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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.
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A week in the life of OSMP Rangers, dogs, dogs, dogs and other news
Jul 28th
• A report of a potential assault on Gregory Canyon Trail. A woman was kneed in the leg while trying to pass a couple of hikers who thought she was being rude. Suspects have not be found.
• A report of a campfire west of NCAR. Boulder Fire could see three foot flames close to Mallory Cave. Suspect/s was never found.
• A report of a dog bite on the Gregory Canyon trail. The dog bit the hiker while they were passing by on the trail.
• A report of a nine year old bit by a dog on the hand at the Bluebell Shelter.
• A visitor in the closure at Boulder Falls who had a warrant for his arrest. Rangers worked with Sheriff’s Officers on this person’s arrest.
• A report of an overdue hiker in the Mt. Sanitas area. Rangers worked with Sheriff’s Officers and RMR to locate the missing party.
• An injured hiker on the East Ridge trail of Mt. Sanitas who had sprained their ankle. Rangers worked with AMR on this call.
• A report of a grass fire on the Reynolds property. The fire was started by a vehicle and was quickly extinguished. The fire was about 30’X30’.
• A report of a party passed out at the Halfway House. The patient was there for a wedding, became overheated and passed out. Rangers helped AMR with this call.
Community Outreach
Reminder: Art Inspired by the Land – Art Show Opening Reception
Fri. July 26, 5 –7 pm
Boulder’s Open Space and Mountain Parks Department is excited to announce that we will host an art show in late summer at the Boulder Public Library Canyon Gallery (1001 Arapahoe Avenue, Boulder). This show will celebrate art created by the community and inspired by OSMP lands. Please join us for appetizers, quartet music from the Boulder Philharmonic, and beautifully inspiring community art celebrating your protected lands and wildlife. This reception is free and open to the public. The art show will run from July 20 – August 28 during normal library hours.
This year to date we have offered 184 educational programs with 8,600 people attending! (Requested hikes plus Natural Selections.)
Mountain Bike Patrol: Trail work last week on Spring Brook was a success. Thanks for everyone who came–Joel, John S, Dan, Jeremy W, Allison, Jeremy, John P, Paul, Steve, and Kyle.
CU police: Two suspects wanted in connection with backpack, laptop theft
Jul 25th
Police are trying to identify two male suspects who investigators believe are responsible for stealing an unattended backpack outside the Target store, located at 2800 Pearl St., on July 12, 2013. The incident occurred at approximately 3:54 p.m.
The male victim told investigators he was waiting outside the store for an acquaintance to arrive. When the acquaintance showed up, the victim walked away from his backpack for a few minutes, forgetting that he had left it behind. Inside the backpack were personal items and a Samsung laptop computer.
When the victim remembered that he’d left his backpack, he went back to retrieve it and found that it was gone. Surveillance video from Target shows two males, one of whom is believed to have stolen the backpack and laptop. A surveillance photo is attached.
The main suspect is described as:
- White male
- Age unknown
- Brown hair
- Wearing a green windbreaker and shorts, and a white bicycle helmet
- Carrying a blue backpack on his back and the stolen backpack in his arms.
The second suspect is described as:
- White male
- Age unknown
- Wearing blue jeans, a light colored shirt and a red hat.
- Carrying a dark colored backpack on his back and walking two bicycles away from the scene.
When the male suspect stole the backpack, he was seen walking south as he left the area.
The case number is 13-9117.
Anyone with information is asked to contact Det. Craig Beckjord at 303-441-3336. Those who have information but wish to remain anonymous may contact the Northern Colorado Crime Stoppers at 1-800-222-TIPS (8477) or 1-800-444-3776. Tips can also be submitted through the Crime Stoppers website at www.crimeshurt.com. Those submitting tips through Crime Stoppers that lead to the arrest and filing of charges on a suspect(s) may be eligible for a cash reward of up to $1,000 from Crime Stoppers.
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