Survey reduction for glacier movement studies

first_imgSurveys of glaciers require special reduction techniques because of the continuous movement of ice. In the past, a minimum of two surveys of a network was needed to determine glacier velocities. A new approach is discussed in this paper. It uses conventional observation equations but allows station co-ordinates and observations to be time dependent. By selecting, a suitable network, a single adjustment of measurements made on different occasions can produce ice movement parameters even from a single survey.last_img

1000 year ice-core records from Berkner Island, Antarctica

first_imgTwo medium-depth ice cores were retrieved from Berkner Island by a joint project between the Alfred-Wegener-Institut and the British Antarctic Survey in the1994/95 field season. A151mdeep core from the northern dome (Reinwarthho«he) of Berkner Island spans 700 years, while a 181m deep core from the southern dome (Thyssenho«he)spans approximately 1200 years. Both cores display clear seasonal cycles in electrical conductivity measurements, allowing dating by annual-layer counting and the calculation of accumulation profiles. Stable-isotope measurements (both d18O and dD), together withthe accumulation data, allow us to estimate changes in climate for most of the past millennium: the data show multi-decadal variability around a generally stable long-term mean. In addition, a full suite of major chemistry measurements is available to define the history ofaerosol deposition at these sites: again, there is little evidence that the chemistry of the sites has changed over the past six centuries. Finally, we suggest that the southern dome, with an ice thickness of 950m, is an ideal site from which to gain a climate history of the late stages of the last glacial and the deglaciation for comparison with the records from the deep Antarcticice cores, and with other intermediate-depth cores such as Taylor Dome and Siple Dome.last_img read more

A minimal substorm model that explains the observed statistical distribution of times between substorms

first_imgA minimal model for the evolution of the global dynamical state of the magnetotail during the substorm has been developed, involving only three simple rules and one free parameter D-the period between substorms under constant solar wind driving. The model is driven with a power input derived from solar wind observations from the Wind spacecraft between 1995 and 1998, to derive a sequence of simulated substorm onsets. For values of D between 2.6 h and 2.9 h, the probability distribution of waiting times between successive simulated substorm onsets is not significantly different to an empirical distribution derived from energetic particle observations at geostationary orbit in 1982-3. Similar results are obtained using solar wind data from the ACE spacecraft between 1998 and 2002. Thus, we argue that the minimal substorm model provides a useful statistical and physical description of the timing of substorm onsets and possibly other substorm properties.last_img read more

Circulation and melting beneath George VI Ice Shelf, Antarctica

first_imgOceanographic data are presented from the eastern Bellingshausen Sea, representing the first near-contemporaneous sampling of conditions near both the northern and southern ice fronts of George VI Ice Shelf. Circumpolar Deep Water (CDW) with a temperature in excess of 1 degrees C floods the entire continental shelf and forms the main inflow to the cavity beneath the ice shelf. We use measurements of salinity, potential temperature, stable isotope ratios and dissolved oxygen, helium, and neon to show that the outflows contain meltwater in concentrations that rise to a maximum of around 3%. Assuming that the currents are in geostrophic balance, we calculate relative velocities along the ice front sections, then estimate the absolute velocity by inversion of the tracer conservation equations. We obtain an overall mean melt rate of 3-5 m a(-1) and a net south-to-north throughflow beneath the ice shelf of 0.17-0.27 Sv. The mean melt rate exceeds that required for equilibrium, consistent with recent observations of ice shelf thinning and retreat. Melting beneath the ice shelf drives upwelling of about 0.1 Sv in total of CDW into the surface mixed layer at the two ice fronts. The effective vertical heat flux per unit area of ice shelf cover is 8 W m(-2), more than 4 times that estimated for vertical diffusion through the main pycnocline of the neighboring open water region. The south-to-north throughflow carries a particularly strong signature of upwelled CDW, including low dissolved oxygen and high nutrient concentrations, north into Marguerite Bay.last_img read more

