- Email: [email protected]
Extreme changes in North Atlantic deep convection during deglaciation
Abstracts / Quaternary International 279-280 (2012) 462–565
signal. Terrestrial leaf waxes at ODP Site 1146 in the SCS (19 27.40’N, 116 16.37’E) are derived mainly from the Pearl River, which drains southeastern China, and should reflect the same growing season as the CLP. To reconstruct past ASM strength, we generate a millennial resolution dDlw record from each site. Chinese speleothem records contain strong variability at the precession band from 50-350 ka, and since changes in precession strongly influence the Asian Monsoon, we target this interval for our analyses. For chronology, we correlate the ODP 1146 benthic foraminifera d18O record to the global benthic d18O record, and adjust the age based on a detailed match between the ODP 1146 planktonic d18O record and the Chinese speleothem d18O record. We tie the ODP 1146 chronology into to the Weinan section by matching changes in dDlw. Analysis of the phasing of these records with respect to orbital parameters and other monsoon records (e.g. magnetic susceptibility of the loess section) provides insight into the mechanisms that drive ASM strength. THE DETECTION OF TIPPING POINTS IN CLIMATE SYSTEMS Zoe A. Thomas. University of Exeter, United Kingdom E-mail address: [email protected]
Palaeoresearch has shown that the Earth's climate has undergone many abrupt, non-linear transitions in the past. These so-called ‘tipping points’ are notoriously difficult to predict, particularly in systems as complex as the Earth's climate. However, a number of generic indicators have been shown to precede tipping points in both natural and social systems. Here I will demonstrate that ‘early warning’ signals of impending tipping points can be detected using time-series analysis, in particular through the identification of increased autocorrelation and increased variance. This technique can be applied to both modelled data and ‘real’ data as demonstrated by the range of examples presented here for models and datasets from the North Atlantic (GRIP/NGRIP ice cores and an array of climate models) and Australasian tree rings. The ability to detect these ‘early warning’ signals has clear implications for the interpretation of palaeoenvironmental datasets and model runs as well as future predictions. GLACIERS FROM BRITISH ISLES ENTERED GERMANY BEFORE GLACIERS FROM SKANDINAVIA Karl Thome. University of Bochum, Geol. Inst., Germany E-mail address: [email protected]
Revision of dating deep-sea-core V28-239 (SHACKLETON & OPDYKE 1976, THOME 1997, 2000, 2001, 2003a, 2003b) cleared history of Northern glaciers: In stage 22 (THOME 2010, 2011) the Lower- Rhine-Region was covered by British glaciers, in the stages 16 and 12 by Skandinavian glaciers (THOME 1997). Since 100 years Skandinavian glaciers and their typical drift were researched, while British glaciers are nearly unknown. But British glaciers are marked in the dating record and their traces found in the field: Large scratches similar to ice-scratch-forms in Finnmark and Hudson-Bay are conserved on a reef near the Normandy. In the LowerRhine-Region British glaciers turned river-directions like the Wupper in Wuppertal-Elberfeld (THOME 2010) and deformed layers below the glacier base, visible from 1965 - 1985 in the brown coal-pit "Neurath-Nordfeld", near Duesseldorf (THOME 2011). Where today Elbe-, Ems-, Weser-, Rhine-, Meuse- and Schelde-River end in the sea, sub glacial water below the British Ice-Sheet did erode large holes. During culmination of the RhineGlacier the distance of the glacier-flanks increased from the Sambre-River in the West to the Möhne-River in the East to 360 km, while in the centre the glacier tongue covered the region Bonn-Cologne. From the Meuse plain (in the West of Roermond) a glacier advanced SE, to Düren, from Arnhem a glacier was directed S, to Cologne. Both glaciers developed during final down melting. A GLACIER PALEOCLIMATE PERSPECTIVE FOR THE HOLOCENE FROM THE WORLD'S HIGHEST MOUNTAINS
491
