Oceanic double-infusion: introduction

Double-diffusion, the mixing of fluids with two constituents of different molecular diffusivities, was originally discovered in the mid-1800s, forgotten, then rediscovered as an ‘oceanographic curiosity’ a century later. Many oceanographers suspect that double-diffusion has major effects on oceanic water masses and circulation, but direct measurement of the effects has proven difficult. In 1996, a Working Group was formed under the auspices of the Scientific Committee on Ocean Research (SCOR WG108), with the goal to identify progress and barriers to quantifying oceanic double-diffusive fluxes, and make recommendations for further progress. This document gives a brief history of double-diffusion, a review of evidence of its potential effects in the ocean, and gives an overview of the review articles contained in this volume, written by the Working Group members with the above aim in mind.     

Observing systems and data sets related to the cryosphere in Canada: A contribution to planning for the global climate observing system

Abstract

The current status and history of observing systems for snow cover, sea and freshwater ice, glaciers, ice caps, ground ice and permafrost in Canada are reviewed as part of a contribution to the WMO's Global Climate Observing System program. The data requirements that have been identified by previous discussion groups for different research, change detection and monitoring purposes are summarized. Problem areas in data collection and processing, as well as gaps in the observing/data systems, are illustrated and the status of cryospheric data archives relating to Canada, and data distribution, are discussed. The present status is considered to be unsatisfactory in a number of respects for the different cryospheric variables important for global change research.     

Simple models,powerful ideas: Towards effective integrative practice

Growing evidence that human societies are on an unsustainable development path has led to widespread calls for a better understanding of the complex dynamics of the human–Earth system. The generation of such an understanding is a considerable challenge. It requires a substantial collaborative effort by a wide range of researchers from the natural and social sciences, engineering, the humanities, and the wider community. The extent to which the participants in this transdisciplinary endeavour manage to create shared understandings will be a critical factor in determining their eventual success. It will set a fundamental limit on their ability to communicate with one another, and hence the degree of integration that they can achieve. It will determine the usefulness of the insights that emerge from their efforts.In this paper it is suggested that the identification of ‘powerful ideas’, fundamental concepts that are both simple and generic, is an effective way to proceed. Empirical evidence from cognitive science and basic insights from information theory provide a framework for a discussion of the nature of such ideas, and of a practical approach to their formulation. It is argued that the collaborative construction of powerful ideas constitutes an efficient form of ‘focused dialogue’ that can support the rapid development of the required shared understandings.     

Bioaccumulation and enantiomeric profiling of organochlorine pesticides and persistent organic pollutants in the killer whale (Orcinus orca) from British and Irish waters

Concentrations and enantiomeric profiles for a range of organochlorine compounds are reported in blubber samples from a number of individual killer whales (Orcinus orca) from British and Irish waters. Elevated contaminant levels and enriched isotopic ratios were determined in one individual whale sampled in the Scottish Western Isles compared to the others suggesting marine mammal based dietary influences. The potential application of isotopic ratios to model contaminant uptake, enantioselective enrichment and accumulation is demonstrated. Data are presented which provide information on enantioselective enrichment factors (EFs) for o,p'-DDT, alpha-HCH and toxaphene congeners CHB26 and CHB 50. This dataset further improves the current database on reported levels of a number of contaminants and provides additional background information on potential metabolic processes in killer whales from British and Irish waters.     

Vulnerability and adaptation in a dryland community of the Elqui Valley, Chile

Livelihoods in drylands are already challenged by the demands of climate variability, and climate change is expected to have further implications for water resource availability in these regions. This paper characterizes the vulnerability of an irrigation-dependent agricultural community located in the Elqui River Basin of Northern Chile to water and climate-related conditions in light of climate change. The paper documents the exposures and sensitivities faced by the community in light of current water shortages, and identifies their ability to manage these exposures under a changing climate. The IPCC identifies potentially increased aridity in this region with climate change; furthermore, the Elqui River is fed by snowmelt and glaciers, and its flows will be affected by a warming climate. Community vulnerability occurs within a broader physical, economic, political and social context, and vulnerability in the community varies amongst occupations, resource uses and accessibility to water resources, making some more susceptible to changing conditions in the future. This case study highlights the need for adaptation to current land and water management practices to maintain livelihoods in the face of changes many people are not expecting.     

