| 1. |
- Adler, Ruth E., et al.
(författare)
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Sediment record from the western Arctic Ocean with an improved Late Quaternary age resolution : HOTRAX core HLY0503-8JPC, Mendeleev Ridge
- 2009
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 68:02-jan, s. 18-29
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Tidskriftsartikel (refereegranskat)abstract
- Sediment core HLY0503-8JPC raised by the HOTRAX'05 expedition from the Mendeleev Ridge was analyzed for multiple lithological, paleontological. and stable-isotopic proxies to reconstruct paleoceanographic conditions in the western Arctic Ocean during the Late Quaternary. The core, extensively sampled in the upper 5 m, reveals pronounced changes in sedimentary environments during the ca. 250 kyr interval encompassing Marine Isotopic Stages (MIS) 1 to 7. An estimated average resolution of 500 yr/sample, at least for the last glacial cycle including the last interglacial, provides more detail than seen in other sedimentary records from the western Arctic Ocean. The age control is provided by C-14 and amino acid racemization measurements on planktonic foraminifers and correlations with the stratigraphy developed for the central Lomonosov Ridge and with glacial events at the Eurasian Arctic margin. Cyclic variations in lithology combined with foraminiferal abundance and stable-isotopic composition indicate profound changes in hydrographic and depositional environments between interglacial-type and glacial-type periods apparently reflecting a combination of 100-kyr and precessional time scales. This periodicity is complicated by abrupt iceberg- and/or meltwater-discharge events with variable (Laurentide vs. Eurasian) provenance. The proxy record from the interval identified as the last interglacial (MIS 5e), which may aid in understanding the future state of the Arctic Ocean, indicates low ice conditions and possibly enhanced stratification of the water column.
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| 2. |
- Bonow, Johan M., et al.
(författare)
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Palaeosurfaces in central West Greenland as reference for identification of tectonic movements and estimations of glacial erosion
- 2006
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 50:3-4, s. 161-183
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Tidskriftsartikel (refereegranskat)abstract
- Landform analysis of basement rocks has been undertaken with the aid of digital elevation data, aerial photographs and field observations in central West Greenland (69°15′N–66°00′N). Palaeosurfaces have been identified, dated relatively to each other, used to quantify uplift and fault movements and also used to estimate differential erosion. Two types of palaeosurfaces were mapped across the Precambrian basement: a surface at low elevation with distinct hills (hilly relief), and two planation surfaces formed across different types of basement rocks. The hilly relief surface emerges as an inclined surface from Cretaceous cover rocks in Disko Bugt and is interpreted as a stripped late Mesozoic etch surface. This surface is cut off towards the south by a less inclined planation surface, which is younger and thus of Cenozoic age. It is similar to the post-Eocene (Miocene?) planation surfaces identified on Disko and Nuussuaq in other studies. The planation surface splits in two southwards towards high areas around Nordre Isortoq and Sukkertoppen Ice Cap. The upper planation surface forms near-summit areas of tectonic blocks dipping in different directions and with different tilts. The uplift centres define the crests of two mega blocks, separated by the ‘Sisimiut Line’ which coincides with the Precambrian Ikertôq thrust zone. A partially developed lower planation surface indicates a first uplift of maximum 500 m followed by a second uplift of maximum 1000 m. We infer that these uplift events occurred during the late Neogene based on correlation with similar surfaces on Nuussuaq and the timing of exhumational events estimated from apatite fission track analyses of samples from a deep borehole on Nuussuaq (reported elsewhere). The difference between a reconstruction of the upper planation surface across the entire area and the present topography was used as an estimate of erosion of basement rock since the formation of the upper planation surface. The erosion is unevenly distributed and varies from almost none on the well-preserved planation surfaces to 800–1300 m along valleys, and even more in the fjords. Erosion is less within areas of gneiss in granulite facies, than in areas of gneiss in amphibolite facies.
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| 3. |
- Brogaard, Sara, et al.
