Tag Archives: Jonathan Amos

El Nino Is Melting Antarctica Ice

Is Antarctica melting?

This may be the most important scientific question facing humanity.  If (when) the southern ice cap melts, it’s pretty much all over for human civilization.

So, there is a lot of attention to measuring and modelling Antarctica these days.


One of the outstanding questions is the effects of warmer climate. Warmer oceans and air generally mean more precipitation, which means more snow in Antarctica.  At the same time, warmer water and air melts sea ice and glaciers along coasts, which means less ice in Antarctica.  In addition, there are relatively short term changes, such as the El Nino cycles, which warm and cool in different years.

In short, there are plusses and minuses to the snow and ice every year, and Antarctica is a big place, where more than one thing happens.  What is the overall trend of the ice cover?

There is only one way to find out, and that is to actually measure the ice and snow. And the only reasonable way to measure a whole continent is with Earth observing satellites.


This winter a team of scientists working at NASA’s Jet Propulsion Lab and other institutions report on a study that combined data from four ESA satellites to create a record of the ice depth in West Antarctica for the last 23 years. These measurements are from radar on the orbital satellite, which, in combination with careful measurement of the satellite position, gives a measure of the top of the ice.

Diagram of Cryosat-2 Instruments

The research team further adjusts the measurements for atmospheric pressure and buoyancy, to derive as accurate a measure as possible for 30 x 30 km patches over the period 1994 – 2017.  These measures are correlated with other data representing the wind, ocean, and other weather.

The research finds that, over the period of the study, the ice has been steadily thinning, likely due to incursions of warmer ocean water under the ice shelf.  Accounting for the general trend, the study examined the effects of the El Nino and Southern Oscillation.  These periodic events intensify surface snow accumulation and ocean-driven basal melting.  The combined result is “an overall height increase, but net mass loss”, because the basal ice lost is denser than the fresh snow.

In El Nino years, this effect adds to the long term trend, and in El Nina years, there is a slowing of ice loss.  If such oscillations become more frequent, intense, or longer, there could be profound effects on the West Antarctic Ice.

The researchers note that these multi year trends can only be observed by continuous satellite coverage, i.e., a series of missions lasting decades.  Unfortunately, the US has dropped its coverage, and ESA’s Cryosat-2 will end in a couple of years.  We are going blind to what is happening in this crucial part of the world.


  1. Jonathan Amos, El Nino’s long reach to Antarctic ice, in BBC News – Science. 2018. http://www.bbc.com/news/science-environment-42614412
  2. F. S. Paolo., L. Padman, H. A. Fricker, S. Adusumilli, S. Howard, and M. R. Siegfried, Response of Pacific-sector Antarctic ice shelves to the El Niño/Southern Oscillation. Nature Geoscience, 2018/01/08 2018. https://doi.org/10.1038/s41561-017-0033-0

 

Space Saturday

 

New Studies About The Chicxulub Asteroid Impact

As everyone knows, there was a large impact at what is now the Gulf of Mexico (the Chicxulub impact) at the exact time that the non-avian dinosaurs died out .  What we don’t really know, though, is how such an impact could wipe out so many species around the globe. It was a big hit for sure, but not necessarily that big.   And, don’t forget that the avian dinosaurs and lots of other species did survive.

The outer rim (white arc) of the crater lies under the Yucatan Peninsula itself, but the inner peak ring is best accessed offshore. Image credit: NASA

There are various ideas about what might have happened. Perhaps the body was a comet, with a lot of gook in the slush. Perhaps the dinosaurs were on the edge of extinction anyway, and the impact was a coincidence that finished them off.  Perhaps there were fires and volcanoes, that created a ‘nuclear winter’ for a century or more. (There is a layer of soot, indicating something like that.)

This year there have been a series of detailed analyses of the Chicxulub Impact Event (and wouldn’t that be a great name for a band!). Much of the new analysis comes from a drilling expedition sponsored by ECORD, the European Consortium for Ocean Research Drilling, Expedition 364 Chicxulub K-Pg Impact Crater“.  (There is no substitute for actual field research, no?)

