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Innovation: patent applications review

Microbubbles enable super-resolution ultrasound imaging

Mayo Clinic researchers have developed systems and methods for super-resolution ultrasound imaging of microvessels (WO/2018/222724). The technique involves acquiring ultrasound data from a region-of-interest in a subject who has been administered a microbubble contrast agent. The data are acquired while the microbubbles are moving through or otherwise present in the region-of-interest, which may include microvessels or other microvasculature. Isolating, localizing, tracking and accumulating the microbubbles in the ultrasound data enables generation of super-resolution images.

Radioactive source delivers PET timing calibration

Philips has described a scheme for performing timing calibration of a PET imaging device. The approach uses a radioactive source comprising a positron-emitting radioisotope with a decay path that includes emission of two opposed 511 keV gamma rays and a cascade gamma ray at a different energy (WO/2018/202878). A timestamped detection event data set acquired from the source by the PET device is processed using energy window filtering and time window filtering. This generates a coincidence data set that includes event pairs, each consisting of two coincident 511 keV gammas, and cascade event pairs or triplets, each consisting of at least one coincident 511 keV event and a coincident cascade event at the cascade gamma ray energy. The coincidence data set is then used to generate a timing calibration, which provides offset times for the detectors of the PET imaging device.

Convolutional neural networks reduce nuclear medicine dose

A team from Stanford University has devised a method to reduce radiation dose for nuclear medicine imaging by using a convolutional network to generate a standard-dose image from a low-dose image (WO/2018/200493). The network includes N convolution neural network stages, where each stage includes M convolution layers with K x K kernels. The network extracts multi-scale and high-level features from the low-dose image to simulate a high-dose image, and adds concatenate connections to the low-dose image to preserve local information and resolution of the high-dose image. The high-dose image includes a radiotracer dose reduction factor (DRF) of one; the low-dose PET image includes a DRF of at least four.

Mesoscopic ultrasound generates brain tissue elastogram

Arizona State University has published details of a technique for creating an elastogram of brain tissue (WO/2018/227088). The elastogram is generated using mesoscopic wavelength ultrasound, composed of longitudinal waves, to produce micromechanical disturbances of brain nuclei and circuits. These tissue disturbances enable characterization of mechanical properties such as stiffness, elasticity, rigidity and viscoelasticity. The magnetic resonance elastography (MRE) system includes an MRE engine in communication with at least one transducer and an MRI device. The MRE engine controls the operation of the transducer, which emits ultrasound and receives at least one signal indicative of brain tissue displacement from the MRI device. It then generates an elastogram of the brain tissue based on the received signal(s).

Nanoparticles allow early diagnosis of Alzheimer’s disease

A team at the Chinese University of Hong Kong has created a novel nanoparticle that can cross the blood–brain barrier and bond with amyloid plaques and other related protein aggregates for detection by MRI (WO/2018/193278). The ability to image these amyloid plaques provide a non-invasive means for diagnosing Alzheimer’s disease at an early stage. According to the filing, which details the compositions and methods of making and using them, the approach employs non-toxic materials that have well established safety profiles and do not require further toxicological testing to secure regulatory approval.

Thickness measurements optimize radiography settings

To calculate the optimal exposure settings for a selected radiography exam, the acquisition geometry of the radiography system and the thickness of the patient must be known. Agfa has developed a method for accurately determining the source-image-distance (SID) and the thickness of a patient in a radiography configuration (WO/2018/184705). The SID is determined based on a method that accurately measures distances between a set of generator arrays and sensor arrays. These arrays are preferably orthogonally arranged magnetic field generators and sensors that allow distance measurement without being affected by the presence of human tissue between the generator and sensor arrays.

