Descifrando el clima de los últimos 2,58 ma. ¿Cómo, dónde y por qué? Registros continentales y marinos

El estudio de los climas del pasado, especialmente de aquellos ocurridos en el Cuaternario, es fundamental para comprender tanto el funcionamiento de los procesos geoambientales actuales como su evolución en un pasado reciente sin actividad antrópica. Para realizar estos estudios nos basamos en las informaciones almacenadas en diferentes tipos de registros tanto terrestres (sedimentos lacustres, estalagmitas, turberas, anillos de árboles, etc.) como marinos (sedimentos marinos, corales, etc.). En este capítulo revisaremos las características principales de los registros paleoclimáticos del Cuaternario, incluyendo su continuidad, resolución o sensibilidad, y la metodología comúnmente aplicada a su estudio, partiendo del trabajo de campo y finalizando con las técnicas de datación más utilizadas. Por último, se describen tres ejemplos de reconstrucciones paleoambientales en la Península Ibérica atendiendo a su escala temporal: (1) los últimos 500.000 años (escala orbital) con registros marinos del Mediterráneo Occidental; (2) el final del último ciclo glaciar desde las cuevas de la costa Cantábrica; y (3) las variaciones paleohidrológicas de los últimos 2.000 años a partir de registros lacustres de paleoavenidas. Algunas ideas sobre líneas futuras de esta investigación se apuntan al final del capítulo.Departamento de Procesos Geoambientales y Cambio Global, Instituto Pirenaico de Ecología, Consejo Superior de Investigaciones Científicas, EspañaDepartamento de Geografía y Geología, Universidad de León, EspañaDepartamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, EspañaDepartamento de Investigación en Recursos Geológicos, Instituto Geológico y Minero de España, Españ

A ?password? game application for learning

La aplicación de entornos educativos cada vez más dinámicos y motivacionales ha impulsado una corriente docente que utiliza recursos digitales, basados en el juego, para la enseñanza. La gamificación, entendida como el empleo del juego para el desarrollo de actividades formativas en el aula, constituye una herramienta para trabajar sobre distintos tipos de aprendizaje y grupos de estudiantes, pudiendo ser empleada antes, durante y al final de las sesiones presenciales en el aula o de forma online. De este modo han surgido, en los últimos años, todo un conjunto de herramientas docentes que contribuyen a dirigir y facilitar el proceso de enseñanza-aprendizaje, y posibilitan una escuela más inclusiva, personalizada y capaz de fomentar a la vez el trabajo sobre otras competencias transversales. Con este fin se ha diseñado una aplicación que simula el ?rosco? del popular programa televisivo ?Pasapalabra?. El objetivo propuesto es contribuir a la incorporación de conceptos geológicos en asignaturas de Ciencias de la Tierra del grado de magisterio en educación primaria, a través del juego. El desarrollo de competencias basado en los videojuegos, dentro del contexto de la gamificación, fomenta el aprendizaje activo y la adquisición de conocimientos geológicos mediante el manejo de nuevas tecnologías a través de medios digitales gratuitos y de fácil acceso. El rosco geológico proporciona, además, una forma de repaso antes, durante y después de cada unidad didáctica, y puede ser utilizado como elemento evaluador. Este tipo de juegos promueve la motivación del alumnado, dirige el aprendizaje y estimula la capacidad de búsqueda de información de alumnos con necesidades especiales.The integration of educational environments increasingly dynamic and motivational have triggered a current tendency based on the use of digital resources. Gamification, understood as the use of games for the development of learning activities that can be developed either in the classroom or online before, during and after the sessions, is a tool that can drive the teaching-learning process. In recent years, a wide variety of teaching tools have contributed to lead and promote learning, allowing the development of a more inclusive school, personalized and capable of promoting, at the same time, the acquisition of transferable skills. For that purpose, we have designed an application that simulates the popular tv program ?Password?. The main goal is to contribute to the learning of geological concepts in Earth Sciences classrooms from the Primary Education Degree, using games. The development of skills through videogames, within the context of gamification, promotes active learning and the acquisition of geological knowledge using new technologies through free and easy to access digital environments. The ?Geologic Password? also provides a way for reviewing knowledge before, during, and after each learning unit and can be used as a method for evaluation. This type of games improves student´s motivation, driving the learning process and increasing the ability to search for information in those students with special needs

Diatom and vegetation responses to Late Glacial and Early Holocene climate changes at Lake Estanya (Southern Pyrenees, NE Spain)

