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Climate warming due to the enhanced greenhouse effect is expected to have a significant impact on the natural environment
and human activity in high latitudes. Because of its geography, wide coastal areas, water resources, forests, and wetlands,
the environment of Estonia is sensitive to climate change and sea level rise. Climate change scenarios for Estonia were generated
using a Model for the Assessment of Greenhouse-gas Induced Climate Change (MAGICC) and a regional climate change database,
Scenario Generator (SCENGEN). Three alternative emission scenarios were combined with data from 14 general circulation model
experiments. The assessment results of forest resources using RipFor, a forest-soil-atmosphere model, show that climate warming
would enhance forest growth in Estonia resulting in increased productivity (2–9%) of harvestable timber on highly productive
sites. Nutrient mobility increases greatly and in highly permeable soils with stable vegetation, increased mobility may result
in nutrient losses through leaching. The assessment results of water resources using the simple water balance model, WatBal,
show that the runoff regime of Estonian rivers would equilibrate and the groundwater table would rise. Climate warming would
not cause any particular problems with water supply but the groundwater quality may suffer from increased leaching. Due to
milder winters and increased storminess, the destruction of coastal areas, inundation of wetlands and disappearance of rare
plant communities in coastal areas would be the most damaging results of climate change. Most sandy beaches high in recreational
value would disappear. However, isostatic uplift and settlements inland from the present coastline reduce the risk of socio-economic
decline.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Mathematical Geosciences - 相似文献
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Abstract— The Lockne impact event took place in a Middle Ordovician (455 Ma) epicontinental sea. The impact resulted in an at least 13.5 km wide, concentric crater in the sea floor. Lockne is one of very few locations where parts of an ejecta layer have been preserved outside the crater structure. The ejecta from the Lockne impact rests on progressively higher stratigraphic levels with increasing distance from the crater, hence forming a slightly inclined discontinuity surface in the pre‐impact strata. We report on a ～30 cm thick sandy layer at Hallen, 45 km south of the crater centre. This layer has a fining upward sequence in its lower part, followed by low‐angle cross‐laminations indicating two opposite current directions. It is rich in quartz grains with planar deformation features and contains numerous, up to 15 cm large, granite clasts from the crystalline basement at the Lockne impact site. The layer is within a sequence dated to the Baltoniodus gerdae conodont subzone. The dating is corroborated by chitinozoans indicating the latest Kukruse time below and the late Idavere above the impact layer. According to the chitinozoans biostratigraphy, some erosion may have occurred because of deposition of the impact layer. The Hallen outcrop, today 45 km from the centre of the Lockne crater, is at present the most distant accessible occurrence of ejecta from the Lockne impact. It is also the most distant location so far found where the resurge of water towards the crater has affected the bottom sediments. A greater crater diameter than hitherto assumed, thus representing greater impact energy, might explain the extent of the ejecta blanket. Fluidisation of ejecta, to be expected at a marine‐target impact, might furthermore have facilitated the wide distribution of ejecta. 相似文献
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Investigations of multi-layer current regime, variations in sea level and wave parameters using a bottom-mounted RDCP (Recording Doppler Current Profiler) during 20 December 2006–23 May 2007 were integrated with surveys on changes of shorelines and contours of beach ridges at nearby Harilaid Peninsula (Saaremaa Island). A W-storm with a maximum average wind speed of 23 m s−1 occurred on 14–15 January with an accompanying sea level rise of at least 100 cm and a significant wave height of 3.2 m at the 14 m deep RDCP mooring site. It appeared that in practically tideless Estonian coastal waters, Doppler-based “vertical velocity” measurements reflect mainly site-dependent equilibrium between resuspension and sedimentation. The mooring site, 1.5 km off the Kelba Spit of Harilaid, was located in the accumulation zone, where downward fluxes dominated and fine sand settled. As a result of storms in January and April, the distal part of the accumulative gravel spit advanced by 50 m, whereas a 30–50 m retreat of the shoreline in the western and northern parts occurred at Cape Kiipsaare. The location of the beach ridges shows that the development of the spit occurs through relatively short-period but infrequent storm events, roughly 2–3 times each decade. 相似文献
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Changes in the activity and tracks of Arctic cyclones 总被引：1，自引：0，他引：1
Changes in the frequency and air pressure of cyclones that enter or are formed within the Arctic basin are herein examined by applying the database of cyclones created using NCEP/NCAR re-analysis. The Arctic basin is defined as the area north of latitude 68° N. Deep cyclones with a mean sea level pressure (SLP) of below 1,000 hPa, were analysed separately from shallow cyclones. Changes in the variables in the first, last, deepest and northernmost points of cyclones were studied. The cyclones were grouped into sectors by using the point on latitude 68° N at which the cyclone entered the Arctic region. The analysis described herein shows that the frequency of incoming cyclones, i.e. those that entered the Arctic basin, increased significantly during the period 1948?C2002, but that the frequency of Arctic cyclones formed within the Arctic basin did not. The frequency of deep cyclones that entered the Arctic basin, as well as the frequency of cyclones that formed within it, clearly increased, while the frequency of shallow Arctic cyclones decreased. The most significant changes in the seasonal parameters associated with the cyclones occurred in winter. The mean annual SLP of deep cyclones decreased significantly, particularly for deep Arctic cyclones. The frequency of incoming cyclones showed an increase in the Bering Strait, Alaskan, Baffin Sea, and East Siberian sectors. 相似文献
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