Potential impact of climate change on ecosystems of the Barents Sea Region

The EU project BALANCE (Global Change Vulnerabilities in the Barents region: Linking Arctic Natural Resources, Climate Change and Economies) aims to assess vulnerability to climate change in the Barents Sea Region. As a prerequisite the potential impact of climate change on selected ecosystems of the study area has to be quantified, which is the subject of the present paper. A set of ecosystem models was run to generate baseline and future scenarios for 1990, 2020, 2050 and 2080. The models are based on data from the Regional Climate Model (REMO), driven by a GCM which in turn is forced by the IPCC-B2 scenario. The climate change is documented by means of the Köppen climate classification. Since the multitude of models requires the effect of climate change on individual terrestrial and marine systems to be integrated, the paper concentrates on a standardised visualisation of potential impacts by use of a Geographical Information System for the timeslices 2050 and 2080. The resulting maps show that both terrestrial and marine ecosystems of the Barents region will undergo significant changes until both 2050 and 2080.     

Thermochemolysis of organic matter preserved in stalagmites: A preliminary study

The analysis of organic matter (OM) preserved in stalagmites is a growing field, but there have been few studies of biomarker compounds such as lignin phenols that are widely used in other palaeoenvironmental contexts. Here we present a preliminary qualitative study of the OM in six stalagmite samples from contrasting environments, using thermochemolysis in the presence of tetramethylammonium hydroxide (TMAH). The results indicate that a wide variety of products is preserved, including several potential lignin-derived compounds, but also that further research is needed to maximise compound recovery and allow the analysis of dissolved OM preserved in stalagmites to reach its full potential.     

Shock metamorphism in sillimanite from the Haughton impact structure,Devon Island,Canada

Clasts of shocked garnet-sillimanite gneisses comprise a minor fraction of the allochthonous breccia at the Haughton impact structure. Refractive indices of the diaplectic and fused components of the gneisses, and reduced specific gravity indicate shock pressures from 35 to 55±5 GPa and effective post-shock temperatures from 500° to 1,000° C in a suite of selected samples.Sillimanites remain birefringent but display several effects of shock metamorphism. Shock-produced planar features and planar fractures are highly developed; optic axial angle (2V _y ) increases from near normal (26°) to over 80° within a sample; there is a reduction in optical relief and a development of a pale brown colouring which generally deepens in shade as shock level increases. There is no unambiguous evidence, optically or from X-ray investigation, of a high-pressure Al₂SiO₅ polymorph or breakdown to mullite and silica. The highly shocked sillimanites have anomalous K₂O contents from 0.11% to 0.92%. Potassium appears to substitute for aluminum and, to a lesser degree, for iron while retaining sillimanite stoichiometry, and the amount of substitution generally reflects increased shock level. The source of the contributed potassium is the coexisting shock-fused feldspar glass. The glass of each sample is derived primarily from melted alkali feldspar with a minor and varied admixture from the breakdown of mafic minerals. The glasses are depleted in K₂O, although Na₂O is unaffected, and the extent of depletion can be correlated with the increased K₂O content of the associated sillimanite. The incorporation of potassium in shocked sillimanites is a function of both degree of shock deformation and availability of potassium from other coexisting shocked phases. It is speculated that the brown colouration is a function of ferrous iron content and may reflect post-crater thermal history rather than shock level.Contribution from the Earth Physics Branch No. 951     

Identifying “free” and “bound” lipid fractions in stalagmite samples: An example from Heshang Cave,Southern China

