The Tauern Window (Eastern Alps, Austria): a new tectonic map, with cross-sections and a tectonometamorphic synthesis

We present a tectonic map of the Tauern Window and surrounding units (Eastern Alps, Austria), combined with a series of crustal-scale cross-sections parallel and perpendicular to the Alpine orogen. This compilation, largely based on literature data and completed by own investigations, reveals that the present-day structure of the Tauern Window is primarily characterized by a crustal-scale duplex, the Venediger Duplex (Venediger Nappe system), formed during the Oligocene, and overprinted by doming and lateral extrusion during the Miocene. This severe Miocene overprint was most probably triggered by the indentation of the Southalpine Units east of the Giudicarie Belt, initiating at 23–21 Ma and linked to a lithosphere-scale reorganization of the geometry of mantle slabs. A kinematic reconstruction shows that accretion of European lithosphere and oceanic domains to the Adriatic (Austroalpine) upper plate, accompanied by high-pressure overprint of some of the units of the Tauern Window, has a long history, starting in Turonian time (around 90 Ma) and culminating in Lutetian to Bartonian time (45–37 Ma).     

Environmental consequence analyses of fish farm emissions related to different scales and exemplified by data from the Baltic--a review

The aim of this work is to review studies to evaluate how emissions from fish cage farms cause eutrophication effects in marine environments. The focus is on four different scales: (i) the conditions at the site of the farm, (ii) the local scale related to the coastal area where the farm is situated, (iii) the regional scale encompassing many coastal areas and (iv) the international scale including several regional coastal areas. The aim is to evaluate the role of nutrient emissions from fish farms in a general way, but all selected examples come from the Baltic Sea. An important part of this evaluation concerns the method to define the boundaries of a given coastal area. If this is done arbitrarily, one would obtain arbitrary results in the environmental consequence analysis. In this work, the boundary lines between the coast and the sea are drawn using GIS methods (geographical information systems) according to the topographical bottleneck method, which opens a way to determine many fundamental characteristics in the context of mass balance calculations. In mass balance modelling, the fluxes from the fish farm should be compared to other fluxes to, within and from coastal areas. Results collected in this study show that: (1) at the smallest scale (<1 ha), the "footprint" expressing the impact areas of fish cage farm often corresponds to the size of a "football field" (50-100 m) if the annual fish production is about 50 ton, (2) at the local scale (1 ha to 100 km2), there exists a simple load diagram (effect-load-sensitivity) to relate the environmental response and effects from a specific load from a fish cage farm. This makes it possible to obtain a first estimate of the maximum allowable fish production in a specific coastal area, (3) at the regional scale (100-10,000 km2), it is possible to create negative nutrient fluxes, i.e., use fish farming as a method to reduce the nutrient loading to the sea. The breaking point is to use more than about 1.1 g wet weight regionally caught wild fish per gram feed for the cultivated fish, and (4) at the international scale (>10,000 km2) related to the Baltic Proper, the contribution from fish farms to the overall nutrient fluxes are very small. We have also given two case-studies at the local scale where the impact of the fish farm emissions are greatest and the idea is to identify coastal areas unsuitable and suitable for fish cage farms and the reasons why. It should also be stressed that the results presented here are exemplified using emissions from fish farms, but that the underlying principles to evaluate the ecosystem effects of nutrient discharges from point source emissions are valid in a wider and more general perspective.     

Spatial response of two European atmospheric circulation classifications (data 1901–2010)

Air pressure field and circulation pattern frequencies were investigated to (1) locate and compare positions of the underlying pressure fields, (2) analyse the spatial dimension of affected areas, (3) create schematic maps of important circulation types and (4) compare the classification types in their response to the data. Two manual classifications were used, selected for the length of their time series and their applicability to a larger region: the Grosswetterlagen classification (GWLc) and the Vangengeim–Girs classification (VGc). Their time series were correlated with a global set of gridded monthly sea-level pressure data. Results show the different conceptual orientation of VGc (hemispheric) and GWLc (continental). The highest correlation values and the largest affected areas are visible in winter, where patterns frequently extended into northern Africa and western Asia. Schematic maps, illustrating the average location of main pressure centres, are provided for basic classes of both classifications. Re-arranging GWLc subtypes increases the classifications comparability with the VGc. Analysis of moving correlation coefficients reveals high fluctuations in the relation of both classifications over time.     

A Zonal Pathway for NADW in the South Atlantic

Several large deployments of neutrally buoyant floats took place within the Antarctic Intermediate (AAIW), North Atlantic Deep Water (NADW), and the Antarctic Bottom Water (AABW) of the South Atlantic in the 1990s and a number of hydrographic sections were occupied as well. Here we use the spatially and temporally averaged velocities measured by these floats, combined with the hydrographic section data and various estimates of regional current transports from moored current meter arrays, to determine the circulation of the three major subthermocline water masses in a zonal strip across the South Atlantic between the latitudes of 19°S and 30°S. We concentrate on this region because the historical literature suggests that it is where the Deep Western Boundary Current containing NADW bifurcates. In support of this notion, we find that a net of about 5 Sv. of the 15–20 Sv that crosses 19°S does continue zonally eastward at least as far as the Mid-Atlantic Ridge. Once across the ridge it takes a circuit to the north along the ridge flanks before returning to the south in the eastern half of the Angola Basin. The data suggest that the NADW then continues on into the Indian Ocean. This scheme is discussed in the context of distributions of dissolved oxygen, silicate and salinity. In spite of the many float-years of data that were collected in the region a surprising result is that their impact on the computed solutions is quite modest. Although the focus is on the NADW we also discuss the circulation for the AAIW and AABW layers.     

Diel Aquatic CO<Subscript>2</Subscript> System Dynamics of a Bermudian Mangrove Environment

Mangrove ecosystems play an important, but understudied, role in the cycling of carbon in tropical and subtropical coastal ocean environments. In the present study, we examined the diel dynamics of seawater carbon dioxide (CO₂) and dissolved oxygen (DO) for a mangrove-dominated marine ecosystem (Mangrove Bay) and an adjacent intracoastal waterway (Ferry Reach) on the island of Bermuda. Spatial and temporal trends in seawater carbonate chemistry and associated variables were assessed from direct measurements of dissolved inorganic carbon, total alkalinity, dissolved oxygen (DO), temperature, and salinity. Diel pCO₂ variability was interpolated across hourly wind speed measurements to determine variability in daily CO₂ fluxes for the month of October 2007 in Bermuda. From these observations, we estimated rates of net sea to air CO₂ exchange for these two coastal ecosystems at 59.8 ± 17.3 in Mangrove Bay and 5.5 ± 1.3 mmol m⁻² d⁻¹ in Ferry Reach. These results highlight the potential for large differences in carbonate system functioning and sea-air CO₂ flux in adjacent coastal environments. In addition, observation of large diel variability in CO₂ system parameters (e.g., mean pCO₂: 390–2,841 μatm; mean pH_T: 8.05–7.34) underscores the need for careful consideration of diel cycles in long-term sampling regimes and flux estimates.