bluuebunny/crossref_metadata_2025 huggingface dataset:
Global surface air temperature variations during the twentieth century: Part 2 , implications for large-scale high-frequency palaeoclimatic studies
Authors: Briffa K.R. , Jones P.D.
Published: November 2007

This paper is the second of a two-part series analysing details of regional, hemispheric and global temperature change during the twentieth century. Based on the grid box data described in Part 1 we present global maps of the strength of regional temperature coherence measured in terms of the correlation decay length for both annual and seasonal mean data. Correlation decay lengths are generally higher for annual rather than seasonal data; higher in the Southern compared to the Northern Hemisphere; and consistently higher over the oceans, particularly the Indian and central north Pacific oceans. Spatial coherence is relatively low in all seasons over the mid to high latitudes of the Northern Hemisphere and especially low in summer over the northern North Atlantic region.

We also describe selected regional temperature series and examine the similarities between these and hemispheric mean data, placing emphasis on the nature of the relationships in different seasons. The Equatorial Indian and Atlantic oceans appear to be the best regional proxies for representing global mean temperatures. Temperature change in regions bordering the northern North Atlantic are less representative of hemisphere mean data, particularly in summer.

The implications of these results for the large-scale interpretation of high-frequency palaeoclimate proxies are discussed. Strictly, given the length of the instrumental data, our results apply to temperature variability on timescales up to, at most, 50 years. Traditional inferences on global mean temperature change based on regional proxies originating around the margins of the northern North Atlantic must be viewed with some caution. Information on temperature change over the oceans, especially the tropical oceans, is an important prerequisite for accurate portrayal of global mean change. Care must be taken when integrating the evidence of different climate proxies to respect the seasonality of the response. Warm-season temperatures are most atypical of the various seasonal averages, especially in the Northern Hemisphere. Inferring annual temperature change on the basis of summer-responsive data is highly questionable.
Holocene moraine chronology, Spitsbergen, Svalbard: lichenometric evidence for multiple Neoglacial advances in the Arctic
Authors: Werner A.
Published: November 2007

Late Holocene (Neoglacial) moraines occurring within 1 or 2 km of present glacier margins are prominent features in the forefields of Spitsbergen glaciers. 'Little Ice Age' moraines are typically the most extensive and best preserved; moraines of older Holocene advances are much less common. Where observed, older moraines occur as moraine remnants and provide irrefutable evidence of earlier Neoglacial advances. The fragmentary moraine record indicates two 'Little Ice Age' advances and two older Neoglacial advances.

Lichenometry provides calibrated ages for periods of moraine stabilization. The oldest moraines stabilized by ca. 1500 years ago, and a second group of moraines stabilized by ca. 1000 years ago. 'Little Ice Age' moraines were deposited during two periods: an early group of moraines stabilized ca. 650 years ago and a later group during the last several centuries. The proposed moraine chronology compares well with other proxy climate records on Spitsbergen and with moraine records from areas bordering the Norwegian-Greenland Sea.
Soil exploitation and early agriculture in northern Italy
Authors: Biagi Paolo , Cremaschi Mauro , Nisbet Renato
Published: November 2007

The current state of research on the environmental impact of early agriculture in northern Italy is reported with particular reference to the region between the Emilian Apennines and the Lombard Pre-Alps. Cultural and palaeoenvironmental evidence supports the view that the location of Neolithic settlements largely depended on the distribution of soils suitable for agriculture. This is particularly evident for the late-seventh millennium BP (Fiorano) and the sixth millennium BP (Square Mouthed Pottery) sites, which are located on well drained, silt-clay-loams.
Mid- to late-Holocene carbon balance in Arctic Alaska and its implications for future global warming
Authors: Marion Giles M. , Oechel Walter C.
Published: November 2007

In the event of global warming, there is considerable uncertainty whether northern ecosystems will act as an atmospheric CO2 sink or source. This study examines Holocene rates of soil carbon accumulation along a latitudinal transect in northern Alaska as an analogue for future change in the Arctic. Rates of carbon accumulation during the colder late-Holocene (4800-400 BP) varied from 1.2 to 3.5 g C m-2 yr-1. During the warmer mid-Holocene (6900-4800 BP), the rate of carbon accumulation at Prudhoe Bay was significantly higher (6.7 g C m-2 yr-1) than during the colder late-Holocene (1.2 g C m-2 yc-1). Both paleoclimatic and latitudinal trends support the argument that long-term carbon storage in far-northern ecosystems (arctic and subarctic) increases with increasing temperature. This suggests that far-northern ecosystems will, over the long term (centuries to millenia), continue to act as a small sink (0.034-0.070 Gt yr-1) for atmospheric CO2 following global warming, which will provide a small negative feedback on global warming. However, recent studies also suggest the possibility that over the short term (decades to centuries), overall carbon loss from the Arctic might also provide a strong positive feedback on global warming.
The temporal significance of transitions from melting to calving termini at glaciers in the central Southern Alps of New Zealand
Authors: Kirkbride Martin P.
Published: November 2007

