Showing papers by "Manfred Mudelsee published in 2012"
TL;DR: In this paper, the authors presented high-resolution stable isotope and lamina thickness profiles as well as radiocarbon data for the Holocene stalagmite ER 76 from Grotta di Ernesto (north-eastern Italy).
Abstract: Here we present high-resolution stable isotope and lamina thickness profiles as well as radiocarbon data for the Holocene stalagmite ER 76 from Grotta di Ernesto (north-eastern Italy), which was dated by combined U-series dating and lamina counting. ER 76 grew between 8 ka (thousands of years before 2000 AD) and today, with a hiatus from 2.6 to 0.4 ka. Data from nine meteorological stations in Trentino show a significant influence of the North Atlantic Oscillation (NAO) on winter temperature and precipitation in the cave region. Spectral analysis of the stable isotope signals of ER 76 reveals significant peaks at periods of 110, 60–70, 40–50, 32–37 and around 25 a. Except for the cycle between 32 and 37 a all periodicities have corresponding peaks in power spectra of solar variability, and the 25-a cycle may correspond to NAO variability. This suggests that climate variability in northern Italy was influenced by both solar activity and the NAO during the Holocene. Six periods of warm winter climate in the cave region were identified. These are centred at 7.9, 7.4, 6.5, 5.5, 4.9 and 3.7 ka, and their duration ranges from 100 to 400 a. The two oldest warm phases coincide with the deposition of sapropel S1 in the Mediterranean Sea indicating that the climate in the cave region was influenced by this prominent pluvial phase in the Mediterranean area. For the younger warm phases it is difficult to establish a supra-regional climate pattern, and some of them may, thus, reflect regional climate variability. This highlights the complexity of regional and supra-regional scale Holocene climate patterns.
95 citations
TL;DR: In this article, the authors present a new record of past winter climate variability for the last 10.8 ka based on four speleothems from Bunker Cave, Western Germany, which is particularly well suited to record changes in precipitation and temperature in response to changes in the North Atlantic realm.
Abstract: Holocene climate was characterised by variability on multi-centennial to multi-decadal time scales. In central Europe, these fluctuations were most pronounced during winter. Here we present a new record of past winter climate variability for the last 10.8 ka based on four speleothems from Bunker Cave, Western Germany. Due to its central European location, the cave site is particularly well suited to record changes in precipitation and temperature in response to changes in the North Atlantic realm. We present high resolution records of δ18O, δ13C values and Mg/Ca ratios. We attribute changes in the Mg/Ca ratio to variations in the meteoric precipitation. The stable C isotope composition of the speleothems most likely reflects changes in vegetation and precipitation and variations in the δ18O signal are interpreted as variations in meteoric precipitation and temperature. We found cold and dry periods between 9 and 7 ka, 6.5 and 5.5 ka, 4 and 3 ka as well as between 0.7 to 0.2 ka. The proxy signals in our stalagmites compare well with other isotope records and, thus, seem representative for central European Holocene climate variability. The prominent 8.2 ka event and the Little Ice Age cold events are both recorded in the Bunker cave record. However, these events show a contrasting relationship between climate and δ18O, which is explained by different causes underlying the two climate anomalies. Whereas the Little Ice Age is attributed to a pronounced negative phase of the North Atlantic Oscillation, the 8.2 ka event was triggered by cooler conditions in the North Atlantic due to a slowdown of the Thermohaline Circulation.
89 citations
TL;DR: In this paper, the authors examined three stalagmite time series of oxygen isotopic composition (18 O) from two caves in western Germany, the series AH-1 from the Atta Cave and the series Bu1 and Bu4 from the Bunker Cave.