Lung-mimicking electrocatalyst system turns water into fuel

When we breathe, air moves through the small passage-like bronchioles of our lungs until it reaches the alveoli. These tiny sac-like structures contain a micron-thick hydrophobic epithelial membrane on the inside and a hydrophilic one on the outside. This special structure ensures that air does not directly diffuse into the bloodstream, which would create unnecessary (and harmful) bubbles, but allows for efficient two-way gas exchange between the bloodstream and the lungs. A team of researchers at Stanford University in the US has now designed a new catalytic system that works in the same way as our lungs to cycle between water and fuel via the oxygen evolution- and oxygen reduction reactions (OER and ORR). These reactions play a key role in clean energy technologies, such as fuel cells and metal-air batteries, and the new system could help make them more efficient.

“The mammalian breathing process could be mistaken as being simple since it is so natural, but it is actually one of the most sophisticated, nature-designed systems for two-way gas exchange,” explains study lead author Jun Li, who is a graduate student in Yi Cui’s group at the Department of Materials Science and Engineering at Stanford. “The alveoli contain a micron-thick membrane that repels water molecules on the inside while attracting them on the outer surface. It is this unique structure that prevents air bubbles from forming and makes air exchange highly efficient.”

“Our electrocatalytic system structurally mimics the alveolus and carries out two different processes. The first, the OER, is analogous to exhalation, in which water is split to produce oxygen and hydrogen gas (a clean fuel) by oxidizing water molecules in the anode of a battery while reducing them at the cathode. Fast gas transport helps to eliminate the energy of O₂bubble formation and this reduces the overpotential,” says Li.

“The second, the ORR, mimics the inhalation process, in which gas reactant is efficiently delivered to gas-liquid-solid contact lines for enhanced catalytic reaction and reduced gas-diffusion resistance. Here, energy is generated through a reaction that consumes oxygen.”

Pouch-like nanoporous hydrophobic PE membrane

The alveolus in the new system is a pouch-like nanoporous hydrophobic, 12-micron-thick polyethylene (PE) membrane, which is around 30 times thinner than conventional gas-diffusion electrodes. The researchers made this structure by first depositing a layer of catalysts on one side of the PE membrane. These also serve as a charge-transport layer and a hydrophilic coating. They then roll the catalyst-coated PE membrane into a pouch structure with a gas phase inside and a liquid phase outside.

Since the PE membrane is hydrophobic, it prevents water from flooding through, which allows for fast transport of gas molecules and charges – just like in mammalian alveoli. The alveolus-like PE structure creates a barrier that water cannot penetrate but is accessible for two-way gas transport. The added advantage is that it also remains hydrophobic for a substantially longer time than conventional carbon-based diffusing layers.

Record-low overpotential

During the OER, the newly formed O₂molecules quickly diffuse from the catalyst/electrolyte interface towards the gas phase without the additional energy costs of forming bubbles in the electrolyte. Again, like nature’s alveoli. Indeed, Li and colleagues say they were able to achieve a record-low overpotential of 190 mV at 10 mA/cm²using catalysts made of Au/NiFeO_x.

Improving electron transfer in enzymatic fuel cells

During the ORR, O₂gas can transport to the catalyst interface, so overcoming oxygen’s low solubility in water. “The result: around 25 times higher current densities for catalysts made from the Ag/Pt bilayer nanoparticles when compared to conventional flat structures, for example,” says Li. “This breathing mimicking design boasts efficient three-phase catalysis with a minimal catalyst thickness.”

A unique gas exchange system

“It could be easily applied to many other multi-phase catalytic systems, particularly gas evolution reactions and gas harnessing reactions, she tells Physics World. “Gas usually does not dissolve well in an aqueous electrolyte – in a two-phase reaction, for example – which limits mass transport for the reactions taking place therein. Our device is a highly efficient and unique dual direction gas exchange system at liquid-solid-gas three-phase contact lines and promotes mass transport for both gas delivery and release.”

The researchers, reporting their work in Joule 10.1016/j.joule.2018.11.015, say they will now be tuning their catalytic system to fit with different electrochemical reactions. “We also believe that the nanoPE membrane can be replaced with other nanoporous hydrophobic membranes that are stable at higher temperatures,” says Li. “Finally, the membranes themselves can be integrated with other, hydrophilic, nanoporous films (for example, cellulosic material) to allow for fast water adsorption by capillary action for continuous reaction processes and active electrocatalytic reactions at the three-phase interface.”

Scutoid cells discovered in soap bubbles

Pillar-shaped structures called scutoids have been spotted in a bubbly foam by physicists in Ireland and the UK. Their finding follows the discovery of scutoids in skin tissues in July 2018. The formation of scutoids in a simple foam suggests that physical processes are driving their creation, which could help with the development of artificially-grown tissues and organs.

Scutoids are column-like structures that are sandwiched between two surfaces. They have n sides at one surface and n-1 at the other. The name derives from their resemblance to a structure called a scutum, which appears in some insects.

Earlier this year, scientists in Spain and the US found scutoids between epithelial (skin) cells in curved tissues. It had been thought that scutoids were a biological phenomenon, but now physicists have shown that the emergence of structures can be understood using a relatively simple physical model.

Beer and sea foam

News of the scutoid discovery came to foam physicists Stefan Hutzler of Trinity College Dublin and Adil Mughal at Aberystwyth University just as they were both leaving for an annual scientific get-together in Northern Ireland.

“We meet once a year in a lovely cottage just by the sea and an adjacent pub,” says Hutzler. “After spending three days together thinking and discussing the occurrence of scutoids, while observing foam by the seashore and in pint glasses, we decided to perform simulations and experiments and look for scutoids in foam.”

“We got it cracked within a month,” he says, “including the simulations performed at Aberystwyth University and our experiments in Trinity”.

Dishwashing liquid

The team took a low-tech approach to creating scutoids by driving air from an aquarium pump into a solution made of dishwashing liquid to create evenly-sized bubbles. The bubbles were then placed between two concentric cylindrical surfaces to mimic the curved tissues in which biological scutoids were discovered.

They soon found scutoids, which the team believes formed as the bubbles sought to minimize their surface energies. This process has been recognized for more than a century as being the prime driver of foam cell formation.

To further understand this effect, physicists turned to computer simulations. These began with hexagonal cylindrical cells that were constrained by curved surfaces. Minimization of the surface energy of these cells resulted in the emergence of several stable scutoids.

Artificial organs

The usefulness of this simple foam model of scutoids must now be explored, but it could ultimately be used describe various biological systems and understand their behaviours. Indeed, knowing how scutoids emerge in complex biological tissues could lead to important insights into how artificial tissue or entire organs could be grown.

“We might get some indications what kind of cell structures could be formed during the growth of artificial organs,” says Hutzler. “We would only need the radii of the curvature and the cell size for the predictions.”

The team is now expanding the scope of the research and wants to identify the conditions and precise geometrical parameters required for scutoid formation. They also plan to study the biophysics and bioengineering aspects of scutoids.

Javier Buceta of Lehigh University, who was part of the team that discovered scutoids in skin tissue, said that his team was very excited about the Trinity-Aberystwyth study. “First, it revealed that our research was getting coverage and captured the interest of other groups working on different problems,” he told Physics World. “Secondly and more importantly, it proved that our idea about why nature decided to pack cells following this geometry was true: an energy minimization principle. In our case, we developed a biophysical model that was in agreement with experiments, but cells are way more complicated than foams and to build our model we discarded some energetic contributions under the assumption that tension was the most relevant one.”

Buceta adds, “As Hutzler and colleagues mention in their paper, this is a rough approximation and other terms can be relevant, but their experiments have shown that tension is indeed enough and that cellular packing can be explained invoking an energy minimization principle. Following these ideas, we are currently investigating more in detail these concepts of energy and forces in tissues and trying to link them with evolutionary principles.”

The study is described in Philosophical Magazine Letters.

Synthetic synapse uses light to contract artificial muscle

Synthetic optoelectronic synapse — A synthetic optoelectronic synapse between an artificial neuron and muscle. (Courtesy: Yeongjun Lee)

Researchers in Korea and the US have engineered a light-activated synthetic synapse that enables an artificial muscle to move and contract. The newly designed organic optoelectronic synapse converts light to electrical signals to enable an artificial muscle to flex and stretch (Science Advances 10.1126/sciadv.aat7387).

