Wednesday, June 06, 2007

See (and hear) it while it lasts . . .

Thunder? It's the sound of Greenland melting

ILULISSAT, Greenland (Reuters) -- Atop Greenland's Suicide Cliff, from where old Inuit women used to hurl themselves when they felt they had become a burden to their community, a crack and a thud like thunder pierce the air.

"We don't have thunder here. But I know it from movies," says Ilulissat nurse Vilhelmina Nathanielsen, who hiked with us through the melting snow. "It's the ice cracking inside the icebergs. If we're lucky we might see one break apart."

It's too early in the year to see icebergs crumple regularly but the sound is a reminder. As politicians squabble over how to act on climate change, Greenland's ice cap is melting, and faster than scientists had thought possible.

A new island in East Greenland is a clear sign of how the place is changing. It was dubbed Warming Island by American explorer Dennis Schmitt when he discovered in 2005 that it had emerged from under the retreating ice.

If the ice cap melted entirely, oceans would rise by 23 feet, flooding New York and London, and drowning island nations like the Maldives.

A total meltdown would take centuries but global warming, which climate experts blame mainly on human use of fossil fuels, is heating the Arctic faster than anywhere else on Earth.

"When I was a child, I remember hunters dog-sledding 50 miles on ice across the bay to Disko Island in the winter," said Judithe Therkildsen, a retiree from Aasiaat, a town south of Ilulissat on Disko Bay.

"That hasn't happened in a long time."

Greenland, the world's largest island, is mostly covered by an ice cap of about 624,000 cubic miles that accounts for a 10th of all the fresh water in the world.

Over the last 30 years, its melt zone has expanded by 30 percent.

"Some people are scared to discover the process is running faster than the models," said Konrad Steffen, a glaciologist at University of Colorado at Boulder and a Greenland expert who serves on a U.S. government advisory committee on abrupt climate change.

In the past 15 years, winter temperatures have risen about 9 degrees Fahrenheit on the cap, while spring and autumn temperatures increased about 5 degrees Fahrenheit. Summer temperatures are unchanged.

Swiss-born Steffen is one of dozens of scientists who have peppered the Greenland ice cap with instruments to measure temperature, snowfall and the movement, thickness and melting of the ice.

Since 1990, Steffen has spent two months a year at Swiss Camp, a wind-swept outpost of tents on the ice cap, where he and other researchers brave temperatures of minus 22 degrees Fahrenheit to scrutinize Greenland's climate change clues.

The more the surface melts, the faster the ice sheet moves towards the ocean. The glacier Swiss Camp rests on has doubled its speed to about 9 miles a year in the last 12 years, just as its tongue retreated 10 km into the fjord.

"It is scary," said Steffen. "This is only Greenland. But Antarctica and glaciers around the world are responding as well."

Two to three days' worth of icebergs from this glacier alone produce enough fresh water to supply New York City for a year.

The rush of new water leaves scientists with crucial questions about how much sea levels could rise and whether the system of ocean currents that ensures Western Europe's mild winters -- known as the "conveyor belt" -- could shut down.

"Some models can predict a change in the conveyor belt within 50 to 100 years," said Steffen. "But it's one out of 10 models. The uncertainty is quite large."

If you're a fisherman in Greenland, however, global warming is doing wonders for your business.

Warmer waters entice seawolf and cod to swim farther north in the Atlantic into Greenlandic nets. In this Disko Bay town, the world's iceberg capital, the harbor is now open year-round because winter is no longer cold enough to freeze it solid.

Warmer weather also boosts tourism, a source of big development hopes for the 56,000 mostly Inuit inhabitants of Greenland, which is a self-governing territory of Denmark.

Hoping to lure American visitors, Air Greenland launched a direct flight from Baltimore last month, and there is even talk of "global warming tourism" to see Warming Island.

One commentator, noting the carbon dioxide emissions such travel would create, has called that "eco-suicide tourism."

Original article posted here.

1 comment:

Anonymous said...

Dr Tao was chosen by RAND as the worlds best to investigate this.
Enjoy the read:-)

