ALBERT

Description: Tephra layers can form useful age-equivalent stratigraphic markers for correlating palaeoenvironmental sequences and they provide information about the spatio-temporal nature of past volcanic ash fall events. The use of microscopic ‘cryptotephra’ layers has both increased the stratigraphic resolution of tephra sequences in proximal areas and extended the distal application of tephrochronology to regions of the world situated far from volcanoes. Effective tephrochronology requires the discrimination between in situ tephra deposited directly from volcanic plumes and tephras that have been remobilised since their initial deposition. We present tephrostratigraphic and glass chemistry data from two proximal peat profiles (one lowland, one upland) from the Shetland Islands, UK. Both profiles contain the Hekla-Selsund tephra (deposited c. 1800–1750 cal. bc ), whilst the Hekla 4 ash (c. 2395–2279 cal. bc ) is present in the upland record. Overlying the Hekla-Selsund tephra are a number of distinct peaks in tephra shard abundance. The geochemistry of these layers shows that they represent re-working of the Hekla 4 and Hekla-Selsund layers rather than primary air-fall deposits. Pollen analysis of the peat sequences illustrates that these re-deposited tephra layers are coincident with a rise in heather-dominated vegetation communities (heath and/or moorland) and a subsequent intensification of burning in the landscape. We suggest that burning caused increased erosion of peats resulting in the remobilisation of tephra shards. The study demonstrates both the need for caution and the opportunities created when applying tephrochronologies in regions heavily affected by past human activity that contain both reworked tephra layers and in situ fallout.

Description: Bomb-pulse dated mini moss-monoliths were used to determine modern pollen accumulation rates on mire surfaces at six locations in northern and central Norway. Coupled with vegetation data these were used to assess the modern pollen–vegetation relationships for Pinus, Betula and Poaceae. Preliminary absolute pollen productivity (APP) estimates are for Pinus sylvestris 11,300 ± 2300 (SE) grains/cm 2 per yr, Betula pubescens 2200 ± 300 and Poaceae 1800 ± 200. The study suggests that pollen accumulation rates and absolute pollen productivity estimates can be derived from mire surface peat. This would ease the establishment of APP estimates for more taxa and regions than available today.

Description: This study focuses on the reconstructions of vegetation and climate changes during the past ~11,000 years on the basis of 222 fossil pollen samples from Qigai Nuur (core QGN-2004) in the southern part of the Mongolian Plateau. Plant Functional Type – Modern Analogue Technique was used for quantitative climatic reconstructions from fossil pollen data. Our results showed that regional vegetation experienced dramatic shifts between steppe forest and dry steppe before 9200 cal. yr BP in the Qigai Nuur region. The reconstructed mean annual temperature and especially mean annual precipitation also showed fluctuations at that time. From ~9200 to ~2800 cal. yr BP, the vegetation was dominated by steppe forests, and the reconstructed climate was generally warm and wet, but with two cold and dry intervals at ~7400 to ~6000 cal. yr BP and at ~4000 to ~2800 cal. yr BP. From ~2800 to ~850 cal. yr BP, dry steppe vegetation dominated the landscape under slightly cooler and much drier climate conditions. During the past ~850 years, the vegetation was characterized by abundant herbs and the climate showed rising temperature and fluctuating precipitation. The comparison of the reconstructed precipitation from the Qigai Nuur core with monsoon-strength records from southern China shows that the first-order variation in the precipitation was most likely controlled by the summer insolation-dictated Inter-Tropical Convergence Zone movements (i.e. N–S shifts). The comparison of the reconstructed precipitation from Qigai Nuur core with surface sea temperature in the Western Tropical Pacific Ocean suggests that the second-order variation in the precipitation was most likely modulated by the El Niño-Southern Oscillation dynamics (i.e. E–W shifts).

Description: In recent decades the biometric analysis of shellfish resources (mainly marine mollusc shells) has been used by many researchers to support the hypothesis of their more intensive human use and to estimate the increase in human populations. This paper studies the plates of the crustacean Pollicipes pollicipes found in three Holocene archaeological levels at the Jaizkibel 3 shell-midden (Gipuzkoa, Basque Country, Northern Spain). First, by analysing a sample from each level, the Minimum Number of Individuals (MNI) was calculated from the Number of Remains (NR). Second, by using one of the plates (right scutum ), the biometry of P. pollicipes in the three levels was reconstructed. The measurements are compared with a sample of P. pollicipes , collected a few kilometres away from the site of J3. The results indicate that the barnacles were not overexploited by the human groups.

Description: The environment of the northern taiga to tundra transition is highly sensitive to climate fluctuations. In this study from northeastern European Russia, stable carbon and oxygen isotope ratios ( 13 C, 18 O) in α-cellulose of Sphagnum fuscum stems subsampled from hummocks and peat plateau profiles have been used as climate proxies. The entire isotope time series, dated by lead ( 210 Pb), caesium ( 137 Cs) and AMS-radiocarbon ( 14 C) dating, spans the past 2500 years. Plant macrofossil analyses were used as an aid in single species selection, but are also helpful in identifying past surface moisture conditions. The most significant relationships were found between the recent 13 C record and summer (July–August) temperatures ( R 2 = 0.58, p 〈 0.01), and the recent 18 O record and winter (October–May) precipitation anomalies in the tundra region ( R 2 = 0.36, p 〈 0.01). The study demonstrates that stable isotopes preserved in northern peat deposits are useful indicators for summer temperature and winter precipitation at decadal to millennial timescales.

Description: Floodplain deposition rates have increased markedly under influence of human impact throughout the late Holocene in many western and central European catchments. Consequently the geomorphology and ecology of many floodplains changed. In this study we discuss this human impact and its influence on the floodplain geoecology during the middle and late Holocene for the headwaters of the Dijle catchment, located in the Belgian loess belt. The floodplain geoecology and the regional vegetation was reconstructed from sedimentological and palynological analyses. An age–depth model for the studied sequences was obtained using 17 radiocarbon dates. Statistical analyses of the pollen data (cluster analysis and canonical correspondence analysis) were used to detect changes in the pollen record. Our data show that until c. 2500 cal. BP, human impact was nearly absent or localized with no discernible influence on the floodplain geoecology. The floodplain was in a stable phase and consisted of a marshy environment where organic material could accumulate, which is interpreted as the natural state of the floodplain. From c. 2500 cal. BP onwards, human impact gradually increased. However, only when human impact in the catchment crossed a threshold around 500 cal. BP, the floodplain geoecology changed with clearing of the Alder carr forest, the establishment of a single channel river and the dominance of minerogenic overbank sedimentation. Spatial variability in the coupling between increasing human impact and changes in floodplain geoecology can be attributed to differences in hillslope–floodplain connectivity and local differences in human impact.

Description: Lake sediments from Lauenensee (1381 m a.s.l.), a small lake in the Bernese Alps, were analysed to reconstruct the vegetation and fire history. The chronology is based on 11 calibrated radiocarbon dates on terrestrial plant macrofossils suggesting a basal age of 14,200 cal. BP. Pollen and macrofossil data imply that treeline never reached the lake catchment during the Bølling–Allerød interstadial. Treeline north of the Alps was depressed by c. 300 altitudinal meters, if compared with southern locations. We attribute this difference to colder temperatures and to unbuffered cold air excursions from the ice masses in northern Europe. Afforestation started after the Younger Dryas at 11,600 cal. BP. Early-Holocene tree- Betula and Pinus sylvestris forests were replaced by Abies alba forests around 7500 cal. BP. Continuous high-resolution pollen and macrofossil series allow quantitative assessments of vegetation dynamics at 5900–5200 cal. BP (first expansion of Picea abies , decline of Abies alba ) and 4100–2900 cal. BP (first collapse of Abies alba ). The first signs of human activity became noticeable during the late Neolithic c. 5700–5200 cal. BP. Cross-correlation analysis shows that the expansion of Alnus viridis and the replacement of Abies alba by Picea abies after c. 5500 cal. BP was most likely a consequence of human disturbance. Abies alba responded very sensitively to a combination of fire and grazing disturbance. Our results imply that the current dominance of Picea abies in the upper montane and subalpine belts is a consequence of anthropogenic activities through the millennia.

Description: Holocene paleoclimate records from Greenland help us understand the response of the Greenland Ice Sheet and regional oceanic and atmospheric circulation systems to natural climate variability in order to place recent changes in a longer-term perspective. Here biogeochemical analysis of a lake sediment core from southeast Greenland is used to define changes in moisture balance and runoff during the Holocene in a catchment near the margin of the Greenland Ice Sheet. A 1.6 m sediment core that spans the last 8.8 ka was recovered from Flower Valley Lake on Ammassalik Island. Magnetic susceptibility, diatoms, bulk biogeochemical properties (TOC, C/N, 13 C org ), and lipid biomarkers ( n -alkanes; C 16 –C 31 ) reveal changes in clastic sedimentation and the relative input of terrestrial- and aquatic-derived organic matter. Hydrogen isotope values ( D ) of mid- ( n -C 25 ) and long-chain ( n -C 29 , n -C 31 ) n -alkanes allow reconstruction of D of precipitation and summertime evaporation of lake water. Following a period of early lake ontogeny and landscape stabilization after deglaciation from 8.4 to 7.0 ka, the mid Holocene, 8.4–4.1 ka, is characterized by greater evaporative enrichment of the lake water as indicated by D records. After 4.1 ka, there is a decrease in evaporative enrichment of the lake water. There is also an abrupt transition to more variable sedimentation marked by sharp increases in magnetic susceptibility, C/N, 13 C org , and the concentration of long-chain n -alkanes, showing periodic delivery of terrestrial organic matter and clastic sediment to the lake. Higher insolation during the mid Holocene resulted in a warmer and drier climate with longer ice-free periods in the summer and enhanced evaporation of lake water. The reduction in insolation and colder temperatures during the late Holocene caused a reduction in evaporation of lake water over the last 4.1 ka and was accompanied by periodic increases in surface runoff, which correspond with intervals of cold Greenland Ice Sheet surface temperatures.

Description: We present a high-resolution isotope stratigraphy based on Globigerinoides ruber (white) over the past 2500 years in the Gulf of Taranto, central Mediterranean. G. ruber (white) reflects summer conditions in the Gulf of Taranto but is influenced by two major surface water masses: the Western Adriatic Current (WAC) and the Ionian Surface Water (ISW) and their variations on a decadal to multicentennial scale. Our analysis of the 13 C and 18 O of G. ruber (white) allows the distinction of several climatic periods: the ‘Roman Warm Period’ (RWP) (450–0 bc ), with relatively wet and warm conditions and a higher influence of the WAC; the ‘Roman Classical Period’ (RCP) ( ad 1–200) characterized by salinity increase resulting from circulation changes; the ‘Dark Ages Cold Period’ (DCP) ( ad 500–750), where wetter conditions in the Gulf of Taranto region are coherent with an increase dominance of the WAC; the ‘Medieval Warm Period’ (MWP), with wet and warm conditions in the first, and a gradual drying in the second half; and finally, the transition from the MWP to the ‘Little Ice Age’ (LIA), which is characterized by continuing dry conditions.

Description: Using various archaeological and geoarchaeological operations, charcoal and waterlogged wood assemblages have been sampled in the marshy areas from the lower Dauphiné (Rhone valley, France). Their identification allows reconstructing the evolution of the woody vegetation in relation to climatohydrological changes and with human practices in the plain since the mid Holocene. It appears that humid-land forests have experienced a shift from ash formations (dominating during Pre- and Protohistory) toward alder formations between the Bronze Age and Roman Period. That vegetation change seems to be linked with pastoral practices in which fire is used as a clearing and regeneration tool. The intense pastoral use of the plain, together with the humidity of the soils when not artificially drained, may also have prevented the development of dense and mature forests. Finally, we show that beech, which is currently absent from the plain, probably grew in the marshlands during the past.

Description: High-resolution macroscopic charcoal and sediment analysis was used to reconstruct fire history and environmental changes from three loess-paleosol profiles on the semi-arid loess tableland landscape during the Lateglacial period and the Holocene. Analysis of charcoal concentrations, influx, and the ratios of particle-size classes (from which changes in charcoal taphonomy over time are inferred) in the profiles show spatially coherent patterns of change that relate to regional variations in climate. Effective moisture variability on century to millennial timescales and regional differences in fuel availability appear to be the most important controls on fire from the Lateglacial period to the mid Holocene (12,000–3100 yr BP). Conversely, asynchronous fire patterns during the late Holocene appear to indicate regional and temporal variations as well as changing intensities of human activity. Land use intensified in the region during the late Holocene, when the climate became more arid, and a distinct increase in charcoal concentration then indicated an unprecedented increase in biomass burning. The increase in fire activity occurs in the recent loess layer (L 0 ) and the surface soil (TS) consistent with the establishment of irrigated farming for cereal cultivation in the southern part of the study region about 3100 yr BP. Broad-scale land reclamation was extended to the loess tableland region about 2170–1730 yr BP (during the Qin-Han Dynasty period), and the rapidly decreasing charcoal concentration in the accumulated topsoil (at depths of less than 20 cm) at the CCY site since 1500 yr BP is consistent with the development of terrace farming in the northern part of the study region at that time. In summary, the evolution of fire history in the study profiles across the region is closely related to (1) gradients in humidity; (2) spatial and temporal variability in the distribution and intensity of human land use; and (3) the buildup of burnable biomass, among which there was a nonlinear complex relationship during the Holocene. Increased efforts to synthesize and analyze multiple paleo-environmental records and to combine these with multiproxy evidence are needed to understand wildfire history as well as human land use and social cultural development across the region in depth.

