Author: admin Page 1 of 405

Conservation and the Antarctic environment: The working group reports of the joint IUCN/SCAR Symposium on the scientific requirements for Antarctic conservation

first_imgSix working groups were set up at the joint IUCN/SCAR Symposium on the scientific requirements for Antarctic conservation. These were charged with (i) identifying gaps in the scientific understanding of ecosystems that inhibit rational management, and (ii) considering whether present conservation practices were taking enough account of what is known of the region, particularly with regard to protected areas. There is still a need for synthesis and further work on stocks and the life history of krill in the pelagic ecosystem. Monitoring strategies are not clear and biomass determinations are difficult and costly. Information on squid is lacking. Although there is much information on higher consumers there is a gap in knowledge of dynamic ecological processes, particularly in winter. Studies of crabeater seals deserve priority. The network of existing protected areas is inadequate for preserving all species of birds, seals and whales; new criteria are needed for effective conservation. On land, the Agreed Measures provide an adequate framework for conservation, though additional steps are needed to ensure adherence to their provisions. Selection criteria are deficient. Additional measures are required; these include the establishment of Conservation Areas, general provision for the protection of biota, and a code of conduct for all activities. Exploitation of marine mammals (except the minke whale) has ceased. Monitoring whales presents difficulties. Fish stocks are significantly exploited and better monitoring is required. Prediction of trends in krill catches is difficult but there has been a large drop in krill fishing effort. Localised effects on predators could occur with catches of a few million metric tons. Commercial mineral exploitation in the Antarctic is a long way in the future but exploitation could result from political motives. There is a need for a data base for the design of investigations and impact assessment. Operational hazards need to be modelled in advance. It is important not to go too far too fast. Antarctica is unique in its control measures and their implementation. However, Specially Protected Areas lack management plans and management plans at Sites of Special Scientific Interest are not consistent. There are inadequate guidelines on the development of scientific stations. The coastal region must be regarded as critical habitat. A comprehensive conservation strategy is required with a broader network of protected areas giving full consideration to marine as well as terrestrial areas. Copies of the full working group reports have been deposited with IUCN and SCAR.last_img read more

The diet of white-chinned petrels Procellaria aequinoctialis, Linnaeus 1758, in years of contrasting prey availability at South Georgia

first_imgThe diet of breeding white-chinned petrels was studied during the summers of 1996 and 1998 at South Georgia. Krill abundance/availability was high throughout 1996 but apparently low at the beginning of the 1998 breeding season. The diet of white-chinned petrels was similar between years and consistent with previous studies. Krill Euphausia superba (41–42% by weight) was the single most important prey item followed by fish (39–29%) and squid (19–25%). Meal mass was consistent (110 g in 1996, 119 g in 1998) between years but a significant decrease (46%) in feeding frequency in 1998 (0.54 meals day−1 compared to 0.75 meals day−1 in 1996) resulted in 19% less food delivered to chicks in 1998 than in 1996. Breeding success, however, was consistent between years at 44% and similar to that recorded previously at Bird Island. This is in contrast to black-browed and grey-headed albatrosses, both of which experienced almost total breeding failure in 1998. It is suggested that their varied and versatile feeding methods, together with their greater diving ability, capacity to feed at night and extensive foraging range, help white-chinned petrels minimise the effects of krill shortage.last_img read more

Publications and theses on Antarctic and sub-Antarctic birds, 1997

first_imgIn 1986, the Bird Biology Subcommittee of the ScientificCommittee on Antarctic Research (SCAR) Working Group onBiology recommended that a list of recent publications on Antarctic and sub-Antarctic seabirds species from 1986 be prepared. The 1997 list, the twelfth to be produced and published in Marine Ornithology, has been compiled by scanning the relevant literature and abstracting services, and by correspondence with members of the subcommittee. Readers are requested to send reprints of their recent relevant literature, including ones missing from this or previous lists, to the author for inclusion in subsequent lists.last_img read more

The regurgitation of stomach contents in trawl caught whiting, evidence of a predator size effect

first_imgThe rate of regurgitation of food from the stomachs of trawl caught whiting Merlangius merlangus was negatively correlated with fish size. Increased musculature of the oesophageal sphincter in larger fish may enable them to resist the forced expulsion of their stomach contents to a greater extent.last_img

Anatomy of a Dansgaard-Oeschger warming transition: High-resolution analysis of the North Greenland Ice Core Project ice core

first_imgLarge and abrupt temperature oscillations during the last glacial period, known as Dansgaard‐Oeschger (DO) events, are clearly observed in the Greenland ice core record. Here we present a new high‐resolution chemical (2 mm) and stable isotope (20 mm) record from the North Greenland Ice Core Project (NGRIP) ice core at the onset of one of the most prominent DO events of the last glacial, DO‐8, observed ∼38,000 years ago. The unique, subannual‐resolution NGRIP record provides a true sequence of change during a DO warming with detailed annual layer counting of very high depth resolution geochemical measurements used to determine the exact duration of the transition. The continental ions, indicative of long‐range atmospheric loading and dustiness from East Asia, are the first to change, followed by the snow accumulation, the moisture source conditions, and finally the atmospheric temperature in Greenland. The sequence of events shows that atmospheric and oceanic source and circulation changes preceded the DO warming by several years.last_img read more

