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An artist's rendering of the asteroid impact that took place 65 million years ago and likely killed off nearly every large vertebrate species on the planet, including, many think, the dinosaurs. Don Davis/NASA

An important finding was reported last week in the same issue of Science as the new studies of Ardipithecus, and unfortunately, overshadowed by the news of the 4-million-year-old hominid.  This finding may turn out to be even more important because it relates not to the evolution of a single species, but to the recovery of life in general on Earth following one of the greatest catastrophes ever.

I’m referring to a paper by Julio Sepúlveda and others called “Rapid Resurgence of Marine Productivity After the Cretaceous-Paleogene Mass Extinction.”

Sepúlveda and colleagues examined marine sediments in Denmark that date to the period following the K-T mass extinction event. That event consisted of an impact on the Earth of a large asteroid 65 million years ago and the subsequent extinction of many species including all the dinosaurs. It is thought that there was a huge drop in the biological activity in the oceans after the event because the sun was largely blocked out, reducing photosynthesis in ocean-living algae. Without sun, the algae would have died off, and without algae, which are at the base of the oceanic food chain, other life forms in the ocean would die off or become very rare. The more widely accepted reconstructions of what happened indicate that this oceanic die-off did indeed happen, and that it took up to three million years for the ecosystems of the open ocean to recover from this impact. (Near-shore ecosystems have been thought to recover much more quickly.) The relatively lifeless post-impact open ocean is sometimes referred to as the “Stangelove ocean” in reference to the character in the apocalyptic movie “Dr. Strangelove.”

That previous research, however, was based on the examination of fossils of marine organisms including algae that leave an easily fossilized “skeleton” of silica, which indeed are sparse for a very long time after the impact. However, it is possible that certain types of organisms that do not leave behind fossils, such as cynobacteria, were abundant and would remain undetected in the fossil record.

The paper by Sepúlveda and colleagues used a different kind of evidence to look for open ocean biological activity and found it, in abundance, possibly within a century after the impact. If this proves to be true, then the darkening of the sky following the impact must have been fairly short term, and the observed long-term disruption of the ocean’s ecosystems must have a different explanation.

“Primary productivity came back quickly, at least in the environment we were studying,” according to Roger Summons, one of the paper’s authors.  “The atmosphere must have cleared up rapidly.  People will have to rethink the recovery of the ecosystems. It can’t be just [because of] the lack of food supply.”

The method this research team used was to look for isotopically distinct materials in the ocean sediments they examined, as well as molecules that could only have been formed by living things.

The sediments they looked in consist of a 37-centimeter-thick layer of clay in Denmark. Within this clay, which was deposited in relatively shallow near-shore environments, are hydrocarbon molecules produced by living organisms that are reasonably well preserved from 65 million years ago. These molecules indicate the existence of extensive open oceanic photosynthesis that would not have been possible under the “Strangelove ocean” model.

The way the analysis works can be understood this way: The ocean has a lot of dissolved carbon in it. This carbon exists in the form of more than one isotope. An isotope is a version of an element that is only a tiny bit different in its nuclear composition, and most elements lighter than Uranium have multiple non-radioactive isotopes. If there was no life in the ocean, the carbon would reach a certain equilibrium with respect to the proportion of each isotope, so sediments that included carbon would have a predictable ratio of these isotopes. (Note:  This has nothing to do with radiocarbon dating.  See this blog post for more on the potential confusion about that issue.)

Living forms use carbon, but when carbon is taken from the surrounding environment certain isotopes are incorporated into biological tissue more readily than others. Which isotopes are used and in what way by biological systems, and the exact reason for this, is complex and far beyond the scope of a mere blog post! Suffice it to say that when a geochemist looks at a sample of carbon, using very sensitive instruments, she can tell if this carbon has come from a non-biological system vs. a biological system. Beyond this, it is even possible to tell what kind of biological system is represented.

Sepúlveda’s team was able to tell that the carbon in these post-impact sediments could only have been assembled into these hydrocarbons (and other compounds) in a functioning open ocean ecosystem with plenty of algae photosynthesizing away at a pretty good clip. Since these sediments were deposited right after the impact, the “Strangelove” ocean theory, with a vast lifeless sea, is highly unlikely.

