Carbon dioxide exchange of two ecodemes of Schistidium antarctici in Continental Antarctica

first_imgSchistidium antarctici is the commonest of five bryophytes known in the Windmill Islands area of Wilkes Land, Greater Antarctica. In moist habitats it forms closed carpets, but in dry sites it develops a short cushion growth form. Carbon dioxide exchange of both a mesic (Sm) and a xeric growth form (Sx) was investigated by means of an IRGA system in the field near Casey Station under natural light and simulated ambient or controlled temperature conditions in the plant chamber. The chlorophyll content in Sm was three times higher than in Sx. The light compensation point of Sm was lower than in Sx. The data for photosynthesis and dark respiration were computed by means of non-linear and linear regression analysis. Sm was more productive and had a wider temperature range of positive net photosynthesis than Sx under similar conditions. Dark respiration per gram of the whole moss sample was identical in both ecodemes. A decline of the photosynthesis curves at quantum flux densities above 500 μmol m-2 s-1 PAR indicated a photoinhibitory effect in Sm. Sx was even more sensitive to high irradiance levels. Photoinhibition was not apparent in laboratory measurements under artificial light. According to our field measurements the photoinhibitory effect increases with increasing temperature. Moisture loss was avoided during the experiments by water supply from the bottom and frequently spraying the moss samples with water. In the natural habitat the desiccating effect of solar radiation is important, as it quickly causes photosynthesis to cease. The moss will dry out sooner in a xeric habitat than in one which is continuously moist. Consequently, the mesic Schistidium might particularly be subjected to photoinhibition by bright sunshine.last_img read more

A redescription of Graneledone verrucosa (Verrill, 1881) (Octopoda: Octopodidae)

first_imgGraneledone verrucosa (Verrill 1881), the type species of the genus Graneledone, is redescribed based on historical material and previously unreported specimens that have resulted from an increase in deep-sea fishing in the North East Atlantic. Graneledone verrucosa var. media (Joubin 1918) was found to be invalid and is herein synonymized with G. verrucosa. Graneledone verrucosa is shown to inhabit deep water throughout the North Atlantic; its distribution extends from 20degrees to 65degrees N and from 9degrees to 75degrees W. A revised diagnosis is given for the genus Graneledone Joubin, 1918.last_img read more

Dynamic subauroral ionospheric electric fields observed by the Falkland Islands radar during the course of a geomagnetic storm

first_imgWe present an analysis of ionospheric electric field data observed during a geomagneticstorm by the recently deployed HF radar located on the Falkland Islands. On 3 August2010 at ∼1800 UT evidence of the onset of a geomagnetic storm was observed in groundmagnetometer data in the form of a decrease in the Sym‐H index of ∼100 nT. Themain phase of the storm was observed to last ∼24 hours before a gradual recovery lasting∼3 days. On 4 August, during the peak magnetic disturbance of the storm, a high velocity(>1000 m s−1) channel of ionospheric plasma flow, which we interpret as a subauroralion drift (SAID), located between 53° and 58° magnetic south and lasting ∼6.5 hours, wasobserved by the Falkland Islands radar in the pre‐midnight sector. Coincident flow datafrom the DMSP satellites and the magnetically near‐conjugate northern hemisphereBlackstone HF radar reveal that the SAID was embedded within the broader subauroralpolarization streams (SAPS). DMSP particle data indicate that the SAID location closelyfollowed the equatorward edge of the auroral electron precipitation boundary, whileremaining generally poleward of the equatorward boundary of the ion precipitation. Thelatitude of the SAID varied throughout the interval on similar timescales to variations inthe interplanetary magnetic field and auroral activity, while variations in its velocity weremore closely related to ring current dynamics. These results are consistent with SAIDelectric fields being generated by localized charge separation in the partial ring current, butsuggest that their location is more strongly governed by solar wind driving and associatedlarge‐scale magnetospheric dynamics.last_img read more

