Export Production in the Subarctic North Pacific over the Last 800 kyrs: No Evidence for Iron Fertilization?

The subarctic North Pacific is a high nitrate-low chlorophyll (HNLC) region, where phytoplankton growth rates, especially those of diatoms, are enhanced when micronutrient Fe is added. Accordingly, it has been suggested that glacial Fe-laden dust might have increased primary production in this region. This paper reviews published palaeoceanographic records of export production over the last 800 kyrs from the open North Pacific (north of ∼35°N). We find different patterns of export production change over time in the various domains of the North Pacific (NW and NE subarctic gyres, the marginal seas and the transition zone). However, there is no compelling evidence for an overall increase in productivity during glacials in the subarctic region, challenging the paradigm that dust-born Fe fertilization of this region has contributed to the glacial draw down of atmospheric CO₂. Potential reasons for the lack of increased glacial export production include the possibility that Fe-fertilization rapidly drives the ecosystem towards limitation by another nutrient. This effect would have been exacerbated by an even more stable mixed layer compared to today. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electromagnetic Subsurface Imaging. A Case for an Adaptive Born Approximation

The process of interpretation of electromagnetic data has many facets of which fast approximate interpretation techniques is an intriguing one. A new variant of the Born approximation – the Adaptive Born approximation – is presented and exemplified through 1D and 2D imaging techniques for transient electromagnetic data. The Adaptive Born approximation is generally applicable in approximate inversion schemes for inductive electromagnetic data as a one-pass imaging algorithm. Though it is as simple to use as the ordinary Born approximation, it offers a more accurate inverse mapping.In the first part of this paper an attempt will be made to give an overview of fundamental concepts in electromagnetic subsurface imaging relevant for approximate inverse mappings and to outline major trends in present day modeling and inversion of electromagnetic data. This is of course an impossible task – certainly for this author – and much important work will not be mentioned in the limited space of the following. My apologies to the people who are not mentioned and whose research is not given credit here though it should have been. Naturally, my choice of references reflects the schools and circles I have been subjected to, but I hope that the list of references to developments in electromagnetic methods will point to papers of importance and thereby to other references for the interested reader.     

TAC management in North Sea flatfish fisheries

The Common Fisheries Policy of the European Union adopted in 1983 is primarily focused on a science-based TAC management system with fixed national quota shares. The quality of the assessments of plaice and sole, the consistency of the scientific advice, the congruency of the management decisions, and the enforcement of the regulations are reviewed over a 15-year period. The conclusion is that there have been problems at each level, with the ultimate effect that the policy has not been able to restrict fishing mortality and that the level of overexploitation has only increased. It is argued that the present TAC system has created more problems than it has resolved. Attention is drawn to the autonomic economic developments within the fishery and to the potential for managing the fishery more effectively from the cost side rather than the profit side.     

Seep carbonate formation controlled by hydrothermal vent complexes: a case study from the Vøring Basin, the Norwegian Sea

Several hundred hydrothermal vent complexes were formed in the Vøring Basin as a consequence of magmatic sill emplacement in the late Palaeocene. The 6607/12-1 exploration well was drilled through a 220-m-thick sequence of Eocene–Miocene diatomites with carbonate nodules above the apex of one of these vent complexes. Analysed calcites and dolomites from this interval have isotopic signatures typical for methane seep carbonates, with low ¹³C signatures of –28 to –54 PDB. The data suggest that the vent complex acted as a fluid migration pathway for about 50×10⁶ years after its formation, leading to near-surface microbial activity and seep carbonate formation.     

Eine Methode zur Registrierung der räumlichen Verteilung der Globalstrahlung in einem Pflanzenbestand

Zusammenfassung Mit zwei Pyranometern wird gleichzeitig und auf gleichem Papier die Globalstrahlung über und in einem Pflanzenbestand registriert. Im Laufe der Registrierung bewegt sich der Strahlungsempf?nger im Bestand mit konstanter Geschwindigkeit entlang einer horizontalen Bahn. Die Apparatur und die Durchführung der Messung werden beschrieben.

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Summary Global radiation above and within a stand of plants is recorded simultaneous and on the same strip of paper. While the record is effectuated the receiver of the radiation is moved horizontally through the stand with constant speed. The equipment and the practical measuring are described.

