- Email: [email protected]
Identifying accelerations in recent sea level around the United Kingdom
Abstracts / Quaternary International 279-280 (2012) 9–120
are exceptionally well dated and span the last 25ka. We hypothesise that if d18Oice is essentially a temperature proxy, then oxygen isotope records from the lake, driven mainly by hydrological changes, should be negatively related to the ice core record. Given that both isotope records derive from the same precipitation source and the role of precipitation in lake hydrology has been established from other independent proxies, these lake sediment data support the primary interpretation of the ice core record from Kilimanjaro in terms of temperature. However, more detailed changes in the ice-core oxygen isotope record should be viewed with caution given the chronological issues of that core. Comparison of our diatom d18O data with the branched isoprenoid tetraether index (BIT) of cell-wall lipids in soil bacteria also reveal fluctuations in the relative contributions of surface run-off and shallow groundwater supplying the lake at different times during the 25ka period. We suggest that these differences are a result of seasonal variations in rainfall distribution and soil-vegetation adjustments.
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pollen markers. We combine these geological records of sea-level change with nearby tide-gauge records, and show good fit during periods of data overlap and identify hitherto unrecognised fluctuations in UK sea level over the past 500 years. LATE HOLOCENE FLOOD FREQUENCIES AND CLIMATE VARIABILITY IN HIGH MOUNTAIN ENVIRONMENTS INFERRED FROM LÜTSCHINE FAN DELTA SEDIMENTS, SWISS ALPS Marta Baró. University of Barcelona, Department of Physical an, Spain E-mail address: [email protected]
The origins of agriculture or agro-pastoralism have been debated by archaeologists for most of the discipline's history. The debate has been transformed in recent decades by new scientific approaches and new archaeological theorizing, but all too rarely do the science and the social or anthropological archaeology interact robustly with each other. This particularly the case with theorizing about the adaptation, transformation or abandonment of foraging systems and the invention or adoption of systems of agro-pastoralism, or parts of such systems, in response to environmental change (whether climatically- or humanly-influenced) or societal change. In many regions of the world linguistic arguments have added a further intriguing dimension to the mix. In many respects our thinking about foraging-farming transitions remains rooted in an intellectual framework of human ‘progression’ and ‘advancement’ that would not have been unfamiliar to the Victorians. The paper will reflect on these problems, and the potential arising from the more effective integration of philosophies and methodologies, taking case studies in particular from Southwest Asia, China, Europe, and Southeast Asia.
For the last two decades palaeoenvironmental research on catchment dynamics in mountain regions focused usually on continuous sedimentary records from lakes. However, also fluvial archives deposited in specific environments, such as smooth sloping fan deltas with a high water table, can provide high resolution data. This contribution explores the potential of reconstruction of Late Holocene flood variability and the identification of driving forces in the Lütschine catchment. Palaeoenvironmental time series has been established from four high resolution fan delta records using techniques of geochronology, sedimentology, geochemistry (XRF2core scanning) and palynology. Aggradation pulses were inferred from grain-size distribution, TOC and Ca/Ti ratio. During colder climate phases, indicated by the oxygen isotope record GISP2, the elements Si and Al increase whereas Ca decreases. This pattern results from a mayor sediment input of the higher areas dominated by crystalline rocks where glacial, periglacial and paraglacial processes trigger geomorphic processes. During warmer phases the Ca values increase due to the catchment response from lower areas dominated by limestone and marls. These trends evidence a climate control of the fan delta aggradation for selected time windows of the last 4700 years. Major flood cycles were detected from geochemical variations at recurrence intervals from 100 to 150 years: core AA-1 shows 11 pulses from 4700 to 3000 cal BP; core IN-40 records 11 pulses from 2730 to 1300 cal BP; core IN-30 records 7 pulses from 2350 to 1575 cal BP; and profile IN-4 shows 2 pulses from 1800 AD to 2001 AD. In addition, extreme flood events inferred from coarse grained layers vary between 300 and 600 years and correlate predominantly with cooler climate phases. Documentary sources of the last 200 years validate the chronology of the two youngest flood layers dated at 1831 and 1933 AD. The Lütschine flood in 2005 marks the start of a new aggradation pulse.