Coupling of climate models and ice sheet models by surface mass balance gradients: application to the Greenland Ice Sheet

first_imgIt is notoriously difficult to couple surface mass balance (SMB) results from climate models to the changing geometry of an ice sheet model. This problem is traditionally avoided by using only accumulation from a climate model, and parameterizing the meltwater run-off as a function of temperature, which is often related to surface elevation (Hs). In this study, we propose a new strategy to calculate SMB, to allow a direct adjustment of SMB to a change in ice sheet topography and/or a change in climate forcing. This method is based on elevational gradients in the SMB field as computed by a regional climate model. Separate linear relations are derived for ablation and accumulation, using pairs of Hs and SMB within a minimum search radius. The continuously adjusting SMB forcing is consistent with climate model forcing fields, also for initially non-glaciated areas in the peripheral areas of an ice sheet. When applied to an asynchronous coupled ice sheet – climate model setup, this method circumvents traditional temperature lapse rate assumptions. Here we apply it to the Greenland Ice Sheet (GrIS). Experiments using both steady-state forcing and glacial-interglacial forcing result in realistic ice sheet reconstructions.last_img read more

High abundances of microplastic pollution in deep-sea sediments: evidence from Antarctica and the Southern Ocean

first_imgPlastic pollution in Antarctica and the Southern Ocean has been recorded in scientific literature since the 1980s; however, the presence of microplastic particles (<5 mm) is less understood. Here, we aimed to determine whether microplastic accumulation would vary among Antarctic and Southern Ocean regions through studying 30 deep-sea sediment cores. Additionally, we aimed to highlight whether microplastic accumulation was related to sample depth or the sediment characteristics within each core. Sediment cores were digested and separated using a high-density sodium polytungstate solution (SPT) and microplastic particles were identified using micro-Fourier-transform infrared spectroscopy (μFTIR). Microplastic pollution was found in 93% of the sediment cores (28/30). The mean (±SE) microplastics per gram of sediment was 1.30 ± 0.51, 1.09 ± 0.22, and 1.04 ± 0.39 MP/g, for the Antarctic Peninsula, South Sandwich Islands, and South Georgia, respectively. Microplastic fragment accumulation correlated significantly with the percentage of clay within cores, suggesting that microplastics have similar dispersion behavior to low density sediments. Although no difference in microplastic abundance was found among regions, the values were much higher in comparison to less remote ecosystems, suggesting that the Antarctic and Southern Ocean deep-sea accumulates higher numbers of microplastic pollution than previously expected.last_img read more

BYU baseball series concludes at UVU and WCC road play begins

first_img FacebookTwitterLinkedInEmailAs the month of March concludes, BYU baseball finishes its series with Utah Valley and plays its first league road games with three games at Pepperdine.Tuesday’s 6 p.m. MDT game at UVU will likely be an all-staff day for the pitching rotation for both teams in the UCCU Crosstown Clash. UVU has a 9-12 record and will start Paxton Schultz (1-1, 5.84). BYU is 12-9 and will start Bo Burrup (1-1, 11.45). Pepperdine is 10-13. The Cougars and the Waves each have 2-4 records in the West Coast Conference.“Utah Valley is always a big game for us,” BYU coach Mike Littlewood said. “Traditionally, we haven’t played well against Pepperdine. It will be a challenge at Pepperdine because we have put ourselves in a situation where we need to beat good teams on the road.“I was proud of the way our guys played last week. We are resilient and saw some good things. We came out of our corner fighting, and that’s all I can ask of our team,” Littlewood said after an 11-game home stand.BYU will likely continue its pitching rotation at Pepperdine of having Jordan Wood (2-1, 3.43), Hayden Rogers (3-2, 5.14) and Blake Inouye (1-2, 6.04) as starters in games Thursday and Friday at 3 p.m. PDT and on Saturday at 1 p.m.The Cougars posted a 3-4 record since beating UVU 9-3 earlier this month, while the Wolverines have won four of their last six games.​ Tags: Baseball/BYU Cougars/UVU Wolverines/WCC Written by Robert Lovell March 26, 2018 /Sports News – Local BYU baseball series concludes at UVU and WCC road play beginslast_img read more