Description: A new sedimentary sequence from Lago di Venere on Pantelleria Island, located in the Strait of Sicily between Tunisia and Sicily was recovered. The lake is located in the coastal infra-Mediterranean vegetation belt at 2 m a.s.l. Pollen, charcoal and sedimentological analyses are used to explore linkages among vegetation, fire and climate at a decadal scale over the past 1200 years. A dry period from ad 800 to 1000 that corresponds to the ‘Medieval Warm Period’ (WMP) is inferred from sedimentological analysis. The high content of carbonate recorded in this period suggests a dry phase, when the ratio of evaporation/precipitation was high. During this period the island was dominated by thermophilous and drought-tolerant taxa, such as Quercus ilex, Olea, Pistacia and Juniperus . A marked shift in the sediment properties is recorded at ad 1000, when carbonate content became very low suggesting wetter conditions until ad 1850–1900. Broadly, this period coincides with the ‘Little Ice Age’ (LIA), which was characterized by wetter and colder conditions in Europe. During this time rather mesic conifers (i.e. Pinus pinaster ), shrubs and herbs (e.g. Erica arborea and Selaginella denticulata ) expanded, whereas more drought-adapted species (e.g. Q. ilex ) declined. Charcoal data suggest enhanced fire activity during the LIA probably as a consequence of anthropogenic burning and/or more flammable fuel (e.g. resinous Pinus biomass). The last century was characterized by a shift to high carbonate content, indicating a change towards drier conditions, and re-expansion of Q. ilex and Olea . The post-LIA warming is in agreement with historical documents and meteorological time series. Vegetation dynamics were co-determined by agricultural activities on the island. Anthropogenic indicators (e.g. Cerealia-type, Sporormiella ) reveal the importance of crops and grazing on the island. Our pollen data suggest that extensive logging caused the local extinction of deciduous Quercus pubescens around ad 1750.

Description: A 1.70 m core extracted from the Lac des Lauzons, Haut Champsaur, French Alps, at 2180 m altitude, provided a detailed Holocene record of beetles, pollen and plant macrofossils, enabling the reconstruction of local palaeoenvironmental changes during the last 10 000 years. After an early phase of colonization by plants and insects, corresponding to the Lateglacial interstadial, a long phase of relative stability of the ecosystems (at least in the vicinity of the lake) is recorded. Strikingly, there is no evidence from beetle and plant macrofossils that the treeline reached the altitude of Lauzons during the Holocene climate optimum, although this period is characterized by major forest expansion in many high-altitude sites in the southern French Alps. The uppermost part of the record is blurred by the infilling of the lake, progressively turning into a peat bog. This sequence also provides an opportunity to compare the records of coprophilous fungal spores and coprophilous beetles and to improve the interpretation of these proxies in terms of their significance as proxies for pastoralism.

Description: A sedimentary basin within the Tjörnes Fracture Zone on the north Icelandic shelf has been investigated with the purpose of locating tephra layers for dating and stratigraphical correlations of terrestrial and marine archives. Two new mid-Holocene tephra markers originating from the Hekla volcano in Iceland have been identified in the marine sediment core MD99-2275 retrieved from the basin east of the island of Grímsey. These tephra layers have been correlated to their terrestrial counterparts, the Hekla Ö tephra and the Hekla DH (Dark Horse) tephra. The Hekla Ö tephra has been dated to 6060±115 cal. yr BP by four AMS 14 C dates from two terrestrial sites in Iceland. An age estimate of 6650 cal. yr BP has been calculated (SAR, soil accumulation rate) for the Hekla DH tephra from three soil sections in Iceland. Preliminary volume estimates of the Hekla Ö and Hekla DH tephra layers are ~1 km 3 and ~0.8 km 3 , respectively. These two tephra layers enhance the age control between the Hekla 4 and Hekla 5 tephra markers in the shelf sediments previously unrestrained by terrestrially dated tephra markers and are a valuable addition to the tephrochronology of Iceland and the north Icelandic shelf.

Description: Environmental reconstructions based on fossil pollen rely on the understanding of modern pollen distribution along climatic and biogeographic gradients. This study analyses the modern pollen spectra of Central America using three basic approaches: (1) the evaluation of using modern pollen spectra to differentiate the main vegetation types of the region, (2) the usage of non-linear regression to predict individual pollen abundances as a function of climate, and (3) the construction of pollen—climate transfer functions. Standard pollen analysis was carried out on mud—water interface samples from 81 lakes in the Yucatan Peninsula and adjacent mountains of Guatemala and Mexico. Detrended correspondence and cluster analyses were used to evaluate the biogeographic patterns revealed by this modern pollen data set. Non-parametric locally weighted scatterplot smoothing (LOESS) regression was used to construct pollen—climate functional relationships. Five modern vegetation types were clearly identifiable through their associated pollen spectra: Pinus forest, Quercus forest, mountain mesophyllous forest, tropical rainforest, and tropical seasonal forest. The last group includes three subcategories (evergreen seasonal, tropical semi-deciduous, and tropical deciduous forests), which were not separable via this analysis. Precipitation and temperature trends were consistent and robust for at least 28 and 30 taxa, respectively, in the LOESS regression. While floristic patterns driven by temperature were clearly reflected by the pollen spectra, those driven by precipitation were less sharply defined. Nevertheless, pollen data from the study area offered good resolution to identify broad biogeographic patterns. Furthermore, individual taxa showed high predictability along precipitation and temperature gradients, allowing the theoretical construction of pollen—climate transfer functions. This study provided valuable tools for the interpretation of fossil pollen sequences from Central America.

Description: We utilized dendrochronology and precise elevation-constrained mapping to date glacially overridden and drowned trees at the margin of Brady Glacier in southeast Alaska. This technique allowed determination of the timing of the former tidewater glacier’s last advance and consequent formation and filling of two marginal lakes. The subfossil tree-ring chronology spans the interval from AD 1370 to 1861. Brady Glacier impounded Spur Lake to an elevation of 83 m a.s.l. around 1830 and 121 m a.s.l. around 1839. Soon after, Spur Lake reached 125 m a.s.l. and began to overflow a stable bedrock sill. The glacier continued to advance, thickening by at least 77 m between c . 1844 and 1859 at a site down-glacier of Spur Lake on the opposite glacier margin. Farther down-glacier, North Trick Lake began to form by 1861 and reached its highest elevation at approximately 130 m a.s.l. when Brady Glacier reached its maximum extent around 1880. Our findings add precision to the chronology of the last advance of Brady Glacier and provide insight into the evolution of glacier-dammed lakes and calving glaciers.

Description: Three weeks after arriving near the Pacific Northwest (PNW) coast in November 1805, Lewis and Clarks’ Corps of Discovery experienced a two-day windstorm that may have rivaled the strongest historically documented storms of the nineteenth and twentieth centuries. Based on the Corps’ detailed historical accounts describing the event as the perfect storm, we characterized the severity of the 1805 windstorm using tree-ring growth anomalies from windsnapped Sitka spruce collected at three sites along the northern Oregon Coast. We compared the 1805 gale to eight other documented events with comparable storm tracks and exceptional magnitude including the 1880 and 1951 events that each caused more than a billion board feet ( c. 2.4 million m 3 ) of windthrow. Statistical comparison of tree-growth responses revealed that the 1805 windstorm was the only event to differ significantly ( 2 ; test, p 〈 0.05, d.f. = 1) from all other storms. Our findings demonstrate the potential application of tree-ring data and historical documents to understand previously obscure climatic events similar to the extreme droughts that led to the demise of the Roanoke Colony during the sixteenth century and adversity experienced by the Jamestown Colony during the seventeenth century. Specifically, we identify the Lewis and Clark tempest of 1805 as being among the most severe PNW windstorms during the past two centuries, and may have contributed to the Corps’ dismal view of coastal Pacific Northwest weather.

Description: Past seasonality changes are often poorly represented by Quaternary proxies because one season, or one factor, dominates the reconstructed signal. During the early Holocene in New Zealand, mean annual temperatures were at least 1.5°C warmer than present. However, treelines were lower, suggesting summers were cooler. Here we use a forest ecosystem process model, LINKNZ, to explore past precipitation and temperature seasonality changes in an intermontane basin of the Southern Alps, New Zealand. Pollen and macrofossils from the basin show that during an early-Holocene warm event (11 500 to 9500 cal. yr BP) podocarp and broadleaved species dominated. In exploratory modelling runs, mean annual temperatures were increased by up to 2°C, precipitation was reduced by 20—30%, and temperature seasonality reduced. When mean annual temperature was increased by 1.0—2.0°C, LINKNZ reconstructed wet forest associations, very different to those in the early-Holocene fossil assemblages. Acceptable matches were made with the early-Holocene vegetation using elevated temperature scenarios with up to 30% lower annual precipitation and decreased temperature seasonality. Longer growing seasons apparently compensate for cooler summer temperatures. We suggest that during the early Holocene in this area, westerly wind flow over the Southern Alps to the west of the basin was less, reducing spill-over rainfall and vapour pressure deficits. Warm oceans generated milder, cloudier climates reducing seasonal contrasts. Inverse modelling is recommended as a tool for exploring past climate scenarios when proxies fail to reconstruct important climate variables.

Description: Based on multiproxy investigations of a 250 cm long sediment core (ALI1), a reconstruction of palaeoenvironmental dynamics for the Alimini Piccolo lake (south Adriatic coast of Apulia, Italy), is proposed. Our results indicate that shortly before 5500 cal. yr BP a marsh environment established. From 5400 cal. BP the marsh progressively became a lagoon and did not change until 3320 cal. BP, when Alimini Piccolo evolved into a shallow, sheltered, freshwater basin. Around 1400 cal. yr BP the basin became again a lagoon. Changes of the deposition environments and the chronological framework defined in the ALI1 sequence allowed speculation about local relative sea-level motions through the mid—late Holocene. Using proxy-data (molluscs, foraminifers, ostracods and plant macro-remains) as environment and bathymetry indicators, we reconstruct the elevation of the basin bottom (above or below sea level) through time. Plant macro-fossils have proved to be an especially reliable source of data for sea-level reconstruction. The resulting relative sea-level curve is characterised by a slow rise between 5500 and 3900 cal. yr BP, a drop culminating around 2500 cal. yr BP and a new, steeper rise continued to the present position. Our model differs from other curves (tectonically and isostatically corrected) proposed for a number of Mediterranean coastal sites where Holocene sea-level changes have been described with a continuously rising curve, steep before 7000—6000 yr BP, more gradual between 6000 yr BP and the present. On the other hand, our reconstruction seems to agree with evidence on sea-level position during the Roman age, found in several Apulian sites (Salento coastland) by means of geomorphological and archaeological investigations.

Description: Instrumental monitoring of the climate at high northern latitudes has documented the ongoing warming of the last few decades. Climate modelling has also demonstrated that the global warming signal will be amplified in the polar region. Such temperature increases would have important implications on the ecosystem and biota of the Barents Sea. This study therefore aims to reconstruct the climatic changes of the Barents Sea based on benthic foraminifera over approximately the last 1400 years at the decadal to sub-decadal scale. Oxygen and carbon isotope analysis and benthic foraminiferal species counts indicate an overall warming trend of approximately 2.6°C through the 1400-year record. In addition, the well-documented cooling period equating to the ‘Little Ice Age’ is evident between c . 1650 and 1850. Most notably, a series of highly fluctuating temperatures are observed over the last century. An increase of 1.5°C is shown across this period. Thus for the first time we are able to demonstrate that the recent Arctic warming is also reflected in the oceanic micro-fauna.

Description: For thousands of years, humans have inhabited locations that are highly vulnerable to the impacts of climate change, earthquakes, and floods. In order to investigate the extent to which Holocene environmental changes may have impacted on cultural evolution, we present new geologic, geomorphic, and chronologic data from the Qazvin Plain in northwest Iran that provides a backdrop of natural environmental changes for the simultaneous cultural dynamics observed on the Central Iranian Plateau. Well-resolved archaeological data from the neighbouring settlements of Zagheh (7170—6300 yr BP), Ghabristan (6215—4950 yr BP) and Sagzabad (4050—2350 yr BP) indicate that Holocene occupation of the Hajiarab alluvial fan was interrupted by a 900 year settlement hiatus. Multiproxy climate data from nearby lakes in northwest Iran suggest a transition from arid early-Holocene conditions to more humid middle-Holocene conditions from c . 7550 to 6750 yr BP, coinciding with the settlement of Zagheh, and a peak in aridity at c . 4550 yr BP during the settlement hiatus. Palaeoseismic investigations indicate that large active fault systems in close proximity to the tell sites incurred a series of large (M W ~7.1) earthquakes with return periods of ~500—1000 years during human occupation of the tells. Mapping and optically stimulated luminescence (OSL) chronology of the alluvial sequences reveals changes in depositional style from coarse-grained unconfined sheet flow deposits to proximal channel flow and distally prograding alluvial deposits sometime after c . 8830 yr BP, possibly reflecting an increase in moisture following the early-Holocene arid phase. The coincidence of major climate changes, earthquake activity, and varying sedimentation styles with changing patterns of human occupation on the Hajiarab fan indicate links between environmental and anthropogenic systems. However, temporal coincidence does not necessitate a fundamental causative dependency.

Description: A high-resolution sedimentological and geochemical study was performed on a 20 m long core from the alpine Lake Anterne (2063 m a.s.l., NW French Alps) spanning the last 10 ka. Sedimentation is mainly of minerogenic origin. The organic matter quantity (TOC%) as well as its quality (hydrogen (HI) and oxygen (OI) indices) both indicate the progressive onset and subsequent stabilization of vegetation cover in the catchment from 9950 to 5550 cal. BP. During this phase, the pedogenic process of carbonate dissolution is marked by a decrease in the calcium content in the sediment record. Between 7850 and 5550 cal. BP, very low manganese concentrations suggest anoxic conditions in the bottom-water of Lake Anterne. These are caused by a relatively high organic matter (terrestrial and lacustrine) content, a low flood frequency and longer summer stratification triggered by warmer conditions. From 5550 cal. BP, a decrease in TOC, stabilization of HI and higher sedimentation rates together reflect increased erosion rates of leptosols and developed soils, probably due to a colder and wetter climate. Then, three periods of important soil destabilization are marked by an increased frequency and thickness of flood deposits during the Bronze Age and by increases in topsoil erosion relative to leptosols (HI increases) during the late Iron Age/Roman period and the Medieval periods. These periods are also characterized by higher sedimentation rates. According to palynological data, human impact (deforestation and/or pasturing activity) probably triggered these periods of increased soil erosion.

Description: Fire regimes in the lowland Neotropics are affected both by anthropogenic land use practices and natural climate variability. In Central America it is widely recognized that fire has been used as an agricultural tool for thousands of years, but the role of anthropogenic ignition as a determinant of past biomass burning frequency and magnitude has been debated. Little is known about the effects of short-term climate variability on fire regimes in this region of the world because of both the low temporal resolution of the available charcoal records and the obfuscating effects of anthropogenic burning throughout the late Holocene. Here we reconstruct 1400 years of fire history and environmental change on Ometepe Island, Lake Nicaragua, and perform statistical wavelet analysis on multiple proxy records to identify natural cycles of environmental variability possibly related to climate forcing. Our results indicate that extensive indigenous burning and landscape modification largely mask any climate signal in the paleo-fire record from AD 580 to 1400, with the exception of the period AD 775—1000 where high wavelet power exists at scales of 2—24 years. This time period coincides with a severe, two-century long regional drought that has been identified at other locations in Central America. High wavelet power at climate-relevant scales after ~AD 1400 in the Ometepe fire record suggests that periodic drought possibly caused by the El Niño Southern Oscillation and/or high-frequency solar cycles may have played a significant role in influencing the post-contact fire regime — a role that is largely concealed in the pre-European strata because of the overriding effects of anthropogenic burning.

Description: Two lacustrine sediment cores from Oldevatnet in western Norway have been studied in order to produce a record of floods, mass-wasting events and glacier fluctuations during the last 7300 years. River floods, density currents and snow-avalanches have deposited distinct ‘event layers’ at the lake floor throughout this time interval. In this study, a novel approach has been applied to distinguish event layers from the continuous background sedimentation, using Rb/Sr-ratios from X-Ray Fluorescence data. Grain-size distribution and the sedimentological parameters ‘mean’ and ‘sorting’ were used to further infer the depositional processes behind each layer. Our data suggest a record dominated by snow-avalanches, with the largest activity occurring during the ‘Little Ice Age’ (LIA). This increase in snow-avalanche activity observed during the LIA was probably caused by a combination of generally increasing winter precipitation and the advance of local glaciers towards the steep valley sides. Several fluctuations in snow-avalanche activity are also recognized prior to the LIA. Proxies of glacial activity from the background sediments indicate a similar development as earlier palaeoclimatic reconstructions from the area. It differs from previous reconstructions, however, by suggesting a lower glacial activity in the period from 2200 to 1000 cal. yr BP.

Description: Most recent developments of Schmidt-hammer exposure-age dating (SHD) as a calibrated-age dating tool have been limited by the use of locations at two age control points. This has necessitated: (1) making assumptions about a linear R-value—age relationship; and (2) basing predictions of age errors only on R-value variance at the two age control points. This paper analyses 9900 R-values obtained from multiple-age control points on a sequence of glacio-isostatically raised shorelines with well constrained ages (Skuleskogen High Coast World Heritage Site and environs, Gulf of Bothnia, northern Sweden) ranging from modern to 10.5 ka in age. The sampling design involved 30 measurements on granite beach boulders from 30 sites at 11 age control points. The R-value—age relationship is best described by a linear function (ordinary least squares, OLS) with an R 2 of 0.89 ( p 〈 0.0001). Predicted-age errors are calculated using two approaches: (1) OLS regression, which takes account of the uncertainties associated with the regression line and the age control points; and (2) weighted total least squares (WTLS) regression which, in addition, takes account of possible shoreline age errors and the heteroscedasticity of R-value residuals with increasing age. With both approaches, 95% predicted-age errors are relatively modest: ±355—455 years and ±300—515 years, respectively, with larger R-value variance and hence uncertainty for older surfaces, and the possibility of further improvement from a more selective field sampling scheme that differentiates between age-related and non-age-related rock-surface variability. Our results also indicate that for certain lithologies and weathering environments, it is possible to construct reliable calibrated-age curves from relatively few age control points.

Description: We used a network of eight pedunculate oak ( Quercus robur L.) sites ( n trees = 70) and one Scots pine ( Pinus sylvestris L.) site ( n trees = 53) to develop drought-sensitive master chronologies for the two areas in southern Scandinavia: a SW-area centred on 57°N 12.7°E and a NE-area centred on 58.8°N 18.2°E. The ratio of actual to equilibrium evapotranspiration (AET/EET) was used as a measure of drought during the growing season defined as the period with average daily temperatures above 9°C. Instrumental data were used to parameterize the relationship between tree-ring data and the drought index (DI) over 1922—2000 for the SW area and over 1922—1995 for the NE area. The DI reconstructions explained 29.7% (SW area) and 43.7% (NE area) of the variance in the observed DI index in the calibration period, and were extended back to AD 1770 for the SW area and to AD 1750 for the NE area. Reconstructed drought dynamics suggested strong decadal- and century-scale temporal variability and limited regional synchronicity over 1770—2000. Large variations in DI were observed in both regions in the second half of the 1700s. Dry conditions were synchronously reconstructed in both sub-regions during 1781—1784, 1853—1855, and, to a lesser degree, during 1974—1978. Over the 1945—1975 period the SW area exhibited a trend towards drier growing seasons, whereas no such trend could be identified for the NE area. Analysis of correlation maps indicated that regional DI dynamics reflected two different climate regimes, associated with the Kattegat area (SW reconstruction) and southeastern Swedish coast of the Baltic sea (NE reconstruction).

Description: A marine sediment core from Vaigat in Disko Bugt, West Greenland, has been analysed in terms of lithology, dinoflagellate cysts and foraminifera in order to evaluate the influence of oceanographic variability on West Greenland glacier stability. The data show that during the past 5200 years the Atlantic foraminiferal abundance in the subsurface waters of the West Greenland Current (WGC) episodically increased, indicating periods of increases in the inflow of subsurface warm Atlantic water at 2000—1500 cal. yr BP and 1300 cal. yr BP as well as periods of less pronounced increased bottom-water temperatures around 4700—4000 cal. yr BP, 3100—2800, 2600, 1000—800, 500—400, and at 200 cal. yr. The sedimentological and dinoflagellate cyst data indicate that these episodes with enhanced advection of Irminger Sea-derived waters are accompanied by increased iceberg rafting, which we link to increased iceberg calving in relation to destabilization of the Jakobshavn Isbrae. The long-term trend in the data documents the end of a late-Holocene Thermal Maximum between 5200 and 4300 cal. yr BP and a final onset of the Neoglaciation at 3500 cal. yr BP. Increased responses of the iceberg rafting after 3500 cal. yr BP, reflects a westward/seaward advance of the glacier margin in relation to onset of Neoglaciation and a development of the glacier into a floating tongue after 2000 cal. yr BP. A comparison of our record with a record from the eastern North Atlantic indicates that a NAO-like anomaly pattern between subsurface waters in West Greenland and atmospheric temperature in the Eastern North Atlantic may have been operating during most of the late Holocene. However, during the past 1000 years the NAO signal may have weakened as some other mode of climate variability overprints the anti-phase climate signal in this region.

Description: The coastal area of Jableh, in the vicinity of the Saladin and Al-Marquab castles, is a fertile alluvial plain located on the northwestern part of Syria, in what was once the crusader Principality of Antioch. In order to detail the coastal environment during the crusader period in the Middle East, palynological analyses have been conducted on the underlying coastal-alluvial deposits. The recovered sediments represent a continuous record of the environmental history of the area spanning a c. AD 850—1850 cal. yr period, from the Muslim Era up to and including the late Ottoman times. During the local crusader period (AD 1100—1270), the area was dominated by an arborescent mattoral mixed with a xerophytic shrub-steppe. The alluvial plain was slightly waterlogged and colonized by a wetland meadow with an open vegetation of steppe-like character on bare surfaces and fresh arable soils. The riparian and open deciduous riverine forests were weakly developed. Signs of agricultural activities are mainly recorded for the High Medieval period (AD 1000—1300), with an increase of vineyards in the coastal area. Since c. AD 1250 cal. yr until the end of the crusader period, agricultural activities never reached the same intensity as during the Mameluke Sultanate and the Ottoman Empire.

Description: In this work a detailed geomorphological study aimed to reconstruct the Holocene evolution of a slope largely affected by landsliding is presented. The study area is located in the lower valley of the Tanagro River, flowing in the Auletta basin, a Pliocene to Quaternary tectonic depression located along the elongation axis of southern Apennines. In order to investigate the relationships between landscape evolution and triggering factors, and to better constrain the Holocene palaeoclimate scenario in which the mass movements occurred, geomorphological data have been integrated with those deriving by the stratigraphic, chronological, and minero-geochemical analyses of the deposits genetically related to the landslide events. The investigated landslide shows a complex style of activity, with compound rotational and translational slide in the upper part of the slope evolving into flow in the lower part. The chronological evolution of the landslide activity has been constrained through radiocarbon dating of palustrine deposits, genetically related to the landslide, and of interbedded paleosols. On the basis of the presented data, the main landslide event can be placed at the beginning of the Holocene and it is followed by a period of scarse landslide activity, as demonstrated by the sedimentation of palustrine deposits within an endorheic pond. As the small basin was created by a counterslope rotation related to the main landslide phenomenon, its deposits post-date the age of the landslide. The geomorphological features related to the main gravitative event are strongly modified by reactivations occurred at the beginnings of Sub-Boreal period, which represent, in southern Europe, the warmest and wettest stage of the Holocene. As confirmed by mineralogical and geochemical data, intense and/or prolonged precipitation might have played a major role as triggering factor in reactivating the slope movement.

Description: We developed a composite oxygen isotopic record of cave calcite for the last 1860 years based on three stalagmites from the Huangye Cave in eastern Gansu Province, northern China. The 18 O values reflect monsoon precipitation changes, with lower 18 O values representing higher precipitation and vice versa . Three intervals of high precipitation were identified at AD 138—450, AD 730—1200, and AD 1860—1960. Two intervals of low precipitation occurred at AD 1320—1410 and AD 1530—1860. The reconstructed monsoon precipitation variations correlate well with other records further east in the eastern Yellow River Basin, suggesting synchronous precipitation changes during the late Holocene in the semi-humid region of northern China on decadal to centennial scales. Peak periods of warfare in dynastic transition times, such as at AD 391—420, AD 601—630, AD 1111—1140, AD 1351—1380, and AD 1621—1650, correspond to sharp declines in precipitation or temperature in semi-humid northern China, indicating a strong connection between climatic and societal changes. Our study suggests that climatic deterioration in semi-humid northern China has played an important role in Chinese societal evolution.

Description: We used pollen assemblages to reconstruct late-Holocene paleohydrologic patterns in floodplain deposits from the lower Roanoke River basin (North Carolina, southeastern USA). Using 120 surface samples from 38 transects, we documented statistical relationships between pollen assemblages, vegetation, and landforms. Backswamp pollen assemblages (long hydroperiods) are dominated by Nyssa (tupelo) and Taxodium (cypress) and have high pollen concentrations. Sediments from elevated levees and seasonally flooded forests (shorter hydroperiods) are characterized by dominant Pinus (pine) pollen, variable abundance of hardwood taxa, and low pollen concentrations. We apply the calibration data set to interpret past vegetation and paleohydrology. Pollen from a radiocarbon-dated sediment core collected in a tupelo-cypress backswamp indicates centennial-scale fluctuations in forest composition during the last 2400 years. Backswamp vegetation has occupied the site since land clearance began ~300 years ago. Recent dam emplacement affected sedimentation rates, but vegetation changes are small compared with those caused by pre-Colonial climate variability. The occurrence of wetter conditions from ~2200 to 1800 cal. yr BP, ~1100 to 750 cal. yr BP, and ~400 to 250 cal. yr BP may indicate changes in cyclonic circulation patterns related to shifts in the position of the Bermuda High and jet stream.

Description: The accumulation history of intertidal silty salt marsh sediments, from the northern shore of The Wash embayment (eastern UK), has been investigated along two cores, using a multiproxy approach involving visual logging, grain size measurements, as well as determination of particulate elements concentrations and 137 Cs, 210 Pb activities. The cores were collected in the high marsh area; one core was collected on the marsh platform, whilst the other was collected 5 m from the edge of a creek. Grain size distribution reveals two distinct silty sand layers within the lower parts of both cores. One of these is thought to represent the well-documented 1953 storm surge catastrophic event. A second silty sand horizon, found in the core located closer to the creek, is interpreted as being a later storm surge deposit produced in 1978. The redox states of both cores are similar and oxic conditions throughout are inferred from geochemical variations. The absence of a redox interface along the sediment column implies regular oxygen penetration during tidal cycles, thereby limiting the post-depositional mobility of 137 Cs and 210 Pb. The Caesium-137 distributions, in both of the cores, show a broad hump shape; these activities are interpreted as being largely affected by marine inputs from Sellafield. 210 Pb dating is used as an independent chronometer that confirms 137 Cs dating. Following the 1978 storm event, the mean accumulation rates, considering 137 Cs and 210 Pb radionuclide data and the discrete coarse-grained marker horizons, are 0.75 ± 0.09 g/cm 2 per yr (nominally 1.00 ± 0.11 cm/yr) close to the creek edge and 0.46 ± 0.04 g/cm 2 per yr (nominally 0.74 ± 0.10 cm/yr) on the marsh platform. Storm erosion is followed by moderately high accumulation rates.

Description: In the first modern pollen trapping study conducted in the Galápagos Islands, 58 clusters of pollen traps were established on four islands: Genovesa, Rocas Bainbridge, Santa Cruz, and San Cristobal. HOBO data loggers collected temperature, humidity, and dew point every 30 min for 1 year at eight locations. The trapping locations were selected to provide a wide diversity of Galápagos habitat types and to support active or future analyses from bog and lake core records recovered from the islands. Pollen influx to the traps was generally low (〈100 grains/cm 2 per yr), but broad habitat types were clearly identifiable based on the pollen collected. More precise identification of trapping sites and vegetation zones within the islands were identified using ordinations of the pollen and climate data. Long-distance dispersal from the mainland and neighboring islands were found to be significant elements of pollen records, particularly those where local pollen production was low (〈150 grains/cm 2 per yr). Over-representation and under-representation of ecological dominants was documented, as was the significant representation of invasive exotic species in some settings. Temperature and relative humidity data were used to reconstruct the presence of ground-level cloud (garúa). Garúa caused substantial cooling, beyond what would be expected from adiabatic lapse rate, in the highlands. The cloud formation associated with garúa caused low-elevation temperatures to be cooler than maximum sea-surface temperatures. The data emphasize the importance of garúa to the endemic flora of the islands and their long-term conservation.

Description: Previous palaeoclimatic studies in the northeastern Qinghai-Tibetan Plateau (NETP) during the Holocene, mainly using lake sediments, have deepened our understanding of the climatic system in this remote region. The timing and forcing mechanisms of climatic change in this region are still controversial, however. Aeolian sand and silt deposits, which are widely distributed in the NETP, can be readily dated by optically stimulated luminescence (OSL) techniques and reveal the sensitive response of the landscape to climatic change. In this study, aeolian sand and loess at six sites around Qinghai Lake were studied to reconstruct millennial-scale climatic changes during the Holocene. Multiproxy data along with 24 OSL age determinations show that low effective moisture and aeolian activity occurred at c . 13 ka, 10—9.1 ka, and 8.9—7.8 ka. Periods of greater effective moisture may have occurred at ~11 ka and 9 ka, and there is evidence for a previously undocumented wet climate at 4—3 ka. These results show that millennial-scale Holocene palaeoclimatic changes in the NETP cannot be explained simply as direct responses to changes in monsoon precipitation forced by summer insolation. We suggest that changes in effective moisture were determined by the balance between monsoon-induced rainfall and evaporation loss (mainly controlled by temperature). Thus, climatic change in the NETP may have been influenced by complex interactions between the monsoon circulation and local convection/evaporation effects, in addition to large-scale change in the Asian monsoon and the westerlies.

Description: The late Holocene in the central Ebro Depression is characterized by a number of morphodynamic stages that affected hillslopes and channels. Climate fluctuations and human activities together caused severe erosion and floods, resulting in alternating stages of accumulation and incision in the valley floors. Seven accumulation levels (N6-N0) correlated with Ebro River fluvial terraces have been identified in the secondary fluvial network of the central Ebro Depression. The main accumulation level (N3) corresponds to a long period of increased hillslope erosion and sedimentation in the valleys, from the Neolithic to the late Roman periods. The accumulation levels are evident throughout the valleys and extend to the valley mouths, where many connect with alluvial fans. The study of several sedimentological profiles, 14 C AMS dating, and many archaeological remnants, have enabled detailed assessment of sedimentation characteristics in the alluvial fans and the relationship thereof to the presence of human settlements. Four sedimentation stages have been identified: (i) pre-Bronze Age (〉 3800 years BP), (ii) Bronze Age/Iron Age (3800-2500 years BP), (iii) Roman/post-Roman period (2500-1500 years BP), and, (iv) the early Middle Ages, mainly during the Visigothic period (sixth century). The sedimentation dynamics of the alluvial fans are related to: (i) climate variability, (ii) human activities in the watershed, and (iii) the meandering character of the Ebro River, which has lateral displacements that change the local base level of tributaries and fans. Level N3 in the valley floors corresponds to stages i-iii of the alluvial fans, which are mostly related to human-induced transformation of characteristics of the secondary basins, coinciding with enhanced erosion under favorable (warm and humid) climatic conditions. In contrast, the Medieval stage, which corresponds to level N2 in the valleys, was caused by floods during a period of high climatic variability.

Description: High-resolution records of nitrate (NO 3 – ), oxygen isotope ( 18 O) and non-sea salt sulphate (nssSO 4 2– ) were studied using an ice core collected from central Dronning Maud Land in East Antarctica to identify the influence of environmental variability on accumulation of NO 3 – over the past 450 years. The results confirmed that multiple processes were responsible for the production and preservation of NO 3 – in Antarctic ice. Correlation between NO 3 – and nssSO 4 2– peaks revealed that sulphate aerosols released during major volcanic eruptions might have activated the production of nitric acid, which was scavenged by ion-induced nucleation in polar ice sheets. The correlation between the nitrate and 18 O records further suggest that enhanced NO 3 – preservation in the ice occurred during periods of lower atmospheric temperature. Major shifts in the NO 3 – record of the ice core presently studied and its comparison with 10 Be record from a core collected from South Pole suggest that a reduction in solar activity influenced the NO 3 – accumulation in Antarctica through enhanced production of odd nitrogen species.

Description: Much of western North America saw higher temperatures and lower precipitation during the middle Holocene. The Great Basin became much drier and warmer than it is today, causing major shifts in lake levels, treelines, plant community composition, and vertebrate distributions and abundances. To assess the impact of climate change on middle-Holocene human population densities in this region, we examine the frequency structures of radiocarbon-dated archaeological sites through time in three separate parts of the Great Basin: the Bonneville Basin, Fort Rock Basin, and western Lahontan Basin. The results of the analysis support the hypothesis that human population densities in many parts of the Great Basin dropped substantially in response to middle-Holocene climate change but also document that there were intervals during the middle Holocene in all three areas that appear to have been marked by temporary population increases. We hypothesize that these increases were associated with equally temporary increases in effective precipitation but, lacking adequate paleoenvironmental data, do not attempt to test this hypothesis.

Description: The largest debris-covered glacier in the Alps (Miage Glacier, western Italian Alps) has been studied to explore the effects of debris-cover extent and depth on the spatial distribution of ground-dwelling arthropods. A multitaxa approach has been used to compare taxa richness and distribution to the functional role (dietary habits) of each taxon along the glacier tongue. Spiders and ground beetles have been studied in detail. Taxa richness declines with distance from the wooded sites (in front of the glacier tongue) to those above the glacier tongue. At each of the supraglacial sites, spiders, ground beetles, aphids, springtails and flies were found. A change in the dominance of the different functional roles was observed along the tongue. Wooded sites are characterised by predatory (e.g. spiders, beetles), detrivore (e.g. springtails and certain flies), phytophagous (e.g. aphids, certain beetles) and parasitoid (e.g. certain wasps) assemblages, whereas at the debris-covered sites, aphids, flies and springtails are likely to be prey for spiders and beetles. The species richness of the predominant predators (spiders and beetles) shows a positive relationship with vegetation cover and debris thickness. Two mutually exclusive spider and ground beetle assemblages were found; one within the debris cover and one within the wooded sites. In our opinion, debris-covered glaciers are acting as a refuge area for the cryophil stenotherm species living at higher altitudes which descend the glacial tongue to lower elevations. A similar hypothesis supports the biogeographical interpretation of the distribution of many boreo-alpine relict species in the Alps. We discuss our results in the light of possible future scenarios which suggest an increase in debris cover with global warming.

Description: New data have allowed us to extend a previous height-increment chronology of Scots pine ( Pinus sylvestris L.) at the northern Fennoscandian timberline 817 years backwards in time, from 1561 to 745. Our final transfer model accounts for 31% of the dependent instrumental (mean June—August) temperature variance between 1908 and 2007. According to the 1263 yr long summer temperature proxy, the most severe summers were experienced in 1601, 1790 and 782. Correspondingly, the summers of 1689, 885 and 1123 were the most favourable for growth. Two drastic shifts in temperature variability were also found. The twentieth century experienced a multidecadal change as the cold 1905—1914 period was immediately followed by a warm period from 1915 to 1944. An even more prominent shift occurred in the Middle Ages, as the most severe cold spell during 1135—1164 was preceded by the warmest period only a decade earlier, during 1115—1124. The Fourier spectrum of the reconstruction shows significant concentrations of variance around 33.3, 23.3 and 11 years, and between 2.6 and 3.0 years. The wavelet spectrum was able to date several centres of fluctuating periodicities between 745 and 2007. Furthermore, daily temperature records allowed us to define the major growth forcing climatic factor in more detail than in previous response analyses. The mean temperature during a 53 day season from 14 June to 6 August produced the strongest positive growth response ( r 2 = 0.36).

Description: Rockfalls fundamentally affect the morphodynamics of high mountain rockwalls, and represent a great danger for both people and infrastructures, but still are poorly known. By comparing old, recent and new photographs, in addition to geomorphological field data, we propose an inventory of the rockfalls that occurred since the end of the ‘Little Ice Age’ on the north side of the Aiguilles de Chamonix (Mont Blanc massif), ranging in volume from 500 to 65 000 m 3 . These 42 rockfalls occurred after 1947, of which 〉 70% during the last two decades, with a maximal frequency during the warm summers, especially in 2003. Average elevation of scars (3130 m a.s.l.) close to the lower modelled permafrost limit, and the topography (e.g. spurs) of the affected rock faces enhancing lateral heat fluxes, suggest that a climatically driven permafrost degradation has triggered many of the recent rockfalls in high-Alpine steep rockwalls.

Description: Reconstructing specific fire-history metrics with charcoal records has been difficult, in part because calibration data sets are rare. We calibrated charcoal accumulation in sediments from three medium (14—19 ha) and one large (4250 ha) lake with a 300 yr tree-ring-based fire-history reconstruction from central Yellowstone National Park (YNP) to reconstruct local fire occurrence and area burned within a 128 840 ha study area. Charcoal peaks most accurately reflected fires within 1.2—3.0 km of coring sites, whereas total charcoal accumulation correlated best with area burned within 6.0—51 km ( r 2 =0.22—0.62, p 〈0.05). To reconstruct area burned for the entire study area, we developed a statistical model based on a composite charcoal record. The model explained 64—79% of the variability in area burned from AD 1675 to 1960 and was robust to cross-validation. Reconstructed area burned from AD 1240—1975 was significantly higher during periods including extreme annual drought ( p =0.05), and area burned varied significantly at ~ 60 yr timescales ( p 〈0.05), similar to the variability in an independent precipitation reconstruction covering the same period. Widespread burning (〉10 000 ha) occurred at 150—300 yr intervals, and at the site level, fire probability increased with stand age (composite Weibull c parameter = 1.61 [95% CI 1.36—2.54]), both suggesting that post-fire stand development played an important intermediary role between climate and fire by increasing fuel abundance and probability of fire spread. Our study illustrates the possibility of reconstructing area burned with multiple charcoal records, and results imply that future fire regimes in YNP will be governed by direct impacts of altered moisture regimes and by vegetation dynamics affecting the abundance and continuity of fuels.