IDENTIFYING ACCELERATIONS IN RECENT SEA LEVEL AROUND THE UNITED KINGDOM
ALPINE GLACIERS VARIATION AND STRESS STRAIN EFFECT DUE TO DEGLACIATION
FORAGING-FARMING TRANSITIONS IN GLOBAL PERSPECTIVE Graeme Barker. McDonald Institute for Archaeological Research, United Kingdom E-mail address: [email protected]
Natasha Barlow. Durham University, United Kingdom
Carlo Baroni. Dipartimento di Scienze della Terra, Universita'd, Italy
E-mail address: [email protected]
E-mail address: [email protected]
Since the early 1990s, average global sea level has accelerated and is predicted to rise by 18-79 cm by the end of the 21st century. When such accelerations in sea level are synchronous on a regional to global scale they record an unambiguous climatic signal and provide evidence of the sensitivity of the atmosphere–cryosphere–ocean system to climatic change. Testing for synchroneity of sea-level signals in the past provides critical constraints for ocean-climate models that are used to predict future sea-level changes. Careful inspection of the small number of northern European tide gauges with long records suggests that accelerations in sea level have occurred previously between the 19th and 20th centuries, while the much larger and better quality 20th century data set shows that widespread accelerations took place in the years following the 1920s and 1990s, with a deceleration recorded in many places after the 1960s. However, their limited number, distribution and duration preclude efforts to test robustly the climate-sea level hypothesis and establish driving mechanisms responsible for change. One way to address this problem is to develop longer-term records of sea level based on proxy data collected from salt marshes. We present two such records from northwest Scotland (Loch Laxford) and southern England (the Isle of Wight). The work forms part of a wider programme, analysing spatial and temporal trends in sealevel change across the North Atlantic during the last 500 years. From each site, we reconstruct sea level using a combination of diatoms and foraminifera, along with a multi-facetted dating approach combining 210Pb, 137 Cs, local and regional pollution histories, high precision 14C dating and
Recently deglaciated areas (paraglacial areas) are potentially exposed to high geomorphological hazard. In alpine valleys, landlslides (E.g., rock falls and rock avalanches) testify processes of gravity-induced slope deformations which can evolve slope failures as a consequence of stress release affecting the intensely jointed rock masses. For better understanding the relationship between the fluctuations of glaciers and slope evolution, we have practiced an interdisciplinary approach that integrates geomorphological approach with stress-strain numerical modelling. In particular, the topic is the analysis of strain effects induced by stress evolution of slopes under time-depending conditions as a response to variation of glacierization levels since the last glacial maximum. Here we presents the preliminary data obtained in the Val Adamè test area, in the Adamello Group (Central Alps), which hosted in the past the southern tongue of the Adamello Glacier, the widest Italian glacier at present. Through geomorphological and geomechanical field surveys and photointepretation, we have reconstructed glacier extension and thickness of the Adamello Glacier, during the main steps of its glacial history: the Last Glacial Maximum, Late Glacial periods and the maximum Holocene position reached during the Little Ice Age. Different levels of glacierization reported on selected geomorphological sections represent the basis for the numerical modeling, performed through the FDM (Finite Difference Method) code FLAC2D by adopting a sequential approach, i.e. by stepping the slope evolution in agreement with the reconstructed glacial fluctuations.
are exceptionally well dated and span the last 25ka. We hypothesise that if d18Oice is essentially a temperature proxy, then oxygen isotope records from the lake, driven mainly by hydrological changes, should be negatively related to the ice core record. Given that both isotope records derive from the same precipitation source and the role of precipitation in lake hydrology has been established from other independent proxies, these lake sediment data support the primary interpretation of the ice core record from Kilimanjaro in terms of temperature. However, more detailed changes in the ice-core oxygen isotope record should be viewed with caution given the chronological issues of that core. Comparison of our diatom d18O data with the branched isoprenoid tetraether index (BIT) of cell-wall lipids in soil bacteria also reveal fluctuations in the relative contributions of surface run-off and shallow groundwater supplying the lake at different times during the 25ka period. We suggest that these differences are a result of seasonal variations in rainfall distribution and soil-vegetation adjustments.
39
pollen markers. We combine these geological records of sea-level change with nearby tide-gauge records, and show good fit during periods of data overlap and identify hitherto unrecognised fluctuations in UK sea level over the past 500 years. LATE HOLOCENE FLOOD FREQUENCIES AND CLIMATE VARIABILITY IN HIGH MOUNTAIN ENVIRONMENTS INFERRED FROM LÜTSCHINE FAN DELTA SEDIMENTS, SWISS ALPS Marta Baró. University of Barcelona, Department of Physical an, Spain E-mail address: [email protected]
The origins of agriculture or agro-pastoralism have been debated by archaeologists for most of the discipline's history. The debate has been transformed in recent decades by new scientific approaches and new archaeological theorizing, but all too rarely do the science and the social or anthropological archaeology interact robustly with each other. This particularly the case with theorizing about the adaptation, transformation or abandonment of foraging systems and the invention or adoption of systems of agro-pastoralism, or parts of such systems, in response to environmental change (whether climatically- or humanly-influenced) or societal change. In many regions of the world linguistic arguments have added a further intriguing dimension to the mix. In many respects our thinking about foraging-farming transitions remains rooted in an intellectual framework of human ‘progression’ and ‘advancement’ that would not have been unfamiliar to the Victorians. The paper will reflect on these problems, and the potential arising from the more effective integration of philosophies and methodologies, taking case studies in particular from Southwest Asia, China, Europe, and Southeast Asia.