Termini of valley glaciers in the central Southern Alps are undergoing a three-phase sequence of retreat that began in the 1950s. An initial phase of melting and slow downwasting under thickening supraglacial debris mantles is associated with stationary or slowly retreating termini. This is followed by a transitional phase of disruption of insulating debris mantles allowing the rapid growth of shallow thermokarst lakes, the shape and location of which vary according to glacier gradient and marginal topography. A third phase of rapid calving retreat of ice cliffs into deepening proglacial lakes develops from the transitional phase. At no stage are terminal responses simply related to climate. Present transitions to calving retreat are related to the morphology of glacier termini, particularly to large outwash heads. Landform evidence indicates that similar calving phases do not appear to have occurred since Late Pleistocene deglaciation, so that present changes to glacier termini are of great significance in the context of the whole Holocene. At millennial timescales, the melting-calving transition is effectively instantaneous and represents a sharp threshold heralding rapid deglaciation. The commencement of calving is imminent at the stationary terminus of Tasman Glacier which will soon retreat rapidly as a result.
Holocene fluctuations of lake levels in the French Jura and sub-Alpine ranges, and their implications for past general circulation patterns
Authors: Magny Michel
Published: November 2007

Temperature and precipitation variations reflected in lake-level fluctuations in the French Jura and Pre-Alps during the last nine millennia are qualitatively assessed by reference to: (1) climatic oscillations reconstructed in the Alps; and (2) modern processes behind Alpine tree-limit variations. The summer season - and mainly the late summer - appears to have a deterministic impact on the Holocene environment. Correlations between palaeoclimatic proxy data recorded in the north Atlantic area from high and middle latitudes, and climatic dynamics illustrated by the 'Little Ice Age' and the recent warming, suggest: (1) the existence of climatic oscillations due to varying solar activity superimposed on larger plurimillennial climatic trends; and (2) that these minor climatic phases correspond with two main types of general circulation pattern alternating over western Europe during the last six millennia. The climatic deteriorations correspond with cooling at high latitudes inducing a stronger thermal gradient and an enhanced cyclonicity over western Europe (and vice versa during climate improvement phases).
Environmental change in montane southwest Uganda: a pollen record for the Holocene from Ahakagyezi Swamp
Authors: Taylor D.M.
Published: November 2007

The environmental history of montane southwest Uganda over the last c. 12 300 years is described using data from a 22.84-m long core of sediment from Ahakagyezi Swamp, Rukiga Highlands. These data include plant microfossils and macrofossils, charcoal and nine radiocarbon dates. According to evidence from plant fossils and radiocarbon dates, vegetation in the Ahakagyezi catchment was very different to the expected climax today until c. 10500 BP. The surface of the swamp was dominated by sedges, whilst the adjacent hillsides were largely devoid of trees. Changes in pollen suggest that a form of dry montane scrub was replaced by moist, lower montane forest from c. 11000BP. Subsequent fluctuations in pollen indicate that, once established, the composition of moist, lower montane forest varied during the Holocene and that unreversed forest reduction commenced in the Ahakagyezi catchment at c. 800 BP. On the surface of the swamp itself Syzygium-dominated swamp forest increased in extent from c. 5800 BP, and more rapidly from c. 3100 BP, before beginning a decline c. 1300 BP. The most likely reason for the presence of montane scrub in the catchment, rather than moist lower montane forest, prior to c. 11000 BP (i.e., a period that is believed to precede agricultural activity in the region) is a climate somewhat drier than the present. The spread of moist lower montane forest is believed to indicate the onset of climatic conditions broadly similar to those of today (i.e., the beginning of the Holocene). The causes of Holocene changes in forest composition and extent are most probably due to one or a combination of the following factors: natural succession; regional climate change; and the impact of human activity.
Micromorphological evidence of soil deterioration since the mid-Holocene at archaeological sites in Brittany, France
Authors: Gebhardt Anne
Published: November 2007

This paper presents data on the evolution of agricultural landscapes in Brittany from the end of the Atlantic chronozone to the Mediaeval period (450 BC-AD 1600), using soil micromorphology in a multidisciplinary palaeoenvironmental context. Buried soils and unburied sediments associated with archaeological structures in Brittany were examined. The study of well dated archaeological buried soils gives new information on the way the landscape of Brittany was affected by human impact, which has disturbed the Atlantic soil balance since the start of the Neolithic and has been a major factor in soil acidification in Brittany. Deforestation of primary woodland occurred however, over a long period. The analysis of down-slope sediment accumulation shows that colluviation of loam-rich soils was stimulated by deforestation and agriculture. Micromorphological study of archaeological ditches shows that some microscopical features are difficult to interpret in unburied conditions, especially in modern cultivated contexts, but that this can be done after comparison with experimentally reconstructed (or similar traditional) structures. Such results help our understanding of the history of bocage (land enclosure).
Varve formation and the climatic record in an Alpine proglacial lake: calibrating annually- laminated sediments against hydrological and meteorological data
Authors: Leemann Andreas , Niessen Frank
Published: November 2007

