The finding came from an international study led by the University of Alaska Fairbanks and Finnish Meteorological Institute. The study, published in the Journal of Climate, used data collected by ocean moorings in the Eurasian Basin of the Arctic Ocean from 2003-2018.

The moorings measured the heat released from the ocean interior to the upper ocean and sea ice during winter. In 2016-2018, the estimated heat flux was about 10 watts per square meter, which is enough to prevent 80-90 centimeters (almost 3 feet) of sea ice from forming each year. Previous heat flux measurements were about half of that much.

“In the past, when weighing the contribution of atmosphere and ocean to melting sea ice in the Eurasian Basin, the atmosphere led,” said Igor Polyakov, an oceanographer at UAF’s International Arctic Research Center and FMI. “Now for the first time, ocean leads. That’s a big change.”

Typically, across much of the Arctic a thick layer of cold fresher water, known as a halocline, isolates the heat associated with the intruding Atlantic water from the sea surface and from sea ice.

This new study shows that an abnormal influx of salty warm water from the Atlantic Ocean is weakening and thinning the halocline, allowing more mixing. According to the new study, warm water of Atlantic origin is now moving much closer to the surface.

“The normal position of the upper boundary of this water in this region was about 150 meters. Now this water is at 80 meters,” explained Polyakov.

A natural winter process increases this mixing. As sea water freezes, the salt is expelled from ice into the water. This brine-enriched water is heavier and sinks. In the absence of a strong halocline, the cold salty water mixes much more efficiently with the shallower, warm Atlantic water. This heat is then transferred upward to the bottom of sea ice, limiting the amount of ice that can form during winter.

“These new results show the growing and spreading influence of heat associated with Atlantic water entering the Arctic Ocean,” added Tom Rippeth, a collaborator from Bangor University. “They also suggest a new feedback mechanism is contributing to accelerating sea ice loss.”

Polyakov and his team hypothesize that the ocean’s ability to control winter ice growth creates feedback that speeds overall sea ice loss in the Arctic. In this feedback, both declining sea ice and the weakening halocline barrier cause the ocean’s interior to release heat to the surface, resulting in further sea ice loss. The mechanism augments the well-known ice-albedo feedback — which occurs when the atmosphere melts sea ice, causing open water, which in turn absorbs more heat, melting more sea ice.

When these two feedback mechanisms combine, they accelerate sea ice decline. The ocean heat feedback limits sea ice growth in winter, while the ice-albedo feedback more easily melts the thinner ice in summer.

“As they start working together, the coupling between the atmosphere, ice and ocean becomes very strong, much stronger than it was before,” said Polyakov. “Together they can maintain a very fast rate of ice melt in the Arctic.”

Polyakov and Rippeth collaborated on a second, associated study showing how this new coupling between the ocean, ice and atmosphere is responsible for stronger currents in the eastern Arctic Ocean.

According to that research, between 2004-2018 the currents in the upper 164 feet of the ocean doubled in strength. Loss of sea ice, making surface waters more susceptible to the effects of wind, appears to be one of the factors contributing to the increase.

The stronger currents create more turbulence, which increases the amount of mixing, known as shear, that occurs between surface waters and the deeper ocean. As described earlier, ocean mixing contributes to a feedback mechanism that further accelerates sea ice decline.

Accelerated currents have practical implications in the Arctic. Ship captains need accurate maps of currents for navigation. Since currents move sea ice, oil and gas extraction activities also need information about currents.

The results place the core at the younger end of an age spectrum that usually runs from about 1.3 billion to 4.5 billion years, but they also make it a good bit older than a recent estimate of only 565 million years.

What’s more, the experiments and accompanying theories help pin down the magnitude of how the core conducts heat, and the energy sources that power the planet’s geodynamo — the mechanism that sustains the Earth’s magnetic field, which keeps compasses pointing north and helps protect life from harmful cosmic rays.

“People are really curious and excited about knowing about the origin of the geodynamo, the strength of the magnetic field, because they all contribute to a planet’s habitability,” said Jung-Fu Lin, a professor at The University of Texas at Austin’s Jackson School of Geosciences who led the research.

The results were published on Aug.13 in the journal Physical Review Letters.

The Earth’s core is made mostly of iron, with the inner core being solid and the outer core being liquid. The effectiveness of the iron in transferring heat through conduction — known as thermal conductivity — is key to determining a number of other attributes about the core, including when the inner core formed.

Over the years, estimates for core age and conductivity have gone from very old and relatively low, to very young and relatively high. But these younger estimates have also created a paradox, where the core would have had to reach unrealistically high temperatures to maintain the geodynamo for billions of years before the formation of the inner core.

The new research solves that paradox by finding a solution that keeps the temperature of the core within realistic parameters. Finding that solution depended on directly measuring the conductivity of iron under corelike conditions — where pressure is greater than 1 million atmospheres and temperatures can rival those found on the surface of the sun.

The researchers achieved these conditions by squeezing laser-heated samples of iron between two diamond anvils. It wasn’t an easy feat. It took two years to get suitable results.

