Cross-basin differences in particulate organic carbon export and flux attenuation in the subtropical North Atlantic gyre

We compared in-situ and satellite-derived measures of the biological carbon pump efficiency at the two seemingly similar subtropical North Atlantic gyre time series sites, the Bermuda time series (BATS, Bermuda Atlantic time-series study and OFP, ocean flux program) in the western gyre and the ESTOC time series (European station for time-series in the ocean, Canary Islands) in the eastern gyre. Satellite-derived surface chlorophyll a was slightly lower at Bermuda compared to ESTOC (annual average of 0.10±0.04 vs. 0.14±0.05-mg-m^?3), as was satellite-derived primary production (annual average of 380±77 vs. 440±80-mg C-m^?2 d^?1). However, export production normalized to primary production (export ratio) was higher at Bermuda by a factor of 2–3 when estimated using mesopelagic traps moored at 500-m depth and by a factor of 3–4 when estimated using surface-tethered drifting traps. When averaged seasonally, flux at BATS was highest in spring (March, April, May) at all depths followed by summer (June, July, August) and decreasing towards fall, but this seasonality was less visible at ESTOC. Seasonal comparison showed the fastest flux attenuation at Bermuda in winter and spring, coinciding with the highest POC flux. POC/PIC ratios derived from the moored traps were significantly higher at BATS than at ESTOC in fall and winter, but this difference was not significant in spring (p>0.05). This study shows that while the western and eastern Atlantic subtropical gyres have similar rates of primary production, the biological carbon pump differs between the two provinces. Higher new nutrient input observed at Bermuda compared to ESTOC might explain part of the difference in export ratio but alone is insufficient. Greater winter mixed-layer depths and higher mesoscale eddy activity at Bermuda resulting in pulsed production events of labile organic matter might explain both the higher export flux and export ratios found at Bermuda.     

Coupling an ocean wave model to an atmospheric general circulation model

A coupled model, consisting of an ocean wave model and an atmospheric general circulation model (AGCM), is integrated under permanent July conditions. The wave model is forced by the AGCM wind stress, whereas the wind waves modify the AGCM surface fluxes of momentum, sensible and latent heat. We investigate the following aspects of the coupled model: how realistic are the wave fields, how strong is the coupling, and how sensitive is the atmospheric circulation to the spatially and temporally varying wave field. The wave climatology of the coupled model compares favorably with observational data. The interaction between the two models is largest (although weak) in the storm track in the Southern Hemisphere. Young windsea, which is associated with enhanced surface fluxes is generated mostly in the equatorward frontal area of an individual cyclone. However, the enhancement of the surface fluxes is too small to significantly modify the climatological mean atmospheric circulation.This paper was presented at the Second International Conference on Modelling of Global Climate Variability, held in Hamburg 7–11 September 1992 under the auspices of the Max Planck Institute for Meteorology. Guest Editor for these papers is L. Dümenil     

