- Email: [email protected]
Decadal-scale natural Arctic climate variation simulated with a comprehensive Earth System Model
Abstracts / Quaternary International 279-280 (2012) 9–120
the Przeworsk culture the sediment facies indicates mainly colluvial processes. GEOARCHAEOLOGY OF THE COTTONWOOD RIVER BASIN, FLINT HILLS, EAST-CENTRAL KANSAS, USA Jared Beeton. Adams State College, United States E-mail address: [email protected]
Temporal and spatial patterns of landscape evolution strongly influence the temporal and spatial patterns of the archaeological record in drainage systems. In this geoarchaeological investigation we took a basin-wide approach in assessing the soil stratigraphy, lithostratigraphy, and geochronology of alluvial deposits and associated buried soils in the Cottonwood River basin of east-central Kansas. When stratigraphic sequences and radiocarbon chronologies are compared by stream size and landform type, patterns emerge. In the valleys of high-order streams (4th order) the Younger Dryas Chronozone (ca. 11,000-10,000 14C yr BP) was characterized by slow aggradation accompanied by pedogenesis, resulting in the development of organic-rich cumulic soils. Between ca. 10,000 and 4,900 14C yr BP, aggradation punctuated by soil formation was the dominant process in those valleys. Alluvial fans formed on the margins of highorder stream valleys during the early and middle Holocene (ca. 9000-5000 14 C yr BP), and continued to develop slowly until ca. 3000-2000 14C yr BP. The late-Holocene record of high-order streams is characterized by episodes of entrenchment, rapid aggradation, and slow aggradation punctuated by soil development. By contrast, the early and middle Holocene (ca. 10,000-5000 14C yr BP) was a period of net erosion in the valleys of low-order streams. However, during the late Holocene small valleys became zones of net sediment storage. Consideration of the effects of these temporal and spatial patterns of landscape evolution on the archaeological record is crucial for accurately interpreting that record and searching for buried archaeological deposits dating to specific cultural periods. LATEGLACIAL AND EARLY HOLOCENE ENVIRONMENTAL HISTORY OF THE SOUTHERN VOSGES MOUNTAINS, NORTH-EAST FRANCE
45
in Brazil as well as marine records show that the response of ecosystems on large scale climate change can be within centuries or decades. Studies from different regions indicate how tropical ecosystems evolved to what they are today. Furthermore they show how sensitive ecosystems are to climate change and how ecosystems responded to natural and anthropogenic environmental changes during the past. This knowledge will help us to understand how ecosystems might change under the ongoing Global Change. DECADAL-SCALE NATURAL ARCTIC CLIMATE VARIATION SIMULATED WITH A COMPREHENSIVE EARTH SYSTEM MODEL Alexander Beitsch. Max Planck Institute for Meteorology, Germany E-mail address: [email protected]
Arctic climate is characterized by substantial changes in surface temperature throughout the last millennium with high-latitude variations being amplified compared to those at mid-latitudes. It remains unclear how much of the recent warming is attributable to internal variability. We investigate Arctic climate variation simulated with the Max Planck Institute's Earth System Model in the framework of the “Community Simulations of the Last Millennium”. A 3000 yr control integration allows for a thorough assessment of internal variations. Particular warm events with longitudinal and temporal patterns comparable to the observed early 20th century warming are found in the control integration. We examine the relative role of lateral changes in atmospheric and oceanic heat transports. Enhanced ocean heat transport alters sea-ice extent in the Barents Sea which is accompanied by shifts in the atmospheric circulation regimes. Both variations contribute significantly to events of particular strong surface air temperature anomalies. The model data show the decadal-scale warm events to be initialized by enhanced Arctic North-Atlantic exchange processes. DIP DIRECTION CONTROLS OF BEDROCK ON CHANNEL MORPHOLOGIES IN VAL LUMNEZIA (GRAUBÜNDEN, EASTERN SWISS ALPS) Toufik Bekaddour. Bern, Switzerland
Carole Bégeot. UMR 6249 Chrono-environment, France
E-mail address: toufi[email protected]
E-mail address: [email protected]
A multi-proxy analysis was applied to a Lateglacial and early Holocene sequence of Lake Sewen (sewensee, southern Vosges, 500 m asl). The vegetation history was reconstructed by means of high resolution pollen data. Previous palynological studies from this site indicate well documented lateglacial records but without chronological framework. The sediment sequence of the present study have been well dated by a combination of ten radiocarbon dates and the identification of two tephra layers: the Laacher See, c. 12.9 0.1 ka, and the Vedde Ash, c. 12.1 0.1 ka. The stratigraphic position of these time markers suggests a hiatus during the allerod/younger dryas transition. In addition to pollen data, palaeoenvironmental reconstructions were also supported by the interpretation of sedimentologicals processes using magnetic susceptibility, granulometry, mineralogy and organic matter content. These records indicate environmental response to major lateglacial climatic changes including century-scale cold events like the intra-Bølling cold period, Older Dryas, and intra-Allerød cold period. ECOLOGICAL RESPONSE ON ENVIRONMENTAL CHANGE IN TROPICAL SOUTH AMERICA DURING THE LATE QUATERNARY Hermann Behling. Georg-August-University Göttingen, Department of P, Germany E-mail address: [email protected]