On May 29, 2006, hot mud began to erupt within the city of Sidoarjo, in eastern Java, Indonesia. The mud volcano (also known as the Lapindo mud flow, or Lusi) hasn’t stopped since then, spewing thousands of cubic feet of material every day. Nearly 2,000 acres of land have been covered with mud, burying roads, homes and factories and displacing almost 60,000 people so far. In the image above, you can see the mud contained by levees built to hold back the flow. (In this false-color image, vegetation appears red and mud is colored gray.)

Lusi’s origin was debated at first, and geologists wondered if an earthquake two days earlier 155 miles away might have triggered the event. But they determined that the eruption was actually triggered by oil and gas drilling just 650 feet from where the mud began to flow. The Indonesians, however, have ruled the incident a natural disaster and halted their criminal probe earlier this month.

NASA image created by Jesse Allen, using data from NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team.

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Venice flooding may not end with floodgates (courtesy of flickr user gwenael.piaser)

Yes, I’m being a bit melodramatic in the headline, but every time that I read about the bad things that are predicted to happen—or already are happening—due to climate change, I worry. (And if you’re about to leave a comment saying that climate change isn’t real, please read this post about weather and climate first.) In the last month, I’ve come across half a dozen stories that give me pause:

The people of Venice thought that they would have their flooding problem fixed with a new floodgate system, but they might have breathed their sighs of relief too soon. A new study in the Journal of Climate Dynamics predicts that by the end of the century, the city’s subsidence (i.e., sinking) combined with rising sea levels from climate change could increase the number of floods from four per year to between 20 and 250 per year. The floodgates alone may not be enough to protect the city, and even if they are, closing off the city from the sea would mean that pollution and untreated sewage would not be able to be flushed out as frequently. Ew.

City dwellers here in the United States have reason to worry, too. A new report from Physicians for Social Responsibility and the National Wildlife Federation warns that rising summer temperatures in urban areas (which will mean more frequent heat waves) could be particularly dangerous to children, the elderly and African-Americans, who are more likely to live in urban areas and be poor. Extreme heat can not only lead to death through heat stroke, but it also may exacerbate other problems, such as asthma.

The situation isn’t any better down on the farm. Wolfram Schlenker of Columbia University and Michael Roberts of North Carolina State University in Raleigh looked at weather patterns and crop yields from 1950 to 2005 to predict how warmer temperatures might affect corn, cotton and soybeans. They found that the amount of time spent about 84 degrees F correlated with drops in yield. Based on current climate models, corn yields could decrease by 82 percent by the end of the century if greenhouse gas emissions continue apace.

Then there’s the New York Times article about the threat of climate change to national security. “The changing global climate will pose profound strategic challenges to the United States in coming decades, raising the prospect of military intervention to deal with the effects of violent storms, drought, mass migration and pandemics, military and intelligence analysts say.” Eek.

Climate change and polar bears don't mix well (courtesy of flickr user Just Being Myself)

Those poor bears. A new analysis in the Journal of Zoology of polar bear skulls collected from 1892 to 2002 finds that the bears have shrunk by about nine percent over that time. The researchers say that stress from increased pollution and disappearing sea ice is the likely cause. As the sea ice shrinks, the bears have to spend more and more time searching for food.

And finally, the weirdest of possible outcomes from climate change: the tilt of the Earth could shift. As we learned in school, the Earth is tilted 23.5 degrees from vertical; this is why we have seasons. But that tilt can change over time. As ice melts, warmer water expands and water in general moves from one place to another—as is expected with climate change—the motion of that water an effect on the planet’s tilt. It’s a small effect—only about 1.5 centimeters per year—but combine that with the knowledge that the redistribution of the water’s mass will have an effect on the Earth’s spin. I find it a little scary that humans, through fossil fuels, can affect the world in such a way.

Death from the Skies!

How will the world end? When Hollywood answers that question, the result is often terrifying but completely unrealistic. But the realms of reality can be even scarier than fiction, as astronomer Phil Plait deftly illustrates in Death from the Skies!, which comes out in paperback this week.