with other proxy data, provide two primary lines of evidence for Holocene climate variability. First, there is strong evidence from paleoclimate records from within and around these glaciers for two widespread and spatially coherent abrupt Holocene events: a large isotopic excursion centered on w5.2 ky BP marking the transition from early Holocene warmth to cooler conditions, and a major dust event between 4.0 and 4.5 ky BP. Both events were concurrent with structural changes in early civilizations. Second, high-resolution ice core stratigraphic records of d18O (temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although they suggest the early Holocene was much warmer at many sites. Tropical ice fields have provided continuous, annually-resolved proxy records of climatic and environmental variability preserved in many measurable parameters, especially oxygen and hydrogen isotopic ratios (d 18O, d D) and net mass balance (accumulation). The remarkable similarity between changes in the highland and coastal cultures of Peru and climate variability in the Andes, especially with regard to precipitation, implies a strong connection between prehistoric human activities and climate in this region. The well-documented ice loss on Quelccaya, Naimona'nyi in the Himalayas, Kilimanjaro in East Africa and the ice fields near Puncak Jaya in Papua, Indonesia, presents a possible analog for glacier response in the tropics during the Holocene. The melting of these ice fields is consistent with model predictions for a vertical amplification of temperature in the tropics. Here these recent changes are examined in the context of the Holocene ice core paleoclimate perspective as recorded in the glaciers on the world's highest mountains LATE QUATERNARY PHYTOGEOGRAPHIC AND CLIMATIC CHANGES IN THE AMERICAN SOUTHWEST Robert Thompson. U.S. Geological Survey, United States E-mail address: [email protected]
In arid and semiarid western North America there are strong gradients in temperature and in the amount and seasonality of precipitation. Distributions of plant species and communities reflect these climatic patterns. Plant macrofossil assemblages from packrat middens in this region provide the basis for reconstruction during the past 25,000 years of species distributions, vegetation communities, and paleoclimates. We compiled data on modern climate and plant distributions and compared this information with past distributions of plant taxa recorded in more than 1000 packrat midden assemblages. To reconstruct past climates, we used the modern analog technique and a weighted mutual climate range method. The midden data indicate that plant species responded individualistically to past climatic changes, and as a result, the composition of plant communities changed in many phases after the end of Full Glacial conditions w15,000 years ago. Presently common species (such as Pinus ponderosa) were uncommon during the Full Glacial, and conversely, species that now have restricted distributions (such as Pinus longaeva) were then widespread. Woodland species lived in the present deserts, retracted their southern and low elevation ranges northward and upslope between 15,000 and 10,000 years ago, but did not reach their present northern ranges until the past 5000 years. Warm deserts were nearly absent prior to 15,000 years ago, expanded by the beginning of the Holocene, but still underwent elevational changes in the past 5000 years. Paleoclimatic changes over the past 25,000 years varied with latitude and elevation. Temperatures during the Full Glacial were 6 C or more colder than today in many parts of the region. Between w15,000 and 12,000 years ago the climate became warmer and wetter, and cool-moist conditions persisted at low elevations until w8000 years ago. Warmer and drier than modern climates occurred across much of the region until after w4000 years ago. EXTREME CHANGES IN NORTH ATLANTIC DEEP CONVECTION DURING DEGLACIATION David Thornalley. Cardiff University, United Kingdom E-mail address: [email protected]
Lonnie Thompson. The Ohio State University, United States E-mail address: [email protected]
Glaciers are among the first responders to global climate change, serving as both indicators and drivers of climate change. Ice core records, coupled
Deep water formation in the North Atlantic by open-ocean convection is an essential component of the overturning circulation of the Atlantic Ocean, which helps regulate global climate. Paleoceanographic studies suggest that deep convection within the North Atlantic was altered during the last
492
Abstracts / Quaternary International 279-280 (2012) 462–565