 The impact was in shallow water, and therefore gouged out a huge amount of the sea floor, which filled the atmosphere with dust [2]. This could have released hundreds of gigatons of CO2 and other chemicals, which could have caused decades of cooling and even longer lasting acidification of the oceans  [3].

This fall, a Japanese team suggested that the area of the impact had a relatively high concentration of hydrocarbons in the rock, resulting in an especially large fireball and huge amounts of soot in the atmosphere [5].

And so on.

I’m no expert on geology or climate modelling, so I can’t really dissect these ideas in detail.

There doesn’t seem to be much disagreement that there was a big boom, with tsunamis and huge forest fires, and very probably earthquakes and volcanoes.  (The Earth ‘rang like a bell’ as one geologist told me.)  For decades after the hit, it looks like there was global cooling and other climate changes—a ‘nuclear winter’ scenario, which killed plants and land animals, and profoundly changed life in the oceans.

It’s clear enough that a Chicxulub scale impact is very bad news for a planet.

But it’s still not clear why the dinosaurs were wiped out everywhere, while plenty of other species survived, including ancestors of birds, frogs, fish, and mammals which lived side-by-side with dinosaurs.

But these new and more detailed studies are giving us a lot to work with.  Combined with more and more fossil evidence, we may be able to come up with some ideas about what combination of luck, geography, physiology, and who knows what may have influenced who died out and who survived Chicxulub.


  1. Jonathan Amos, Asteroid impact plunged dinosaurs into catastrophic ‘winter’, in BBC News – Science & Environment. 2017. http://www.bbc.com/news/science-environment-41825471
  2. Jonathan Amos, Dinosaur asteroid hit ‘worst possible place’, in BBC News – Science and Environment. 2017. http://www.bbc.com/news/science-environment-39922998
  3. Natalia Artemieva, Joanna Morgan, and Expedition 364 Science Party, Quantifying the Release of Climate-Active Gases by Large Meteorite Impacts With a Case Study of Chicxulub. Geophysical Research Letters, 44 (20):10,180-10,188, 2017. http://dx.doi.org/10.1002/2017GL074879
  4. Julia Brugger, Georg Feulner, and Stefan Petri, Baby, it’s cold outside: Climate model simulations of the effects of the asteroid impact at the end of the Cretaceous. Geophysical Research Letters, 44 (1):419-427, 2017. http://dx.doi.org/10.1002/2016GL072241
  5. Kunio Kaiho and Naga Oshima, Site of asteroid impact changed the history of life on Earth: the low probability of mass extinction. Scientific Reports, 7 (1):14855, 2017/11/09 2017. https://doi.org/10.1038/s41598-017-14199-x

 

PS.  Some great names for bands:

Chicxulub
The Chicxulub Event
We Are Children of Chicxulub
Thanks to Chicxulub
Brought to You By Chicxulub

 

 

 

Antarctic Surface Under the Ice

In a valuable companion to research on the heat flux under Antarctica, a team of scientist from Edinburgh published new maps of the rocks under an important area of Antarctica.

The research group assembled a higher resolution map of the rock underneath the Pine Island Glacier in West Antarctica [2]. This is, of course, critical information for understanding and predicting the flow of the ice.

This region is particularly important because the glacier has been thinning and flowing into the sea rather rapidly over the past 50 years, contributing 5-10% of global sea rise observed. Thus, the speed of this process has an important impact on projections of sea level rise.

“The retreating Pine Island Glacier (PIG), West Antarctica, presently contributes ~5–10% of global sea-level rise. PIG’s retreat rate has increased in recent decades with associated thinning migrating upstream into tributaries feeding the main glacier trunk.”

The study used ice-penetrating radar to measure the rock under more than a kilometer of ice. The radar was dragged across the ice surface, collecting data in 40 x 100 m patches.

The findings show a remarkably varied and mountainous surface under the ice. This means that there is quite a lot of friction, which will slow the ice flow in many places. These findings will provide much better parameters to computational models of this glacier.