We investigate Lake Estanya's diatom and pollen records from the Late Glacial (LG) to the Early Holocene (EH), in order to compare limnological and vegetation responses to common climate forcing. The biotic changes recognized in this study largely agree with the hydrological evolution of the lake described previously for the same period. The diatom record shows high sensitivity to fluctuations in both lake level and salinity concentration as consequence of climate shifts. In addition vegetation results indicate that the area could have played an important role as regional vegetation refuge. Shallow lake conditions during the Last Glacial Maximum (LGM) were punctuated by relatively deeper freshwaters between 19.3 and 18.6 cal kyr BP and at 18.0 cal kyr BP, as recorded by diatom shifts. A subsequent increasing aridity trend, coinciding with the Mystery Interval (MI), affected the diatom accumulation rates, which dropped to its minimum values between 17.2 to 14.7 cal kyr BP. Particularly dry and cold conditions during the LGM and MI are supported by the largest values of steppic pollen taxa of the whole sequence, which account for up to 40%. However, relatively high values of Betula during the Heinrich Event 1 suggest a plausible regional vegetation refuge. Abrupt cooling and warming episodes within the LG triggered remarkable ecological threshold crossings in the diatom communities, especially during the stadial/interstadial episodes. At this point, the vegetation reflect the onset of warm conditions during the Bølling/Allerød with the partial substitution of Betula by Marcescent and Evergreen Quercus, what probably indicates the arrival of temperate taxa to the area and the likely migration of birch to higher altitudes. The Younger Dryas Stadial shows a complex ecological response. Diatoms are very poorly preserved, but aquatic taxa reach their highest values. An increase in Marcescent Quercus during this cold stage lends further support to the hypothesis that this is a regional vegetation refuge. Low lake levels recorded during the EH affected the development and preservation of diatom communities. A delay in the onset of humid conditions for the EH is also supported by the vegetation composition, characterized by the maximum expansion of Juniperus

Millennial land use explains modern high‐elevation vegetation in the submediterranean mountains of Southern Europe

Aim Pinewood decline and scrubland expansion are major features of Late Holocene vegetation history in the Cantabrian Range. However, the drivers of this remarkable vegetation shift remain to be investigated. Here, we aim at disentangling the role of past land use and climate in shaping the high-elevation Cantabrian landscape during the past two millennia. Location Cantabrian Range (northern Iberia). Taxa Pinus sylvestris, Betula, Ericaceae, Juniperus, Poaceae. Methods We conducted high-resolution multiproxy palaeoecological analyses (pollen, plant macrofossils, microscopic charcoal and dung fungi) on lake sediments from Lago del Ausente to reconstruct vegetation, fire occurrence and grazing through time. The chronology is based on 14C (terrestrial plant macrofossils) and 210Pb dating, and Bayesian age-depth modelling (‘rbacon’). We carried out cross-correlation analysis to quantify vegetation responses to fire. Results Between 250 and 900 CE, the vegetation above 1700 m a.s.l. consisted of subalpine scrubland and scattered P. sylvestris trees/stands. Pinewoods with Betula were widespread at slightly lower elevation. This vegetation was resilient to moderate fire disturbance associated with limited pastoral activities. In contrast, enhanced fire occurrence alongside heavier pastoralism led to the demise of pinewoods and their replacement with Betula stands, subalpine scrublands, and meadows between 900 and 1100 CE. Later, the subalpine scrubland-birch tree line did not respond to Little Ice Age cooling. However, further intensification of transhumant herding between 1300 and 1860 CE (‘La Mesta’) triggered birch decline and the establishment of the modern treeless landscape. Main conclusions The extant high-elevation vegetation of the Cantabrian Range is largely the legacy of intensive land use starting more than one millennium ago. Recurrent and severe fires to promote pasturelands led to the regional extirpation of the previously widespread Pinus sylvestris. Future management should aim at preserving the valuable cultural open landscape of mountain scrubland and meadows and also at restoring patches of ancient pine-birch woodlands

Vegetation changes and hydrological fluctuations in the Central Ebro Basin (NE Spain) since the Late Glacial period: Saline lake records

