A "critical" climatic evaluation of last interglacial (MIS 5e) records from the Norwegian Sea

Sediment cores from the Norwegian Sea were studied to evaluate interglacial climate conditions of the marine isotope stage 5e (MIS 5e). Using planktic forminiferal assemblages as the core method, a detailed picture of the evolution of surface water conditions was derived. According to our age model, a step-like deglaciation of the Saalian ice sheets is noted between ca. 135 and 124.5 Kya, but the deglaciation shows little response with regard to surface ocean warming. From then on, the rapidly increasing abundance of subpolar forminifers, concomitant with decreasing iceberg indicators, provides evidence for the development of interglacial conditions sensu stricto (5e-ss), a period that lasted for about 9 Ky. As interpreted from the foraminiferal records, and supported by the other proxies, this interval of 5e-ss was in two parts: showing an early warm phase, but with a fresher, i.e., lower salinity, water mass, and a subsequent cooling phase that lasted until ca. 118.5 Kya. After this time, the climatic optimum with the most intense advection of Atlantic surface water masses occurred until ca. 116 Kya. A rapid transition with two notable climatic perturbations is observed subsequently during the glacial inception. Overall, the peak warmth of the last interglacial period occurred relatively late after deglaciation, and at no time did it reach the high warmth level of the early Holocene. This finding must be considered when using the last interglacial situation as an analogue model for enhanced meridional transfer of ocean heat to the Arctic, with the prospect of a future warmer climate

Marine Palaeoklimatologie: Rapiden Klimawechseln auf der Spur Schlussbericht 1990-1993

SIGLEAvailable from TIB Hannover: F95B2048 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Evaluation of full field automated photoelastic analysis based on phase stepping

A full field automated polariscope for photoelastic analysis has been developed in the author's laboratory and has been described in detail elsewhere. Briefly, the system uses phase-stepping to determine both the fractional isochromatic fringes and isoclinic parameter at all points in the field of view independently of their neighbouring points. A wrapping algorithm is then employed to produce continuous ischromatic and isoclinic data, which can be subsequently be used in stress separation procedures. The idea of using phase stepping in photoelasticity is a fairly recent innovation and can be described as changing incremently the absolute phase of the reference wave by rotating the output elements of the polariscope and measuring the local light intensity after each step. In the apparatus described here, the output elements are rotated to six different positions providing six images of the specimen. Maps of the periodic values of the isoclinic and isochromatic parameters are subsequently obtained by combining, mathematically, these six images. A number of full field techniques have been developed. Poloshin and Redner have developed half fringe photoelasticity, and two laboratories in Japan are working on the technique of phase stepping. It appears, however, that no detailed evaluation has been made of the accuracy and reliability of the results generated by the technique. The objective of the work described in this paper has been provided such an evaluation. Five different models were selected for analysis using the automated system and manually using the Tardy compensation method: (a) a disk in diametral compression: (b) a constrained beam subject to a point load: (c) a tensile plate with a central hole: (d) a turbine blade; and (e) a turbine disk slot. These models provided a range of different fringe patterns, orders and stress gradients to test the performance of the system

The application of evolutionary and maximum entropy algorithms to photoelastic spectral analysis

Over the past 10 years, spectral analysis has been shown to have the potential to be a reliable means of automating photoelasticity. However, the four methods of analyzing the spectra that have previously been proposed are slow and, in some cases, inaccurate. This paper describes three new methods for spectral analysis based on the maximum entropy method, a genetic algorithm and a memetic algorithm. Thirty-five spectra for known fringe orders were recorded and used in testing the four existing methods and the three new ones. It was found that the new methods were all considerably faster than the existing methods, although less accurate than the best existing method. By combining the maximum entropy method with either the genetic algorithm or the memetic algorithm, spectra could be analyzed up to 30 times as fast as they could with any of the existing methods and with comparable accuracy