Search

Glacier mass balance reconstructions provide a means of placing relatively short observational records into a longer-term context. Here, we use multiple proxies from Pinus cembra trees from God da Tamangur, combining tree ring anatomy and stable isotope chronologies to reconstruct seasonal glacier mass balance (i.e., winter, summer, and annual mass balance) for the nearby Silvretta Glacier over the last 2 centuries. The combination of tree ring width, radial diameter of earlywood cell lumina, and latewood radial cell wall thickness provides a highly significant reconstruction for summer mass balance, whereas for the winter mass balance, the correlation was less significant but still robust when radial cell lumina were combined with δ18O records. A combination of the reconstructed winter and summer mass balances allows the quantification of the annual mass balance of the Silvretta Glacier for which in situ measurements date back to 1919. Our reconstruction indicates a substantial increase in glacier mass during the first half of the 19th century and an abrupt termination of this phase after the end of the Little Ice Age. Since the 1860s, negative glacier mass balances have been dominant and mass losses accelerate as anthropogenic warming picks up in the Alps.

Abstract Tropical South American climate is influenced by the South American Summer Monsoon and the El Niño Southern Oscillation. However, assessing natural hydroclimate variability in the region is hindered by the scarcity of long-term instrumental records. Here we present a tree-ring δ 18O-based precipitation reconstruction for the South American Altiplano for 1700–2013 C.E., derived from Polylepis tarapacana tree rings. This record explains 56% of December–March instrumental precipitation variability in the Altiplano. The tree-ring δ 18O chronology shows interannual (2–5 years) and decadal (~11 years) oscillations that are remarkably consistent with periodicities observed in Altiplano precipitation, central tropical Pacific sea surface temperatures, southern-tropical Andean ice core δ 18O and tropical Pacific coral δ 18O archives. These results demonstrate the value of annual-resolution tree-ring δ 18O records to capture hydroclimate teleconnections and generate robust tropical climate reconstructions. This work contributes to a better understanding of global oxygen-isotope patterns, as well as atmospheric and oceanic processes across the tropics.

Abstract Documentary climate data describe evidence of past climate arising from predominantly written historical documents such as diaries, chronicles, newspapers, or logbooks. Over the past decades, historians and climatologists have generated numerous document-based time series of local and regional climates. However, a global dataset of documentary climate time series has never been compiled, and documentary data are rarely used in large-scale climate reconstructions. Here, we present the first global multi-variable collection of documentary climate records. The dataset DOCU-CLIM comprises 621 time series (both published and hitherto unpublished) providing information on historical variations in temperature, precipitation, and wind regime. The series are evaluated by formulating proxy forward models (i.e., predicting the documentary observations from climate fields) in an overlapping period. Results show strong correlations, particularly for the temperature-sensitive series. Correlations are somewhat lower for precipitation-sensitive series. Overall, we ascribe considerable potential to documentary records as climate data, especially in regions and seasons not well represented by early instrumental data and palaeoclimate proxies.

Abstract Background The prognostic role of decongestion‐related change of cardiac morphology and in particular right heart function has not been investigated comprehensively in AHF patients. Methods and results This prospective observational single‐centre study included consecutive patients hospitalized for treatment of AHF with reduced, mildly‐reduced or preserved left ventricular ejection fraction (LVEF). Comprehensive transthoracic echocardiography at admission and discharge assessed decongestion‐related change of cardiac function and morphology. The combined endpoint of 1 year all‐cause mortality and cardiovascular rehospitalization explored the prognostic importance of decongestion‐related change. The 176 study participants were 83 years old [74–87] and 54% were men. Fifty one (29%) had rLVEF, 65 (37%) mrLVEF, and 60 (34%) pLVEF. The proportion of de novo or worsening chronic HF was not different between LVEF groups. HF aetiology and cardiovascular risk factors were equally distributed across all groups except for a higher BMI in the pLVEF group. Decongestion equally reduced body weight, heart rate, systolic and diastolic blood pressure, tricuspid regurgitation gradient, and inferior vena cava diameter across all groups (P