Description: In the light of the currently increasing drought frequency and water scarcity on oceanic islands, it is crucial for the conservation of threatened insular vertebrates to assess how they will be affected. A 4000 yr old fossil assemblage in the Mare Aux Songes (MAS), southwest Mauritius, Mascarene Islands, contains bones of 100 000+ individual vertebrates, dominated by two species of giant tortoises Cylindraspis triserrata and C. inepta , the dodo Raphus cucullatus , and 20 other vertebrate species ( Rijsdijk, Hume, Bunnik, Florens, Baider, Shapiro et al. (2009) Mid-Holocene vertebrate bone Concentration-Lagerstätte on oceanic island Mauritius provides a window into the ecosystem of the dodo ( Raphus cucullatus ). Quaternary Science Reviews 28: 14–24). Nine radiocarbon dates of bones statistically overlap and suggest mass mortality occurred between 4235 and 4100 cal. yr BP. The mortality period coincides with a widely recognized megadrought event. Our multidisciplinary investigations combining geological, paleontological and hydrological evidence suggests the lake was located in a dry coastal setting and had desiccated during this period. Oxygen isotope data from a Uranium-series dated stalagmite from Rodrigues, an island 560 km east of Mauritius, supports this scenario by showing frequently alternating dry and wet periods lasting for decades between 4122 and 2260 cal. yr BP. An extreme drought resulted in falling water-tables at MAS and elsewhere on the island, perhaps deprived these insular vertebrates of fresh water, which led to natural mass mortalities and possibly to extirpations. In spite of these events, all insular species survived until at least the seventeenth century, confirming their resistance to climatic extremes. Despite this, the generally exponential increase of combined human impacts on islands including loss of geodiversity, habitats, and stocks of fresh water, there will be less environmental safe-haven options for insular endemic and native vertebrates during future megadrought conditions; and therefore will be more prone to extinction.

Description: The environmental evolution, inferred from the sedimentary sequence, that has occurred during the last three millennia in a drained coastal marsh in the Tiber delta is presented. The stratigraphy of the sediments has been revealed through excavation of 7 km of trenches in an area of about 1.5 km 2 . The most evident environmental variations are represented by the transformation of freshwater marshes into brackish-water marshes, around the ninth–eighth centuries bc , and from brackish-water to freshwater marshes during the fourteenth–fifteenth centuries ad . The change in the water salinity was produced by the opening and closure of an inlet connecting the marshes and the sea because of the evolution of the delta. Other environmental variations are reflected in the fluctuations in the water level of brackish marshes: in a general trend towards an increase in water level, probably caused by the late-Holocene sea level increase, some phases of water decrease in the range of 10–20 cm occurred. The majority of the environmental changes were largely produced by erosion and sedimentary events connected with Tiber delta variations induced both by human impact and climate. The lower water levels were contemporary with glacial advances in the Alps and the Apennine chains. At least one of the five decreases of the water level was contemporaneous with a marine regression documented in Italy.

Description: Understanding the processes controlling peatland carbon (C) sequestration is critical to anticipate potential changes in the global C cycle in response to climate change. Although identification of these factors may be relatively straightforward on seasonal timescales, at centennial to millennial timescales complexities arise because of interactions between climate, vegetation, hydrology and long-term ecological processes. To better understand the factors controlling long-term C accumulation, Holocene rates of C sequestration were quantified from three pristine ombrotrophic peatlands in boreal Quebec, northeastern Canada (52°N, 75–76°W). Bulk density and loss-on-ignition analyses, combined with radiocarbon dating and age–depth modelling, were used to estimate long-term apparent rates of carbon accumulation. Past changes in vegetation and water-table depth were obtained from plant macrofossil and testate amoeba analysis. Earliest regional peat accumulation started ~7520 cal. BP, with long-term rates of C sequestration varying between 14.9 and 22.6 g/m 2 per yr. High C sequestration rates occurred during the mid Holocene when relatively stable Sphagnum section Acutifolia communities were present, while low rates were found during the cooler late Holocene when Cyperaceae and ligneous vegetation were more dominant. However, C sequestration was highly variable among cores, implying that local topography, geomorphology and hydrology, or disturbance factors such as fire, mediate the influence of climate on C accumulation. Reconstructed water-table depths reveal several dry shifts since 3000 cal. BP, suggesting that episodic cold and dry conditions during the late Holocene may have contributed to lower C sequestration rates. Given the intensity of the water-table shifts at these times, we hypothesize that recurrent episodes of frozen subsurface peat might have intensified surface drying. As projected by climate scenarios, anticipated warmer and wetter conditions may lead to greater stability of hummock Sphagna cover and increased C sequestration potential in boreal peatlands.

Description: Sediment records from closed-basin lakes in the Northern Great Plains (NGP) of North America have contributed significantly to our understanding of regional paleoclimatology. A high-resolution (near decadal) fossil diatom record from Kettle Lake, ND, USA that spans the last 8500 cal. yr BP is interpreted in concert with percent abundance of aragonite in the sediment as an independent proxy of groundwater flow to the lake (and thus lake water level). Kettle Lake has been relatively fresh for the majority of the Holocene, likely because of the coarse substrata and a strong connection to the underlying aquifer. Interpretation of diatom assemblages in four groups indicative of low to high groundwater flow, based on the percent of aragonite in sediments, allow interpretations of arid periods (and probable meromictic lake conditions) that could not be detected based on diatom-based salinity reconstructions alone. At the centennial–millennial scale, the diatom record suggests humid/wet periods from 8351 to 8088, 4364 to 1406 and 872 to 620 cal. yr BP, with more arid periods intervening. During the last ~ 4500 years, decadal–centennial scale periods of drought have taken place, despite the generally wetter climate. These droughts appear to have had similar impacts on the Kettle Lake hydrology as the ‘Dust Bowl’ era droughts, but were longer in duration.

Description: This paper presents a paleoenvironmental reconstruction of historical development in the area of the ancient harbor of Claudius based on micropaleontological and sedimentological data. Benthic foraminifera are reliable tools for this kind of research because they are sensitive to short-time environmental changes induced by both natural and anthropogenic events. By studying eight sediment cores collected from different sections of the harbor, it was possible to reconstruct a comprehensive picture of the harbor complex. Qualitative and quantitative analysis of foraminiferal associations and sedimentological data, along with radiocarbon dating, were useful to identify three key intervals in the history of the coastal area where the harbor developed. The first interval, located at the bottom of all cores, is characterized by a brackish water environment, corresponding to the formation of the first deltaic cusp of the Tiber River. The second interval is characterized by the harbor activities that developed after a general increase in water depth due to a diversion of the Tiber River mouth. The third interval marks the final phase of harbor activities and the subsequent filling of Claudius’ basin. However, a link with the inner Trajanus’ basin was maintained via the central part of the basin, which remained submerged longer, until the early Middle Ages.

Description: We propose that the Anthropocene be defined as the last c . 2000 years of the late Holocene and characterized on the basis of anthropogenic soils. This contrasts with the original definition of the Anthropocene as the last c . 250 years (since the Industrial Revolution) and more recent proposals that the Anthropocene began some 5000 to 8000 years ago in the early to mid Holocene (the early-Anthropocene hypothesis). Anthropogenic soil horizons, of which several types are recognized, provide extensive terrestrial stratigraphic markers for defining the start of the Anthropocene. The pedosphere is regarded as the best indicator of the rise to dominance of human impacts on the total environment because it reflects strongly the growing impact of early civilisations over much of the Earth’s surface. Hence, the composition of anthropogenic soils is deemed more appropriate than atmospheric composition in providing ‘golden spikes’ for the Anthropocene.

Description: The house mouse invasion of the European continent has crucial implications for our understanding of the synanthropization process of European small mammals during the Holocene. Mice remains collected from a Chalcolithic burnt house in southern Romania, provided a unique opportunity to document which of the two house mouse subspecies was the commensal taxa of the late Neolithic Romania and question the factors of its invasive process. To obtain the subspecific status of the Mus remains, we performed molar shape analysis with geometric morphometrics, using 160 specimens sampling the extant Eastern European Mus taxa as modern comparatives. Along with an overwhelming majority of eastern house mice ( Mus musculus musculus ) living constantly in the Chalcolithic house, indigenous small mammals (common hamster, field mice, voles and white toothed shrews) were also occupying the settlement sporadically, highlighting the antiquity of the synanthropisation of European small mammals. This secured occurrence of the eastern house mouse in late Neolithic Romania, led us to propose two testable research hypotheses: first, an eastern house mouse commensalism center in Eastern Europe happening during the sixth millennium bc , when neolithization reached the natural distribution of free living populations of Mus musculus musculus in the Pontic steppes of Ukraine; second, new trajectories of trading networks, stimulated by copper metallurgy around the fifth millennium bc , having allowed long-distance translocation of the commensal eastern house mouse from Eastern to Southern Europe Neolithic settlements.

Description: The pattern of Holocene palaeoclimatic change in arid-semiarid northern China is debated. The terminal Huangqihai Lake is located at the northern margin of the modern East Asian summer monsoon and sensitive to climate change. We present here a sedimentary section from Huangqihai lake basin which comprises lacustrine and fluvial deposits and is about 8–9 m above the present lake level. Quartz optically stimulated luminescence (OSL) dating was employed to construct the chronology of the section. Based on the OSL chronology and the sedimentological and granulometric analysis, we conclude that (1) the Huangqihai Lake experienced a humid climate during the early part of the Holocene (from c . 10.2 ± 1.0 to 6.7 ± 0.7 ka) with a persistent and stable high lake level; (2) the lake level began to decline indicating aridification between 8.7 ± 0.8 ka and 6.7 ± 0.7 ka, and the climate was drier and variable after 6.7 ± 0.7 ka compared with that of before; (3) from 2.2 ± 0.2 to 0.93 ± 0.07 ka the climatic conditions were highly variable and continuously deteriorating, and the lake was turned into a playa for most of the time. In summary, the climate showed a general drying trend from the early Holocene to the late Holocene.

Description: There has been a sustained need to quantify past climate changes from proxy records to better understand the driving mechanisms and thus to improve the prediction of the future. Transfer function is an intuitive and frequently used method in this regard. However, this method is unable to provide interpretive and predictive results from proxy records, because physical processes are not included. The inverse proxy modelling method opened up a new avenue for quantitative palaeoclimate reconstructions through the integration of proxy records with deterministic models. It is fundamentally different from the statistical approach, representing a conceptual advance in quantitative palaeoclimatology. Here we demonstrate the potential of this method by placing a mechanistic model and a 6000 year long peat cellulose 18 O record obtained from the high-cold and monsoonal eastern Tibetan Plateau ( c. 3500 m a.s.l.) in a Bayesian paradigm. In this worked example, the marginal posterior probability distributions of palaeoclimate variables such as the 18 O of soil water, temperature, and relative humidity were inferred jointly through the solution to an ill-posed inverse problem using the Markov chain-Monte Carlo method. Our results indicate that the observed variation of the peat cellulose 18 O record in this monsoonal area essentially reflects the changes in the oxygen isotopic composition of soil water, which is closely linked to that of rainfall. Compared with hydrology, temperature and humidity have little influence on the oxygen isotope fractionation of leaf water.

Description: High-resolution climate reconstructions from a range of natural archives across the world are fundamental to place current climate change into perspective. Paleoclimate records for the Southern Hemisphere are scarce and only a few quantitative high-resolution reconstructions exist for the past millennium. We present a record of annually laminated sediments of Lago Plomo (46°59'S, 72°52'W,203 m a.s.l.) located east of the Northern Patagonian Ice Field (NPI). Radiometric dating ( 210 Pb, 137 Cs, 14 C AMS) is consistent with counts of millimetre-scale laminae, confirming the annual nature of the laminae couplets with a light summer and a dark winter layer. The varves were analyzed for thickness, mass accumulation rate (MAR), scanning x-ray fluorescence (XRF) and scanning reflectance spectroscopy in the visible range (VIS-RS). MAR data were calibrated against austral winter (JJA) precipitation data (CRU TS 3.0) for the period ad 1930–2002 ( r = 0.67, p (aut) 〈 0.05). Using a linear inverse regression model we reconstructed winter precipitation for Lago Plomo back to ad 1530. The root mean squared error of prediction (RMSEP) is small (13.3 mm/month; 12% of the average precipitation) compared with the pronounced decadal and multidecadal variability, suggesting that most of the reconstructed variability is significant. Wetter phases (reference ad 1930–2002) were observed around ad 1600, ad 1630–1690 and ad 1780–1850, and a prolonged drier period ad 1690–1780 with a multidecadal minimum centered on ad 1770. The spatial correlation for South America suggests that the JJA precipitation record from Lago Plomo is representative for large areas in the southwest between c . 41°S and 51°S.

