10)
retrieved 11 March 2021
from https://phys.org/news/2021-03-retreating-glaciers-threaten-herbs-iconic.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purpos

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