(författare)
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Primary production of Inner Mongolia, China, between 1982 and 1999 estimated by a satellite data-driven light use efficiency model
- 2005
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 45:4, s. 313-332
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Tidskriftsartikel (refereegranskat)abstract
- Declining biological production as a part of an ongoing land degradation process is considered a severe environmental problem in the dry northern and northwestern regions of China. The aim of this study is to develop and adapt a satellite data-driven gross primary production model called Lund University light use efficiency model (LULUE) to temperate conditions in order to map gross primary production (GPP) for the Grasslands of Inner Mongolia Autonomous Region (IMAR), China, from 1982 to 1999. The water stress factor included in the original model has been complemented with two temperature stress factors. In addition, algorithms that allocate the proportions of C3/C4 photosynthetic pathways used by plants and that compute temperature-based C3 maximum efficiency values have been incorporated in the model. The applied light use efficiency (LUE) model is using time series of the Normalized Difference Vegetation Index (NDVI), CLouds from AVHRR (CLAVR) from the 8-km resolution NOAA Pathfinder Land Data Set (PAL). Quasi-daily rainfall and monthly minimum and maximum temperatures, together with soil texture information, are used to compute water limitations to plant growth. The model treats bare soil evaporation and actual transpiration separately, a refinement that is more biophysically realistic, and leads to enhanced precision in our water stress term, especially across vegetation gradients. Based on ground measurements of net primary production (NPP) at one site, the LULUE reproduces the variability of primary production better than CENTURY or NDVI alone. Mean annual GPP between 1982 and 1999 range from about 100 g/m(2) in desert regions in the west to about 4000 g/m(2) in the northeast of IMAR, and the coefficient of variation for GPP is highest near the margins of the deserts in the west where rainfall is erratic. Linear trends fitted through the 18-year time series reveal that the western regions have encountered no change, while a large area in the center of the IMAR shows marked increases in GPP. In the northeast, negative trends in GPP are noted and coincide with rainfall trends. Though the high inter-annual variability in primary production undermines the identification of significant trends, we could not isolate any general decline in grassland primary production.
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| 4. |
- Colleoni, Florence, 1983-, et al.
(författare)
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Influence of regional factors on the surface mass balance of the large Eurasian ice sheet during the peak Saalian (140 kyrs BP)
- 2009
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 68:1-2, s. 132-148
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Tidskriftsartikel (refereegranskat)abstract
- Recent geologically-based reconstructions of the Eurasian ice sheet show that during the peak Saalian (≈ 140 kya) the ice sheet was larger over Eurasia than during the Last Glacial Maximum (LGM) at ≈ 21 kya. To address this problem we use the LMDZ4 atmospheric general circulation model to evaluate the impact on the Saalian ice sheet's surface mass balance (SMB) from proglacial lakes, dust deposition on snow, vegetation and sea surface temperatures (SST) since geological records suggest that these environmental parameters were different during the two glacial periods. Seven model simulations have been carried out. Dust deposition decreases the mean SMB by intensifying surface melt during summer while proglacial lakes cool the summer climate and reduce surface melt on the ice sheet. A simulation including both proglacial lakes and dust shows that the presence of the former parameter reduces the impact of the latter, in particular, during summer. A switch from needle-leaf to tundra vegetation affects the regional climate but not enough to significantly influence the SMB of the nearby ice margin. However, a steady-state vegetation in equilibrium with the climate should be computed to improve the boundary conditions for further evaluations of the vegetation impact on the ice sheet's SMB. Finally, changes of the SST broadly affect the regional climate with significant consequences for the SMB.
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| 5. |
- Darby, Dennis, et al.
(författare)
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The 2005 HOTRAX Expedition to the Arctic Ocean
- 2009
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 68:1-2, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- The Healy–Oden Trans-Arctic Expedition (HOTRAX'05) recovered 29 long piston cores and associated multicores along a transect from the Alaskan margin across the central Arctic Ocean to the northern Svalbard margin. The initial results focus on the age and stratigraphy of these cores using a variety of approaches including radiocarbon, paleomagnetic and other chronostratigraphic methods as well as detailed correlations of proxy records. High sedimentation cores from probable drift deposits are described from the shelf and continental slope north of Alaska. Provenance and sedimentary processes in these deposits include both currents and sea-ice rafting. Much lower sedimentation rates in the central Arctic Ocean show geographic variability consistent with the patterns of expected sediment distribution by ice and, to a smaller extent, subsurface currents. Insights into the Upper Quaternary stratigraphy and depositional history are provided in two papers on a core from the Mendeleev Ridge with sedimentation rates relatively elevated for this region. To compliment the results from the HOTRAX cores, two papers are included dealing with the stratigraphy and sedimentary processes on the Chukchi shelf and a modeling study addressing why the Marine Isotopic Stage 6 (ca. 140 ka) glaciation was substantially more extensive in the Arctic than the Last Glacial Maximum.
