April 18, 2013
If you weren’t on the East Coast during Hurricane Sandy, you likely experienced the disaster through electronic means: TV, radio, the internet or phone calls. As people across the country tracked the storm by listening to information broadcast through electromagnetic waves, a different kind of wave, produced by the storm itself, was traveling beneath their feet.
Keith Koper and Oner Sufri, a pair of geologists at the University of Utah, recently determined that the crashing of massive waves against Long Island, New York and New Jersey—as well as waves hitting each other offshore—generated measurable seismic waves across much of the U.S., as far away as Seattle. As Sufri will explain in presenting the team’s preliminary findings today during the Seismological Society of America‘s annual meeting, they analyzed data from a nationwide network of seismometers to track microseisms, faint tremors that spread through the earth as a result of the storm waves’ force.
The team constructed a video (below) of the readings coming from 428 seismometers over the course of a few days before and after the storm hit. Initially, as it traveled up roughly parallel to the East Coast , readings remained relatively stable. Then, “as the storm turned west-northwest,” Sufri said in a press statement, “the seismometers lit up.” Skip to about 40 seconds into the video to see the most dramatic seismic shift as the storm hooks toward shore:
The microseisms shown in the video differ from the waves generated by earthquakes. The latter arrive suddenly, in distinct waves, while the microseisms that resulted from Sandy arrived continuously over time, more like a subtle background vibration. That makes converting these waves to the moment magnitude scale used to measure earthquakes somewhat complicated, but Koper says that if the energy from these microseisms was compressed into a single wave, it would register as a 2 or 3 on the scale, comparable to a minor earthquake that can be felt by a few people but causes no damage to buildings.
The seismic activity peaked when Sandy changed direction, the researchers say, triggering a sudden increase in the number of waves running into each other offshore. These created massive standing waves, which sent significant amounts of pressure into the seafloor bottom, shaking the ground.
It’s not uncommon for events other than earthquakes to generate seismic waves—Hurricane Katrina produced shaking that was felt in California, landslides are known to have distinct seismic signatures and the meteor that crashed in Russia in February produced waves as well. One of the reasons the readings from Sandy scientifically interesting, though, is the potential that this type of analysis could someday be used to track a storm in real-time, as a supplement to satellite data.
That possibility is enabled by the fact that a seismometer detects seismic motion in three directions: vertical (up-and-down shaking) as well as North-South and East-West movement. So, for example, if most of the shaking detected by a seismometer in one location is oriented North-South, it indicates that the source of the seismic energy (in this case, a storm) is located either North or South of the device, rather than East or West.
A nationwide network of seismometers—such as Earthscope, the system that was used for this research and is currently still being expanded—could eventually provide the capacity to pinpoint the center of a storm. “If you have enough seismometers, you can get enough data to get arrows to point at the source,” Koper said.
Satellites, of course, can already locate a hurricane’s eye and limbs. But locating the energetic center of the storm and combining it with satellite observations of the storm’s extent could eventually enable scientists to measure the energy being released by a hurricane in real-time, as the storm evolves. Currently, the Saffir-Simpson scale is used to quantify hurricanes, but there are several criticisms of it—it’s solely based on wind speed, so it overlooks the overall size of a storm and the amount of precipitation in produces. Including the raw seismic energy released by a storm could be a way of improving future hurricane classification schemes.
The prospect of seismometers (instruments typically used to detect earthquakes) being employed to supplement satellites in tracking storms is also interesting because of a recent trend in the exact opposite direction. Last month, a satellite data was used for the first time to detect an earthquake by picking up extremely low pitched sound waves that traveled from the epicenter through outer space. The fields of meteorology and geology, it seems, are quickly coming together, reflecting the real-world interaction between the Earth and the atmosphere that surrounds it.
December 14, 2012
The year 2012 was a major one for science. We saw scientists develop a new type of drug to combat HIV, figure out how to store digital data in DNA—fitting an astonishing 700 terabytes of information into a single gram of it—and even invent a coating for the inside of condiment bottles that could eliminate our stuck-ketchup-headaches once and for all (though, admittedly, this one is a little less groundbreaking than the others). Yet a few milestones in particular—discoveries, technological feats, realizations, and inventions—stand out:
1. The Higgs Boson: The landmark discovery by the European Organisation for Nuclear Research (CERN) of the once-mythical particle might be the most significant scientific discovery of our lifetimes, but it’s also one of the most surprising. Stephen Hawking, the Einstein of our time, famously bet Michigan physicist Gordon Kane $100 that it would never be found.
