Observations of sea ice influence on the littoral sediment exchange,North Zealand,Denmark

Nielsen, Niels: Observations of sea ice influence on the littoral sediment exchange, North Zealand, Denmark. Geografisk Tidsskrift 88:61–67. Copenhagen. 1988.

In 1985 and 1986 monthly surveys of sediment volumes were carried out on a sandy beach and its nearshore platform at the north coast of Zealand. Both winters in the research period had temperatures below average, and consequently abundant sea ice formations. ‘Ice winters’ in open Danish waters occur statistically about 1/3 of the winters. The appearance of sea ice resulted in marked loss of sediment from the whole littoral zone, but by far the largest net erosion could be detected on the nearshore plane. An important factor is assumed to be the interaction of waves with the icefoot and ice pile-ups. For the beach itself, ice-glazing of the beach surface and interstitial frost in the foreshore sediments caused wave erosion within and just off the swash zone due to variations of the percolation parameter. This dynamic was observed during both the freeze-up and thaw-up periods. On the backshore, wind-derived forms characterized the winter beach, but here the net sediment budget was less affected.     

Simultaneous measurements of turbulence over land and water

Turbulence and mean flow variables under unstable conditions are examined with special emphasis on the consequences of roughness and surface elevation change. An interpolation formula for _w ², between neutral and free convection, is shown to bring order to the data. The spectral distribution of vertical wind variance is found to be in good agreement with results over horizontal homogeneous terrain, both with respect to form and position. In particular, the length scale _m corresponding to the maximum of nS _w(n) is unchanged. Another turbulent length scale, (k/)z, is found to be substantially reduced in the disturbed zone of the internal boundary layer. To a first approximation, the flow-acceleration effect on the non-dimensional wind shear can be separated from the diabatic effect.     

Fluxes of dissolved combined neutral sugars (polysaccharides) in the Delaware estuary

This project examined concentrations, composition and turnover neutral sugars in the Delaware estuary to gain insights into dissolved inorganic nitrogen (DIN) use by heterotrophic bacteria and into the lability and diagenetic state of dissolved organic material (DOM) during passage through the estuary. Dissolved free monosaccharides were not measurable (<5 nM) in the estuary whereas concentrations of dissolved combined neutral sugars (DCNS) were high, much higher than observed in oceanic waters. DCNS made up a similar fraction of dissolved organic carbon (DOC) as in the oceanic waters examined to date, and the monosaccharide composition of the DCNS pool was similar to that of oceanic waters. The composition did not vary substantially within the estuary or seasonally, but it did vary among three size fractions of the organic matter pool. Glucose was enriched in the low molecular weight fraction of DOC and in particulate material, whereas the high molecular weight DOC fraction was slightly depleted in glucose. Depletion experiments indicated that DCNS is not used extensively on the day time scale in the Delaware estuary, although freshly-produced polysaccharides may still be important carbon sources for heterotrophic bacteria. The very low concentrations of free monosaccharides in the Delaware estuary help to explain why DIN use by heterotrophic bacteria is relatively low in this estuary. Although DOC-DIN interactions in the Delaware apparently differ from oceanic waters, the portion of DOM traced by DCNS, which is thought to be the labile fraction, appears to be similar to that of oceanic DOM, suggesting that organic material in the estuary is degraded extensively before being exported to the coastal ocean.     

Sensitivity of DaisyGIS to LAI: Implications for land use based modelling of nitrate leaching

Geografisk Tidsskrift, Danish Journal of Geography 106(2): 75–85, 2006

Scaling is an important issue when measuring, modelling and understanding coupled socio-environmental terrestrial systems. Scaling may be enhanced through the incorporation of remotely sensed data. This paper assesses the sensitivity of DaisyGIS to changes in the Leaf Area Index (LAI) and discusses the implications for land use based modelling of nitrate leaching using remote sensing based LAI estimates. It is shown how DaisyGIS simulates nitrate leaching quite well over the period 2001 to 2004 except for one plot during a season with winter rape. It was found that the model is sensitive to changes in LAI with increases of up to 262% on nitrate leaching rates when reducing LAI by 15%. At the same time, the nitrate leaching rates at the field level vary considerably due to local changes in the water balance determined by soil profile characteristics. DaisyGIS is already an important tool for aiding decision makers and this study has shown how remote sensing based LAI estimates may be a valuable tool for model parameterisation and potentially for model validation.     

A lateral model parameter correlation procedure for one-dimensional inverse modelling

We present a new, fast and versatile method, the lateral parameter correlation method, of invoking lateral smoothness in model sections of one-dimensional (1D) models. Modern, continuous electrical and electromagnetic methods are capable of recording very large data sets and except for a few cases, standard inversion methodology still relies on 1D models. In environments where the lateral rate of change of resistivity is small, 1D inversion can be justified but model sections of concatenated 1D models do not necessarily display the expected lateral smoothness.
The lateral parameter correlation method has three steps. First, all sounding data are inverted individually. Next, a laterally smooth version of each model parameter, one at a time, is found by solving a simple constrained inversion problem. Identity is postulated between the uncorrelated and correlated parameters and the equations are solved including a model covariance matrix. As a last step, all sounding data are inverted again to produce models that better fit the data, now subject to constraints by including the correlated parameter values as a priori values. Because the method separates the inversion from the correlation it is much faster than methods where the inversion and correlation are solved simultaneously, typically with a factor of 200–500.
Theoretical examples show that the method produces laterally smooth model sections where the main influence comes from the well-determined parameters in such a way that problems with equivalence and poor resolution are alleviated. A field example is presented, demonstrating the improved resolution obtained with the lateral parameter correlation method. The method is very flexible and is capable of coupling models from inversion of different data types and information from boreholes.     

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.     

Erosion-driven drawdown of atmospheric carbon dioxide: The organic pathway

Rapidly eroding, coastal mountain belts, where steep rivers and submarine channels connect upland sources to nearby marine sinks are hotspots of organic carbon transfer from life biomass, soil and exhumed bedrock into geological storage. Using observations from the Southern Alps of New Zealand, and Taiwan, we have mapped this organic pathway to geological carbon sequestration, and can evaluate the magnitude and efficiency of transfers between sources and sinks. We demonstrate that POC is harvested by landsliding, but importantly also by common and widespread surface runoff on steep hillslopes. Although terrestrially sourced POC is found in many sedimentary environments associated with mountain belts and frontier basins, it appears to be most abundantly trapped and preserved in marine turbidites. The loss of all forms of POC in onward transport through short, steep routing systems to this repository is limited. This is in marked contrast to larger routing systems, in which only the most resilient forms of POC survive into long-term deposition.     

Photo's from Proceedings of the Third MicroQuasar Workshop; Granada Worshop on Galactic Relativistic Jet Sources – Granada,Spain, 11–13 September 2000

The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe K region (1100 cm²). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin² . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations.