Quantification of the impact of moisture source regions on the oxygen isotope composition of precipitation over Eagle Cave, central Spain

The 5-day reconstruction of air mass history for the days with precipitation at Eagle Cave (central Spain), together with the determination of moisture uptake locations along back trajectories, is used to identify the moisture sources of precipitation for this site from 2009 to 2011. During this 3-year period, around 30% of precipitation at Eagle Cave originated from the moisture recycled within the Iberian Peninsula (IP), with the Proximal Atlantic being also a main source region of moisture, whereas the Mediterranean Sea and the Distal Atlantic have large variability during the studied period and other source regions are minor precipitation contributors. The comparison of monthly oxygen isotope composition of precipitation at Eagle Cave with the monthly percentage of precipitation originated in source regions shows a significant negative correlation for the IP region. Thus, the moisture recycling process in the IP region explains 12% of the variability of the monthly oxygen isotope composition of precipitation (p-value < 0.1). However, when temperature, amount of precipitation and all source regions are considered, 74% of the variability of the monthly oxygen isotope composition of precipitation is explained (p-value < 0.05). Therefore, although for Eagle Cave amount of precipitation and temperature are main contributors of the precipitation oxygen isotope variability (r(2) = 0.54; p-value < 0.001), the moisture uptake distribution among source regions is a substantial control and should be considered when interpreting oxygen isotope speleothem records from this cave. This research highlights the importance of moisture sources in controlling the oxygen isotope composition of precipitation in mid-latitudes, and the need of quantification of this effect in order to improve the interpretation of oxygen isotope paleo-records that depend on isotope composition of precipitation. (C) 2014 Elsevier Ltd. All rights reserved.