Electric-Field Assisted Fuel Atomization
R. Tao
Department of Physics, Temple University, Philadelphia, PA 19122, USA
Fuel injection technology is employed in most combustion systems, such as
internal combustion engines or oil burners. It has been well known that atomization plays
an important role in combustion efficiency and pollutant emissions — specifically, that a
finer fuel mist allows a more efficient burn of the fuel, resulting in fewer harmful
emissions. This is attributed to a fact that combustion starts from the interface between
the fuel and air (oxygen). If we reduce the size of the fuel droplets, we increase the total
surface area to start burning, boost the combustion efficiency, and improve the emission.
There are a couple of new techniques in development to reach this goal. For
example, Delphi Company in its long-term project plans to develop a new fuel injector
that utilizes a high pressure of 200 bar to reduce the size of fuel droplets to 25 μm in
diameter. This injector, called Delphi Multec™ Direct Injection Gasoline Spray Stratified
Injector, requires substantial changes of the fuel lines in vehicles as the current vehicles
can only sustain a fuel pressure less than 3 bars [1].
Another possible technique is the electrostatic atomization, which makes all fuel
droplets negatively charged [2-6]. The droplet size will be small if the charge density on
the droplets is high. In addition, since the negatively charged droplets are repulsive to
each other, no agglomeration could occur. Unfortunately, up to date, electrostatic
atomization technology has not been employed on any fuel systems, not to say on
vehicles. The main reason is that the electrostatic atomization technology requires special
fuel injectors with a very high voltage directly applied on. Shown in Fig.1 is a typical
such fuel injector for the electrostatic atomization [6], which is completely different from
any existing fuel injectors employed on vehicles now. It requires a high voltage directly
applied on the nozzle. The emitter cathode emits negative charges to pass the fuel to the
anode, while it cannot move down to close the nozzle in order to stop the spray. To
employ such a fuel injector on vehicles is not an easy task.
Fig. 1 The fuel injector for electrostatic atomization. The high voltage needs to be applied
directly on the nozzle.
The new technology reported here is novel and unconventional since it does not need
to change the existing fuel injector. In fact, the developed device is just an add-on for the
current existing fuel injectors and it can be used with all current fuel injectors on vehicles.
Our experiments, in fact, were conducted with an Accel fuel injector (Fig.2) , which is
widely used on many automobiles. Our invention does not try to provide negative charges
to fuel droplets as in the electrostatic atomization. Instead, our invention lets the fuel pass
an electric field to have its viscosity reduced. When the viscosity of the fuel is reduced,
the size of the sprayed droplets is reduced, too [7,8].
Fig.2 The Accel high impedance fuel injector used in our experiment.
Fig.3 The experimental setup. The fuel flows through two metallic meshes before it
reaches the fuel injector. A voltage is applied on the two meshes to produce an electric
field around 1kV/mm in the space between the two meshes.
Fig.4. Two copper meshes are inserted inside the fuel line.
The experimental setup is in Fig.3. As mentioned before, the fuel injector was an
Accel high impedance fuel injector (Fig.2). Inside the fuel line were inserted two copper
meshes (Fig.4), on which a voltage is applied to produce a strong electric field, about
1kV/mm, in the space within the two meshes. We also arranged the anode is close to the
fuel injector, so that the produced electric field was opposite to the fuel flow direction. In
the experiment, we let the fuel take about 15 seconds to pass the electric field. One fuel
spray lasted for about 4 milliseconds. The droplets were collected by a plate, which was
covered with a layer of oxidized magnesium. Once the droplets were collected, the plates
were scanned by a high-resolution scanner and the droplet size distributions were then
analyzed by computers.
Our glass plate is a square, about 10cm x 10 cm, which is large enough to collect
all droplets in the spray. Shown in Fig.5 is a typical recording of collected droplets.
While this method is slower and more time consuming than the optical scattering
technique, it is certainly much more reliable than any other methods: It provides no
ambiguity. Every droplet in the spray is recorded and physically measured.
Fig.5 A typical plate with collected sprayed droplets.
The statistical results for the diesel fuel are in Fig.6, while the results for
gasoline with 20% ethanol are in Fig.7. All of them are averaged over many tests. It is
clear from both figures that a strong electric field reduces the droplet size in the
atomization process.
For the experiment with diesel, the fuel pressure was 200 lb/in2 (psi), the electric
field was about 1.0kV/mm. The fuel took about 15 seconds to pass the electric field. The
effect on diesel fuel is very significant. For example, the number of droplets of radius
below 5 μm was increased from 5.3% to 15.3%. This was a factor of three. It is also clear
from Fig.4 that the electric field made most droplets to have radius below 40 μm. If such
a device is applied on a diesel vehicle, the fuel mileage will be increased by 15-30% and
the emission will also be greatly improved.
No electric field
With Electric Field of 1 kV/mm
Fig.6 The size distribution of diesel fuel in the atomization with or without electric field
applied. The fuel pressure was 200 psi. The electric field was 1.0kV/mm. The fuel took
about 15seconds to pass the electric field.
With Electric Field 1.2kV/mm
No Electric Field
Fig.7 The size distribution of gasoline (with 20% ethanol) in the atomization with or
without electric field. The fuel pressure was 110psi. The electric field was 1.2kV/mm.
The fuel took about 15 seconds to pass the electric field.
In the experiment with gasoline (with 20% ethanol), the fuel pressure was 110psi,
the electric field was 1.2kV/mm, and the fuel took about 15 seconds to pass the electric
field. The effect on gasoline is also significant. For example, the number of droplets with
radius of 10 μm was increased from 17.6% to 20.7%, an increase of 20%. If such a device
is applied on a vehicle, the gas mileage will be increased by 5-10% and the emission will
also be greatly improved.