Swiss tree rings reveal warm and wet summers during medieval times

We present a 1200 year drought reconstruction for the European Alpine region based on carbon isotope variations of tree rings from living larch trees and historic timber. The carbon isotope fractionation at the study site is sensitive to summer precipitation, temperature, and irradiance, resulting in a stable and high correlation with a drought index for interannual to decadal frequencies and possibly beyond (r(2)=0.58 for 1901-2004, July/August). When combining this information with maximum latewood density-derived summer temperature, a strongly reduced occurrence of summer droughts during the warm A.D. 900-1200 period is evident, coinciding with the Medieval Climate Anomaly (MCA), with a shift to colder and drier conditions for the subsequent centuries. The warm-wet MCA contrasts strongly with the climate of the drought-prone warm phase of the recent decades, indicating different forcing mechanism for these two warm periods and pointing to beneficial conditions for agriculture and human well-being during the MCA in this region.

Evidence for cooler European summers during periods of changing meltwater flux to the North Atlantic

We analyzed fossil chironomids (nonbiting midges) and pollen in two lake-sediment records to reconstruct and quantify Holocene summer-temperature fluctuations in the European Alps. Chironomid and pollen records indicate five centennial-scale cooling episodes during the early- and mid-Holocene. The strongest temperature declines of ≈1°C are inferred at ≈10,700–10,500 and 8,200–7,600 calibrated 14C years B.P., whereas other temperature fluctuations are of smaller amplitude. Two forcing mechanisms have been presented recently to explain centennial-scale climate variability in Europe during the early- and mid-Holocene, both involving changes in Atlantic thermohaline circulation. In the first mechanism, changes in meltwater flux from the North American continent to the North Atlantic are responsible for changes in the Atlantic thermohaline circulation, thereby affecting circum-Atlantic climate. In the second mechanism, solar variability is the cause of Holocene climatic fluctuations, possibly triggering changes in Atlantic thermohaline overturning. Within their dating uncertainty, the two major cooling periods in the European Alps are coeval with substantial changes in the routing of North American freshwater runoff to the North Atlantic, whereas quantitatively, our climatic reconstructions show a poor agreement with available records of past solar activity. Thus, our results suggest that, during the early- and mid-Holocene, freshwater-induced Atlantic circulation changes had stronger influence on Alpine summer temperatures than solar variability and that Holocene thermohaline circulation reductions have led to summer-temperature declines of up to 1°C in central Europe.

Grabfigur Mrs. Andrew D. White [Illustration]

Moses Jakob Ezekiel

Andrew Black, Kniestück

Signatur des Originals: S 36/F08218

Andrew Radde-Gallwitz, Basil of Caesarea, Gregory of Nyssa, and the Transformation of Divine Simplicity, Oxford University Press, Oxford, 2009; 261 pp. ISBN 978-0-19-957411-7.

Fil: Peretó Rivas, Rubén.

Theodore de Mopsuestia, The Commentaries of the Minor Epistle of Paul, Translated with an Introduction by Rowan A. Greer (SBL Writings from the Greco-Roman World, 26). Atlanta GA, Society of Biblical Literature, 2010. ISBN 978-1-58983-279-4, XLIV-839 p.

Fil: Peretó Rivas, Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas

Identification and Stereospecificity of the First Three Enzymes of 3-Dimethylsulfoniopropionate Biosynthesis in a Chlorophyte Alga1

Many marine algae produce 3-dimethylsulfoniopropionate (DMSP), a potent osmoprotective compound whose degradation product dimethylsulfide plays a central role in the biogeochemical S cycle. Algae are known to synthesize DMSP via the four-step pathway, l-Met → 4-methylthio-2-oxobutyrate → 4-methylthio-2-hydroxybutyrate → 4-dimethylsulfonio-2-hydroxy-butyrate (DMSHB) → DMSP. Substrate-specific enzymes catalyzing the first three steps in this pathway were detected and partially characterized in cell-free extracts of the chlorophyte alga Enteromorpha intestinalis. The first is a 2-oxoglutarate-dependent aminotransferase, the second an NADPH-linked reductase, and the third an S-adenosylmethionine-dependent methyltransferase. Sensitive radiometric assays were developed for these enzymes, and used to show that their activities are high enough to account for the estimated in vivo flux from Met to DMSP. The activities of these enzymes in other DMSP-rich chlorophyte algae were at least as high as those in E. intestinalis, but were ≥20-fold lower in algae without DMSP. The reductase and methyltransferase were specific for the d-enantiomer of 4-methylthio-2-hydroxybutyrate in vitro, and both the methyltransferase step and the step(s) converting DMSHB to DMSP were shown to prefer d-enantiomers in vivo. The intermediate DMSHB was shown to act as an osmoprotectant, which indicates that the first three steps of the DMSP synthesis pathway may be sufficient to confer osmotolerance.

Will of the Rev. Andrew Croswell, 1785 November

This folder contains three handwritten copies of the November 8, 1785, will of Andrew Croswell and a copy of the inventory of Croswell's estate.

Copy of Andrew Croswell's executor's account, 1788 June 2

One-leaf account of the disbursements of the estate of Andrew Croswell presented to the judge of probate for Suffolk County, Massachusetts.

Letter from William Croswell to Andrew Croswell, 1828 June 20

Draft of a letter to Croswell's nephew regarding the family's history.

Letters from Daniel White to Andrew Hall, March 23, 1799

These two letters, both written on the same document, appear to be White's response to accusations from the father of one of his students at the Medford grammar school. Andrew Hall appears to have accused White of punishing his son too severely. In the letters, White denies Hall's accusations while defending his apparently strict approach to discipline. It is not certain whether both these letters were intended for Hall, or if one was written to another (unnamed) upset parent.