Shifting ocean carbonate chemistry during the Eocene-Oligocene climate transition: implications for deep ocean Mg/Ca paleothermometry

first_imgTo date, no conclusive evidence has been identified for intermediate or deep water cooling associated with the > 1 parts per thousand benthic delta O-18 increase at the Eocene-Oligocene transition (EOT) when large permanent ice sheets first appeared on Antarctica. Interpretation of this isotopic shift as purely ice volume change necessitates bipolar glaciation in the early Oligocene approaching that of the Last Glacial Maximum. To test this hypothesis, it is necessary to have knowledge about deep water temperature, which previous studies have attempted to reconstruct using benthic foraminiferal Mg/Ca ratios. However, it appears likely that contemporaneous changes in ocean carbonate chemistry compromised the Mg/Ca temperature sensitivity of benthic foraminifera at deep sites. New geochemical proxy records from a relatively shallow core, ODP Site 1263 (estimated paleodepth of 2100 m on the Walvis Ridge), reveal that carbonate chemistry change across the EOT was not limited to deep sites but extended well above the lysocline, critically limiting our ability to obtain reliable estimates of deep-ocean cooling during that time. Benthic Li/Ca measurements, used as a proxy for [CO32-], suggest that [CO32-] increased by similar to 29 mu mol/kg at Site 1263 across the EOT and likely impacted benthic foraminiferal Mg/Ca. A [CO32-]-benthic Mg/Ca relationship is most apparent during the early EOT when the overall increase in [CO32-] is interrupted by an apparent dissolution event. Planktonic d18O and Mg/Ca records suggest no change in thermocline temperature and a delta O-18(seawater) increase of up to 0.6 parts per thousand at this site across the EOT, consistent with previous estimates and supporting the absence of extensive bipolar glaciation in the early Oligocene.last_img read more

Modification of turbulent dissipation rates by a deep Southern Ocean eddy

first_imgThe impact of a mesoscale eddy on the magnitude and spatial distribution of diapycnal ocean mixing is investigated using a set of hydrographic and microstructure measurements collected in the Southern Ocean. These data sampled a baroclinic, mid-depth eddy formed during the disintegration of a deep boundary current. Turbulent dissipation is suppressed within the eddy, but is elevated by up to an order of magnitude along the upper and lower eddy boundaries. A ray-tracing approximation is employed asa heuristic device to elucidate how the internal wave field evolves in the ambient velocity and stratification conditions accompanying the eddy. These calculations are consistent with the observations, suggesting reflection of internal wave energy from the eddy center and enhanced breaking through critical layer processes along the eddy boundaries. These results have important implications for understanding where and how internal wave energy is dissipated in the presence of energetic deep geostrophic flows.last_img read more

Seismic reflection imaging of mixing processes in Fram Strait

first_imgThe West Spitsbergen Current, which flows northward along the western Svalbard continental slope, transports warm and saline Atlantic water (AW) into the Arctic Ocean. A combined analysis of high-resolution seismic images and hydrographic sections across this current has uncovered the oceanographic processes involved in horizontal and vertical mixing of AW. At the shelf break, where a strong horizontal temperature gradient exists east of the warmest AW, isopycnal interleaving of warm AW and surrounding colder waters is observed. Strong seismic reflections characterize these interleaving features, with a negative polarity reflection arising from an interface of warm water overlying colder water. A seismic-derived sound speed image reveals the extent and lateral continuity of such interleaving layers. There is evidence of obliquely aligned internal waves emanating from the slope at 450–500 m. They follow the predicted trajectory of internal S2 tidal waves and can promote vertical mixing between Atlantic and Arctic-origin waters.last_img read more

Manual mapping of drumlins in synthetic landscapes to assess operator effectiveness

first_imgMapped topographic features are important for understanding processes that sculpt the Earth’s surface. This paper presents maps that are the primary product of an exercise that brought together 27 researchers with an interest in landform mapping wherein the efficacy and causes of variation in mapping were tested using novel synthetic DEMs containing drumlins. The variation between interpreters (e.g. mapping philosophy, experience) and across the study region (e.g. woodland prevalence) opens these factors up to assessment. A priori known answers in the synthetics increase the number and strength of conclusions that may be drawn with respect to a traditional comparative study. Initial results suggest that overall detection rates are relatively low (34–40%), but reliability of mapping is higher (72–86%). The maps form a reference datasetlast_img read more

High resolution boundary conditions of an old ice target near Dome C, Antarctica

first_imgA high resolution (1 km line spacing) aerogeophysical survey was conducted over a region near the East Antarctic Ice Sheet’s Dome C that may hold a 1.5 million year old climate record. New ice thickness data derived from an airborne coherent radar sounder was combined with unpublished data that was unavailable for earlier compilations. We find under the primary candidate region elevated rough topography, near a number of subglacial lakes, but also regions of smoother bed. The high resolution of this ice thickness dataset also allows us to explore the nature of ice thickness uncertainties in the context of radar geometry and processing.last_img read more

Page 1 of 405

Powered by WordPress & Theme by Anders Norén