High-resolution images of the bed across Pine Island Glacier. a Location and context. In b, the colourmap shows regional bed topography from Bedmap223, the black line is the ice divide, the white line is the grounding line51, and high-resolution survey patches are shown as black rectangles. Locations of offshore bathymetry shown in Fig. 2c, f are marked. c uses the same schema but demarcating survey patches with white rectangles, labelled by season of data acquisition (2007/08, 2010/11 and ‘iSTAR’ = 2013/14) and an end label denoting the location (where ‘tr’ = trunk; ‘it’ = intertributary and ‘t1, t5…’ denotes tributaries numbered after ref. 52. Surface ice velocities53 contoured at 100-m intervals are also shown. d–l Perspective views of the bed beneath Pine Island Glacier, together with parameters of ice flow. Vertical exaggeration in all images = 10. τ b and U b are the mean basal shear stress (kPa) and mean basal ice velocity (m a−1) from model inversion37; P r is the measured upstream propagation rate of ice thinning per ice-stream tributary from 1992 to 2015 using a thinning/non-thinning threshold of 1.0 m a−1 6 and β is the inverted basal traction coefficient equal to τ b/U b

 

The detailed information from this study required close up, on site measurements. Perhaps it would be possible to get similar data from aircraft or spacecraft, though I suspect it would be difficult. Of course, the topographical information from this study will be combined with long term satellite observations of the air, ice, and sea, to get a more complete picture of what is happening.

It is interesting to note that despite the high friction underneath that we now know about, this glacier has been absolutely cruising retreating at rapid pace. How fast would it be melting if it weren’t sliding over the teeth of a mountain range? Is the rugged terrain under the ice helping to preserve the ice cap as the air and sea warm up?

This detailed study covers only one small patch of the Antarctic coast. It will be interesting to see the results of similar studies on other glaciers, as are planned.


  1. Jonathan Amos, Antarctic glacier’s rough belly exposed, in BBC News – Science & Environment. 2017. http://www.bbc.com/news/science-environment-42052072
  2. Robert G. Bingham, David G. Vaughan, Edward C. King, Damon Davies, Stephen L. Cornford, Andrew M. Smith, Robert J. Arthern, Alex M. Brisbourne, Jan De Rydt, Alastair G. C. Graham, Matteo Spagnolo, Oliver J. Marsh, and David E. Shean, Diverse landscapes beneath Pine Island Glacier influence ice flow. Nature Communications, 8 (1):1618, 2017/11/20 2017. https://doi.org/10.1038/s41467-017-01597-y

Antarctica Heat Flux Map

One of the most important scientific questions of the early twenty first century is, “what’s going on in Antarctica?”

Antarctica is a the largest reserve of ice on the planet, and when (not if) the ice melts, it will raise sea levels by tens of meters. Glub.  (See a new NASA simulation of the effects of the melting ice.)

Just how fast is the ice melting?

This is a complex question to answer. The ice caps are gigantic (miles deep at places), and warmed by the air above and the Earth and sea underneath. Warmer air and water melt the ice, but may produce more new snow. There are liquid rivers and lakes under the ice which erode and melt from underneath. In some places glacier of ice are flowing down to the sea, where they will break up and melt.

It’s complicated.

This week a team of British researchers published a map that reflects an important piece of the picture: the heat flux under the ice [3]. This is the heat coming from the Earth’s interior, which they show is quite variable across the continent.

Hotspots are located under West Antarctica; in contrast, the East is broadly relatively cold. British Antarctic Survey.

The study used several measures of the magnetic properties of the rock under the Antarctic ice, including surface, air craft, and satellite surveys. Molten rock loses its magnetic field at a specific temperature, so the magnetic measurements can show where the rock cools below this limit. This can be used to infer the temperature at various depths below the surface.

The resulting map shows considerable variation across the continent. The warmest locations will presumably tend to melt more than cooler places (on the underside of the ice).

One interesting point from the map is that West Antarctica is melting faster than other areas, but the heat flux from the Earth is low. This suggests that the melting is due to warmer seas and ice flows, with little contribution from geothermal heat.

This dataset will contribute to many studies of the Antarctic ice. (It will be literally the foundation for many simulations.)