Detailed records on vegetation and environmental changes during the late Quaternary, based on pollen, charcoal and multivariate data analyses, provide insights on past ecological response on environmental changes. Several examples from South America will be presented. Studies from the Ecuadorian Andes as well as from the lowlands and highlands of Brazil reflect interesting ecological responses to climate change, fire and human impact. Results from continental records from the lowlands and highlands
The bedding orientation of bedrock exerts a prime control in the nature and the rates of sediment transfer on mountainous landscapes. Here, we address one particular situation, in which the dip angle of the bedrock is subparallel to the topographic slope (termed dip-slope). Such an arrangement results in the potential for large-scale deep-seated landsliding with bedding or jointing acting as glide planes. Hillslopes with the opposite situation (non-dip slope) have no such preconditioning, and denude through detachment and incision. The Val Lumnezia, Eastern Swiss Alps (Graubünden) contains both dip-slope and non-dip slope valley flanks. The topographic slope of the western valley flank parallels Mesozoic metasediments (dip-slope situation) whereas the Bündner schists on the opposite valley dip perpendicular to the topographic slope (non-dip slope situation). We analyse the relationship between upstream size of drainage basins A and channel gradients S. Where channels are graded and actively shape the landscape, channel gradient is directly related to basin area following Flint's (1974) law: S ¼ ksA-? where ks and ? denote the channels steepness and concavity, respectively. The western valley sides are characterized by low ? values ranging from 0.1 to 0.2, and equally display low ks indices of approximately 150 m0.9. Streams on the eastern valley side have higher ? values ranging between 0.3 and 0.8 and higher ks indices reaching 280 m0.9. The high ks and ? values on eastern valley sides are compatible with the rapid dissection of the channel network into landscapes where low hillslope slip rates allow the channel network to actively shape the landscapes. This is in contrast to the western valley sides, where low ks and ? values suggest that the channel network is continually destabilized by rapid deep-seated landsliding. RECONSTRUCTION OF HISTORIC FUNGAL BARCODING DNA PRESERVED IN PERMAFROST
COMMUNITIES
Eva Bellemain. NCB, NHM; University of Oslo, Norway E-mail address: [email protected]
BY
the Przeworsk culture the sediment facies indicates mainly colluvial processes. GEOARCHAEOLOGY OF THE COTTONWOOD RIVER BASIN, FLINT HILLS, EAST-CENTRAL KANSAS, USA Jared Beeton. Adams State College, United States E-mail address: [email protected]
Temporal and spatial patterns of landscape evolution strongly influence the temporal and spatial patterns of the archaeological record in drainage systems. In this geoarchaeological investigation we took a basin-wide approach in assessing the soil stratigraphy, lithostratigraphy, and geochronology of alluvial deposits and associated buried soils in the Cottonwood River basin of east-central Kansas. When stratigraphic sequences and radiocarbon chronologies are compared by stream size and landform type, patterns emerge. In the valleys of high-order streams (4th order) the Younger Dryas Chronozone (ca. 11,000-10,000 14C yr BP) was characterized by slow aggradation accompanied by pedogenesis, resulting in the development of organic-rich cumulic soils. Between ca. 10,000 and 4,900 14C yr BP, aggradation punctuated by soil formation was the dominant process in those valleys. Alluvial fans formed on the margins of highorder stream valleys during the early and middle Holocene (ca. 9000-5000 14 C yr BP), and continued to develop slowly until ca. 3000-2000 14C yr BP. The late-Holocene record of high-order streams is characterized by episodes of entrenchment, rapid aggradation, and slow aggradation punctuated by soil development. By contrast, the early and middle Holocene (ca. 10,000-5000 14C yr BP) was a period of net erosion in the valleys of low-order streams. However, during the late Holocene small valleys became zones of net sediment storage. Consideration of the effects of these temporal and spatial patterns of landscape evolution on the archaeological record is crucial for accurately interpreting that record and searching for buried archaeological deposits dating to specific cultural periods. LATEGLACIAL AND EARLY HOLOCENE ENVIRONMENTAL HISTORY OF THE SOUTHERN VOSGES MOUNTAINS, NORTH-EAST FRANCE
45
in Brazil as well as marine records show that the response of ecosystems on large scale climate change can be within centuries or decades. Studies from different regions indicate how tropical ecosystems evolved to what they are today. Furthermore they show how sensitive ecosystems are to climate change and how ecosystems responded to natural and anthropogenic environmental changes during the past. This knowledge will help us to understand how ecosystems might change under the ongoing Global Change. DECADAL-SCALE NATURAL ARCTIC CLIMATE VARIATION SIMULATED WITH A COMPREHENSIVE EARTH SYSTEM MODEL Alexander Beitsch. Max Planck Institute for Meteorology, Germany E-mail address: [email protected]