Ice Age as compared with today. Convection was weaker and/or shallower leading to poorer ventilation of the deep Atlantic and increased storage of dissolved inorganic carbon. Despite the climatic importance of open-ocean deep convection within the North Atlantic, high-resolution evidence for past mode changes has come primarily from stable isotope and nutrient proxy records, yet these proxies are complicated by biological processes and isotopic fractionation during air-sea gas exchange, which may overprint variations caused by water mass changes. Here we use very high resolution water-column radiocarbon reconstructions to examine changes in Northeast (NE) Atlantic convection since the last glacial maximum. Large and abrupt changes in deep water ventilation (ventilation age shifts of 3-5000 years within 100-200 years) were associated with switching between well-ventilated deep water, formed by convection in the NE Atlantic, and incursions of 14C-depleted water, interpreted to be Antarctic Intermediate Water (AAIW), the latter occurring during cold intervals. Significant differences in the convective activity of the NE versus the Northwest (NW) Atlantic have been revealed. Of particular note is the strong reduction in NE Atlantic convection for a sustained interval (the Intra-Allerød Cold Period) beginning w600 years prior to the onset of the Younger Dryas (YD) which has important implications for the cause of the YD. Moreover, we suggest that, despite a strong control on Greenland temperature by NE Atlantic convection, reduced open-ocean convection in both the NW and NE Atlantic is necessary to account for contemporaneous perturbations in atmospheric circulation. TEPHRA IN DEGLACIAL OCEAN SEDIMENTS SOUTH OF ICELAND: STRATIGRAPHY, GEOCHEMISTRY AND OCEANIC RESERVOIR AGES
the lower limb of the AMOC. We have performed sortable silt analysis in 6 cores in the Northwest Atlantic to produce a depth profile of changes in the strength and depth of the lower limb of the AMOC during the Marine Isotope Stage (MIS) 5/4a glacial inception, an interval which contains D-O events 19 and 20 and marks the onset of full glacial conditions. We show that D-O interstadials are associated with relatively fast flow speed between 3-4 km, suggesting a similar deep circulation regime to the modern AMOC. During cold D-O stadial events, shoaling of the DWBC is inferred, with a strong increase in relative flow speed at w2-2.5 km, although the influence of this fast flow extends down to w3-3.5 km. The DWBC shoals even further during MIS 4, which notably includes Heinrich Stadial 6. Inferred flow speed variability at w2 km depth is tightly coupled to Greenland temperature proxies, providing strong evidence that AMOC mode changes played a leading role in abrupt climate variability. In contrast to the shallower sites, the timing of increased relative flow speed at sites > 4 km water depth, associated with a nutrient enriched, corrosive water mass, suggests an additional Antarctic control on abyssal circulation in the Atlantic Ocean. Furthermore, we also examine changes in deep ocean circulation on the Iberian Margin in order to compare the timing and nature of AMOC changes between the Northeast and Northwest Atlantic. RISING NATIONAL GEOPARKS AND GEOHERITAGE CONSERVATION OF CHINA DEVELOPED A NEW RESEARCH FIELD OF THE QUATERNARY SCIENCE Mingzhong Tian. China University of Geosciences, China E-mail address: [email protected]
David Thornalley. Cardiff University, United Kingdom E-mail address: [email protected]
Icelandic tephra layers within deglacial ocean sediment cores from south of Iceland have been detected and their timing with respect to the climate shifts of the last deglaciation constrained. Geochemical analysis of the tephra allowed the likely source volcanic systems to be identified. The previously known Saksunarvatn ash and Vedde ash are recognised and described. Several other major tephra layers are examined: a basaltic eruption(s) of Katla at w8.4 ka; a basaltic eruption of Katla at w12.6 ka; a rhyolitic eruption of Katla at w13.6 ka producing tephra similar in appearance and composition to the Vedde ash; a basaltic eruption of Katla at w14.0 ka; and two basaltic eruptions of Grímsvötn at w14.6 ka and w15.0 ka. Abundant rhyolitic ash with a similar appearance and chemistry to the Vedde ash is found throughout the deglacial interval, predating