Processes leading to the formation of varves in proglacial Oeschinensee (Switzerland) are investigated. The aim is to calibrate annually-laminated sediments of the last three decades against hydrological and meteorological instrumental data. Results from water samples and sediment traps show that the suspended sediment in the lake is mainly distributed by underflows during the time of the largest sediment input from May to mid-August. This leads to the deposition of the basal silt layers of the varves. Settling of fine-grained suspension from interflows dominates sedimentation between August and October, forming the final layer of fine-grained material at the end of the annual deposition cycle. The median grain-size at the top of the varves is always below 5 μm and thus defines the varve boundaries. Varve thickness is a function of the annual discharge of suspended load from the catchment. This is supported by evidence from hydrological and meteorological data compiled for a glaciated catchment (Loetschental) adjacent to Oeschinensee. Suspended sediment discharge is related to runoff which in turn is correlated with summer air temperature (correlation coefficients 0.66 and 0.70 respectively). Between AD 1962 and 1982, annual thicknesses of the Oeschinensee varve record showed a positive correlation with the average summer air temperature of the region (correlation coefficient 0.44).
Holocene pollen spectra from Oyo, northwestern Sudan: problems of interpretation in a hyperarid environment
Authors: Ritchie J.C.
Published: November 2007

The Oyo site is in the hyperarid core of the eastern Sahara. A 3.4 m core of lake sediment yielded a continuous pollen record for the period 9 to 4.5 ka BP. The lower, regularly-laminated carbonate sediments (9-6 ka) show a pollen assemblage with the tropical taxa dominated by plants of Sudanian and Sahelian affinity, and the local taxa dominated by grass and Typha. The upper sediments (6-4.5 ka), grading from laminated carbonates to coarsely bedded and massive layers with aeolian sands, have reduced frequencies of Sudanian pollen taxa, and increases in Saharan types and sedge-dominated local pollen spectra. A possible vegetational reconstruction is a mosaic of savanna woodlands associated with groundwater-supported lakes and marshes between 9 and 6 ka BP, and sparser cover of steppe and semidesert communities between 6 and 4.5 ka BP as water tables dropped and hyperarid conditions were restored.
Radiocarbon AMS dating of Holocene wolf (Canis lupus) remains from Greenland
Authors: Bennike Ole , Meldgaard Morten , Heinemeier Jan , Rud Niels
Published: November 2007

Radiocarbon AMS dating of seven polar wolf (Canis lupus) remains from east and north Greenland and one from Ellesmere Island document the presence of this large carnivore in Greenland at around 6800, 1600, 800 and 500 BP, corresponding to calibrated ages of 5620 BC, AD 530, AD 1260 and AD 1420. Three of the remains yielded modem ages. These results demonstrate the presence of the wolf in Greenland since the early mid-Holocene and it is argued that it was probably present during most of the Holocene. The dates are important for a proper understanding of the faunal and environmental history of Greenland.
Non-climatic factors and the environmental impact of volcanic volatiles: implications of the Laki fissure eruption of AD 1783
Authors: Grattan John , Charman Daniel J.
Published: November 2007

Studies of the potential of Icelandic volcanic eruptions to modify the environment of the British Isles have primarily concentrated on the degree of induced climate change, but models and temperature records suggest that the scale of such change may have been minimal. As a result it is difficult to account for change in the palaeoenvironmental and archaeological records, in response to a volcanic eruption, by invoking climate change alone. An additional mechanism is proposed by which Icelandic volcanic eruptions transport and deposit environmentally-significant levels of acid volatiles and halogens. Contemporary documentary evidence indicates a widespread dry, smoky haze throughout western Europe during the Laki fissure eruption in the summer of AD 1783, indicative of the presence of volcanically generated gases in the lower atmosphere. Severe damage to crops and trees occurred in a number of locations in Britain and western Europe, the descriptions of which are consistent with the impact of acid deposition. It is suggested that the deposition of acids and halogens emitted in Icelandic volcanic eruptions may be more significant than climatic perturbations for ecosystems in the British Isles.
The impact of the Romans on the environment of northern England: pollen data from three sites close to Hadrian's Wall
Authors: Dumayne L. , Barber K.E.
Published: November 2007

Pollen diagrams from three sites along Hadrian's Wall in northern England are used to assess human impact on vegetation during the later Holocene, but with particular reference to the Roman period. In the light of available archaeological evidence, the radiocarbon-dated diagrams indicate that at Walton Moss and Glasson Moss, Cumbria, a period of woodland removal began during the Iron Age, continuing and accelerating during the Roman occupation. At Fozy Moss there was little human impact on vegetation in the area around the moss until the time of the Roman occupation when massive clearance resulted in an almost completely deforested landscape. These results are discussed against the background of previously published pollen diagrams from northern Britain.
Holocene lake-level changes in the Fennoscandian tree-line region, western Finnish Lapland: diatom and cladoceran evidence
Authors: Hyvärinen Hannu , Alhonen Pentti
Published: November 2007

Lithostratigraphical, diatom and cladoceran evidence were used to demonstrate Holocene lake-level changes in two closed-basin lakes in western Finnish Lapland, north of the coniferous tree- line. The lake levels were significantly lower than present in early to mid-Holocene times, from about 8000 until about 4000BP, after which they rose to the present level. The changes are believed to be climatically controlled and regionally representative. The proposed mid-Holocene dryness in Lapland contrasts with the evidence from southern Sweden and Finland, where past lake levels indicate humid conditions during much of the mid-Holocene (Atlantic) time.
The Neolithic transition - fact or fiction? Palaeoecological evidence from the Balkans
Authors: Willis K.J. , Bennett K.D.
Published: November 2007

