scholarly journals Review on “Speleothem stable isotope reference records for East-Central Europe – Resampling sedimentary proxy records to get evenly spaced time-series with spectral control” by I. G. Hatvani et al.

2017 ◽  
Author(s):  
Laia Comas-Bru
2016 ◽  
Vol 8 (1) ◽  
Author(s):  
Asok K. Sen ◽  
Zoltán Kern

AbstractThis study investigates the low-frequency (interannual and longer period) variability in three hydroclimatic records from east Central Europe. Two of these records consist of climate proxies derived from oak-tree rings in Bakta forest, and Balaton Highlands in Hungary, for the time interval 1783-2003. The third record consists of homogenized instrumental precipitation data from Budapest, Hungary, from 1842 to 2003. Using wavelet analysis, the three time series are analyzed and compared with one another. It is found that all three time series exhibit strong interannual variability at the 2-4 years timescales, and these variations occur intermittently throughout the length of each record. Significant variability is also observed in all the records at decadal timescales, but these variations persist for only two to three cycles. Wavelet coherence among the various time series is used to explore their time-varying correlation. The results reveal significant coherence at the 2-4 years band. At these timescales, the climatic variations are correlated to the tree-ring signal over different time intervals with changing phase. Increased (decreased) contribution of large-scale stratiform precipitation offers a potential explanation for enhanced (faded) coherence at the interannual timescale. Strong coherence was also observed occasionally at decadal timescales, however these coherences did not appear uniformly. These results reinforce the earlier assertion that neither the strength nor the rank of the similarity of the local hydroclimate signals is stable throughout the past two centuries.


2020 ◽  
Vol 16 (6) ◽  
pp. 2445-2458
Author(s):  
Carmen-Andreea Bădăluţă ◽  
Aurel Perșoiu ◽  
Monica Ionita ◽  
Natalia Piotrowska

Abstract. The climate of east-central Europe (ECE) is the result of a combination of influences originating in the wider North Atlantic realm, the Mediterranean Sea, and the western Asian and Siberian regions. Previous studies have shown that the complex interplay between the large-scale atmospheric patterns across the region results in strongly dissimilar summer and winter conditions on timescales ranging from decades to millennia. To put these into a wider context, long-term climate reconstructions are required, but, largely due to historical reasons, these are lacking in ECE. We address these issues by presenting a high-resolution, radiocarbon-dated record of summer temperature variations during the last millennium in ECE, based on stable isotope analysis of a 4.84 m long ice core extracted from Focul Viu Ice Cave (Western Carpathians, Romania). Comparisons with both instrumental and proxy-based data indicate that the stable isotope composition of cave ice records the changes in summer air temperature and has a similar temporal evolution to that of the Atlantic Multidecadal Oscillation on decadal to multidecadal timescales, suggesting that changes in the North Atlantic are transferred, likely via atmospheric processes towards the wider Northern Hemisphere. On centennial timescales, the data show little summer temperature differences between the Medieval Warm Period (MWP) and the Little Ice Age (LIA) in eastern Europe. These findings are contrary to those that show a marked contrast between the two periods in terms of both winter and annual air temperatures, suggesting that cooling during the LIA was primarily the result of wintertime climatic changes.


2017 ◽  
Author(s):  
István Gábor Hatvani ◽  
Zoltán Kern ◽  
Szabolcs Leél-Őssy ◽  
Attila Demény

Abstract. Uneven spacing is a common feature of sedimentary paleoclimate records, in many cases causing difficulties in the application of classical statistical and time series methods. Although special statistical tools do exist to assess unevenly spaced data directly, the transformation of such data to a temporarily equidistant time series applicable to commonly used statistical tools remains, however, an unachieved goal. The present paper, therefore, introduces an approach to obtain evenly spaced time series (using cubic spline fitting) from unevenly spaced speleothem records with the application of a spectral control to avoid spectral bias caused by interpolation and retain the original spectral characteristics of the data. The methodology was applied to stable carbon and oxygen isotope records derived from two stalagmites of the Baradla Cave (NE Hungary) dating back to the late 18th century; it was also applied to additional well-dated and high-resolution stable isotope records from the Han-sur-Lesse Cave (Belgium). To show the benefit of these equally spaced records to climate studies, their coherence with primary and complex climate indices is explored using wavelet transform coherence and discussed. The results shed light on clear relationships with climate and NAO indices, lending support to the approach utilized in this study. Moreover, these suggest that the Baradla composite stable isotope data can serve as regional reference records for the past ~200 years. The equally spaced time series obtained, are available at: https://doi.org/10.1594/PANGAEA.875917.


Author(s):  
Jacek Wieclawski

This article discusses the problems of the sub-regional cooperation in East-Central Europe. It formulates the general conclusions and examines the specific case of the Visegrad Group as the most advanced example of this cooperation. The article identifies the integrating and disintegrating tendencies that have so far accompanied the sub-regional dialogue in East-Central Europe. Yet it claims that the disintegrating impulses prevail over the integrating impulses. EastCentral Europe remains diversified and it has not developed a single platform of the sub-regional dialogue. The common experience of the communist period gives way to the growing difference of the sub-regional interests and the ability of the East-Central European members to coordinate their positions in the European Union is limited. The Visegrad Group is no exception in this regard despite its rich agenda of social and cultural contacts. The Russian-Ukrainian conflict confirms a deep divergence of interests among the Visegrad states that seems more important for the future of the Visegrad cooperation than the recent attempts to mark the Visegrad unity in the European refugee crisis. Finally, the Ukrainian crisis and the strengthening of the NATO’s “Eastern flank” may contribute to some new ideas of the sub-regional cooperation in East-Central Europe, to include the Polish-Baltic rapprochement or the closer dialogue between Poland and Romania. Full text available at: https://doi.org/10.22215/rera.v10i1.251  


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