  1. Jonathan Amos, Antarctica’s warm underbelly revealed, in BBC News – Science & Environment. 2017. http://www.bbc.com/news/science-environment-41972297
  2. Eric Larour, Erik R. Ivins, and Surendra Adhikari, Should coastal planners have concern over where land ice is melting? Science Advances, 3 (11) 2017. http://advances.sciencemag.org/content/3/11/e1700537.full

Yasmina M. Martos, Manuel Catalan, Tom A. Jordan, Alexander Golynsky, Dmitry Golynsky, Graeme Eagles, and David G. Vaughan, Heat flux distribution of Antarctica unveiled. Geophysical Research Letters:n/a-n/a, http://dx.doi.org/10.1002/2017GL075609

 

A Big Hole Inside the Great Pyramid

Pretty much everyone has heard that Scan Pyramids Mission has detected a large void in Kufru’s Great Pyramid [2].

Whoa! Using cosmic radiation scanning a pyramid! That’s heavy, man!

The 4,500 year old pyramid is one of the oldest and largest structures ever constructed by humans, and there is much we don’t know about this artificial mountain.

For one thing, it isn’t easy to know what lies inside a million tons of rock.

The SPM used muon radiography to image the interior of the pyramid. This is a pretty cool technique, using muons that are generated by cosmic rays hitting the Earth’s atmosphere. These tiny particles shoot through the air, water, and stone at near the speed of light, but they are absorbed and scattered by matter. So, dense stone will block more muons that air, revealing a silhouette of the internal structure.

Basically, a detector is set in place to count muons coming down from the sky, through the pyramid and hitting the device. There are zillions of muons passing all the time (something like 10,000 per square meter every minute), but they rarely interact so it takes a while to accumulate a clear picture. The measurements took a couple of years, sitting there catching muons. (There is some clever analysis required to interpret the muon counts – see the paper [2].)

Their initial observations detected the known chambers, and also suggested an unknown large low-density cavity above and parallel to the Grand Gallery. The team confirmed this finding with two other instruments.

The conclusion is that there is something above the Grand Gallery.

The researchers are careful to call it a “cavity”, not a chamber. There are several cavities known in other parts of the pyramid, likely left by the builders to reduce the pressure on the internal chambers. It is quite possible that this newly found cavity has a similar origin. (It is located above the very large Grand Gallery, which must surely be one of the most vulnerable structures inside the pyramid.)

On the other hand, it certainly seems large enough to be a new chamber, and if it is, there could be unprecedented artifacts hidden there—for more than 4,000 years.

The investigators are working on ideas for how to explore the chamber. An initial concept is to drill a small (3 cm) hole, and slip in tiny robots to look around.  Maybe tiny UAVs, assuming the chamber is not filled with sand.

Keewwl!


  1. Jonathan Amos, ‘Big void’ identified in Khufu’s Great Pyramid at Giza, in BBC News -Science & Environment. 2017. http://www.bbc.com/news/science-environment-41845445
  2. Kunihiro Morishima, Mitsuaki Kuno, Akira Nishio, Nobuko Kitagawa, Yuta Manabe, Masaki Moto, Fumihiko Takasaki, Hirofumi Fujii, Kotaro Satoh, Hideyo Kodama, Kohei Hayashi, Shigeru Odaka, Sébastien Procureur, David Attié, Simon Bouteille, Denis Calvet, Christopher Filosa, Patrick Magnier, Irakli Mandjavidze, Marc Riallot, Benoit Marini, Pierre Gable, Yoshikatsu Date, Makiko Sugiura, Yasser Elshayeb, Tamer Elnady, Mustapha Ezzy, Emmanuel Guerriero, Vincent Steiger, Nicolas Serikoff, Jean-Baptiste Mouret, Bernard Charlès, Hany Helal, and Mehdi Tayoubi, Discovery of a big void in Khufu’s Pyramid by observation of cosmic-ray muons. 11/02/online 2017. http://dx.doi.org/10.1038/nature24647

PS.  Wouldn’t  “Sitting there catching muons” be a good name for a band?

 

Robots on Enceladus!

In the last two decades, we have established that this solar system is awash in water, albeit mostly dirty ice. That’s good news for our 98%-water species, at least in the very long term. Whatever else, we shouldn’t die out of thirst.

Even more interesting are the “ocean worlds“, icy moons of Neptune and Saturn (and, who knows, outer planets such as Pluto and Uranus), which probably have a liquid ocean underneath a thick crust of ice.

