Late Quaternary climate-driven environmental change in the Larsemann Hills, East Antarctica, multi-proxy evidence from a lake sediment core

Little is known about the response of terrestrial East Antarctica to climate changes during the last glacial-interglacial cycle. Here we present a continuous sediment record from a lake in the Larsemann Hills, situated on a peninsula believed to have been ice-free for at least 40,000 yr. A mutli-proxy data set including geochronology, diatoms, pigments and carbonate stable isotopes indicates warmer and wetter conditions than present in the early part of the record. We interpret this as Marine Isotope Stage 5e after application of a chronological age-depth model and similar ice core evidence. Dry and cold conditions are inferred during the last glacial, with lake-level minima, floristic changes towards a shallow water algal community, and a greater biological receipt of ultraviolet radiation. During the Last Glacial Maximum and Termination I the lake was perennially ice-covered, with minimal snowmelt in the catchment. After ca. 10,500 cal yr B.P., the lake became seasonally moated or ice-free during summer. Despite a low accumulation rate, the sediments document some Holocene environmental changes including neoglacial cooling after ca. 2450 cal yr B.P., and a gradual increase in aridity and salinity to the present.     

Reply to discussion of “Measurements of sheet flow transport in acceleration-skewed oscillatory flow and comparison with practical formulations” by D.A. van der A,T. O'Donoghue and J.S. Ribberink

This is a reply to the discussion by Camenen and Larson (Coastal Eng., 58, 2011, 131–134) of “Measurements of sheet flow transport in acceleration-skewed oscillatory flow and comparison with practical formulations” by D.A. van der A et al. (Coastal Eng. 57, 2010, 331–342). The authors of the original paper (Van der A et al., 2010) thank the discussers for their interest in and comments on the work presented in the paper.     

The emergence of a post-industrial music economy? Music and ICT synergies in Stockholm, Sweden

Research into the music industry has for a long time been almost exclusively dominated by a focus on the production of albums and songs. In recent years, however, cities such as Stockholm have seen the growth of a profitable and varied music services industry producing everything from remixes to music marketing strategies. Standing at the forefront of this growth industry are a large number of firms attempting to combine in innovative ways music and ICT. This can take a variety of forms, for instance: selling and distributing music over the internet; web design and computerised advertising services tailored to music products; software design focused on multimedia products and virtual instruments; high-tech post-production and mixing services; and virtual centres and communities of music industry actors. The article will examine these activities within the city in attempt to measure the direction and cohesiveness of the emerging sector. The article concludes by arguing that these type of new industrial synergies tell us much about the way industrial innovations are formed in an interindustry and inter-cluster environment, and the future competitiveness and shape of the music industry. In particular, the article argues that evidence from Stockholm points to the emergence of a post-industrial musical economy.     

Porosity and permeability in sediment mixtures

Porosity in sediments that contain a mix of coarser- and finer-grained components varies as a function of the porosity and volume fraction of each component. We considered sediment mixtures representing poorly sorted sands and gravely sands. We expanded an existing fractional-packing model for porosity to represent mixtures in which finer grains approach the size of the pores that would exist among the coarser grains alone. The model well represents the porosity measured in laboratory experiments in which grain sizes and volume fractions were systematically changed within sediment mixtures. Permeability values were determined for these sediment mixtures using a model based on grain-size statistics and the expanded fractional-packing porosity model. The permeability model well represents permeability measured in laboratory experiments using air- and water-based permeametry on the model sediment mixtures.     

Exploring biological constraints on the glacial history of Antarctica

The evolutionary and biogeographic history of the contemporary Antarctic terrestrial and marine biotas reveals many components of ancient origin. For large elements of the terrestrial biota, long-term isolation over timescales from hundreds of thousands to tens of millions of years, and thus persistence through multiple glacial cycles, now appears to be the norm rather than the exception. For the marine biota there are some parallels with benthic communities also including ancient components, together with an incidence of species-level endemism indicating long-term isolation on the Antarctic continental shelf. Although it has long been known that a few ice-free terrestrial locations have existed in Antarctica for up to 10–12 million years, particularly in the Dry Valleys of Victoria Land along with certain nunataks and higher regions of large mountain ranges, these do not provide potential refugia for the majority of terrestrial biota, which occur mainly in coastal and/or low-lying locations and exhibit considerable biogeographic regionalisation within the continent. Current glacial models and reconstructions do not have the spatial resolution to detect unequivocally either the number or geographical distribution of these glacial refugia, or areas of the continental shelf that have remained periodically free from ice scouring, but do provide limits for their maximum spatial extent. Recent work on the evolution of the terrestrial biota indicates that refugia were much more widespread than has been recognised and it is now clear that terrestrial biology provides novel constraints for reconstructing the past glacial history of Antarctica, and new marine biological investigations of the Antarctic shelf are starting to do likewise.     

