Lakes on Greenland Ice Sheet Drain in Chain Reaction, Destabilizing Sheet and Raising Sea Levels
A research team led by the University of Cambridge found that the lakes of meltwater that form on the ice sheet in the summer drain in a chain reaction that increases the flow of the ice sheet, destabilizing it and increasing sea level rise, the University of Cambridge reported in a press release.
It had long been known that these lakes could drain quickly on an individual basis. They can last months, then drain through more than one kilometer (approximately 0.621 miles) of ice within hours.
However, this study used a combination of observation and three-dimensional modeling to show that the lakes do not drain in isolation. Instead, the melting of one lake can trigger the melting of lakes up to 80 kilometers (approximately 49.71 miles) away.
The process begins when a lake drains and the water it contained ends up on the bottom of the ice sheet. This causes the sheet to flow faster, which destabilizes it and leads to the formation of more fractures. Other lakes then drain through these new fractures in a chain reaction that can speed the flow of the ice sheet by up to 400 percent.
A model of the lake-melting chain-reaction process. Nature Communications
Researchers observed 124 lakes drain within a span of five days, and found evidence for crevices opening 135 kilometers (approximately 83.9 miles) inland from the ice sheet's edge, which is farther than thought possible.
The study therefore contradicts the findings of the Fifth Assessment Report by the Intergovernmental Panel on Climate Change, published in 2014, which held that melt water on the surface of the ice sheet did not impact its flow.
"This growing network of melt lakes, which currently extends more than 100 kilometres inland and reaches elevations as high as 2,000 metres above sea level, poses a threat for the long-term stability of the Greenland ice sheet," the study's lead author and member of Cambridge's Scott Polar Research Institute Dr. Poul Christoffersen said in the press release.
This isn't the first study in recent years to suggest the Greenland ice sheet is in more trouble than previously believed. In 2016, scientists found the ice sheet was melting 7 percent faster than they had thought.
While the Polar Portal reported that the ice sheet actually gained a small amount of mass in 2017 due to heavy winter snows and a cool summer, the National Oceanic and Atmospheric Administration calculated that the sheet could only regain the mass it has lost since 2002 after 80 years like this one.
According to Global Citizen, the ice sheet, which is seven times the size of the United Kingdom and two miles thick, is currently contributing to global sea level rise at a rate of one millimeter (approximately 0.04 inches) per year. If all the ice in the sheet were to melt, it would raise sea levels by more than 20 feet.
This is unlikely to happen any time soon, but that doesn't mean there's nothing to worry about.
"When we say the ice sheet is melting faster, no one saying it's all going to melt in next decade or the next 100 years or even the next 1,000 years but it doesn't all have to melt for more people to be in danger," Dr. Joe Cook, a glacial microbiologist at Sheffield University, told Global Citizen. "Only a small amount has to melt to threaten millions in coastal communities around world."
The growing Texas solar industry is offering a safe harbor to unemployed oil and gas professionals amidst the latest oil and gas industry bust, this one brought on by the novel coronavirus pandemic, the Houston Chronicle reports.
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>