Extensive study of the spread of agriculture from the near east to northern Europe by archaeologists has failed to establish the extent to which early Neolithic farmers had an impact upon the landscape. Two current theories for how early farming spread from southeast to northern Europe (population expansion resulting in the surplus population moving northwards, and cultural migration of technologies and crops without a large population movement) are examined in the light of palaeoeco logical evidence for the temporal and spatial scale of the development of extensive agriculture. Both theories assume on a time-transgressive spread starting at 10000BP in the near east, reaching the Balkans at 8000-6000 BP, and northern Europe at 5000-4000 BP. The model of the so-called 'Neolithic transition' is fully incorporated into the archaeological literature and has further been used to suggest the spread of the Indo-European language. However, evidence from Holocene palaeoecological records of the Balkans suggests that the time-transgressive explanation for the spread of agriculture is unsatisfactory. The impact of agriculture upon the landscape did not follow a time-transgressive spread and did not occur until at least 6000BP, considerably later than either of the prevailing theories. Ideas about how, why, and when the impact took place need revision.
Stable isotope record of palaeoclimatic change in a British Holocene tufa
Authors: Andrews J.E. , Pedley H.M. , Dennis P.F.
Published: November 2007

A 9.5 m long, continuous core through Holocene tufa deposits in Derbyshire, UK, was analysed for oxygen and carbon stable isotope variations with a view to palaeoclimatic and palaeoenvir onmental interpretation. The depositional environment of the tufa is well understood and dated using 14C and biostratigraphy. It is argued that smooth variations of up to 1‰ in δ18O of the tufa calcites are caused by changes in the isotopic composition of regional rainfall, which in turn were caused mainly by changes in air temperature (palaeoclimate). In general, lower δ13C values for calcite correspond with higher δ18O values, suggesting a stronger component of soil-derived carbon during warmer climatic phases. A stable isotope approach to reading terrestrial palaeoclimatic records is of widespread application to Holocene and older tufa deposits which are common in carbonate bedrock regions.
Radiocarbon-dated Holocene pollen and ostracod sequences from barrage tufa- dammed fluvial systems in the White Peak, Derbyshire, UK
Authors: Taylor David M. , Griffiths Huw I. , Pedley H. Martyn , Prince Iain
Published: November 2007

Sedimentary evidence, in the form of pollen, ostracod and radiocarbon-age data from three barrage tufa-dammed systems in the White Peak area of Derbyshire, is used to reconstruct the region's environmental history from 10000 to 4000BP. The data highlight the useful role that such fluvial systems can play in environmental reconstructions, through their ability to act as sumps for a wide range of proxy indicators, in a region where environmental change during the Holocene period has been relatively poorly documented. Pollen data suggest that the period of climatic amelioration following the last (Devensian) glaciation facilitated the spread of thermophilous woodland taxa on the White Peak, although there are some indications that the first immigrant trees were not established until a relatively late date. Forest clearance commencing during the mid-Holocene, and possibly as early as the late Mesolithic, was most probably to provide land for grazing, and was virtually complete by 4000BP. Ostracod data reveal fluctuations in discharge of the River Lathkill draining the White Peak, particularly lower flow rates after 7400 BP, which are difficult to explain simply in terms of climate change.
Late-Holocene shoreline changes related to palaeoseismic events in the Ionian Islands, Greece
Authors: Pirazzoli P.A. , Stiros S.C. , Laborel J. , Laborel-Deguen F. , Arnold M. , Papageorgiou S. , Morhangel C.
Published: November 2007

A systematic multidisciplinary survey on the coasts of the Ionian Islands, founded on 26 new radiocarbon accelerator mass spectrography (AMS) dates, has revealed the occurrence of sectors which were uplifted (seismo)tectonically during the late Holocene. In Corfu, two uplift movements of about 0.8m each took place in the central part of the island: one of them around 790-400 cal. BC, and also at a more recent, undetermined date. In Levkas, up-and-down tectonic movements of metric order governed late-Holocene relative sea-level changes, at least in the northern part of the island; submergence of at least 2.5 m occurred since 2400 years ago, with a possible spasmodic subsidence around cal. AD 500-700. In Cephalonia, two vertical displacements affected most of the island, around cal. AD 350-710 and in AD 1953; both movements resulted in uplift in the southeastern part of the island. Submergence seems to predominate round Ithaca. Lastly, in Zante, clear evidence of a Holocene crustal block movement is limited to the southeastern peninsula, where an uplift of 0.95 ± 0.15 m took place, probably coseism ically, around the period cal. AD 200-500. The time ranges of uplift in Cephalonia and Zante, and of possible subsidence in Levkas, correspond with a period of regional tectonic paroxysm, between the middle of the fourth century AD and the middle of the sixth century AD; this has already been documented in several areas of the eastern Mediterranean, notably in the Gulf of Corinth, the southern Hellenic arc, Turkey, Cyprus, the Lebanon and Syria.
Holocene evolution of a lowland Scottish landscape: Kirkpatrick Fleming. Part I, peat- and pollen-stratigraphic evidence for raised moss development and climatic change
Authors: Tipping Richard
Published: November 2007

