- Email: [email protected]
Pollen–vegetation relationships in SW Iberia: preliminary results and implications for Quaternary research
Abstracts / Quaternary International 279-280 (2012) 9–120
QUATERNARY TEPHROCHRONOLOGY IN THE NORTHERN CIRCUMPACIFIC VOLCANIC ZONE Kaori Aoki. Rissho University, Japan E-mail address: [email protected]
In the Circum-Pacific Volcanic Zone (CPVZ), there are many Quaternary volcanoes, which repeated the explosive eruptions. Large explosions produced widespread tephras which deposited around CPVZ. It is important to reveal the tephrostratigraphy in and around CPVZ, and then to promote it to the precise tephrochronology with the background of radiometric and/or astronomical ages, because it is one of the most valuable stratigraphic timemarkers to correlate the regional palaeoenvironmental records from marine environments, lakes, coasts, mountains, even from ice sheets. North CPVZ surrounds the north Pacific Basin, and accompanies with three big marginal seas, the Sea of Japan, the Sea of Okhotsk, and the Bering Sea. Many tephras are found in pelagic sediments collected around north CPVZ, and thin tephra beds distribute in a zone 990-1290 km wide from CPVZ. Significant factors to transport tephra widely in this area are mainly the seasonal winds and sea ice during winter. In summer, monsoon around the northwest CPVZ area (western Pacific, the Sea of Japan, and the Sea of Okhotsk) blows from southeast to northwest, and wind around the high latitude are of north CPVZ (the Bering Sea and the Alaska region) blows from southwest to northeast. In winter, monsoon around the northwest CPVZ blows from northeast (Siberia region) to southeast (Pacific), and cold winds from Arctic region strongly affect the high latitude area of north CPVZ. Furthermore, winter seasonal sea ice expands in the Sea of Okhotsk, the Bering Sea and the high latitude area of north Pacific today, and it expanded often to the middle latitude area of north Pacific during glacial periods. Nowadays, around northwest CPVZ (Japanese Islands, and sea around them, 30 N-45 N), late Quaternary precise tephrochronology contribute to contract the age scale of various sediments. In future, tephrastratigraphic study in marine sediment around CPVZ will contribute to establish the Circum-Pacific teprochronology. MODEL PARAMETRIC UNCERTAINTY AND THE EVOLUTION OF THE GREENLAND ICE SHEET Patrick J. Applegate. Stockholm University, Sweden E-mail address: [email protected]
We evaluate the effects of highly uncertain model input parameters on the modeled development of the Greenland ice sheet over time, especially during the mid-Holocene. Numerical ice sheet models contain many highly uncertain parameters that are typically held fixed. At minimum, a list of these uncertain parameters includes the positive degree-day factors for ice and snow, the basal heat flux, the flow enhancement factor, and the basal sliding factor. To illustrate the effects that these uncertain parameters can have on ice sheet model paleo-simulations, we perform w250 ice sheet model runs for Greenland, using the SICOPOLIS ice sheet model (http://sicopolis.greveweb.net/) and climate boundary conditions derived from ice cores. Each ensemble member includes different parameter combinations chosen by Latin hypercube sampling, following recent work by Emma Stone and colleagues (The Cryosphere, v. 4, pp. 397417, 2010). We focus on the statistical distribution of modeled ice volumes at 6,000 years before present. At that time, the Greenland ice sheet was likely smaller than it is today, but the ice has hidden or removed evidence showing where the ice margin was. The parameter ranges we investigate are consistent with a wide variety of Greenland ice sheet reconstructions for this critical time slice. We further comment on how this range can be reduced by removing ensemble members that are inconsistent with the modern ice geometry. This work has implications for the use of ice sheet models in reconstructing past ice sheets, as well as the initialization of ice sheet models for projecting future ice sheet behavior. HOLOCENE VEGETATION DYNAMICS AND ABRUPT CLIMATE CHANGES INFERRED FROM LAGUNA DE EL CAÑIZAR SEQUENCE, (IBERIAN RANGE, NE SPAIN) Josu Aranbarri. Instituto Pirenaico de Ecología, Spain E-mail address: [email protected]