The final version is available at: http://www.sciencedirect.com/science/journal/00310182Although the Central Ebro Basin (Northeastern Iberian Peninsula) is both the northernmost semi-arid area in Europe and one of the regions with the largest biodiversity, it has been insufficiently studied in terms of past climate variability due to the scarcity of suitable sites for palaeoenvironmental analyses. Previous studies from ephemeral saline lakes in the area, mainly based on palynological data, show abrupt and rapid arid/humid transitions throughout the last glacial cycle highlighting a complex palaeohydrological evolution. New cores from two saline lakes (La Playa and La Salineta) in the Los Monegros area provide multi-proxy records including sedimentology, geochemistry, and pollen indicators. This study, together with a detailed and comprehensive review of the main saline records from the Central Ebro Basin, enables us tos reconstruct a comprehensive picture of the palaeoclimate evolution during the last glacial cycle. One of the main results of this study is the alternation of humid and dry phases as a characteristic of the climate evolution during the Lateglacial. Additionally, the study suggests an important role of the increased flow from the Pyrenean rivers during deglaciation in the hydrological balance of the Central Ebro Basin. It is found that the Early Holocene is the wettest period over the sequence studied contrasting with the arid Middle Holocene interval, which is frequently absent as a result of intense aeolian erosive processes. Although anthropogenic activity partially masks the climate signal from the palynological data in the uppermost part of the sequences studied, there are some sedimentological evidences for a climate change during the last 2000 years resulting in a recovery of average saline lake levels in the Central Ebro Basin.This work was part of the project “Arid periods in the Mediterranean area since the Last Glacial Maximum” (REN 2000-1136/CLI), and LIMNOCLIBER (REN 2003-09130-C02-02), funded by the CICYT, and the project “Environmental evolution and effects of the anthropogenic impact in the lacustrine complex of Bujaraloz–Sástago” (PO23/2001), funded by the Aragon regional government (DGA). We acknowledge the Pyrenean Institute of Ecology (CSIC) for financial support.Peer reviewe

Palaeolimnological evidence for an east-west climate see-saw in the Mediterranean since AD 900

During the period of instrumental records, the North Atlantic Oscillation (NAO) has strongly influenced inter-annual precipitation variations in the western Mediterranean, while some eastern parts of the basin have shown an anti-phase relationship in precipitation and atmospheric pressure. Here we explore how the NAO and other atmospheric circulation modes operated over the longer timescales of the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). High-resolution palaeolimnological evidence from opposite ends of the Mediterranean basin, supplemented by other palaeoclimate data, is used to track shifts in regional hydro-climatic conditions. Multiple geochemical, sedimentological, isotopic and palaeoecological proxies from Estanya and Montcortés lakes in northeast Spain and Nar lake in central Turkey have been cross-correlated at decadal time intervals since AD 900. These dryland lakes capture sensitively changes in precipitation/evaporation (P/E) balance by adjustments in water level and salinity, and are especially valuable for reconstructing variability over decadal-centennial timescales. Iberian lakes show lower water levels and higher salinities during the 11th to 13th centuries synchronous with the MCA and generally more humid conditions during the 'LIA' (15th-19th centuries). This pattern is also clearly evident in tree-ring records from Morocco and from marine cores in the western Mediterranean Sea. In the eastern Mediterranean, palaeoclimatic records from Turkey, Greece and the Levant show generally drier hydro-climatic conditions during the LIA and a wetter phase during the MCA. This implies that a bipolar climate see-saw has operated in the Mediterranean for the last 1100. years. However, while western Mediterranean aridity appears consistent with persistent positive NAO state during the MCA, the pattern is less clear in the eastern Mediterranean. Here the strongest evidence for higher winter season precipitation during the MCA comes from central Turkey in the northeastern sector of the Mediterranean basin. This in turn implies that the LIA/MCA hydro-climatic pattern in the Mediterranean was determined by a combination of different climate modes along with major physical geographical controls, and not by NAO forcing alone, or that the character of the NAO and its teleconnections have been non-stationary. © 2011 Elsevier B.V

Abrupt Diatom Responses to Recent Climate and Land Use Changes in the Cantabrian Mountains (NW Spain)

