Posts tagged temperature
Ice-free Arctic winters could explain amplified warming during Pliocene
Jul 29th
Year-round ice-free conditions across the surface of the Arctic Ocean could explain why the Earth was substantially warmer during the Pliocene Epoch than it is today, despite similar concentrations of carbon dioxide in the atmosphere, according to new research carried out at the University of Colorado Boulder.
The last time researchers believe the carbon dioxide concentration in the atmosphere reached 400 ppm—between 3 and 5 million years ago during the Pliocene—the Earth was about 3.5 to 9 degrees Fahrenheit warmer (2 to 5 degrees Celsius) than it is today. During that time period, trees overtook the tundra, sprouting right to the edges of the Arctic Ocean, and the seas swelled, pushing ocean levels 65 to 80 feet higher.
Scientists’ understanding of the climate during the Pliocene has largely been pieced together from fossil records preserved in sediments deposited beneath lakes and on the ocean floor.
“When we put 400 ppm carbon dioxide into a model, we don’t get as warm a planet as we see when we look at paleorecords from the Pliocene,” said Jim White, director of CU-Boulder’s Institute of Arctic and Alpine Research and co-author of the new study published online in the journal Palaeogeography, Paleoclimatology, Palaeoecology. “That tells us that there may be something missing in the climate models.”
Scientists have proposed several hypotheses in the past to explain the warmer Pliocene climate. One idea, for example, was that the formation of the Isthmus of Panama, the narrow strip of land linking North and South America, could have altered ocean circulations during the Pliocene, forcing warmer waters toward the Arctic. But many of those hypotheses, including the Panama possibility, have not proved viable.
For the new study, led by Ashley Ballantyne, a former CU-Boulder doctoral student who is now an assistant professor of bioclimatology at the University of Montana, the research team decided to see what would happen if they forced the model to assume that the Arctic was free of ice in the winter as well as the summer during the Pliocene. Without these additional parameters, climate models set to emulate atmospheric conditions during the Pliocene show ice-free summers followed by a layer of ice reforming during the sunless winters.
“We tried a simple experiment in which we said, ‘We don’t know why sea ice might be gone all year round, but let’s just make it go away,’ ” said White, who also is a professor of geological sciences. “And what we found was that we got the right kind of temperature change and we got a dampened seasonal cycle, both of which are things we think we see in the Pliocene.”
In the model simulation, year-round ice-free conditions caused warmer conditions in the Arctic because the open water surface allowed for evaporation. Evaporation requires energy, and the water vapor then stored that energy as heat in the atmosphere. The water vapor also created clouds, which trapped heat near the planet’s surface.
“Basically, when you take away the sea ice, the Arctic Ocean responds by creating a blanket of water vapor and clouds that keeps the Arctic warmer,” White said.
White and his colleagues are now trying to understand what types of conditions could bridge the standard model simulations with the simulations in which ice-free conditions in the Arctic are imposed. If they’re successful, computer models would be able to model the transition between a time when ice reformed in the winter to a time when the ocean remained devoid of ice throughout the year.
Such a model also would offer insight into what could happen in our future. Currently, about 70 percent of sea ice disappears during the summertime before reforming in the winter.
“We’re trying to understand what happened in the past but with a very keen eye to the future and the present,” White said. “The piece that we’re looking at in the future is what is going to happen as the Arctic Ocean warms up and becomes more ice-free in the summertime.
“Will we continue to return to an ice-covered Arctic in the wintertime? Or will we start to see some of the feedbacks that now aren’t very well represented in our climate models? If we do, that’s a big game changer.”
CU-Boulder geological sciences Professor Gifford Miller also is a co-author of the study. Researchers from Northwestern University and the National Center for Atmospheric Research also were involved in the study, which was supported by a grant from the National Science Foundation.
-CU-[includeme src=”http://c1n.tv/boulder/media/bouldersponsors.html” frameborder=”0″ width=”670″ height=”300″]
CU joins Sloan Digital Sky Survey to map stars, galaxies and quasars in 3D
Jun 26th
The survey, known as SDSS-IV, is the fourth stage of an effort that began with SDSS-I in 2000 to create the largest digital color image of the northern sky, said CU-Boulder Professor Michael Shull of the astrophysical and planetary sciences department, lead scientist in the effort by CU-Boulder to join the survey. Since 2000, astronomers have mapped about one-half of the visible northern sky in three dimensions as part of the three prior Sloan sky surveys, discovering nearly half a billion astronomical objects ranging from asteroids and stars to galaxies and distant quasars in the process.
“We got into this because we think it is going to be a great recruitment tool for new students, and we have one of the best undergraduate majors in the country,” Shull said. “We also want to recruit high-caliber graduate students and postdoctoral researchers.”
The SDSS 2.5-meter telescope is located at the Apache Point Observatory in Sunspot, N.M., and is owned by the Astrophysical Research Consortium, or ARC, an organization of eight research institutions including CU-Boulder. The Sloan telescope sky-mapping project is funded by the Alfred P. Sloan Foundation, the participating institutions, the National Science Foundation and the U.S. Department of Energy Office of Science. Apache Point also hosts several other telescopes, including a 3.5-meter optical telescope owned and operated by ARC and routinely used by CU-Boulder.
ARC was formed in 1984 to create a national observatory that could provide telescope time to each member university based on its investment. Current ARC members in addition to CU-Boulder are the University of Chicago, Johns Hopkins University, Princeton University, the Institute of Advanced Study in Princeton, N.J., the University of Washington, the University of Virginia and New Mexico State University. CU-Boulder owns a one-eighth share of each of the two telescopes.
The costs to build new instruments, make observations and analyze data from the SDSS-IV from 2014 to 2020 is estimated to be between $50 million and $60 million, said Shull. The Sloan Foundation is contributing roughly $10 million, while additional funds are coming from more than 10 full institutional members, including CU, and from scientists with individual and small group memberships from various institutions.
Full institutional partners like CU-Boulder are paying roughly $1 million to join part four of the Sloan sky survey effort. CU-Boulder’s member fee was supported by university grants, awards, donations, general funds and indirect cost recovery savings. As an early institutional partner joining the Sloan IV survey before the end of the current fiscal year, CU received a $350,000 discount from ARC, said Shull.
Light from the Sloan telescope is directed to two powerful new instruments — a dual-channel visible light, or optical spectrograph, and a near-infrared spectrograph. Astronomical spectrographs break light into telltale colors much like a prism, revealing information about the size, temperature, composition and motion of celestial objects, said Shull.
The Sloan spectrographs will carry out a massive survey of galaxies and quasars in the distant universe, as well as stars in the Milky Way and thousands of nearby galaxies, said Shull, who also is a member of CU-Boulder’s Center for Astrophysics and Space Astronomy.
The new optical spectrograph on the Sloan telescope can take data from up to 1,000 galaxies or quasars simultaneously, he said. The instrument includes a circular aluminum plate roughly the size of a large pizza pan with 1,000 small perforations precisely drilled to match up with known astronomical objects in the sky. Each hole is plugged with an optical fiber attached to the spectrograph.
“I think this is going to be a perfect way for undergraduates to get their hands dirty working with ‘big data,’ said Shull. “A lot of undergraduates are better at computers than we are, so hiring a freshman or a sophomore who really wants to get into computing and big data sets in the field of astronomy is one of our goals.”
One of the biggest discoveries by SDSS-III astronomers came in 2012 when they detected the predicted signature of the first sound waves from matter and radiation in the early universe, said Shull. Sloan researchers used a multi-fiber spectrograph as part of the Baryon Oscillation Sky Survey, or BOSS, to detect the large-scale structures of ancient galaxies — similar in some ways to ripples on a pond — that were preserved after the Big Bang.
Shull, who plans to use the multi-fiber spectrograph to hunt for distant quasars in the early universe going back 13 million years, said the BOSS effort also is expected to reveal new information about so-called “dark energy.” A hypothetical form of energy that makes up the majority of the universe and produces a force that opposes gravity, dark energy is thought to be the cause of the accelerating expansion of the universe.
Another SDSS-IV effort will be a sky survey in the infrared to probe the distribution, dynamics and chemistry of stars and to explore the formation of our Milky Way Galaxy and its two companion galaxies, the Large Magellanic Cloud and the Small Magellanic Cloud, said Shull. Since the two Magellanic Clouds are best viewed from the southern hemisphere, SDSS scientists plan to collaborate with astronomers who are using the 2.5 meter du Pont Telescope at Las Campanas, Chile, on the effort.
SDSS-IV astronomers also will be using the BOSS instrument to study the internal structure of 10,000 nearby galaxies. The data will include precise velocities of stellar motions and chemical abundances for a large range of galaxy masses, types and environments. The data will complement observations of two newly completed American telescopes: the ALMA millimeter and submillimeter array radio telescope in Chile and the Expanded-Very Large Array radio telescope in New Mexico.