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| 6. |
- Darby, Dennis, et al.
(författare)
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The role of currents and sea ice in both slowly deposited central Arctic and rapidly deposited Chukchi-Alaskan margin sediments
- 2009
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 68:1-2, s. 58-72
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Tidskriftsartikel (refereegranskat)abstract
- A study of three long cores from the outer shelf and continental slope north of Alaska in the Arctic Ocean indicate that localized drift deposits occur here with sedimentation rates of more than 1.5 m/kyr during the Holocene. Currents in this area average about 5–20 cm/s but can reach 100 cm/s and these velocities transport the sediment found in these cores primarily as intermittent suspended load. These high accumulation sediments form levee-like deposits associated with margins of canyons cutting across the shelf and slope. Unlike most textural investigations of Arctic sediment that focus on the coarser ice-rafted detritus (IRD), this paper focuses on the > 95% of the sediment, which is finer than 45 μm. The mean size of this fraction varies between 6 and 15 μm in Holocene sediments from the Chukchi–Alaskan shelf and slope with the higher values closer to shore. Analysis of detailed size distributions of these Holocene deposits are compared to 34 sediment samples collected from sea ice across the Arctic Ocean and to Holocene sediment from central Arctic Ocean cores and indicate that similar textural parameters occur in all of these sediments. Principal components of these size distributions indicate that sea ice is an important link between the shelves and the central Arctic. Factor scores indicate nearly identical components in the clay and fine silt size fractions but very different components in the coarse silt for sea ice sediment and central Arctic ridge sediments compared to shelf and continental slope deposits. Sea ice must contribute to sedimentation in both of these Arctic regions, but bottom currents dominate in the slope region, forming drift deposits.
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| 7. |
- De Angelis, Hernán, et al.
(författare)
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Snow zonation on Hielo Patagónico Sur, Southern Patagonia, derived from Landsat 5 TM data
- 2007
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181. ; 59, s. 149-158
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Tidskriftsartikel (refereegranskat)abstract
- Hielo Patagónico Sur (HPS), an icefield in Southern Patagonia, is the largest temperate ice mass in the southern hemisphere. Despite continued research efforts during the last decade many glaciological variables, especially mass balance, are still poorly known. This is partly because access to the icefield is difficult due to remoteness and persistent harsh weather conditions. Therefore, remote sensing appears to be a more suitable tool for the acquisition of data. In this work we present a remote sensing study of snow zonation on HPS using Landsat 5 Thematic Mapper data acquired on 12March 2001. By using image processing and classification techniques, proved to be useful in other glaciated regions, we map for the first time the extent and occurrence of major snow zones on the whole HPS. We separate between two classes of ice and three classes of snow. Ice facies are classified as bare or debris (i.e. dirt) covered ice, covering 2454 km2 and 777 km2 respectively, or 18.4% and 5.8% of the icefield on the day of image acquisition. Snow types are classifiedaccording to spectral differences in the images, following the glacier facies concept. Two of the three snow cover types are interpreted to represent differences in snow grain size within a fairly homogeneous snowpack whereas the third one is interpreted to represent the slush zone. A first order altitudinal control on the distribution of these snow facies is evident. In addition, our results show that snow accumulation on HPS is markedly controlled by the interaction of strong west–northwest snow-bearing winds and the roughmountainous terrain. In order of decreasing altitude we find that the two snow facies and the slush facies occupy 3819 km2, 3292km2 and2295 km2 respectively, or 28.6%, 24.6%and 17.2%of the icefield, on the day of image acquisition. Estimates of equilibrium line altitude using our results yield values of 800–900 m above sea level for the western side and 1500–1600 m above sea level for the eastern side, with an accumulation area ratio of 0.74.
