‘Unknown territory’: Antarctic glaciers melting at rate unprecedented in 5,500 years: study

June 12, 2022 / activist360

“These currently elevated rates of ice melting may signal that those vital arteries from the heart of the West Antarctic Ice Sheet have been ruptured,” said one researcher. “Is it too late to stop the bleeding?”

By Julia Conley, Common Dreams (CC BY-NC-ND 3.0).

The human-caused climate crisis is pushing crucial glaciers in Antarctica to lose ice at a rate not seen in more than 5,000 years, according to a new study published Thursday.

Researchers at the University of Maine, the British Antarctic Survey, and Imperial College London found that the Pine Island and Thwaites glaciers on the West Antarctic Ice Sheet could cause global sea level rise of up to 3.4 meters, or over 11 feet, in the next several centuries due to their accelerated rate of ice loss.

“That the present-day rate of glacier retreat that has doubled over the past 30 years is, indeed, unprecedented.”

The glaciers—one of which, the Thwaites, has been called the “doomsday glacier” by climate scientists because of its potential to raise sea levels—are positioned in a way that allows increasingly warm ocean water to flow beneath them and erode the ice sheet from the base, causing “runaway ice loss,” the University of Maine team said in a statement.

The researchers examined penguin bones and seashells on ancient Antarctic beaches in order to analyze changes in local sea levels since the mid-Holocene period, 5,500 years ago.

Sea levels were higher and glaciers were smaller during the mid-Holocene, as the climate of the planet was warmer than it is today.

Since then, according to the study published in Nature Geoscience, relative sea levels have fallen steadily and the Thwaites and Pine Island glaciers have stayed relatively stable—until recent decades.

Ice loss was likely accelerated just prior to the mid-Holocene, and since then, the rate of relative decrease in sea levels over the past 5,500 years was almost five times smaller than it is in present day, due to “recent rapid ice mass loss,” according to the scientists.

“That the present-day rate of glacier retreat that has doubled over the past 30 years is, indeed, unprecedented,” wrote Caroline Brogan, a science reporter at Imperial College.

With the Thwaites spanning an area of more than 74,000 square miles and the Pine Island glacier spanning more than 62,600 square miles, the rapid ice loss of the two glaciers could cause major rises in sea levels around the globe.

Dylan Rood of Imperial College’s Department of Earth Science and Engineering, a co-author of the study, likened the two glaciers to arteries that have burst.

“These currently elevated rates of ice melting may signal that those vital arteries from the heart of the West Antarctic Ice Sheet have been ruptured, leading to accelerating flow into the ocean that is potentially disastrous for future global sea level in a warming world,” said Rood. “Is it too late to stop the bleeding?”

The study follows increasingly urgent calls from the Intergovernmental Panel on Climate Change, the International Energy Agency, and climate scientists around the world for an end to fossil fuel extraction, which is needed to achieve net-zero carbon emissions by 2050 and limit the average global temperature from rising more than 1.5°C above preindustrial levels.

Scientists have warned that the accelerated melting of the Thwaites glacier is likely irreversible.

“We’re going into unknown territory,” Scott Braddock, a researcher at University of Maine, told Science News. “We don’t have an analog to compare what’s going on today with what happened in the past.”

African Desert is Home to Abundant Forest Growth

November 2, 2020 / activist360 / Leave a comment

Researchers have found an unknown wealth of trees in an African desert zone supposedly too arid for green growth.

Rural Burkina Faso: Part of the Sahel, but with plenty of trees. Image: By Adam Jones, Ph.D., via Wikimedia Commons — *Burkina Faso: Part of the Sahel, but with plenty of trees. Image: By Adam Jones, Ph.D., via Wikimedia Commons.*

By Tim Radford, Climate News Network (CC BY-ND 4.0)

With help from high resolution satellite imagery and some advanced artificial intelligence techniques, European scientists have been counting the trees in a parched African desert.

They pored over 1.3 million square kilometres of the waterless western Sahara and the arid lands of the Sahel to the south, to identify what is in effect an unknown forest. This region − a stretch of dunes and dryland larger than Angola, or Peru, or Niger − proved to be home to 1.8 billion trees and shrubs with crowns larger than three square metres.

“We were very surprised to see that quite a few trees actually grow in the Sahara Desert because up till now, most people thought that virtually none existed. We counted hundreds of millions of trees in the desert alone,” said Martin Brandt, a geographer at the University of Copenhagen in Denmark, who led the research.

He and colleagues from Germany, France, Senegal, Belgium and Nasa in the US report in the journal Nature that they used an artificial intelligence technique called “deep learning” and satellite imagery so advanced that − from space − a camera could resolve an object half a metre or more in diameter, to see if they could answer unresolved questions about all those trees beyond the world’s forests.

Trees outside of forested areas are not usually included in climate models, and we know very little about their carbon stocks. They are an unknown component in the global carbon cycle”.
—Martin Brandt, lead researcher, University of Copenhagen

Trees matter, wherever they are. In cities, they enhance urban life and sustain property values. In forests, they conserve and recycle water, shelter millions of animals and smaller plants, and absorb atmospheric carbon. In grasslands they conserve soils, offer habitat for species and provide subsistence fuel, food and fodder for humans and animals.
But trees beyond the forests are an unknown factor when it comes to the puzzle of the global carbon budget and the great challenge of containing runaway climate change.