23
Western Mediterranean mountains, and particularly those areas in the Iberian Range located in the transition between Mediterranean and Atlantic ecosystems and climates, are very sensitive to regional/global environmental changes, principally those related to humid-dry fluctuations. The Laguna del Cañizar (Teruel province, 40o30’N, 1o18’W) illustrates the Holocene climate and vegetation variability based on pollen and microcharcoal analysis, complemented with sedimentological and geochemical analyses. Preliminary pollen and sediment analyses show three main units: 1) Early Holocene vegetation landscape dominated by conifers with a still important steppe herbaceous component indicating dry and cool climate conditions; 2) Middle Holocene, characterized by the development of a Mediterranean open forest with evergreen and deciduous Quercus as the main arboreal taxa related to an increase in temperatures and moisture availability; 3) late Holocene (until 2700 cal yr BP) with a progressive aridification. This millennial scale vegetation dynamics is in agreement with the main available Iberian Mediterranean sequences. A high resolution sampling in selected intervals has enabled to detect vegetation and hydrological response to centennial-scale abrupt environmental changes such as the 8.2 and 4.2 cal yr BP events. POLLEN–VEGETATION RELATIONSHIPS IN SW IBERIA: PRELIMINARY RESULTS AND IMPLICATIONS FOR QUATERNARY RESEARCH João Araújo. University of the Algarve, Portugal E-mail address: [email protected]
Current approaches to quantitative palaeovegetation reconstruction from Quaternary pollen records are based on pollen productivity estimates (Broström et al. 2008). These estimates compare the percentage pollen composition of surface sediments or moss cushions with the surrounding vegetation. However, in areas where tree cover is sparse, such as Mediterranean savannas, percentage-based estimates are of limited use in reconstructing vegetation cover (Sugita et al. 2010). The Mediterranean region's strong climatic seasonality also limits the distribution of sites where pollen is preserved, potentially biasing pollen–vegetation relationships toward more humid zones. To better reconstruct the palaeovegetation of the Mediterranean region it is preferable to use absolute pollen productivity estimates and sampling locations randomly located in the vegetation. We placed pollen traps in the main vegetation formations of Southern Portugal – Litoral, Barrocal, Serra and Montado – as part of the Pollen Monitoring Programme. In addition to Tauber (1974) traps, we used roofed traps to monitor wind-transported pollen accumulation. We also collected moss samples and quantified vegetation cover abundance in survey rings of exponentially increasing size (van der Knaap et al. 2001). Our results indicate that Pinus and Quercus species have very high pollen productivity, while Arbutus and Pistacia have very low productivity. The latter taxa also have low background values, indicating a predominantly local pollen source. These data should assist in the interpretation of Quaternary pollen records parts of Mediterranean region where these taxa are important. LATE GLACIAL AND HOLOCENE GLACIAL HISTORY OF MONTE SAN LORENZO, CENTRAL PATAGONIA, CHILE Juan Carlos Aravena. Fundación CEQUA, Chile E-mail address: [email protected]
Many glaciated areas around the world underwent periods of renewed glacial activity during the Last Glacial-Interglacial Transition (LGIT), and later, during the Holocene. Even though important efforts have been made, the causes and mechanisms underlying these glacial fluctuations are still being debated. In Southern South America most of the record and understanding of former glacial fluctuations comes from studies of the outlet glaciers from the Patagonian Icefields. This ongoing research will reconstruct Late Glacial and Holocene history of the Monte San Lorenzo area (47 35’S; 7219’W), an isolated granitic massif that supports several small glaciers that were independent of outlet glaciers from the two major icefields. This study focuses on Río Tranquilo glacier, located on the northern flank of Monte San Lorenzo. Geomorphic evidence indicates that during times of major glacial expansion, Río Tranquilo glacier flowed more
