Reconstruction Of Past Climate Research Articles

Controlling the external moment arm at the knee allows better recovery after multiple slipping perturbations during gait

Global reconstructions of the Earth's Quaternary ice sheet history such as ICE-6G assume that mantle rheology is linear and Earth properties are laterally homogeneous. However, these assumptions are unrealistic because high temperature/pressure creep experiments show that both linear and non-linear creep laws operate simultaneously in the mantle. Also surface geology and seismic tomography show that mantle properties vary laterally. This study uses the Coupled Laplace-Finite Element Method to find an ice model that is consistent with an Earth model with composite rheology where both linear and non-linear creep laws operate simultaneously in the mantle, and the effective viscosity is laterally heterogeneous.We use the ICE-6G ice model as initial load on a composite rheology Earth model and iteratively improve both the ice and Earth model parameters until they fit observations of Glacial Isostatic Adjustment or GIA (relative sea level and land uplift rate) well simultaneously. We thereby focus on North America and northern Europe. Our best combination model, called ICE-C(M_C), also fits gravity rate-of-change data in both areas. This finding removes the obstacle in using composite rheology in GIA studies since previous work found it impossible for composite rheology to fit both relative sea level and land uplift rate data simultaneously. It shows that composite rheology is clearly an alternative to linear rheology in future GIA studies.The ICE-C model is at the last glacial maximum (LGM) position from 26 ka BP (thousand years before present) to 19 ka BP, which implies that composite rheology also supports the timing of LGM proposed by Clark et al. (2009). The model is found to be significantly thicker in the center of rebound in Fennoscandia than ICE-6G from the LGM to about 8 ka BP, but significantly thinner around the Fennoscandian coastline from LGM to about 12 ka BP. These changes in the lower boundary conditions in northern Europe may affect the reconstruction of past climate there. Regional differences in ice thickness between ICE-C and ICE-6G are also found in Laurentia. During LGM there are negligible differences in total ice volume between ICE-C and ICE-6G, thus it remains questionable if a composite rheology may help in solving the missing ice problem. ICE-C is also consistent with meltwater pulses 1A and 1B. Mantle viscosities and creep parameters of Earth model M_C are consistent with previous findings from GIA modeling and microphysics experiments.

Geochemical characteristics of dust aerosol availability in northwestern China

Based on field sample collections, wind tunnel experiments, and statistical analyses, the spatial differences of geochemical characteristics of dust aerosol availability originating from different landscapes in the Tarim Basin, Qaidam Basin, and Ala Shan Plateau of northwestern China were evaluated. Experiments and statistical analysis results showed that there are many differences in the geochemical characteristics of dust aerosol availability originating from above regions. Riverbeds, wadis and gobi deserts, and interdunes are the major landscapes for element emissions of dust aerosols in the Qaidam Basin, Ala Shan Plateau, and Tarim Basin, respectively. Among them, more than 60% of the elements such as Ti, Cr, Rb, Y, Nb, Ce, Nd, Pb, and Al2O3 in dust aerosol availability that originated from the Ala Shan Plateau and the Tarim Basin may play an important role in the element emissions in coarse fractions. Variations in the geochemical characteristics of dust aerosol availability caused by landscape and regional differences may play an important role in loess compositions and in past climate reconstructions that used post-depositional eolian sediments as a proxy.

From Leaf to Label: A robust automated workflow for stomata detection

Leaf stomata are microscopic pores on the leaves of plants which control the balance between water loss and CO2 uptake by the plant. As plants adapt their stomatal traits in response to environmental parameters such as water availability, temperature and atmospheric carbon dioxide concentrations, stomatal size and density of preserved leaves have allowed for reconstruction of past climates. Stomata serve as ‘gates’ between deep-soil water reservoirs and the atmosphere and are a key determinant of transpiration in models for operational predictions of the near-climate. It is well known that stomatal size and density vary widely across plant species and even though efforts have mapped stomatal behavior globally, more detail is needed as including more interspecific trait variation in climate models could significantly reduce the error in model predictions. Despite their important function, no standardized methodology has yet been described to measure stomatal traits which is widely considered to be labour-intensive and time-consuming and to this day mostly performed manually. Herbaria contain a treasure of unique ecological data covering large temporal scales. We used the African Herbarium of Meise Botanic Garden which contains over 1.2 million African specimens with a very good coverage of the Congo Basin (dating back to 1880) to develop a workflow for extracting stomatal trait data starting from the herbarium specimen, involving the automatic detection of stomata using a deep learning approach. The purpose of developing this workflow is to generate a large amount of data on stomatal traits on an easy, cost- and time- efficient manner. Here, we will present the leaf-to-label workflow and demonstrate how it was used to study the effect of global change on leaf adaptation in central African rainforest over the past 100 years.