In an interview with The Atlantic, physicist Lawrence Krauss explained why so many experts had agreed with Hawking, arguing that the existence of the Higgs—a particle (and associated field) that makes certain types of elementary particles behave as though they had mass—was just too convenient, as it was originally posited simply to explain away an apparent difficulty in an otherwise appealing theory in theoretical physics.
The theory seeks to unite all physical forces under the same set of rules. But how can electromagnetic forces–governed by massless photons–fit under the same theoretical umbrella as the weak force, which is governed by bosons with discernible mass that control radioactive decay? Efforts to answer this conundrum gave birth to the Higgs boson. Krauss noted,”It seemed too easy…It seemed to me that introducing an invisible field to explain stuff is more like religion than science…Great, I invented invisible hobgoblins to make things right.”
Incredibly, in this case, it turned out the hobgoblins were real.
2. Earth-Like Planets: 2012 featured a ton of exoplanet discoveries, but the sighting of HD 40307g was without a doubt the most unexpected and exciting. The planet, bigger than earth but not so large as to be a gas giant, seems to orbit in its sun’s “goldilocks zone” (not too hot and not too cold), making it potentially capable of hosting liquid water, considered a prerequisite for life as we know it.
Even better, it’s just 42 light-years away: distant by human standards, but fairly close by compared many of the astronomical objects, making future projects to observe the planet much more feasible.
3. Curiosity Reaches Mars: Okay, the mission itself wasn’t too surprising—it’s been in the works since 2004—but what was so astonishing was the sudden surge of public interest in the rover and in space exploration as a whole. For decades following the manned Apollo missions of the 1960s and 70s, general enthusiasm for space science had slowly ebbed. After Curiosity’s successful landing, though, it surged. Among other things, video of NASA engineers celebrating the feat went viral and the official Curiosity twitter account garnered some 1.2 million followers.
People are so interested in Curiosity‘s exploits, in fact, that even an engineer’s throwaway line about “a discovery for the history books” pumped up expectations so much that we were bound to be disappointed by the actual finding: that early Martian soil samples seem to be representative of what we know of the planet as a whole, and that its chemistry is complex enough to have potentially once supported life. Bigger news might come over the next few years, but as project scientist John Grotzinger said, “Curiosity’s middle name is patience.”
4. Climate Change Is Even Worse Than We Thought: After decades of warnings from scientists that our greenhouse gas emissions will soon wreak havoc with the climate, we’re now starting to see the consequences—and they sure aren’t pretty. As a whole, experts are saying that the even the most frightening climate scenarios have proved to be too conservative in their analysis of how rising carbon dioxide concentrations will alter precipitation patterns, drive ocean acidification, lead to more powerful storms and, in general, make most parts of the planet grow warmer.
One silver lining might be that the public is now starting to acknowledge climate change as a present-day problem, rather than a hypothetical trend that could take effect in the future. Sadly, this has come only after record-breaking heat waves, droughts and the tragic impacts of Hurricane Sandy. Although the most recent international climate talks in Doha accomplished little, there are hopes that this shift in opinion could lead to a long-awaited change in policy sometime soon.
5. A New Way to Desalinate Seawater: With world populations expected to keep growing and potable water projected to grow more scarce over the coming century, a practical and cheap means of desalinating sea water is one of materials science’s holy grails. In July, MIT researchers announced the development of a new method of desalinization using one-atom-thick sheets of graphene, a pure carbon substance. Their method could be far cheaper and less energy-intensive than existing systems—potentially providing a way to solve many of the world’s water problems once and for all.
October 29, 2012
Hurricane Sandy has collided with a cold front to form a “Frankenstorm,” bringing extreme weather to the East Coast. Experts predict that the storm will cause billions of dollars in damages and could cause as many as 10 million people to lose power. This historically unprecedented weather event brings to mind a troubling question: Is the storm a natural occurrence or a consequence of human-driven climate change?
The answer—as often happens in science—is more complicated than a simple yes or no. For starters, there’s the distinction between weather and climate. As my colleague Sarah Zielinski wrote here in 2009, “Weather is a data point. Climate is a collection of data.” Science tells us that increasing concentrations of greenhouse gases will doubtlessly change the climate, but linking that overall shift to any one weather event is far less certain.
Nevertheless, climate models do predict that on the whole, cyclones (a category that includes hurricanes, typhoons and other extreme storms, named depending on their location) will become more frequent and intense as the climate changes. The reason is that, as noted in a 2010 Nature Geoscience study, warmer oceans cause more evaporation and precipitation, theoretically leading to more frequent powerful storms like Sandy.
