Academic literature on the topic 'Darwin Shelf'

The foraminifera are distributed throughout Port Darwin and differ according to biotope. The tidal flat and coral reef biotopes are basically undisturbed, and contain species of foraminifera typical of those environments. Turbidity is responsible for a lower diversity of the reefal facies, and particularly affects those species with symbiotic algae. The reworked biotope contains foraminifera more typical of the shallow continental shelf. Strong tidal currents associated with the large tidal range are responsible for the reworking of sediments and foraminifera1 tests from inside and outside Port Darwin.

ABSTRACTThe Darwin–Hatherton Glacial system (DHGS) connects the East Antarctic Ice Sheet (EAIS) with the Ross Ice Shelf and is a key area for understanding past variations in ice thickness of surrounding ice masses. Here we present the first detailed measurements of ice thickness and grounding zone characteristics of the DHGS as well as new measurements of ice velocity. The results illustrate the changes that occur in glacier geometry and ice flux as ice flows from the polar plateau and into the Ross Ice Shelf. The ice discharge and the mean basal ice shelf melt for the first 8.5 km downstream of the grounding line amount to 0.24 ± 0.05 km3 a−1 and 0.3 ± 0.1 m a−1, respectively. As the ice begins to float, ice thickness decreases rapidly and basal terraces develop. Constructed maps of glacier geometry suggest that ice drainage from the EAIS into the Darwin Glacier occurs primarily through a deep subglacial canyon. By contrast, ice thins to <200 m at the head of the much slower flowing Hatherton Glacier. The glaciological field study establishes an improved basis for the interpretation of glacial drift sheets at the link between the EAIS and the Ross Ice Sheet.

Nutrient and major ion concentrations were measured in surface water samples from lakes, ponds and streams at sites 30–320 km south of McMurdo Sound: the Darwin Glacier region (79.7–80.0°S), Pyramid Trough in the southern Dry Valleys (78.2°S), and the McMurdo Ice Shelf ablation zone (77.8–78.4°S). These aquatic environments ranged from dilute meltwaters (conductivity <0.05 mS cm−1) to concentrated brines (>50 mS cm−1). The lowest nitrate concentrations were recorded at the sites closest to the seasonally open waters of the Ross Sea. Much higher values (100–142000mg NO3–Nm−3) were recorded at sites further south. These observations support the hypothesis that NO3 precipitation over Antarctica is of stratospheric rather than coastal marine origin. The nitrogen-rich waters contained chloride and nitrate in the ratio 5.45g Cl:1g N (C.V.=8.4%) which is within the range for Antarctic snow, and indicative of nitrate enrichment by freeze concentration processes. Cyanobacterial mats were conspicuous elements of the biota across the full range of salinities, and were usually dominated by oscilatoriacean species. Nitrogen-fixing cyanobacteria and diatoms were also represented in these benthic microbial communities at the more northern sites, but were absent from all samples from the Darwin Glacier region.

AbstractThree temporary Automatic Weather Stations measured summertime surface layer climate over the Darwin–Hatherton Glacial system. These data were used to test a Polar optimized Weather Research and Forecasting model (Polar-WRF) simulation for December as a case study. Observations show differences in hourly averaged solar and net all-wave radiation between white ice and blue ice areas (BIAs). Although the down-welling solar radiation is higher over the white ice region, the net all-wave energy is higher over the BIA. Derived albedo for each surface type confirms that the blue ice areas have lower albedo. Also, the hourly averaged temperatures are higher at lower elevation stations, creating a gradient towards the Ross Ice Shelf. Analysis shows that there is a diurnal oscillation in strength and intensity of the katabatic wind. The two lower stations register a distinct reversal of wind direction in the early afternoon due to intrusion of an anabatic circulation. Anabatic winds are not prevalent further up the Darwin Glacier. A high-resolution Polar-WRF simulation as a case study shows good agreement with observations. The December 2008 case study is characterized by a strong south-westerly katabatic wind over Hatherton, whereas the flow over Lower Darwin was diurnally reversing. Polar-WRF shows that the katabatic front advanced and retreated periodically between Hatherton and Lower Darwin.

More than 40 non-native species have been registered in the zoobenthos of the Black Sea. Only, five alien species, the Crustacea, Rhithropanopeus harrisii (Gould, 1841) and Rhithropanopeus harrisii (Gould, 1841), and the Mollusca, Rapana venosa (Valenciennes, 1846), Mya arenaria (Linne, 1758) and Anadara kagoshimensis (Tokunaga, 1906), were recorded in the benthos on the Crimean shelf between 1999-2014. The blood-cockle A. kagoshimensis had settled on many sites of the Black Sea shelf in the past forty years. The first detection (1999) at the Crimean coast and the temporal variability of this mollusc’s population coincided with the tendency in variability of the water temperature in the area.The five alien species had spatial aggregation and their occurrence did not exceed 23 % in the boundaries of the distribution sites. An increasing trend for their abundance in the last five - seven years was observed. These years were characterized by temperature rise in the surface layer of coastal waters. Similar patterns have been observed in the interannual variability of the biomass and abundance ratio of aliens to native for all zoobenthic taxonomic groups, i.e. of dominance index of alien species.The low level of the dominance index of the introduced species is indicative of low impact on the diversity of the benthic communities of the Crimea coast, i.e. on the scale of the metacommunity. With the exception of the R. venosa, they exhibited lower biomass and abundance along the Crimean coast shelf as opposed to other areas of the Black Sea shelf. Occasionally, the dominance index for the barnacle Amphibalanus improvisus (Darwin, 1854) could be high, a fact attributed to the low biomass and abundance of other benthic species.

The reason why I wavered a bit with this topic is that, after all, it has to do with Darwin, after a great Darwin year, as seen by a German scientist. Not that Darwin was very adept in German: Gregor Mendel’s ‘Versuche über Pflanzenhybriden’ (Experiments on Plant Hybrids) was said to have stayed uncut and probably unread on his shelf, which is why he never got it right with heredity in his life – only Gregory Bateson, Ronald A. Fisher, and JBS Haldane, together with Sewall Wright merged evolution with genetics. But Darwin taught us, nevertheless, in essence why the single human species shows such tremendous ethnic diversity, which impresses us above all through a diversity of languages – up to 7000 altogether – and among them, as a consequence, also German, my mother tongue, and English. It would thus have been a truly Darwinian message, if I had written this article in German. I would have called that the discommunication function of the many different languages in humans, which would have been a most significant message of cultural evolution, indeed. I finally decided to overcome the desire to demonstrate so bluntly what cultural evolution is all about, or rather to show that nowadays, with global cultural progress, ‘the world is flat’ indeed – even linguistically. The real sign of its ‘flatness’ is that English is used everywhere, even if Thomas L. Friedman may not have noticed this sign. But I will also come back to that later, when I hope to show how Darwinian principles connect both natural and cultural evolution, and how they first have been widely misunderstood as to their true meaning, and then have been terribly misused – although more so by culturalists, or some self-proclaimed ‘humanists’, rather than by biologists – or at least most of them. Let me, however, quickly add a remark on human languages. That languages even influence our brains and our thinking, that is: how we see the world, has first been remarked upon by Wilhelm von Humboldt and later, more extensively so, by Benjamin Whorf. It has recently been shown by neural imaging – for instance by Angela Friederici – that one’s native language, first as learned from one’s mother and from those around us when we are babies, later from one’s community of speakers, can deeply impinge on a baby’s brain development and stay imprinted in it throughout life, even if language is, of course, learned and not fully genetically preformed. This shows once more how deep the biological roots are that ground our cultures, according to truly Darwinian principles, even if these cultures are completely learned.

