NASA MODIS: Temperature Feedback magnifying climate warming in Arctic

Mosaic of images of the Arctic by MODIS. Credit: NASA

A team of researchers with the Max Planck Institute in Germany, has found that temperature feedback in the Arctic is causing more warming in that region than sea ice albedo feedback.

In their paper published in the journal Nature Geoscience, the team describes how plugging data into a computer simulation revealed a "layered cake" atmosphere that traps heat over the polar cap.

Scientists have known for several years that temperatures in the Arctic are rising faster (due to global warming) than for the rest of the planet—for the most part, most climatologists have attributed this to sea ice albedo—a feedback system where a small rise in temperature leads to melting of ice and snow.

Less ice and snow means less heat is reflected back into space, which means more warming occurs, and so on. In this new effort, the researchers suggest that while sea ice albedo is causing temperatures to rise, it's second to temperature feedback in overall impact.

To gain a better perspective on why Arctic temperatures are increasing so much, the researchers turned to highly sophisticated and data intensive climate computer models.

Their model showed a cap of cold layered air hovering over the Arctic, holding in the heat. The researchers believe their simulation accurately portrays what actually exists in the real Arctic.

Normally, they explain, changing weather patterns (such as thunderstorms) in other parts of the world keep atmospheric air churning, which in turn allows heat closer to the ground to be moved higher, allowing some of it to escape into space.

Things are very different in the Arctic—there is very little churning, which means that warm air close to ground (just one to two kilometers thick) remains where it is, trapped by a heavy layered atmosphere.

The simulation also helps to explain why Arctic warming is more pronounced in the winter than during other seasons—even less mixing of the air in the atmosphere occurs because the air is so cold.

The team reports that their simulations show that the temperature feedback that occurs in the Arctic is causing more average temperature increase than sea ice albedo, the second most critical factor in causing warming.

They have not used their findings to try to predict what sort of overall impact increasing Arctic temperatures might have on the rest of the planet, however, if the polar cap will melt completely, or if it does, when it might occur.

More information: Arctic amplification dominated by temperature feedbacks in contemporary climate models, Nature Geoscience (2014) DOI: 10.1038/ngeo2071

Dwarf planet Makemake: Confirmation that it lacks atmosphere

Dwarf planet Makemake is about two thirds of the size of Pluto, and travels around the Sun in a distant path that lies beyond that of Pluto but closer to the Sun than Eris, the most massive known dwarf planet in the Solar System.

Previous observations of chilly Makemake have shown it to be similar to its fellow dwarf planets, leading some astronomers to expect its atmosphere, if present, to be similar to that of Pluto.

However, the new study now shows that, like Eris, Makemake is not surrounded by a significant atmosphere.

The team, led by Jose Luis Ortiz (Instituto de Astrofisica de Andalucia, CSIC, Spain), combined multiple observations using three telescopes at ESO's La Silla and Paranal observing sites in Chile - the Very Large Telescope (VLT), New Technology Telescope (NTT), and TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) - with data from other small telescopes in South America, to look at Makemake as it passed in front of a distant star.

"As Makemake passed in front of the star and blocked it out, the star disappeared and reappeared very abruptly, rather than fading and brightening gradually. This means that the little dwarf planet has no significant atmosphere," says Jose Luis Ortiz.

"It was thought that Makemake had a good chance of having developed an atmosphere - that it has no sign of one at all shows just how much we have yet to learn about these mysterious bodies. Finding out about Makemake's properties for the first time is a big step forward in our study of the select club of icy dwarf planets."

Makemake's lack of moons and its great distance from us make it difficult to study, and what little we do know about the body is only approximate.

The team's new observations add much more detail to our view of Makemake - determining its size more accurately, putting constraints on a possible atmosphere and estimating the dwarf planet's density for the first time.

They have also allowed the astronomers to measure how much of the Sun's light Makemake's surface reflects - its albedo. Makemake's albedo, at about 0.77, is comparable to that of dirty snow, higher than that of Pluto, but lower than that of Eris.

It was only possible to observe Makemake in such detail because it passed in front of a star - an event known as a stellar occultation.

These rare opportunities are allowing astronomers for the first time to find out a great deal about the sometimes tenuous and delicate atmospheres around these distant, but important, members of the Solar System, and providing very accurate information about their other properties.

Occultations are particularly uncommon in the case of Makemake, because it moves in an area of the sky with relatively few stars.

Accurately predicting and detecting these rare events is extremely difficult and the successful observation by a coordinated observing team, scattered at many sites across South America, ranks as a major achievement.

"Pluto, Eris and Makemake are among the larger examples of the numerous icy bodies orbiting far away from our Sun," says Jose Luis Ortiz.

"Our new observations have greatly improved our knowledge of one of the biggest, Makemake - we will be able to use this information as we explore the intriguing objects in this region of space further."

Jupiter's Big Moon Ganymede Albedo Mapped by Amateur Astronomer

An amateur astronomer has created the first-ever homemade brightness map of Jupiter's huge moon Ganymede in a magnificent display of how non-professional skywatchers can contribute to the field of observational astronomy.

Greek skywatcher Emmanuel Kardasis of the Hellenic Amateur Astronomy Association (HAAA) created the new Ganymede map using a common "hobby" telescope and off-the-shelf camera and computer equipment.

His map matches up well with images of Ganymede's surface taken by professionals, said officials with the European Planetary Science Congress (EPSC), which is meeting this week in Madrid.

For example, Kardasis' reflected brightness (or albedo) map identifies such Ganymede features as Phrygia Sulcus, a system of grooves and ridges thousands of miles across, and a low-lying dark area called the Nicholson region.

To create the images, Kardasis attached a camera to his telescope and recorded a video of the ice-covered Ganymede, which is the largest moon in the solar system at 3,273 miles (5,268 kilometers) across.

He picked the video's sharpest frames, then enhanced them using photo-editing software, EPSC officials said.

"Ganymede has a tiny disk as seen from Earth so was a good test for my techniques," Kardisis said in a statement.

"If the same methods were applied to other worlds, perhaps [Jupiter's] volcanic moon Io, we could capture surface fluctuations."

"Professional observatories may create better images, but they cannot monitor our rapidly and ever-changing universe."

"The equipment amateurs need to generate products like his Ganymede map is relatively easy to find" Kardasis said.

"Creating useful images of planets requires a telescope with a diameter of at least eight inches. For tiny discs, such as the moons of Jupiter, bigger is definitely better," he said.

"My Ganymede images were made using an 11-inch telescope. You also need a good motor drive on your tripod, a sensitive camera, some freely available software and lots of patience!"