the Vedde ash by up to 3,000 years, supporting previous suggestions that there were pre-Vedde ash eruptions of rhyolite that may have contributed to North Atlantic Ash Zone 1. This study expands the tephro-stratigraphic framework of the North Atlantic and provides a marine archive in which the timing of tephra layers (useful as isochrons) can be directly compared to major ocean and climate events of the last deglaciation. Furthermore, by correlating tephra layers and abundance changes in the polar foraminifera, Neogloboquadrina pachyderma (sinistral), to equivalent tephra events and inferred abrupt cooling/warming in Greenland ice-cores, contemporaneous 14C dated planktonic foraminifera have been used to estimate changes in the surface radiocarbon reservoir age south of Iceland. Consistent with previous studies, larger surface reservoir ages are calculated during late Heinrich Stadial 1 and the Younger Dryas (w2000 years and w800-1900 years respectively). RAPID CHANGES IN NORTH ATLANTIC DEEP OCEAN CIRCULATION DURING THE MIS 5A/4 GLACIAL INCEPTION
Geoheritage is the valuable geological records for our exploring earth history. Setting up geoparks is a wise way for geoheritage sustainable using to geoheritage conservation, the geoscientifics popularization and fasting the regional economy. In China, 139 national geoparks has been set up since 2001, 22 of which, such as Hexigten Global Geopark, Alxa Desert Global Geopark, are members of GGN (Global Geopark Network) associated by UNESCO; in addition to above mentioned 44 geoheritage have obtained the candidates of China National Geopark in 2009. The Quaternary geology theory and researches in geoparks opens a brand new research area; moreover, it is a new trend of geology service for society. Geoparks is a scientific park where many important Quaternary geology theoretical issues, such as whether the glacier developed in NE China, how formed the Badain Jaran sand mountains as the biggest and the highest dune of the world, are under dispute. In China geoparks are in the scope of Quaternary geology research in addition to few related stratigraphy and paleontology; moreover, practices have proved that it has supported geopark development such as geoheritage appraisal, conservation and planning. Those new research directions of Quaternary geology in geopark include (1) survey and appraisal of geoheritage resources, especially investigation of topographic feature and Quaternary geological phenomena (2) conservation and sustainable using of geoheritage (3) mapping of geopark (4) geopark scientific interpretation (5) scientific popularization of geopark. The Quaternary geology has been playing an active role of geopark construction for instance Hong Kong National Geopark. In the future, several key aspects should be focused on discipline development of the Quaternary geology, and these are (1) methods and theory of the Quaternary geology in geopark (2) adding content of course about geopark base on the original foundation (3) cultivates geopark professional talents who master the Quaternary sciences. EFFECTIVE MOISTURE DURING THE LATE GLACIAL TO HOLOCENE TRANSITION FROM MAINLAND EASTERN AUSTRALIA
David Thornalley. Cardiff University, United Kingdom E-mail address: [email protected]
Changes in the mode of operation of the Atlantic meridional overturning circulation (AMOC) are a leading hypothesis to explain the abrupt climate changes (Dansgaard-Oeschger (D-O) events) recorded in Greenland ice cores during the last glacial period. Existing records which document AMOC mode changes across D-O events are primarily restricted to water mass proxies which cannot detect changes in the strength of the AMOC. Instead, palaeo-current flow speed proxy data (based on the sortable silt mean grain size) can be used to examine directly changes in the strength of
John Tibby. University of Adelaide, Australia E-mail address: [email protected]
The nature of the late glacial transition (LGT), particularly in the Southern Hemisphere, is one of the most interesting, and strongly contested, topics in Quaternary science. In particular, debate has focussed on the presence or absence of a Younger Dryas (YD) signature in the region. Recent papers have cogently argued for both the presence (Andres et al. 2003, EPSL 216) and absence (Barrows et al. 2007, Science 318) of YD influence. Australia, despite spanning a number of climate zones that are influenced by key