AbstractWe present direct terrestrial evidence of ice volume change of the Darwin and Hatherton glaciers which channel ice from the Transantarctic Mountains into the Ross Ice Shelf. Combining glacial geomorphology with cosmogenic exposure ages from 25 erratics indicates a pre-LGM ice volume at least 600 m thicker than current Hatherton ice elevation was established at least 2.2 million years ago. In particular, five erratics spread across a drift deposit at intermediate elevations located below a prominent moraine feature mapped previously as demarcating the LGM ice advance limits, give a well-constrained single population with mean 10Be age of 37.0 ± 5.5 ka (1σ). At lower elevations of 50–100 m above the surface of Lake Wellman, a further five samples from within a younger drift deposit range in exposure age from 1 to 19 ka. Our preferred age model interpretation, which is partly dependent on the selection of a minimum or maximum age-elevation model, suggests that LGM ice volume was not as large as previously estimated and constrains LGM ice elevation to be within ± 50 m of the modern Hatherton Glacier ice surface, effectively little different from what is observed today.

AbstractLateral drift sheets of outlet glaciers that pass through the Transantarctic Mountains constrain past changes of the huge Ross ice drainage system of the Antarctic Ice Sheet. Drift stratigraphy suggests correlation of Reedy III (Reedy Glacier), Beardmore (Beardmore Glacier), Britannia (Hatherton/Darwin Glaciers), Ross Sea (McMurdo Sound), and “younger” (Terra Nova Bay) drifts; radiocarbon dates place the outer limits of Ross Sea drift in late Wisconsin time at 24,000–13,000 yr B.P. Outlet-glacier profiles from these drifts constrain late Wisconsin ice-sheet surface elevations. Within these constraints, we give two extreme late Wisconsin reconstructions of the Ross ice drainage system. Both show little elevation change of the polar plateau coincident with extensive ice-shelf grounding along the inner Ross Embayment. However, in the central Ross Embayment one reconstruction shows floating shelf ice, whereas the other shows a grounded ice sheet. Massive late Wisconsin/Holocene recession of grounded ice from the western Ross Embayment, which was underway at 13,040 yr B.P. and completed by 6600-6020 yr B.P., was accompanied by little change in plateau ice levels inland of the Transantarctic Mountains. Sea level and basal melting probably controlled the extent of grounded ice in the Ross Embayment. The interplay between the precipitation (low late Wisconsin and high Holocene values) and the influence of grounding on outlet glaciers (late Wisconsin thickening and late Wisconsin/Holocene thinning, with effects dying out inland) probably controlled minor elevation changes of the polar plateau.

Abstract. Differential interferometric synthetic aperture radar (DInSAR) is an essential tool for detecting ice-sheet motion near Antarctica's oceanic margin. These space-borne measurements have been used extensively in the past to map the location and retreat of ice-shelf grounding lines as an indicator for the onset of marine ice-sheet instability and to calculate the mass balance of ice sheets and individual catchments. The main difficulty in interpreting DInSAR is that images originate from a combination of several SAR images and do not indicate instantaneous ice deflection at the times of satellite data acquisitions. Here, we combine the sub-centimetre accuracy and spatial benefits of DInSAR with the temporal benefits of tide models to infer the spatio-temporal dynamics of ice–ocean interaction during the times of satellite overpasses. We demonstrate the potential of this synergy with TerraSAR-X data from the almost-stagnant southern McMurdo Ice Shelf (SMIS). We then validate our algorithm with GPS data from the fast-flowing Darwin Glacier, draining the Antarctic Plateau through the Transantarctic Mountains into the Ross Sea. We are able to reconstruct DInSAR-derived vertical displacements to 7 mm mean absolute residual error and generally improve traditional tide-model output by up to 39 % from 10.8 to 6.7 cm RMSE against GPS data from areas where ice is in local hydrostatic equilibrium with the ocean and by up to 74 % from 21.4 to 5.6 cm RMSE against GPS data in feature-rich coastal areas where tide models have not been applicable before. Numerical modelling then reveals Young's modulus of E=1.0±0.56 GPa and an ice viscosity of ν=10±3.65 TPa s when finite-element simulations of tidal flexure are matched to 16 d of tiltmeter data, supporting the hypothesis that strain-dependent anisotropy may significantly decrease effective viscosity compared to isotropic polycrystalline ice on large spatial scales. Applications of our method include the following: refining coarsely gridded tide models to resolve small-scale features at the spatial resolution and vertical accuracy of SAR imagery, separating elastic and viscoelastic contributions in the satellite-derived flexure measurement, and gaining information about large-scale ice heterogeneity in Antarctic ice-shelf grounding zones, the missing key to improving current ice-sheet flow models. The reconstruction of the individual components forming DInSAR images has the potential to become a standard remote-sensing method in polar tide modelling. Unlocking the algorithm's full potential to answer multi-disciplinary research questions is desired and demands collaboration within the scientific community.

