The study of global atmospheric pollution in Antarctica

first_imgWaste products from man’s activities, released into the environment, distribute themselves between the atmosphere, the land, the sea and, through these, to the biota. There is a constant interchange of material between reservoirs leading, it is thought, to an ultimate sinking of trace materials into the depths of the ocean where they slowly accumulate on the ocean bed and are removed from the circulation system. Substances released into the air can rise into the upper atmosphere and spread all over the world before they finally sediment into the lower atmosphere and suffer washout. The overall lifetime of a particular pollutant is determined by its concentration in each reservoir and by its rate of transfer between different pairs of reservoirs. A major goal for scientists is to achieve a quantitative description of this process for the major pollutants so that in the future it may be possible to predict the changing concentrations with time, in each reservoir, of a potentially harmful pollutant of known input rate into the environment.last_img read more

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Ion cyclotron absorption at the second harmonic of the oxygen gyrofrequency

first_imgThe ray paths of unstable electromagnetic waves generated inside the plasmapause during magnetic storm conditions are followed using the HOTRAY code. Unducted waves which are preferentially generated in the field aligned direction are rapidly refracted to large wave normal angles. At frequencies between the Oxygen and Helium gyrofrequencies the waves reflect once their frequency falls below the bi‐ion frequency and the waves subsequently bounce back and forth across the equator. The wave energy is ultimately absorbed by Landau resonance with plasmaspheric electrons or by second harmonic cyclotron resonance with thermal Oxygen; the latter being an important effect which has not previously been considered. Both processes may provide a significant heating mechanism for either population during storms.last_img read more

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Can high Arctic soil microarthropods survive eleveated summer temperatures?

first_img1. Tolerance of high summer temperatures was investigated in seven common species of oribatid mite (Acarina) and springtail (Collembola) found in soils associated with dominant vegetation types in West Spitsbergen, Svalbard. 2. Laboratory survival experiments are linked with field data from a 3-year temperature manipulation experiment to characterize the response of these animals to elevated field temperatures. 3. A 1-h exposure to 30⚬C under moist conditions showed that none of the species studied suffered significant mortality. The temperature required to kill all individuals was between 35-40 and 40-45⚬C for springtails and mites respectively. Under dry conditions at equivalent temperatures, differences in survival between mites and Collembola were strongly accentuated. Oribatid mites were little affected by the additional drought stress but the lethal temperature for springtails was shifted downwards by several degrees. 4. In parallel 3-h exposure experiments under moist conditions, the thermal death point was shifted downwards by c. 2.5⚬C in all the species, compared with 1-h exposures. Under dry conditions most Collembola died but mite survival differed little from that in the corresponding wet treatment over 3 h. 5. In longer-term experiments some mature Onychiurus arcticus survived more than 196 and 68 days at 5 and 25⚬C respectively. Above 30⚬C individuals survived for <24 h. 6. Regression relationships were established between maximum microhabitat temperatures and screen temperatures over 3 years. These were used to predict past maximum vegetation/litter mat and soil temperatures from historical screen data and to estimate the screen temperatures necessary to raise microhabitat temperatures to the thermal death point of the soil-dwelling arthropods. 7. The results are used to interpret the findings of a 3-year field experiment which examined the response of mite and springtail populations to temperature enhancement on two tundra sites, using small polythene tents. 8. High Arctic soil microarthropods appear able to cope with the higher summer temperatures they may experience as a result of climate change. It is the associated changes in soil moisture status that will probably produce the more significant changes in the microarthropod community. Species differ in their susceptibilities, but a decrease in soil moisture appears to favour oribatid mites at the expense of Collembola.last_img read more

