The practical salinity scale 1978 and its antecedents

The history of the definition of salinity and the methods of computing It are traced from the beginning of the twentieth century until the present. Difficulties that have arisen in existing practices are discussed, in particular, the situation regarding reduction of in-situ CTD observations. The Practical Salinity Scale 1978 is an attempt to remove the shortcomings; it has been recommended for international acceptance. The basis for this new scale is an equation relating the ratio of the electrical conductivity of the seawater sample to that of a standard potassium chloride solution (KCI) at15degC atmospheric pressure. The samples used were prepared from standard seawater diluted with distilled water or evaporated by weight. Finally, the set of new equations for CTD data reduction is given, based upon the work of authors whose papers are appearing elsewhere in this volume.     

Recent occurrence of large jökulhlaups at Lake Tuborg,Ellesmere Island,Nunavut

The varved sediment record from glacially-fed Lake Tuborg, Ellesmere Island, Nunavut, shows that only three large jökulhlaups have occurred there in the last millennium: 2003, 1993, and 1960. Detailed analyses of sediment microstructure and particle size, combined with in-situ hydrometeorological and limnological process studies, allowed jökulhlaup facies identification and discrimination from deposits from other processes. Deposits from large jökulhlaups are anomalously thick, typically lack internal structure, have sharp bases, and fine upwards. The ice-dammed lake above Lake Tuborg (the source of the jökulhlaups) likely changed its drainage style in 1960, from ice-dam overtopping to ice-dam flotation and glacial tunnel enlargement by melt widening, which allowed the lake to drain completely and catastrophically. Complete drainage of ice-dammed lakes by ice-dam flotation is rare in the region is due to the pervasiveness of cold-based ice. Twentieth century warming is likely responsible for some combination of dam thinning, lake expansion and deepening, and changing the thermal regime at the base of the dam. Anomalously thick individual varves were periodically deposited beginning in the nineteenth century, and their thickness increased with time. This likely reflects a combination of increased ice dam overtopping, subaqueous slope failures, sediment availability and rising air temperature. The varve record presented here significantly correlates with a previous, shorter record from Lake Tuborg. However, generally weak correlations are found between the new varve time series, regional records of air temperature, and glacial melt from ice cores on the Agassiz Ice Cap. It is hypothesized that on short timescales, sedimentation at the coring location reflects a complex and varying integration of multiple hydroclimatic, geomorphic and limnologic influences.     

Geological Setting and Controls on the Development of Graphite, Sillimanite and Phosphate Mineralization within the Jiamusi Massif: An Exotic Fragment of Gondwanaland Located in North-Eastern China?

China is the world's biggest producer and exporter of graphite and also possesses the world's largest reserves of crystalline graphite. One of the main production areas is in northeastern China around Jixi, in Heilongjiang Province, where graphite, sillimanite and phosphate form in original sedimentary horizons within the Mashan Group. The Mashan Group is composed of khondalitic metasediments and tectonically interleaved orthogneisses, all metamorphosed to granulite facies. The peak conditions have been calculated at 800–850°C at 5.3–6.2 kb and the P–T–t path defines a tight clockwise loop involving simultaneous decrease in temperature and pressure, falling to 410–490°C at less than 3 kb. This metamorphic event is interpreted as resulting from continent–continent collision, with emplacement of mantle–derived mafic magma and possible delamination at the base of the crust. Metamorphism has been precisely dated at 500 Ma, using U–Pb zircon SHRIMP techniques. It appears likely that this terrane formed part of an originally more extensive orogenic belt of Late Pan–African age. Rocks of similar age are recorded from east Antarctica, Western Australia, India and Sri Lanka, suggesting that the Mashan Group was most likely juxtaposed with these areas within Gondwanaland. The mechanism by which the Mashan Group arrived at its present position between the Siberian and North China Cratons is poorly constrained, but it appears likely that, along with the North China, South China and Tarim Blocks, it underwent a northward drift from an initial location off northern Australia to finally dock with the Siberian Craton in the Late Permian to Late Jurassic.     

