- Email: [email protected]
A Glacier Paleoclimate Perspective for the Holocene from the World's Highest Mountains
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
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