Unravelling the oxygen isotope signal (δ18O) of rodent teeth from northeastern Iberia, and implications for past climate reconstructions

Small mammals, especially rodents, constitute valuable proxies for continental Quaternary environments at a regional and local scale. Recent studies have demonstrated the relation between the stable oxygen isotope composition of the biogenic phosphate from rodent teeth (δ18Op), and the oxygen isotope composition of meteoric waters (δ18Omw), which is related to air temperatures at mid and high latitudes. This work explores the δ18Op of rodent tooth enamel (from Murinae and Arvicolinae subfamilies) to investigate the palaeoenvironmental conditions in northeastern Iberia during Marine Isotope Stage 3 (MIS 3; ca. 60-30 ka). Fourteen new δ18Op analyses from modern samples in conjunction with forty-six δ18Op analyses previously published are used to decipher the isotope record of present-day rodent teeth in this region. Two main factors should be considered in Iberian palaeoenvironmental reconstructions: the singular nature of Iberian δ18Omw records and the potential seasonality bias of small-mammal accumulation. Methodological proposals are made with a view to ensuring the correct interpretation of the δ18Op of small mammals in reconstructing past air temperatures. This methodology is applied to the MIS 3 sequence of the Cova dels Xaragalls site (Vimbodí-Poblet, Tarragona, Spain), where fifty-one δ18O analyses were performed on wood mouse (Apodemus sylvaticus) lower incisors. A spring-early summer accumulation of small mammals is suggested for the layers at Cova dels Xaragalls. In agreement with previous environmental studies of the site, variations in the δ18Op values suggest slight fluctuations in the climatic conditions throughout the sequence, which are consistent with the stadial-interstadial alternations that characterized MIS 3. Complementary palaeoenvironmental methods determine cooler conditions than nowadays, but within a globally stable climatic period.

The climate of the past millennium and online public engagement in a scientific debate

AbstractAfter the publication in 1999 of a reconstruction of the Northern Hemisphere temperature popularly known as “the hockey‐stick,” climate scientists and Internet bloggers engaged in a heated and often stalemated public debate on the validity of paleoclimate reconstructions and on their implications for the wider question of anthropogenic climate change. The Internet emerged as an important medium for channeling the direct participation of the public almost at the same level as the professional climate scientist. It also allowed dissemination of largely unfiltered information. I argue that, although paleoclimate research did benefit in some technical aspects, the public debate around the hockey‐stick focused on issues that were not scientifically central, like the existence of the Medieval Warm Period or the characterization of 1998 as the warmest year of the millennium. In contrast, much more relevant points, such as constraining the value of climate sensitivity using reconstructions of past climate, remained restricted within purely academic circles. The public resonance of the hockey‐stick debate was also clearly framed by the politicization of climate science and the impacts of the series of IPCC reports, in particular the Third Assessment Report, published in 2001. This resonance was amplified by the expanding use of the Internet. The Internet represented a new bidirectional channel through which the public and academia could interact to achieve a transparent, democratic, and participative evaluation of science. I argue that, although we could have hoped for a positive outcome of the hockey‐stick controversy, this opportunity for a new constructive public engagement in scientific debates was missed.This article is categorized under: Paleoclimates and Current Trends > Paleoclimate Social Status of Climate Change Knowledge > Sociology/Anthropology of Climate Knowledge

In search of an ice history that is consistent with composite rheology in Glacial Isostatic Adjustment modelling

Global reconstructions of the Earth's Quaternary ice sheet history such as ICE-6G assume that mantle rheology is linear and Earth properties are laterally homogeneous. However, these assumptions are unrealistic because high temperature/pressure creep experiments show that both linear and non-linear creep laws operate simultaneously in the mantle. Also surface geology and seismic tomography show that mantle properties vary laterally. This study uses the Coupled Laplace-Finite Element Method to find an ice model that is consistent with an Earth model with composite rheology where both linear and non-linear creep laws operate simultaneously in the mantle, and the effective viscosity is laterally heterogeneous.We use the ICE-6G ice model as initial load on a composite rheology Earth model and iteratively improve both the ice and Earth model parameters until they fit observations of Glacial Isostatic Adjustment or GIA (relative sea level and land uplift rate) well simultaneously. We thereby focus on North America and northern Europe. Our best combination model, called ICE-C(M_C), also fits gravity rate-of-change data in both areas. This finding removes the obstacle in using composite rheology in GIA studies since previous work found it impossible for composite rheology to fit both relative sea level and land uplift rate data simultaneously. It shows that composite rheology is clearly an alternative to linear rheology in future GIA studies.The ICE-C model is at the last glacial maximum (LGM) position from 26 ka BP (thousand years before present) to 19 kaBP, which implies that composite rheology also supports the timing of LGM proposed by Clark et al. (2009). The model is found to be significantly thicker in the center of rebound in Fennoscandia than ICE-6G from the LGM to about 8 kaBP, but significantly thinner around the Fennoscandian coastline from LGM to about 12 kaBP. These changes in the lower boundary conditions in northern Europe may affect the reconstruction of past climate there. Regional differences in ice thickness between ICE-C and ICE-6G are also found in Laurentia. During LGM there are negligible differences in total ice volume between ICE-C and ICE-6G, thus it remains questionable if a composite rheology may help in solving the missing ice problem. ICE-C is also consistent with meltwater pulses 1A and 1B. Mantle viscosities and creep parameters of Earth model M_C are consistent with previous findings from GIA modeling and microphysics experiments.

The isotopic composition of meteoric water along altitudinal transects in the Tian Shan of Central Asia

The Tian Shan in Central Asia are a unique mountain range in that they are in the world's most continental location. Seasonal precipitation in the northern Tian Shan is segregated into distinct elevation bands where high elevations receive precipitation primarily during summer and low elevations to the north receive precipitation primarily during the late winter and spring. In this study, we sampled stream water along multiple altitudinal transects to determine the effect unique seasonal patterns of precipitation have on the isotopic composition of surface water. Our results suggest that the northern Tian Shan exhibits an isotopic lapse rate for waters sampled in late spring, but not for those sampled in late summer, when stream water budgets are dominated by high elevation precipitation and snow melt. Deuterium excess results suggest that subcloud evaporation significantly affects the isotopic composition of precipitation at low elevations in spring and that sublimation of snow has a minor impact on δ18O values of summer melt water. Because high and low elevation δ18O values are similar, conventional paleoaltimetry based on Rayleigh distillation of an air mass is not applicable to the Kyrgyz Tian Shan. Stream water proxies from the rock record are likely to reflect changes in the seasonal distribution of precipitation which occur on the same spatial scale as altitudinal changes. These results highlight the need to understand modern controls on local stable isotopes of meteoric water in reconstructions of past climate or topography using geologic proxy materials.

Climate Factors Leading to Asymmetric Extreme Capture in the Tree‐Ring Record

AbstractPaleoclimate data play a critical role in contextualizing recent hydroclimate extremes, but asymmetries in tree‐ring responses to extreme climate conditions pose challenges for reconstruction and interpretation of past climate. Here we establish the extent to which existing tree‐ring records capture precipitation extremes in western North America and evaluate climate factors hypothesized to lead to asymmetric extreme capture, including timing of precipitation, seasonal temperatures, snowpack, and atmospheric river events. We find that while there is dry‐biased asymmetry in one third of western North American tree‐ring records, 45% of sites capture wet extremes as well as or better than dry extremes. Summer extremes are rarely captured at any sites. Latitude and elevation affect site‐level extreme responses, as do seasonal climate conditions, particularly in the autumn and spring. Directly addressing asymmetric extreme value capture in tree‐ring records can aid our interpretation of past climate and help identify alternative avenues for future reconstructions.

