2. Februar 2011

Was haben Guizhou/Südwest China und Montana/Nordwest USA gemeinsam?

Aus dem Abstract des "Article in press", Climate and environmental changes during the past millennium in central western Guizhou, China as recorded by Stalagmite ZJD-21 von Tz-Shing et al., erfahren wir Interessantes aus der Zhijin Cave in Zhijin County in Guizhou. So schreiben die Autoren:
The ZJD-21 Delta18O record suggests: (1) dry/warm climates during AD 950-1100 (overlapping with most of the Medieval Warm Period, MWP, in Europe); (2) strengthening of the summer monsoon from the MWP toward the beginning of the Little Ice Age (LIA) at AD 1250; (3) realtively wet/cold conditions occurred between AD 1250 and 1500, shown by relatively light Delta18O values;

Ebenfalls möchte ich hier die Studie, Geomorphic and climatic change over the past 12,900 yr at Swiftcurrent Lake, Glacier National Park, Montana, USA (Pdf-Format, 1,5 MB) von MacGregor et al. vorstellen. 

Die Autoren führen aus:
A sediment core, representing a 12,900-yr record collected from Swiftcurrent Lake, located on the eastern side of Glacier National Park, Montana, was analyzed to assess variability in Holocene and latest Pleistocene environment.
MacGregor et al., Abstract

Für uns von Interesse die Analyse der "Period V: 1,3 ka to present":
The most recent period in the Swiftcurrent Lake core ist characterized by generally high %TOC, low C/N ratios and fine-grained sediment (Fig. 7). Period V brackets well-defined climate events including the Medieval Warm Period (MWP) and the Little Ice Age (LIA), and changes in the %TOC record are well-correlated with documented timing of climate changes defining the MWP and LIA. For example, %TOC is relatively high and stable between 1.3 and 0.7 ka, corresponding closely with slightly increased GISP 2 temperatures.

MacGregor et al., 87