Abstract: A fundamental problem in paleoclimatology is to take fully into account the various error sources when ex- amining proxy records with quantitative methods of statisti- cal time series analysis. Records from dated climate archives such as speleothems add extra uncertainty from the age de- termination to the other sources that consist in measurement and proxy errors. This paper examines three stalagmite time series of oxygen isotopic composition ( 18 O) from two caves in western Germany, the series AH-1 from the Atta Cave and the series Bu1 and Bu4 from the Bunker Cave. These records carry regional information about past changes in win- ter precipitation and temperature. U/Th and radiocarbon dat- ing reveals that they cover the later part of the Holocene, the past 8.6 thousand years (ka). We analyse centennial- to millennial-scale climate trends by means of nonparametric Gasser-M¨ uller kernel regression. Error bands around fitted trend curves are determined by combining (1) block boot- strap resampling to preserve noise properties (shape, auto- correlation) of the 18 O residuals and (2) timescale simula- tions (models StalAge and iscam). The timescale error in- fluences on centennial- to millennial-scale trend estimation are not excessively large. We find a "mid-Holocene climate double-swing", from warm to cold to warm winter condi- tions (6.5 ka to 6.0 ka to 5.1 ka), with warm-cold amplitudes of around 0.5 ‰ 18 O; this finding is documented by all three records with high confidence. We also quantify the Medieval Warm Period (MWP), the Little Ice Age (LIA) and the cur- rent warmth. Our analyses cannot unequivocally support the conclusion that current regional winter climate is warmer than that during the MWP.
19 citations
TL;DR: In this paper, the authors reconstruct a proxy record of April and November-December temperatures in south-central Finland for the interval from 1836 to 1872 from breakup and freeze-up dates and ice-cover duration of a lake.
Abstract: One obstacle on the way to a comprehensive spatial reconstruction of regional temperature changes over the past centuries is the sparseness of long winter temperature records. This paper reconstructs a proxy record of April and November–December temperatures in south-central Finland for the interval from 1836 to 1872 from breakup and freeze-up dates and ice-cover duration of a lake. Emphasis is on detecting the suitable winter months and quantifying the calibrations with measured temperatures (1873–2002). The calibration slope for the breakup date (0.158°C/day) is larger than for freeze-up date (0.119°C/day) or duration (0.090°C/day). A comparison with results from other proxy records shows that the slope may depend also on the geographical site. Trend analyses of the full temperature records (1836–2002) indicate the existence of minor change-points at around 1867 (April temperature) and 1874 (November–December temperature), with warming rates thereafter of 1.67°C per century (April) and 1.16°C per century (November–December). Spectral analyses reveal peaks in the band between 2 and 5 year period, which may point to influences of the North Atlantic Oscillation, and less power in the decadal band (up to 42 year period).
10 citations
Posted Content•
TL;DR: In this article, a technique of time series analysis, called potential forecasting, which is based on dynamical propagation of the probability density of the time series, is introduced, and applied to forecast Arctic sea-ice time series.
Abstract: We introduce a technique of time series analysis, potential forecasting, which is based on dynamical propagation of the probability density of time series. We employ polynomial coefficients of the orthogonal approximation of the empirical probability distribution and extrapolate them in order to forecast the future probability distribution of data. The method is tested on artificial data, used for hindcasting observed climate data, and then applied to forecast Arctic sea-ice time series. The proposed methodology completes a framework for `potential analysis' of climatic tipping points which altogether serves anticipating, detecting and forecasting climate transitions and bifurcations using several independent techniques of time series analysis.
1 citations
TL;DR: An elegant mathematical generalization of autoregressive models (the nine types) is given and state-of-the-art model fitting techniques (genetic algorithm combined with fitness function and least squares) are explained.
Abstract: The paper by Battaglia and Protopapas (Stat Method Appl 2012) is stimulating. It gives an elegant mathematical generalization of autoregressive models (the nine types). It explains state-of-the-art model fitting techniques (genetic algorithm combined with fitness function and least squares). It is written in a fluent and authoritative manner. Important for having a wider impact: it is accessible to non-statisticians. Finally, it has interesting results on the temperature evolution over the instrumental period (roughly the past 200 years). These merits make this paper an important contribution to applied statistics as well as climatology. As a climate researcher, coming from Physics and having had an affiliation with a statistical institute only as postdoc, I re-analyse here three data series with the aim of providing motivation for model selection and interpreting the results from the climatological perspective.