QUATERNARY TEPHROCHRONOLOGY IN THE NORTHERN CIRCUMPACIFIC VOLCANIC ZONE Kaori Aoki. Rissho University, Japan E-mail address: [email protected]
In the Circum-Pacific Volcanic Zone (CPVZ), there are many Quaternary volcanoes, which repeated the explosive eruptions. Large explosions produced widespread tephras which deposited around CPVZ. It is important to reveal the tephrostratigraphy in and around CPVZ, and then to promote it to the precise tephrochronology with the background of radiometric and/or astronomical ages, because it is one of the most valuable stratigraphic timemarkers to correlate the regional palaeoenvironmental records from marine environments, lakes, coasts, mountains, even from ice sheets. North CPVZ surrounds the north Pacific Basin, and accompanies with three big marginal seas, the Sea of Japan, the Sea of Okhotsk, and the Bering Sea. Many tephras are found in pelagic sediments collected around north CPVZ, and thin tephra beds distribute in a zone 990-1290 km wide from CPVZ. Significant factors to transport tephra widely in this area are mainly the seasonal winds and sea ice during winter. In summer, monsoon around the northwest CPVZ area (western Pacific, the Sea of Japan, and the Sea of Okhotsk) blows from southeast to northwest, and wind around the high latitude are of north CPVZ (the Bering Sea and the Alaska region) blows from southwest to northeast. In winter, monsoon around the northwest CPVZ blows from northeast (Siberia region) to southeast (Pacific), and cold winds from Arctic region strongly affect the high latitude area of north CPVZ. Furthermore, winter seasonal sea ice expands in the Sea of Okhotsk, the Bering Sea and the high latitude area of north Pacific today, and it expanded often to the middle latitude area of north Pacific during glacial periods. Nowadays, around northwest CPVZ (Japanese Islands, and sea around them, 30 N-45 N), late Quaternary precise tephrochronology contribute to contract the age scale of various sediments. In future, tephrastratigraphic study in marine sediment around CPVZ will contribute to establish the Circum-Pacific teprochronology. MODEL PARAMETRIC UNCERTAINTY AND THE EVOLUTION OF THE GREENLAND ICE SHEET Patrick J. Applegate. Stockholm University, Sweden E-mail address: [email protected]
We evaluate the effects of highly uncertain model input parameters on the modeled development of the Greenland ice sheet over time, especially during the mid-Holocene. Numerical ice sheet models contain many highly uncertain parameters that are typically held fixed. At minimum, a list of these uncertain parameters includes the positive degree-day factors for ice and snow, the basal heat flux, the flow enhancement factor, and the basal sliding factor. To illustrate the effects that these uncertain parameters can have on ice sheet model paleo-simulations, we perform w250 ice sheet model runs for Greenland, using the SICOPOLIS ice sheet model (http://sicopolis.greveweb.net/) and climate boundary conditions derived from ice cores. Each ensemble member includes different parameter combinations chosen by Latin hypercube sampling, following recent work by Emma Stone and colleagues (The Cryosphere, v. 4, pp. 397417, 2010). We focus on the statistical distribution of modeled ice volumes at 6,000 years before present. At that time, the Greenland ice sheet was likely smaller than it is today, but the ice has hidden or removed evidence showing where the ice margin was. The parameter ranges we investigate are consistent with a wide variety of Greenland ice sheet reconstructions for this critical time slice. We further comment on how this range can be reduced by removing ensemble members that are inconsistent with the modern ice geometry. This work has implications for the use of ice sheet models in reconstructing past ice sheets, as well as the initialization of ice sheet models for projecting future ice sheet behavior. HOLOCENE VEGETATION DYNAMICS AND ABRUPT CLIMATE CHANGES INFERRED FROM LAGUNA DE EL CAÑIZAR SEQUENCE, (IBERIAN RANGE, NE SPAIN) Josu Aranbarri. Instituto Pirenaico de Ecología, Spain E-mail address: [email protected]
23