Paleo ice flow and subglacial meltwater dynamics in Pine Island Bay, West Antarctica

first_imgIncreasing evidence for an elaborate subglacialdrainage network underneath modern Antarctic ice sheetssuggests that basal meltwater has an important influence onice stream flow. Swath bathymetry surveys from previouslyglaciated continental margins display morphological featuresindicative of subglacial meltwater flow in inner shelf areas of some paleo ice stream troughs. Over the last few years several expeditions to the eastern Amundsen Sea embayment(West Antarctica) have investigated the paleo ice streams that extended from the Pine Island and Thwaites glaciers. A compilation of high-resolution swath bathymetry data from inner Pine Island Bay reveals details of a rough seabed topography including several deep channels that connect a series of basins. This complex basin and channel network is indicative of meltwater flow beneath the paleo-Pine Island and Thwaites ice streams, along with substantial subglacial water inflow from the east. This meltwater could have enhanced ice flow over the rough bedrock topography. Meltwater features diminish with the onset of linear features north of the basins. Similar features have previously been observed in several other areas, including the Dotson-Getz Trough (western Amundsen Sea embayment) and Marguerite Bay (SW Antarctic Peninsula), suggesting that these features may be widespread around the Antarctic margin and that subglacial meltwater drainage played a major role in past ice-sheet dynamics.last_img read more

High-latitude ocean and sea ice surface fluxes: Challenges for climate research

first_imgPolar regions have great sensitivity to climate forcing; however, understanding of the physical processes coupling the atmosphere and ocean in these regions is relatively poor. Improving our knowledge of high-latitude surface fluxes will require close collaboration among meteorologists, oceanographers, ice physicists, and climatologists, and between observationalists and modelers, as well as new combinations of in situ measurements and satellite remote sensing. This article describes the deficiencies in our current state of knowledge about air–sea surface fluxes in high latitudes, the sensitivity of various high-latitude processes to changes in surface fluxes, and the scientific requirements for surface fluxes at high latitudes. We inventory the reasons, both logistical and physical, why existing flux products do not meet these requirements. Capturing an annual cycle in fluxes requires that instruments function through long periods of cold polar darkness, often far from support services, in situations subject to icing and extreme wave conditions. Furthermore, frequent cloud cover at high latitudes restricts the availability of surface and atmospheric data from visible and infrared (IR) wavelength satellite sensors. Recommendations are made for improving high-latitude fluxes, including 1) acquiring more in situ observations, 2) developing improved satellite-flux-observing capabilities, 3) making observations and flux products more accessible, and 4) encouraging flux intercomparisons.last_img read more

Hierarchical population genetic structure in a direct developing Antarctic marine invertebrate

first_imgUnderstanding the relationship between life-history variation and population structure in marine invertebrates is not straightforward. This is particularly true of polar species due to the difficulty of obtaining samples and a paucity of genomic resources from which to develop nuclear genetic markers. Such knowledge, however, is essential for understanding how different taxa may respond to climate change in the most rapidly warming regions of the planet. We therefore used over two hundred polymorphic Amplified Fragment Length Polymorphisms (AFLPs) to explore population connectivity at three hierachical spatial scales in the direct developing Antarctic topshell Margarella antarctica. To previously published data from five populations spanning a 1500 km transect along the length of the Western Antarctic Peninsula, we added new AFLP data for four populations separated by up to 6 km within Ryder Bay, Adelaide Island. Overall, we found a nonlinear isolation-by-distance pattern, suggestive of weaker population structure within Ryder Bay than is present over larger spatial scales. Nevertheless, significantly positive Fst values were obtained in all but two of ten pairwise population comparisons within the bay following Bonferroni correction for multiple tests. This is in contrast to a previous study of the broadcast spawner Nacella concinna that found no significant genetic differences among several of the same sites. By implication, the topshell’s direct-developing lifestyle may constrain its ability to disperse even over relatively small geographic scales.last_img read more

Ocean-forced ice-shelf thinning in a synchronously coupled ice-ocean model

first_imgThe first fully synchronous, coupled ice shelf-ocean model with a fixed grounding line and imposed upstream ice velocity has been developed using the MITgcm (Massachusetts Institute of Technology general circulation model). Unlike previous, asynchronous, approaches to coupled modeling our approach is fully conservative of heat, salt, and mass. Synchronous coupling is achieved by continuously updating the ice-shelf thickness on the ocean time step. By simulating an idealized, warm-water ice shelf we show how raising the pycnocline leads to a reduction in both ice-shelf mass and back stress, and hence buttressing. Coupled runs show the formation of a western boundary channel in the ice-shelf base due to increased melting on the western boundary due to Coriolis enhanced flow. Eastern boundary ice thickening is also observed. This is not the case when using a simple depth-dependent parameterized melt, as the ice shelf has relatively thinner sides and a thicker central “bulge” for a given ice-shelf mass. Ice-shelf geometry arising from the parameterized melt rate tends to underestimate backstress (and therefore buttressing) for a given ice-shelf mass due to a thinner ice shelf at the boundaries when compared to coupled model simulations.last_img read more