Post-glacial regional climate variability along the East Antarctic coastal margin—Evidence from shallow marine and coastal terrestrial records

We review the post-glacial climate variability along the East Antarctic coastline using terrestrial and shallow marine geological records and compare these reconstructions with data from elsewhere. Nearly all East Antarctic records show a near-synchronous Early Holocene climate optimum (11.5–9 ka BP), coinciding with the deglaciation of currently ice-free regions and the optimum recorded in Antarctic ice and marine sediment cores. Shallow marine and coastal terrestrial climate anomalies appear to be out of phase after the Early Holocene warm period, and show complex regional patterns, but an overall trend of cooling in the terrestrial records. A Mid to Late Holocene warm period is present in many East Antarctic lake and shallow coastal marine records. Although there are some differences in the regional timing of this warm period, it typically occurs somewhere between 4.7 and 1 ka BP, which overlaps with a similar optimum found in Antarctic Peninsula terrestrial records. The differences in the timing of these sometimes abrupt warm events in different records and regions points to a number of mechanisms that we have yet to identify. Nearly all records show a neoglacial cooling from 2 ka BP onwards. There is no evidence along the East Antarctic coastline for an equivalent to the Northern Hemisphere Medieval Warm Period and there is only weak circumstantial evidence in a few places for a cool event crudely equivalent in time to the Northern Hemisphere's Little Ice Age. There is a need for well-dated, high resolution climate records in coastal East Antarctica and particularly in Terre Adélie, Dronning Maud Land and Enderby Land to fully understand the regional climate anomalies, the disparity between marine and terrestrial records, and to determine the significance of the heterogeneous temperature trends being measured in the Antarctic today.     

Modeling and interpreting the seismic-reflection expression of sandstone in an ancient mass-transport deposit dominated deep-water slope environment

Subsurface mass-transport deposits (MTDs) commonly have a chaotic seismic-reflection response. Synthetic seismic-reflection profiles, created from a precise lithological model, are used to interpret reflection character and depositional geometries at multiple frequencies. The lithological model was created from an outcrop of deep-water lithofacies where sandstone deposition was influenced by mass-transport deposit topography. The influence of MTD topography on sandstone distribution should be considered in reservoir characterization and modeling when MTDs underlie the reservoir, especially if the reservoir is thin relative to the scale of the topography. MTD topography up to several tens of meters in both the horizontal and vertical dimensions (relative to local elevation) compartmentalizes significant quantities of sandstone and is not resolved at lower seismic-reflection frequencies. The resolvability of thick (up to 70 m) sandstone packages is hindered when they are encased in MTDs of at least equivalent thickness. Lateral and vertical changes in seismic-reflection character (e.g., amplitude, polarity, geometry) of sandstone packages in the synthetic profiles are due to lithology changes, tuning effects, resolution limits, and depositional geometries, which are corroborated by the lithological model. Similar reflection-character changes are observed in an actual seismic-reflection profile, of comparable scale to the synthetic profiles, from the Gulf of Mexico, which demonstrates similar lithofacies distributions. Synthetic profiles, when constrained by a precise lithological model, are particularly useful analogues for interpretation of lithofacies relationships, and depositional geometries, in complicated depositional environments, such as deep-water slope deposits.     

Recent environmental change and trace metal pollution in World Heritage Bathurst Harbour, southwest Tasmania, Australia

Bathurst Harbour in World Heritage southwest Tasmania, Australia, is one of the world’s most pristine estuarine systems. At present there is a lack of data on pollution impacts or long-term natural variability in the harbor. A ca. 350-year-old ²¹⁰Pb-dated sediment core was analysed for trace metals to track pollution impacts from local and long-range sources. Lead and antimony increased from AD 1870 onwards, which likely reflects remote (i.e. mainland Australian and global) atmospheric pollution sources. Variability in the concentrations of copper and zinc closely followed the history of mining activities in western Tasmania, which began in the AD 1880s. Tin was generally low throughout the core, except for a large peak in AD 1989 ± 0.5 years, which may be a consequence of input from a local small-scale alluvial tin mine. Changes in diatom assemblages were also investigated. The diatom flora was composed mostly of planktonic freshwater and benthic brackish-marine species, consistent with stratified estuarine conditions. Since mining began, however, an overall decrease in the proportion of planktonic to benthic taxa occurred, with the exception of two distinct peaks in the twentieth century that coincided with periods of high rainfall. Despite the region’s remoteness, trace metal analyses revealed evidence of atmospheric pollution from Tasmanian and possibly longer-range mining activities. This, together with recent low rainfall, appears to have contributed to altering the diatom assemblages in one of the most pristine temperate estuaries in the world.     

Assessing water quality in Marine Protected Areas from Southern California, USA

Despite the regulatory mandate to maintain “natural water quality”, there are ?271 storm drain discharges that potentially threaten the 14 designated marine water quality protected areas in Southern California called Areas of Special Biological Significance (ASBS). After sampling 35 site-events, the geomean concentrations of total suspended solids, nutrients, total and dissolved trace metals, and polycyclic aromatic hydrocarbons in the ocean following storm events were similar between reference drainages and ASBS discharge sites. Concentrations of chlorinated hydrocarbons were nondetectable and no post-storm sample exhibited significant toxicity to the endemic purple sea urchin (Strongylocentrotus purpuratus) near ASBS discharge sites. A reference-based threshold was developed and, despite the similarities in average concentrations, there were some individual ASBS discharge sites that were greater than reference background. Cumulatively across all ASBS, the constituents that were most frequently greater than the reference-based threshold were nutrients and general constituents, followed by dissolved and total trace metals.