SDSS-IV also has had a significant citizen science component since 2007, when a data set of a million galaxies was released to the public, who were asked to classify them in three categories: Elliptical galaxies, merging galaxies and spiral galaxies, including the direction of the spiral arms. An astounding 70,000 classifications were received by SDSS scientists from the public within an hour of the data release, and during the first year more than 150,000 people made more than 50 million galaxy classifications.
CU has a legacy in space dating back nearly 70 years, said CU-Boulder Vice Chancellor for Research Stein Sture. It is the top funded public university by NASA, has a $70 million instrument now flying on the Hubble Space Telescope, is leading a $485 million mission to Mars and controls four NASA satellites from campus.
A video news story on the project is available at http://youtu.be/1Rke59L5cAo.
-CU-
[includeme src=”http://c1n.tv/boulder/media/bouldersponsors.html” frameborder=”0″ width=”670″ height=”300″]
CU study hints conditions on Mars may support energy for life forms
May 30th
The findings, published in the journal Nature Geoscience, also hint at the possibility that hydrogen-dependent life could have existed where iron-rich igneous rocks on Mars were once in contact with water.
Scientists have thoroughly investigated how rock-water reactions can produce hydrogen in places where the temperatures are far too hot for living things to survive, such as in the rocks that underlie hydrothermal vent systems on the floor of the Atlantic Ocean. The hydrogen gases produced in those rocks do eventually feed microbial life, but the communities are located only in small, cooler oases where the vent fluids mix with seawater.
The new study, led by CU-Boulder Research Associate Lisa Mayhew, set out to investigate whether hydrogen-producing reactions also could take place in the much more abundant rocks that are infiltrated with water at temperatures cool enough for life to survive.
“Water-rock reactions that produce hydrogen gas are thought to have been one of the earliest sources of energy for life on Earth,” said Mayhew, who worked on the study as a doctoral student in CU-Boulder Associate Professor Alexis Templeton’s lab in the Department of Geological Sciences.
“However, we know very little about the possibility that hydrogen will be produced from these reactions when the temperatures are low enough that life can survive. If these reactions could make enough hydrogen at these low temperatures, then microorganisms might be able to live in the rocks where this reaction occurs, which could potentially be a huge subsurface microbial habitat for hydrogen-utilizing life.”
When igneous rocks, which form when magma slowly cools deep within the Earth, are infiltrated by ocean water, some of the minerals release unstable atoms of iron into the water. At high temperatures — warmer than 392 degrees Fahrenheit — scientists know that the unstable atoms, known as reduced iron, can rapidly split water molecules and produce hydrogen gas, as well as new minerals containing iron in the more stable, oxidized form.
Mayhew and her co-authors, including Templeton, submerged rocks in water in the absence of oxygen to determine if a similar reaction would take place at much lower temperatures, between 122 and 212 degrees Fahrenheit. The researchers found that the rocks did create hydrogen — potentially enough hydrogen to support life.
To understand in more detail the chemical reactions that produced the hydrogen in the lab experiments, the researchers used “synchrotron radiation” — which is created by electrons orbiting in a manmade storage ring — to determine the type and location of iron in the rocks on a microscale.
The researchers expected to find that the reduced iron in minerals like olivine had converted to the more stable oxidized state, just as occurs at higher temperatures. But when they conducted their analyses at the Stanford Synchrotron Radiation Lightsource at Stanford University, they were surprised to find newly formed oxidized iron on “spinel” minerals found in the rocks. Spinels are minerals with a cubic structure that are highly conductive.
Finding oxidized iron on the spinels led the team to hypothesize that, at low temperatures, the conductive spinels were helping facilitate the exchange of electrons between reduced iron and water, a process that is necessary for the iron to split the water molecules and create the hydrogen gas.
“After observing the formation of oxidized iron on spinels, we realized there was a strong correlation between the amount of hydrogen produced and the volume percent of spinel phases in the reaction materials,” Mayhew said. “Generally, the more spinels, the more hydrogen.”
Not only is there a potentially large volume of rock on Earth that may undergo these low temperature reactions, but the same types of rocks also are prevalent on Mars, Mayhew said. Minerals that form as a result of the water-rock reactions on Earth have been detected on Mars as well, which means that the process described in the new study may have implications for potential Martian microbial habitats.
Mayhew and Templeton are already building on this study with their co-authors, including Thomas McCollom at CU-Boulder’s Laboratory for Atmospheric and Space Physics, to see if the hydrogen-producing reactions can actually sustain microbes in the lab.
This study was funded by the David and Lucille Packard Foundation and with a U.S. Department of Energy Early Career grant to Templeton.
-CU-
[includeme src=”http://c1n.tv/boulder/media/bouldersponsors.html” frameborder=”0″ width=”670″ height=”300″]