A critical evaluation of multi‐proxy dendroclimatology in northern Finland

Twentieth‐century summer (July–August) temperatures in northern Finland are reconstructed using ring widths, maximum density and stable carbon isotope ratios (δ¹³C) of Scots pine tree rings, and using combinations of these proxies. Verification is based on the coefficient of determination (r²), reduction of error (RE) and coefficient of efficiency (CE) statistics. Of the individual proxies, δ¹³C performs best, followed by maximum density. Combining δ¹³C and maximum density strengthens the climate signal but adding ring widths leads to little improvement. Blue intensity, an inexpensive alternative to X‐ray densitometry, is shown to perform similarly. Multi‐proxy reconstruction of summer temperatures from a single site produces strong correlations with gridded climate data over most of northern Fennoscandia. Since relatively few trees are required (<15) the approach could be applied to long sub‐fossil chronologies where replication may be episodically low. Copyright © 2010 John Wiley & Sons, Ltd.     

Atmospheric sulfur deposition and streamwater quality in Finland

The correlation between sulfate concentrations in Finnish headwater streams and atmospheric sulfate deposition has been studied by using data from the streamwater chemistry in August–September 1990 and computed S deposition from the anthropogenic emissions. The sulfate concentrations and acidity in water are interpolated and smoothed into a deposition model grid. These data are compared with geological and pedogeochemical (glacial till) background information. The areas where the streamwater SO₄ concentrations are mainly controlled by either anthropogenic S deposition or sulfur in till is estimated by applying the fuzzy Gustafsson-Kessel algorithm, which provides a soft clustering suitable for overlapping control factors. Residual areas can be well explained by the SO₄-rich Littorina clay deposits. The higher overall background SO₄ concentrations in streams in south Finland compared with central and northern Finland are an indisputable consequence of the heavier S deposition load in the south. However, anthropogenic sulfur deposition has a clear correlation with the sulfates in streamwaters only in northeastern Lapland impacted by the large industrial emissions in the Kola Peninsula. The secondary sulfide and sulfate minerals of marine Littorina sediments are dominating sources in the broad coastal belts, as are the primary sulfide minerals locally in the Pori-Vammala area, at the eastern end of the main sulfide ore belt between Lake Ladoga and the Gulf of Bothnia, in the Outokumpu area, and in the Peräpohja and central Lapland schist belts. Consequently, in addition to the anthropogenic deposition, there are natural sources of sulfur which cause acidity of streamwaters.     

The influence of nonlinear material properties and resistance to bending on the development of internal structures

A reexamination of Biot's internal instability analysis, including the effects of bending resistance and nonlinear material properties, shows that internal buckling and oblique localized shearing into bands are the two end-member processes associated with internal instability. The first is a consequence of a high anisotropy which is an intrinsic property of the original unstressed layering or foliation. The second is a consequence of a highly anisotropic material response to perturbations which is induced during the initial uniform compression if material properties are nonlinear. The incremental anisotropy generating the instability is associated with planes of least resistance to shearing in directions parallel to the initial compression in the first case and at 45° to the initial compression in the second case.     

The effects of stock size and environmental variability on Cape hake recruitment in Namibia: an unsolved puzzle (a comment on Kainge et al. 2013)

Measuring and forecasting recruitment are central to the understanding and management of fish stocks. Kainge et al. (2013) studied the effect of spawning stock size and environmental fluctuations on the recruitment levels of the Cape hake Merluccius capensis in Namibia. However, their study contains some flaws that undermine the conclusion that Cape hake recruitment is under the influence of upwelling in summer. Until those flaws are properly addressed, this conclusion, in our view, should be treated with caution.     