In ’Why didn't they ask Evans?’ (Turney, 2017), I draw together previously unpublished sources and new analyses of published material to cast further light on the circumstances that led to the fatal events surrounding the return of Captain Robert Falcon Scott's Polar Party on the British Antarctic Expedition (BAE, 1911–1913). Of particular importance are the notes on the meeting between the Royal Geographical Society's President Lord Curzon and the widows Kathleen Scott and Oriana Wilson in April 1913, which explicitly identify Lieutenant Edward ‘Teddy’ Evans as having removed food that exceeded his allocation as a member of the Last Supporting Party (Curzon, 1913), the establishment and almost immediate closure of a ‘Committee of Enquiry’ chaired by Lord Curzon (Beaumont, 1913a, b, c; Cherry-Garrard, 1913a; Darwin, 1913; Goldie, 1913), the recognition of missing food at key depots by the returning Polar Party on the 7, 24 and 27 February 1912 (Scott, 1913a; Wilson, 1912), Evans’ anger at not being selected as a member of the Polar Party and his early departure home (Evans, 1912), the revised timeline of when Evans fell down with scurvy on the Ross Ice Shelf to apparently align with when and where the food was removed (The Advertiser, 3 April 1912, Adelaide: 10) (Cherry-Garrard, 1922; Ellis, 1969; Evans, 1912, 1913a, 1943; Lashly, 1912; Scott, 1913a, 1913b), Evans’ failure to ensure Scott's orders regarding the return of the dog sledging teams had been acted on (Cherry-Garrard, 1922; Gran, 1961; Hattersley-Smith & McGhie, 1984) and the misunderstanding amongst senior Royal Geographical Society members during Evans’ recuperation in the UK that Apsley Cherry-Garrard ‘was to meet the South Pole party, with two teams of dogs, at the foot of the [Beardmore] glacier’ (Markham, 1913). I would like to thank May (2018) for her comment and acknowledge that Edward Wilson's sketchbooks of the expedition's logistics, scientific priorities, sketches and notes on the BAE comprise entries from 1911–1912 and not solely from 1912, which Turney (2017) used to denote the year of the last entry.

