| 1. |
- Routh, Joyanto, 1968-, et al.
(author)
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Sedimentary geochemical record of humanï¿œinduced environmental changes in the Lake Brunnsviken watershed, Sweden
- 2004
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In: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 49:5, s. 1560-1569
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Journal article (peer-reviewed)abstract
- Environmental changes in Lake Brunnsviken, its watershed, and the greater Stockholm region since the middle of the nineteenth century have left interpretable geochemical imprints in the bottom sediments. These human-induced perturbations within the lakeï¿œs watershed included agriculture, urbanization, sewage and industrial disposal, and water column aeration. Smaller d15Ntotal values, high organic carbon mass accumulation rates, low C:N ratios, and larger d13Corg values identify periods of increased nutrient delivery and elevated primary productivity in the lake. C: S ratios that change from high to low trace the transition from an oxic hypolimnion to an anoxic one during the periods of high productivity. Accumulations of redox-sensitive trace elements increase during the anoxic period and are further magnified during a time of industrial waste discharge into the lake. A recent decrease in black carbon concentrations in sediments reflects the conversion from wood and coal to cleaner forms of energy.
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| 2. |
- John Lowe, J., et al.
(author)
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Inter-regional correlation of palaeoclimatic records for the last Glacial-Interglacial Transition : A protocol for improved precision recommended by the INTIMATE project group
- 2001
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In: Quaternary Science Reviews. - 0277-3791. ; 20:11, s. 1175-1187
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Journal article (peer-reviewed)abstract
- The remit of the INTIMATE project of the INQUA Palaeoclimate Commission is to synthesise marine, terrestrial and ice-core data for the North Atlantic region during the Last Glacial-Interglacial Transition (LGIT: ca 13-1014C kyr BP; ca 15-11.5 ice-core kyr BP). A major problem, however, is the difficulty of effecting correlations at a temporal resolution that are adequate for defining 'leads' and 'lags' between the polar ice, terrestrial, marine, and atmospheric realms. The limitations of the dating and correlation methods currently employed are summarised, and new quality assurance protocols are proposed. These include recommendations on the contextual information that should accompany radiocarbon dates, procedures for radiocarbon calibration, the use of an event-stratigraphic approach in inter-regional correlations, and the more widespread use of time-parallel marker horizons (based on tephra layers, oxygen isotope stratigraphy, palaeomagnetic stratigraphy, and radiocarbon 'wiggle-matching') to underpin the geochronology and correlation of events during the LGIT. These protocols will be adopted by the INTIMATE project in future international, collaborative research and are recommended to other groups working on this important time period.
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| 7. |
- Morford, Jennifer L., et al.
(author)
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Sampling marine pore waters for Mn, Fe, U, Re and Mo: Modifications on diffusional equilibration thin film gel probes
- 2003
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In: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 285-286, s. 85-103
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Journal article (peer-reviewed)abstract
- Pore water metal profiles are important for identifying redox horizons and understanding trace metal geochemical cycling. The challenges of pore water sampling for trace metals are minimizing disturbance, especially at the sediment–water interface, and minimizing oxidation during sampling. We are investigating diffusional equilibration in thin films (DET) probes for obtaining pore water profiles. Our goal is to use probes for redox-sensitive trace metals U, Re and Mo, in addition to Mn and Fe, in coastal marine areas. Initial solution equilibration tests and laboratory core incubation experiments suggest that equilibration times for probes in sediments are approximately 24–48 h. Control tests suggest that the incubation does not alter the redox conditions in the pore waters. Pore water profiles from cores sampled by slicing, centrifuging and filtering (in a nitrogen atmosphere) and from probes are similar. Two modifications on the gel probe design were tested to determine their impact. (1) PVC wedges were attached to the backs of probes to increase the contact between sediments and the probe surface and to reduce the risk of forming channels along the probe surface, which might allow vertical pore water transport. Lower Fe concentrations were measured from probes without PVC wedges, but other metal profiles were similar. (2) A modified face frame was removed from the front of a probe, to reduce disturbance of the sediments during insertion and to increase the contact between the sediments and probe surface. Probes with modified face frames did not have increasing U and Mo concentrations with depth, whereas two of the three probes without face frames did have increasing concentrations. Increasing U and Mo concentrations at depth may be reflecting the influence of irrigating burrows and their supply of oxygen to reduced sediments, which could oxidize previously reduced metals. The distribution of burrows is heterogeneous and resulting profiles would also be expected to be heterogeneous in their response. Differences between probe profiles and sliced/centrifuged profiles are examined to gain insight into possible sampling artifacts. Peaks in the Re sliced/centrifuged profiles suggest a large Re flux to the overlying waters, which is neither calculated from probe profiles nor measured in benthic chamber samples. It is possible that heterogeneity at the sampling site in Buzzards Bay resulted in these differences; however, it is also possible that centrifugation releases Re from pore structures that would not be measured with less intrusive sampling methods, such as gel probes or benthic chambers.