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| 8. |
- Helldén, Ulf
(författare)
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A coupled human-environment model for desertification simulation and impact studies
- 2008
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 64:3-4, s. 158-168
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the development of a system dynamic model to simulate and analyze desertification. The human-environment coupled model integrates socio-economic drivers with bio-physical drivers of biomass production, land degradation and desertification. It is based on the UN and GEF definitions of desertification. It illustrates the concept of desertification through differential equation and simulation output graphics. It is supplemented with a causal loop diagram demonstrating the existing feed-back mechanisms. The model relates population pressure and dynamics over time to the growth and availability of biomass resources. The human population stock is described as a function of growth rate, death rate and resources dependent in and out migration of people. The relative growth rate of the stock of resources is modeled as a function of climate and exploitation pressure affecting soil erosion and water availability. The model is applied for the Sahelian desertification syndrome using input data to illustrate and simulate a 150 years period (1900-2050) in Kordofan, Sudan. The model indicates that it is difficult to generate irreversible desertification. (C) 2008 Elsevier B.V. All rights reserved.
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| 9. |
- Helldén, Ulf, et al.
(författare)
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Regional desertification: A global synthesis
- 2008
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 64:3-4, s. 169-176
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents results on the use of NOAA AVHRR data for desertification monitoring on a regional-global level. It is based on processing of the GIMMS 8 km global NDVI data set. Time series of annually integrated and standardized annual NDVI anomalies were generated and compared with a corresponding rainfall data set (1981-2003). The regions studied include the Mediterranean basin, the Sahel from the Atlantic to the Red Sea, major parts of the drylands of Southern Africa, China-Mongolia and the drylands of South America, i.e. important parts of the desertification prone drylands of the world. It is concluded that the suggested methodology is a robust and reliable way to assess and monitor vegetation trends and related desertification on a regional-global scale. A strong general relationship between NDVI and rainfall over time is demonstrated for considerable parts of the drylands. The results of performed trend analysis cannot be used to verify any systematic generic land degradation/desertification trend at the regional-global level. On the contrary. a "greening-up" seems to be evident over large regions. (C) 2008 Elsevier B.V. All rights reserved.
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| 10. |
- Jakobsson, Martin, et al.
(författare)
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Reconstructing the Younger Dryas ice dammed lake in the Baltic Basin: Bathymetry, area and volume
- 2007
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 57:3-4, s. 355-370
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Tidskriftsartikel (refereegranskat)abstract
- A digital 3D-reconstruction of the Baltic Ice Lake's (BIL) configuration during the termination of the Younger Dryas cold phase (ca. 11700 cal. yr BP) was compiled using a combined bathymetric-topographic Digital Terrain Model (DTM), Scandinavian ice sheet limits, Baltic Sea Holocene bottom sediment thickness information, and a paleoshoreline database maintained at the Lund University. The bathymetric-topographic DTM, assembled from publicly available data sets, has a resolution of 500 X 500 m on Lambert Azimuthal Equal Area projection allowing area and volume calculations of the BIL to be made with an unprecedented accuracy. When the damming Scandinavian ice sheet margin eventually retreated north of Mount Billingen, the high point in terrain of Southern central Sweden bordering to lower terrain further to the north, the BIL was catastrophically drained resulting in a 25 m drop of the lake level. With our digital reconstruction, we estimate that approximately 7800 km(3) of water drained during this event and that the ice dammed lake area was reduced by ca. 18%. Building on previous results suggesting drainage over 1 to 2 years, our lake volume calculations imply that the freshwater flux to the contemporaneous sea in the west was between about 0.12 and 0.25 Sv. The BIL reconstruction provides new detailed information on the paleogeography in the area of southern Scandinavia, both before and after the drainage event, with implications for interpretations of geological records concerning the post-glacial environmental development. (c) 2007 Elsevier B.V All rights reserved.
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| 11. |
- Jessen, Catherine, et al.