[Abstract] The multi-proxy study of sediment cores from Lake Isoba (43° 02′ N, 5° 18′ W; 1400 m a.s.l.) allows a detailed assessment of the past hydrological and environmental dynamics in north-western Iberia resulting from the interplay between climate variability and anthropogenic impact. The combination of diatom stratigraphy, sedimentology and high-resolution elemental geochemistry along with a robust chronological framework (established by 210Pb, 137Cs and 14C dating) provides a detailed environmental reconstruction for the past ~ 500 years. Abrupt changes in the fossil diatom assemblages indicate a high sensitivity of this small lake to past environmental change and allow identifying four major stages related to the main climate fluctuations of the Little Ice Age (LIA) and recent warming. High lake levels, enhanced runoff and higher productivity characterised the middle phase of the LIA (~ 1550 to 1630 CE), indicating an overall wet climate. Conversely, shallow lake levels, decreased runoff and relatively low productivity prevailed during the last phase of the LIA and the onset of the Industrial Era (~ 1630 to 1925 CE), likely due to colder and drier conditions. High lake levels and higher carbonate input occurred after ~ 1925 CE until the 1980s CE, when our data show an abrupt drop in lake levels probably caused by a regional negative rainfall anomaly related to climate warming during the past decades. Finally, since ~ 1997 CE a remarkable and abrupt increase in the lake nutrient load and turbidity is detected, probably associated with the replacement of transhumant sheep flocks with staying cattle. The main environmental changes reconstructed at Lake Isoba mostly agree with other palaeoclimatic records from northern Spain. However, the hydrological patterns reconstructed are opposed to those observed on the northern slopes of the Cantabrian Mountains. The recent and strong impact of land-use changes on the lake, causing more ecological disruptions than previous climate changes, is noteworthy and demonstrates the high sensitivity of mountain lakes to human activities in a global change context.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Open Access funding provided by University of the Basque Country. This study was financially supported by the GECANT project (CGL2017-82703-R) (AEI/FEDER, UE

Hydrogeochemical characteristics of the Saliencia lakes (Somiedo Natural Park, NW Spain): trophic state and relationship with anthropogenic pressures

The high-mountain lakes of Saliencia (El Valle, La Cueva, Calabazosa and Cerveriz), in the Somiedo Natural Park (Asturias, NW Spain), have been subject to different anthropogenic pressures, including metal mining, cattle grazing, damming activities and water channelling work for hydroelectric exploitation. This paper reports the results of a recent geochemical and limnological study conducted in these lakes, for which no previous study existed in the literature. Based on depth profiles of temperature, conductivity, pH and ORP, as well as dissolved oxygen, chlorophyll-a, organic carbon, nutrient and metal concentration, we discuss the impact of anthropogenic pressure on the lakes. In the sampling period (July to September, 2014-2016), most of the lakes showed a marked stratification with vertical gradients as a result of different physical and (bio)geochemical processes. All the lakes showed a good environmental state with no apparent metal pollution. However, this set of mountain lakes is not homogeneous with regard to nutrient availability, primary productivity, or hypolimnetic oxygen deficit and a range of trophic conditions exist from oligotrophic (El Valle) to eutrophic (Calabazosa). This trend shows a good correlation with total phosphorus concentration (e.g., 10 µg/L P in El Valle vs. 35 µg/L P in Calabazosa), though erosive processes in the catchment may also have contributed to increase the oxygen consumption rate through an import of allochthonous organic matter. Higher nitrate contents seem to characterize the areas with higher grazing pressure (e.g., El Valle), though the obtained data do not allow us to establish any evident relationship between cattle activity and eutrophication

The influence of subaquatic springs in lacustrine sedimentation: Origin and paleoenvironmental significance of homogenites in karstic Lake Banyoles (NE Spain)

Banyoles (42°08′N, 2°45′E) is the largest and deepest lake of karstictectonic origin in the Iberian Peninsula. The lake comprises two basins and six sub-circularly shaped sub-basins fed by subaquatic springs. Periods of intense groundwater inflow in the deepest sub-basins lead to the fluidization and re-suspension of previously deposited sediments and subsequent settling forming homogenite deposits on the southern basin intermediate platforms. The multiproxy analysis of sediment cores combined with high resolution seismic stratigraphy (3.5 kHz pinger and multi-frequency Chirp surveys) allows a precise reconstruction of depositional environments and related hydrological variability and groundwater inflowduring the last ca. 7.6 cal kyr BP. According to the agemodel based on 137Cs, 210Pb and AMS 14C dating, homogenite deposition occurred between 7.2 and 5.5 cal kyr BP, stopped during the middle Holocene (5.52.8 cal kyr BP) and greatly increased during the last two millennia with a total of 17 homogenite layers individually up to 75 cm-thick. The onset of this unique sedimentation mode at ca. 3 cal kyr BP coincides with an increase in lake level, evidenced by the onlapping of fine-grained, distal sediments over coarser massive, carbonate-rich, littoral deposits. A detailed, multidisciplinary study of the homogenites (sedimentology, physical properties, high-resolution elemental geochemistry, mineral composition, grain-size, organic matter content and SEM) combined with seismic stratigraphy demonstrates that the fluidization events triggering the formation of the homogenites were caused by higher and more intense local groundwater inflow, related to increased rainfall during the Late Holocene and likely intensified by land use changes during the last millennium