Stalagmites are good archives for paleoecological change, as they are easy to date, and contain multiple environmental proxy records, including climatic records from oxygen isotopes. Lipid biomarkers preserved within stalagmites have recently been used to investigate changes in the overlying soil and vegetation. However, the understanding of lipid records from stalagmites is still at an early stage, and is hindered by the low abundances of lipids preserved and the complexity of the organic matter signal. Here the first results of a sequential extraction procedure are presented, that enables examination of the distribution patterns of “free” (solvent extraction) and “bound” (including physically bound within the calcite matrix and chemically bound to macromolecules) lipids in a stalagmite from southern China. In both groups the dominant compounds are saturated fatty acids, which are an order of magnitude more abundant in the “bound” phase. n-alkanes and n-alcohols chiefly appear in the “free” lipids. In contrast, 3-hydroxy acids are predominantly released under strong acid reflux conditions, suggesting a principal input from bacterial membrane compounds. A direct comparison between the present results and the published data from an Ethiopian stalagmite shows significant differences in the lipid signals from separate sites, with a stronger microbial signal in the Chinese sample. This preliminary investigation of lipid distributions in different modes highlights the importance of microbial geochemical processes in karst systems and supports the use of stalagmites in paleoecological reconstruction.     

Estimating Potential Evaporation over a Hill

A simple analytical model of the effect of a hill on potential evaporation (i.e., evaporation from well-watered vegetation) is presented. It is shown to reproduce the results from a two-dimensional non-linear numerical model. The analytical model is used to demonstrate the sensitivity of the changes in evaporation to surface resistance, aerodynamic resistance, temperature, slope and sun angle. Methods used by MORECS (Meteorological Office Regional Evaporation Calculation System) to estimate the potential evaporation at high elevations, and by Numerical Weather Prediction models to represent sub-grid scale hills, take account of the change in altitude but neglect the slope effects. A slope of 20 degrees, which is typical of upland terrain in the U.K., increases the potential evaporation by about 5%.     

Responses of humpback whales to a changing climate in the Southern Hemisphere: Priorities for research efforts

Globally, baleen whales were severely depleted by historic whaling. Recovering populations have been observed to alter their behaviour. These changes have been attributed to climate change in some cases and raise concerns over the successful recovery of baleen whale populations. Current data-driven statistical habitat and behavioural models have proven useful for addressing questions of whale distribution changes within their limitations. Given observed changes in oceanic conditions, a new approach to managing baleen whale population recovery is necessary. Model predictions of future whale movements and distributions under climate change scenarios are vital to enable adequate conservation management. This paper presents a new perspective on understanding the impacts of climate change on humpback whales, arguing the need for a system-based multidisciplinary research approach. Our approach includes coupled, mechanistic models based upon robust ecological principles, and integrates key physical, biogeochemical, biological and ecological modules to address long-term changes associated with climate change. To illustrate the need for this system-based multidisciplinary approach, we focus on Southern Hemisphere humpback whales, the recovery of which may be impacted by rapid changes in habitat conditions brought about by anthropogenic climate change.     

Coordination nature of aluminum (oxy)hydroxides formed under the influence of tannic acid studied by X-ray absorption spectroscopy

The effect of biomolecules on the mechanisms of the formation and nature of the transformation products of Al (oxy)hydroxides at the atomic and molecular levels and the impact on their nano-scale surface chemistry remain to be uncovered. In this article, the coordination structure of Al in Al (oxy)hydroxides formed under the influence of tannic acid was studied with X-ray absorption near edge structure (XANES) spectroscopy. Al K-edge and L-edge spectra show that as the tannate/Al molar ratio (MR) was increased from 0, 0.001, 0.01 to 0.1, the coordination number of Al changed from the sixfold coordination to mixed six-, five-, and/or fourfold coordination in the structural network of the Al (oxy)hydroxides formed under the increasing perturbation of tannic acid. In O K-edge spectra, the intensity of the peak assigned to the π^∗ at 532.1 eV increased as the tannate/Al MR increased, with the spectrum of the Al precipitate formed at a tannate/Al MR of 0.1 being almost identical to that of tannic acid. These results indicate that tannate ligands are incorporated into the structural network of short-range ordered Al (oxy)hydroxides to perturb their structural configuration during the formation of Al precipitates under the influence of tannic acid. With increasing tannate/Al MR, the Al (oxy)hydroxides decreased in amount and developed structural defects and the Al-tannate precipitates increased in amount. The decrease in the coordination number of Al in the Al (oxy)hydroxides is attributed to steric and electronic factors which cause the change in Al-O bonding, because Al is complexed with tannate which has different functional groups and is much larger in size compared with OH and H₂O ligands. The surface reactivity of a metal-O bond is related to its covalency and coordination geometry. The findings obtained in the present study are, thus, of fundamental significance in understanding the structural and surface chemistry of Al (oxy)hydroxides and their impact on the transformation, transport, and fate of nutrients and pollutions in the environment.     