[Truncated abstract] The Northern Bonaparte Basin and adjacent Darwin Shelf form part of a major petroleum province on the northwestern margin of Australia. The middle to Late Cretaceous Bathurst Island Group consists of siliciclastic and pelagic carbonate strata that form the regional seal to underlying Upper Jurassic and Lower Cretaceous reservoir sandstones. The Bathurst Island Group has previously been subdivided into four stratigraphic sequences or ‘play intervals’ bound by regional disconformities in the Valanginian (KV horizon), Lower Aptian (KA horizon), upper Lower Cenomanian (KC horizon), Middle Campanian (KSC horizon), and at the CretaceousPaleocene boundary (T horizon). Correlation of these sedimentary packages and stratigraphic surfaces requires high-resolution calcareous microfossil biostratigraphy, while palaeobathymetric determinations based on benthonic foraminiferal assemblages are important for determining the subsidence history of the area and relative sea-level changes. This study presents the first detailed stratigraphic distributions, taxonomic lists and illustrations of foraminifera and calcareous nannofossils from the Bathurst Island Group of the Northern Bonaparte Basin and Darwin Shelf. A biostratigraphic framework has been constructed for the study area incorporating ‘standard’ (Tethyan) Cretaceous planktonic foraminiferal and calcareous nannofossil events where applicable, and integrating locally defined events where necessary. This framework allows Cretaceous strata to be correlated regionally across the study area and to the global chronostratigraphic scale. Correlation of the Northern Bonaparte Basin and Darwin Shelf strata to the Cretaceous Stages and international time scale is based on recent ties of nannofossil and foraminiferal events to macrofossil zones and palaeomagnetic polarity chrons at ratified and proposed Global Stratotype Sections and Points (GSSPs). Calcareous nannofossil events recorded in the study area that are critical for defining stage boundaries include the lowest occurrences of Prediscosphaera columnata, Micula decussata, Lithastrinus grillii, and Aspidolithus parcus parcus, and the highest occurrences of Helenea chiastia, Lithastrinus moratus, Aspidolithus parcus constrictus, and Eiffellithus eximius. Important planktonic foraminiferal events for correlation include the lowest occurrences of Rotalipora gr. globotruncanoides, and Dicarinella asymetrica, and the highest occurrences of Planomalina buxtorfi, Rotalipora cushmani, and Dicarinella asymetrica. During the middle to Late Cretaceous the Northern Bonaparte Basin and Darwin Shelf occupied mid-high palaeolatitudes between 35ºS to 45ºS. These palaeolatitudes are reflected in the transitional character of the planktonic microfossil assemblages, which combine elements of the low-latitude, warm-water Tethyan Province to the north and the cool-water high-latitude Austral Province to the south. ‘Standard’ Tethyan zonations are most applicable for uppermost AlbianMiddle Campanian strata because equator-to-pole temperature gradients were weakly developed, and global climate was warm and equable during this interval. These conditions resulted in broad latitudinal distributions for Tethyan marker species, and consequently most UC calcareous nannofossil zones and European-Mediterranean planktonic foraminiferal zones are recognised. In contrast, the EarlyLate Albian and the late Middle CampanianMaastrichtian were intervals of greater bioprovinciality and stronger palaeotemperature gradients. In these intervals application of the Tethyan zonations is more difficult, and a number of the Tethyan biostratigraphic markers are absent from the study area (e.g. Ticinella species in the Albian and Radotruncana calcarata in the Late Campanian). Cretaceous palaeobathymetric reconstruction of the study area is based on comparison of the foraminiferal assemblages with those of previous Cretaceous palaeobathymetric studies. Marginal marine assemblages consist solely of low diversity siliceous agglutinated foraminifera (e.g. Trochammina). Inner and middle neritic water depths (0-100 m) contain rare to common planktonic foraminifera (mainly globigerine forms), robertinids (e.g. Epistomina), siliceous agglutinates, lagenids, buliminids (e.g. Neobulimina), and rotaliids. The outer neritic zone (100-200 m water depth) contains abundant planktonic foraminifera (keeled and globigerine), calcareous agglutinates (e.g. Dorothia), and diverse lagenids, buliminids, and rotaliids. Upper-middle bathyal water depths (200-1000 m) are characterised by abundant planktonic foraminifera, common siliceous agglutinated taxa (e.g. Glomospira), rare to common Osangularia, and globular species of Gyroidinoides, Pullenia, and Paralabamina.

In this chapter, the author recalls how his family would spend afternoons and evenings reading poems on the screened porch overlooking the sand dunes, the beach, and the sea in a rented house in Garden City, South Carolina. His father-in-law, Lucas, eagerly anticipates those times, bringing along his 101 Favorite Poems, published in 1929. But they all bring a few poems to the porch—even the children. At age ten their nephew Aidan Powers came equipped with a full set of Shel Silverstein's ingenious poetry. Masterpieces and ditties are treated with equal weight: poems by Percy Bysshe Shelley, John Keats, William Wordsworth, and Lord Byron are interspersed with children's poetry and nonsense verses. The evenings of poetry reading on the porch at the beach were so enjoyed by the family that they spawned poetry nights in the Dargan living room back in Darlington, South Carolina, on a weekly basis.