Reconstructing carbonate alteration histories in orogenic sedimentary basins: Xigaze forearc, southern Tibet

Abstract Carbonate clumped isotope thermometry (T( Δ 47 )) and the oxygen stable isotope record ( δ 18 O ) provide critical constraints on the temperature of carbonate mineral formation and isotopic composition of ancient waters used in reconstructions of past climate, tectonics, and ecological and environmental change. The robust use of these proxies requires that carbonate minerals in the rock record retain primary isotopic compositions through often complex post-depositional thermal histories. New carbonate clumped isotope thermometry and sedimentology data are paired with existing thermochronology and isotope exchange reaction modeling to provide unique constraints on the alteration history of the carbon and oxygen isotopes in Tethyan marine carbonates (Jialazi Fm, Tso Jianding Group) of the Xigaze forearc, southern Tibet. Within the framework of the textural and isotopic data, the effects of early and late burial alteration on Δ 47 and δ 18 O values of marine rocks that were buried to 4 km above sea level are modeled. The alteration products are considered within two well-studied mechanistic frameworks: water-rock recrystallization and solid-state reordering of 13 C 18 O bonds at high temperature. The proposed alteration model is as follows: (1) shallow, early diagenesis with water of similar composition and temperature to formation waters infills primary porespace with microspar; (2) high-temperature, rock-buffered water-rock exchange and partial solid-state reordering at >3–4 km depth; and (3) near-surface, low-temperature water-rock exchange on the exhumation pathway. The Δ 47 heterogeneity within individual samples (0.456 to 0.721) requires significant differential alteration on the retrograde path (high to low temperature, low water-rock ratio) in which primary compositions and compositions inherited during early burial diagenesis are overprinted with modern meteoric values. A low T( Δ 47 ) value is often assumed to record the primary temperature of the depositional environment. However, samples yielding low T( Δ 47 ) values in the Jialazi Fm have undergone extensive high-temperature water-rock alteration, and therefore, require a mechanism for increasing 13 C 18 O bond ordering on the retrograde pathway while preserving many primary biogenic structures and micritic textures. This study highlights the potential significance of late-stage, low-temperature alteration of carbonates derived from orogenic sedimentary basins for studies of terrestrial paleoenvironments and tectonics. This study also provides an example framework for combining observational and analytical data to reconstruct a carbonate alteration history of a buried sedimentary package.

In situ X-ray tomography densification of firn: The role of mechanics and diffusion processes

One of the most efficient proxy methods for paleoclimatology consists of obtaining data previously preserved within polar ice cores. Models for past climate reconstruction are based in particular on the characterization of entrapped gases in ice closed pores. Improving the temporal accuracy of these models requires a better understanding of firn densification mechanisms. In particular, the interplay between viscoplastic deformation and diffusion processes for pore closure is not well understood. In this work, we describe the first in situ laboratory densification experiments on polar firn retrieved from Antarctica with live characterization by X-ray tomography. Our in situ tests allow for the first time to approximately access the process of pore closure in ice, which takes thousands of years to occur in Antarctica, from visualizations and quantitative analyses of short time laboratory experiments. The parameters of pore separation and closure and the microstructural changes that accompany them are monitored. We show that densification of polar firn and pore closure could be replicated at higher strain rate and warmer temperature. Experiments allow the viscoplastic part of the firn deformation to be decoupled from the diffusion mechanisms that occur at high temperature. Our results show that density alone is not sufficient to predict the close-off density at which gases get entrapped. More generally, the method laid out here may find useful application in the domain of high temperature powder compaction, for which pore closure and grain growth are significant process parameters.

Boron isotope systematics of cultured brachiopods: Response to acidification, vital effects and implications for palaeo-pH reconstruction

CO2-induced ocean acidification and associated decrease of seawater carbonate saturation state contributed to multiple environmental crises in Earth’s history, and currently poses a major threat for marine calcifying organisms. Owing to their high abundance and good preservation in the Phanerozoic geological record, brachiopods present an advantageous taxon of marine calcifiers for palaeo-proxy applications as well as studies on biological mechanism to cope with environmental change. To investigate the geochemical and physiological responses of brachiopods to prolonged low-pH conditions we cultured Magellania venosa, Terebratella dorsata and Pajaudina atlantica under controlled experimental settings over a period of more than two years. Our experiments demonstrate that brachiopods form their calcite shells under strong biological control, which enables them to survive and grow under low-pH conditions and even in seawater strongly undersaturated with respect to calcite (pH = 7.35, Ωcal = 0.6). Using boron isotope (δ11B) systematics including MC-ICP-MS as well as SIMS analyses, validated against in vivo microelectrode measurements, we show that this resilience is achieved by strict regulation of the calcifying fluid pH between the epithelial mantle and the shell. We provide a culture-based δ11B−pH calibration, which as a result of the internal pH regulatory mechanisms deviates from the inorganic borate ion to pH relationship, but confirms a clear yet subtle pH dependency for brachiopods. At a micro-scale level, the incorporation of 11B appears to be principally driven by a physiological gradient across the shell, where the δ11B values of the innermost calcite record the internal calcifying fluid pH while the composition of the outermost layers is also influenced by seawater pH. These findings are of consequence to studies on biomineralisation processes, physiological adaptations as well as past climate reconstructions.

