Miocene precipitation in Europe: Temporal trends and spatial gradients

It is known from present-day climates that both temporal and spatialvariations in precipitation can be more pronounced than those intemperature and thus influence ecosystems and human society in moresubstantial way. However, very little is known about such variations inthe past. Here we present an analysis of 206 palaeoprecipitation datafrom two twelve million year long proxy records of precipitation forSouthwest (Calatayud-Teruel basin) and Central Europe (Western andCentral Paratethys), spanning the late Early and Middle to Late Miocene(17.8-5.3 Ma) at a temporal resolution of about 80 kyr and 200 kyr,respectively. The estimates of precipitation are based on theecophysiological structure of herpetological assemblages. The resultsshow that precipitation variations in both regions have large amplitudesduring the Miocene with comparable temporal trends at longer timescales. With locally 300 mm up to more than 1000 mm more rainfall peryear than present, the early Langhian and the Tortonian were relativelywet periods, whereas the late Langhian and late Serravallian wererelatively dry, with up to 300 to 500 mm less precipitation thanpresent. The most humid time intervals were the early and middleTortonian washhouse climate periods. Overall, our data suggest that thelatitudinal precipitation gradient in Europe from the Middle to LateMiocene were highly variable, with a general tendency towards a reducedgradient relative to present day values. The gradient decreases duringcooling periods and increases during warming periods, similar to resultsfrom simulations of future climate change. Interestingly, theprecipitation gradient was reversed during the second washhouse climateperiod and the Early Messinian, which may have causes a negativehydrologic balance in the Eastern Paratethys during the latter time.Yet, our reconstructed gradient curve shows no direct correlation withthe global temperature signal from oxygen isotopes, which implies anon-linear regional response. Our results further suggest that majorfluctuations in the precipitation gradient can be responsible for shiftsin ecosystem distribution, and particularly, for faunal turnover inSouth Western Europe