ALBERT

Description: The recent warming of the global climate is well recognized. However, does a warmer climate also mean a moister climate? Does dry get drier and wet get wetter? There are important questions as they relate to changes in the water cycle and impacts the water resources as well as the frequency and intensity of storms and floods in the near future. In Europe, regional climate models do not show consistent and robust results for future hydroclimatic changes and how extreme events will evolve in response to future climate change. Paleo-hydroclimatic data from natural archives are one of the few means to assess such changes in the longer context. Here, we present an annually-resolved record of warm season (MJJA) precipitation and summer flood frequency from the varved (annually laminated) sediments of proglacial Lake Oeschinen (46°30′N–7°44′E, 1580 m, NW Swiss Alps) back to AD 884. These data sets are inferred from the thickness of annual sediment deposits and the occurrence of flood event layers in the sediments. The chronology of the sediment record is based on multiple varve counts and validated with historical floods chronicled in written documents (back to the 14th century) and 14C AMS dates.

Description: Here, we present an annually-resolved record of summer flood frequency from the varved (annually laminated) sediments of proglacial Lake Oeschinen (46 30 N-7 44 E, 1580 m, NW Swiss Alps) back to AD 884. This dataset is produced based on the occurrence of flood event layers in the sediments. The chronology of the sediment record is based on multiple varve counts and validated with historical floods chronicled in written documents (back to the 14th century), 210Pb, 137Cs and 14C AMS dates. Our record of flood frequency suggests more frequent floods under cool and humid climate during the warm seasons. This picture is consistent with other studies from small and medium size catchments at mid- and high elevations in the Alpine area. However, the 13th century reveals a period with high flood frequency during warm and moderately dry (average precipitation) conditions. This anomalous situation is currently not understood; nonetheless, this is also one out of several possible scenarios for the future. From the different combinations found in our record, we conclude that the relation between floods, precipitation and temperature and, in consequence, future projections remain poorly constrained.

Description: Here, we present an annually-resolved record of warm season (MJJA) precipitation from the varved (annually laminated) sediments of proglacial Lake Oeschinen (46 30 N-7 44 E, 1580 m, NW Swiss Alps) back to AD 884. This data set is inferred from the thickness of annual sediment deposits in the sediments. The chronology of the sediment record is based on multiple varve counts and validated with historical floods chronicled in written documents (back to the 14th century), 201Pb, 137Cs, and 14C AMS dates. Our precipitation record is consistent with the few multi-centennial warm-season precipitation records available for Europe. We did not find a persistent relationship between warm-season precipitation and temperature. In contrast, results show that the relation between precipitation and temperature has oscillated between positive correlations (warmer gets wetter, cooler gets drier) and negative correlations (warmer gets drier, cooler gets wetter) with a highly significant (X2 = 99%) multidecadal (60-70 yrs) periodicity over the last millennium. Possible explanations for this phenomenon are changes in the weather type statistics or the within-weather-type variability, which influence the combinations between precipitation and temperature over continental central Europe and operate at multidecadal scales. Such multidecadal effects might also be important for precipitation scenarios in the Alpine area under future warming. From the different combinations found in our record, we conclude that the relation between floods, precipitation and temperature and, in consequence, future projections remain poorly constrained.

Description: We have measured leaf wax n-Alkanes from a Loess Paleosol Sequence (location: 47.56819 / 7.88053) ranging back to MIS 4. The data set contains n-Alkane patterns, Deuterium and Radiocarbon. We also present some calculations, derived from the Patterns: Average chain length gives a hint whether trees/shrubs or grasses were the dominant vegetation. The higher the value, the higher the contribution of grasses. ACL=(27 x nC_27+29 x nC_29+31 x nC_31+33 x nC_33)/(nC_27+nC_29+nC_31+nC_33 ) OEP is a marker for degradation. The higher the values, the less degraded are the n-alkanes. OEP=(nC_27+nC_29+nC_31+nC_33)/(nC_26+nC_28+nC_30+nC_32 ) For more information, further calculations and discussion see the related manuscript.

Description: Sediment phosphorus (P) released to surface water (a.k.a. internal P loading) is the key factor delaying lake recovery from eutrophication in many lakes. The sediment P availability and release risk into lake water can be largely evaluated by P fractions in sediments. In deep eutrophic lakes, hypolimnetic anoxia is suggested to prompt sediment-P mobility and potentially increase internal P loading on short term. However, the long-term effects hypolimnetic redox conditions and trophic state on sedimentary P-fraction retention in deep lakes are not clear. In this study we investigated two sediment cores retrieved from the deepest part of Lake Burgäschi, Switzerland. The age-depth profile based on 210Pb and 137Cs chronology dates back to the early 1900s. Sedimentary green-pigments (chlorophylls and diagenetic products) inferred from hyperspectral imaging (HSI) scanning and X-ray fluorescence (XRF)-inferred Fe/Mn ratios primarily reflect lake trophic state evolution (aquatic primary productivity) and hypolimnetic oxygenation, respectively. A sequential P-extraction with five P fractions was performed to uncover P fractionation in sediment profiles. In addition, we measured the sediment bulk elements of carbon, nitrogen and sulfur. The temporal records of P fractions concentrations and net burial rates (NBR) in sediments were investigated.