Two millennia of Main region (southern Germany) hydroclimate variability

Abstract

Abstract. A reconstruction of hydroclimate with an annual\nresolution covering millennia for a geographically limited region in\ncontinental Europe significantly improves our knowledge of past climate\ndynamics. With the use of an extensive collection of oak ring-width series\n(Quercus robur and Quercus petraea) from living trees, historic timbers and subfossil alluvial wood\ndeposits from the Main River region in southern Germany, a regional,\n2000-year long, seasonally resolved hydroclimate reconstruction for the\nMain region has been developed. Climate-growth response analysis has been\nperformed with daily climate records from AD\u20091900 onwards. To test the\nstability of the developed transfer function, a bootstrapped transfer\nfunction stability test (BTFS) as well as a classical calibration/verification approach have been implemented to study climate-growth model\nperformance. Living oak trees from the Main River region show a significant\nsensitivity to the precipitation sum from 26\xa0February to 6\xa0July (spring to\nmidsummer) during the full ( r=0.49 , p , N=116 ) and\nsplit ( r=0.58 , p , N=58 ) calibration periods. BTFS\nconfirmed the stability of the developed transfer function. The developed\nprecipitation reconstruction reveals high variability on a high- to\nmid-frequency scale during the past two\xa0millennia. Very dry spring to\nmidsummer seasons lasting multiple years appeared in the decades AD\u2009500/510s, 940s, 1170s, 1390s and 1160s. At the end of the AD\u2009330s, a\npersistent multi-year drought with drastically reduced rainfall (with regard to 1901–2000) could be identified, which was the driest decade over the past\n2000 years in this region. In the AD\u2009550s, 1050s, 1310s and 1480s,\nmulti-year periods with high rainfall hit the Main region. In spring to\nmidsummer of AD\u2009338, precipitation was reduced by ∼38 \u2009%\nand in AD\u2009357 it increased by ∼39 \u2009%. The presented\nhydroclimate reconstruction and its comparison to other records reveal\ninteresting insights into the hydroclimate dynamics of the geographically\nlimited area over the Common Era, in addition to revealing noticeable temporal\ndifferences.