Arctic climate is characterized by substantial changes in surface temperature throughout the last millennium with high-latitude variations being amplified compared to those at mid-latitudes. It remains unclear how much of the recent warming is attributable to internal variability. We investigate Arctic climate variation simulated with the Max Planck Institute's Earth System Model in the framework of the “Community Simulations of the Last Millennium”. A 3000 yr control integration allows for a thorough assessment of internal variations. Particular warm events with longitudinal and temporal patterns comparable to the observed early 20th century warming are found in the control integration. We examine the relative role of lateral changes in atmospheric and oceanic heat transports. Enhanced ocean heat transport alters sea-ice extent in the Barents Sea which is accompanied by shifts in the atmospheric circulation regimes. Both variations contribute significantly to events of particular strong surface air temperature anomalies. The model data show the decadal-scale warm events to be initialized by enhanced Arctic North-Atlantic exchange processes. DIP DIRECTION CONTROLS OF BEDROCK ON CHANNEL MORPHOLOGIES IN VAL LUMNEZIA (GRAUBÜNDEN, EASTERN SWISS ALPS) Toufik Bekaddour. Bern, Switzerland
Carole Bégeot. UMR 6249 Chrono-environment, France
E-mail address: toufi[email protected]
E-mail address: [email protected]
A multi-proxy analysis was applied to a Lateglacial and early Holocene sequence of Lake Sewen (sewensee, southern Vosges, 500 m asl). The vegetation history was reconstructed by means of high resolution pollen data. Previous palynological studies from this site indicate well documented lateglacial records but without chronological framework. The sediment sequence of the present study have been well dated by a combination of ten radiocarbon dates and the identification of two tephra layers: the Laacher See, c. 12.9 0.1 ka, and the Vedde Ash, c. 12.1 0.1 ka. The stratigraphic position of these time markers suggests a hiatus during the allerod/younger dryas transition. In addition to pollen data, palaeoenvironmental reconstructions were also supported by the interpretation of sedimentologicals processes using magnetic susceptibility, granulometry, mineralogy and organic matter content. These records indicate environmental response to major lateglacial climatic changes including century-scale cold events like the intra-Bølling cold period, Older Dryas, and intra-Allerød cold period. ECOLOGICAL RESPONSE ON ENVIRONMENTAL CHANGE IN TROPICAL SOUTH AMERICA DURING THE LATE QUATERNARY Hermann Behling. Georg-August-University Göttingen, Department of P, Germany E-mail address: [email protected]
Detailed records on vegetation and environmental changes during the late Quaternary, based on pollen, charcoal and multivariate data analyses, provide insights on past ecological response on environmental changes. Several examples from South America will be presented. Studies from the Ecuadorian Andes as well as from the lowlands and highlands of Brazil reflect interesting ecological responses to climate change, fire and human impact. Results from continental records from the lowlands and highlands
The bedding orientation of bedrock exerts a prime control in the nature and the rates of sediment transfer on mountainous landscapes. Here, we address one particular situation, in which the dip angle of the bedrock is subparallel to the topographic slope (termed dip-slope). Such an arrangement results in the potential for large-scale deep-seated landsliding with bedding or jointing acting as glide planes. Hillslopes with the opposite situation (non-dip slope) have no such preconditioning, and denude through detachment and incision. The Val Lumnezia, Eastern Swiss Alps (Graubünden) contains both dip-slope and non-dip slope valley flanks. The topographic slope of the western valley flank parallels Mesozoic metasediments (dip-slope situation) whereas the Bündner schists on the opposite valley dip perpendicular to the topographic slope (non-dip slope situation). We analyse the relationship between upstream size of drainage basins A and channel gradients S. Where channels are graded and actively shape the landscape, channel gradient is directly related to basin area following Flint's (1974) law: S ¼ ksA-? where ks and ? denote the channels steepness and concavity, respectively. The western valley sides are characterized by low ? values ranging from 0.1 to 0.2, and equally display low ks indices of approximately 150 m0.9. Streams on the eastern valley side have higher ? values ranging between 0.3 and 0.8 and higher ks indices reaching 280 m0.9. The high ks and ? values on eastern valley sides are compatible with the rapid dissection of the channel network into landscapes where low hillslope slip rates allow the channel network to actively shape the landscapes. This is in contrast to the western valley sides, where low ks and ? values suggest that the channel network is continually destabilized by rapid deep-seated landsliding. RECONSTRUCTION OF HISTORIC FUNGAL BARCODING DNA PRESERVED IN PERMAFROST
COMMUNITIES
Eva Bellemain. NCB, NHM; University of Oslo, Norway E-mail address: [email protected]
BY