signal. Terrestrial leaf waxes at ODP Site 1146 in the SCS (19 27.40’N, 116 16.37’E) are derived mainly from the Pearl River, which drains southeastern China, and should reflect the same growing season as the CLP. To reconstruct past ASM strength, we generate a millennial resolution dDlw record from each site. Chinese speleothem records contain strong variability at the precession band from 50-350 ka, and since changes in precession strongly influence the Asian Monsoon, we target this interval for our analyses. For chronology, we correlate the ODP 1146 benthic foraminifera d18O record to the global benthic d18O record, and adjust the age based on a detailed match between the ODP 1146 planktonic d18O record and the Chinese speleothem d18O record. We tie the ODP 1146 chronology into to the Weinan section by matching changes in dDlw. Analysis of the phasing of these records with respect to orbital parameters and other monsoon records (e.g. magnetic susceptibility of the loess section) provides insight into the mechanisms that drive ASM strength. THE DETECTION OF TIPPING POINTS IN CLIMATE SYSTEMS Zoe A. Thomas. University of Exeter, United Kingdom E-mail address: [email protected]
Palaeoresearch has shown that the Earth's climate has undergone many abrupt, non-linear transitions in the past. These so-called ‘tipping points’ are notoriously difficult to predict, particularly in systems as complex as the Earth's climate. However, a number of generic indicators have been shown to precede tipping points in both natural and social systems. Here I will demonstrate that ‘early warning’ signals of impending tipping points can be detected using time-series analysis, in particular through the identification of increased autocorrelation and increased variance. This technique can be applied to both modelled data and ‘real’ data as demonstrated by the range of examples presented here for models and datasets from the North Atlantic (GRIP/NGRIP ice cores and an array of climate models) and Australasian tree rings. The ability to detect these ‘early warning’ signals has clear implications for the interpretation of palaeoenvironmental datasets and model runs as well as future predictions. GLACIERS FROM BRITISH ISLES ENTERED GERMANY BEFORE GLACIERS FROM SKANDINAVIA Karl Thome. University of Bochum, Geol. Inst., Germany E-mail address: [email protected]
Revision of dating deep-sea-core V28-239 (SHACKLETON & OPDYKE 1976, THOME 1997, 2000, 2001, 2003a, 2003b) cleared history of Northern glaciers: In stage 22 (THOME 2010, 2011) the Lower- Rhine-Region was covered by British glaciers, in the stages 16 and 12 by Skandinavian glaciers (THOME 1997). Since 100 years Skandinavian glaciers and their typical drift were researched, while British glaciers are nearly unknown. But British glaciers are marked in the dating record and their traces found in the field: Large scratches similar to ice-scratch-forms in Finnmark and Hudson-Bay are conserved on a reef near the Normandy. In the LowerRhine-Region British glaciers turned river-directions like the Wupper in Wuppertal-Elberfeld (THOME 2010) and deformed layers below the glacier base, visible from 1965 - 1985 in the brown coal-pit "Neurath-Nordfeld", near Duesseldorf (THOME 2011). Where today Elbe-, Ems-, Weser-, Rhine-, Meuse- and Schelde-River end in the sea, sub glacial water below the British Ice-Sheet did erode large holes. During culmination of the RhineGlacier the distance of the glacier-flanks increased from the Sambre-River in the West to the Möhne-River in the East to 360 km, while in the centre the glacier tongue covered the region Bonn-Cologne. From the Meuse plain (in the West of Roermond) a glacier advanced SE, to Düren, from Arnhem a glacier was directed S, to Cologne. Both glaciers developed during final down melting. A GLACIER PALEOCLIMATE PERSPECTIVE FOR THE HOLOCENE FROM THE WORLD'S HIGHEST MOUNTAINS
491
