Stories tagged Earth and Space Science

Apr
09
2010

By Our Hands: Cities are perhaps the most impressive mark humankind has left upon the face of planet Earth.
By Our Hands: Cities are perhaps the most impressive mark humankind has left upon the face of planet Earth.Courtesy anaxila

Throughout the ongoing debate about exactly how, to what extent, and the ethical implications, the indisputable fact remains that humankind has altered the planet. Back when the human population was only a few thousand strong and agriculture and cooked food were the latest inventions, it was easy for the Joneses to pick up and move camp when the water ran dry, the soil stopped producing tasty wheat, or the garbage piled too high in the backyard. The same can’t be said for the populations of world cities today.

Advances in public health, industry, and agriculture have blown the human population out of the brush. There will soon be 9 billion people on the face of planet Earth! Coupled with rising affluence, our ballooning population’s resource consumption and waste outputs are wrecking havoc on natural systems. New research (see several links below for more info) suggests that within a fixed amount of space, humankind is in danger of causing our own extinction and the only way out is to discard traditional ideas of industrialization and embrace sustainability.

No, silly...: Not THAT kind of tipping point!
No, silly...: Not THAT kind of tipping point!Courtesy Go Gratitude

The first step to bailing out humankind is to investigate how close to failure the world actually is. This was the point of a recent international collaboration: to calculate safe limits for pivotal environmental processes. The key idea here is that of “tipping points,” which can be thought of as thresholds or breaking points. Think about being pestered by your brother or sister: aren’t you able to put up with the annoyance for even a little while before you get so upset you retaliate? That’s your tipping point – the last straw that put you over the edge.

Led by Stockholm Resilience Center’s Johan Rockstrom, a group of European, Australian, and American scientists – including the University of Minnesota’s Institute on the Environment’s director, Jonathan Foley – identified nine processes reaching their tipping points. Three (climate change, nutrient cycles, and biodiversity loss) have already been pushed past their tipping points, four (ocean acidification, ozone depletion, freshwater use, and land use) are approaching their tipping points, and two (aerosol loading and chemical pollution) do not yet have identified tipping points because they require more research. The Institute on the Environment recently released a YouTube video addressing the conclusion of this new research:

Blissfully, there are things we can do to stop hurting the planet and begin patching its wounds. According to Foley’s article, we can’t let ourselves get any closer to the tipping points and piecemeal solutions won’t cut it because of the interconnectedness of the issues. Instead, we should focus on switching to low- or no-carbon fuel sources, stopping deforestation, and rethinking our approaches to agriculture.

There's No Place Like Home: It's worth keeping healthy.
There's No Place Like Home: It's worth keeping healthy.Courtesy NASA

The conclusions of this research have been well-accepted, but there has been some criticisms for 1) attempting to establish tipping points at all, and 2) for the appropriateness of the establish tipping points. If you would like more information, including commentaries, please check out the following sources:

Article in Nature: A safe operating space for humanity

Commentaries: Planetary Boundaries

Article in Scientific American: Boundaries for a Health Planet

Article in Ecology and Society: Planetary Boundaries: Exploring the Safe Operating Space for Humanity

Two questions to consider as you watch the YouTube video and take a look through the links and articles referenced above are:

1) What are the consequences of being past our tipping points?

2) How do the solutions discussed prevent us from reaching tipping points?

You are encouraged to post your thoughtful answers below!

Mar
18
2010

If you're visiting the Science Museum of Minnesota, look out the windows from the Mississippi River Gallery on level 5. If you're in downtown St. Paul, stop by the museum and look at the river from the overlook on Kellogg Plaza. (City officials are asking folks not to flock to areas where barriers are going up - especially Harriet Island - but the view from in or around the museum is spectacular and safe.)

Kate's photos, 3/18 (3): Looks peaceful, doesn't it? Still, the city is warning people to stay off of the river, out of the low-lying parks, and away from Harriet Island and Water Street.
Kate's photos, 3/18 (3): Looks peaceful, doesn't it? Still, the city is warning people to stay off of the river, out of the low-lying parks, and away from Harriet Island and Water Street.Courtesy Kate Hintz

The Mississippi is going up FAST today, and forecasters expect that the river will officially reach "flood stage" by early this afternoon. (It's 10:45am, and the river's at 11.67'. It's risen a foot and a half in the last 24 hours, should reach 12' ("action stage") pretty soon, and 14' ("flood stage") by late today.

Kate's photos, 3/18 (2): Look across the river to the floodwall: that's the high-water mark for the 1965 flood, the highest in recorded history. That year, the river crested here in downtown St. Paul at 26.01' and marked the end for the communities then down on the river flats.
Kate's photos, 3/18 (2): Look across the river to the floodwall: that's the high-water mark for the 1965 flood, the highest in recorded history. That year, the river crested here in downtown St. Paul at 26.01' and marked the end for the communities then down on the river flats.Courtesy Kate Hintz

Kate's photos, 3/18 (1): Shepard/Warner roads will close from Chestnut Street to US 61 starting Saturday morning, and could remain closed for weeks. Take your river sightseeing drive/bike ride/walk before then!
Kate's photos, 3/18 (1): Shepard/Warner roads will close from Chestnut Street to US 61 starting Saturday morning, and could remain closed for weeks. Take your river sightseeing drive/bike ride/walk before then!Courtesy Kate Hintz

So what's going on around the river?

  • The city has closed all city boat launches and temporarily banned all recreational boating within the city limits.
  • Water Street will be entirely closed, starting this afternoon.
  • Hidden Falls and Lilydale regional parks are closed.
  • Flood barriers are going up at the St. Paul downtown airport and at Harriet Island.
  • Harriet Island will close once the river reaches 17'.
  • Warner/Shepard Roads will be closed from Chestnut Street to US 61 starting Saturday morning in preparation for the construction of a temporary levee that could withstand river levels to 26'. These roads could be closed for weeks, depending on the extent of the flooding.

Here's the latest hydrology graph:
3/18 hydrology graph, 10:15am
3/18 hydrology graph, 10:15amCourtesy USGS

Check out our full feature on the 2010 Mississippi River flooding.

Mar
17
2010

Look out the window or walk down the street to nearly any river or stream in Minnesota right now and you are likely to observe two things about the river:

  1. it is getting deeper (or “rising” in relation to the banks); and
  2. it appears to be moving faster.

You can, of course, confirm these observations by investigating reports from gauging stations along these rivers, maintained by the U.S. Geological Survey. (See data for the gauging station serving downtown St. Paul.) But what is really happening?

It may be high and fast...: ...but (as of today) the Mississippi at St. Paul is still in a bankfull state.
It may be high and fast...: ...but (as of today) the Mississippi at St. Paul is still in a bankfull state.Courtesy Liza Pryor

Until a river flows over its banks, it is considered to be in a “bankfull” state. In this state, the water flowing through the river is confined to a relatively fixed channel area. Simply put, floods occur because more water is being introduced into this channel from upstream, due to snowmelt, heavy rains, or a dam breach. As this added volume of water moves through a fixed area, it both increases in velocity and in depth until it overflows the banks, at which point some, but not necessarily a lot, of the volume and velocity moving through the channel are reduced.

Scientists call the rate of flow through a channel “discharge." Discharge is defined as the volume of water passing through a given cross-section of the river channel within a specified period of time.A simple equation for determining discharge is

Q = D x W x V

where Q = discharge, D = channel depth, W = channel width and V = velocity.

Looking at this equation, it is easy to see that if discharge becomes greater and channel width is fixed, then an increase in both volume and depth (or height relative to the banks) is likely to be the cause. Discharge can be measured in cubic feet per second or cubic meters per second, for example.

But is the river flowing at the same rate at the surface as it does along its banks and beds? Understanding this requires investigating some more detailed equations, as the banks and bed introduce friction, which affects the rate of flow.

To learn more about rivers and how they flow, you may want to check out the works of Luna Leopold, and M. Gordon Wolman. In particular:

  • Leopold, Luna B. (2006, reprint). A View of the River. Harvard University Press; and
  • Leopold, Luna B.; Wolman, M. Gordon; and Miller, John P. (1995). Fluvial Processes in Geomorphology. Dover Publications, both classics for understanding how rivers work.

Also, check out our full feature on the 2010 Mississippi River flooding.

Mar
16
2010

All day, up in the Mississippi River Gallery, people have been stopping to look out the window and watch the river.

Here's how the US Geological Survey sees it:
Mississippi River, actual vs. forecast, 3/16/10, 1pm
Mississippi River, actual vs. forecast, 3/16/10, 1pmCourtesy USGS

The river's rising, but not as fast as yesterday. And yesterday's rise outpaced predictions by almost a foot, but today the rise matches the predicted curve almost exactly.

So what are folks seeing out the window? Take a look.

Also check out our full feature on the 2010 Mississippi River flooding.

