Climate variability in the Aegean Sea (marine record M2, Athos basin) during the past 1500 years

We provide new evidence on sea surface temperature (SST) variations and paleoceanographic/paleoenvironmental changes over the past 1500 years for the north Aegean Sea (NE Mediterranean). The reconstructions are based on multiproxy analyses, obtained from the high resolution (decadal to multi-decadal) marine record M2 retrieved from the Athos basin. Reconstructed SSTs show an increase from ca. 850 to 950 AD and from ca. 1100 to 1300 AD. A cooling phase of almost 1.5 °C is observed from ca. 1600 AD to 1700 AD. This seems to have been the starting point of a continuous SST warming trend until the end of the reconstructed period, interrupted by two prominent cooling events at 1832 ± 15 AD and 1995 ± 1 AD. Application of an adaptive Kernel smoothing suggests that the current warming in the reconstructed SSTs of the north Aegean might be unprecedented in the context of the past 1500 years. Internal variability in atmospheric/oceanic circulations systems as well as external forcing as solar radiation and volcanic activity could have affected temperature variations in the north Aegean Sea over the past 1500 years. The marked temperature drop of approximately ~2 °C at 1832 ± 15 yr AD could be related to the 1809 ?D 'unknown' and the 1815 AD Tambora volcanic eruptions. Paleoenvironmental proxy-indices of the M2 record show enhanced riverine/continental inputs in the northern Aegean after ca. 1450 AD. The paleoclimatic evidence derived from the M2 record is combined with a socio-environmental study of the history of the north Aegean region. We show that the cultivation of temperature-sensitive crops, i.e. walnut, vine and olive, co-occurred with stable and warmer temperatures, while its end coincided with a significant episode of cooler temperatures. Periods of agricultural growth in Macedonia coincide with periods of warmer and more stable SSTs, but further exploration is required in order to identify the causal links behind the observed phenomena. The Black Death likely caused major changes in agricultural activity in the north Aegean region, as reflected in the pollen data from land sites of Macedonia and the M2 proxy-reconstructions. Finally, we conclude that the early modern peaks in mountain vegetation in the Rhodope and Macedonia highlands, visible also in the M2 record, were very likely climate-driven.

Age determination of sediment core NP90-52 (Table 1)

Data on glacial erosion have been compiled and synthesised using a wide range of sediment budget and sediment yield studies from the Svalbard-Barents Sea region. The data include studies ranging in timescale from 1 to 10**6 yr, and in size of drainage basin from 101 to 105 km**2. They show a clear dependence of sediment yield on the mode of glacierization. Polar glaciers erode at rates comparable to those found in Arctic fluvial basins, or about 40 t/km**-2/ yr or 0.02 mm/yr. In contrast, rates of erosion by polythermal glaciers are 800-1000 t/km**2/ yr (or ca 0.3-0.4 mm/yr), while rates from fast-flowing glaciers are slightly more than twice this: 2100 t/km**2/yr (or 1 mm/yr). Similar rates are also found for large glacierized basins like those in the southwestern parts of the Barents Sea. In contrast to the situation in fluvial basins, in which sediment yield typically decreases with increasing basin size, the tendency in glacierized basins is for erosion to be independent of basin size. In studies of sediment yield from glaciers it is sometimes difficult to distinguish between material actually dislodged from the bedrock by glaciers and material dislodged by other processes in interglacial times and simply transported to a depocenter by a glacier. Our data suggest that pulses of sediment resulting from advance of a glacier over previously-dislodged material last on the order of 10**3 yr, and result in inferred erosion rates that are approximately 25% higher than long-term average rates of glacial erosion. The maximum sediment fluxes from the large Storfjorden and Bear Island drainage basins occurred in mid-Pleistocene. The onset of this period of high sediment yield coincided with the onset of the 100 kyr glacial cycle. We presume that this was the beginning of a period of increased glacial activity, but one in which glaciers still advanced and retreated frequently. During the last two to four 100 kyr cycles, however, sediment yields appear to have decreased. This decrease may be the result of the submergence of the Barents Sea. Glacier erosion would be much higher for a subaerial Barents Sea setting than it would be for a present day subsea Barents Sea. A classical question in Quaternary Geology is whether glaciers are more erosive than rivers. We surmise that if factors such as the lithology and the available potential energy (mgh) of the precipitation falling at a given altitude, whether in liquid or solid form, are held constant, then glaciers are vastly more effective agents of erosion than rivers.