Hall of Famer Ray Allen discusses his new autobiography in conversation with ABC News

first_imgApril 3, 2018 /Sports News – National Hall of Famer Ray Allen discusses his new autobiography in conversation with ABC News FacebookTwitterLinkedInEmailABC News.(NEW YORK) — Former professional basketball player Ray Allen spent nearly two decades playing in the NBA, and over the weekend, it was announced the star shooter was inducted into the Naismith Memorial Basketball Hall of Fame. Allen, who last played in the league in 2014, is part of a 2018 Hall of Fame class that includes former NBA stars Jason Kidd, Steve Nash, and Grant Hill.Allen recently sat down with ABC News to discuss his new autobiography From the Outside: My Journey Through Life and the Game I Love, reflecting on how his youth shaped his career and talking about the things that drove him to work towards a Hall of Fame career.“As a military dependent, you travel all over the world… you had to learn how to fit in,” Allen tells ABC News, discussing his military upbringing and how at times he felt like an “outsider” as a child. “Often times, sports bonded all of us.”His goal, and hope, was always to become a professional basketball player. While he was not surrounded by NBA athletes growing up, he witnessed a lot of missed opportunity: those who had the ability to reach the NBA, but never ended up making it.“There were examples of those in my community of why it didn’t happen for them… ‘Alcohol ruined me. Injuries ruined me.’ So, I was getting all this firsthand knowledge these are the things I need to steer clear of if I want to be successful. I don’t know if I can make it to the NBA, but I wanted to give myself a chance.”A high school basketball star in South Carolina, Allen went on to play the sport at UCONN and get drafted in the first round by the Minnesota Timberwolves. He talks about his college experience and NBA career, moving from Milwaukee to Seattle to Boston and Miami, but says there was more the wanted to include:“There was so much. It’s hard to encapsulate everything that I’ve known and everything that I’ve thought of and every person good and bad that has inspired me. After writing this, I thought I could write two books because there was so much.”Allen capped off his career in Miami, winning a championship with the Heat in 2013.His autobiography is now available in stores and online.Copyright © 2018, ABC Radio. All rights reserved. Written bycenter_img Beau Lundlast_img read more