Annually resolved tree-ring records extending back to pre-industrial conditions have the potential to constrain the responses of global land surface models at interannual to centennial timescales. Here, we demonstrate a framework to simultaneously constrain the representation of tree growth and physiology in the ORCHIDEE global land surface model using the simulated variability of tree-ring width and carbon (Δ13C) and oxygen (δ18O) stable isotopes in six sites in boreal and temperate Europe. We exploit the resulting tree-ring triplet to derive integrative constraints for leaf physiology and growth from well-known mechanistic relationships among the variables. ORCHIDEE simulates Δ13C (r=0.31–0.80) and δ18O (r=0.36–0.74) better than tree-ring width (r), with an overall skill similar to that of a tree-ring model (MAIDENiso) and another isotope-enabled global vegetation model (LPX-Bern). The comparison with tree-ring data showed that growth variability is not well represented in ORCHIDEE and that the parameterization of leaf-level physiological responses (stomatal control) to drought stress in the temperate region can be constrained using the interannual variability of tree-ring stable isotopes. The representation of carbon storage and remobilization dynamics emerged as a critical process to improve the realism of simulated growth variability, temporal carryover, and recovery of forest ecosystems after climate extremes. Simulated forest gross primary productivity (GPP) correlates with simulated tree-ring Δ13C and δ18O variability, but the origin of the correlations with tree-ring δ18O is not entirely physiological. The integration of tree-ring data and land surface models as demonstrated here should guide model improvements and contribute towards reducing current uncertainties in forest carbon and water cycling.

Copyright of International Journal of Nautical Archaeology is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Glacier mass balance reconstructions provide a means of placing relatively short observational records into a longer-term context. Here, we use multiple proxies from Pinus cembra trees from God da Tamangur, combining tree ring anatomy and stable isotope chronologies to reconstruct seasonal glacier mass balance (i.e., winter, summer, and annual mass balance) for the nearby Silvretta Glacier over the last 2 centuries. The combination of tree ring width, radial diameter of earlywood cell lumina, and latewood radial cell wall thickness provides a highly significant reconstruction for summer mass balance, whereas for the winter mass balance, the correlation was less significant but still robust when radial cell lumina were combined with δ18O records. A combination of the reconstructed winter and summer mass balances allows the quantification of the annual mass balance of the Silvretta Glacier for which in situ measurements date back to 1919. Our reconstruction indicates a substantial increase in glacier mass during the first half of the 19th century and an abrupt termination of this phase after the end of the Little Ice Age. Since the 1860s, negative glacier mass balances have been dominant and mass losses accelerate as anthropogenic warming picks up in the Alps. [ABSTRACT FROM AUTHOR]

Abstract Aims Mild or moderate aortic regurgitation (AR) has only little effect on cardiovascular outcome in people with normal left ventricular ejection fraction (EF); therefore, it is not perceived as a major clinical problem. This study investigates whether mild or moderate AR is associated with increased short‐term mortality in patients hospitalized for treatment of acute heart failure (AHF) and whether mild or moderate AR impacts differently on short‐term mortality in AHF patients with reduced EF (AHFrEF), mid‐range EF (AHFmrEF), or preserved EF (AHFpEF). Methods and results This mono‐centric study included 505 consecutive adult patients hospitalized for de novo or worsening chronic HF not related to acute ischaemia or severe valvular pathology in the echocardiogram at index hospitalization. Cox regression analysis studied the impact of AR on all‐cause mortality (ACM) over the 150 days' study period. Mild or moderate AR was associated with increased ACM (HR 1.75 [95% CI: 1.1–2.7]; P = 0.009). The prevalence of mild or moderate AR in the study population was 42% and not significantly different between AHFpEF (n = 227), AHFmrEF (n = 86), and AHFrEF (n = 192) study participants (37.9% vs. 50.0% vs. 42.7%; P = 0.144). In AHFpEF patients, the age‐adjusted hazard for ACM was increased in patients with AR compared with patients without AR (HR 2.17 [95% CI: 1.1–4.2]; P = 0.002). The age‐adjusted hazard for ACM was increased by a trend in AHFmrEF with AR (HR 7.11, [95% CI: 0.9–57.8]; P = 0.067) and not different between the AHFrEF groups (HR 0.95 [95% CI: 0.5–1.8]; P = 0.875). Conclusions Mild or moderate AR increased ACM only in AHFpEF patients, highlighting a distinct clinical relevance.