Constraints on synrift intrabasinal horst development from alluvial fan and aeolian deposits (Triassic, Fundy Basin, Nova Scotia)

From: Ventra, D. & Clarke, L. E. (eds) Geology and Geomorphology of Alluvial and Fluvial Fans: Terrestrial and Planetary Perspectives. Geological Society, London, Special Publications, 440, http://doi.org/10.1144/SP440.8 # 2016 The Author(s). Published by The Geological Society of London. All rights reserved

La construcción social del medio ambiente : Aprovechamiento y enajenación. El caso del curso inferior del Río Atuel

Desde una estrategia metodológica múltiple, el presente trabajo aborda los aspectos sociales de una problemática ambiental compleja: el potencial restablecimiento del sistema ecológico fluvial, manejo y aprovechamiento del Río Atuel en su curso inferior. En el marco del proyecto de investigación que llevara adelante la Universidad Nacional de La Pampa denominado ?Estudio para la determinación del caudal mínimo necesario para el restablecimiento del sistema ecológico fluvial en el curso inferior del río Atuel? - un recurso natural antropizado-, en el subgrupo específico nos planteamos los siguientes objetivos, que dieron origen al presente informe: identificar los emergentes perceptivos de mayor incidencia en la dimensión ambiental y su problemática, en la población y los referentes institucionales; estudiar las prácticas sociales relativas al uso del agua en el área; sondear la afectación diferencial esperada por los distintos actores sociales e instituciones, frente a posibles cambios en los caudales del Río Atuel y las percepciones acerca de la incidencia en su calidad de vida. Focalizándo el análisis en la población local del área afectada por las problemáticas del Río Atuel y sus caudales, en los depatamentos de Cachileo y Chical Có de la Provincia de La Pampa, nos aproximamos a perspectivas y prácticas sociales propias de un escenario socio-ambiental afectado por la intensificación de las políticas provinciales de gobierno. La temática se abre en torno a la recuperación de un recurso históricamente enajenado, signada por un accionar errante del Estado, propia de una prolongada confrontación jurídica interprovincial, que promovió la intensificación de la problemática ecológica y ambiental en el área. Desde la perspectiva con que se llevó adelante el estudio consideramos que la conceptualización e intervención sociológica debe promoverse, especialmente frente a la configuración de un escenario complejo y contradictorio, en una dimensión de alto impacto en la calidad de vida y el desarrollo local

La construcción social del medio ambiente : Aprovechamiento y enajenación. El caso del curso inferior del Río Atuel