Description: Taupo volcano in central North Island, New Zealand, is the most frequently active and productive rhyolite volcano on Earth. Its latest explosive activity about 1800 years ago generated the spectacular Taupo eruption, the most violent eruption known in the world in the last 5000 years. We present here a new accurate and precise eruption date of ad 232 ± 5 (1718 ± 5 cal. BP) for the Taupo event. This date was derived by wiggle-matching 25 high-precision 14 C dates from decadal samples of Phyllocladus trichomanoides from the Pureora buried forest near Lake Taupo against the high-precision, first-millennium ad subfossil Agathis australis (kauri) calibration data set constructed by the Waikato Radiocarbon Laboratory. It shows that postulated dates for the eruption estimated previously from Greenland ice-core records ( ad 181 ± 2) and putative historical records of unusual atmospheric phenomena in ancient Rome and China ( c . ad 186) are both untenable. However, although their conclusion of a zero north–south 14 C offset is erroneous, and their data exhibit a laboratory bias of about 38 years (too young), Sparks et al. (Sparks RJ, Melhuish WH, McKee JWA, Ogden J, Palmer JG and Molloy BPJ (1995) 14 C calibration in the Southern Hemisphere and the date of the last Taupo eruption: Evidence from tree-ring sequences. Radiocarbon 37: 155–163) correctly utilized the Northern Hemisphere calibration curve of Stuiver and Becker (Stuiver M and Becker B (1993) High-precision decadal calibration of the radiocarbon timescale, AD 1950–6000 BC. Radiocarbon 35: 35–65) to obtain an accurate wiggle-match date for the eruption identical to ours but less precise ( ad 232 ± 15). Our results demonstrate that high-agreement levels, indicated by either agreement indices or 2 data, obtained from a 14 C wiggle-match do not necessarily mean that age models are accurate. We also show that laboratory bias, if suspected, can be mitigated by applying the reservoir offset function with an appropriate error value (e.g. 0 ± 40 years). Ages for eruptives such as Taupo tephra that are based upon individual 14 C dates should be considered as approximate only, and confined ideally to short-lived material (e.g. seeds, leaves, small branches or the outer rings of larger trees).

Description: The slopes in Northern Iceland show the widespread occurrence of solifluction features, indicative of an active periglacial environment due to annual mean temperatures around 3°C at sea level and seasonal soil frost. In order to reconstruct periods with active and inactive solifluction in the past we excavated 18 solifluction lobes for analysing the sediment sequences. Dating of the sediments was realised mainly by tephrochronology and 14 C. The oldest solifluction layer could be dated to the Younger Dryas (YD), just after the deglaciation of Northern Iceland. The early to mid Holocene up to the deposition of Hekla 3 Tephra (~3 ka BP) is characterized by the accumulation of loess and tephra layers, which show no signs of secondary remobilisation or erosion, indicating stable slopes during the mid-Holocene climatic optimum (MCO). After the deposition of Hekla 3 Tephra and especially during the ‘Little Ice Age’ (LIA), solifluction reappeared in the profiles as a probable consequence of Neoglacial cooling. The results fit well with other proxies from Iceland (glacier variations, pollen), from North Atlantic marine cores and from Greenland ice records.

Description: Diatom assemblages from Holsteinsborg Dyb on the West Greenland shelf were analysed with high temporal resolution for the last 1200 years. A high degree of consistency between changes in frequency of selected diatom species and instrumental data from the same area during the last 70 years confirms the reliability of diatoms (particularly sea-ice species and warm-water species) for the study of palaeoceanographic changes in this area. A general cooling trend with some fluctuations is marked by an increase in sea-ice species throughout the last 1200 years. A relatively warm period with increased influence of Atlantic water masses of the Irminger Current (IC) is found at ad 750–1330, although with some oceanographic variability after ad 1000. A pronounced oceanographic shift occurred at ad 1330, corresponding in time to the transition from the so-called ‘Medieval Warm Period’ (MWP) to the ‘Little Ice Age’ (LIA). The LIA cold episode is characterized by three intervals with particularly cold sea-surface conditions at ad 1330–1350, ad 1400–1575 and ad 1660–1710 as a result of variable influence of Polar waters in the area. During the last 70 years, two relatively warm periods and one cold period (the early 1960s to mid-1990s) are indicated by changes in the diatom components. Our study demonstrates that sedimentary records on the West Greenland shelf provide valuable palaeoenvironment data that confirm a linkage between local and large-scale North Atlantic oceanographic and atmospheric oscillations.

Description: The integration of sedimentary facies, pollen, spores, carbon and nitrogen isotopes records, C/N ratio and radiocarbon dates allowed the identification of changes in vegetation and the sources of organic matter accumulated on tidal flats near the mouth of the Amazon River during the mid and late Holocene. Data from the margin of Amazon River indicate marine influence related to mangrove presence over a tidal mud flat between 5560–5470 cal. yr BP and 5290–5150 cal. yr BP. Afterward, the mangrove area shrank following the return of more humid conditions and increase of Amazon River discharge. A common reworking process of the tidal flat through the lateral migration of a meandering creek occurred in the study site, with later development of transitional vegetation under freshwater influence. Following the natural vegetation succession under stable climate and hydrological conditions, the expansion of ‘várzea’ (flooded freshwater vegetation) forests occurred since 600–560 cal. yr BP until the present. Furthermore, regarding the tidal flats located west of the mouth of Amazon River, these stable conditions also allowed the mangrove maintenance over mudflats with deposition of marine organic matter during at least the last 2350–2300 cal. yr BP.

Description: This study aims to estimate relative pollen productivity (PPEs) of major pollen types and the relevant source area of pollen (RSAP) in a semi-open landscape in western Norway. Extended R-value (ERV) models are used to analyse a data set consisting of surface pollen assemblages from 34 lakes and vegetation survey around each site. Ordination techniques indicate relatively short gradients (〈2.3 SD) both in the vegetation and pollen data sets. The lake sizes vary from 0.4 ha to 19.0 ha (mean=5.7 ha, sd=4.3 ha) but follow a normal distribution – a departure from the assumption of the ERV models that the lake size should be constant among sites. Simulations demonstrate that, if the sizes of circular-shaped lakes follow a normal distribution, the ERV model-based methods provide the expected PPE and RSAP values using a standardized lake radius. If the distribution is highly skewed or equally random around the mean, the results are not reliable. We apply the analytical strategy implied from the simulations to obtain relative PPEs and the RSAP in western Norway. PPEs for ten taxa ( Alnus , Fagus , Picea , Pinus , Quercus, Juniperus , Salix , Calluna , Cyperaceae, Rumex ) relative to Poaceae are comparable with some of those previously obtained in different parts of Europe, indicating that there are general patterns of high and low pollen producers that will be useful for reconstruction purposes. The RSAP estimate is the area within a radius of 900–1100 m. This study demonstrates the importance of careful evaluation of the extent to which the departures from the model assumptions affect the outcomes from the ERV model-based analysis.

Description: Based on radiocarbon dating and our analysis of plant and animal remains from Buziping, a Majiayao (5300–4300 BP) and Qijia (4200–3800 BP) period site located in Dingxi, Gansu Province, China, and our review of archaeobotanical studies in the Western Loess Plateau and adjacent areas, we discuss subsistence strategies during the Majiayao and Qijia periods. We also discuss the development of agriculture in the Western Loess Plateau and its influence on cultural expansion during the late Neolithic period. Humans settled at Buziping for the first time during the Majiayao period (4890–4710 cal. yr BP by 14 C dating). Charred seeds from the site indicate that people engaged in millet-based agricultural production. People continued this type of agriculture during a second phase of occupation (4130–3880 cal. yr BP by 14 C dating) during the Qijia period, but the proportion of foxtail millet to broomcorn millet increased from the Majiayao to Qijia period. Raising domestic animals was another aspect of subsistence during the Qijia period. The main domestic animals were likely pigs and dogs, although hunting of wild animals also took place. Subsistence at Buziping site was affected by the rapid development of intensive agriculture that diffused across eastern Gansu Province during the late Neolithic. Our work suggests that millet-based agriculture spread from east to west across the Western Loess Plateau and likely promoted the expansions of those two cultures in the area during the Majiayao period and early–mid Qijia period. Climate change might have also promoted Majiayao and Qijia expansions and probably facilitated the adoption of rain-fed agriculture in this region.

Description: We evaluated the potential of maize pollen concentrations in lake sediment profiles to serve as indicators of the extent of prehistoric agriculture in neotropical lake basins using records from a network of five sediment cores recovered from Laguna Zoncho, Costa Rica. The watershed of this small (0.75 ha) lake in the Diquís archaeological region has a c . 3000 year history of prehistoric agriculture and subsequent forest recovery, as documented through previous studies of pollen, charcoal, diatoms, and phosphorus fractions in a single core recovered from the center of the lake. In our new network of cores, we compared maize pollen concentrations with two independent proxies for the scale of agriculture in the same cores: abundance of organic matter (OM), which is an indicator of soil erosion, and bulk sediment stable carbon isotope ratios of organic matter ( 13 C OM ), which reflect the proportion of forested and cleared land within the watershed. In none of the five cores did maize pollen concentrations correspond with either OM or 13 C OM , suggesting that sedimentary maize pollen concentrations are not sensitive to the scale of maize agriculture in small neotropical watersheds. We found maize pollen in relatively high concentrations in two of the four cores taken near the lakeshore, but the others contained little or no maize pollen. The core from the center of the lake consistently recorded maize pollen, a finding that we attribute to sediment-focusing processes.

Description: The absence of accurate sea-level index points in SW Europe has long precluded the development of Holocene sea-level curves and the correct understanding of tectonic activity. In order to understand the coastal evolution and the major drivers in the Minho area, Portugal, we have combined micropaleontological and sedimentological data, where the chronological framework is provided by 13 radiocarbon ages. The stratigraphic reconstruction is in agreement with regional models of evolution and provides new sea-level index points that support a regional isostatic model producing the first complete Holocene sea-level curve from this area. Field data and model reconstructions present a good agreement for the region considered and vertical land movement estimates derived from the isostatic model are in agreement with GPS vertical velocities. At regional scale, our results support a north–south trend for SW Europe, where isostatic rebound seems to be minimized in the south of the Iberian Peninsula while local factors (sedimentation, local geomorphology, etc.) tend to dominate during the late Holocene. This newly produced sea-level curve has helped to improve isostatic model predictions and provide pre-anthropogenic sea-level rise rates against which modern rates can be compared.

Description: We surveyed and dated the former shorelines of one lake in the Shackleton Range and two lakes in the Pensacola Mountains, situated inland of the Weddell Sea embayment Antarctica between 80° and 85°S. These are amongst the highest latitude lakes in the Antarctic and are located in areas where there is little or no Holocene climate and hydrological information. Surveys of the lake shorelines show that past water levels have been up to 15.7, 17.7 and 69.5 m higher than present in the three study lakes. AMS radiocarbon dating of lake-derived macrofossils showed that there was a sustained period of higher water levels from approximately 4300 and until sometime after 2250 cal. yr BP. This is interpreted as being the result of an increased number of meltwater events and/or degree-days above freezing, relative to the present. The closest comparable ice cores from the Dominion Range in the Transantarctic Mountains (85°S, 166°E) and the Plateau Remote ice core on the continental East Antarctic Ice Sheet (84°S, 43°E) also provide some evidence of a warmer period beginning at c . 4000–3500 yr BP and ending after 2000–1500 yr BP, as does a synthesis of oxygen isotope data from five Antarctic ice cores. This suggests that the well-documented mid- to late-Holocene warm period, measured in many lake and marine sediments around the coast of Antarctica, extended into these regions of the continental interior.

Description: A new compilation of historical observations and archaeomagnetic measurements of magnetic inclination for the last 1000 years from eastern Australia (the eastern Australian Inclination Record [ eAIR2012 ]) has revealed the existence of a well-defined inclination anomaly in the region. Evidence of this magnetic feature has been preserved in sedimentary records from across eastern Australia, though this has not previously been recognised. Analyses of additional sedimentary sequences have confirmed the incidence and timing of this feature, revealing its presence between the 13th and 18th centuries ad . The inclination of the field during this episode appears to have been steeper than at any time since the start of the Holocene. Lake sediment evidence suggests that the anomaly is a composite feature, displaying a distinct peak at cal. ad 1270–1386 (±2 uncertainty), reappearing after cal. ad 1431–1651 (±2 uncertainty) and disappearing before cal. ad 1822±46 (±2 uncertainty). The disappearance of the anomaly is tightly bracketed in the historical record between ad 1770 and 1777. The rapid shift in inclination during the 18th century ad offers considerable potential as a means of dating a critical period of Australian environmental history, an episode that currently lies beyond the reach of established dating methods. This information also provides a valuable constraint on models of regional geomagnetic field change over centennial and millennial timescales. Our examination of the historical record has revealed that the inclination measurements made by the 18 th -century French explorer La Pérouse are consistently erroneous. Since La Pérouse’s data make up 13% of the total body of pre-19th century inclination records, the inclusion of these measurements in global compendia of magnetic observations may seriously skew attempts to model the geomagnetic field. We advocate that La Pérouse’s inclination measurements should therefore be employed only with considerable caution.

Description: The Höfðahólar rock avalanche, in the Skagafjörður area of northern Iceland, was investigated on the basis of a geomorphological analysis of its landforms and close surrounding environment. Thanks to sound chronological constraints ( 14 C dating from birch remnants in peat areas that developed within depressions over the chaotic rock-avalanche deposit, tephrochronological sequences resulting from subsequent ash fallouts over the deposit, calibration of an age–depth model of peats and previously dated raised beaches), we define the rock-avalanche implementation with a wider timeframe between 10,200 and 7975 cal. yr BP and with a narrower frame between 9000 and 8195 ± 45 cal. yr BP. Such a well constrained timing proposes one of the most precise datings of an early-Holocene major slope failure in Iceland. This result fits well in the known chronology of the deglaciation in this area and in the prevailing Icelandic theory of a generalized phase of landsliding that occurred shortly after the deglaciation of the area. The main driver for the rock-avalanche occurrence is associated to a paraglacial origin; glacio-isostatic rebound, associated to rockwall debuttressing, is thought to be the main factor in the genesis of this Boreal major disequilibrium.

