Posts tagged San Francisco
CU Boulder research team finds massive crevasses and bendable ice affect stability of Antarctic ice shelf
Dec 7th
Gaping crevasses that penetrate upward from the bottom of the largest remaining ice shelf on the Antarctic Peninsula make it more susceptible to collapse, according to University of Colorado Boulder researchers who spent the last four Southern Hemisphere summers studying the massive floating sheet of ice that covers an area twice the size of Massachusetts.
But the scientists also found that ribbons running through the Larsen C Ice Shelf – made up of a mixture of ice types that, together, are more prone to bending than breaking – make the shelf more resilient than it otherwise would be.
The research team from CU-Boulder’s Cooperative Institute for Research in the Environmental Sciences presented the findings Dec. 6 at the American Geophysical Union’s annual meeting in San Francisco.
The Larsen C Ice Shelf is all that’s left of a series of ice shelves that once clung to the eastern edge of the Antarctic Peninsula and stretched into the Weddell Sea. When the other shelves disintegrated abruptly – including Larsen A in January 1995 and Larsen B in February 2002 – scientists were surprised by the speed of the breakup.
Researchers now believe that the catastrophic collapses of Larsen A and B were caused, at least in part, by rising temperatures in the region, where warming is increasing at six times the global average. The Antarctic Peninsula warmed 4.5 degrees Fahrenheit since the middle of the last century.
The warmer climate increased meltwater production, allowing more liquid to pool on top of the ice shelves. The water then drained into surface crevasses, wedging them open and cracking the shelf into individual icebergs, which resulted in rapid disintegration.
But while the meltwater may have been responsible for dealing the final blow to the shelves, researchers did not have the opportunity to study how the structure of the Larsen A and B shelves may have made them more vulnerable to drastic breakups – or protected the shelves from an even earlier demise.
CU-Boulder researchers did not want to miss the same opportunity on the Larsen C shelf, which covers more than 22,000 square miles of sea.
“It’s the perfect natural laboratory,” said Daniel McGrath, a doctoral student in the Department of Geography and part of the CIRES research team. “We wanted to study this shelf while it’s still stable in order to get a better understanding of the processes that affect ice shelf stability.”
McGrath worked with CIRES colleagues over the last four years to study the Larsen C shelf in order to better understand how the warming climate may have interacted with the shelf’s existing structure to increase its vulnerability to a catastrophic collapse.
McGrath presented two of the group’s key findings at the AGU meeting. The first was the role that long-existing crevasses that start at the base of the shelf and propagate upward – known as basal crevasses – play in making the shelf more vulnerable to disintegration. The second relates to the way a type of ice found in areas called suture zones may be protecting the shelf against a breakup.
The scientists used ground penetrating radar to map out the basal crevasses, which turn out to be massive. The yawning cracks can run for several miles in length and can penetrate upwards for more than 750 feet. While the basal crevasses have been a part of Larsen C for hundreds of years, the interaction between these features and a warming climate will likely make the shelf more susceptible to future disintegration. “They likely play a really important role in ice-shelf disintegration, both past and future,” McGrath said.
The research team also studied the impact of suture zones in the ice shelf. Larsen C is fed by 12 distinct glaciers, which dump a steady flow of thick ice into the shelf. But the promontories of land between the glacial outlets, where ice does not flow into the shelf, allow for the creation of ribbon-like suture zones, which knit the glacial inflows together and which turn out to be important to the ice shelf’s resilience. “The ice in these zones really holds the neighboring inflows together,” McGrath said.
The suture zones get their malleable characteristic from a combination of ice types. A key component of the suture zone mixture is formed when the bottoms of the 12 glacial inflows begin to melt. The resulting freshwater is more buoyant than the surrounding seawater, so it rises upward to the relatively thinner ice zones between the glacial inflows, where it refreezes on the underside of the shelf and contributes to the chaotic ice structure that makes suture zones more flexible than the surrounding ice.
It turns out that the resilient characteristics of the suture zones keep cracks, including the basal crevasses, from spreading across the ice shelf, even where the suture zone ice makes up a comparatively small amount of the total thickness of the shelf. The CIRES team found that at the shelf front, where the ice meets the open sea, suture zone ice constitutes only 20 percent of the total thickness of the shelf but was still able to limit the spread of rifts through the ice. “It’s a pretty small part of the total ice thickness, and yet, it still has this really important role of holding the ice shelf together,” McGrath said.
Other CU researchers involved in the Larsen C project were Konrad Steffen, former director of CIRES; Ted Scambos, of CIRES and CU-Boulder’s National Snow and Ice Data Center; Harihar Rajaram, of the Department of Civil Engineering; and Waleed Abdalati, of CIRES.
CU BUFF GOLFERS FINISH SECOND AT UNM TUCKER INVITATIONAL
Sep 29th
The Buffaloes entered the day in third place, 15 shots back of the Lobos, and pulled to within 11 strokes early; but the home team got hot in the middle of the round and pulled away, finishing with a 15-under par 848 team score for a 29-stroke victory over the Buffaloes. Colorado posted a 14-over team score of 878, while San Francisco, in second after two rounds, slipped to third with a 22-over 886 tally.