Desde una estrategia metodológica múltiple, el presente trabajo aborda los aspectos sociales de una problemática ambiental compleja: el potencial restablecimiento del sistema ecológico fluvial, manejo y aprovechamiento del Río Atuel en su curso inferior. En el marco del proyecto de investigación que llevara adelante la Universidad Nacional de La Pampa denominado ?Estudio para la determinación del caudal mínimo necesario para el restablecimiento del sistema ecológico fluvial en el curso inferior del río Atuel? - un recurso natural antropizado-, en el subgrupo específico nos planteamos los siguientes objetivos, que dieron origen al presente informe: identificar los emergentes perceptivos de mayor incidencia en la dimensión ambiental y su problemática, en la población y los referentes institucionales; estudiar las prácticas sociales relativas al uso del agua en el área; sondear la afectación diferencial esperada por los distintos actores sociales e instituciones, frente a posibles cambios en los caudales del Río Atuel y las percepciones acerca de la incidencia en su calidad de vida. Focalizándo el análisis en la población local del área afectada por las problemáticas del Río Atuel y sus caudales, en los depatamentos de Cachileo y Chical Có de la Provincia de La Pampa, nos aproximamos a perspectivas y prácticas sociales propias de un escenario socio-ambiental afectado por la intensificación de las políticas provinciales de gobierno. La temática se abre en torno a la recuperación de un recurso históricamente enajenado, signada por un accionar errante del Estado, propia de una prolongada confrontación jurídica interprovincial, que promovió la intensificación de la problemática ecológica y ambiental en el área. Desde la perspectiva con que se llevó adelante el estudio consideramos que la conceptualización e intervención sociológica debe promoverse, especialmente frente a la configuración de un escenario complejo y contradictorio, en una dimensión de alto impacto en la calidad de vida y el desarrollo local

La construcción social del medio ambiente : Aprovechamiento y enajenación. El caso del curso inferior del Río Atuel

Desde una estrategia metodológica múltiple, el presente trabajo aborda los aspectos sociales de una problemática ambiental compleja: el potencial restablecimiento del sistema ecológico fluvial, manejo y aprovechamiento del Río Atuel en su curso inferior. En el marco del proyecto de investigación que llevara adelante la Universidad Nacional de La Pampa denominado ?Estudio para la determinación del caudal mínimo necesario para el restablecimiento del sistema ecológico fluvial en el curso inferior del río Atuel? - un recurso natural antropizado-, en el subgrupo específico nos planteamos los siguientes objetivos, que dieron origen al presente informe: identificar los emergentes perceptivos de mayor incidencia en la dimensión ambiental y su problemática, en la población y los referentes institucionales; estudiar las prácticas sociales relativas al uso del agua en el área; sondear la afectación diferencial esperada por los distintos actores sociales e instituciones, frente a posibles cambios en los caudales del Río Atuel y las percepciones acerca de la incidencia en su calidad de vida. Focalizándo el análisis en la población local del área afectada por las problemáticas del Río Atuel y sus caudales, en los depatamentos de Cachileo y Chical Có de la Provincia de La Pampa, nos aproximamos a perspectivas y prácticas sociales propias de un escenario socio-ambiental afectado por la intensificación de las políticas provinciales de gobierno. La temática se abre en torno a la recuperación de un recurso históricamente enajenado, signada por un accionar errante del Estado, propia de una prolongada confrontación jurídica interprovincial, que promovió la intensificación de la problemática ecológica y ambiental en el área. Desde la perspectiva con que se llevó adelante el estudio consideramos que la conceptualización e intervención sociológica debe promoverse, especialmente frente a la configuración de un escenario complejo y contradictorio, en una dimensión de alto impacto en la calidad de vida y el desarrollo local

Chemistry and grain-size distribution of terrigenous sediments deposited at Site GeoB9501

The Sahara Desert is the largest source of mineral dust in the world. Emissions of African dust increased sharply in the early 1970s, a change that has been attributed mainly to drought in the Sahara/Sahel region caused by changes in the global distribution of sea surface temperature. The human contribution to land degradation and dust mobilization in this region remains poorly understood, owing to the paucity of data that would allow the identification of long-term trends in desertification. Direct measurements of airborne African dust concentrations only became available in the mid-1960s from a station on Barbados and subsequently from satellite imagery since the late 1970s: they do not cover the onset of commercial agriculture in the Sahel region ~170 years ago. Here we construct a 3,200-year record of dust deposition off northwest Africa by investigating the chemistry and grain-size distribution of terrigenous sediments deposited at a marine site located directly under the West African dust plume. With the help of our dust record and a proxy record for West African precipitation we find that, on the century scale, dust deposition is related to precipitation in tropical West Africa until the seventeenth century. At the beginning of the nineteenth century, a sharp increase in dust deposition parallels the advent of commercial agriculture in the Sahel region. Our findings suggest that human-induced dust emissions from the Sahel region have contributed to the atmospheric dust load for about 200 years.