The eagle has landed — on a baseball player during the national anthem

first_imgApril 5, 2018 /Sports News – National The eagle has landed — on a baseball player during the national anthem Beau Lund FacebookTwitterLinkedInEmailiStock/Thinkstock(MINNEAPOLIS) — Maybe the Eagle knew James Paxton was Canadian.During the national anthem at Thursday afternoon’s home opener for the Minnesota Twins, an eagle may have mistaken the Mariners pitcher for its handler as it tried landing on Paxton’s shoulder.Paxton was standing alone in left field, clutching his cap to his chest, when the bird, named Challenger, circled around him a few times and attempted to land awkwardly on his right, non-throwing, shoulder.“Challenger simply thought the pitcher was one of his handlers standing near the large U.S. flag in the outfield ready to catch him and give him a piece of salmon,” the American Eagle Foundation said in a statement Thursday night.The 28-year-old Challenger has performed at 12 World Series games, five BCS National Championships and dozens of other high-profile events. This is the bird’ first public mishap.“The sharp points on the tip of Challenger’s talons are always blunted before his performances at major sporting events,” the foundation added.Paxton was unharmed. He pitched five strong innings, but the Twins prevailed 4-2.“I wasn’t going to run,” Paxton said after the game. “I figured I’m not going to outrun an eagle, so we might as well just see what happens.”Copyright © 2018, ABC Radio. All rights reserved.center_img Written bylast_img read more

Idaho youth football team lifts overturned car to rescue trapped couple

first_img Written by Beau Lund May 31, 2018 /Sports News – National Idaho youth football team lifts overturned car to rescue trapped couplecenter_img FacebookTwitterLinkedInEmailRegan Magill via Storyful(JORDAN VALLEY, ORE.) — A youth football team helped rescue an Oregon couple trapped in an overturned car on Wednesday, possibly saving their lives.A member of the Boise Black Knights football team shared video of the moment on social media after he and his teammates pulled the man free and lifted the vehicle to rescue the woman stuck inside.Several of the boys were seen raising the vehicle as other team members worked to cut the woman out of her seat belt and pull her from the wreckage.The team members were on their way home from a tournament in California when they came across the crash scene on an Oregon highway, according to Black Knights coach Rudy Jackson of Boise, Idaho.That’s when the players — age 13 and younger — quickly jumped into action.“We were all driving. They came around the corner and seen an accident with a car rolled over, and the two vans pulled over,” Jackson said in an interview with ABC News’ Good Morning America on Thursday. “Me right now talking about it — I’m getting emotional, because I’ve watched these boys grow. And they came a long way. They’re amazing young men.”Regan Magill, the team member who helped capture the footage, said Jackson is the one who deserves credit for rescuing the couple, noting his lessons on the importance of selflessness.“He taught us to play selfless football and not selfish — just help others out before yourself,” Magill told Good Morning America.There was no official word on the couple’s condition.Copyright © 2018, ABC Radio. All rights reserved.last_img read more

Van Dyke’s career-high 23 carries Utah over Arizona, 83-76

first_img Associated Press The Wildcats are 13-2 against Utah since Sean Miller became the head coach at Arizona. The Wildcats outlasted Utah 84-81 in overtime on Jan. 5. Ten of those contests have been decided by single digits. Tags: Pac 12/Parker Van Dyke/Utah Runnin’ Utes Basketball Utah didn’t score during the first four minutes of the game, until just after Van Dyke — whose 3-point buzzer-beater stunned UCLA last Saturday — checked into the game and hit a shot from the corner. Dylan Smith scored a season-high with 16 points and Ryan Luther had 14 for the Wildcats (14-11, 5-7), who have lost six in a row for the first time since former coach Lute Olson’s first season at Arizona in 1983-84. UP NEXT February 14, 2019 /Sports News – Local Van Dyke’s career-high 23 carries Utah over Arizona, 83-76 Sedrick Barefield had 15 points and six assists and Timmy Allen scored 14 for the Utes (14-10 overall, 8-4 Pac-12), who have won three in a row and are in second place in the conference. The Wildcats got within five points in the final minute but Both Gach made four straight free throws in the final 13 seconds to clinch the win. Neither team led by more than Arizona’s 32-26 margin in the first half until Utah went on a 18-2 run in the second half, sparked by Van Dyke’s shooting and Johnson’s strong play at the rim. Johnson’s follow basket with 7:03 to play gave Utah a 66-51 lead. Utah’s center barely touched the ball on offense in the first half but dominated the paint in the second half, scoring all of his points. Johnson added 10 rebounds, marking the fifth straight game he has notched double figures on the boards. Utah hosts Arizona State on Saturday. FacebookTwitterLinkedInEmailSALT LAKE CITY (AP) — Parker Van Dyke made seven 3-pointers and scored a career-high 23 points and Jayce Johnson also set a career-best with 17 points to help Utah beat Arizona 83-76 on Thursday night. Written by Arizona continues its mountain swing at Colorado on Sunday.last_img read more