This series of papers addresses the principal natural and anthropogenic environmental changes that have transformed a typical lowland Scottish landscape during the Holocene. Sediment- and pollen- stratigraphic techniques, together with radiocarbon dating, are applied in this paper to the stratigraphy of a raised bog at Burnfoothill Moss, eastern Dumfriesshire, to deduce changes in groundwater levels within the bog, and by inference, changes in effective precipitation. The basin, initially a shallow pond, was rapidly colonized by fen peat at 9600 BP, possibly during a phase of drier climate, which ended at c. 8700 BP. Short-lived fluctuations in bog-surface wetness are identified before a major change to a wetter bog surface at around 7700 cal. BP, representing the transformation from fen peat to raised moss. Anthropogenic interference with surrounding woodland is believed to have destabilized the water balance within the peat. Drier bog-surface conditions occur at c. 6700 cal. BP, and a shift to a wetter climate at around 5250 cal. BP, but a perhaps more substantial wet shift is recorded at c. 4000 cal. BP. At c. 1900 cal. BP a dry climate shift is recognized, ending at c. 1200 cal. BP. Slightly prior to the 'Little Ice Age', represented by a very wet phase before c. 400 cal. BP, is a dry period between c. 600 and 400 cal. BP.
Seven tephra isochrones in Scotland
Authors: Dugmore Andrew J. , Larsen Gu∂rún , Newton Anthony J.
Published: November 2007

This paper reports the presence and geochemical characteristics of seven separate tephras in Scotland that fell in AD 1510, and about 450 BP, 2100 BP, 3600 BP, 3830 BP, 5600 BP and around 6000 BP. The results come from 14 peat bogs spread throughout the Highlands and Islands where 26 tephra deposits have been characterized using over 400 grain-discrete electron-probe micro-analysis. Firstly, tephras are identified and defined by major element characteristics at a reference site. Secondly, tephras are linked between sites on the basis of geochemistry, and dated. Informal names, based on British sites, are suggested for tephras not yet linked to precise sources in Iceland. Despite some apparent variation in colour, all analysed grains in these seven deposits are silicic or intermediate in composition (SiO2 >57%). This phenomenon does not appear to be an artifact of preservation for two reasons. First, small (<40 μm) basic glass shards in peat bogs in northern Iceland are found to have undergone minimal alteration over the last 6000 years; so it is unlikely that basic glass of this age or less in British peat bogs has dissolved since its deposition. Second, tests have shown that the extraction technique used to remove tephra from peat does not significantly alter the mass or particle-size distribution of these glass shards. This study stresses the advantage of using a geographical range of sites to build a regional tephrochro nology in distal areas of volcanic fallout, because there is frequently great local variability in tephra distribution. In the five years since tephras were first identified in northern Britain it has become apparent that tephrochronology can make significant and exciting new contributions to environmental studies throughout this region.
Sea-surface temperature fluctuations during the Holocene off the south coast of Africa: implications for terrestrial climate and rainfall
Authors: Cohen A.L. , Tyson P.D.
Published: November 2007

Models of southern African palaeoclimate implicate surface atmospheric circulation anoma lies as forcing large-scale changes during the Late Quaternary. The available proxy data are insufficient to test the models since they provide information about temperature and rainfall rather than surface circulation. A conceptual model is proposed which links coastal ocean temperatures with atmospheric circulation and allows a history of surface circulation to be inferred from sea-temperature data. A Holocene sea-surface temperature (SST) record was constructed by measuring the oxygen isotope composition of marine mollusc shells preserved in an archaeological cave deposit on the coast of the eastern Agulhas Bank, southern Africa. Radiocarbon-dating of individual shells allowed definition of the timing and timespan of events in the record. By serially sampling along the growth axis of each shell, information was obtained about intra-annual variability as well as millennial-scale trends. During the early Holocene, the sea surface on the eastern Agulhas Bank was colder than it is at present. Maximum summer and winter temperatures obtained 5800 years ago, exceeding by more than 2°C those recorded in the region today during non-El Nino years. On average, temperatures remained high for the following 1500 years but dropped again during the Late Holocene. At 650 BP, at the start of the 'Little Ice Age' in southern Africa, the surface waters on the eastern Agulhas Bank were colder during both winter and summer.

Millennial-scale variability was attributed to the same processes which force interannual SST anomalies in the region today, namely surface winds and the Agulhas Current. Negative temperature anomalies were probably associated with higher volume transport of the Agulhas Current, which forces upwelling over the shelf edge, and with increased prevalence of easterly winds, which drive coastal upwelling. In contrast, a northward displacement of the westerly wind belt, weakening of the anticyclonic circulation and thus suppression of both coastal and shelf-edge upwelling may have been responsible for positive temperature anomalies recorded during the mid-Holocene. The conceptual model predicts that negative SST anomalies are associated with wetter conditions over the southern African interior, whereas warm-water anomalies are associated with dry conditions.
The role of climate in landscape morphogenesis since the Bronze Age in Provence, southeastern France
Authors: Provansal M.
Published: November 2007