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Quasi-biennial oscillation effects in the semidiurnal tide of the Antarctic lower thermosphere

first_imgA continuous 37-year record of the geomagnetic field from Argentine Islands Geomagnetic Observatory at Faraday research station (65°S, 64°W), Antarctica, has been analysed to reveal a 27-month periodicity in the amplitude of the semidiurnal Sq variation in the H-component significant at the 98% level. This indicates the presence of a periodicity in the strength of the semidiurnal tide at dynamo region altitudes matching that of the quasi-biennial oscillation (QBO) classically observed in the zonal stratospheric winds at equatorial latitudes. It adds to similar observations (Olsen, 1994) which demonstrated such an effect in the diurnal Sq range at near-equatorial latitudes but which showed no evidence for its presence at mid-latitudes. Faraday research station is in a uniquely advantageous geophysical location for such geographically high-latitude observations.last_img read more

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A unifying lithostratigraphy of late Cretaceous–early Tertiary fore-arc volcanic sequences on Alexander Island, Antarctica

first_imgLate Cretaceous–early Tertiary subduction-related fore-arc volcanic rocks are exposed in a north–south linear belt along the length of Alexander Island. The age and tectonic setting of these rocks is well understood; they are not considered to represent “normal” arc magmas but were generated in the fore-arc as a result of ridge subduction. Due to their distinct composition and mode of formation, they are no longer considered to be genetically related to the Antarctic Peninsula magmatic arc. They are therefore removed from the Antarctic Peninsula Volcanic Group and placed in a newly defined Alexander Island Volcanic Group. The group is made up of the Monteverdi, Staccato, Walton, Colbert, Elgar and Finlandia formations, which vary widely in lithology, facies and age. The Colbert and Elgar formations are subdivided into nine and three members respectively. Type localities, representative lithologies and age of each of the formations are discussed. The Staccato and Colbert Magmatic complexes are defined to include volcanic and plutonic rocks that are considered to be coeval. The Rouen Intrusive complex combines the plutonic rocks from the Rouen Mountains and Rothschild Island on the basis of age and chemistry.last_img read more

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Cephalopods of the South Georgia slope

first_imgDuring January 2003 the bathymetric distribution of the cephalopod fauna of the South Georgia and Shag Rocks slope (100-900 m) was investigated using a commercial bottom trawl. Forty-four trawl stations caught 193 cephalopod specimens including six species of octopod and seven of squid. The benthic octopods Pareledone turqueti and Adelieledone polymorpha were abundant in shallow water at South Georgia, being replaced by Thaumeledone gunteri in greater depths. However, neither A. polymorpha nor T gunteri were caught on the adjacent Shag Rocks area. Two specimens of the deep-sea genus Graneledone were caught on the South Georgia slope. The most abundant squid species caught were Moroteuthis knipovitchi, Psychroteuthis glacialis and Slosarczykovia circumantarctica, which are primarily pelagic and may have been taken when their vertical migrations impinged on the slope.last_img read more

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Recent rapid salinity rise in three East Antarctic lakes

first_imgResearch in East Antarctica has shown several recent environmental changes that may be linked to human impacts on climate. In order to detect the influence and context of these changes on coastal aquatic ecosystems we examined lake sediment cores from three lakes in the Windmill Islands, East Antarctica; Beall Lake, Holl Lake and ȁ8Lake Mȁ9. Cores were sectioned at␣2.5 mm intervals. Their diatom species composition was examined to detect changes in lake salinity using a diatom-salinity transfer function, and their algal pigment content was examined to detect photoautotrophic community responses to environmental change. Results showed that Holl Lake originated in a depression exposed by Holocene recession of the continental ice sheet and that Beall Lake and Lake M originated as isolated marine basins formed by changes in relative sea level. A general late Holocene trend of declining lake salinity was evident in all three lakes, interrupted by one short-term high salinity event in Beall Lake. This is consistent with a long-term positive moisture balance. This general decline in salinity has been followed by a remarkable recent rapid increase in salinity in all three lakes in the last few decades. We speculate that this rapid increase in salinity might be linked to changes taking place in the region including feedbacks resulting from decreasing sea ice extent as recorded in the nearby Law Dome ice core, and positive feedbacks in the catchments whereby reduced snow cover has led to decreased albedo, which in turn has caused increased evaporation and sublimation. Collectively these changes have shifted the lakes across a threshold from positive to negative moisture balance. A minor, but not rapid shift in the abundance of diatom pigments relative to pigments from green algae and cyanobacteria was also detected suggesting that some changes in photoautotrophic community composition have occurred. Measurements of modern nutrient levels are also higher than would be expected in Beall Lake and Holl Lake, given the extremely low sediment accumulation rates. This may be associated with a c. 300% increase in the population of Adélie penguins in the Windmill Islands recorded since the 1950s, or may a first signs of a rapid increase in catchment development and associated lake productivity as experienced in Antarctic and Arctic lakes subject to recent rapid regional warming. The most marked feature of the records is the rapid increase in salinity in all three lakes in␣the last few decades, which has occurred in lakes both with and without resident penguin populations.last_img read more