Mimicking human sensory and motor functions has become one of the key motivations for bio-inspired engineering, especially for developing electronic prostheses and neurorobotics. Performing human-like sensing functions, as well as processing neural signals including motor responses, are among the key tasks for an artificial sensorimotor nervous system. However, the major focus to date has been on the development of materials and tools that mimic memory properties in a human brain at the basic level. Therefore, emulation of the human neuromuscular system remains a challenge.

Stretchable optoelectronic neuromuscular system

Taking the neurorobotics field a step further, the researchers — at Seoul National University and Stanford University, led by Tae-Woo Lee and Zhenan Bao — designed a synthetic optoelectronic synapse. This sensorimotor system contains a photodetector and organic synapses that contract an artificial muscle when triggered by pulses of light. Their design is similar to optogenetic techniques used in biology, where genetically modified cells and neurons become sensitive to light to operate.

Tae-Woo Lee and Zhenan Bao — Co-senior authors Tae-Woo Lee (left) and Zhenan Bao (right).

The new design is a stretchable organic nanowire synaptic transistor (s-ONWST) that propagates optical signals and converts them into excitatory postsynaptic currents (EPSCs) that activate contraction of an artificial muscle. To achieve this design, the researchers aimed to develop a device that will be flexible, stretchable and durable under different movement conditions. Hence, they chose organic nanowires, which can achieve the flexibility of a biological neuromuscular system more easily than conventional rigid inorganic artificial synapses.

The team fabricated the polymeric organic nanowire-based artificial synapse using ion gel electrolyte and a single organic nanowire. Next, they added a photodetector to the s-ONWST and assembled the optoelectronic synapse. Upon exposure to light, the photodetector generates voltage spikes and drives the s-ONWST to emit the EPSCs.

The transistor’s ion gel-based electrochemical behaviour was confirmed through current–voltage curves. In biological synapses, neurotransmitters migrate across the synaptic cleft (the small space between the presynaptic neuron and the postsynaptic neuron) upon receiving an action potential. In a similar manner in the artificial neuromuscular system, negative presynaptic voltage spikes move anions towards the organic nanowire.

The researchers determined that their organic optoelectronic synapse has the potential to be used as an optical wireless communication method in human–machine interfaces. Their experiments showed that the s-ONWST can react to visible light displayed in patterns similar to Morse code. In other words, every single English letter elicited a distinguishable EPSC amplitude response. Other tests on the s-ONWST further confirmed that stretching the device did not result in any significant defect in its response.

Bio-inspired soft electronics can take advantage of light-interactive actuators to drive operation of sensory and motor systems. This would be achieved through the development of optical wireless communication in which undirected visible, infrared or ultraviolet light propagates a signal.

“We have demonstrated the first neurologically inspired organic optoelectronic sensorimotor synapse,” the authors claim. They are looking forward to the emergence of “a promising strategy for the development of next-generation biomimetic soft electronics, soft robotics, neurorobotics and electronic prostheses” in the near future.

Research group — Tae-Woo Lee’s research group at Seoul National University.

Robotics and self-assembly shape up

“Ultimately, machines functioning in this way could achieve dynamically changing physical structures – programmable matter – and hence would open up a whole new world of machinery,” suggest the authors of the recent Science Robotics report on robot swarm morphogenesis. The prognosis gives an impressive outlook for a swarm comprised of robots with just three functions: movement, robot-to-robot communication, and a multicolour light-emitting diode (LED) for experimental monitoring. However as is so often the case the sum is much more than the sum of its parts.

Ivica Slavkov, Daniel Carrillo-Zapata work with co-authors in Barcelona in Spain, Bristol in the UK, and Amsterdam in the Netherlands in this latest report. They design swarms of simple “kilobots” so that they can self-organize into simple patterns and shapes not by recognizing and arranging their location according to some top-level master plan, but through local interactions with nearby robots. The approach crops up at many levels in nature from the growth of bacterial colonies, networks of slime mould and alveoli in lungs, to the way fire ants construct bridges.