Watch the steps: They're a good benchmark.
Watch the steps: They're a good benchmark.Courtesy Liza Pryor

Raspberry Island: Still high and dry
Raspberry Island: Still high and dryCourtesy Liza Pryor

Looking upstream: You're still looking at Harriet Island. But low-lying areas of Lilydale (upstream, south side of the river) get inundated when the river reaches 14 feet or so. Right now, that's predicted to happen sometime after 7pm on Sunday, 3/21.
Looking upstream: You're still looking at Harriet Island. But low-lying areas of Lilydale (upstream, south side of the river) get inundated when the river reaches 14 feet or so. Right now, that's predicted to happen sometime after 7pm on Sunday, 3/21.Courtesy Liza Pryor

Mar
12
2010

Science Friday logo
Science Friday logo
Courtesy Science Friday
It's Friday, so it's time for a new Science Friday video. This week,

"What is the future of sustainable architecture? Washington University's Tyson Living Learning Center in Eureka, MO, achieves the Living Building Challenge--a set of green guidelines that measure a building based on its performance. The building's architect Dan Hellmuth, of Hellmuth & Bicknese Architects in St. Louis, and Kevin Smith, associate director of Tyson Research Center, point out some of the Center's greenest features."
Mar
06
2010

Chilean quake sped up Earth's rotation, tipped planet's axis

Earth spins faster
Earth spins fasterCourtesy NASA
If you read the post about how earthquakes differ, you would know that in the Chile earthquake, a large amount of the Earth's crust plunged under its neighboring crust, bringing it closer to the center of the earth.
Just as Olympic figure skaters spin faster when their arms move closer to their body, the Earth is now spinning faster making our day about 1.26 microseconds shorter than it was before the quake.
Earth was also slightly tipped off balance, like when a spinning skater brings in one arm but not the other. The planet's axis tilted about 8 centimeters. This is insignificant compared to other wobbles measuring several meters resulting from winds and ocean currents.

Feb
18
2010

Space travel kills you: Well, probably not you, but it would kill these two BFFs.
Space travel kills you: Well, probably not you, but it would kill these two BFFs.Courtesy JGordon
Heyo, Buzzketeers. Any Starketeer Treketeers out there?

Yes? Well check this bit of fun science out: a Professor at Johns Hopkins says that traveling at near-light speeds in a space ship (as folks often do in science fiction) would have the delightful effect of almost instantly killing everyone on board.

Aw, whoops. Did I say "fun"? I meant the opposite of fun.

See, it'd obviously be no good to run into a big chunk of rock while flying around super fast in outer space, but (fortunately) big chunks of rock are really pretty rare way out in space. That's not the problem. The problem is the tiny stuff. The really, really tiny stuff.

Here on Earth, each cubic centimeter of air has about 30 billion billion atoms in it. (That's right—two "billions.") In outer space, however, each cubic centimeter of space might have 2 atoms in it. Two lonely, harmless little hydrogen atoms, drifting around, looking for friends. That low-density of matter is no problem for a low-speed ship—it'd just zoom right through them—but for a ship approaching the speed of light, they could be a huge problem, according to this professor.

Because the ship would be going so fast, the hydrogen atoms would "appear highly compressed, thereby increasing the number of atoms hitting the craft." There's something here about Einstein's special theory of relativity here, but, you know, blah blah blah.That stuff is complicated. I think if it like going running on a buggy night—if you run fast through a cloud of bugs, more of those bugs are going to hit you, and harder. (The moral there being: run with your mouth closed, and run slowly, especially if you're naked.)

So, because so many of the hydrogen atoms are hitting the ship, and because the ship is going so fast, it would be like turning a giant particle accelerator on the ship (except, in this case, the ship is being accelerated into the particles, not the other way around, but the effect is the same). It would be like getting hit with approximately the same amount of energy as if you stepped into the beam of the Large Hadron Collider. Even with a 4-inch-thick aluminum hull, 99% of the hydrogen would blast through the ship as radiation, frying the electronics and killing the crew in seconds. Sad.

You can't wrestle a particle beam, Kirk.

Still, maybe there are some Trekkies and physicists out there who can make us all feel a little better about this? The Johns Hopkins professor clearly knows a ton about radiation, but maybe he's not such an expert on space, or about the physics of Star Trek. I'm certainly not. Don't they warp space on that show? So that they aren't traveling though billions of miles of space (and all that dangerous hydrogen), but are skipping from one spot to another? Something like that? Help me out here. The image of Spock dying of radiation poisoning (again) makes me cry salty tears.