By the end of the old millennium, social movement organizations (SMOs) had become the most popularly acclaimed and, in many respects, trusted agencies advocating global environmental change. They had won widespread public admiration because of their daring and heroic undertakings, because of the verve and symbolic acuity of their actions and because they seemed to be in the vanguard of environmental change. Of course, commentators noted that governments and inter-governmental agencies might have more power to set and influence environmental standards, that companies might be making the greatest impacts on the environment, that it was often scientists who identified possible environmental problems which were ‘off the radar’ of environmental groups, and that the daily consumer choices of the industrialized world’s massed citizens and commuters might outweigh their efforts. All the same, social movements represented the quintessential environmental actor. In cultural terms, environmental organizations stood for the environment in a way which the Environment Minister, the collected scientists of the Intergovernmental Panel on Climate Change or Shell simply could not. Moreover, those movement organizations which focused on issue of global environmental change seemed particularly successful; in the late 1980s through to the early 1990s—around the time of the Earth Summit— they were rewarded with disproportionately rapid growth and cultural cachet (see McCormick 1991: 152–5 who cites Friends of the Earth, Greenpeace and the World Wide Fund for Nature (WWF) in this regard). And their market prominence within the NGO sector has largely continued. At the same time, social movements commanded the attention of social scientists and commentators. For one thing, social movements and the associated movement organizations appeared to confound expectations. Far from politics as usual, social movements indicated how successfully and how enduringly people could be organized—or organize themselves —around non-conventional political objectives. Standard economic and political theories did not anticipate that people ‘ought’ to mobilize so successfully around a diffuse political objective such as global environmental improvement.

Pu material can generate surface corrosion and self-radiation effect during storage, leading to the creation and recoil of uranium and helium ions, which produce defects through displacement cascades, these self-irradiation defects tend to change plutonium properties. To study these aging behavior, calculations at the spin unrestricted generalized gradient approximation (GGA) level of density functional theory (DFT) have been performed using the DMol3 programs. Relativistic effects, such as mass-velocity, Darwin term, are considered in this code. Some conclusions are draw as follows: 1) Band structure of the (100) surface of γ-Pu is very narrow around the Fermi level, showing that the eigenstate of this level is mainly composed of local atomic orbital, the local property of electrons in this band is very strong, while the band around the Fermi level is mainly constituted by 5f narrow band; 2) DOS of the (100) surface of γ-Pu are mainly composed of the density of states in −48–41eV, −23–16eV, −3–2eV; 3) Contribution of s shell to the total DOS is mainly distributed in the first interval, and p shell is mainly in the second interval, while d and f shells are mainly in the third interval.

Abstract Closely spaced cylinder arrays are widely used in offshore platform designs. When subject to random waves and currents, their interactive response behavior is very complicated and perhaps beyond the ability of direct analytical formulations to model their motions. In this study extremal statistics methods were utilized to analyze model basin data that investigated the response behavior of in-line paired and triple deep-water cylinder arrays. The cylinder models used in the model basin experiments were constructed with an ABS outer plastic shell that surrounded an inner steel wire core that could be pretensioned. The cylinder model diameter ratio of the outer shell to steel wire was 4.25 with a slenderness ratio of approximately 1300. The cylinder arrays were pretensioned on the top side and were tested varying pitch to diameter ratios of 3.0, 4.4, and 8.75. The random sea states were simulated using a JONSWAP spectrum. The response time series were investigated using generalized extreme value (GEV) distributions that were fitted to the block maxima that represented the maximum in-line relative displacement between two adjacent tendons. The most appropriate models were selected by comparing their goodness of fit via the Anderson-Darling (AD) test criterion with special attentions paid to their performance in fitting the upper tail of the distribution. The selected models were then used to predict threshold-crossing probabilities of the cylinder array relative response behavior. Both tabular and graphical interpretations of the findings are presented and discussed.