Although limited to simpler shapes, compared with top-down shape self-assembly there are a number of advantages to this kind of “morphogenesis”. As well as being an emergent, naturally scalable approach, the researchers describe it as “robust to failure of individual agents, and flexible, i.e., exhibiting the type of swarm intelligence seen in natural swarms.” What Slavkov, Carillo-Zapata and team highlight is that by allowing each element a higher degree of autonomy and self-regulation, swarms of self-organizing morphogenetic robots applied to, for example, building construction would be able to respond to changes in their environment and enable self-repair.

A certain degree of freedom

Autonomous self-constructing architecture may be a little way off, but the balance between freedom and control also crops up when engineering machinery with moving parts – you need to allow some freedom of mobility for the machine to function but too much makes the movement hard to govern. As a result engineers tend to favour joints or linkages – assemblies of connected rigid bodies – with just one degree of freedom.

Until recently this left a fairly limited range of linkages at their disposal but by exploring loops of twisted tetrahedra researchers have now unearthed a whole new class of “Möbius kaleidocycles” with the coveted one degree of freedom. As well as the fundamental advances the development poses for understanding the morphologies and mobility of looped linkages and direct applications in robotics, Schönke and Fried suggest the results may point to new organic chemistry.

Governing anisotropy

From tetrahedral loops to tiles, truncated tetrahedral quantum dots prove to be the sought-after building blocks of a single-component colloid that can generate quasicrystalline superlattices (QC-SLs) – a structure of layers of non-periodic but ordered material. The unusual rotational symmetry in the absence of translational periodicity found in quasicrystals has proved an intriguing field of research, earning Dan Shechtman the 2011 Nobel Prize in Chemistry for his first observation of what is now considered to be the signature quasicrystal diffraction pattern.

Computers had predicted the possible bottom-up assembly of QC-SLs generated from single-component colloidal building blocks but experimental realization has proved difficult due to the metastability and high structural complexity in these systems. Rising to the challenge, Ou Chen and colleagues at Brown University in the US, and Max Planck Institute for the Structure and Dynamics of Matter and Heinrich Pette Institute–Leibniz Institute for Experimental Virology in Germany produced truncated tetrahedral quantum dots with different surfactants on different facets. The different surfactants lead to what they describe as “anisotropic patchiness”, which provides the governing hand to coordinate the structure’s assembly. Chen and colleagues also identify a “flexible polygon tiling rule,” which drives the order in the emerging quantum dot arrangement.

“Mechanistic studies demonstrated that the anisotropic surface tethers induced enthalpic patchiness of the TTQDs [truncated tetrahedral quantum dots], which, combined with molecular microscopic environments at the assembly site, were responsible for the 10-fold QC-SL formation,” they report in Science. “Our discovery shows the possibility of creating superstructural materials, otherwise inaccessible through isotropic counterparts, from anisotropic building blocks even without the guidance of a unit cell.”

This flurry of game-changing results based on new morphologies and geometries highlights a useful maxim relevant for any assembly of functional agents. While power is nothing without control, perhaps control functions best with a certain degree of freedom.

Festive five: Physics World picks its favourite features from 2018

As 2018 draws to a close, you may have noticed us announce the Physics World Breakthrough of the Year for research into “twistronics” and the Physics World Book of the Year, which was awarded to Beyond Weird by Philip Ball.

I’m now pleased to reveal the five authors whose Physics World features we’ve picked as our favourites of 2018. We’ve published almost 80 features over the last year in our monthly magazine, focus issues, special reports and online.

But these authors’ articles have all the hallmarks of a top Physics World feature, in that they tell a good story, say something profound and are pitched at a level that you – the connossieurs of physics – will enjoy.