Description: During Holocene advances of the Bear River Glacier, in northwestern British Columbia, ice pushed against a bedrock slope on the north side of Bear River Pass as it was being diverted eastward and westward along the pass. The result is a series of till sheets plastered against the rock slope and separated by wood mats. This sequence of tills provides an unusually detailed record of early-Neoglacial history and shows that Neoglacial expansion in the northern Coast Mountains began earlier than previously known. Moraines show the extent of ‘Little Ice Age’ expansion, and documents related to the long mining history of the area provide records of post-LIA recession. The oldest deposits in the area are a small lateral moraine outside of a prominent LIA moraine, and a till in the pass older than c . 3500 14 C yr BP. The small moraine is undated; it may be equivalent to the latest-Pleistocene Crowfoot Advance which produced similar moraines in the southern Coast Mountains and eastern Cordillera. Wood mats in the pass show that Neoglacial advances occurred at c . 3700, 3500, 3300, and 1000 14 C yr BP; each advance was slightly more extensive than the previous one. Documentary evidence indicates that the pass was still filled with ice in 1913, and diverging both eastward and westward, but glacier retreat has been rapid since then. Retreat from the pass in the mid-20th century resulted in the creation of Strohn Lake, through which meltwater from the glacier passes; a complicated lake history includes switching of discharge from eastward to westward and a series of jokuhlaups that damaged highway infrastructure to the west. A comparison of the history recorded at Bear River Pass with that recorded at the Todd Icefield 15 km to the north shows that different components of glacial history are preserved in different places, and many sites need to be examined to obtain a relatively complete regional history.

Description: We report on a sediment record from a small lake within the subarctic wetland complex Stordalen in northernmost Sweden covering the last 1000 years. Variations in the content of minerogenic material are found to follow reconstructed variations in the activity of the Sun between the 13th and 18th centuries. Periods of low solar activity are associated with minima in minerogenic material and vice versa. A comparison between the sunspot cycle and a long instrumental series of summer precipitation further reveals a link between the 11 yr solar cycle and summer precipitation variability since around 1960. Solar minima are in this period associated with minima in summer precipitation, whereas the amount of summer precipitation increases during periods with higher solar activity. Our results suggest that the climate responds to both the 11 yr solar cycle and to long-term changes in solar activity and in particular solar minima, causing dry conditions with resulting decreased runoff.

Description: We describe the analysis of existing and new maximum-latewood-density (MXD) and tree-ring width (TRW) data from the Torneträsk region of northern Sweden and the construction of 1500 year chronologies. Some previous work found that MXD and TRW chronologies from Torneträsk were inconsistent over the most recent 200 years, even though they both reflect predominantly summer temperature influences on tree growth. We show that this was partly a result of systematic bias in MXD data measurements and partly a result of inhomogeneous sample selection from living trees (modern sample bias). We use refinements of the simple Regional Curve Standardisation (RCS) method of chronology construction to identify and mitigate these biases. The new MXD and TRW chronologies now present a largely consistent picture of long-timescale changes in past summer temperature in this region over their full length, indicating similar levels of summer warmth in the medieval period (MWP, c . ce 900–1100) and the latter half of the 20th century. Future work involving the updating of MXD chronologies using differently sourced measurements may require similar analysis and appropriate adjustment to that described here to make the data suitable for the production of un-biased RCS chronologies. The use of ‘growth-rate’ based multiple RCS curves is recommended to identify and mitigate the problem of ‘modern sample bias’.

Description: The annual and seasonal temperatures in the Arctic over the past 1150 years are analyzed in simulations performed with the three-dimensional Earth system model of intermediate complexity LOVECLIM forced by changes in solar irradiance, volcanic activity, land use, greenhouse gas concentrations and orbital parameters. The response of the system to individual forcings for each season is examined in order to evaluate the contribution of each forcing to the seasonal contrast. For summer, our results agree relatively well with the reconstruction of Kaufman et al. (2009). Our modelling results suggest that the temperature changes during this period were characterized by large seasonal differences. In particular, while annual mean temperatures display a decreasing trend during the pre-industrial period, spring temperatures appear to rise. The variations in the Earth’s orbital parameters are the main cause for those seasonal differences. Larger climate variations are simulated in autumn compared with the other seasons in response to each forcing, particularly in response to changes in greenhouse gas concentration during the industrial period and in response to land use forcing, which surprisingly has a significant impact on Arctic temperature. These contrasting changes for the different seasons also underline the need for an adequate estimate of the season represented by a proxy.

Description: Benthic foraminiferal assemblages from a core southwest of Disko Bugt provide a Holocene perspective (last ~7 ka BP) on ice-sheet/ocean interactions between the West Greenland Current (WGC) and the West Greenland ice sheet. Changes in the fauna reveal significant variations in the water mass properties (temperature and salinity) of the WGC through time. From 7.3 to 6.2 ka BP, a relatively warm/strong WGC influences ice-sheet melt in Disko Bugt and causes enhanced meltwater production, resulting in low surface-water productivity. The most favourable oceanographic conditions occur from 5.5 to 3.5 ka BP, associated with ‘thermal optimum-like’ conditions, encompassing minimum ice sheet extent in the Disko Bugt area. These conditions are attributed to: (1) reduced meltwater influence as the ice sheet is land based and (2) enhanced contribution of warm/saline water masses from the Irminger Current to the WGC. The transition into the late Holocene (last ~3.5 ka BP) is characterized by a cooling of oceanographic conditions, caused by increased advection of cold/low-salinity water masses from the East Greenland Current. A longer-term late-Holocene cooling trend within the WGC is attributed to the onset of Neoglacial cooling within the North Atlantic region. Superimposed on this cooling trend, multicentennial-scale variability within the WGC matches reconstructions from a nearby coring site in Disko Bugt as follows: (1) cooling at ~2.5 ka BP, linked to the 2.7 ka BP ‘cooling event’; (2) a warm phase centred at 1.8 ka BP, associated with the ‘Roman Warm Period’; (3) slight warming between 1.4 and 0.9 ka BP, linked to the ‘Medieval Climate Anomaly’; (4) severe cooling of the WGC after 0.9 ka BP, culminating at 0.3 ka BP during the ‘Little Ice Age’. We show that multicentennial-scale palaeoceanography variability along the West Greenland margin is driven by ocean forcing, i.e. variations in the relative contribution of Atlantic (Irminger Current) and Polar (East Greenland Current) water masses to the WGC during the last ~7 ka BP, influencing ice sheet dynamics.

Description: In semi-arid ecosystems where lacustrine sediments are rare, bio-proxies preserved in fluvial deposits are needed to understand environmental changes. In this study, we evaluate the potential of phytoliths as a bio-proxy in the Yamé River’s deposits at Ounjougou (Mali, West Africa) covering the middle to late Holocene (7790–4000 cal. BP). In soils, phytolith assemblages result mainly from decomposition of local vegetation but in alluvial deposits, the taphonomy of phytoliths is more complex, depending on the type of transport and deposition. In order to define the spatial origin of the phytolith assemblages, either from local (valley floor) or regional vegetation (catchment area), we took the sedimentary characteristics of the deposits into account. Using a combination of general and index approaches, phytoliths of 14 modern and 29 fossil samples from the Yamé valley were analyzed. The predominant source area of represented phytoliths varies with the fluvial energy of transport. Channel deposits, carried during periods of strong fluvial activity, contain higher numbers of savanna grass phytoliths and display a lower ratio of dicotyledon versus Poaceae phytoliths (D/P) than those deposited in the floodplain where phytoliths from the local gallery forest are more strongly represented. From the 5th millennium BP onwards, higher percentages of grass short cell phytoliths (GSCP) and lower D/P values point to gradual vegetation opening due to increasing aridity. High amounts of burned phytoliths show regular fire incidence in the gallery forest and attest for human impact on the landscapes of Ounjougou from the 7th millennium BP onwards. After 4500 cal. BP, there is evidence for pearl millet cultivation.

Description: Despite many studies of Holocene paleoclimate records from small lakes in the mid-continent of North America, direct estimates of lake-level changes associated with mid-Holocene aridity are rare. Varved sediments from Elk Lake, Clearwater County, Minnesota, are among the best studied in terms of paleoenvironmental proxies, yet the sedimentary architecture of those sediments has not been previously studied and the hydrological responses of the lake – changes in level and volume – are poorly known. High-resolution seismic-reflection (CHIRP) profiles of Elk Lake reveal complex sedimentary basins in the lake, a pattern of nearshore onlap of sediments onto older substrates, and the focusing of sediments into several deep basins. Biogenic gas obscures sediments in the deepest parts of the basins, but beneath the rest of the lake, a three-part Holocene sequence is clear. The transitions between these parts are correlated with lithological changes defined in earlier core studies. Sediments of the modern stage are less focused than those of the prairie lake stage. A prominent erosional unconformity occurs within the Holocene sequence, separating sediments from the prairie and modern stages of the lake. Erosion associated with this unconformity extends to a depth of 18.2 m below the modern water surface, at which point the unconformity grades into a conformable horizon within the sequence in the deep basins of the lake. This transition is an analog of the onlap of modern sediments onto older substrates, which occurs at a depth of about 8.2 m. The configuration of the erosional unconformity and its modern analog indicates a lake-level fall in the mid Holocene of 10.0 m. At its mid-Holocene minimum, the lake was 39% of its present size and 30% of its present volume, providing quantitative evidence to aid in constraining and evaluating reconstructions of mid-Holocene aridity in the mid-continent of North America.

Description: Species distribution models are widely used by ecologists to estimate the relationship between environmental predictors and species presence and abundance records. In this paper, we use compiled faunal assemblage records from archaeological sites located across southwest Asia and southeast Europe to estimate and to compare the biogeography of ancient wild and early domestic cattle ( Bos primigenius and Bos taurus ). We estimate the contribution of multiple environmental parameters on the explanation of variation in abundance of cattle remains from archaeological sites, and find that annual precipitation and maximum annual temperature are significant predictors of abundance. We then formulate, test, and confirm a hypothesis that states the process of cattle domestication involves a change in the types of environmental ranges in which cattle exploitation occurred by applying a species distribution model to presence-only data of wild and domestic cattle. Our results show that there is an expansion of cattle rearing in more temperate environments, which is a defining characteristic of the European early Neolithic.

Description: The scale, spatial variability and implications of pre-Columbian human-induced changes in the Amazon basin are controversial. While some scholars believe that large settlements and complex societies were limited to areas with favourable environmental conditions and human disturbance was localized, others propose that social complexity developed regardless of environmental constraints and opportunities and that human disturbance was widespread. In order to understand the extent to which environmental preconditions influenced the development of pre-Columbian societies, research is needed that integrates both environmental reconstructions and archaeological data. The present study explores past human–environment interactions in the Llanos de Moxos (LM) in the Bolivian Amazon. Combining extensive fieldwork and remote sensing image analysis, we reconstruct mid- to late-Holocene fluvial activity in the southeastern LM and the formation of a sedimentary lobe left by the Grande River. The lobe deposition created the conditions for the development of fertile, drained soils. We also show how pre-Columbian inhabitants adapted to the sedimentary lobe and managed to maximize the area of land suitable for agriculture by building a drainage/irrigation infrastructure. Our results provide an interpretative framework for the diversity of archaeological remains in the LM and suggest that people reached high levels of social complexity as a result of two necessary factors: favourable environmental conditions and human ingenuity.

Description: Three alluvial units, ranging from the middle to late Holocene in age, were distinguished in Bardenas Reales Natural Park (Ebro Basin, NE Spain) based on morphosedimentary analysis and radiocarbon data. In this sensitive Mediterranean alluvial system, the succession and isotopic composition of gastropods greatly contribute to establishing the prevailing palaeoenvironmental conditions. The oldest unit (4763±87 to 2848±55 cal. yr BP) represents fluvial channels and swamped areas, includes the greatest proportion of aquatic gastropods ( Ancylus fluviatilis and Lymnaea truncatula ) and marsh species ( Vallonia pulchella ) and presents the most negative values of 18 O (mean –2.21 PDB). The intermediate unit (1403±60 to 836±65 cal. yr BP) shows a high rate of alluvial activity related to irregular torrential rainfall, with sedimentary features of aridity, and this unit includes only dry open ground gastropods ( Xeroplexa sp., Chondrinidae indet. and Granopupa granum ) and presents the least negative values of 18 O (mean –1.17 PDB). The youngest unit (191±97 to 127±82 cal. yr BP) exhibits a recurrence of flooding events, mostly includes marsh ( Truncatellina callicratis and Lauria cylindracea ) and aquatic ( Lymnae truncatula ) species and shows a very heterogeneous isotopic signal, with –1.83 PDB as the mean value of 18 O. As a consequence, a palaeoenvironmental pattern comprised of an early wetter/colder phase followed by a warmer/drier period and, finally, an increase in both cold conditions and hydrological variability, is deduced for the middle to late Holocene in the Ebro Basin. Gastropod shell 13 C values, related to vegetation, can also be linked to palaeoenvironmental changes. The succession and stable isotope composition of gastropods in alluvial sequences are revealed as very sensitive indicators of rapid Holocene climatic changes in fragile semi-arid landscape systems.