As I have noted earlier, ESA and NASA are gearing up to explore these worlds, because we just have to.  A prime target is the large moon Europa, which has a fissured icy crust and, most likely, a watery ocean below.

This week Waite, J. Hunter and colleagues report on yet another moon, Enceladus, which also has an icy crust ovre a liquid ocean. Enceladus also has active volcanoes !spewing water vapor. Whoa!

Enceladus is also notable because the Cassini spacecraft actually visited and swooped through one of the volcanic plumes to take a sample.

As Waite et al report, this sample contains water with traces of several other species, including H2. (See [2] for the details of this non-trivial measurement, a billion KM from home.) The researchers are particularly interest in H2, because they theorize that it is generated by “ongoing hydrothermal reactions of rock containing reduced minerals and organic materials.” They also calculate that this indicates “thermodynamic disequilibrium that favors the formation of methane from CO2 in Enceladus’ ocean “ (p. 155)

The thermodynamics and Hydrogen are both highly favorable for microbes, so these findings suggest that the ocean is “habitable”. This makes Enceladus a tempting target for a landing mission.

“We’re pretty darn sure that the internal ocean of Enceladus is habitable and we need to go back and investigate it further,” said Cassini scientist Dr Hunter Waite from the Southwest Research Institute in San Antonio, Texas.”  (quoted in [1])

So now we have at least two high priority “ocean worlds” that we should must visit.

The good news is that the gear being developed will work for missions to either or both Enceladus or Europa.

It is difficult to be optimistic about the prospects for government funding for such missions (unless someone’s family can make a bundle off the “deal”).

But, why aren’t the Silicon Valley hobbyists all over this stuff? This is way more interesting than sending rich tourists into low Earth orbit, and probably cheaper, too.

So let’s all raise a glass to my new favorite, “Robots on Enceladus!”

Suck on that, Europa.


  1. Jonathan Amos, Saturn moon ‘able to support life’. BBC News – Science & Environment.April 13 2017, http://www.bbc.co.uk/news/science-environment-39592059
  2. J. Hunter, Waite, Christopher R. Glein, Rebecca S. Perryman, Ben D. Teolis, Brian A. Magee, Greg Miller, Jacob Grimes, Mark E. Perry, Kelly E. Miller, Alexis Bouquet, Jonathan I. Lunine, Tim Brockwell, and Scott J. Bolton, Cassini finds molecular hydrogen in the Enceladus plume: Evidence for hydrothermal processes. Science, 356 (6334):155-159, 2017. http://science.sciencemag.org/content/356/6334/155

 

Space Saturday

Evidence of Water Volcanoes on Europa

While waiting for pictures from Rosetta’s last dive, and also waiting for Juno’s next pass at Jupiter, we see more indications of how cool Jupiter’s moon Europa is.

William Sparks and colleagues (including Melissa McGrath of The SETI Institute, no relation so far as I know) published a study using the Hubble Space Telescope to detect evidence of water plumes shooting out from Europa [1].

Such plumes of water have been observed at Saturn’s moon Enceladus, and there is strong reason to think that Europa has a liquid water ocean under the frozen surface. So this would not be unbelievable.

The new study stretches the limits of the Hubble, identifying smudges that could be water plumes. Other spectroscopic studies have detected Hydrogen and Oxygen in these regions, supporting the notion that there might be water there. Suggestive, but hardly conclusive or very detailed evidence.

The possibility of water plumes high above the surface is particularly interesting because Europa’s ocean is one of the places in our solar system that might support life. A mission to that ocean will be really, really difficult, but maybe we can orbit or land on the surface to sample from these plumes. This could tell us quite a bit about what is down below, even if we can’t visit yet.

Both NASA an ESA are planning possible missions to fly by Europa in the next decade. Clearly, investigating water jets, if they can be found, will be a high priority.

Cool!


  1. W. B. Sparks, K. P. Hand, M. A. McGrath, E. Bergeron, M. Cracraft, and S. E. Deustua, Probing for Evidence of Plumes on Europa with HST/STIS. The Astrophysical Journal, 829 (2):121, 2016. http://stacks.iop.org/0004-637X/829/i=2/a=121

 

Space Saturday