Month: May 2021

An error in ice-temperature measurement

first_imgAn analysis is made of the disturbance in conductive heat flow caused by drilling a bore hole in ice in which there is a vertical temperature gradient. The model used is that of a perfectly insulating hole placed in a linear temperature gradient; it is shown that the temperature measured at the bottom of the hole deviates from its value before drilling by an amount of order —0.6aU where a is the bore-holt radius and U is the temperature gradient. The deviation takes effect in a few hours. The error is typically between 0.005 and 0.1 deg and is therefore significant only where very high accuracy is required. It should not be present in temperate glaciers, nor where the thermometer is properly frozen in, nor if temperatures are measured at the bore-hole walls far above the bottom.last_img read more

Lipid in an arctic food chain: Calanus, Bolinopsis, Beroe

first_imgThe zooplankton of the fjords of Svalbard in late summer is dominated by copepodites of Calanus glacialis (JASCHNOV). These are consumed by, among others, the lobate ctenophore Bolinopsis infundibulum (O.F. MÜLLER), which is in turn preyed upon by the larger ctenophore Beroe cucumis (FABRICIUS). This simple food chain enables the fate of different lipid classes or fatty acids to be followed from prey to predator. Calanus glacialis, Bolinopsis infundibulum, and Beroe cucumis were sampled from Raudfjorden, Svalbard (79°50′ N, 12°10′ E) in August 1984 and their lipid composition analysed in detail. All three species were rich in lipid and between 50 and 75 % of this lipid was wax ester. The fatty acid composition of this wax ester was different in the three species, with very little similarity in composition between predator and prey in either Calanus/Bolinopsis or Bolinopsis/Beroe. Phospholipid fatty acid composition was also species-specific. Triacylglycerol formed only 2 to 8 % of the total lipid but the fatty acid composition of this triacylglycerol was almost identical in all three species. It is concluded that in the absence of supportive biological information, simple statistical analyses of fatty acid spectra are of limited value in establishing trophic relationship in pelagic marine food webs, although specific individual lipid components may be useful in certain contexts.last_img read more

Pre-natal investment in reproduction by female Antarctic fur seals

first_imgMaternal investment, in terms of pup birth mass, in gestation by Antarctic fur seals (Arctocephalus gazella) was related to the date of birth in two consecutive years. There were significant differences in birth mass between years and between the sexes within years. Birth mass was used to calculate the mean energetic cost of producing a pup to parturition. The cost for a male pup in 1986 was 173 MJ while it was 191 MJ in 1987. For female pups the cost was 152 and 166 MJ in 1986 and 1987 respectively. Given the probable pattern of foetal growth, this constitutes a minimum of 5–15% of the maternal energy budget in the final months of gestation. Birth mass varied inversely with date of birth, but more strongly for male than for female pups. The sex ratio at birth was unity in both years and this did not vary with time through the birth season. In a subsample of mothers (n=79) which were captured on the day of birth, there was a decline in the body mass and standard length with date of birth. Male birth mass was directly related to maternal mass and maternal condition (mass/length) but there was no significant relationship for females. These results suggest that the growth of male foetuses is limited by maternal resources while female foetuses do not exploit fully maternal resources.last_img read more

The intense magnetic storm of December 19, 1980: Observations atL= 4

first_imgThe intense magnetic storm of December 19, 1980 occurred during a major rocket and balloon geophysical research campaign at Siple Station, Antarctica. A balloon flight measuring the electric field and bremsstrahlung X ray flux was conducted during the main phase of the storm. The balloon data and associated ground‐based data from around the world contain several lines of evidence which indicate that the dayside auroral oval expanded to an invariant latitude ≤59° during the storm. Evidence for this conclusion includes (1) the pattern of ground‐based magnetic field and ionospheric electric field perturbations; (2) a substantial departure from the normal diurnal curve of the vertical component of the electric field in the stratosphere; and, (3) identical, relatively rapid equatorward motion of regions of electron precipitation, observed or inferred to occur, simultaneously at three L ∼ 4 stations: Siple, Halley Bay and SANAE, separated by several hours in local time across the dayside. The absence of electron precipitation at Siple after this equatorward motion is an indication that the polar cap had expanded to include Siple during this interval. The power spectra of the magnetic field fluctuations at ULF observed at Siple and in a conjugate latitude chain of magnetometers were consistent with the presence of the dayside auroral oval in the near vicinity of Siple and with the presence of a major magnetospheric boundary slightly equatorward of ∼59°. The stratospheric electric field measured during the recovery phase was very large for this latitude for a period of several hours. This observation suggests that a subauroral latitude ion drift event of unusual intensity and duration accompanied this storm.last_img read more

Cold acclimation and cryoprotectants in a freeze-tolerant Antarctic nematode, Panagrolaimus davidi

first_imgPanagrolaimus davidi is a freeze-tolerant Antarctic nematode which survives extensive intracellular freezing. This paper describes the development of culture techniques which provide clean samples, with a high degree of freeze tolerance and in sufficient quantities for the analysis of potential cryoprotectants. Cultures grown at 20 °C survived a short-term freezing stress but survival declined with the time spent frozen. Acclimation of cultures at 5 °C enhanced the long-term survival of freezing. Starvation, however, reduced the nematode’s ability to survive short-term freezing. The principal cryoprotectants detected by gas chromatography were trehalose and glycerol. The levels of trehalose, but not those of glycerol, increased significantly after acclimation. Trehalose may stabilise membranes and protect them against the dehydrating effects of the osmotic stresses resulting from freeze concentration effects but other factors, such as recrystallisation inhibition, may be involved in long-term survival.last_img read more