Altitudinal patterns of wind transport and deposition of Yungas tree pollen in northwestern Argentina: Implications for interpreting the Quaternary fossil record

The presence of pollen from Yungas tree species in fossil sequences located above the tree-line has led to alternative interpretations of past climate changes in tropical and subtropical Andes. We studied atmospheric and surface pollen deposition rates of Yungas trees along an altitudinal gradient (1700–3800 m a.s.l.) to understand the role of local wind patterns in modern pollen transport to mountain regions. Pollen from the Montane forest (Alnus and Juglans) and the Montane rainforest (Anadenanthera, Celtis and Myrtaceae) becomes airborne and is transported upslope well above the tree-line. The resulting patterns of pollen deposition show a secondary maximum in the Montane grassland, consistent with the development of a mountain-valley breeze system during the flowering period of the pollen producer species. Given that the pattern is also preserved in the surface sediment, we propose that these tree pollen types are good indicators of mesoscale atmospheric circulation and could provide a proxy for this circulation system in Quaternary records. This alternative approach to interpreting fossil pollen records of Yungas species in highlands of the Central Andes has implications for regional reconstructions of past climate.

A complete Holocene climate and environment record for the Western Carpathians (Slovakia) derived from a tufa deposit

Calcareous tufas are great archives of geochemical information for the reconstruction of past climate. Their importance increases in the regions where other proxies are rare, such as Western Carpathians. Here, we present the first whole-Holocene palaeoclimatic reconstruction for this region based on geochemical proxies. We analysed δ18O, δ13C and Mg/Ca ratio on tufa calcite of the Mituchovci site (White Carpathian Mountains, W Slovakia) and compared these with pollen, plant macrofossil and mollusc data. According to δ18O, two distinct thermal maxima occurred in the region, around 11.4 ka and between 7.3 and 6.9 ka BP. According to δ13C and Mg/Ca ratio, a steep increase in moisture and rainfall took place around 8.5 ka cal. BP, preceded by a cold and dry event. These events are well reflected in the biotic proxies and are suggested also by other palaeoenvironmental studies from the Carpathians. We found some later fluctuations, with dry and warm Bronze Age (ca. 3.6 ka cal. BP), cold and wet Urnfield period (ca. 2.8 ka cal. BP), warm Roman period (ca. 2 ka cal. BP) and cold but humid Migration period (ca. 1.5 ka cal. BP). We observed extreme abruptness and amplitude of the variation in all geochemical proxies in the last 500 years, when biotic proxies imply a very intense human deforestation. Land-use changes may have altered both the temperature regime in the studied fen and the carbon cycle in the recharge area.

In Situ X-Ray Tomography Densification of Firn: Decoupling the Role of Mechanics and Diffusion Processes

One of the most efficient proxy method for paleoclimatology consists of obtaining data previously preserved within polar ice cores. Models for past climate reconstruction are based in particular on the characterization of entrapped gases in ice closed pores. Improving the temporal accuracy of these models requires a better understanding of firn densification mechanisms. In particular, the interplay between viscoplastic deformation and diffusion processes for pore closure is not well understood. In this work, we propose the first in situ densification experiments on polar firn retrieved from Antarctica with live characterization by X-ray tomography. Our in situ tests allow pore closure, which take thousands of years to occur in Antarctica, to be visualized and quantitatively characterized in a few hours in the laboratory. Pore separation and closure parameters with the accompanying microstructural changes were followed. We show that densification of polar firn and pore closure could be replicated at high strain rate and temperature. Experiments allow the viscoplastic part of the firn deformation to be decoupled from the diffusion mechanisms that occur at high temperature. Our results show that density alone is not sufficient to predict the close-off density at which gases get entrapped. More generally, the method laid out here may find useful application in the domain of high temperature powder compaction, for which pore closure and grain growth are significant process parameters.

