Mittelalterliche Warmperiode

Ran et al. veröffentlichen in der Märzausgabe von Palaeogeography, Palaeoclimatology, Palaeoecology eine interessante Studie mit dem Titel Diatom-based reconstruction of palaeoceanographic changes on the North Icelandic shelf during the last millennium . Aus dem Abstract: Warm and stable conditions with relatively strong influence of the Irminger current on the North Icelandic shelf are indicated during the interval AD 940-1300, corresponding in time to the Medieval Warm Period (MWP).

Seit kurzem ist auf sciencedirect ein eingereichtes und akzeptiertes Manuskript von Martin-Chivelet et al., unter dem Titel Land surface temperature changes in Northern Iberia since 4000 yr BP, based on Delta13 C of speleothems als "Article in press" abrufbar. Aus dem Abstract: Main climatic recognized periods are: [...] (5) 1350-750 yr BP warm period (Medieval Warm Period) punctuated by two cooler events at ~ 1250 and ~ 850 yr BP;

This epoch appears to show most of the same characteristics as the post-glacial epoch both in the Northern Hemisphere and in the Antarctic, only in less degree, perhaps because of its shorter duration. The Arctic pack ice had melted so far back that appearences of drift ice in waters near Iceland and Greenland south of 70° N. were rare in the 800s and 900s and apparently unknown between 1020 and 1200, when a rapid increase of frequency began. This evidence hardly supports Brooks' suggeston that the Arctic Ocean again became ice-free during this epoch, though "permanent" ice was probably limited to inner Arctic areas north of 80° N. and possibly not including the Canadian Archipelago (to judge from occasional exploits there by the Old Norse Greenland colonist).[1] From the evidence of early Norse burials and plant roots in ground now permanently frozen in southern Greenland, annual mean temperatures there must have been 2°-4°C. above present values. It seems probable that ...

In der neuen Studie Drought duration and frequency in the U.S. Corn Belt during the last millennium (AD 992-2004) (Pdf-Format, ca. 890 KB), stellen sich die Autoren der nicht ganz unwichtigen Aufgabe, (to) "characterize the historic occurrence, duration, and frequency of drought events" (Stambaugh et al., 155). Aus dem Abstract: We used a new long tree-ring chronology developed from the central U.S. to reconstruct annual drought and characterize past drought duration, frequency, and cycles in the U.S. Corn Belt region during the last millennium. This is the first paleoclimate reconstruction achieved with subfossil oak wood in the U.S. and increases the current dendroclimatic record in the central U.S. agricultural region by over 500 years. A tree ring-width drought response function was calibrated and verified against monthly instrumental Palmer Hydrologic Drought Index (PHDI) during the summer season (JJA). Für uns von Interesse, das Mittelalter. Wir finden dazu in der ...

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, locate...