Gravity change and land uplift in Fennoscandia 1966–1984

An analysis is made of the results from all repeated gravity measurements of the Fennoscandian land uplift gravity line 63°. The line is, thereby, divided into two separate parts: one part west of the land uplift maximum, and the other part east of the land uplift maximum. A statistically significant change of gravity is found both for the western part and the eastern one. Both parts give a relation between gravity change and land uplift of about ?0.22μgal/mm.     

Some possibilities of predicting radio wave absorption in the lower ionosphere

Summary An attempt is made to show possible ways of predicting radio wave absorption in the midlatitude lower ionosphere using relations between absorption and the intensity of solar ionizing radiation and/or common solar activity indices, and between absorption and f₀F2.

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aa mu nuau nu a¶rt;u ¶rt;um u u a mu ¶rt; nu u umum uuu uu (uu uu u¶rt;au amumu) u ¶rt; nu u f₀F2.

     

Hydrostatic-system palsas at Toolik lake,Alaska: Field observations and simulation

Stratigraphic and chemical data from the ice core of an ‘anthropogenic palsa’ at Toolik Lake, Alaska, indicate that the mound formed as a consequence of hydrostatic pressure developed in an isolated hydrologic system within the active layer. Survey data for five palsas over a three-year period suggest that growth was essentially complete at the time of the initial survey; a net decrease of summit elevation is apparent in all five mounds, but complete degradation of the palsas would require several decades at observed rates. Because accurate field measurements of thermal and hydrologic evolution in such features are extremely difficult, simulation of the environmental conditions and events involved in palsa growth is an important supplement to field observation. Both analytic and finite-element models yield results that are in substantial agreement with inferences drawn from observational data.     

The two-step shape and timing of the last deglaciation in Antarctica

The two-step character of the last deglaciation is well recognized in Western Europe, in Greenland and in the North Atlantic. For example, in Greenland, a gradual temperature decrease started at the Bölling (B) around 14.5 ky BP, spanned through the Alleröd (A) and was followed by the cold Younger Dryas (YD) event which terminated abruptly around 11.5 ky BP. Recent results suggest that this BA/YD sequence may have extended throughout all the Northern Hemisphere but the evidence of a late transition cooling is still poor for the Southern Hemisphere. Here we present a detailed isotopic record analyzed in a new ice core drilled at Dome B in East Antarctica that fully demonstrates the existence of an Antarctic cold reversal (ACR). These results suggest that the two-step shape of the last deglaciation has a worldwide character but they also point to noticeable interhemispheric differences. Thus, the coldest part of the ACR, which shows a temperature drop about three times weaker than that recorded during the YD in Greenland, may have preceded the YD. Antarctica did not experienced abrupt changes and the two warming periods started there before they started in Greenland. The links between Southern and Northern Hemisphere climates throughout this period are discussed in the light of additional information derived from the Antarctic dust record.     

Development and propagation of precipitation cores on cold fronts

The structure and propagation of precipitation cores on a variety of cold fronts are described. The shapes of the cores, and their orientations with respect to the synoptic-scale front, are not always uniform either between fronts or within the same front. Interactions between cores depend on their proximity and relative strength. Large gaps between precipitation cores move along the cold front at a slower speed than the cores and affect the evolution of the precipitation cores. The spacing of precipitation cores, the height of the head of the density current associated with the cold front, and the strength of the cold front are positively correlated with precipitation strength. This suggests that interactions between cores are strongly influenced by precipitation.Current theories for precipitation cores on narrow cold-frontal rainbands cannot account for these observations. A new mechanism is proposed based on a positive feedback between the diabatic cooling produced by the melting and evaporation of precipitation, the head of the density current, and the strength of the front.     

High resolution time series of lead and zinc in sediments of Lake Constance

Sediments in Lake Constance have been dated by radiometric methods and lamination counting. Investigations into the concentrations of lead and zinc in the sediments were carried out to get detailed information about environmental history. Maximum concentrations were found at the beginning of the 1960's. The lead maximum contamination occurred 3 years before the zinc maximum and has an unidentified source. The use of coal, leaded gasoline or the remobilization within the sediment could be excluded to result in the lead maximum. The fluctuations in zinc contamination could be explained with increasing and decreasing pollution (industry, coal burning, building of sewage plants). The greatest fluctuations of both metals occur during periods of great change in the economic history of Germany.     

Influence of the IMF sector boundaries on cosmic rays and tropospheric vorticity

Summary The effect of the IMF sector boundary crossing (IMF SBC) in the vorticity area index (VAI) — the well-known dip in the VAI after IMF SBC — is found to be independent of the IMF SBC effect in the cosmic ray flux. This finding refutes a recent suggestion by Lundstedt [1] that the IMF SBC effect in VAI is caused by a decrease in cosmic ray flux, but supports the concept of the IMF SBC effects in the ionosphere and atmosphere developed by Latovika [2–4]. Cosmic rays seem to affect the troposphere in another way.

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¶rt;mu nu mau nam aum n ( ) a u¶rt; na¶rt;u aumu () — um uu n — a¶rt; auu m ma nm uu . mm mam nam ¶rt;a n¶rt;u ¶rt;m¶rt;a [1], m m a nuu nma uu , n¶rt;¶rt;uam nu m u u am, aum amu [2–4]. am m uu u m um a mn ¶rt;u a.

     

Deep structure of the lithosphere beneath the territory of Bulgaria

Summary Teleseismic P residuals calculated for waves arriving from various azimuths and angles of incidence, and a 3-D inversion of the residuals provided the basis for characterizing the uppermost mantle structure beneath Bulgaria. The Moesian Platform and the Rhodopean Massif are two different blocks characterized by a lithosphere thickness of about 130–140 km with a zone of lithosphere thinning along their contact. Both units have opposite patterns of the directional dependence of relatively high and low P velocities. This directional dependence is interpreted by dipping anisotropic structures in the subcrustal lithosphere, which probably represent remnants of paleosubductions of an old oceanic lithosphere.

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auma u nu¶rt;u n¶rt; au aumau u au. a uu mu ¶rt;am ¶rt; aamuauu mm amuu n¶rt; au. uua nama u ¶rt;nu au, ¶rt;a au a mu um nuuum 130–140 ¶rt; uma m ¶rt; u mama. a a aamua nmun ana auum mum u u mu . ma anaa auum umnmuaa a nu aumn mm amu. mu mm n¶rt;maum a mamu na¶rt;u ma au um.