“Trees outside of forested areas are not usually included in climate models, and we know very little about their carbon stocks,” Dr Brandt said. “They are basically a white spot on maps and an unknown component in the global carbon cycle.”

The total identified in the target zone of the Sahara and the Sahel is almost certainly an under-estimate: the technology did not and could not pinpoint trees with a crown or shade area smaller than 3 square metres.

The study adds to the chronicle of surprises delivered by tree and forest research. In the last few years scientists have essayed a global census of woody growths wider than 5cms at breast height − that’s the botanist’s definition of a tree − and arrived at a total of more than 3 trillion.

New map possible

They have also counted the different kinds of tree: more than 60,000 species. They have already made attempts to measure the extent of tree cover in dryland and savannah regions and identified a kind of hidden forest.

They have calculated that a determined global tree planting campaign could absorb enough carbon to make a formidable difference to the challenge of global heating, and they have confirmed that conserved natural forests are, even on the simple basis of human economics, a bargain: forests are worth more to the world when they flourish than when they are cleared.

The new approach − the match of artificial intelligence with high resolution imagery − could one day help identify not just trees, but different tree species. It could, researchers hope, eventually even provide a reliable count of trees in a forest, although where canopies overlap it will always be difficult to number the trunks that support them. It offers the world’s forest scientists a new starting point for a map of all the planet’s trees.

“Doing so wouldn’t have been possible without this technology,” Dr Brandt said. “Indeed, I think it marks the beginning of a new scientific era.”

Original publication: Climate News Network — LONDON, 27 October, 2020

Tracking 3 Decades of Dramatic Glacial Lake Growth

September 5, 2020 / activist360 / Leave a comment

In the largest-ever study of glacial lakes, researchers using a 30-year satellite data record have found that the volume of these lakes worldwide has increased by about 50% since 1990.
Credits: NASA

In the largest-ever study of glacial lakes, researchers using 30 years of NASA satellite data have found that the volume of these lakes worldwide has increased by about 50% since 1990 as glaciers melt and retreat due to climate change.

The findings, published in the journal Nature Climate Change, will aid researchers assessing the potential hazards to communities downstream of these often unstable lakes and help improve the accuracy of sea-level rise estimates by advancing our understanding of how glacial meltwater is transported to the oceans.

Glaciers are retreating on a near-global scale and this study provides scientists with a clearer picture of how much of this water has been stored in lakes.

“We have known that not all meltwater is making it into the oceans immediately,” said lead author Dan Shugar of the University of Calgary in Canada. “But until now there were no data to estimate how much was being stored in lakes or groundwater.” The study estimates current glacial lake volumes total about 37.4 cubic miles (156 cubic kilometers) of water, the equivalent of about one-third the volume of Lake Erie.

Shugar and his collaborators from governments and universities in Canada, the United States, and the United Kingdom, working under a grant from NASA’s High Mountain Asia Program, initially planned to use satellite imaging and other remote-sensing data to study two dozen glacial lakes in High Mountain Asia, the geographic region that includes the Tibetan Plateau and surrounding mountain ranges, including the Himalaya.

“We wrote scripts in Google Earth Engine, an online platform for very large analyses of geospatial data, to look only at High Mountain Asia, and then decided to look at all glacial lakes in the world,” Shugar said. “From there, we were able to build a scaling relationship to estimate the volume of the world’s glacial lakes based on the area of this large population of lakes.”

The team ultimately analyzed more than 250,000 scenes from the Landsat satellite missions, a joint NASA/U.S. Geological Survey program. A decade ago it would not have been possible to process and analyze this volume of data. The team looked at the data in five time-steps beginning with 1990 to examine all the glaciated regions of the world except Antarctica and analyze how glacial lakes changed over that period.

Shugar points out that while water from melting glaciers stored in glacial lakes is a relatively small contributor to overall sea level rise, it can have a major impact on mountain communities downstream of these glacial lakes.

Glacial lakes are not stable like the lakes in which most people are used to swimming or boating because they are often dammed by ice or glacial sediment called a moraine, which is composed of loose rock and debris that is pushed to the front and sides of glaciers. Rather, they can be quite unstable and can burst their banks or dams, causing massive floods downstream. These kinds of floods from glacial lakes, known as glacial lake outburst floods, have been responsible for thousands of deaths over the past century, as well as the destruction of villages, infrastructure, and livestock. A glacial lake outburst flood affected the Hunza Valley in Pakistan in May 2020.

“This is an issue for many parts of the world where people live downstream from these hazardous lakes, mostly in the Andes and in places like Bhutan and Nepal, where these floods can be devastating,” Shugar said. “Fortunately, organizations like the United Nations are facilitating a lot of monitoring and some mitigation work where they’re lowering the lakes to try and decrease the risks.”

In North America, the risks posed by a glacial lake outburst flood are lower.

“We don’t have much in the way of infrastructure or communities that are downstream,” Shugar said. “But we’re not immune to it.”

For more information about NASA’s Earth science programs, visit https://www.nasa.gov/earth.