The thermophilic bryoflora of Deception Island: unique plant communities as a criterion for designating an Antarctic Specially Protected Area

first_imgDeception Island in the South Shetland Islands is one of the most volcanically active sites south of 60°S. Between 1967 and 1970 three major eruptions devastated large expanses of the landscape and its vegetation. Since 1970 extensive recolonization has occurred on the more stable surfaces. Unheated ground supports several bryophyte and lichen communities typical of much of the Maritime Antarctic, but geothermal habitats possess remarkable associations of bryophytes, many of which are unknown or very rare elsewhere in the Antarctic. Nine geothermal sites and their vegetation are described. Communities associated with more transient sites have disappeared when the geothermal activity ceased. Mosses and liverworts occur to within a few centimetres of the vents where temperatures reach 90–95°C, while temperatures within adjacent moss turf can reach 35–50°C or more and remain consistently between 25 and 45°C. Most of the bryoflora has a Patagonian–Fuegian provenance. It is presumed that, unlike most species, the thermophiles are not pre-adapted to the Antarctic environment, being able to colonize only where the warm and humid conditions prevail. The floristic and ecological importance of these thermophilic communities, and their sensitivity to perturbation by the rapidly increasing annual summer influx of tourists, as well as scientists, has resulted in these unique sites being proposed as components of a new Antarctic Specially Protected Area under the Antarctic Treaty.last_img read more

Distribution of post-weaning Antarctic fur seal Arctocephalus gazella pups at South Georgia

first_imgPotentially some of the biggest gaps in our knowledge about the ecology of Antarctic fur seals (Arctocephalus gazella) relate to juvenile animals. We investigated the at-sea distribution of five male and five female fur seal pups post-weaning. The study was carried out at Bird Island, South Georgia during two successive winters using satellite-linked platform transmitter terminals (PTTs). Our results are analysed in relation to pup sex and the physical environment and productivity of those 2 years, as well as in the context of our present knowledge of where post-breeding females and males forage. The available physical and biological data during both of the winters of this study suggest that both years were not unusual. We report marked differences between the sexes with male pups foraging significantly further away from land and their birth site than do females. The pups foraged in areas to the East of Bird Island seldom reported as foraging areas for the adult population. Also as winter progressed they showed a more oceanic distribution leaving the continental shelf, possibly to exploit a different prey source that was more readily available in the upper water column.last_img read more

Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation

first_imgThe history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies.last_img read more

Scoreboard roundup — 10/31/18

first_imgNovember 1, 2018 /Sports News – National Scoreboard roundup — 10/31/18 Beau Lund Written bycenter_img FacebookTwitterLinkedInEmailiStock/Thinkstock(NEW YORK) — Here are the scores from Wednesday’s sports events:NATIONAL BASKETBALL ASSOCIATIONBrooklyn 120, Detroit 119Minnesota 128, Utah 125Denver 108, Chicago 107Indiana 107, N.Y. Knicks 101Golden State 131, New Orleans 121San Antonio 120, Phoenix 90L.A. Lakers 114, Dallas 113NATIONAL HOCKEY LEAGUEVancouver 4, Chicago 2MAJOR LEAGUE SOCCERNew York City 3, Philadelphia 1Copyright © 2018, ABC Radio. All rights reserved.last_img read more

NFL games could be affected by raging wildfires in California

first_img Written by Beau Lund November 11, 2018 /Sports News – National NFL games could be affected by raging wildfires in Californiacenter_img FacebookTwitterLinkedInEmailiStock/Thinkstock(LOS ANGELES) — As wildfires in California rage on, three National Football League games are scheduled to take place in the state between Sunday and Monday, but plans could change as the NFL monitors concerns over air pollution due to smoke.Amid worries over poor air quality at the games, NFL spokesman Brian McCarthy told ABC News that “at this point, all games will kick off as scheduled,” but league officials are “monitoring conditions in California and are in close communication with the clubs and local authorities.”The Seattle Seahawks vs. Los Angeles Rams game is expected to take place at Los Angeles Memorial Coliseum, and the Los Angeles Chargers will play the Oakland Raiders at the Oakland Coliseum on Sunday afternoon.According to ESPN, the Rams canceled practice on Friday and the Raiders were limited to a walkthrough due to the fires.Meanwhile, the New York Giants vs. the San Francisco 49ers game is expected to take place in Levi’s Stadium in Santa Clara on Monday night.At least 23 people have been killed this week as flames from the wildfires engulfed their vehicles, homes and neighborhoods in Northern California, authorities said.There were more 100 people missing in the region, but by Saturday, officials added that at least 70 people reported missing were located and are now safe.Gov. Jerry Brown requested a presidential major disaster declaration to “bolster the ongoing emergency response and help residents recover from devastating fires burning in Butte, Los Angeles and Ventura counties,” his office announced on Sunday.Butte County is in the north, while Los Angeles and Ventura counties are in the southern part of the state.The governor’s request comes a day after President Trump blamed “gross mismanagement of the forests” in California for the trio of deadly wildfires, and threatened to withhold federal funding to assist the flame-ravaged state.“There is no reason for these massive, deadly and costly forest fires in California except that forest management is so poor. Billions of dollars are given each year, with so many lives lost, all because of gross mismanagement of the forests. Remedy now, or no more Fed payments!” Trump tweeted on Saturday.When asked about the president’s tweets, Evan Westrup, the governor’s press secretary, told ABC News on Sunday: “Our focus is on the Californians impacted by these fires and the first responders and firefighters working around the clock to save lives and property — not on the president’s inane and uninformed tweets.”In August, wildfires in California broke records after the Mendocino Complex Fire became the largest in the state’s recorded history. Copyright © 2018, ABC Radio. All rights reserved.NFL games could be affected by raging wildfires in Californialast_img read more