Each chapter begins with a movie script-ready scenario of Armageddon. Before delving into the topics of solar flares and coronal mass ejections, for example, there comes the story of a cold winter made worse when an event—prefaced by sunspots but not yet named—knocks out power for half the planet. Without heat, thousands die, and entire countries are driven bankrupt by the catastrophe. Having hooked his reader thusly, Plait then goes on to describe in easy-to-understand language what had caused the disaster, including how we know that such things happen and whether or not we should be scared.

Topics include gamma-ray bursts, black holes and even alien attacks. And a chart near the back of the book handily sums up the risk of each event, level of damage and whether or not we could prevent such things from happening. The most likely scenario is being hit by an asteroid, though we might one day be able to prevent these strikes. Near impossible in our time, thankfully, are the deaths of the sun or the universe. Most worrisome, though, might be the supernovae, which if one occurred close enough to Earth could lead to a mass extinction.

This book should be on the shelf of every disaster flick screenwriter. Perhaps we would then get movies with plots that are even more terrifying for the possibility that they could really happen.

“The Universe is vast beyond imagining, and wields mighty forces,” Plait writes. And for the events in his book, “it’s not a matter of if, it’s a matter of when.” Scary, indeed.

Typhoon Morakot

The full impact of Typhoon Morakot, which struck Taiwan, China and the Philippines earlier this week, may not be known for days or weeks, but hundreds are missing and dozens are already confirmed dead. Morakot was only a Category 2 storm, far less powerful than storms like Katrina or Andrew that we in the United States associate with incredible damage. But this should be a reminder that though our own hurricane season has been quiet so far and may be less active than average due to El Niño, which developed in the tropical Pacific Ocean in June, those of you who live on the East Coast should still be prepared. The hurricane season’s peak is approaching; it lasts from mid-August through mid-October.

The difference in severity of a natural disaster does not always lie in the severity of the natural event. Geography matters; Morakot’s death toll will surely rise due to a massive mudslide caused by the torrential rains. However, the ability of the individual and the community to prepare for an event and deal with the aftereffects are perhaps even more important.

Katrina was an example of both the geography and preparedness problems. New Orleans’ low elevation contributed to the devastation, but inadequate levies and poverty exacerbated the situation to such a degree that the city still hasn’t fully recovered, nearly five years later. But while we can’t do much about where we live other than to leave (which you should do if told to evacuate), we can at least prepare ourselves for a potential event.

What you should do to prepare depends much on where you live, so instead I will suggest you go to the FEMA and NOAA preparedness web sites and start there. Simply having a plan will already put you steps ahead of some of your neighbors.

NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center.

A 1973 tornado in Union City, Oklahoma in an early stage of formation (Credit: NOAA)

Yesterday, the Verification Of Rotation in Tornadoes EXperiment 2 (VORTEX2) got underway—it’s the largest attempt in history to study the deadly storms, involving more than 50 scientists and 40 research vehicles. VORTEX1 in 1994 and 1995 documented the life cycle of a tornado for the first time (and partly inspired the movie Twister). VORTEX2 will build on that and seek answers to the following questions:

- How, when, and why do tornadoes form? Why some are violent and long lasting while others are weak and short lived?

- What is the structure of tornadoes? How strong are the winds near the ground? How exactly do they do damage?

- How can we learn to forecast tornadoes better? Current warnings have an only 13 minute average lead time and a 70% false alarm rate. Can we make warnings more accurate? Can we warn 30, 45, 60 minutes ahead?

One of the scientists, Josh Wurman, is blogging the project. You may recognize him from Storm Chasers on the Discovery Channel. He’s the guy watching the screens on the DOW radar truck. (That’s not a boring job; it’s the most important one. He’s the one who tells everyone in his crew where to go to catch a storm and when to leave so they won’t die.) This year, he’s got two new DOW radars, in addition to his old one, and hopes to deploy 12 tornado pods.

And it looks like the IMAX guys are back, too. They’ve spent the last two seasons of Storm Chasers trying to film the inside of a twister. I really hope that they’re successful this year—that movie is bound to be amazing.