They are, in chronological order:

Imre Bartos, from the University of Florida in the US, for “A new cosmic messenger” from the January 2018 issue of Physics World, in which he describes the excitement surrounding the recent discovery of gravitational waves form two colliding neutron stars.

Philip Ball, science writer in London, UK, for “Is photosynthesis quantum-ish?” from the April 2018 issue of Physics World, in which he examines whether there’s something inherently quantum in how plants turn sunlight into energy.

Seth Lloyd, from the Massachusetts Institute of Technology, for “Stephen Hawking’s scientific legacy” from the May 2018 issue of Physics World, in which he recalls the immense scientific contributions of the great cosmologist, who died in March this year.

Sidney Perkowitz, Emory University in Atlanta, US, for “Time examined and time experienced” from the July 2018 issue of Physics World, in which he surveys our changing scientific and philosophical understanding of time over the centuries.

Melanie Windridge, Tokamak Energy and Imperial College London, for “Physicist on top of the world”, from the September 2018 issue of Physics World, in which she describes her summit of the world’s highest peak and explains how scientific and technological advances are helping to make the ascent less arduous.

Congratulations to all our winners – and remember, if you have an idea for a feature of your own, features editor Sarah Tesh would love to hear from you.

The science of fireworks

Fireworks have become a hallmark of celebrations around the world. In the December 2018 issue of Physics World, Pierre Thebault looks beyond the bright colours and loud bangs, to the array of scientific methods pyrotechnicians use to improve the safety, environmental impact and spectacle of fireworks. Find out more about what’s included in December’s issue of Physics World.

How to make square-shaped droplets

The shape of a liquid droplet can be controlled precisely by sandwiching it between two taut, elastic films. By varying the tension in the films, Rafael Schulman and Kari Dalnoki-Veress at McMaster University could create flat, elliptical, and almost square-shaped droplets. The experiment offers a relatively easy way to measure interfacial tension between liquids and elastic polymers and could also be used to create tuneable liquid lenses.

When a spherical liquid droplet comes into contact with a solid surface, the contact angle between the two substances can vary depending on a variety of properties, including the surface tension. The physics of this wetting process has been studied for over a century, but Schulman and Dalnoki-Veress realized that no-one had studied liquid droplets placed between two stretchable films.

To test how the contact angle affects droplet shapes in this situation, the duo designed a setup where glycerol and polyethylene glycol droplets were sandwiched between two elastic sheets, each stretchable in two orthogonal directions. Firstly, the researchers fixed one sheet to a hard surface and placed droplets of between 30-300𝜇m in diameter on top of it. They then stretched the second film equally in both directions, which caused the spherical droplets to flatten into pancake-like shapes.

Asymmetric stretching

The duo then repeated the experiment, this time stretching the top film more in one direction than the other, resulting in a surface tension that varied across the film. This time, the droplets took on elliptical shapes, with an aspect ratio that depended on the difference in tension between the two directions.

Next, the physicists detached the bottom sheet, and stretched both sheets equally in both directions. Remarkably, this caused the droplets to adopt square-like shapes, with their sides oriented along the directions of tension in the films.

In the past, values for tension at the interface between liquids and elastic polymers have been notoriously difficult to calculate. However, from their observations, Schulman and Dalnoki-Veress saw that the easily-quantifiable variations in contact angles with tension allowed for relatively easy measurements of this value for the first time.

The duo also realized that the setup could be used to create liquid lenses with highly-tuneable aspect ratios. They also tested the lenses’ ability to focus light by passing a diffracted laser beam through them. This resulted in line-shaped spots for elliptical drops, while square droplets produced cross-shaped spot patterns.

The finding could provide useful insights for optics research in the future, and shows that further research into the already well-studied field of wetting could yet uncover new physical phenomena.

The research is described in Physical Review Letters.

Brian May’s new single includes Stephen Hawking, design your own physics-themed Christmas jumper

Famous for his soaring guitar solos and long curly locks, Brian May also has a longstanding interest in space. Indeed, in 2006 he returned to Imperial College after a 30-year hiatus to complete a PhD in astrophysics.

