Jörg F W Negendank

Evidence from Lake Lisan of solar influence on decadal- to centennial-scale climate variability during marine oxygen isotope stage 2

Documentation of short-term climate variability during the glacial period has been limited by the availability of well-dated high-resolution archives. Here we present a paleoclimate reconstruction from varved lacustrine sediments of Lake Lisan, Dead Sea Rift, for ca. 26.2–17.7 (calendar) ka. The age is based on a floating varve chronology anchored to radiometric dates. Our reconstruction indicates that small ice-rafting events (a, b, c, and d), as well as Heinrich events in the North Atlantic, are associated with the Eastern Mediterranean arid intervals. Study of seasonal sublaminae yields evidence of several additional decadal- to century-scale arid events that correlate with cooler temperatures at higher latitudes. Analyses in the frequency domain indicate the presence of periodicities centered at 1500 yr, 500 yr, 192 yr, 139 yr, 90 yr, and 50–60 yr, suggesting a solar forcing on climate.

Mid- to Late Holocene Lake Ecosystem Response to Catchment and Climatic Changes — A Detailed Varve Analysis of Lake Holzmaar (Germany)

A varved sediment record of Lake Holzmaar, Germany spanning ca. 4120 years (mid- to late Holocene) was investigated with the aim to reconstruct environmental and indirectly climate change Summer (‘light’) and winter (‘dark’) laminae were identified according to their predominantly autochthonous and allochthonous structure, respectively. Algal sublayers within the light laminae were subject to marked changes in thickness and in algal species composition. Diatoms were the dominant algal class throughout the record. However, chrysophytes played a substantial role in varve formation between ca. 5300 and 3660 cal yr BP. Autecological characteristics of the dominant algal species and algal succession allowed to infer shifts of the prevailing water circulation type and relative changes in nutrient concentration and ratios (phosphorus and silica). Based on the combination of all results, the palaeolimnological development was reconstructed and split into three distinct lake periods (6340–5300 cal yr BP; 5300–3660 cal yr BP; 3660–2220 cal yr BP). The palaeolimnological characteristics in turn allowed to make suggestions upon the palaeoclimatological development in consideration of relevant studies from other sites in Western Europe. With the beginning of the Iron Age (ca. 2660 cal yr BP), climatic interpretation remains unclear though, because anthropogenic activity sharply increased.

Klimawandel und Wasserhaushalt

Die kostengunstige Deckung des Wasserbedarfs der Nutzer bei gleichzeitiger Erhaltung der Okosystemfunktionen von Gewassern stellt eine stetig zu erfullende Aufgabe der Wasserwirtschaft dar. Eine nachhaltige Bewirtschaftung hoch beanspruchter Wasserressourcen-Systeme ist dabei nur mOglich, wenn fortlaufend solche Methoden und Verfahren evaluiert und weiterentwickelt werden, die Veranderungen und Anpassungen des Wasserwirtschaftssystems erlauben. Es gilt, Wasserdargebot und Wasserbedarf durch dargebotsund/ oder bedarfsorientierte Einflussnahmen unter minimalen Kosten bzw. bei maximaler Nachhaltigkeit in ubereinstimmung zu bringen (Grunewald 2008a; Abb. 2-1).

Evidence for the Climate During the Late Maunder Minimum from Proxy Data and Model Simulations Available Within KIHZ

The knowledge constructed within the project “Klima in historischen Zeiten” (KIHZ) about the Late Maunder Minimum (LMM), based upon corals, lake and marine sediment records, ice cores and speleothems, is reviewed. The data are compared to a simulation with the climate model ECHO-G. It is found that the LMM was an event of global scale, with a cooling on the entire Northern hemisphere and in the tropics, while a weaker warming may have taken place on the Southern Hemisphere. The model results are mostly consistent with the empirical evidence. However, the empirical data are not very conclusive so that any claims that the dynamics behind the simulated LMM would equal the dynamics of the real event should be considered with care.

Climate Change at the End of the Third Millennium BC — Evidence from Varved Lacustrine Sediments

The sedimentary record of Lake Holzmaar provides an absolute varve chronology confirmed by AMS-14C data. Before 2500 BC and after 1800 BC depositional processes were controlled by both human and palaeoclimatic influences. Between the end of the Neolithic and the onset of the Bronze Age no anthropogenic interference with the environment is suggested by the archaeological data. An increase in dry density and magnetic susceptibility during the period 2500 to 1800 BC (in sideral years) is therefore, attributed to palaeoclimatic causes. These sediment changes are interpreted to be the result of increased runoff related to an increase of precipitation and/or colder temperatures which is in agreement with other proxy records from northern and central Europe, indicating cold and wet conditions at this time.

The Contribution of High-resolution Magnetostratigraphic Analyses to Paleoclimatic Reconstructions

Paleoclimatic studies based on sedimentary sequences can be supported by the analysis of the sediment’s magnetism. Determination of the magnetization directions, and partly, the intensity can provide useful information for dating when the results can be correlated to dated master curves. So, one main task of a magnetostratigraphic study is to provide an age model for the sediments investigated for paleoclimatic reconstructions. In addition, analysis of the magnetic carrier minerals themselves give additional information about paleoenvironmental processes, since often the input and preservation or alteration of the magnetic particles reflect climatic influences on the sediments bulk composition. Magnetostratigraphy therefore can be one of the most important stratigraphic tools in paleoclimate research.

Phase Stability of the Solar Schwabe Cycle in Lake Holzmaar, Germany, and GISP2, Greenland, between 10,000 and 9,000 cal. BP

Changes of solar activity — e.g. the solar Schwabe cycle — are frequently documented in those archives comprising the output of biological systems The signal transfer from the solar input signal to the biological output signal is supposed to be nonlinear with an output maximum for optimal conditions of the system. Under the assumption of long-term phase stability of the solar Schwabe cycle, phase analysis should enable the detection of phase jumps when optimal conditions are crossed during the secular development of the biological system. The current study compares two archives (sediment accumulation rate of Lake Holzmaar and MSA accumulation rate in the Greenland ice core of GISP2) which are controlled by biological systems and influenced by the changes of climate in the surroundings of the Northern Atlantic. The same pattern of phase jumps of the solar Schwabe cycle is found in both archives and might permit high precision cross-dating of the archives.