Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Other. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing an older version [v1]Go to new versionA climatic evaluation of the southern dispersal routeAuthorsSamuel LNicholsonRobHosfieldiDHuw SGroucuttiDAlistair W GPikeiDStephen JBurnsiDAlbertMatteriDDominikFleitmanniDSee all authors Samuel L NicholsonCorresponding Author• Submitting AuthorEcology and Evolutionary Biology, University of Reading, Reading, RG6 6LA, United KingdomDepartment of Archaeology, University of Reading, Reading, RG6 6AB, United Kingdomview email addressThe email was not providedcopy email addressRob HosfieldiDDepartment of Archaeology, University of Reading, Reading, RG6 6AB, United KingdomiDhttps://orcid.org/0000-0001-6357-2805view email addressThe email was not providedcopy email addressHuw S GroucuttiDExtreme Events Research Group, Max Planck Institute for Chemical Ecology, 07745 Jena, Jena, GermanyDepartment of Archaeology, Max Plank Institutes for Chemical Ecology, the Science of Human History, and Biogeochemsitry, 07745 Jena, GermanyInstitute of Prehistoric Archaeology, University of Cologne, Cologne, 5093, GermanyiDhttps://orcid.org/0000-0002-9111-1720view email addressThe email was not providedcopy email addressAlistair W G PikeiDDepartment of Archaeology, University of Southampton, Southampton, SO17 1BF, United KingdomiDhttps://orcid.org/0000-0002-5610-8948view email addressThe email was not providedcopy email addressStephen J BurnsiDDepartment of Geosciences, University of Massachusetts, MA 01003-9297, United States of AmericaiDhttps://orcid.org/0000-0003-4623-5326view email addressThe email was not providedcopy email addressAlbert MatteriDUniversity of BerniDhttps://orcid.org/0000-0001-8072-3185view email addressThe email was not providedcopy email addressDominik FleitmanniDDepartment of Archaeology, University of Reading, Reading, RG6 6AB, United KingdomDepartment of Environmental Sciences, University of Basel, CH-4056 Basel, SwitzerlandiDhttps://orcid.org/0000-0001-5977-8835view email addressThe email was not providedcopy email address
Abstract The oxygen isotopic composition of land-snail shells may provide insight into the source region and trajectory of precipitation. Last glacial maximum (LGM) gastropod shells were sampled from loess from Belgium to Serbia and modern land-snail shells both record δ 18 O values between 0‰ and − 5‰. There are significant differences in mean fossil shell δ 18 O between sites but not among genera at a single location. Therefore, we group δ 18 O values from different genera together to map the spatial distribution of δ 18 O in shell carbonate. Shell δ 18 O values reflect the spatial variation in the isotopic composition of precipitation and incorporate the snails' preferential sampling of precipitation during the warm season. Modern shell δ 18 O decreases in Europe along a N–S gradient from the North Sea inland toward the Alps. Modern observed data of isotopes in precipitation (GNIP) demonstrate a similar trend for low-altitude sites. LGM shell δ 18 O data show a different gradient with δ 18 O declining toward the ENE, implying a mid-Atlantic source due to increased sea ice and a possible southern displacement of the westerly jet stream. Balkan LGM samples show the influence of a Mediterranean source, with δ 18 O values decreasing northward.
The approach commonly used to assess the potential for climate reconstruction is to use linear regressions to compare the isotopic signal stored in archives to instrumental climatic data sets. A new method is proposed that combines statistical and mechanistic approaches to extract climatic information from δ 13 C records in organic matter. Both a spatial and a temporal gradient of 13 C discrimination in a moss species commonly found in temperate and tropical peat bogs are compared to meteorological records. The relevance of fossil and modem analogues to elucidate palaeoenvironment records are tested. It was found that the magnitude and, in some cases, the direction of the impact of temperature, humidity and CO 2 atmospheric concentration on 13C discrimination depend on the calibration set considered. The use of a mechanistic model is shown to help greatly in specifying the joint influence of the climatic variables.
Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Other. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing the latest version by default [v2]A climatic evaluation of the southern dispersal routeAuthorsSamuel LNicholsonRobHosfieldiDHuw SGroucuttiDAlistair W GPikeiDStephen JBurnsiDAlbertMatteriDDominikFleitmanniDSee all authors Samuel L NicholsonCorresponding Author• Submitting AuthorEcology and Evolutionary Biology, University of Reading, Reading, RG6 6LA, United KingdomDepartment of Archaeology, University of Reading, Reading, RG6 6AB, United Kingdomview email addressThe email was not providedcopy email addressRob HosfieldiDDepartment of Archaeology, University of Reading, Reading, RG6 6AB, United KingdomiDhttps://orcid.org/0000-0001-6357-2805view email addressThe email was not providedcopy email addressHuw S GroucuttiDExtreme Events Research Group, Max Planck Institute for Chemical Ecology, 07745 Jena, Jena, GermanyDepartment of Archaeology, Max Plank Institutes for Chemical Ecology, the Science of Human History, and Biogeochemsitry, 07745 Jena, GermanyInstitute of Prehistoric Archaeology, University of Cologne, Cologne, 5093, GermanyiDhttps://orcid.org/0000-0002-9111-1720view email addressThe email was not providedcopy email addressAlistair W G PikeiDDepartment of Archaeology, University of Southampton, Southampton, SO17 1BF, United KingdomiDhttps://orcid.org/0000-0002-5610-8948view email addressThe email was not providedcopy email addressStephen J BurnsiDDepartment of Geosciences, University of Massachusetts, MA 01003-9297, United States of AmericaiDhttps://orcid.org/0000-0003-4623-5326view email addressThe email was not providedcopy email addressAlbert MatteriDUniversity of BerniDhttps://orcid.org/0000-0001-8072-3185view email addressThe email was not providedcopy email addressDominik FleitmanniDDepartment of Archaeology, University of Reading, Reading, RG6 6AB, United KingdomDepartment of Environmental Sciences, University of Basel, CH-4056 Basel, SwitzerlandiDhttps://orcid.org/0000-0001-5977-8835view email addressThe email was not providedcopy email address
Abstract. The 4.2 kyr event is regarded as one of the largest and best documented abrupt climate disturbances of the Holocene. Drying across the Mediterranean and Middle East is well established and is linked to societal transitions in the Akkadian, Egyptian and Harappan civilizations. Yet the impacts of this regional drought are often extended to other regions and sometimes globally. In particular, the nature and spatial extent of the 4.2 kyr event in the tropics have not been established. Here, we present a new stalagmite stable isotope record from Anjohikely, northwest Madagascar. Growing between 5 and 2 kyr BP, stalagmite AK1 shows a hiatus between 4.32 and 3.83 kyr BP, replicating a hiatus in another stalagmite from nearby Anjohibe, and therefore indicating a significant drought around the time of the 4.2 kyr event. This result is the opposite to wet conditions at 8.2 kyr BP, suggesting fundamentally different forcing mechanisms. Elsewhere in the south-east African monsoon domain dry conditions are also recorded in sediment cores in Lake Malawi and Lake Masoko and the Taros Basin on Mauritius. However, at the peripheries of the monsoon domain, drying is not observed. At the northern (equatorial East Africa) and eastern (Rodrigues) peripheries, no notable event is record. At the southern periphery a wet event is recorded in stalagmites at Cold Air Cave and sediment cores at Lake Muzi and Mkhuze Delta. The spatial pattern is largely consistent with the modern rainfall anomaly pattern associated with weak Mozambique Channel Trough and a northerly austral summer Inter Tropical Convergence Zone position. Within age error, the observed peak climate anomalies are consistent with the 4.2 kyr event. However, outside Madagascar, regional hydrological change is consistently earlier than a 4.26 kyr BP event onset. Gradual hydrological change frequently begins at 4.6 kyr BP, raising doubt as to whether any coherent regional hydrological change is merely coincident with the 4.2 kyr event rather than part of a global climatic anomaly.