Warmer Current Is Carving Away Greenland Ice Sheet From Below, Scientists Find

The Greenland ice sheet is melting faster than ever recorded in modern history. New research finds that the world's second-largest ice deposit is not just melting from the surface but from below as well, which adds a new twist to consider when predicting global sea level rise.
The Arctic ice sheet stores large quantities of frozen water extending 1.7 million square kilometers (656,000 square miles) long, according to the National Snow and Ice Data Center. In recent years it has seen unprecedented melting — seven times faster today than in the 1990s — that is likely to be intensified by the climate crisis. Scientists estimate that if the Greenland Ice Sheet completely melted, sea levels would rise by about 20 feet.
Researchers have long known that surface melt occurs from exposure to the sun and rising temperatures, but Arctic scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) in Germany have now determined that an underwater current of warmer water is carving a destructive path below the surface.
To come to their findings, the team took to the 79 North Glacier, a 50-mile-long "tongue" of floating ice that has slid into the ocean and floats on the surface while remaining connected to the land ice. In the last two decades the 79 North Glacier has seen dramatic loss of both its mass and thickness. The first-ever extensive ship-based survey of the ocean floor revealed an underwater current more than a mile-wide arriving from the Atlantic Ocean, bringing heat into contact with the glacier to accelerate its melting.
"The reason for the intensified melting is now clear," researcher Janin Schaffer said, according to EurekAlert!. "Because the warm water current is larger, substantially more warmth now makes its way under the ice tongue, second for second."
Schaffer and her team also found what is known as a bathymetric sill, which acts as a dam to water flowing over the seafloor. As water builds up against this barrier, it grows until eventually rushing over and coming into contact with the tongue, further melting the ice from below.
"The readings indicate that here, too, a bathymetric sill near the seafloor accelerates warm water toward the glacier. Apparently, the intensive melting on the underside of the ice at several sites throughout Greenland is largely produced by the form of the seafloor,"Schaffer said.
Writing in Nature Geoscience, the study authors add that similar effects were seen at other parts of the Greenland Ice Sheet as well. The researchers say that their findings may help to more accurately gauge the total amount of meltwater lost from the ice sheet each year.
- Redwoods are the world's tallest trees.
- Now scientists have discovered they are even bigger than we thought.
- Using laser technology they map the 80-meter giants.
- Trees are a key plank in the fight against climate change.
They are among the largest trees in the world, descendants of forests where dinosaurs roamed.
Pixabay / Simi Luft
<p><span>Until recently, measuring these trees meant scaling their 80 meter high trunks with a tape measure. Now, a team of scientists from University College London and the University of Maryland uses advanced laser scanning, to create 3D maps and calculate the total mass.</span></p><p>The results are striking: suggesting the trees <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">may be as much as 30% larger than earlier measurements suggested.</a> Part of that could be due to the additional trunks the Redwoods can grow as they age, <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">a process known as reiteration</a>.</p>New 3D measurements of large redwood trees for biomass and structure. Nature / UCL
<p>Measuring the trees more accurately is important because carbon capture will probably play a key role in the battle against climate change. Forest <a href="https://www.wri.org/blog/2020/09/carbon-sequestration-natural-forest-regrowth" target="_blank">growth could absorb billions of tons</a> of carbon dioxide from the atmosphere each year.</p><p>"The importance of big trees is widely-recognised in terms of carbon storage, demographics and impact on their surrounding ecosystems," the authors wrote<a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank"> in the journal Nature</a>. "Unfortunately the importance of big trees is in direct proportion to the difficulty of measuring them."</p><p>Redwoods are so long lived because of their ability to <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">cope with climate change, resist disease and even survive fire damage</a>, the scientists say. Almost a fifth of their volume may be bark, which helps protect them.</p>Carbon Capture Champions
<p><span>Earlier research by scientists at Humboldt University and the University of Washington found that </span><a href="https://www.sciencedirect.com/science/article/pii/S0378112716302584" target="_blank" rel="noopener noreferrer">Redwood forests store almost 2,600 tonnes of carbon per hectare</a><span>, their bark alone containing more carbon than any other neighboring species.</span></p><p>While the importance of trees in fighting climate change is widely accepted, not all species enjoy the same protection as California's coastal Redwoods. In 2019 the world lost the equivalent of <a href="https://www.worldwildlife.org/threats/deforestation-and-forest-degradation" target="_blank" rel="noopener noreferrer">30 soccer fields of forest cover every minute</a>, due to agricultural expansion, logging and fires, according to The Worldwide Fund for Nature (WWF).</p>Pixabay
<p>Although <a href="https://c402277.ssl.cf1.rackcdn.com/publications/1420/files/original/Deforestation_fronts_-_drivers_and_responses_in_a_changing_world_-_full_report_%281%29.pdf?1610810475" target="_blank" rel="noopener noreferrer">the rate of loss is reported to have slowed in recent years</a>, reforesting the world to help stem climate change is a massive task.</p><p><span>That's why the World Economic Forum launched the Trillion Trees Challenge (</span><a href="https://www.1t.org/" target="_blank" rel="noopener noreferrer">1t.org</a><span>) and is engaging organizations and individuals across the globe through its </span><a href="https://uplink.weforum.org/uplink/s/uplink-issue/a002o00000vOf09AAC/trillion-trees" target="_blank" rel="noopener noreferrer">Uplink innovation crowdsourcing platform</a><span> to support the project.</span></p><p>That's backed up by research led by ETH Zurich/Crowther Lab showing there's potential to restore tree coverage across 2.2 billion acres of degraded land.</p><p>"Forests are critical to the health of the planet," according to <a href="https://www.1t.org/" target="_blank" rel="noopener noreferrer">1t.org</a>. "They sequester carbon, regulate global temperatures and freshwater flows, recharge groundwater, anchor fertile soil and act as flood barriers."</p><p><em data-redactor-tag="em" data-verified="redactor">Reposted with permission from the </em><span><em data-redactor-tag="em" data-verified="redactor"><a href="https://www.weforum.org/agenda/2021/03/redwoods-store-more-co2-and-are-more-enormous-than-we-thought/" target="_blank">World Economic Forum</a>.</em></span></p>EcoWatch Daily Newsletter
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