“We encountered many problems and failed several times, which made us frustrated, and we almost gave up,” said article co-author Youjun Zhang, an associate professor at Sichuan University in China. “With the constructive comments and encouragement by professor Jung-Fu Lin, we finally worked it out after several test runs.”

The newly measured conductivity is 30% to 50% less than the conductivity of the young core estimate, and it suggests that the geodynamo was maintained by two different energy sources and mechanisms: thermal convection and compositional convection. At first the geodynamo was maintained by thermal convection alone. Now, each mechanism plays about an equally important role.

Lin said that with this improved information on conductivity and heat transfer over time, the researchers could make a more precise estimate of the age of the inner core.

“Once you actually know how much of that heat flux from the outer core to the lower mantle, you can actually think about when did the Earth cool sufficiently to the point that the inner core starts to crystalize,” he said.

This revised age of the inner core could correlate with a spike in the strength of the Earth’s magnetic field as recorded by the arrangement of magnetic materials in rocks that were formed around this time. Together, the evidence suggests that the formation of the inner core was an essential part of creating today’s robust magnetic fields.

The National Science Foundation and the National Natural Science Foundation of China supported the research.

The trailside tracks have turned out to be even more significant than Krill first imagined. “These are by far the oldest vertebrate tracks in Grand Canyon, which is known for its abundant fossil tracks” says Rowland. “More significantly,” he added, “they are among the oldest tracks on Earth of shelled-egg-laying animals, such as reptiles, and the earliest evidence of vertebrate animals walking in sand dunes.”

The track-bearing boulder fell from a nearby cliff-exposure of the Manakacha Formation. The presence of a detailed geologic map of the strata along the Bright Angel Trail, together with previous studies of the age of the Manakacha Formation, allowed the researchers to pin down the age of the tracks quite precisely to 313 +/- 0. 5 million years.

The newly discovered tracks record the passage of two separate animals on the slope of a sand dune. Of interest to the research team is the distinct arrangement of footprints. The researchers’ reconstruction of this animal’s footfall sequence reveals a distinctive gait called a lateral-sequence walk, in which the legs on one side of the animal move in succession, the rear leg followed by the foreleg, alternating with the movement of the two legs on the opposite side. “Living species of tetrapods―dogs and cats, for example―routinely use a lateral-sequence gait when they walk slowly,” says Rowland. “The Bright Angel Trail tracks document the use of this gait very early in the history of vertebrate animals. We previously had no information about that.” Also revealed by the trackways is the earliest-known utilization of sand dunes by vertebrate animals.

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However, not all birds are the same, and not all weather events have the same impact. How do different bird species respond to extreme weather events that occur for different amounts of time, ranging from weekly events like heat waves to seasonal events like drought? And how do traits unique to different species — for example, how far they migrate or how commonly they occur — predict their vulnerability to extreme weather?

To answer these questions, ecologists would traditionally observe a small number of bird species at a few sites over a few years, and then draw general conclusions. However, Zuckerberg and UW-Madison postdoctoral researcher Jeremy Cohen, along with Daniel Fink of the Cornell Lab of Ornithology, had more ambitious goals: they looked at 109 species across eastern North America over a 15-year period, and integrated this information with fine-scale satellite temperature and precipitation data.

In a study recently published in the journal Global Change Biology, the researchers show that not all birds are equally vulnerable to the effects of extreme weather resulting from climate change. As the planet warms, some species will adapt while others may struggle without conservation measures. The results of this study could help conservationists target their efforts to vulnerable species, as well as locations where extreme weather events are predicted.

The researchers used data from eBird, a global citizen-science initiative where bird enthusiasts submit checklists of bird sightings online. These checklists include which species were seen, how many, the location and time, and other observations.

The researchers compiled more than 830,000 of these checklists and integrated each one with weather data summarized over the week, month and three months before the observation was recorded. They relied on advanced computing to manage this large amount of information.

“The study we did would not have been remotely possible without data science,” says Cohen. The emerging field of data science involves the study, development or application of methods that reveal new insights from data.

Zuckerberg points out that the combination of citizen science and data science makes research possible at a scale that was previously unimaginable for ecologists. However, citizen science has its limitations. Researchers have less control over the scientific process, and data quality can vary.

“Someone can go out for five minutes or two hours and submit eBird data. They can submit a checklist for 10 species or 40 species,” says Zuckerberg. “We’ve adopted data science methods for working with large, unstructured data sets.”

After controlling for this noisy data, the researchers observed that some species are less sensitive to extreme weather, and populations are not equally exposed to its effects because some geographic areas are warming faster than others.

When it comes to heat waves, Cohen notes, “long-distance migrants were not super affected by really hot periods. They winter in tropical environments and should be tolerant of heat.”

However, resident birds and short-distance migrants such as robins and red-winged blackbirds responded negatively to heat waves, with their numbers sometimes declining 10% to 30% over several weeks.

As for drought, commonly occurring species like crows were more resilient than rare birds, particularly if the drought was severe and long-lasting.