Galaxies in Interaction

Posters: Because of the large number of contributions, some oral presentations had to be transferred into Posters. The reader is referred to the final programme for the actual allocation of Posters. A01 Chemical Enrichment of the Intracluster Medium A02 Structural analysis of high‐velocity clouds – Evidence for an interaction between the Milky Way and the Magellanic System A03 Multi‐Phase Chemo‐Dynamical SPH code for galaxy evolution A04 The proper motion of M33 A05 Wavelet analysis of Intra–group Light in Hickson Compact Groups A06 Evidence for an evolutionary connection between early and late type dwarf galaxies A07 Dwarf Galaxies in the NGC 5846 Group A08 X‐ray spectroscopy of serendipitous clusters of galaxies in XMM‐Newton observations A09 Evolution of smale scale systems of galaxies: X‐ray detected E+S galaxy pairs A10 Modelling Star Formation in Interacting Galaxies A11 NGC 1427A – the beginning of the end: a lonely dwarf irregular entering the dense core of the Fornax cluster A12 Dwarf galaxies in galaxy groups: Photo‐evaporation, orbits and gas stripping A13 High resolution stellar kinematics for the central component of the Polar Ring Galaxy NGC 4650A A14 The Influence of Environment on the Morphological Evolution of Disk‐Dominated Galaxies A15 Interactions and star formation in galaxies A16 Dust Condensations and Molecular Clouds in Interacting Spirals A17 Star formation rates and kinematics of modelled interacting galaxies A18 Evolution of Galaxies and the Tully–Fisher Relation A19 Evolution and Collision of Galaxies on the GRID A20 Multiwavelength observations of two S+E merger candidates: the Medusa and NGC 4441 A21 Interacting Galaxies in Small Galaxy Groups A22 Virial and total masses of galaxy triplets in the Local Supercluster A23 Simulations of Interaction Processes of Galaxies with the Intra‐Cluster Medium A24 Chemical evolution of the thick and thin disks of our Galaxy A25 Dust properties of UV‐bright galaxies at z ∼ 2 A26 Simulation of the Gravitational Collapse and Fragmentation of Rotating Molecular Clouds A27 NGC 5719/13: interacting spirals forming a counter‐rotating stellar disc A28 Starbursts in very metal‐poor dwarfs due to interactions and mergers: link to the processes in the high‐redshift young galaxies A29 Testing galaxy evolution in the field: morphology and properties of the diffuse X‐ray emission in shell galaxies A30 Effects of galactic winds on dIrrs with particular emphasis on NGC 1569 and the refill of superbubble cavities A31 Galaxy formation through merging at z ≈ 2 A32 3D simulations of the ISM‐ICM interaction of disk galaxies in clusters A33 Gas replenishment in ram pressure stripped disk galaxies A34 New Results on the Kinematics of the Outer Cluster System of NGC 1399 A35 Chemical gradient evolution in massive galaxy disk due to its minor merger with dwarf galaxy A36 The complex kinematics of galaxies in Hickson 62 A37 Dust in the outer regions of interacting galaxies A38 Dynamical interaction of M31 and M32 A39 A comparative study of galaxy properties in low‐ and high density environment A40 Compact Groups in Dense Environment: The Case of IC1370 A41 The Star Formation History of CG J1720‐67.8 A42 Galaxy populations in the infall regions of intermediate redshift clusters A43 The study of gravitational fragmentation in two‐clumps collisions A44 Star Formation Activity in Galaxy Clusters Near and Far A45 An Exploration of the Merging History of the Local Starburst Galaxy, NGC 3310 A46 The high‐velocity clouds of M31: tracers of galactic evolution A47 The Properties of Fossil Groups     

Atmospheric nitrogen inputs into the North Sea: effect on productivity

The ANICE (Atmospheric Nitrogen Inputs into the Coastal Ecosystem) project addressed the atmospheric deposition of nitrogen to the North Sea, with emphasis on coastal effects. ANICE focused on quantifying the deposition of inorganic nitrogen compounds to the North Sea and the governing processes. An overview of the results from modelling and experimental efforts is presented. They serve to identify the role of the atmosphere as a source of biologically essential chemical species to the marine biota. Data from the Weybourne Atmospheric Observatory (UK) are used to evaluate the effect of short episodes with very high atmospheric nitrogen concentrations. One such episode resulted in an average deposition of 0.8 mmol N m⁻² day⁻¹, which has the potential to promote primary productivity of 5.3 mmol C m⁻² day⁻¹. This value is compared to long-term effects determined from model results. The total calculated atmospheric deposition to the North Sea in 1999 is 948 kg N km⁻¹, i.e. 0.19 mmol N m⁻² day⁻¹ which has the potential to promote primary productivity of 1.2 mmol C m⁻² day⁻¹. Detailed results for August 1999 show strong gradients across the North Sea due to adjacent areas where emissions of NO_x and NH₃ are among the highest in Europe. The average atmospheric deposition to the southern part of the North Sea in August 1999 could potentially promote primary production of 2.0 mmol C m⁻² day⁻¹, i.e. 5.5% of the total production at this time of the year in this area of the North Sea. For the entire study area the atmospheric contribution to the primary production per m² is about two-third of this value. Most of the deposition occurs during short periods with high atmospheric concentrations. This atmospheric nitrogen is almost entirely anthropogenic in origin and thus represents a human-induced perturbation of the ecosystem.     