with other proxy data, provide two primary lines of evidence for Holocene climate variability. First, there is strong evidence from paleoclimate records from within and around these glaciers for two widespread and spatially coherent abrupt Holocene events: a large isotopic excursion centered on w5.2 ky BP marking the transition from early Holocene warmth to cooler conditions, and a major dust event between 4.0 and 4.5 ky BP. Both events were concurrent with structural changes in early civilizations. Second, high-resolution ice core stratigraphic records of d18O (temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although they suggest the early Holocene was much warmer at many sites. Tropical ice fields have provided continuous, annually-resolved proxy records of climatic and environmental variability preserved in many measurable parameters, especially oxygen and hydrogen isotopic ratios (d 18O, d D) and net mass balance (accumulation). The remarkable similarity between changes in the highland and coastal cultures of Peru and climate variability in the Andes, especially with regard to precipitation, implies a strong connection between prehistoric human activities and climate in this region. The well-documented ice loss on Quelccaya, Naimona'nyi in the Himalayas, Kilimanjaro in East Africa and the ice fields near Puncak Jaya in Papua, Indonesia, presents a possible analog for glacier response in the tropics during the Holocene. The melting of these ice fields is consistent with model predictions for a vertical amplification of temperature in the tropics. Here these recent changes are examined in the context of the Holocene ice core paleoclimate perspective as recorded in the glaciers on the world's highest mountains LATE QUATERNARY PHYTOGEOGRAPHIC AND CLIMATIC CHANGES IN THE AMERICAN SOUTHWEST Robert Thompson. U.S. Geological Survey, United States E-mail address: [email protected]
In arid and semiarid western North America there are strong gradients in temperature and in the amount and seasonality of precipitation. Distributions of plant species and communities reflect these climatic patterns. Plant macrofossil assemblages from packrat middens in this region provide the basis for reconstruction during the past 25,000 years of species distributions, vegetation communities, and paleoclimates. We compiled data on modern climate and plant distributions and compared this information with past distributions of plant taxa recorded in more than 1000 packrat midden assemblages. To reconstruct past climates, we used the modern analog technique and a weighted mutual climate range method. The midden data indicate that plant species responded individualistically to past climatic changes, and as a result, the composition of plant communities changed in many phases after the end of Full Glacial conditions w15,000 years ago. Presently common species (such as Pinus ponderosa) were uncommon during the Full Glacial, and conversely, species that now have restricted distributions (such as Pinus longaeva) were then widespread. Woodland species lived in the present deserts, retracted their southern and low elevation ranges northward and upslope between 15,000 and 10,000 years ago, but did not reach their present northern ranges until the past 5000 years. Warm deserts were nearly absent prior to 15,000 years ago, expanded by the beginning of the Holocene, but still underwent elevational changes in the past 5000 years. Paleoclimatic changes over the past 25,000 years varied with latitude and elevation. Temperatures during the Full Glacial were 6 C or more colder than today in many parts of the region. Between w15,000 and 12,000 years ago the climate became warmer and wetter, and cool-moist conditions persisted at low elevations until w8000 years ago. Warmer and drier than modern climates occurred across much of the region until after w4000 years ago. EXTREME CHANGES IN NORTH ATLANTIC DEEP CONVECTION DURING DEGLACIATION David Thornalley. Cardiff University, United Kingdom E-mail address: [email protected]
Lonnie Thompson. The Ohio State University, United States E-mail address: [email protected]
Glaciers are among the first responders to global climate change, serving as both indicators and drivers of climate change. Ice core records, coupled
Deep water formation in the North Atlantic by open-ocean convection is an essential component of the overturning circulation of the Atlantic Ocean, which helps regulate global climate. Paleoceanographic studies suggest that deep convection within the North Atlantic was altered during the last
492
Abstracts / Quaternary International 279-280 (2012) 462–565