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| 8. |
- Wörman, Anders, 1961-, et al.
(author)
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Kinematic model of solute transport in stream networks : Example with phosphate retention in Morsa watershed, Norway
- 2004
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In: Archives of Hydro-engineering and Environmental Mechanics. - 1231-3726. ; 51:1, s. 41-53
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Journal article (peer-reviewed)abstract
- A theoretical description of reactive solute transport in a network of stream channels is derived by convoluting unit solutions based on a physical representation of transport and topographical information of the distributions of solute load as well as pathways. The theory is applied to a generic analysis of the phosphate export in Morsa watershed due to the load from 620 individual households with a local wastewater treatment. Essential factors for the phosphate export is filtering of the water in stream-bed sediments through a distribution of hyporheic flow paths of various lengths. This generic study indicates that a significant portion of phosphate is retained in the hyporheic zones for a long time. The 90% recovery time following a hypothetical remediation action in the households is expected to be in the order of one decade.
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| 11. |
- Westin, Charles
(author)
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10. Populating the Baltic region
- 2002. - 1
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In: The Baltic Sea Region. - Uppsala : Baltic University Press. - 9197357987 ; , s. 145-151
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Book chapter (pop. science, debate, etc.)
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| 13. |
- Keller, T, et al.
(author)
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Impact of artificial snow and ski slope grooming on the snow pack properties and the soil thermal regime in a sub-alpine area
- 2004
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In: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 38, s. 314-318
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Journal article (peer-reviewed)abstract
- Studies have indicated that the soil on groomed ski slopes may be subjected to more pronounced cooling than the soil below a natural snowpack. We analyzed the thermal impacts of ski-slope preparation in a sub-alpine ski resort in central Switzerland (1100 in a.s.l.) where artificial snow was produced. Physical snow properties and soil temperature measurements were carried out on the ski slope and off-piste during winter 1999/2000. The numerical soil-vegetation-atmosphere transfer model COUP was run for both locations, with a new option to simulate the snowpack development on a groomed ski slope. Snow density. snow hardness and thermal conductivity were significantly higher on the ski slope than in the natural snowpack. However, these differences did rift affect the cooling of the soil, since no difference was observed between the ski slope and the natural snow cover. This might be because cold periods were rare and short and thus any snowpack could protect the soil from freezing. The major impact of the ski-slope grooming was a 4 week delay in snowmelt and soil warming at the end of the season. The newly implemented option proved to be a useful strategy for simulating the snowpack of a ski slope. However, snow density was underestimated by the model as it could not account adequately for compaction due to grooming traffic. Our study demonstrates that there is no site-independent answer as to whether a groomed snowpack affects the thermal conditions in the soil.
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| 16. |
- Sjöberg, Lars Erik, et al.
(author)
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Land uplift near Vatnajokull, Iceland, as observed by GPS in 1992, 1996 and 1999
- 2004
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In: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 159:3, s. 943-948
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Journal article (peer-reviewed)abstract
- Warming of the climate in the 20th century has been manifested by an ablation of Europe's largest ice cap, Vatnajokull in Iceland. The thin elastic lithosphere and the low-viscosity asthenosphere are responding to the reduction in mass by current land uplift in the vicinity of the ice cap suggested to be of the order of 5-10 mm yr(-1): lithosphere thickness and asthenosphere viscosities compatible with these values have been inferred. From our repeated GPS epoch campaigns in 1992, 1996 and 1999 uplift rates are estimated to be of the order of 5-19 mm yr(-1), and the uplift rate is decreasing by -0.11 +/- 0.01 mm yr(-1) km(-1) with radial distance from the centre of the ice cap. These results deviate from previous Earth rheology models estimated for the region. Our data indicate that the lithosphere thickness might be of the order of 10-20 km and the asthenosphere viscosity may be as low as 5 x 10(17) Pa s, but these parameters need a careful fitting to the estimated uplift rates.
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| 17. |
- Stähli, M., et al.
(author)
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A new in-situ sensor for large-scale snow cover monitoring
- 2004
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In: Annals of Glaciology. - : International Glaciological Society. - 0260-3055 .- 1727-5644. ; 38, s. 273-278
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Journal article (peer-reviewed)abstract
- A new in situ sensor for the simultaneous measurement of snow water equivalent, snow density and liquid-water content is presented in this paper. The system consists of radio frequency transmission lines of up to 25 in length cast in a flat PVC band, which can be set up either horizontally to monitor single snow-layer properties or sloping from a mast to the soil surface to determine vertical snowpack properties. The dielectric coefficient along the flat-band cable is measured with a time-domain reflectometer at high frequencies, and with a low-frequency impedance analyzer. The performance of the sensor system was tested during two winter seasons (2001-03) at the high-alpine test site Weissfluhjoch, Davos, Switzerland. The cable suspension and set-up of the sloping cable was shown to be critical with regard to stability and the formation of unwanted air gaps along the cable. Overall, the sensing system proved quite robust and produced results in agreement with manual snowpack observations.
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