Writing his thesis must have taken its toll on May, because he hasn’t released a single since 1998. But now May is releasing a new tune just after midnight EST on New Year’s Day from the control centre of NASA’s New Horizons space mission.

According to the NME, the single features the voice of the late Stephen Hawking and is a tribute to the NASA mission, which will reach Ultima Thule in the Kuiper Belt on 1 January.

There is still time to enter Physics World’s Christmas jumper design competition. Send in your jumper design (sweater design to those in North America) for the chance to win a copy of Stephen Hawking’s final book Brief Answers to the Big Questions. The last day for entries is 7 January 2019 and there are more details here: “Christmas competition”.

Greenland’s icecap melt picks up speed

Greenland’s icecap – the largest single store of frozen freshwater in the northern hemisphere – is melting faster than ever, according to two separate studies using two different approaches.

Surface meltwater started flowing over the surface and percolating through the ice at a greater rate in the mid-19th century and accelerated dramatically during the 20th and the first decades of the 21st century, according to a new study of ice cores taken more than 2000 metres above sea level.

And a 25-year record of European Space Agency satellite data confirms the alarming picture: the elevation of the Greenland ice sheet was changing in the mid-1990s, and the pace of thinning stepped up after 2003. Greenland’s bedrock carries enough ice to raise global sea levels by around seven metres.

“Melting of the Greenland Ice Sheet has gone into overdrive. As a result, Greenland melt is adding to sea level more than at any time in the last three and a half centuries, if not thousands of years,” said Luke Trusel, a glaciologist at Rowan University in the US.

“And increasing melt began around the same time as we started altering the atmosphere in the mid-1800s.”

His co-author Sarah Das of the Woods Hole Oceanographic Institution said: “From a historical perspective, today’s melt rates are off the charts, and this study provides the evidence.”

Snow falls on the great icecaps of the two hemispheres, freezes, melts a little in the summer and freezes again, so that – like the rings of a tree – the accumulated precipitation tells a story of successive years of climate change. The two researchers and their colleagues report in Nature that ice cores taken from the icecap between 2003 and 2015 contained enough information for them to assess annual melting rates over several centuries.

They found a clear pattern of more intense melting nearer the present, and over the last 20 years the intensity increased by between 250% and 575%, compared to the 18th century. In the last century the entire planet has warmed by around 1 °C as greenhouse gas levels in the atmosphere have risen, in response to ever greater use of fossil fuels.

The message for the future is ominous. “Rather than increasing steadily as climate warms, Greenland will melt increasingly more and more for every degree of warming,” said Trusel. “The melting and sea level rise we’ve observed will already be dwarfed by what may be expected in the future as climate continues to warm.”

Greenland has served for decades as a climate laboratory: change almost imperceptible in lower latitudes can be measured almost on a yearly basis in the high fastnesses of the island, and the Nature study is only the latest twist in a story that is already alarming.

Dangers identified

Scientists long ago took the measure of change on the ice cap, in the glaciers and at the boundary with the Atlantic, and identified the dangers of accelerated warming in the Arctic.

They monitored unexpected increases in the flow of the island’s biggest glaciers, monitored the way the island’s bedrock rose in response to an increased loss of ice, and even identified those reaches of ice that had passed the point of no return.

The Nature scientists backed up their on-the-ground observations with measurements made by satellites. And in an entirely separate study, European researchers report in the journal Earth and Planetary Science Letters that, according to their readings too, the elevation of the icecap had begun to change in ways that enabled them to measure ice loss with the decades, and a recent speed-up.

“A pattern of thinning appears to dominate a large fraction of the ice sheet margins at the beginning of the millennium, with individual outlet glaciers exhibiting large thinning rates,” said Louise Sandberg Sørenson, of the Danish National Space Institute, who led the research.

“Over the full 25-year period, the general picture shows much larger volume losses are experienced in west, north-west and south-east basins of Greenland, compared to the more steady-state situations in the colder north.”

This article first appeared at Climate News Network

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