Ice Age as compared with today. Convection was weaker and/or shallower leading to poorer ventilation of the deep Atlantic and increased storage of dissolved inorganic carbon. Despite the climatic importance of open-ocean deep convection within the North Atlantic, high-resolution evidence for past mode changes has come primarily from stable isotope and nutrient proxy records, yet these proxies are complicated by biological processes and isotopic fractionation during air-sea gas exchange, which may overprint variations caused by water mass changes. Here we use very high resolution water-column radiocarbon reconstructions to examine changes in Northeast (NE) Atlantic convection since the last glacial maximum. Large and abrupt changes in deep water ventilation (ventilation age shifts of 3-5000 years within 100-200 years) were associated with switching between well-ventilated deep water, formed by convection in the NE Atlantic, and incursions of 14C-depleted water, interpreted to be Antarctic Intermediate Water (AAIW), the latter occurring during cold intervals. Significant differences in the convective activity of the NE versus the Northwest (NW) Atlantic have been revealed. Of particular note is the strong reduction in NE Atlantic convection for a sustained interval (the Intra-Allerød Cold Period) beginning w600 years prior to the onset of the Younger Dryas (YD) which has important implications for the cause of the YD. Moreover, we suggest that, despite a strong control on Greenland temperature by NE Atlantic convection, reduced open-ocean convection in both the NW and NE Atlantic is necessary to account for contemporaneous perturbations in atmospheric circulation. TEPHRA IN DEGLACIAL OCEAN SEDIMENTS SOUTH OF ICELAND: STRATIGRAPHY, GEOCHEMISTRY AND OCEANIC RESERVOIR AGES
the lower limb of the AMOC. We have performed sortable silt analysis in 6 cores in the Northwest Atlantic to produce a depth profile of changes in the strength and depth of the lower limb of the AMOC during the Marine Isotope Stage (MIS) 5/4a glacial inception, an interval which contains D-O events 19 and 20 and marks the onset of full glacial conditions. We show that D-O interstadials are associated with relatively fast flow speed between 3-4 km, suggesting a similar deep circulation regime to the modern AMOC. During cold D-O stadial events, shoaling of the DWBC is inferred, with a strong increase in relative flow speed at w2-2.5 km, although the influence of this fast flow extends down to w3-3.5 km. The DWBC shoals even further during MIS 4, which notably includes Heinrich Stadial 6. Inferred flow speed variability at w2 km depth is tightly coupled to Greenland temperature proxies, providing strong evidence that AMOC mode changes played a leading role in abrupt climate variability. In contrast to the shallower sites, the timing of increased relative flow speed at sites > 4 km water depth, associated with a nutrient enriched, corrosive water mass, suggests an additional Antarctic control on abyssal circulation in the Atlantic Ocean. Furthermore, we also examine changes in deep ocean circulation on the Iberian Margin in order to compare the timing and nature of AMOC changes between the Northeast and Northwest Atlantic. RISING NATIONAL GEOPARKS AND GEOHERITAGE CONSERVATION OF CHINA DEVELOPED A NEW RESEARCH FIELD OF THE QUATERNARY SCIENCE Mingzhong Tian. China University of Geosciences, China E-mail address: [email protected]
David Thornalley. Cardiff University, United Kingdom E-mail address: [email protected]
Icelandic tephra layers within deglacial ocean sediment cores from south of Iceland have been detected and their timing with respect to the climate shifts of the last deglaciation constrained. Geochemical analysis of the tephra allowed the likely source volcanic systems to be identified. The previously known Saksunarvatn ash and Vedde ash are recognised and described. Several other major tephra layers are examined: a basaltic eruption(s) of Katla at w8.4 ka; a basaltic eruption of Katla at w12.6 ka; a rhyolitic eruption of Katla at w13.6 ka producing tephra similar in appearance and composition to the Vedde ash; a basaltic eruption of Katla at w14.0 ka; and two basaltic eruptions of Grímsvötn at w14.6 ka and w15.0 ka. Abundant rhyolitic ash with a similar appearance and chemistry to the Vedde ash is found throughout the deglacial interval, predating the Vedde ash by up to 3,000 years, supporting previous suggestions that there