How has climate responded to natural perturbations?

Wolff, E. W.; Harrison, S. P.; Knutti, R.; Sanchez-Goñi, M. F.; Wild, O.; Danlau, A.-L.; Masson-Delmotte, V.; Prentice, I. C.; Spahni, R.

Pinus nigra (European black pine) as the dominant species of the last glacial pinewoods in south-western to central Iberia: a morphological study of modern and fossil pollen

Aim Our aim was to discriminate different species of Pinus via pollen analysis in order to assess the responses of particular pine species to orbital and millennial-scale climate changes, particularly during the last glacial period. Location Modern pollen grains were collected from current pine populations along transects from the Pyrenees to southern Iberia and the Balearic Islands. Fossil pine pollen was recovered from the south-western Iberian margin core MD95-2042. Methods We measured a set of morphological traits of modern pollen from the Iberian pine species Pinus nigra, P. sylvestris, P. halepensis, P. pinea and P. pinaster and of fossil pine pollen from selected samples of the last glacial period and the early to mid-Holocene. Classification and regression tree (CART) analysis was used to establish a model from the modern dataset that discriminates pollen from the different pine species and allows identification of fossil pine pollen at the species level. Results The CART model was effective in separating pollen of P. nigra and P. sylvestris from that of the Mediterranean pine group (P. halepensis, P. pinea and P. pinaster). The pollen of Pinus nigra diverged from that of P. sylvestris by having a more flattened corpus. Predictions using this model suggested that fossil pine pollen is mainly from P. nigra in all the samples analysed. Pinus sylvestris was more abundant in samples from Greenland stadials than Heinrich stadials, whereas Mediterranean pines increased in samples from Greenland interstadials and during the early to mid-Holocene. Main conclusions Morphological parameters can be successfully used to increase the taxonomic resolution of fossil pine pollen at the species level for the highland pines (P. nigra and P. sylvestris) and at the group of species level for the Mediterranean pines. Our study indicates that P. nigra was the dominant component of the last glacial south-western/central Iberian pinewoods, although the species composition of these woodlands varied in response to abrupt climate changes.

Holocene biomass burning and global dynamics of the carbon cycle

Fire regimes have changed during the Holocene due to changes in climate, vegetation, and in human practices. Here, we hypothesise that changes in fire regime may have affected the global CO2 concentration in the atmosphere through the Holocene. Our data are based on quantitative reconstructions of biomass burning deduced from stratified charcoal records from Europe, and South-, Central- and North America, and Oceania to test the fire-carbon release hypothesis. In Europe the significant increase of fire activity is dated ≈6000 cal. yr ago. In north-eastern North America burning activity was greatest before 7500 years ago, very low between 7500–3000 years, and has been increasing since 3000 years ago. In tropical America, the pattern is more complex and apparently latitudinally zonal. Maximum burning occurred in the southern Amazon basin and in Central America during the middle Holocene, and during the last 2000 years in the northern Amazon basin. In Oceania, biomass burning has decreased since a maximum 5000 years ago. Biomass burning has broadly increased in the Northern and Southern hemispheres throughout the second half of the Holocene associated with changes in climate and human practices. Global fire indices parallel the increase of atmospheric CO2 concentration recorded in Antarctic ice cores. Future issues on carbon dynamics relatively to biomass burning are discussed to improve the quantitative reconstructions.

Sedimentology, magnetics and chemistry on palaeolake core D100 from the Gobi Desert

The Gaxun Nur Basin in arid China is tectonically influenced by the left-lateral displacements along the Gobi-Altay and Qilian Shan shear zones, resulting in a large pull-apart basin with strong subsidence in the interior. The up to 300 m thick basin fills consist of fluvio-lacustrine fine-grained deposits mainly transported by river discharges from the Tibetan Plateau. They led to a large depositional area of more than 28,000 qkm in size with presently dry terminal lakes at the outer edges. This vast area serves as a main source for loess transport to south-eastern regions of China (Loess Plateau) caused by the variable winter monsoon. Based on geochemical and sedimentological analyses of the sediment core D100 retrieved from a deep drilling in the centre of the Gaxun Nur Basin following questions have to be answered: 1. Reconstruction of the water balance and determination of hydrological cycles during interglacial and glacial periods. 2. Reconstructing variations in lacustrine environment and aeolian activities with respect to transitional phases fro, warm to cold stages (MIS 4 to 5 and older stages). 3. Establishing a sustainable chronology for the last 250 ka.