(författare)
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Climate forced atmospheric CO2 variability in the early Holocene: A stomatal frequency reconstruction
- 2007
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 57:3-4, s. 247-260
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic climate in the Northern Hemisphere during the early Holocene could be expected to have impacted on the global carbon cycle. Ice core studies however, show little variability in atmospheric CO2. Resolving any possible centennial to decadal CO2 changes is limited by gas diffusion through the firn layer during bubble enclosure. Here we apply the inverse relationship between stomatal index (measured on sub-fossil leaves) and atmospheric CO2 to complement ice core records between 11,230 and 10,330 cal. yr BP. High-resolution sampling and radiocarbon dating of lake sediments from the Faroe Islands reconstruct a distinct CO2 decrease centred on ca. 11,050 cal. yr BP, a consistent and steady decline between ca. 10,900 and 10,600 cal. yr BP and an increased instability after ca. 10,550 cal. yr BP. The earliest decline lasting ca. 150 yr is probably associated with the Preboreal Oscillation, an abrupt climatic cooling affecting much of the Northern Hemisphere a few hundred years after the end of the Younger Dryas. In the absence of known global climatic instability, the decline to ca. 10,600 cal. yr BP is possibly due to expanding vegetation in the Northern Hemisphere. The increasing instability in CO2 after 10,600 cal. yr BP occurs during a period of increasing cooling of surface waters in the North Atlantic and some increased variability in proxy climate indicators in the region. The reconstructed CO2 changes also show a distinct similarity to indicators of changing solar activity. This may suggest that at least the Northern Hemisphere was particularly sensitive to changes in solar activity during this time and that atmospheric CO2 concentrations fluctuated via rapid responses in climate. (c) 2006 Elsevier B.V. All rights reserved.
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| 12. |
- Nilsson, Carin, et al.
(författare)
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Relating forest damage data to the wind field from high-resolution RCM simulations: Case study of Anatol striking Sweden in December 1999
- 2007
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 57:1-2, s. 161-176
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Tidskriftsartikel (refereegranskat)abstract
- Forestry is of major economical importance in Europe, and recent devastating windstorms have pinpointed the vulnerability of this economic sector to windstorms. Forest damage is an important economic issue at a country level and may become even of larger concern under future conditions following global warming. An underlying question is to what extent the storm damage is due to changes in the wind climate compared to the effect of changes in forest management practices? In this paper, the first part of this rather complex problem is tackled. By using the Canadian Regional Climate Model, CRCM, including a physically based gust parameterisation scheme, NCEPNCAR reanalysis wind fields for the windstorm Anatol, on December 3-4, 1999, were downscaled, into a nested set-up, to 2 km resolution. The aim is to relate the simulated storm wind field to the observed distribution of storm damaged forests in Scania in southern Sweden, as a first methodological step towards analysing the effect of future windstorms in Swedish forests at the highest spatial resolution one can afford nowadays. Our results show that the CRCM produced realistic wind field simulations, compared to station observations, of the windstorm event in 1999. The simulated winds were underestimated at the coasts, but in congruence with inland observations. Most of the damaged forest stands were located on south-westerly (SW) slopes, which indicated a south-westerly wind during the wind throw process. This SW wind direction was evident in the early phase of the simulated storm, but then changed into a westerly flow, at an earlier stage than the true observations specified. Further, most damage occurred in the areas of simulated maximum wind speed greater than 30 m s. To conclude, the CRCM has proven to be a useful tool to realistically simulate a forest damaging storm event. Hence, the model could be used for further study cases, preferably driven by a GCM, in order to reveal a greater understanding about recent storms, which in turn helps us evaluate future climate change driven storm conditions. (c) 2006 Elsevier B.V All rights reserved.
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| 13. |
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| 14. |
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| 15. |
- Rundgren, Mats, et al.
(författare)
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Last interglacial atmospheric CO2 changes from stomatal index data and their relation to climate variations
- 2005
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 49:1-2, s. 47-62
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Tidskriftsartikel (refereegranskat)abstract
- A high-resolution atmospheric CO2 reconstruction based on stomatal index data obtained from Betula and Quercus leaf fragments extracted from the Danish Hollerup lake sediment section provides a unique insight into last interglacial CO2 dynamics. According to pollen stratigraphic correlations the CO2 record covers the first c. 7400 years of the Eemian, as palaeobotanically defined in northwestern Europe. The first c. 3000 years of the reconstruction are characterised by centennial to millennial CO2 variability in the interval 250-290 ppmv, while the remaining part of the record is generally more stable with slightly higher values (290-300 ppmv). According to pollen stratigraphic correlations this shift in CO2 dynamics is coincident with the end of the early Eemian climatic optimum in northwestern Europe. Pollen data from this region indicate that early Eemian CO2 instability may be linked to vegetation succession following deglaciation in Europe, but vegetation dynamics on other northern continents were probably also important. In addition, palaeoceanographic records from the Nordic seas indicate an influence of oceanic processes on the reconstructed Eemian CO2 evolution. A 300-year period of rapid CO2 oscillations immediately before the establishment of stable conditions is synchronous with a dry and cool event previously inferred from proxy data from the same sediment sequence, suggesting that this was a climatic event of regional or global significance. The presented CO2 reconstruction is in general agreement with previous ice core and stomatal-based CO2 data, although a larger variability compared with Vostok ice core data is evident. This may be explained partly by the different resolution of the two records and the inherent smoothing of ice core gas records.