were pre-Vedde ash eruptions of rhyolite that may have contributed to North Atlantic Ash Zone 1. This study expands the tephro-stratigraphic framework of the North Atlantic and provides a marine archive in which the timing of tephra layers (useful as isochrons) can be directly compared to major ocean and climate events of the last deglaciation. Furthermore, by correlating tephra layers and abundance changes in the polar foraminifera, Neogloboquadrina pachyderma (sinistral), to equivalent tephra events and inferred abrupt cooling/warming in Greenland ice-cores, contemporaneous 14C dated planktonic foraminifera have been used to estimate changes in the surface radiocarbon reservoir age south of Iceland. Consistent with previous studies, larger surface reservoir ages are calculated during late Heinrich Stadial 1 and the Younger Dryas (w2000 years and w800-1900 years respectively). RAPID CHANGES IN NORTH ATLANTIC DEEP OCEAN CIRCULATION DURING THE MIS 5A/4 GLACIAL INCEPTION
Geoheritage is the valuable geological records for our exploring earth history. Setting up geoparks is a wise way for geoheritage sustainable using to geoheritage conservation, the geoscientifics popularization and fasting the regional economy. In China, 139 national geoparks has been set up since 2001, 22 of which, such as Hexigten Global Geopark, Alxa Desert Global Geopark, are members of GGN (Global Geopark Network) associated by UNESCO; in addition to above mentioned 44 geoheritage have obtained the candidates of China National Geopark in 2009. The Quaternary geology theory and researches in geoparks opens a brand new research area; moreover, it is a new trend of geology service for society. Geoparks is a scientific park where many important Quaternary geology theoretical issues, such as whether the glacier developed in NE China, how formed the Badain Jaran sand mountains as the biggest and the highest dune of the world, are under dispute. In China geoparks are in the scope of Quaternary geology research in addition to few related stratigraphy and paleontology; moreover, practices have proved that it has supported geopark development such as geoheritage appraisal, conservation and planning. Those new research directions of Quaternary geology in geopark include (1) survey and appraisal of geoheritage resources, especially investigation of topographic feature and Quaternary geological phenomena (2) conservation and sustainable using of geoheritage (3) mapping of geopark (4) geopark scientific interpretation (5) scientific popularization of geopark. The Quaternary geology has been playing an active role of geopark construction for instance Hong Kong National Geopark. In the future, several key aspects should be focused on discipline development of the Quaternary geology, and these are (1) methods and theory of the Quaternary geology in geopark (2) adding content of course about geopark base on the original foundation (3) cultivates geopark professional talents who master the Quaternary sciences. EFFECTIVE MOISTURE DURING THE LATE GLACIAL TO HOLOCENE TRANSITION FROM MAINLAND EASTERN AUSTRALIA
David Thornalley. Cardiff University, United Kingdom E-mail address: [email protected]
Changes in the mode of operation of the Atlantic meridional overturning circulation (AMOC) are a leading hypothesis to explain the abrupt climate changes (Dansgaard-Oeschger (D-O) events) recorded in Greenland ice cores during the last glacial period. Existing records which document AMOC mode changes across D-O events are primarily restricted to water mass proxies which cannot detect changes in the strength of the AMOC. Instead, palaeo-current flow speed proxy data (based on the sortable silt mean grain size) can be used to examine directly changes in the strength of
John Tibby. University of Adelaide, Australia E-mail address: [email protected]
The nature of the late glacial transition (LGT), particularly in the Southern Hemisphere, is one of the most interesting, and strongly contested, topics in Quaternary science. In particular, debate has focussed on the presence or absence of a Younger Dryas (YD) signature in the region. Recent papers have cogently argued for both the presence (Andres et al. 2003, EPSL 216) and absence (Barrows et al. 2007, Science 318) of YD influence. Australia, despite spanning a number of climate zones that are influenced by key