Western Mediterranean mountains, and particularly those areas in the Iberian Range located in the transition between Mediterranean and Atlantic ecosystems and climates, are very sensitive to regional/global environmental changes, principally those related to humid-dry fluctuations. The Laguna del Cañizar (Teruel province, 40o30’N, 1o18’W) illustrates the Holocene climate and vegetation variability based on pollen and microcharcoal analysis, complemented with sedimentological and geochemical analyses. Preliminary pollen and sediment analyses show three main units: 1) Early Holocene vegetation landscape dominated by conifers with a still important steppe herbaceous component indicating dry and cool climate conditions; 2) Middle Holocene, characterized by the development of a Mediterranean open forest with evergreen and deciduous Quercus as the main arboreal taxa related to an increase in temperatures and moisture availability; 3) late Holocene (until 2700 cal yr BP) with a progressive aridification. This millennial scale vegetation dynamics is in agreement with the main available Iberian Mediterranean sequences. A high resolution sampling in selected intervals has enabled to detect vegetation and hydrological response to centennial-scale abrupt environmental changes such as the 8.2 and 4.2 cal yr BP events. POLLEN–VEGETATION RELATIONSHIPS IN SW IBERIA: PRELIMINARY RESULTS AND IMPLICATIONS FOR QUATERNARY RESEARCH João Araújo. University of the Algarve, Portugal E-mail address: [email protected]
Current approaches to quantitative palaeovegetation reconstruction from Quaternary pollen records are based on pollen productivity estimates (Broström et al. 2008). These estimates compare the percentage pollen composition of surface sediments or moss cushions with the surrounding vegetation. However, in areas where tree cover is sparse, such as Mediterranean savannas, percentage-based estimates are of limited use in reconstructing vegetation cover (Sugita et al. 2010). The Mediterranean region's strong climatic seasonality also limits the distribution of sites where pollen is preserved, potentially biasing pollen–vegetation relationships toward more humid zones. To better reconstruct the palaeovegetation of the Mediterranean region it is preferable to use absolute pollen productivity estimates and sampling locations randomly located in the vegetation. We placed pollen traps in the main vegetation formations of Southern Portugal – Litoral, Barrocal, Serra and Montado – as part of the Pollen Monitoring Programme. In addition to Tauber (1974) traps, we used roofed traps to monitor wind-transported pollen accumulation. We also collected moss samples and quantified vegetation cover abundance in survey rings of exponentially increasing size (van der Knaap et al. 2001). Our results indicate that Pinus and Quercus species have very high pollen productivity, while Arbutus and Pistacia have very low productivity. The latter taxa also have low background values, indicating a predominantly local pollen source. These data should assist in the interpretation of Quaternary pollen records parts of Mediterranean region where these taxa are important. LATE GLACIAL AND HOLOCENE GLACIAL HISTORY OF MONTE SAN LORENZO, CENTRAL PATAGONIA, CHILE Juan Carlos Aravena. Fundación CEQUA, Chile E-mail address: [email protected]
Many glaciated areas around the world underwent periods of renewed glacial activity during the Last Glacial-Interglacial Transition (LGIT), and later, during the Holocene. Even though important efforts have been made, the causes and mechanisms underlying these glacial fluctuations are still being debated. In Southern South America most of the record and understanding of former glacial fluctuations comes from studies of the outlet glaciers from the Patagonian Icefields. This ongoing research will reconstruct Late Glacial and Holocene history of the Monte San Lorenzo area (47 35’S; 7219’W), an isolated granitic massif that supports several small glaciers that were independent of outlet glaciers from the two major icefields. This study focuses on Río Tranquilo glacier, located on the northern flank of Monte San Lorenzo. Geomorphic evidence indicates that during times of major glacial expansion, Río Tranquilo glacier flowed more