Revised age models and foraminiferal records obtained for the Last Interglacial period in six marine sediment cores

The dataset contains the revised age models and foraminiferal records obtained for the Last Interglacial period in six marine sediment cores: - the Southern Ocean core MD02-2488 (age model, sea surface temperatures, benthic d18O and d13C for the period 136-108 ka), - the North Atlantic core MD95-2042 (age model, planktic d18O, benthic d18O and d13C for the period 135-110 ka), - the North Atlantic core ODP 980 (age model, planktic d18O, sea surface temperatures, seawater d18O, benthic d18O and d13C, ice-rafted detritus for the period 135-110 ka), - the North Atlantic core CH69-K09 (age model, planktic d18O, sea surface temperatures, seawater d18O, benthic d18O and d13C, ice-rafted detritus for the period 135-110 ka), - the Norwegian Sea core MD95-2010 (age model, percentage of Neogloboquadrina pachyderma sinistral, sea surface temperatures, benthic d18O, ice-rafted detritus for the period 134-110 ka), - the Labrador Sea core EW9302-JPC2 (age model, percentage of Neogloboquadrina pachyderma sinistral, sea surface temperatures, benthic d18O for the period 134-110 ka).

Seismic multichannel reflection profiles from the Gulf of Cadiz, IODP Expedition 339

Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics.

Pueblos, espacio y megaminería en La Rioja : Experiencia educativa en Famatina y Chilecito

En el marco del desarrollo de una experiencia pluridisciplinaria, este proyecto pretende introducir a los alumnos de 4° y 5° del Liceo Víctor Mercante, Universidad Nacional de La Plata, en el análisis, reflexión y concientización de las problemáticas ambientales derivadas de la Megaminería que pretende explotar el Cerro Famatina, La Rioja. Simultáneamente se propone traer las voces de la lucha social a la escuela como así también sensibilizar el entorno. Se contribuirá a lograr una formación integral que posibilite la comprensión del mundo y la interacción con el medio social para transformarlo. Metodológicamente, se comenzó con el planteo de problemáticas e interpretación de fuentes, se realizó un viaje de estudio en donde se hicieron encuestas y entrevistas a actores sociales. Finalmente se realizó una transferencia educativa al colegio y a escuelas de La Plata. El viaje coadyuvó a la comprensión que: la minería a cielo abierto no es una actividad económica sustentable en la medida en que sólo favorece a ciertos grupos de poder y no a la población toda y su ambiente; la impronta de los pueblos originarios no está claramente presente cuando se defiende la economía familiar. Las luchas sociales surgen de la genuina preocupación del pueblo riojano

Pueblos, espacio y megaminería en La Rioja : Experiencia educativa en Famatina y Chilecito

En el marco del desarrollo de una experiencia pluridisciplinaria, este proyecto pretende introducir a los alumnos de 4° y 5° del Liceo Víctor Mercante, Universidad Nacional de La Plata, en el análisis, reflexión y concientización de las problemáticas ambientales derivadas de la Megaminería que pretende explotar el Cerro Famatina, La Rioja. Simultáneamente se propone traer las voces de la lucha social a la escuela como así también sensibilizar el entorno. Se contribuirá a lograr una formación integral que posibilite la comprensión del mundo y la interacción con el medio social para transformarlo. Metodológicamente, se comenzó con el planteo de problemáticas e interpretación de fuentes, se realizó un viaje de estudio en donde se hicieron encuestas y entrevistas a actores sociales. Finalmente se realizó una transferencia educativa al colegio y a escuelas de La Plata. El viaje coadyuvó a la comprensión que: la minería a cielo abierto no es una actividad económica sustentable en la medida en que sólo favorece a ciertos grupos de poder y no a la población toda y su ambiente; la impronta de los pueblos originarios no está claramente presente cuando se defiende la economía familiar. Las luchas sociales surgen de la genuina preocupación del pueblo riojano

Pueblos, espacio y megaminería en La Rioja : Experiencia educativa en Famatina y Chilecito

En el marco del desarrollo de una experiencia pluridisciplinaria, este proyecto pretende introducir a los alumnos de 4° y 5° del Liceo Víctor Mercante, Universidad Nacional de La Plata, en el análisis, reflexión y concientización de las problemáticas ambientales derivadas de la Megaminería que pretende explotar el Cerro Famatina, La Rioja. Simultáneamente se propone traer las voces de la lucha social a la escuela como así también sensibilizar el entorno. Se contribuirá a lograr una formación integral que posibilite la comprensión del mundo y la interacción con el medio social para transformarlo. Metodológicamente, se comenzó con el planteo de problemáticas e interpretación de fuentes, se realizó un viaje de estudio en donde se hicieron encuestas y entrevistas a actores sociales. Finalmente se realizó una transferencia educativa al colegio y a escuelas de La Plata. El viaje coadyuvó a la comprensión que: la minería a cielo abierto no es una actividad económica sustentable en la medida en que sólo favorece a ciertos grupos de poder y no a la población toda y su ambiente; la impronta de los pueblos originarios no está claramente presente cuando se defiende la economía familiar. Las luchas sociales surgen de la genuina preocupación del pueblo riojano