For the last two decades palaeoenvironmental research on catchment dynamics in mountain regions focused usually on continuous sedimentary records from lakes. However, also fluvial archives deposited in specific environments, such as smooth sloping fan deltas with a high water table, can provide high resolution data. This contribution explores the potential of reconstruction of Late Holocene flood variability and the identification of driving forces in the Lütschine catchment. Palaeoenvironmental time series has been established from four high resolution fan delta records using techniques of geochronology, sedimentology, geochemistry (XRF2core scanning) and palynology. Aggradation pulses were inferred from grain-size distribution, TOC and Ca/Ti ratio. During colder climate phases, indicated by the oxygen isotope record GISP2, the elements Si and Al increase whereas Ca decreases. This pattern results from a mayor sediment input of the higher areas dominated by crystalline rocks where glacial, periglacial and paraglacial processes trigger geomorphic processes. During warmer phases the Ca values increase due to the catchment response from lower areas dominated by limestone and marls. These trends evidence a climate control of the fan delta aggradation for selected time windows of the last 4700 years. Major flood cycles were detected from geochemical variations at recurrence intervals from 100 to 150 years: core AA-1 shows 11 pulses from 4700 to 3000 cal BP; core IN-40 records 11 pulses from 2730 to 1300 cal BP; core IN-30 records 7 pulses from 2350 to 1575 cal BP; and profile IN-4 shows 2 pulses from 1800 AD to 2001 AD. In addition, extreme flood events inferred from coarse grained layers vary between 300 and 600 years and correlate predominantly with cooler climate phases. Documentary sources of the last 200 years validate the chronology of the two youngest flood layers dated at 1831 and 1933 AD. The Lütschine flood in 2005 marks the start of a new aggradation pulse.
IDENTIFYING ACCELERATIONS IN RECENT SEA LEVEL AROUND THE UNITED KINGDOM
ALPINE GLACIERS VARIATION AND STRESS STRAIN EFFECT DUE TO DEGLACIATION
FORAGING-FARMING TRANSITIONS IN GLOBAL PERSPECTIVE Graeme Barker. McDonald Institute for Archaeological Research, United Kingdom E-mail address: [email protected]
Natasha Barlow. Durham University, United Kingdom
Carlo Baroni. Dipartimento di Scienze della Terra, Universita'd, Italy
E-mail address: [email protected]
E-mail address: [email protected]
Since the early 1990s, average global sea level has accelerated and is predicted to rise by 18-79 cm by the end of the 21st century. When such accelerations in sea level are synchronous on a regional to global scale they record an unambiguous climatic signal and provide evidence of the sensitivity of the atmosphere–cryosphere–ocean system to climatic change. Testing for synchroneity of sea-level signals in the past provides critical constraints for ocean-climate models that are used to predict future sea-level changes. Careful inspection of the small number of northern European tide gauges with long records suggests that accelerations in sea level have occurred previously between the 19th and 20th centuries, while the much larger and better quality 20th century data set shows that widespread accelerations took place in the years following the 1920s and 1990s, with a deceleration recorded in many places after the 1960s. However, their limited number, distribution and duration preclude efforts to test robustly the climate-sea level hypothesis and establish driving mechanisms responsible for change. One way to address this problem is to develop longer-term records of sea level based on proxy data collected from salt marshes. We present two such records from northwest Scotland (Loch Laxford) and southern England (the Isle of Wight). The work forms part of a wider programme, analysing spatial and temporal trends in sealevel change across the North Atlantic during the last 500 years. From each site, we reconstruct sea level using a combination of diatoms and foraminifera, along with a multi-facetted dating approach combining 210Pb, 137 Cs, local and regional pollution histories, high precision 14C dating and
Recently deglaciated areas (paraglacial areas) are potentially exposed to high geomorphological hazard. In alpine valleys, landlslides (E.g., rock falls and rock avalanches) testify processes of gravity-induced slope deformations which can evolve slope failures as a consequence of stress release affecting the intensely jointed rock masses. For better understanding the relationship between the fluctuations of glaciers and slope evolution, we have practiced an interdisciplinary approach that integrates geomorphological approach with stress-strain numerical modelling. In particular, the topic is the analysis of strain effects induced by stress evolution of slopes under time-depending conditions as a response to variation of glacierization levels since the last glacial maximum. Here we presents the preliminary data obtained in the Val Adamè test area, in the Adamello Group (Central Alps), which hosted in the past the southern tongue of the Adamello Glacier, the widest Italian glacier at present. Through geomorphological and geomechanical field surveys and photointepretation, we have reconstructed glacier extension and thickness of the Adamello Glacier, during the main steps of its glacial history: the Last Glacial Maximum, Late Glacial periods and the maximum Holocene position reached during the Little Ice Age. Different levels of glacierization reported on selected geomorphological sections represent the basis for the numerical modeling, performed through the FDM (Finite Difference Method) code FLAC2D by adopting a sequential approach, i.e. by stepping the slope evolution in agreement with the reconstructed glacial fluctuations.