Sub-decadal scale coupling of the Moroccan Sidi Ali lake core record with historical and meteorological data for the last 120 years

Abstract

<p>The Western Mediterranean region including the North African desert margin faces major environmental challenges in the backdrop of global climate change in terms of rising temperatures, a higher recurrence of drought events and a decrease in annual precipitation. As a condition to state further prospects, it is crucial to comprehend past and present hydro-climatic patterns. The Moroccan Middle Atlas is considered a transition zone between Atlantic, Mediterranean and Saharan air masses and is therefore of unprecedented interest in order to comprehend regional climate variability and to assess emerging hydrological, geomorphological and ecological impacts. Despite the growing number of limnological studies from the Middle Atlas, there still is a strong need for coupling palaeolimnological results at the sub-recent time scale with historical cartographic information, meteorological variables and underlying climatic forcing. Lake Sidi Ali (33°03’ N, 5°00’ W, 2080 m a.s.l.) provides a unique archive for understanding environmental changes throughout the 20<sup>th</sup> century. At least for the past 100 years the lake has experienced a minimum of three significant lake level changes in the order of several meters. We were able to reconstruct and quantify these alternations with the help of historical sources, topographic maps and satellite imagery. In addition, we implemented a multi-proxy analytical approach on a 145-cm long sediment record, including δ<sup>18</sup>O and δ<sup>13</sup>C isotope analysis of ostracod shells and CNS elemental analysis. A reliable age model based on 25 <sup>210</sup>Pb measurements and one radiocarbon dated cedar needle enables the linkage of sediment geochemical variations to lake level changes based on an instrumental record and historic topographic maps. We use meteorological precipitation and temperature data to evaluate the main drivers controlling these fluctuations. Furthermore, we have indications for a temporal coupling of Atlantic climate patterns (North Atlantic Oscillation, NAO; Atlantic Multidecadal Oscillation, AMO) with Sidi Ali lake level development.</p>