“Rarer species have more specialized habitat and food requirements — this is a general rule in ecology,” says Cohen. “More common species usually have more options. If habitat quality declines due to drought, a generalist can go somewhere else.”

Cohen says this is the first large-scale study, spanning half a continent, to look at how birds respond immediately after weather events. Because of the scope of the project, conservationists can better understand how many different bird species are likely to be affected by climate change, and mitigate some of the negative effects.

“If birds are truly winged sentinels of climate change, the greater likelihood of drought, flooding and extreme temperature conditions like heat waves will have significant consequences,” says Zuckerberg. “We need to think about how we help species adapt to climate extremes.”

The study was funded in part by the National Science Foundation (grants CCF-1522054, CNS-1059284 and DBI-1356308) and the UW-Madison Data Science Initiative.

Astronomers discovered planets beyond our solar system, known as exoplanets, in the 1990s. We quickly went from knowing of only our own planetary system to realizing that planets likely outnumber the hundreds of billions of stars in our galaxy. Now, a team of scientists is finding ways to improve our understanding of planet demographics by searching for rogue worlds.

“As our view of the universe has expanded, we’ve realized that our solar system may be unusual,” said Samson Johnson, a graduate student at Ohio State University in Columbus who led the research effort. “Roman will help us learn more about how we fit in the cosmic scheme of things by studying rogue planets.”

The findings, published in the Astronomical Journal, center on the Roman Space Telescope’s ability to locate and characterize isolated planets. Astronomers have only tentatively discovered a few of these nomad worlds so far because they are so difficult to detect.

Finding galactic nomads

Roman will find rogue planets by conducting a large microlensing survey. Gravitational lensing is an observational effect that occurs because the presence of mass warps the fabric of space-time. The effect is extreme around very massive objects, like black holes and entire galaxies. Even solitary planets cause a detectable degree of warping, called microlensing.

If a rogue planet aligns closely with a more distant star from our vantage point, the star’s light will bend as it travels through the curved space-time around the planet. The result is that the planet acts like a natural magnifying glass, amplifying light from the background star. Astronomers see the effect as a spike in the star’s brightness as the star and planet come into alignment. Measuring how the spike changes over time reveals clues to the rogue planet’s mass.

“The microlensing signal from a rogue planet only lasts between a few hours and a couple of days and then is gone forever,” said co-author Matthew Penny, an assistant professor of physics and astronomy at Louisiana State University in Baton Rouge. “This makes them difficult to observe from Earth, even with multiple telescopes. Roman is a game-changer for rogue planet searches.”

Microlensing offers the best way to systematically search for rogue planets — especially those with low masses. They don’t shine like stars and are often very cool objects, emitting too little heat for infrared telescopes to see. These vagabond worlds are essentially invisible, but Roman will discover them indirectly thanks to their gravitational effects on the light of more distant stars.

Lessons from cosmic castaways

Johnson and co-authors showed that Roman will be able to detect rogue planets with masses as small as Mars. Studying these planets will help narrow down competing models of planetary formation.

The planet-building process can be chaotic, since smaller objects collide with one another and sometimes stick together to form larger bodies. It’s similar to using a piece of playdough to pick up other pieces. But occasionally collisions and close encounters can be so violent that they fling a planet out of the gravitational grip of its parent star. Unless it manages to drag a moon along with it, the newly orphaned world is doomed to wander the galaxy alone.

Rogue planets may also form in isolation from clouds of gas and dust, similar to how stars grow. A small cloud of gas and dust could collapse to form a central planet instead of a star, with moons instead of planets surrounding it.

Roman will test planetary formation and evolution models that predict different numbers of these isolated worlds. Determining the abundance and masses of rogue planets will offer insight into the physics that drives their formation. The research team found that the mission will provide a rogue planet count that is at least 10 times more precise than current estimates, which range from tens of billions to trillions in our galaxy. These estimates mainly come from observations by ground-based telescopes.

Since Roman will observe above the atmosphere, nearly a million miles away from Earth in the direction opposite the Sun, it will yield far superior microlensing results. In addition to providing a sharper view, Roman’s perspective will allow it to stare at the same patch of sky continuously for months at a time. Johnson and his colleagues showed that Roman’s microlensing survey will detect hundreds of rogue planets, even though it will search only a relatively narrow strip of the galaxy.

Part of the study involved determining how to analyze the mission’s future data to obtain a more accurate census. Scientists will be able to extrapolate from Roman’s rogue planet count to estimate how common these objects are throughout the entire galaxy.

“The universe could be teeming with rogue planets and we wouldn’t even know it,” said Scott Gaudi, a professor of astronomy at Ohio State University and a co-author of the paper. “We would never find out without undertaking a thorough, space-based microlensing survey like Roman is going to do.”

The Nancy Grace Roman Space Telescope is managed at Goddard, with participation by NASA’s Jet Propulsion Laboratory and Caltech/IPAC in Pasadena, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from research institutions across the United States.