R.W. Stewart

Abstract

The physical mechanism that causes an interdecadal oscillation in a coarse resolution sector ocean model forced by mixed boundary conditions is studied. The oscillation is characterized by large fluctuations in convective activity and air/sea heat exchange on a decadal timescale. Changes in the subsurface temperature and surface salinity are essential for the existence of the oscillation. It is shown that a large part of these variations can be explained with the hypothesis of a constant ocean velocity field. This may easily lead to the erroneous conclusion that the oscillation is mainly a “nondynamical” phenomenon. In this paper it is demonstrated that the ocean dynamics play an essential role in explaining decadal oscillations.     

Sensitivity of an ecosystem model to hydrology and temperature

We tested the sensitivity of a dynamic ecosystem model (LPJ-GUESS) to the representation of soil moisture and soil temperature and to uncertainties in the prediction of precipitation and air temperature. We linked the ecosystem model with an advanced hydrological model (JULES) and used its soil moisture and soil temperature as input into the ecosystem model. We analysed these sensitivities along a latitudinal gradient in northern Russia. Differences in soil temperature and soil moisture had only little influence on the vegetation carbon fluxes, whereas the soil carbon fluxes were very sensitive to the JULES soil estimations. The sensitivity changed with latitude, showing stronger influence in the more northern grid cell. The sensitivity of modelled responses of both soil carbon fluxes and vegetation carbon fluxes to uncertainties in soil temperature were high, as both soil and vegetation carbon fluxes were strongly impacted. In contrast, uncertainties in the estimation of the amount of precipitation had little influence on the soil or vegetation carbon fluxes. The high sensitivity of soil respiration to soil temperature and moisture suggests that we should strive for a better understanding and representation of soil processes in ecosystem models to improve the reliability of predictions of future ecosystem changes.     

The Haughton Impact Structure,Devon Island,Canada: Setting and History of Investigations

Abstract— Although mapped initially as a piercement dome, subsequent discovery of shock metamorphism in clasts of an impact breccia, shatter cones in outcrops of uplifted target rocks and morphological and geophysical characteristics consistent with a complex crater, confirmed a meteorite impact origin for the Haughton structure, Devon Island. Results of three field investigations carried out prior to 1984 defined a complex crater, 20 km in diameter, formed in a lower Paleozoic sedimentary sequence overlying gneisses of the Precambrian basement. The distribution of allochthonous breccia overlying the disturbed target rocks and of the sediments deposited in the crater-filling lake were mapped. A Miocene or possibly Holocene age for the crater was based on paleo-flora and fauna assemblages from the lake sediments. Gravity and magnetic surveys revealed anomalies coincident with the crater, but not interpretable from surface lithologies. Some of the early investigations were of a reconnaissance nature and results and interpretation can only be considered preliminary. Other studies that were carried out in some detail, petrographic investigations in particular, require complementary work for a fuller understanding of their significance. As a result, in 1984 the HISS (Haughton Impact Structure Studies) group carried out a program of detailed geological mapping and sampling, and seismic, gravity, and magnetic surveys in an attempt to improve the definition of the surface and subsurface nature of Haughton, and to formulate a more complete understanding of its formation and subsequent history. Results of these various studies are presented in the eight succeeding papers of this volume.