Between the Rhône and the Massif des Maures, geomorphological research, radiocarbon dating and archaeological excavation has revealed synchronous variations in morphological evolution produced by changes in climate. Following one or more torrential protohistoric phases, the later Iron Age and Gallo-Roman civilizations were marked by a reduction in runoff from slopes and a lowering of the water level in marshy areas. This was probably due to drier climatic fluctuations linked to a more even seasonal rainfall distribution. The early Middle Ages and the beginning of Modem Times correspond to a renewed increase in rainfall, the erosive effects of which have been exacerbated by human activity.
Mapping Holocene upwelling in the eastern equatorial Pacific using Radiolaria
Authors: Haslett Simon K.
Published: November 2007

Recently, an assemblage of Radiolaria characteristic of upwelling has been described from the Peru Current, Oman Margin, and Somalian Gyre regions, and subsequently from the eastern tropical Atlantic. An Upwelling Radiolarian Index (URI) has been developed to monitor temporal variations in upwelling systems. In the present study, the URI has been adapted to map spatial variation in the eastern equatorial Pacific upwelling system using Holocene core-top samples. The results indicate a good correlation between the Holocene URI and the present day thermocline depth, confirming that the component species of the URI are indeed characteristic of upwelling. The URI is a potent tool for reconstructing and monitoring upwelling systems in the geological record, either in time-slice studies over wide geographical areas, or in time-series analysis at one or more sites. Its application is limited only by the availability of well-dated cores, and restrictions by the stratigraphical ranges of the URI component species.
Biomass burning recorded in the GISP2 ice core: a record from eastern Canada?
Authors: Taylor K.C. , Mayewski P.A. , Twickler M.S. , Whitlow S.I.
Published: November 2007

Combustion byproducts from biomass burning are preserved in annually stratified layers in the Greenland ice sheet. Electrical conductivity (ECM) and ammonium records from the GISP2 ice core in central Greenland have been used to develop a 6000-year record of biomass burning. Although there is some uncer tainty regarding the source area for the combustion byproducts, it is likely that the majority of the material originates in eastern Canada. Time periods of high biomass-burning activity occurred in 0-150 BP, 350-750 BP, and 5000 to >6000 BP. The period 1150-3250 BP is characterized by moderately elevated levels of biomass-burning activity. These periods are associated with drier conditions. The 5000 to >6000 BP period of high biomass-burning activity may also be related to forest successional sequences following the removal of the Laurentide ice sheet. This paper explains how ice cores can be used to develop records of biomass burning and offers suggestions for future studies.
Regional aridity in North America during the middle Holocene
Authors: Dean Walter E. , Ahlbrandt Thomas S. , Anderson Roger Y. , Platt Bradbury J.
Published: November 2007

Increased aridity throughout the Great Plains and Rocky Mountain region during the middle Holo cene has been documented from pollen records, aeolian proxy variables in lake cores, and active sand dune migration. Varve calibration provided by a continuously varved record of the Holocene from a core from Elk Lake, northwestern Minnesota, shows that the influx of aeolian clastic material increased beginning about 8 ka and ended about 3.8 ka, with peak aeolian activity at about 6 ka. If aeolian influx to Elk Lake corresponds in time to aeolian influx in other lakes and to maximum dune activity in Minnesota dune fields, then the varve calibration in Elk Lake provides precise time calibration of periods of peak aeolian activity in Minnesota. Palaeowind studies from the Minnesota dune fields show that the dominant wind direction when the dunes were active was from the northwest, the same as the dominant wind direction in dune fields throughout the Great Plains and Rocky Mountains. If the mid-Holocene aeolian activity in Minnesota was driven by an increase in westerly zonal winds, then the varve calibration can be extended to more precisely determine the timing of activity of dunes over a much broader area. We suggest that an increase in the westerly zonal wind field might have a solar-geomagnetic cause.
Long-term population dynamics of Fagus sylvatica at the northern limits of its distribution in southern Sweden: a palaeoecological study
Authors: Björkman Leif
Published: November 2007

Regional pollen diagrams indicate that Fagus may have been present close to its northern distri butional limits in southern Sweden for as long as 1000 years. Fagus has probably always been rare in this region, except for some small and scattered stands. Many of these outlying Fagus stands have been regarded as planted but no previous studies have investigated this in detail. At Mattarp, a small outpost Fagus stand in northern Småland, the pollen record of the deposit of a small hollow indicates that Fagus became established c. 400 BP. The local establishment was associated with an earlier phase of woodland clearance and the former system of land-use. Local factors seem to have controlled the immigration and establishment at the stand-scale at this site. Regional climate had probably been favourable for Fagus for almost 2000 years and cannot be regarded as the direct cause for establishment at this site. The complex south Swedish cultural landscape may have favoured Fagus establishment in many areas, particularly when there has been a temporary reduction in human influence. Picea became regionally established around 800 BP, but a local expansion did not occur until c. 400 BP, coinciding with the establishment of Fagus. Picea expansion also seems to have been favoured by a moderate human influence at this site. Fagus pollen influx values have steadily increased since the time of establishment. It seems likely that the Fagus stand has continually increased in size, and probably would continue to do so if this were not prevented by human activities.
Palaeo-reversals in groundwater flow and peatland development at Lost River, Minnesota, USA
Authors: Glaser Paul H. , Bennett P.C. , Siegel D.I. , Romanowicz E.A.
Published: November 2007