Table 1: Station list with macrobenthos biomass results from the ocean floor

Among the Siberian shelf seas the Kara Sea is most strongly influenced by riverine runoff with nearly 1500 km fresh water discharge per year. This fresh water, discharged mainly by Ob and Yenisei, contains about 3.1 * 106 and 4.6 * 106 tons of total organic carbon per year, respectively (Gordeev et al. 1996). Little is known about the relevance of this organic material for biological communities, neither for the Kara Sea nor for the adjacent deep basins of the central Arctic Ocean. Aiming at elucidating the fate of fluvial matter transported from the rivers via estuaries into the central Arctic Ocean and the relative importance of marine organic matter being produced such information is crucial. Here we present calculations on the organic carbon demand of the Kara Sea macrozoobenthos based on measured biomass (total wet weight [ww] per 0.25 m ) from quantitative box corer samples and empirical relationships between biomass, annual production, annual respiration, and carbon remineralisation. This bottom-up approach may serve as a first estimate of the carbon remineralization potential of a given zoobenthos community (or area) as long as no data on in situ respiration rates are available. Our data basis comprises 54 stations sampled in summer seasons 1997, 1999 and 2000 in the Kara Sea at water depths between 10 and 68 m. The geographical area represented by stations analysed covers roughly 178 000 km**2, which is about one fifth of the total Kara Sea area. In this area, 290 species of invertebrate macrozoobenthos were identified with polychaeta, Crustacea, mollusca and echinodermata being the most abundant. For all stations analysed, mean biomass values ranged between 4.3 and 778.1 g ww/m**2 with organic carbon demands between 3.5 and 43.2 mg C/m**2/d. For the area of 178 000 km2 a preliminary total consumption of 1.4 * 10**6t Corg/y (equivalent to 21.5 mg C/m**2/d) was calculated for the macrozoobenthos. An extrapolation of our data would lead to an annual carbon demand of about 5-7 * 106 t for the whole Kara Sea macrozoobenthos (or 15.5-21.7 mg C/m2/d).

Characterization of the defined MDC types and compilation of MDC initiation times (excel-file 19 kB)

Mud accumulates on continental shelves under a variety of environmental conditions and results in a diverse formation of mud depocenters (MDCs). Their three-dimensional architectures have been in the focus of several recent studies. Due to some terminological confusion concerning MDCs, the present study sets out to define eight individual MDC types in terms of surface sediment distribution and internal geometry. Under conditions of substantial sediment supply, prodeltas (distal zones off river deltas; triangular sheets), subaqueous deltas (disconnected from deltas by strong normal-to-shore currents; wedge-like clinoforms), and mud patches (scattered distribution) and mud blankets (widespread covers) are formed. Forced by hydrodynamic conditions, mud belts in the strict sense (detached from source; elongated bodies), and shallow-water contourite drifts (detached from source; growing normal to prevailing current direction; triangular clinoforms) develop. Controlled by local morphology, mud entrapments (in depressions, behind morphological steps) and mud wedges (triangular clinoforms growing in flow direction) are deposited. Shelf mud deposition took place (1) during early outer-shelf drowning (~14 ka), (2) after inner-shelf inundation to maximum flooding (9.5-6.5 ka), and (3) in sub-recent times (<2 ka). Subsequent expansion may be (1) concentric, in cases where the depocenter formed near the fluvial source, (2) uni-directional, extending along advective current transport paths, and (3) progradational, forming clinoforms that grow either parallel or normal to the bottom current direction. Classical mud belts may be initiated around defined nuclei, the remote sites of which are determined by seafloor morphology rather than the location of the source. From a stratigraphic perspective, mud depocenters coincide with sea-level highstand-related, shelf-wide condensed sections. They often show a conformable succession from transgressive to highstand systems tract stages.