Weathering of phlogopite in simulated bioleaching solutions

The purpose of this study was to examine structural alterations of finely ground phlogopite, a trioctahedral mica, when exposed to acid, iron- and sulfate-rich solutions typical of bioleaching systems. Phlogopite suspensions were supplemented with ferrous sulfate and incubated with iron- and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans) at 22 °C. As bacteria oxidized ferrous iron, ferric iron thus formed partially precipitated as K-jarosite. K-jarosite precipitation was contingent on the preceding ferrous iron oxidation by bacteria and the release of interlayer-K from phlogopite. This chemically and microbially induced weathering involved alteration of phlogopite to a mixed layer structure that included expansible vermiculite. The extent of phlogopite weathering and structure expansion varied with duration of the contact, concentration of ferrous iron and phlogopite, and the presence of monovalent cations (NH₄⁺, K⁺, or Na⁺) in the culture solution. NH₄⁺ and K⁺ ions (100 mM) added to culture suspensions precipitated as jarosite and thereby effectively prevented the loss of interlayer-K and structural alteration of phlogopite. Additional Na⁺ (100 mM) was insufficient to precipitate ferric iron as natrojarosite and therefore the precipitation was coupled with interlayer-K released from phlogopite. When ferrous iron was replaced with elemental sulfur as the substrate for A. ferrooxidans, the weathering of phlogopite was based on chemical dissolution without structural interstratification. The results demonstrate that iron oxidation and the concentration and composition of monovalent ions can have an effect on mineral weathering in leaching systems that involve contact of phlogopite and other mica minerals with acid leach solutions.     

An Analysis and Implications of Alternative Methods of Deriving the Density (WPL) Terms for Eddy Covariance Flux Measurements

We explore some of the underlying assumptions used to derive the density or WPL terms (Webb et al. (1980) Quart J Roy Meteorol Soc 106:85–100) required for estimating the surface exchange fluxes by eddy covariance. As part of this effort we recast the origin of the density terms as an assumption regarding the density fluctuations rather than as a (dry air) flux assumption. This new approach, which is similar to the expansion/compression approach of Liu (Boundary-Layer Meteorol 115:151–168, 2005), eliminates the dry-air mean advective vertical velocity from the development of the WPL terms and allows us to directly compare Liu’s assumptions for deriving the WPL terms with the analogous assumptions appropriate to the original expression of the WPL terms. We suggest, (i) that the main difference between these two approaches lies in the interpretation of the turbulent exchange flux, and (ii) that the original WPL formulation is the more appropriate approach. Given the importance of the WPL terms to accurate and reliable measurements of surface exchange fluxes, a careful analysis of their origins and their proper mathematical expression and interpretation is warranted.     

The optical depth sensor (ODS) for column dust opacity measurements and cloud detection on martian atmosphere

A lightweight and sophisticated optical depth sensor (ODS) able to measure alternatively scattered flux at zenith and the sum of the direct flux and the scattered flux in blue and red has been developed to work in martian environment. The principal goals of ODS are to perform measurements of the daily mean dust opacity and to retrieve the altitude and optical depth of high altitude clouds at twilight, crucial parameters in the understanding of martian meteorology. The retrieval procedure of dust opacity is based on the use of radiative transfer simulations reproducing observed changes in the solar flux during the day as a function of 4 free parameters: dust opacity in blue and red, and effective radius and effective width of dust size distribution. The detection of clouds is undertaken by looking at the time variation of the color index (CI), defined as the ratio between red and blue ODS channels, at twilight. The retrieval of altitude and optical depth of clouds is carried out using a radiative transfer model in spherical geometry to simulate the CI time variation at twilight. Here the different retrieval procedures to analyze ODS signals, as well as the results obtained in different sensitivity analysis are presented and discussed.     

Assessment of recent eutrophication and climate influence in the Archipelago Sea based on the subfossil diatom record

Two short sediment cores from the Archipelago Sea in the northern Baltic Sea were examined for their siliceous microfossils in order to study recent eutrophication in the area. The diatom record was divided into diatom assemblage zones. Locally weighted weighted averaging regression and calibration was applied for the quantitative reconstruction of past TN concentrations. The cores were dated using radiometric (²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs) methods. The diatom assemblages in the topmost zones in both cores indicate eutrophication during the last decade. TN reconstructions partially fail to trace the actual measured TN concentrations. Especially from the late 1980s to the mid 1990s, the dominating diatom species are more influenced by other factors, such as the length of the ice season, than by nutrient concentrations. It seems that in the Archipelago Sea, diatom assemblages are principally governed by climatic fluctuations with a moderate influence of eutrophication in recent years. The peak in sedimentation in the early 1990s coincides with the short ice seasons indicating that sedimentation may increase with decreasing ice-cover extent due to warming climate.