Description: The mid-Holocene behaviour of five glaciers in the British Columbia Coast Mountains was reconstructed from radiocarbon ages and stratigraphic analysis. Subfossil wood evidence at Canoe, Fyles, Jacobsen, Tchaikazan and Icemaker glaciers suggests these glaciers were expanding into standing forests prior to 6630, 4900 and 4200 cal. yr BP. Stratigraphically constrained woody detritus at Fyles Glacier records the progradational history of a Gilbert-type delta forming in response to glacial expansion between 7020 and 5470 cal. yr BP. This research provides the first evidence for mid-Holocene glacial expansion in the central and northern British Columbia Coast Mountains. Proxy records describing mid-Holocene climates in the British Columbia Coast Mountains indicate a trend towards slightly cooler and possibly wetter conditions than present. Glacial expansion occurring between 7500 and 4000 cal. yr BP has regional correlatives, suggesting coherent broad-scale climate forcing mechanisms influenced glacial mass balance at this time.

Description: Holocene glacier activity in the northern British Columbia Coast Mountains, Canada, is described following investigations in the recently deglaciated forefields of White and South Flat glaciers spilling from the Cambria Icefield. Glacially overridden stumps and detrital wood was radiocarbon and dendrochronologically dated to describe an advance between ad 250 and 650. Expansion and thickening of White Glacier by ad 765 resulted in creation of an ice-dammed lake in South Flat valley that persisted until ad 1080. Following this the lake drained, before refilling in the early ‘Little Ice Age’ prior to ad 1300. Shortly thereafter White and South Flat glaciers became confluent and flowed over the valley side toward White Lake. The characteristics of the site and the preservation of 1500 yr old deposits indicate that the two glaciers remained confluent throughout the remainder of the ‘Little Ice Age’, only separating following terminal retreat early in the 20th century. The late-Holocene glacial history of White and South Flat glaciers appears synchronous with those of other glaciers in northern portion of Pacific Northwest.

Description: This study presents a recontruction of the Holocene vegetation and fire history of the Serra do Caparaó (Espírito Santo/Minas Gerais, SE Brazil) based on pollen and charcoal analysis from the 130 cm long core Primeiro Rancho I. Radiocarbon dates indicate a complete record of the Holocene (11,400 cal. yr BP to present). At the core site, high elevation grassland (campos de altitude) has been the dominant vegetation throughout the recorded period. In the early Holocene (11,400 to 9000 cal. yr BP), a humid phase was followed by a drier one. Fires occurred continuously during the studied period but were more frequent in the early Holocene. Between 9000 and 2700 cal. yr BP, a gradual increase in the diversity and abundance of Atlantic montane forest taxa indicates an increase in humidity and/or rainfall; campos de altitude taxa still dominated but the montane forest taxon Symplocos was strongly present. Between 2700 and 1200 cal. yr BP, the arboreal Atlantic montane forest taxon Luehea became prominent but forest expansion halted and apparently reversed after 1200 cal. yr BP, possibly because of human activities. Simultaneously, campos de altitude expanded; abrupt variations in the pollen assemblages suggest environmental instability. Campos de altitude are a natural vegetation in Serra do Caparaó, but their present extent is likely influenced by anthropogenic activities, as several data suggest an increase of humidity after 1200 cal. yr BP, which should have caused a forest expansion. Reduction in human disturbance at higher elevations would thus probably result in succession to forest in some of the lower campos.

Description: This study presents a comprehensive assessment of high-resolution Southern Hemisphere (SH) paleoarchives covering the last 2000 years. We identified 174 monthly to annually resolved climate proxy (tree ring, coral, ice core, documentary, speleothem and sedimentary) records from the Hemisphere. We assess the interannual and decadal sensitivity of each proxy record to large-scale circulation indices from the Pacific, Indian and Southern Ocean regions over the twentieth century. We then analyse the potential of this newly expanded palaeoclimate network to collectively represent predictands (sea surface temperature, sea level pressure, surface air temperature and precipitation) commonly used in climate reconstructions. The key dynamical centres-of-action of the equatorial Indo-Pacific are well captured by the palaeoclimate network, indicating that there is considerable reconstruction potential in this region, particularly in the post AD 1600 period when a number of long coral records are available. Current spatiotemporal gaps in data coverage and regions where significant potential for future proxy collection exists are discussed. We then highlight the need for new and extended records from key dynamical regions of the Southern Hemisphere. Although large-scale climate field reconstructions for the SH are in their infancy, we report that excellent progress in the development of regional proxies now makes plausible estimates of continental- to hemispheric-scale climate variations possible.

Description: A late-Holocene alluvial sequence in north-central Texas has a 1 m thick buried cumulic soil with an A-C profile called the West Fork paleosol. It formed 2300 to 1000 yr BP and is a local equivalent of the Copan paleosol that is present throughout the southern US Great Plains. Stable carbon isotopes indicate that the paleosol and underlying gray clay formed under vegetation dominated by C 4 species (mean 13 C: –18.3 ± 0.3). Diverse paleoenvironmental studies indicate that the period of paleosol formation was cool and wet and that alluvial water-tables were high, resulting in broad wet meadows across alluvial valleys, characterized by communities of grasses. Present-day wet meadows and bottomlands with Mollisols with A-C profiles along streams in the Great Plains are dominated by C 4 tallgrass species and may serve as analogues to wet-meadow environments during the late Holocene. A shift in climate to warm-dry conditions about 1000 yr BP was accompanied by deep channel cutting, low alluvial water-tables, and colonization of abandoned floodplains by trees and other C 3 species, as indicated by a change in carbon isotopes to lower values (mean 13 C: –20.8 ± 0.5) and correlating with the ‘Medieval Warm Period’. Other stable carbon isotope studies from late-Holocene alluvium in Texas have been mistakenly interpreted as evidence for paleoenvironmental conditions opposite to those presented in this investigation. We conclude that interpretations of stable carbon isotopes from alluvium based on broad patterns of upland C 4 grasses and climate can be in error, especially in cases where wet-meadow deposits and soils are present.

Description: The impact of short-term climate anomalies and disturbances on past plant communities can be understood using high temporal or contiguous sedimentary pollen analysis. The response of pollen assemblages to decadal- to multidecadal-scale moisture variability was analyzed for the time intervals 3000–2200 and 1400–500 cal. yr BP. The hydroclimate and vegetation history for Minden Bog in southeastern Michigan were reconstructed using analyses of sedimentary testate amoebae and pollen. Results indicated that moisture anomalies accounted for 3% to 24% of the variation in arboreal pollen abundance for Fagus, Pinus, Quercus , and Tsuga. Betula pollen percentages did not appear to be affected by moisture variability. Given the longevity of these taxa, rapid arboreal pollen assemblage responses to moisture variability at decadal to multidecadal timescales were likely due to climate-induced changes in pollen productivity. Our data suggest that pollen–climate relationships may be counterintuitive at these fine temporal scales. For example, Tsuga pollen percentages generally increased during short-term dry events, in contrast to expected decreases in abundance with drying at millennial timescales based on empirical pollen–climate relationships. Results suggest caution should be used when inferring subdecadal to multidecadal climate variation from highly resolved pollen records. Rather, high-resolution pollen data may more accurately represent superimposed plant responses that are the composite of reproductive output nested within long-term plant community compositional changes in response to climatic variation.

Description: In the southern Duero Basin of central Spain, there are vast areas of aeolian sand sheets and dune fields. A comprehensive survey of the sand quarries in this area identified a number of palaeosols in sedimentary sequences. The identification and AMS radiocarbon dating of soil charcoal fragments collected in these palaeosols indicate the persistence of Pinus pinaster in this area throughout most of the Holocene. Although potential natural vegetation models have usually considered the Pinus pinaster forests in this inland area of artificial origin, soil charcoal analysis provides firm evidence of a natural origin. Our data fit perfectly with the pattern of Holocene vegetation development for inland areas of Iberia, which are characterised by stability of pine forests throughout the Holocene. Finally, the growing body of palaeobotanical evidence from Iberia (macrofossils and pollen) is contributing to improve our knowledge of P. pinaster ecology, showing that this species has been present in most Iberian regions during the Holocene, where it has inhabited areas characterised by a very diverse set of climatic and soil conditions.

Description: Climate proxy records and general circulation models suggest that Atlantic Meridional Overturning Circulation (AMOC) plays a key role for global climate changes. Paleoceanographic data document multiple episodes of prominent AMOC weakening during the early Holocene. However, proxy records at adjacent continents have not been demonstrated to fully capture the climate responses to multiple AMOC variation due to temporal resolution and/or the proxy sensitivity. Here we present decadal- to multidecadal-resolution hydrogen isotopic records of aquatic biomarkers from Blood Pond, Massachusetts during the early Holocene. Our data reveal a full series of prominent and abrupt cooling events centered on 10.6, 10.2, 9.5, 9.2, 8.8 and 8.4 ka. These abrupt climatic reversals coincide with key intervals of weakened AMOC, suggesting an apparent relationship between AMOC oscillations and the abrupt continental climate changes in northeastern North America. The noticeable connection implies that the AMOC variation did play an important role in the abrupt climate changes during the early Holocene. Our data also suggest that northeastern North America may experience significant climatic variations should the predicted major disturbance of AMOC occur in the coming century as a result of anthropogenic greenhouse gas emissions.

Description: Several studies indicate that changes in solar activity may have driven Holocene subtropical monsoon variability on decadal and centennial timescales, but the strength and nature of this link remains debated. In this study, we combine a recent mapping of the Holocene solar-cycle activity with four subtropical speleothem 18 O records, which allows a strong test of the link between solar activity, monsoon activity (or intensity), and the hydrological cycle. This is possible because the speleothem 18 O records mainly reflect changes in local rainfall composition, which is controlled by changes in total moisture loss along the atmospheric transport path and monsoon intensity. We find that the spectral density distributions of the speleothem records exhibit particularly significant ~210 yr cyclicities that tend to coincide in time with the three Suess solar-cycle bursts, i.e. intervals around 1850–3200 BP, 4500–5700 BP, and 7750–8850 BP when the ~210 yr solar cycle was particularly strong. The speleothems from Dongge Cave (China) and Sofular Cave (Turkey) appear to have recorded all three Suess bursts, whereas the speleothems from Heshang Cave (China) and Pink Panther Cave (southwestern USA) only recorded the first and last Suess bursts, and the middle Suess burst, respectively. The temporal relationship between the Suess solar cycle and particularly significant 210 yr oscillations in the speleothem 18 O records therefore supports the notion that solar variability played a significant role in driving centennial-scale changes in the hydrological cycle in the subtropics during the Holocene.

Description: An appropriate bioproxy is required to decipher Holocene tree biomass dynamics from the stand scale in relation to local processes such as disturbance or global climate change. Here we used plant litter collected in traps placed in subalpine forests, and data on the surrounding stands, to develop calibration equations for converting the observed macroremain accumulation rates to tree biomass (basal area) values. The needle accumulation rate (NAR) was modeled for Larix decidua and Pinus cembra . We then used the calibration equation developed from the trapped macroremains to reconstruct past tree biomass for sedimentary Holocene series from two subalpine lakes in the Alps. Our data show that NAR is significantly correlated with basal area. We found a clear overrepresentation of L. decidua NAR compared with its real basal area. This distortion potentially masks the occurrence of P. cembra , another important functional species of subalpine ecosystems, when macroremains are not calibrated. Without calibration, the use of NAR to describe past plant biomass always leads to an overestimation of L. decidua biomass and an underestimation of P. cembra biomass. Several shifts between the dominance of the two species, which were masked when using unadjusted NAR, were apparent and occurred at both sites. By comparing the reconstructed basal areas with fire frequencies, we found that P. cembra biomass accumulation preceded the increase of fire frequency and that fire frequencies superior to 0.0085 fire/yr could induce a long-term loss of resilience of cembra pine forest to the benefit of larch. This results to a slight dominance of Larix biomass from 2500 to 2000 cal. BP until the present day at the two sites. Our results provide increased understanding of tree biomass dynamics associated with specific vegetation phases, and shifts in dominant species, and highlight the needs to understand the causes of these shifts and identify how such processes are related to local environmental conditions.

Description: We derive a paleoflood chronology for the past 2000 years from three stratigraphic sections of overbank sediments with dates from radiocarbon, luminescence, 137 Cs techniques, and historical records. Particle sizes were measured in 6–15 year intervals in post-1870 sediments and in 45–170 year intervals in pre-1870 sediments using an automatic laser analyzer. The sedimentological characteristics of ad 1948–2009 deposits were compared with gaging records, demonstrating that fine sand content and sorting discern time intervals of large floods, but flood magnitudes are not well resolved. This modern analog was applied to pre-1870 sediments and revealed two periods in the last 2000 years with large floods during ad 650–850 and ad 1100–1350, which are times when the regional tree-ring record showed extreme wetness and no severe or extreme droughts. Our findings indicate flood-prone phases of transitional climate at the beginning and end of the ‘Medieval Warm Period’ (MWP), and relatively subdued flooding during the ‘Little Ice Age’ (LIA), possibly correlated with rearrangement of macro-scale atmospheric circulation patterns between the MWP and the LIA.