Abstract
Abstract. Thus far, studies on climate change have focused mainly on the variability of the atmospheric and surface components of the hydrologic cycle, investigating the impact of this variability on the environment, especially with respect to the risks of desertification, droughts and floods. Conversely, the impacts of climate change on the recharge of aquifers and on the variability of groundwater flow have been less investigated, especially in Mediterranean karst areas whose water supply systems depend heavily upon groundwater exploitation. In this paper, long-term climatic variability and its influence on groundwater recharge were analysed by examining decadal patterns of precipitation, air temperature and spring discharges in the Campania region (southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, from 1921 to 2010, using 18 rain gauges and 9 air temperature stations with the most continuous functioning. The time series of the winter NAO index and of the discharges of 3 karst springs, selected from those feeding the major aqueducts systems, were collected for the same period. Regional normalised indexes of the precipitation, air temperature and karst spring discharges were calculated, and different methods were applied to analyse the related time series, including long-term trend analysis using smoothing numerical techniques, cross-correlation and Fourier analysis. The investigation of the normalised indexes highlighted the existence of long-term complex periodicities, from 2 to more than 30 yr, with differences in average values of up to approximately ±30% for precipitation and karst spring discharges, which were both strongly correlated with the winter NAO index. Although the effects of the North Atlantic Oscillation (NAO) had already been demonstrated in the long-term precipitation and streamflow patterns of different European countries and Mediterranean areas, the results of this study allow for the establishment of a link between a large-scale atmospheric cycle and the groundwater recharge of carbonate karst aquifers. Consequently, the winter NAO index could also be considered as a proxy to forecast the decadal variability of groundwater flow in Mediterranean karst areas.
Highlights
In the last few decades, the international scientific community has intensely debated climate change on a global scale (WMO, 1979) and the influence of anthropogenic activities
The time series of the winter NAOI, MAPI, MATI and MAEPI were first analysed with a least squares linear regression approach (Fig. 2)
In the Campania region, a complex cyclical periodicity of rainfall patterns that was mainly teleconnected with the North Atlantic Oscillation was discovered, confirming that previously observed for other regions of western Europe and North America (Hurrell and van Loon, 1997; VincenteSerrano and Trigo, 2011)
Summary
In the last few decades, the international scientific community has intensely debated climate change on a global scale (WMO, 1979) and the influence of anthropogenic activities. Int/pages/prog/wcp/wcdmp/index en.php) have been developed to analyse the state of knowledge on climate change, to start global monitoring of the climate systems and to fully understand the causes of its variability. Different groups of international experts (Intergovernmental Panel on Climate Change – IPCC) have been called to analyse the different causes and effects of these changes on the environment. P. De Vita et al.: Coupled decadal variability of the North Atlantic Oscillation evaluate different scenarios for the impact of greenhouse gas pollution on global climate
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