Feb
17
2010

The Enriquillo fault: Only the western half of the Enriquillo fault ruptured during Haiti's January earthquake.
The Enriquillo fault: Only the western half of the Enriquillo fault ruptured during Haiti's January earthquake.Courtesy Mikenorton
Haiti’s January 12th earthquake occurred on a strike-slip fault that runs in an east/west direction through the country. The fault, known as the Enriquillo fault, is where the North American and Caribbean tectonic plates meet. The jostling of these plates caused a quake that measured 7.0 on the Richter scale, killed approximately 217,000 people, destroyed 280,000 residences and commercial buildings, and left over one million people homeless. It has been deemed the most destructive natural disaster that a single nation has endured. Unfortunately, geologists believe that another, equally destructive quake could occur in Haiti within the next 20-30 years. Using high-resolution radar images of the Enriquillo fault after the quake, geologists from the University of Miami found that only half (the western half) of the fault had surged. They speculate that the remaining energy still locked up in the earth is what will cause the next quake on the eastern portion of the fault.

The radar images also showed that the earthquake produced a lot of vertical motion, not typical in strike-slip faults. This vertical motion, say geologists, explains how such a small fault movement could cause such a large earthquake. From their analysis, geologists are recommending that Haiti move all of its essential infrastructure (schools, hospitals, etc.) north, out of the fault zone.

This is a great example of science being used to help avoid future devastation, or at least lessen future destruction. Knowing that there is still potential danger along the Enriqillo fault allows people to plan accordingly (i.e. building or rebuilding in a safer location). However, this is also a case where I hope science is wrong.

Feb
07
2010

Underwater, or “internal” waves, unlike the familiar wind-generated surface waves, occur due to density stratification often generated by coastal tides. These internal wave can lead to redistribution of nutrients and minerals. Internal waves can also cause vertical “velocity shear”, intensifying the vertical mixing process within the water column and bringing suspended particles and nutrients to the surface. Understanding and tracking these internal waves is another way to monitor the vital signs of an estuary.

Internal waves
Internal wavesCourtesy CMOP

CMOP successfully launched its new autonomous underwater vehicles (AUV) to help scientists gain a better understanding of the Columbia River estuary. One of the first studies to use these vehicles will be directed at internal waves. Craig McNeil, oceanographer from the Applied Physics Laboratory at the University of Washington and CMOP investigator, is using AUV’s to study the generation and propagation of internal waves in the Columbia River estuary and plume. He's interested in the physics of internal waves and mixing near the sea surface and the sea floor.

McNeil said,

“Scientists speculate that some bottom following internal waves have closed circulations that traps water and biology. The AUVs will help us sample these waves so we can better understand these complex mixing mechanisms.”

One upcoming experiment will study the dynamics of the freshwater plume as it spreads out over the denser saltwater of the coastal ocean. Of particular interest is to compare measured observations with theoretical predictions. McNeil will program the vehicles to travel into the advancing plume and navigate through the plume front. This will allow CMOP to study the progression of internal waves that are known to be generated at the advancing plume front and determine their propagation speed.

Watch researchers deploy the AUV: Watch Craig, Troy, and Trina deploy the AUV in the Columbia River.
Watch researchers deploy the AUV: Watch Craig, Troy, and Trina deploy the AUV in the Columbia River.Courtesy CMOP

Before those measurements could take place, McNeil needed to test the vehicles’ capabilities in the field. Along with oceanographer Trina Litchendorf and field engineer Troy Swanson, McNeil tested the vehicle in Lake Washington over the winter months. By spring the team was ready to take it through its paces in the Columbia River estuary.

They traveled to Astoria, Oregon, and met up with CMOP’s field team for the vehicle’s first mission in the river. They decided initial tests would be conducted during slack tide due to the limits of the vehicle in strong currents. The mission was based on tidal cycle information supplied by CMOP’s cyber-team. The expected velocities during slack tide would be less than 0.5 m/s or about 1 knot, which was in the acceptable range for the vehicles

The vehicle was deployed near the first transponder set by the team in the North Channel of the Columbia River. There it performed a compass calibration and proceeded to its first designated waypoint. To make sure it was on track, McNeil monitored the vehicle’s position with a device called the Ranger. The Ranger's transponder receives status updates from the vehicle.

Water temperature map: This figure shows a map of water temperature recorded by the CTD on the AUV during its first mission in the North Channel of the Columbia River estuary westward of the Astoria Bridge.
Water temperature map: This figure shows a map of water temperature recorded by the CTD on the AUV during its first mission in the North Channel of the Columbia River estuary westward of the Astoria Bridge.Courtesy CMOP

The results of the mission were a success. The vehicle traveled upon its designated coordinates and collected salinity and temperature data. Now the team has a better understanding of how to control the vehicle’s navigation in the river, which means it will be able to perform longer missions.

