Florence Sylvestre

Bio: Florence Sylvestre is an academic researcher from Aix-Marseille University. The author has contributed to research in topics: Holocene & Climate change. The author has an hindex of 26, co-authored 83 publications receiving 1895 citations. Previous affiliations of Florence Sylvestre include University of Angers & Université Paul Cézanne Aix-Marseille III.

Hydrological Variability in South America Below the Tropic of Capricorn (Pampas and Patagonia, Argentina) During the Last 13.0 Ka

Abstract: New limnogeological results (Laguna Mar Chiquita, 30°S) at the middle latitudes in the subtropical Pampean plains of Southern South America are used to establish comparisons with records spanning Late Glacial times and the Holocene covering the Northern Andean Patagonia and the Extra Andean Southern Patagonia. Historical and archaeological data were also used to enlarge existing environmental reconstructions in the central plains of Southern South America. Two groups of climate records – at both sides of the Arid Diagonal- can be distinguished according to their hydrological response during dominant warm or cold climatic phases. The first group includes records from the Pampean region and allows to reconstruct the past activity of the South America Monsoonal System. The second group includes archives of the Patagonian climate, as well as the Salinas del Bebedero, and provides a record of past changes in the strength and latitudinal position of the Southern Westerlies.

Foraminiferal assemblages in a hypersaline lagoon, araruama (r.j.) brazil

Abstract: Foraminiferal assemblages were studied in 93 samples collected in the lagoon of Araruama and in the adjacent area. The lagoon of Araruama is one of the largest hypersaline lagoons in the world, with a salinity range of 52–65 ‰. Historical reports show that the lagoon has been hypersaline since at least the 16th century. Foraminiferal assemblages are dominated by miliolids, mainly Triloculina oblonga, and rotaliids, with Ammonia tepida and the less abundant Cribroelphidium excavatum var. selseyense . Textulariids are almost absent. This assemblage is similar to those usually reported from hypersaline lagoons with sandy carbonate-rich sediments and from salt marshes. A high proportion of aberrant tests was observed. Anthropogenic stresses do not seem to be responsible for these morphological abnormalities, which are attributed to high salinity conditions and to changes of salinity. However, the higher proportion of Ammonia tepida in the more impacted northern part of the lagoon is probably due to human impact.

The Lake Chad hydrology under current climate change

Abstract: Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to ~50 million people and supports unique ecosystems and biodiversity. In the past decades, it became a symbol of current climate change, held up by its dramatic shrinkage in the 1980s. Despites a partial recovery in response to increased Sahelian precipitation in the 1990s, Lake Chad is still facing major threats and its contemporary variability under climate change remains highly uncertain. Here, using a new multi-satellite approach, we show that Lake Chad extent has remained stable during the last two decades, despite a slight decrease of its northern pool. Moreover, since the 2000s, groundwater, which contributes to ~70% of Lake Chad's annual water storage change, is increasing due to water supply provided by its two main tributaries. Our results indicate that in tandem with groundwater and tropical origin of water supply, over the last two decades, Lake Chad is not shrinking and recovers seasonally its surface water extent and volume. This study provides a robust regional understanding of current hydrology and changes in the Lake Chad region, giving a basis for developing future climate adaptation strategies.

Ecology and Applications of Benthic Foraminifera

Abstract: In this volume John Murray investigates the ecological processes that control the distribution, abundance, and species diversity of benthic foraminifera in environments ranging from marsh to the deepest ocean. To interpret the fossil record it is necessary to have an understanding of the ecology of modern foraminifera and the processes operating after death leading to burial and fossilisation. This book presents the ecological background required to explain how fossil forms are used in dating rocks and reconstructing past environmental features including changes of sea level. It demonstrates how living foraminifera can be used to monitor modern-day environmental change. Ecology and Applications of Benthic Foraminifera presents a comprehensive and global coverage of the subject using all the available literature. It is supported by a website hosting a large database of additional ecological information (www.cambridge.org/0521828392) and will form an important reference for academic researchers and graduate students in Earth and Environmental Sciences.

The Anthropocene is functionally and stratigraphically distinct from the Holocene

Abstract: Human activity is leaving a pervasive and persistent signature on Earth. Vigorous debate continues about whether this warrants recognition as a new geologic time unit known as the Anthropocene. We review anthropogenic markers of functional changes in the Earth system through the stratigraphic record. The appearance of manufactured materials in sediments, including aluminum, plastics, and concrete, coincides with global spikes in fallout radionuclides and particulates from fossil fuel combustion. Carbon, nitrogen, and phosphorus cycles have been substantially modified over the past century. Rates of sea-level rise and the extent of human perturbation of the climate system exceed Late Holocene changes. Biotic changes include species invasions worldwide and accelerating rates of extinction. These combined signals render the Anthropocene stratigraphically distinct from the Holocene and earlier epochs.

Global Scale Attribution of Anthropogenic and Natural Dust Sources and their Emission Rates Based on MODIS Deep Blue Aerosol Products

Abstract: [1] Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Here we present a global-scale high-resolution (0.1°) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the Sahel. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small-scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes.

The History of South American Tropical Precipitation for the Past 25,000 Years

Abstract: Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas.