A review of selected, well-dated, multiproxy paleoclimatic records (lacustrine, dendrochronological, geomorphological) characterizes the main environmental changes occurred in the Southern Pyrenees during the last millennium. Warmer and relatively arid conditions prevailed during the Medieval Climate Anomaly (MCA, <1300 AD), with a significant development of xerophytes and Mediterranean vegetation and limited deciduous tree formations (mesophytes). The Little Ice Age (LIA, 1300–1800 AD) was generally colder and moister, with an expansion of deciduous taxa and cold-adapted mountainous conifers. Two major phases occurred within this period: (i) a transition MCA-LIA, characterized by fluctuating, moist conditions and relatively cold temperatures (ca. 1300 and 1600 AD); – (ii) a second period, characterized by coldest conditions and higher humidity, coinciding with maximum (recent) glacier advances (ca. 1600–1850 AD). After the LIA a warming and more arid phase started coinciding with glacier retreat, and interrupted by a short-living cooling episode during the late 19th to early 20th centuries. Some records suggest a response to solar activity with colder and slightly moister conditions during solar minima. Centennial-scale hydrological fluctuations are in phase with reconstructions of NAO variability, which appears to be the main forcing for humidity in the region during the last millennium

En este trabajo se presenta el reto que muchas veces supone conseguir un buen modelo de edad independiente en una secuencia paleoambiental. Esta aproximación pasa por la necesidad de combinar diferentes metodologías de datación, con la complejidad que esto implica. Se han seleccionado dos ejemplos de dos archivos paleoambientales muy distintos, y con cronologías muy diferentes. El registro de El Cañizar de Villarquemado, un paleolago en la provincia de Teruel, que alberga en sus sedimentos los últimos 135.000 años de historia y constituye la secuencia continental más larga y continua estudiada en la mitad septentrional de Iberia. Para poder establecer un modelo de edad robusto e independiente fue necesario combinar dataciones de radiocarbono AMS, U-Th, OSL, IRSL, paleomagnetismo y criptotefro-cronología, aunque no todas las técnicas resultaron exitosas. El segundo ejemplo se centra en el reto de datar el hielo presente en el icónico glaciar de Monte Perdido, situado en el Pirineo Central, Huesca. Este registro se consiguió datar mediante radiocarbono en diferentes tipos de muestras y aplicando las técnicas de 210Pb y 137Cs para el periodo más reciente. En ambos ejemplos, las combinaciones de métodos y tipo de muestras datadas permitieron obtener cronologías robustas gracias a una importante inversión de tiempo y financiación, siendo el resultado de la colaboración de varios equipos de investigación. En este trabajo se esbozan las dificultades encontradas en la elaboración de ambas cronologías y se presenta el resultado final, fruto de una modelización que combina las diferentes aproximaciones para obtener los modelos de edad definitivos.