The 600-mm precipitation isoline distinguishes tree-ring-width responses to climate in China.

The numerous temperature and precipitation reconstructions in China based on tree-ring-width data have played significant roles in furthering the understanding of past climate changes. However, the geographical variability in the responses of trees to climate variations in China remains largely undetermined. Here, we describe an important spatial boundary in the response of trees to climate variations, namely the 600-mm annual precipitation isoline. We found that, to the north of this line, tree-ring widths are usually positively correlated with precipitation and negatively correlated with growing-season temperature. To the south of this line, the tree-ring widths respond positively to temperature, and winter half-year temperatures are the main reconstructed parameters, especially on the third topographical step of China. We also found that precipitation reconstructions based on tree-ring data and the Palmer Drought Severity Index almost exclusively fall in the region of the 200- to 600-mm annual precipitation isolines, not other regions. Our findings indicate that, when using multiple tree-ring-width chronologies for large-scale past climate reconstructions, the climatic signal of each tree-ring-width series should be carefully considered.

Improving the quality of pollen-climate calibration-sets is the primary step for ensuring reliable climate reconstructions

Pollen-based climate reconstructions have been widely applied in China as an essential way to investigate quantitatively past climate change, which is necessary to improve the reliability of future climate predictions. However, their usefulness is often doubted, particularly for those regions with a long history of civilization (e.g. East China), where both the modern and past vegetation are heavily disturbed by human activities.Which factors influence the integrity of pollen-based climate reconstructions and how to improve their reliability are rigorous challenges for palynologists. Previous work focusing on these two questions has used modern pollen data from China or eastern continental Asia and mainly concludes that past climate reconstruction is quite sensitive to the quality of the calibration-set.

Influence of sampling and disturbance history on climatic sensitivity of temperature-limited conifers

Accurately capturing medium- to low-frequency trends in tree-ring data is vital to assessing climatic response and developing robust reconstructions of past climate. Non-climatic disturbance can affect growth trends in tree-ring-width (RW) series and bias climate information obtained from such records. It is important to develop suitable strategies to ensure the development of chronologies that minimize these medium- to low-frequency biases. By performing high density sampling (760 trees) over a ~40-ha natural high-elevation Norway spruce ( Picea abies) stand in the Romanian Carpathians, this study assessed the suitability of several sampling strategies for developing chronologies with an optimal climate signal for dendroclimatic purposes. There was a roughly equal probability for chronologies (40 samples each) to express a reasonable ( r = 0.3–0.5) to non-existent climate signal. While showing a strong high-frequency response, older/larger trees expressed the weakest overall temperature signal. Although random sampling yielded the most consistent climate signal in all sub-chronologies, the outcome was still sub-optimal. Alternative strategies to optimize the climate signal, including very high replication and principal components analysis, were also unable to minimize this disturbance bias and produce chronologies adequately representing climatic trends, indicating that larger scale disturbances can produce synchronous pervasive disturbance trends that affect a large part of a sampled population. The Curve Intervention Detection (CID) method, used to identify and reduce the influence of disturbance trends in the RW chronologies, considerably improved climate signal representation (from r = 0.28 before correction to r = 0.41 after correction for the full 760 sample chronology over 1909–2009) and represents a potentially important new approach for assessing disturbance impacts on RW chronologies. Blue intensity (BI) also shows promise as a climatically more sensitive variable which, unlike RW, does not appear significantly affected by disturbance. We recommend that studies utilizing RW chronologies to investigate medium- to long-term climatic trends also assess disturbance impact on those series.

Production and preservation of resins-past and present.