Raised bogs represent end-products of peatland development that are generally assumed to be decoupled from the regional groundwater system. However, the development of two peat mounds in northern Minnesota was driven by three major reversals in its groundwater-flow regime. A 4000-year record of groundwater flow was reconstructed by stratigraphic studies that utilized both botanical indicators of the surface-water chemistry, and mineral indicators of the pore-water chemistry and chemical weathering regime. The mineral stratigraphy indicated that the peat mounds were initially formed under a discharge (upward flow) regime. During the succeeding moist period, these peat mounds developed into raised bogs as their water-table mounds drove local recharge (downward) flow into the mineral substratum. A major reversal to a prevailing discharge regime at 1200 BP, however, converted the smaller peat mound into a spring fen and weathered the silicate minerals within the peat profile of the larger mound. This reversal was apparently caused by the onset of extended droughts, which dissipate the water table mound within these peat landforms.
Fuegian floating tree-ring chronology from subfossil Nothofagus wood
Authors: Roig F. , Roig C. , Rabassa J. , Boninsegna J.
Published: November 2007

The discovery of subfossil Nothofagus wood buried in several peat bogs of Argentine Tierra del Fuego is reported. A provisional, fragmented-floating tree-ring width chronology covering the last 1400 years has been obtained. Statistical and spectral analysis revealed no significant differences between the present and floating Tierra del Fuego tree-ring chronologies. Some cyclical growth peculiarities found in both modern and floating chronologies are discussed.
Late-glacial and Holocene vegetation and environment of Campbell Island, far southern New Zealand
Authors: McGlone M.S. , Moar N.T. , Wardle P. , Meurk C.D.
Published: November 2007

Campbell Island lies 600 km southeast of the New Zealand mainland. Scrub, grassland, rushes and large-leaved forb vegetation grow on the deep peats that cover nearly the entire island. Campbell Island was extensively glaciated at the height of the Last Glaciation and mean annual temperatures were about 5°C below present. Peat growth began c. 13 000 BP, and large-leaved forbs, rushes and other tundra plants grew under a cooler (—3°C) climate than now. Grassland largely replaced the large-leaved forbs at around 9500 BP as the climate warmed. Scrub and dwarf forest of Dracophyllum was uncommon until around 7000 BP and reached its greatest altitudinal and areal extent between then and 3000 BP. Warmer (+0.5°C), drier summer conditions during the mid- to late Holocene favoured this scrub expansion. In the late Holocene, Dracophyllum scrub was reduced in density and altitudinal range, probably by cooling temperatures and increased southwesterly winds. A warming of the island by 1 °C since the turn of the century may have encouraged Dracophyllum to spread into tussock and bog communities depleted by late nineteenth to early twentieth century fire and grazing.
Structure and composition of the subalpine forest on Mount Hauhungatahi, North Island, New Zealand, during the Holocene
Authors: Ogden John , Horrocks Mark , Palmer Jonathan G. , Fordham Robin A.
Published: November 2007

Tree stumps of Holocene age were identified and measured at three sites above the present tree-line on Mount Hauhungatahi, Tongariro National Park, New Zealand. Wood and peat were radiocarbon dated and annual rings in stump cross-sections counted for growth-rates. Comparative measurements were made in three plots in the modern subalpine forests. Stem densities and basal areas in the ancient forest were within the range of the modern subalpine forest samples. The conifers Halocarpus biformis, Phyllocladus asplenifolius var. alpinus, and Libocedrus bidwillii were present in both sets of samples, but in different proportions. Modern forest plots also contained Podocarpus hallii and angiosperm trees. Tree-line forest, composed predominantly of Halocarpus bidwillii, reached 1340 m by c. 10000 cal. BP and c. 1390 m by 8700 cal. BP. These early- Holocene H. bidwillii trees were slower-growing and longer-lived than the same species in current subalpine forests. From c. 5400 to 3800 cal. BP woody vegetation was again preserved. The current irregularly depressed timberline appears to have been initiated before the Taupo eruption (c. 1700 cal. BP). Charcoal indicates infrequent fires in the subalpine bogs and scrublands in post-Taupo time.
Evidence for a more recent occurrence of water chestnut (Trapa natans L.) in Finland and its palaeoenvironmental implications
Authors: Korhola A.A. , Tikkanen M.J.
Published: November 2007

Pollen and diatom analyses as well as radiocarbon datings were used to study the development of the ancient lake-basin Pyysuo in SW Finland with mass occurrence of Trapa natans subfossil fruits in its sediments. The basin was isolated from the Baltic Sea c. 4300 BP, after which it continued to develop as a shallow, eutrophic, alkaline and vegetation-rich small lake until the final overgrowth by a mire at c. 2500 BP. The fossil fruits of Trapa natans appeared in the sediments c. 3500 BP, and reached their maximum abundance just prior to filling-in. In view of the great time span of its finds now in Finland (8500-2500 BP), its occurrence was evidently not directly limited by the mean temperature, but the habitat availability and local conditions in the lake basins themselves.
Human impact on the history of Lake Nômmejärv, NE Estonia: a geochemical and palaeobotanical study
Authors: Punning J.-M. , Boyle J.F. , Alliksaar T. , Tann R. , Varvas M.
Published: November 2007