NCAA: Utah College Track & Field Roundup: 5/11

first_img Brad James May 11, 2018 /Sports News – Local NCAA: Utah College Track & Field Roundup: 5/11 Written by Tags: Big Sky/Mountain West/Southern Utah/Utah Valley/WAC/Weber State FacebookTwitterLinkedInEmailMOSCOW, Idaho-Thursday, as the Big Sky track and field championships ensued, numerous Southern Utah and Weber State athletes excelled.In the women’s hammer throw, Northern Arizona’s Brooke Anderson took the crown with a toss of 227-9. Weber State’s Terrell Womack placed eighth overall with a toss of 166-10.In the women’s high jump, Weber State’s Abbigael Brecht had a leap of 5 feet 8 inches to win the conference title in this event.Her teammate, Eden Richards, tied for third with a leap of 5 feet 5 and 3/4 inches.In the men’s shot put, Idaho’s Zack Short took the title with a toss of 59 and 7 3/4 inches. Nick Benham of Weber State placed sixth and Southern Utah’s Cannon Brunsvik finished seventh.The women’s discus saw Molli Detloff of North Dakota place first and Weber State’s Sophie Merritt finish fifth.Cidnee Davies of Weber State won the women’s long jump with a leap of 19 9 3/4 feet. Another Wildcats’ conference title was won by Trey Devereaux in the men’s pole vault with a leap of 16 1 1/4 feet. His teammate, Keaton Pace, placed fifth in this event.In the men’s javelin, Jensen Lillquist of Montana took the conference title, while Southern Utah’s Skyler Porcaro and Jeff Rowley finished second and fourth, respectively.The men’s long jump title was won by Eastern Washington’s Keshun McGee with a leap of 24 10 1/2 feet.The men’s 3000-meter steeplechase title was won by Weber State’s Jordan Cross in 9:01.49 as Southern Utah’s Michael Finch placed third.In the women’s 3000-meter steeplechase, Sarah Medved of Portland State placed first in a time of 10:30.35 as Weber State’s Summer Harper finished fourth and Morgan Porcaro of Southern Utah finished sixth.The men’s 10,000-meter run title was won by Southern Utah’s Aidan Reed in a time of 30:04.06, as Matthew Wright, his teammate, placed second and Colton Rimann of Weber State placed sixth.Concluding action Thursday was the women’s 10,000-meter run with this title won by Southern Utah’s Angie Nickerson in a time of 35:04.29 with her teammate, Madison Fruchey placing fourth.After three days of competition, Montana State’s men are in the lead with 44 points, while the Southern Utah men are second with 41 points. Weber State is in third with 36 points.For the women, North Dakota is in first with 52 points while Weber State is in second with 37.5 points. Southern Utah is in seventh place with 19 points.LAWRENCE, Kan.-As Day 2 of the WAC track and field championships ensued, the team standings see Grand Canyon’s men’s and women’s teams currently in the lead. The Antelope women have 26 points, just ahead of second-place Utah Valley with 24 points. The Antelope men have 24 points and once again, Utah Valley is in second as the Wolverines have 16 points.In the men’s decathlon, Grand Canyon’s Grant Carpenter won the crown with 6486 points. Josh Thomas of Utah Valley finished fourth overall in the event.The women’s heptathlon was won by Ashley Krawczuk of Grand Canyon as she amassed 4672 points. Sara Ohlwiler of Utah Valley placed fourth with 4378 points.In the women’s 10,000-meter run, Olivia Stein of Seattle U. won the title in a time of 35:51.29. A trio of Utah Valley Wolverines took the second, third and fourth slots with McKayla Walker, Savannah Berry and Hannah Branch finishing in these respective slots.In the men’s 10,000-meter run, Missouri-Kansas City’s Nathan Keown took the crown in a time of 31:03.75. Utah Valley’s Tyson Lambert and Kevin Lynch placed third and fourth, respectively.The meet resumes Friday with Day 3.FRESNO, Calif.-As Day 2 of the Mountain West track and field championships unfolded at Fresno State Thursday, the women’s heptathlon saw history made.On her home track, Fresno State’s Jestena Mattson won the heptathlon with 5511 points, which is a new school record for the Bulldogs. Talie Bonds and Niki Xydona of Utah State placed seventh and eighth, respectively.For the men, Air Force’s Cavlin Berstler won the decathlon title, becoming the first Falcon to do so in 9 years. Berstler posted 7203 points. Thus, the second day of the Mountain West track and field championships saw numerous historic events occur, setting the stage for what should be a great third day of competition Friday.last_img read more

Pacific holds off Cougars on Senior Day

first_img Tags: Baseball/BYU Cougars/WCC FacebookTwitterLinkedInEmailPROVO, Utah — Pacific scored in the ninth to hold off the BYU baseball team 6-5 on Senior Day at Miller Park in the final game for both teams.The Cougars (22-28, 11-16 West Coast Conference) were outhit 11 to eight on the day and tallied three errors as the Tigers (22-29, 11-16 WCC) managed to stay on top throughout the game and take the series 2-1.Pacific didn’t take long to get on the board as two throwing errors sent a runner across home plate for a 1-0 lead in the first inning.Daniel Schneemann answered with a solo home run to center field to even the game at 1-all after one inning.In the second, a single to right field and another throwing error was followed by a double to left field to score both runners and increase the Tigers’ lead to 3-1.Brennon Anderson led off the third inning with a base hit to left field and with one out, Brock Hale walked. A passed ball advanced Anderson and Hale before a single to left field by Keaton Kringlen sent both runners home to tie the game at 3-3.Pacific responded in the fourth and sixth innings with two runs off singles to right field and shortstop, respectively, to take back the lead, 5-3.Kringlen tallied his second hit of the game in the sixth when he doubled up the middle. David Clawson followed with a double of his own down the right field line to send Kringlen home for the fourth run of the game, but BYU still trailed 5-4.Defensively, Casey Jacobsen, Anderson and Nate Favero combined for a double play to keep the Tigers from scoring in the seventh inning.Favero led off the eighth with a single up the middle and advanced to second off a sacrifice bunt by Kringlen. A wild pitch walked Mitch McIntyre and Favero scooted home to once again tie the game at 5-all.A double to right center field sent a runner home to give Pacific a 6-5 advantage and ultimately the win over the Cougars.BYU honored five seniors in the final game of the season: Anderson, Favero, Kendall Motes, Rhett Parkinson and Hayden Rogers.​ Written by May 19, 2018 /Sports News – Local Pacific holds off Cougars on Senior Day Robert Lovelllast_img read more