&lt;p&gt;High altitude mountain lakes archive high-resolution records of environmental variability (climatic and anthropic). The REPLIM project funded by the INTERREG program (POCTEFA 2014-2020) has implemented a network to understand current and past changes in Pyrenean lakes. In this work, we compare six high altitude lake records along a W- E transect in the South Central Pyrenees: Acherito (1877 m.a.s.l.), La Sierra (2022 m.a.s.l.), Sabocos (1900 m.a.s.l.), Marbor&amp;#233; (2600 m.a.s.l), Urdiceto (2364 m.a.s.l.) and Cregue&amp;#241;a (2633 m.a.s.l.).&lt;/p&gt;&lt;p&gt;In each lake we have analyzed short sediment cores across transects applying sedimentological (facies, grain size, sediment composition, thin sections), geochemical (XRF scanner, elemental and trace metals) physical (Magnetic Susceptibility), isotopic (&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C and &amp;#948; &lt;sup&gt;15&lt;/sup&gt;N of bulk organic matter) and biological (diatoms) techniques. The age models have been constructed with &lt;sup&gt;137&lt;/sup&gt;Cs, &lt;sup&gt;210&lt;/sup&gt;Pb and &lt;sup&gt;14&lt;/sup&gt;C dates.&lt;/p&gt;&lt;p&gt;The sedimentary dynamics and heavy metals depositional history for the last 2000 years provides a temporal context for recent changes. Sedimentary facies variability correlates with climate phases and reflect varied human pressures. In general, during the colder and more humid periods, usually associated with glacier advances (LIA and Late Antiquity LIA), higher surface runoff was generated and, therefore, sediment delivery to the lake increased, in some cases with deposition of coarser facies. Intense watershed disturbances due to human impact were noticeable in lower altitude lakes since early medieval times. All lakes show larger sediment rate variability during the last centuries, but the timing of the onset varies. Lakes located at higher altitudes (Marbor&amp;#233; and Creg&amp;#252;e&amp;#241;a) show larger changes in sedimentation rates and dynamics around the end of the LIA (ca. 1850 CE), while in lower altitude lakes (Sierra, Sabocos, Acherito) occurred later (ca. 1950 CE).&amp;#160; In most lakes, a significant increase in organic matter accumulation started at the end of the 19th century and the trend accelerated since mid 20th century. Diatom and isotopes analyses suggest an increase in lake primary productivity during the last decades. The results indicate that the combined impacts of climate change and increased human pressure in the Pyrenees at the end of the LIA had a greater impact on high-altitude lakes, but recent changes in the 20th century have affected the lakes at all altitudes&lt;/p&gt;&lt;p&gt;All lakes show a similar heavy metal deposition pattern, with enrichment during Roman and Medieval times and a progressive increase since the end of the 18&lt;sup&gt;th&lt;/sup&gt; century (industrialization) and reaching its peak in the middle and late 20&lt;sup&gt;th&lt;/sup&gt; century. Some metals, such as Pb, show a subsequent decline at the end of the 20&lt;sup&gt;th&lt;/sup&gt; century related to the reduction of industrial emissions and the ban on leaded gasoline.&lt;/p&gt;&lt;p&gt;This integrated approach demonstrates the sensitivity of high altitude lake systems to record past changes and highlights the need for multi-archive studies to support regional reconstructions of past environmental and climate changes.&lt;/p&gt;

&lt;p&gt;The last deglaciation (from &amp;#8776;19 kyr BP to the onset of the Holocene) is a time interval characterized by major and abrupt climate changes mostly caused by the Atlantic Meridional Overturning Circulation (AMOC) which is responsible for redistributing heat on a planetary scale, including the Iberian Peninsula. This study is focused in the Western Pyrenees, northern Spain, a southern European region key to understand Northern Hemisphere climate teleconnections associated to several warming and cooling events that took place abruptly. It is especially important to know when precisely these events occurred and what their amplitude was to better understand their causes and impacts on the regional environment.&lt;/p&gt;&lt;p&gt;The climatic events mentioned above are recorded in lake and marine sediments in the central and southern Europe denoting the importance of these records in the transitional zone between the Atlantic and the Mediterranean climatic realms. The glacial-interglacial transition was also identified in isotopic values of speleothems at this latitude, where differences and similarities with the patterns identified in the Greenland record during the last deglaciation are analysed. Even so, there is still no continental record of temperature reconstruction during part of the last deglaciation in the Iberian Peninsula that can be compared with the latest record of fluid inclusions in speleothems in central Europe (Affolter et al., 2019).&lt;/p&gt;&lt;p&gt;In this new study, three stalagmites from Ostolo Cave in the Western Pyrenees were analysed to identify and characterize the timing of the climate variability along the abrupt changes that punctuated the last deglaciation and subsequently generate a reconstruction of the past temperature with the help of fluid inclusion water isotopes. The samples were dated at high precision and cover almost continuously the same period (16.5-10 kyr BP) with a high degree of replication. The speleothem &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O and fluid inclusion water isotopes (&amp;#948;D) records follow closely the well-known changes from high latitudes showing more negative values during GS-1 and H1, related to colder climates, while more positive values were reached during GI-1 and the Early Holocene, pointing towards warmer temperatures. Our Ostolo Cave fluid inclusion temperature record resembles Greenland and Mediterranean sea surface temperature trends and allows for the first time and from a continental record, a continuous reconstruction of temperature throughout the last deglaciation in southern Europe.&lt;/p&gt;

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