McNeil and his team will now use the AUVs to study various physical processes in the Columbia River estuary, including internal waves, currents, and mixing of various biogeochemical components of the water; all of these adding to our understanding of the estuary’s vital signs.

More photos of the AUV deployment: More photos of the AUV deployment
More photos of the AUV deployment: More photos of the AUV deploymentCourtesy CMOP

Feb
07
2010

Estuaries are coastal areas in which rivers and oceans meet. Thus, they include both fresh and salt water, each of which support different ecological communities of plants and animals, large and small. Salinity (“saltiness”) of the estuary is a measure of its health--a vital sign--for those communities.

In some cases, salt-water from the ocean side of the estuary can begin to “intrude” on an area previously dominated by fresh water. It is important to be able to measure and monitor this aspect estuary health.

CMOP has developed a remote sensing device that opens the way for scientists to better understand and predict salinity intrusions in estuaries.

Circuit analog for dipole source on river bed
Circuit analog for dipole source on river bedCourtesy CMOP

Oceanographer Thomas Sanford, Ph.D., and his team from the Applied Physics Laboratory at the University of Washington, have developed a bottom-mounted instrument for measuring electrical conductivity in the water column, which can be transformed into salinity readings.

The current process for measuring salinity involves sensors that provide “point” observations. Sanford’s instrument provides measurements of integrated salinities across the entire water column, allowing a more representative description of salinity intrusion.

How does it work?

Sanford’s approach is to produce a low-frequency electrical current and measure the resulting electric field at a nearby dipole receiver. The received electrical field is a function of the electrical conductivity of the water column and the sediments.

Quasi-static electrical analog circuit: The quasi-static electrical analog circuit for electric currents divided between the parallel resistors of saline water (Rw ) and the sediment (Rs ) is such that: Vr /Is = CRwRs /(Rw + Rs ) = C(Σw + Σs )-1 , ∴ Σw = CIs/Vr – Σs, where Σw is the conductance (vertical integral of σ) of the river, C is an empirical calibration value, Is is the source current, Vr is the receiver voltage and Σs is the conductance of the sediments
Quasi-static electrical analog circuit: The quasi-static electrical analog circuit for electric currents divided between the parallel resistors of saline water (Rw ) and the sediment (Rs ) is such that: Vr /Is = CRwRs /(Rw + Rs ) = C(Σw + Σs )-1 , ∴ Σw = CIs/Vr – Σs, where Σw is the conductance (vertical integral of σ) of the river, C is an empirical calibration value, Is is the source current, Vr is the receiver voltage and Σs is the conductance of the sedimentsCourtesy CMOP

Sanford’s team deployed the system in the Columbia River estuary before and during a flood tide. At the same time, they took measurements with a CTD, a standard oceanography-sampling device that reads Conductivity, Temperature and Depth. As the layer of seawater thickened, they observed the decreased resistance of the water column caused the receiver voltage to decrease.

Previous studies in the Columbia River had demonstrated a tight correlation between electrical conductivity and salinity. This correlation permits the conversion of electrical conductivity to salinity. Sanford’s team collected a time series of water-column electrical conductivity that they converted to salinity. The inferred salinity was shown to agree with the salinity readings from the CTD.

Vertically integrated salinity: Observed vertically integrated salinity from CTD casts (red dots) compared to that inferred from the electrical measurements using the electrical conductance time series fitted to the equation: Sw = 8.82*(CIs/Vr -Σs ), where C is an empirical coefficient equal to 43, Is is source current and Vr is observed electric field and Σs an offset caused by leakage into the sediments equal to 8. Blue dots are observed electrical conductance and the continuous curve is the electrical conductance, both converted by salinity by the factor 8.82 psu/S/m.
Vertically integrated salinity: Observed vertically integrated salinity from CTD casts (red dots) compared to that inferred from the electrical measurements using the electrical conductance time series fitted to the equation: Sw = 8.82*(CIs/Vr -Σs ), where C is an empirical coefficient equal to 43, Is is source current and Vr is observed electric field and Σs an offset caused by leakage into the sediments equal to 8. Blue dots are observed electrical conductance and the continuous curve is the electrical conductance, both converted by salinity by the factor 8.82 psu/S/m.Courtesy CMOP

What's next?

CMOP researchers are looking at Sanford’s new sensor as an opportunity to better explain processes as diverse as internal waves, estuarine turbidity, and summer blooms of phytoplankton (tiny mobile plants that sometimes collect in massive “blooms” in surface waters in estuaries). They expect to improve computer models that are designed to depict the variable conditions of the estuary, and anticipate changes associated with climate and human impact. Once demonstrated for the Columbia River, the new sensor has the potential to be used in estuaries around the world.