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Greenland: Bringing together remote sensing and fieldwork.

first_imgWith global land and sea temperatures rising, the importance of accurate monitoring of the world’s ice sheets is increasing. Satellite radar altimetry can be used to measure elevation changes of ice sheets from which mass balance can be derived. In the percolation zone of ice sheets, summer melt which percolates into the snowpack and refreezes causes a re-distribution of mass through densification, which can result in elevation changes which are not representative of changes in mass balance. We present data collected in the percolation zone of the Greenland Ice Sheet prior to and post the processes of summer melt, percolation and refreezing. Data from nine sites along two 1-km transects show that in 2004 there was a 31.6% increase in accumulation over the summer, but due to surface melting percolation and refreezing the average snowpack density increased by 26.2%, resulting in only a 5.3% increase in elevation. Our results indicate that in areas of substantial seasonal melt and refreezing, densification rates must be accurately quantified if mass balance estimates are to be usefully derived from surface elevation change.last_img read more

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Geolocation tracking of the annual migration of adult Australasian gannets (Morus serrator) breeding in New Zealand

first_imgThe long breeding period and high reproductive investment of seabirds make use of resource-rich foraging areas pivotal both during and between breeding seasons. We tracked adult Australasian Gannets (Morus serrator) from their New Zealand breeding colony at Cape Kidnappers to Australia during the non-breeding period to assess wintering behavior and migratory routes for this species. Data from three recovered geolocation sensor (GLS) tags showed that both a male and a female M. serrator, and a hybrid M. capensis × M. serrator migrated across the Tasman Sea to winter in Australian and Tasmanian coastal waters. Tracked birds covered distances of up to 13,000 km on their migration. These movements were consistent with historical records of band recoveries.last_img

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Vertical structure of Antarctic tropospheric ozone depletion events: characteristics and broader implications

first_imgThe majority of tropospheric ozone depletion event (ODE) studies have focussed on time-series measurements, with comparatively few studies of the vertical component. Those that exist have almost exclusively used free-flying balloon-borne ozonesondes and almost all have been conducted in the Arctic. Here we use measurements from two separate Antarctic field experiments to examine the vertical profile of ozone during Antarctic ODEs. We use tethersonde data to probe details in the lowest few hundred meters and find considerable structure in the profiles associated with complex atmospheric layering. The profiles were all measured at wind speeds less than 7 ms(-1), and on each occasion the lowest inversion height lay between 10 m and 40 m. We also use data from a free-flying ozonesonde study to select events where ozone depletion was recorded at altitudes > 1 km above ground level. Using ERA-40 meteorological charts, we find that on every occasion the high altitude depletion was preceded by an atmospheric low pressure system. An examination of limited published ozonesonde data from other Antarctic stations shows this to be a consistent feature. Given the link between BrO and ODEs, we also examine ground-based and satellite BrO measurements and find a strong association between atmospheric low pressure systems and enhanced BrO that must arise in the troposphere. The results suggest that, in Antarctica, such depressions are responsible for driving high altitude ODEs and for generating the large-scale BrO clouds observed from satellites. In the Arctic, the prevailing meteorology differs from that in Antarctica, but, while a less common effect, major low pressure systems in the Arctic can also generate BrO clouds. Such depressions thus appear to be fundamental when considering the broader influence of ODEs, certainly in Antarctica, such as halogen export and the radiative influence of ozone-depleted air masses.last_img read more

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