Hydrological and sediment yield response to summer rainfall in a small high Arctic watershed

In cold regions, the response and related antecedent mechanisms that produce flood flows from rainfall events have received limited study. In 2007, a small watershed at Cape Bounty, Melville Island, Nunavut, was studied in detail during the melt season. Two rainfall events on June 30 and July 22, totalling 9·2 and 10·8 mm, respectively, represented significant contributions to seasonal discharge and sediment transport in a year with a low winter snowpack. The precipitation events elevated discharge and suspended sediment concentrations to twice the magnitude of the nival melt, and generated the only measurable downstream lacustrine turbidity current of the season. In two days, rainfall runoff transported 35% of the seasonal suspended sediment load, in contrast to 29% transported over the nival freshet. The magnitude and intensity of the rain events were not unusual in this setting, but the rainfall response was substantial in comparison with equivalent past events. Exceptional temperatures of July 2007 generated early, deep permafrost thaw, and ground ice melt. The resultant increase in soil moisture amplified the subsequent rainfall runoff and sediment transport response. These results demonstrate the importance of antecedent moisture conditions and the role of permafrost active layer development as an important factor in the rainfall runoff and sediment transport response to precipitation events. Copyright © 2009 John Wiley & Sons, Ltd.     

Sub‐fossil Chironomidae as indicators of palaeoflow regimes: integration into the PalaeoLIFE flow index

The sub‐fossil head capsules of larval Chironomidae have been widely exploited as palaeoecological indicators of lentic ecosystems but their value in the interpretation of the evolution of lotic systems has been underutilised by comparison. Recent research has demonstrated that the remains of Chironomidae are abundant within fluvial sequences and that they offer a valuable record of channel change and floodplain evolution that may complement that derived from existing biological and sedimentological techniques. This paper demonstrates the use of Chironomidae in characterising the palaeoflow regime of a large mid–late Holocene floodplain palaeochannel (5470–4960 to 1530–1350 cal. a BP) of the River Trent (Derbyshire, UK). Using expert knowledge and published information regarding flow preferences, larval Chironomidae were incorporated into the PalaeoLIFE (Lotic‐invertebrate Index for Flow Evaluation) methodology. The results clearly demonstrate that the sub‐fossil record provided by Chironomidae can be used to characterise changes in the flow regime within palaeochannel sections. At the scale of the channel section, species‐ and generic‐level ecological associations can provide useful information regarding habitat characteristics, including the presence of instream vegetation, mineral substrates and woody debris. The ability to undertake environmental reconstruction and channel evolution history was significantly enhanced through the application of a multi‐proxy approach, by incorporating other aquatic insect groups (Trichoptera and Coleoptera) into the PalaeoLIFE metric, together with sedimentological data. Copyright © 2010 John Wiley & Sons, Ltd.     

Beryllium‐10 surface exposure dating of glacial successions in the Central Alaska Range

Glacial landforms and outwash terraces in the Nenana River valley, Reindeer Hills and Monahan Flat in the central Alaska Range were dated with 60 ¹⁰Be exposure ages to determine the timing of Late Pleistocene glaciation. In the Nenana River valley, glaciation occurred at 104–180 ka (Lignite Creek glaciation), ca. 55 ka (Healy glaciation), and ca. 16 ka (Carlo Creek phase); glaciers retreated in the Reindeer Hills and Monahan Flat by ca. 14 ka and ca. 13 ka, respectively. The Carlo Creek moraine is similar in age to at least six other moraines in the Alaska Range, Ahklun Mountains and Brooks Range. The new data suggest that post‐depositional geological processes limit the usefulness of ¹⁰Be methods to the latter part (≤60 ka) of the late Quaternary in central Alaska. Ages on Healy and younger landforms cluster well, with the exception of Riley Creek moraines and Monahan Flat‐west sites, where boulders were likely affected by post‐depositional processes. Copyright © 2010 John Wiley & Sons, Ltd.     

“It's so different today”: Climate change and indigenous lifeways in British Columbia,Canada

Indigenous Peoples of British Columbia have always had to accommodate and respond to environmental change. Oral histories, recollections of contemporary elders, and terms in indigenous languages all reflect peoples’ responses to such change, especially since the coming of Europeans. Very recently, however, many people have noted signs of greater environmental change and challenges to their resilience than they have faced in the past: species declines and new appearances; anomalies in weather patterns; and declining health of forests and grasslands. These observations and perspectives are important to include in discussions and considerations of global climate change.