Amber is fossilised plant resin. It can be used to provide insights into the terrestrial conditions at the time the original resin was exuded. Amber research thus can inform many aspects of palaeontology, from the recovery and description of enclosed fossil organisms (biological inclusions) to attempts at reconstruction of past climates and environments. Here we focus on the resin itself, the conditions under which it may have been exuded, and its potential path to fossilisation, rather than on enclosed fossils. It is noteworthy that not all plants produce resin, and that not all resins can (nor do) become amber. Given the recent upsurge in the number of amber deposits described, it is time to re-examine ambers from a botanical perspective. Here we summarise the state of knowledge about resin production in modern ecosystems, and review the biological and ecological aspects of resin production in plants. We also present new observations on conifer-derived resin exudation, with a particular focus on araucarian conifer trees. We suggest that besides disease, insect attacks and traumatic wounding from fires and storms, other factors such as tree architecture and local soil conditions are significant in creating and preserving resin outpourings. We also examine the transformation of resin into amber (maturation), focusing on geological aspects of amber deposit formation and preservation. We present new evidence that expands previous understanding of amber deposit formation. Specific geological conditions such as anoxic burial are essential in the creation of amber from resin deposits. We show that in the past, the production of large amounts of resin could have been linked to global climate changes and environmental disruption. We then highlight where the gaps in our knowledge still remain and potential future research directions.

A 305-year continuous monthly rainfall series for the island of Ireland (1711–2016)

Abstract. A continuous 305-year (1711–2016) monthly rainfall series (IoI_1711) is created for the Island of Ireland. The post 1850 series draws on an existing quality assured rainfall network for Ireland, while pre-1850 values come from instrumental and documentary series compiled, but not published by the UK Met Office. The series is evaluated by comparison with independent long-term observations and reconstructions of precipitation, temperature and circulation indices from across the British–Irish Isles. Strong decadal consistency of IoI_1711 with other long-term observations is evident throughout the annual, boreal spring and autumn series. Annually, the most recent decade (2006–2015) is found to be the wettest in over 300 years. The winter series is probably too dry between the 1740s and 1780s, but strong consistency with other long-term observations strengthens confidence from 1790 onwards. The IoI_1711 series has remarkably wet winters during the 1730s, concurrent with a period of strong westerly airflow, glacial advance throughout Scandinavia and near unprecedented warmth in the Central England Temperature record – all consistent with a strongly positive phase of the North Atlantic Oscillation. Unusually wet summers occurred in the 1750s, consistent with proxy (tree-ring) reconstructions of summer precipitation in the region. Our analysis shows that inter-decadal variability of precipitation is much larger than previously thought, while relationships with key modes of climate variability are time-variant. The IoI_1711 series reveals statistically significant multi-centennial trends in winter (increasing) and summer (decreasing) seasonal precipitation. However, given uncertainties in the early winter record, the former finding should be regarded as tentative. The derived record, one of the longest continuous series in Europe, offers valuable insights for understanding multi-decadal and centennial rainfall variability in Ireland, and provides a firm basis for benchmarking other long-term records and reconstructions of past climate. Correlation of Irish rainfall with other parts of Europe increases the utility of the series for understanding historical climate in further regions.

Organic matter geochemical signatures (TOC, TN, C/N ratio, δ13C and δ15N) of surface sediment from lakes distributed along a climatological gradient on the western side of the southern Andes

Paleolimnological studies in western South America, where meteorological stations are scarce, are critical to obtain more realistic and reliable regional reconstructions of past climate and environmental changes, including vegetation and water budget variability. However, climate and environmental geochemical indicators must be tested before they can be applied with confidence. Here we present a survey of lacustrine surface sediment (core top, 0 to ~1cm) biogeochemical proxies (total organic carbon [TOC], total nitrogen [TN], carbon/nitrogen ratio [C/N ratio] and bulk organic δ13C and total δ15N) from a suite of 72 lakes spanning the transition from a Mediterranean climate with a patchwork of cultivated vegetation, pastureland, and conifers in central Chile to a rainy temperate climate dominated by broadleaf deciduous and evergreen forest further south. Sedimentary data are compared to the latitudinal and orographic climatic trends of the region based on the climatology (precipitation and temperature) produced with Climate Forecast System Reanalysis (CFSR) data and the modern Southern Hemisphere Westerly Winds (SWW) location. The geochemical data show inflection points at ~42°S latitude and ~1500m elevation that are likely related to the northern limit of influence of the SWW and elevation of the snow line, respectively. Overall the organic proxies were able to mimic climatic trends (Mean Annual Precipitation [MAP] and temperature [MAT]), indicating that they are a useful tool to be included in paleoclimatological reconstruction of the region.