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Résumé On a enregistré simultanément et sur la même bande d'enregistrement le rayonnement global au moyen de deux pyranomètres placés l'un au-dessus. l'autre à l'intérieur d'une culture. Durant l'enregistrement, l'appareil situé entre les plantes se dépla?ait de long d'une trajectoire horizontale et à une vitesse constante. On décrit ici l'appareillage et l'exécution des mesures.

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Mit 3 Textabbildungen     

From smallholders to transnationals: The impact of changing consumer preferences in the EU on Ghana’s pineapple sector

This paper explores the impact that a new type of pineapple, and subsequent changing consumer preferences in the Global North, has had on the livelihoods of pineapple growers in Ghana. The paper starts by tracing how research and development in Costa Rica by the world’s largest producers of pineapple, Del Monte and Dole, have resulted in a new variety MD2. This new pineapple type has been marketed in the EU through campaigns carried out by plantation companies via supermarkets. Consumer preferences have subsequently switched to MD2 away from the varieties which previously dominated the market, including the Ghanaian grown Smooth Cayenne. Ghanaian smallholders have experienced a dramatic drop in the demand for Smooth Cayenne and are unable to switch to growing MD2. The Ghanaian pineapple sector is consequently being restructured with large-scale pineapple farms, principally run by transnational companies, growing large quantities of MD2 for export. Through a detailed empirical study of the changing livelihoods of pineapple growers in two settlements in Ghana, we show how smallholders have been affected in differing ways as transnational companies have increasingly entered the market. Recent attempts to incorporate smallholders as producers of niche pineapple products are discussed. The paper illustrates the mutual benefits of linking global value chain analysis with livelihood analysis.     

Natural hazards in Nordic Countries

Compared to many areas of the world, the human losses caused by natural hazards are smaller in Nordic countries. This is mainly due to the low population density in the exposed areas. However, the economic losses are significant and the geohazards picture varies among the countries. The predominant natural hazards in Nordic countries are floods, landslides, and, with the exception of Denmark, snow avalanche. Volcanoes and earthquakes are major geohazards in Iceland, and parts of Norway are susceptible to seismic activity. Slidetriggered tsunamis also represent a threat to parts of the coastal areas of Nordic countries and Greenland.     

Coupled rainfall and water vapour stable isotope time series reveal tropical atmospheric processes on multiple timescales

High-frequency stable isotope data are useful for validating atmospheric moisture circulation models and provide improved understanding of the mechanisms controlling isotopic compositions in tropical rainfall. Here, we present a near-continuous 6-month record of O- and H-isotope compositions in both water vapour and daily rainfall from Northeast Australia measured by laser spectroscopy. The data set spans both wet and dry seasons to help address a significant data and knowledge gap in the southern hemisphere tropics. We interpret the isotopic records for water vapour and rainfall in the context of contemporaneous meteorological observations. Surface air moisture provided near-continuous tracking of the links between isotopic variations and meteorological events on local to regional spatial scales. Power spectrum analysis of the isotopic variation showed a range of significant periodicities, from hourly to monthly scales, and cross-wavelet analysis identified significant regions of common power for hourly averaged water vapour isotopic composition and relative humidity, wind direction, and solar radiation. Relative humidity had the greatest subdiurnal influence on isotopic composition. On longer timescales (weeks to months), isotope variability was strongly correlated with both wind direction and relative humidity. The high-frequency records showed diurnal isotopic variations in O- and H-isotope compositions due to local dew formation and, for deuterium excess, as a result of evapotranspiration. Several significant negative isotope anomalies on a daily scale were associated with the activity of regional mesoscale convective systems and the occurrence of two tropical cyclones. Calculated air parcel back trajectories identified the predominant moisture transport paths from the Southwest Pacific Ocean, whereas moisture transport from northerly directions occurred mainly during the wet season monsoonal airflow. Water vapour isotope compositions reflected the same meteorological events as recorded in rainfall isotopes but provided much more detailed and continuous information on atmospheric moisture cycling than the intermittent isotopic record provided by rainfall. Improved global coverage of stable isotope data for atmospheric water vapour is likely to improve simulations of future changes to climate drivers of the hydrological cycle.