Climatic reconstructions based on tree-ring isotopic series convey substantial information about past conditions prevailing in forested regions of the globe. However, in some cases, the relations between isotopic and climatic records appear unstable over time, generating the “isotopic divergences”. Former reviews have thoroughly discussed the divergence concept for tree-ring physical properties but not for isotopes. Here we want to take stock of the isotopic divergence problem, express concerns and stimulate collaborative work for improving paleoclimatic reconstructions. There are five main causes for divergent parts in isotopic and climatic series: (1) artefacts due to sampling and data treatment, relevant for dealing with long series using sub-fossil stems; (2) stand dynamics, including juvenile effects mostly occurring in the early part of tree-ring series; (3) rise in atmospheric pCO2, which can directly influence the foliar behaviour; (4) change in climate, which may modify the isotope–climate causal links; and finally (5) atmospheric pollution, which may alter leaf and root functions. Future paleoclimate research would benefit from interdisciplinary efforts designed to develop further process-based models integrating multi-proxy inputs so as to help identify causes of isotopic divergences and circumvent some of them in inverse applications.

Along the coast of northwestern Alaska, architectural wood remains are well preserved in the Birnirk and Thule coastal sites of the early 2nd millennium CE. These structural wood elements are unique archives for documenting climatic variations and cultural transformations during this key development period of Inuit culture. Along this treeless Arctic coast, driftwood accumulates from the subarctic forests of interior Alaska. Except for northwestern Alaska, regional tree-ring chronologies are too short (at best 350–400 years) to successfully date archaeological wood remains from Birnirk and Thule coastal sites using conventional dendrochronology. This paper examines the potential of tree-ring derived δ 18O signal to annually date eight architectural wood samples from the Rising Whale (KTZ-304) site at Cape Espenberg, northwestern Alaska. We developed a δ 18O master chronology, covering the period 935–1157 CE, using five wood samples from the KTZ-304 site. Blind isotope cross-dating of individual series belonging to this δ 18O master chronology (one against the other four) showed conclusive dating and a very strong coherence of the isotopic signal. We, then, used the δ 18O master chronology to cross-date three other wood samples for which we knew, from previous 14C wiggle-matching procedure, the first measured ring to be in this time interval, within a ± 18 to 30-year precision. Oxygen isotope dendrochronology provided a plausible date for one of the samples (the first measured ring at 1073 CE). This preliminary study encourages us to acquire additional data to extend in time and strengthen the δ 18O master chronology of northwestern Alaska (NWAK18O) and help refine our understanding of climate and culture change during the 2nd millennium CE. [ABSTRACT FROM AUTHOR]

Oxygen isotopes in tree rings (δ18OTR) are widely used to reconstruct past climates. However, the complexity of climatic and biological processes controlling isotopic fractionation is not yet fully understood. Here, we use the MAIDENiso model to decipher the variability in δ18OTR of two temperature-sensitive species of relevant palaeoclimatological interest (Picea mariana and Nothofagus pumilio) and growing at cold high latitudes in North and South America. In this first modelling study on δ18OTR values in both northeastern Canada (53.86° N) and western Argentina (41.10° S), we specifically aim at (1) evaluating the predictive skill of MAIDENiso to simulate δ18OTR values, (2) identifying the physical processes controlling δ18OTR by mechanistic modelling and (3) defining the origin of the temperature signal recorded in the two species. Although the linear regression models used here to predict daily δ18O of precipitation (δ18OP) may need to be improved in the future, the resulting daily δ18OP values adequately reproduce observed (from weather stations) and simulated (by global circulation model) δ18OP series. The δ18OTR values of the two species are correctly simulated using the δ18OP estimation as MAIDENiso input, although some offset in mean δ18OTR levels is observed for the South American site. For both species, the variability in δ18OTR series is primarily linked to the effect of temperature on isotopic enrichment of the leaf water. We show that MAIDENiso is a powerful tool for investigating isotopic fractionation processes but that the lack of a denser isotope-enabled monitoring network recording oxygen fractionation in the soil–vegetation–atmosphere compartments limits our capacity to decipher the processes at play. This study proves that the eco-physiological modelling of δ18OTR values is necessary to interpret the recorded climate signal more reliably.