Colorado is one of three schools to have played in all 58 Tucker invitationals (along with host New Mexico and New Mexico State); the Buffs have never won here but did also finish second in 1956 and 1981.
Senior Jason Burstyn and sophomore David Oraee led the Buffaloes here, as both tied for seventh with 1-over par 217 scores on the 7,578-yard, par-72 UNM Championship golf course.
Burstyn closed his efforts with a 4-over 76, scoring two birdies and six bogeys with 10 pars; his 12 birdies led cu for the week as he posted his third top 10 finish in four meets this fall.
Oraee had three birdies, nine pars and six bogeys en route to his final round 75 (3-over), as he duplicated his finish earlier in the week at CU’s Mark Simpson Invitational. He also has three top 10 efforts this season.
Senior Beau Schoolcraft recorded the team’s best individual score for the second straight round, and was the only Buff under par in the final round with a 1-under 71; he played a solid 18 with three birdies and 13 pars against just bogeys to finish up with a 4-over 220 score which tied him for 13th place (his third top 20 finish this fall). He had eight birdies, a team-best 34 pars and 12 bogeys for the tourney.
Senior Derek Fribbs tied for 38th with a 75 Saturday for a 10-over 226 score. He wrapped things up with two birdies, 12 pars, three bogeys and a double. Freshman Philip Juel-Berg tied for 53rd after fashioning a 2-over 74 in the final round for a 14-over 230. He had two birdies, 12 pars and four bogeys Saturday.
Junior Johnny Hayes competed here as an individual, closing things out with a 5-over 77 (one birdie, 11 par, six bogeys). That also gave him a 14-over 230 total, thus tying Juel-Berg with a 53rd place finish. He had CU’s lone eagle here this weekend with four birdies and 30 pars.
“We got off to a good start and made up a couple of shots, but the New Mexico just hit the gas and ran away from everyone,” coach Roy Edwards said. “We knew the guys would be a little tired from a pretty long week (CU’s tournament was last Monday and Tuesday), and we kind of ran out of gas and didn’t play very well on the back nine. But it’s a credit to the guys to still go out there and shoot the fourth lowest round of the day and also move into second place. We still matched the highest we’ve ever finished here, and it had been three decades since we finished this high.
“I don’t think any team in the country would have beaten New Mexico today. So we’re excited about that.”
CU’s 7-over 295 score on Saturday trailed New Mexico’s 281, the best team round of the tournament, and Minnesota and UTEP’s rounds (294) by a single shot.
New Mexico’s Gavin Green recorded a final round 69 for a 7-under 209 total to win by one stroke over Minnesota’s Erik Van Rooyen, who closed with a 71 and a 210 score.
The Buffaloes, now 37-2 against Division I competition in three tournaments this fall, are off for two weeks until Oct. 8-9, when they will travel to Portland to take part in the Pac-12 Conference Fall Preview.
“Overall, it was a good, solid week for the Buffaloes,” Edwards added. “While we didn’t play our best today, Beau turned in a quality round and Jason and David had solid tournaments.”
BUFFALO INDIVIDUALS (*—played as an individual)
T7. Jason Burstyn………………………………….. 68-73-76—217
T7. David Oraee……………………………………… 69-73-75—217
T13. Beau Schoolcraft……………………………… 77-72-71—220
T38. Derek Fribbs…………………………………….. 75-76-75—226
T53. Philip Juel-Berg………………………………… 79-77-74—230
T53. *Johnny Hayes………………………………… 75-78-77—230
TOP 5 INDIVIDUALS
1. Gavin Green, New Mexico……………………. 71-69-69—209
2. Erik Van Rooyen, Minnesota……………….. 66-73-71—210
3. John Catlin, New Mexico……………………… 76-69-67—212
4. Cory McElyea, San Francisco……………… 69-69-75—213
5. Pete Fernandez, UC-Irvine…………………… 70-69-75—214
TEAM SCORES
1. New Mexico………………………………….. 283-285-281—849
2. Colorado…………………………………….. 289-294-295—878
3. San Francisco………………………………. 297-284-305—886
4. Brigham Young…………………………….. 298-293-299—890
4. Minnesota……………………………………. 288-308-294—890
4. Baylor………………………………………….. 296-290-304—890
7. Texas-El Paso………………………………. 299-298-294—891
8. UC-Irvine……………………………………… 287-301-304—892
9. Arizona…………………………………………. 293-299-303—895
10. Utah…………………………………………….. 303-297-302—902
11. Texas-San Antonio……………………….. 301-299-305—905
12. New Mexico State…………………………. 304-299-305—908
13. Wyoming………………………………………. 308-292-310—910
14. Pepperdine…………………………………… 310-300-308—918
Boulder to test green bike-lanes
Sep 13th