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| 16. |
- Sellén, Emma, et al.
(författare)
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Pleistocene variations of beryllium isotopes in central Arctic Ocean sediment cores
- 2009
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 68:1-2, s. 38-47
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Tidskriftsartikel (refereegranskat)abstract
- Neogene marine sediments can be dated via decay of the cosmogenic radionuclide 10Be. Two cores from theAlpha and Mendeleev Ridges in the Arctic Ocean have been analyzed for seawater-derived beryllium (Be)isotopes in order to date the sediments and to calculate sedimentation rates. The decrease of 10Be concentrationin the cores was used to calculate first order sedimentation rates. To eliminate the dilution effect of berylliumcaused by short-term changes in sedimentation rate and grain size, the 10Be concentrationswere normalized tothe terrigenous stable isotope 9Be determined in the same sample aliquot. The measured 10Be concentrationsyield low average sedimentation rates for the Alpha and Mendeleev Ridges of 2.3 mm ka−1 and 2.7 mm ka−1,respectively. Sedimentation rates calculated from the 10Be/9Be ratios result in similarly low values, rangingfrom 0.2 to 6.8 mm ka−1 for the Alpha Ridge core and from 1.9 to 6.9 mm ka−1 for the Mendeleev Ridge core.However, amino acid racemization dating for the past 150 ka of a core adjacent to the Mendeleev Ridge corestudied here indicates significantly higher sedimentation rates than calculated from the downcore decreaseof 10Be and 10Be/9Be. If such higher rates also prevailed at the locations of our cores, for which there isbiostratigraphic evidence, either the supply of 10Be was much lower than assumed or that of 9Be was muchhigher. This could imply that the signature of the deepwaters in this part of the Arctic Ocean compared to todaywas largely different for most of the past approximately one million years with a significantly lower 10Be/9Beratio. Our study also addresses the variability of beryllium isotopes in sediment cores across the Arctic Oceanthrough a comparison of previously published results. Calculated 10Be fluxes reveal low values in the AmerasianBasin and highest values in the Eurasian Basin, near the Fram Strait. The decrease of Be isotopes in the twostudied Amerasian Basin cores may thus have been caused by environmental factors such as significantlyreduced inflow of Atlantic waters in the past, reduced input of 10Be and/or increased input of 9Be from theshelves, combined with a more efficient sea ice shielding in this part of the Arctic Ocean.
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| 17. |
- Sellén, Emma, et al.
(författare)
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Sedimentary regimes in Arctic’s Amerasian and Eurasian basins : Clues to differences in sedimentation rates
- 2008
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 61:3-4, s. 275-284
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Tidskriftsartikel (refereegranskat)abstract
- A standard lithostratigraphic model based on cores retrieved 1963–1973 from the ice island T-3 was developed by Clark et al. (1980) for the Amerasian Basin of the Arctic Ocean. We have investigated whether or not it is possible to apply this lithostratigraphy to cores from the Lomonosov Ridge, which can be correlated to Eurasian Basin cores, for the purpose of correlating the Amerasian and Eurasian stratigraphies. Published averaged sedimentary proxies from a selected set of T-3 cores are used to correlate with the identical published proxies for the included Lomonosov Ridge cores. The standard lithostratigraphic classification could not be applied to the Lomonosov Ridge cores, which is interpreted to result from differences in sedimentary regimes in the Amerasian and Eurasian Basins. These differences also apply to the barrier between the two basins, the Lomonosov Ridge. The general sedimentation rates are three to four times lower in the Amerasian Basin than in the Eurasian Basin if the first down-core paleomagnetic inclination change is used to correlate between the two basins whereas correlation based on sediment coarse fraction suggests only two times lower rates in the Amerasian Basin.
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