Spatial characteristics of ocean surface waves

The spatial variability of open ocean wave fields on scales of O (10km) is assessed from four different data sources: TerraSAR-X SAR imagery, four drifting SWIFT buoys, a moored waverider buoy, and WAVEWATCH III^? model runs. Two examples from the open north-east Pacific, comprising of a pure wind sea and a mixed sea with swell, are given. Wave parameters attained from observations have a natural variability, which decreases with increasing record length or acquisition area. The retrieval of dominant wave scales from point observations and model output are inherently different to dominant scales retrieved from spatial observations. This can lead to significant differences in the dominant steepness associated with a given wave field. These uncertainties have to be taken into account when models are assessed against observations or when new wave retrieval algorithms from spatial or temporal data are tested. However, there is evidence of abrupt changes in wave field characteristics that are larger than the expected methodological uncertainties.     

Same space – different perspectives: comparative analysis of geographic context through sketch maps and spatial video geonarratives

ABSTRACT

The importance of including a contextual underpinning to the spatial analysis of social data is gaining traction in the spatial science community. The challenge, though, is how to capture these data in a rigorous manner that is translational. One method that has shown promise in achieving this aim is the spatial video geonarrative (SVG), and in this paper we pose questions that advance the science of geonarratives through a case study of criminal ex-offenders. Eleven ex-offenders provided sketch maps and SVGs identifying high-crime areas of their community. Wordmapper software was used to map and classify the SVG content; its spatial filter extension was used for hot spot mapping with statistical significance tested using Monte Carlo simulations. Then, each subject’s sketch map and SVG were compared. Results reveal that SVGs consistently produce finer spatial-scale data and more locations of relevance than the sketch maps. SVGs also provide explanation of spatial-temporal processes and causal mechanisms linked to specific places, which are not evident in the sketch maps. SVG can be a rigorous translational method for collecting data on the geographic context of many phenomena. Therefore, this paper makes an important advance in understanding how environmentally immersive methods contribute to the understanding of geographic context.     

Evaluating the impact of visualization of wildfire hazard upon decision-making under uncertainty

The paper investigates whether the methods chosen for representing uncertain geographic information aid or impair decision-making in the context of wildfire hazard. Through a series of three human subject experiments, utilizing 180 subjects and employing increasingly difficult tasks, this research evaluates the effect of five different visualizations and a text-based representation on decision-making under uncertainty. Our quantitative experiments focus specifically on the task of decision-making under uncertainty, rather than the task of reading levels of uncertainty from the map. To guard against the potential for generosity and risk seeking in decision-making under uncertainty, the experimental design uses performance-based incentives. The experiments showed that the choice of representation makes little difference to performance in cases where subjects are allowed the time and focus to consider their decisions. However, with the increasing difficulty of time pressure, subjects performed best using a spectral color hue-based representation, rather than more carefully designed cartographic representations. Text-based and simplified boundary encodings were among the worst performers. The results have implications for the performance of decision-making under uncertainty using static maps, especially in the stressful environments surrounding an emergency.     

Eco-hydrological versus supply-limited weathering regimes and the potential for biotic enhancement of weathering at the global scale

Biotic enhancement of weathering (BEW) has been proposed to substantially alter the geologic C cycle but the large scale impact of small scale biotic processes remains elusive, especially when compared to large scale drivers of weathering such as climate and crustal uplift. A global land surface model was used to estimate the potential strength of BEW for two contrasting types of weathering regimes that are either limited by the supply of fresh parent material by uplift or controlled by the climatic and eco-hydrological conditions. The biospheric effect on soil CO₂ in the model was then removed in order to determine the reduction of weathering rates and thereby to infer BEW. It was found that only those areas that are not supply limited are susceptible to biotic enhancement. This indicates that the potential for BEW depends directly on the supply of fresh material and thus on crustal uplift.     

Model Atmospheres of AGB Stars: Dynamics, Molecules and Dust

The atmospheres and circumstellar envelopes of AGB stars are characterized by complex physical phenomena like shock waves caused by stellar pulsation or formation of molecules and dust which often lead to a heavy mass loss and have a strong influence on IR properties as observed by ISO. To allow a physical interpretation of various observations we have constructed improved dynamical model atmospheres of long-period variables. In this contribution we mainly investigate the dependence of the atmospheric structure and its variability on stellar pulsation, molecular opacities and time-dependent dust formation. IR spectra resulting from our models are discussed in detail by Loidl et al. (1997b) and compared to ISO-SWS spectra obtained by Hron et al. (1997). This revised version was published online in August 2006 with corrections to the Cover Date.