A Younger Dryas (Loch Lomond Stadial) jökulhlaup deposit, Fort Augustus, Scotland

This study provides an insight into the impact of probably the largest flood ever to have been identified in mainland Britain by examining new sedimentary evidence from the Auchteraw terrace, Fort Augustus, Scotland. Study of three sections reveals a succession consisting of: (1) sheet gravels; (2) large trough-shaped depressions infilled with cross-stratified sands and gravels; (3) smaller-scale, finer-grained cross-strata; and (4) sheet-like, occasionally channelized, bimodal sand and gravel beds. This study shows that both the sedimentology and morphology of the Auchteraw terrace are consistent with jökulhlaup deposition and reveal a greater variety of lithofacies types than identified in previous studies of jökulhlaups from ice-dammed lakes. The fine-grained nature of the sediment discussed in this study emphasizes the importance of sediment supply for the formation of distinctive jökulhlaup successions. The sedimentary evidence recorded here provides a valuable tool for the interpretation of the magnitude and frequency of proglacial meltwater flows associated with Pleistocene ice sheets worldwide.     

Changes in weather persistence: Insight from Inuit knowledge

Since the 1990s, local residents from around the Arctic have reported changes in weather predictability. Examination of environmental measurements have not, until now, helped describe what the local inhabitants have been reporting, in part because prior studies did not focus directly on the persistence aspect of weather. Here we show that there is evidence of changes in persistence in weather over the last two decades for Baker Lake, Nunavut, Canada. Hourly data indicate that for local spring, the persistence of temperature has changed dramatically in the last 15 years with some years showing a strong drop in day-to-day persistence in the local spring afternoons, somewhat at odds with changes in persistence on a more global scale. Changes in daily persistence may have implications for human health, agriculture, and ecosystems worldwide. More importantly, the approach of merging indigenous knowledge with scientific methods may offer unexpected benefits for both.     

Quaternary tephra marker beds and their potential for palaeoenvironmental reconstruction on Chatham Island,east of New Zealand,southwest Pacific Ocean

Tephras provide one of the most reliable methods of time control and synchronisation within Quaternary sequences. We report on the identification of two widespread rhyolitic tephras – the Kawakawa and Rangitawa tephras – preserved in extensive peat deposits on Chatham Island ～900 km east of New Zealand. The tephras, both products of supereruptions from the Taupo Volcanic Zone, occur as pale, fine‐ash dominated layers typically 10–150 mm thick. Mineralogically they are dominated by rhyolitic glass, together with subordinate amounts of quartz, feldspar, hypersthene, hornblende, Fe–Ti oxides and zircon. Phlogopite/biotite was identified additionally in Rangitawa Tephra. Ages for each tephra were obtained via mineralogical and major element glass composition‐based correlation with well‐dated equivalent deposits on mainland New Zealand, and we also obtained a new zircon fission‐track age for Rangitawa Tephra (350 ± 50 ka) on Chatham Island. Both tephras were erupted at critical times for palaeoenvironmental reconstructions in the New Zealand region: the Kawakawa at ca. 27 cal. ka, near the beginning of the ‘extended’ LGM early in marine isotope stage (MIS) 2; and the Rangitawa at ca. 350 ka near the end of MIS 10. The time constraints provided by the tephras demonstrate that Chatham Island peats contain long‐distance pollen derived from mainland New Zealand, which provides a reliable proxy for identifying glacial–interglacial climate conditions, in this case during the MIS 11–10 and MIS 2–1 cycles. The two tephras thus provide important chronostratigraphic tie‐points that facilitate correlation and synchronisation not only across the Quaternary deposits of the Chatham Islands group but also with climatically significant terrestrial and marine records in the wider New Zealand region. Copyright © 2010 John Wiley & Sons, Ltd.     

Impacts of changes in the flue-cured tobacco sector on farmers in Ontario, Canada

Impacts of the forces and processes of agricultural restructuring are described in this paper through an analysis of farmers’ ‘lived experience’ in the tobacco sector of Ontario, Canada. The paper argues that the political and economic changes in the 1980s fundamentally altered tobacco farming and the broader rural community. The analysis is based upon a survey of farmers and former farmers, and includes examples of individual case histories. The results show the ways in which farmers’ well-being was affected and provides insights into coping mechanisms.