A comprehensive geochemical and palaeobotanical study of the lacustrine sediments of Lake Nôm mejärv from industrialized NE Estonia establishes the links between the nature and intensity of human activities and their impacts on the state and structure of the lake ecosystem. In cores of sediment formed during the last century, five zones can be distinguished, each reflecting a pattern of human activity and characterized by a particular diatom community and sediment composition. Using reliable geochronological data it is possible to compare these zones with the known industrial load on the lake and its catchment area. The information obtained is of practical value for planning the rehabilitation of this severely impacted lake.
Development and age structure of Holocene coastal sand dunes at Horn Head, near Dunfanaghy, Co Donegal, Ireland
Authors: Wilson Peter , Braley Sharon M.
Published: November 2007

Two areas of Holocene coastal sand dunes on the western side of the Horn Head peninsula extend from low ground immediately inland of their respective source beaches onto flanking higher ground (> 100 m OD). Stratigraphic investigations supported by 14C dating of buried organic-rich horizons and shells demonstrate several phases of sand accumulation in the Pollaguill-Croaghadara system in contrast to the larger Tramore-Anloge Hill system, where the available evidence points to relatively recent dune emplacement. A broadly synchronous phase of dune development occurred during the thirteenth to fourteenth centuries AD and is viewed as part of a regional (northwestern Europe) dune-building episode resulting from climatic deterio ration. Earlier phases (pre-3300-2800 14C years BP) of aeolian sand deposition at Pollaguill-Croaghadara have no apparent equivalents at Tramore-Anloge Hill and repeated fluvial incision and sand reworking during the last 2000 14C years is also evident at the former site. Dated organic horizons, in combination with site location, sand source and transport direction, suggest the earliest phase of aeolian sand accumulation and subsequent stabilization was time-transgressive. The respective roles of relative sea-level change, climatic change and anthropogenic influence in dune evolution are difficult to evaluate in the absence of detailed information, although documentary evidence indicates human-induced destabilization of the Tramore-Anloge Hill dunes during the 1920s and 1930s. Thus, despite similar topographic settings and close proximity, the dunes do not share entirely similar histories and caution against the development of regional dune chronologies from investi gations of single systems. The observations and data suggest that a mix of local and regional controls have combined in the construction of these dunes.
History of forest fires in eastern Finland from the fifteenth century AD - the possible effects of slash-and-burn cultivation
Authors: Lehtonen Hannu , Huttunen Pertti
Published: November 2007

The history of forest fires in two areas in eastern Finland, Kitsi and Ahvenjärvi, both of about 150 ha, is studied by dendrochronological dating of fire scars. Forty-nine samples were collected from Kitsi and 20 samples from Ahvenjärvi. The history of fires spans the period AD 1403-1994 at Kitsi and 1359-1994 at Ahvenjärvi, within which a total of 23 fire years were dated for Kitsi and 22 for Ahvenjärvi. Over the 400- year period of AD 1500-1900, fires occurred an average of once every 19.2 years in Kitsi and once every 20.6 years in Ahvenjärvi. The mean fire interval at Kitsi was 42.3 years and that at Ahvenjärvi 48.8 years before AD 1650 and 32.2 years after 1650. Forest fires increased towards the end of the seventeenth century and decreased markedly after 1850. There were fewer fires for a time at the beginning of the eighteenth century, especially in Kitsi. The changes in the history of fires reflect changes in the population of North Karelia and the extent of slash-and-burn cultivation. Past forest fires were a major factor influencing the vegetation dynamics of the boreal forests of North Karelia, and slash-and-burn cultivation has greatly affected the history of fires in the region.
Late-Holocene rodent middens from Rio Limay, Neuquen Province, Argentina
Authors: Markgraf Vera , Betancourt Julio , Rylander Kate Aasen
Published: November 2007

Pollen analysis of late-Holocene amberat deposits from two caves near the forest-steppe ecotone in northern Patagonia documents a major shift from Austrocedrus-Nothofagus forest to steppe shrub assemblages some time after 1800 and before 1300 BP. The probable explanation of the reduction of tree taxa calls for either drier summers or intensified land use or a combination of both.
Holocene lake-level rise in the Upper Peninsula of Michigan, USA, as indicated by peatland growth
Authors: Brugam Richard B. , McCance Johnson Stacy
Published: November 2007

We examined one sediment core from Kerr Lake and eight cores from the adjacent peatland in the Sylvania Wilderness Area of the Upper Peninsula of Michigan, USA. Radiocarbon dating of the interface between peat and the underlying glacial till showed that the peatland grew by paludification of the surrounding uplands, implying a rising water level in the lake. Pollen analysis of the cores showed that the peatland began expanding just before the arrival of Tsuga in the surrounding forests. The most rapid growth of the peatland occurred between 3900 and 3000 BP. This is also the time when the forests were being transformed from dry Pinus strobus-dominated woodlands to moister Tsuga- and Acer saccharum-dominated northern hardwoods. Our results imply an increase in available moisture at the time of Tsuga colonization.