As Bill McKibben writes at The Daily Beast, “when that ocean is hot—and at the moment sea surface temperatures off the Northeast are five degrees higher than normal—a storm like Sandy can lurch north longer and stronger, drawing huge quantities of moisture into its clouds, and then dumping them ashore.” A study published earlier this month in Proceedings of the National Academy of Sciences found a strong positive association between warmer years and storm activity in the 20th century, while the Nature Geoscience study noted that the latest models indicate that by 2100, tropical cyclones (including hurricanes) will occur 6 to 34 percent more frequently.
However, it’s important to note that these predictions are made with less confidence than many others dealing with the climate’s future. As Adam Frank writes at NPR, these types of long-term climate forecasts are arranged in a confidence hierarchy. Climate models allow us to be most certain, for example, that global average temperatures will increase and extreme heat events will become more frequent.
The amount of confidence that can be assigned to the prediction of increased cyclones and hurricanes over time is lower. As an IPCC special report on extreme weather events notes, “There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities.”
The reason for this reduced amount of confidence is partly the fact that storm formation is far more complicated than the simpler physics of greenhouse gases trapping radiation and causing overall warming. Additionally, since cyclones occur irregularly—and there is limited historical data on their frequency and magnitude prior to the satellite era—the degree to which their formation can be linked to climate change is restricted.
As Andrew Revkin points out at the New York Times’ Dot Earth blog, the overall scientific picture is simply more complex than advocates for action on climate change might prefer. He cites a 2002 Nature study [PDF] that notes:
Climate models suggest that human activities, specifically the emission of atmospheric greenhouse gases, may lead to increases in the frequency of severe storms in certain regions of the Northern Hemisphere. However, the existence of natural variability in storminess confounds reliable detection of anthropogenic effects.
Put most bluntly, this storm will bring terrible consequences to millions of East Coast residents, and we have many compelling reasons to limit anthropogenic climate change to whatever degree possible before it’s too late. But it’s scientifically disingenuous—even for those of us who are most desperate to convince others of the seriousness of the threat—to explicitly link this one weather event to the overall experiment we’re conducting on the planet’s atmosphere.
September 2, 2010
The U.S. East Coast is likely to miss out on most of the destructive forces of Hurricanes Danielle and Earl this week, with both just skimming by off the coast. But a miss on land doesn’t mean that the storms have no effect. In fact, they’ve both brought powerful waves and, more worrisome, rip currents. This past weekend, lifeguards rescued 250 people from the killer currents. One man in Ocean City, Maryland was swept out to sea and never found.
Rip currents—a.k.a. rip tides—can form anywhere there are waves, including on the shores of the Great Lakes. Around 100 people die every year after being caught in these currents. They quickly channel water, and anyone caught in the current, away from shore. They’re dangerous not because they pull people under (they’re only surface currents) but because they usually catch people unaware; swimmers don’t notice the rip current in the heavy surf.
The rip currents form because of complex interactions between incoming waves, currents and bathymetry (the structure of the ocean bottom). The National Weather Service explains the basic mechanics:
- Waves break on the sand bars before they break in the channel area.
- Wave breaking causes an increase in water level over the bars relative to the channel level.
- A pressure gradient is created due to the higher water level over the bars.
- This pressure gradient drives a current alongshore (the feeder current).
- The longshore currents converge and turn seaward, flowing through the low area or channel between the sand bars.
Your best strategy for dealing with a rip current is simply to avoid them and if you don’t know how to swim, to stay completely out of the water. But if you find yourself being dragged out to sea, don’t panic and don’t try to fight the current and swim back to shore. You’ll tire yourself out. Instead, swim parallel to the shore to get out of the current and then head back to the sand. If you can’t manage that, signal to a lifeguard that you need help and concentrate on staying afloat.
June 4, 2010
These are storms that go by many names. Scientists call them “tropical cyclones,” but they are also known as “typhoons,” “severe cyclonic storms” and, of course, “hurricanes.” The storm in the image above is Tropical Cyclone Phet, which earlier this week grazed the coast of Oman as it headed towards Pakistan and India. In the North Indian Ocean, the tropical cyclone season lasts from April through December, though storms are rare—only four to six form on average there each year.
The North Atlantic hurricane season—the one you’re probably more familiar with—is far more active (an average of 11 storms per year), and this year NOAA has predicted 14 to 23 named storms, with three to seven hurricanes of category 3 strength or greater. The El Niño in the eastern Pacific has dissipated and there are record warm temperatures in the Atlantic right now, making favorable conditions for these powerful storms. Hurricane season started June 1 and lasts through November. If you live anywhere along the U.S. East or Gulf Coasts, you probably should make some plans for what to do if one heads towards you.