The Threat of Multiâ Year Drought in Western Amazonia

Recent â onceâ inâ aâ centuryâ Amazonian droughts highlight the impacts of drought and climate change on this region’s vegetation, carbon storage, water cycling, biodiversity, land use, and economy. The latest climate model simulations suggest this region will experience worsening future drought. However, the instrumental record is too short to quantify the range of background drought variability, or to evaluate extended drought risk in climate models. To overcome these limitations, we generated a new, highly resolved lake record of hydroclimatic variability within the western Amazon Basin. We find that Amazonia has regularly experienced multiâ year droughts over the last millennium. Our results indicate that current climate model simulations likely underestimate the background risk of multiâ year Amazonian drought. These findings illustrate that the future sustainability of the Amazonian forest and its many services may require management strategies that consider the likelihood of multiâ year droughts superimposed on a continued warming trend.Plain Language SummaryThe Amazon basin recently experienced multiple â onceâ inâ aâ centuryâ droughts that impacted the region’s water cycle, economy, vegetation, and carbon storage. However, the instrumental record in this region tends to be too short to determine if these droughts are abnormal in a longâ term context. Paleoclimate data can extend drought records that help water and land managers plan for these events in the face of climate change. To provide additional information about preâ instrumental drought, here we present results from a new paleoclimate lake record based on sediments we recovered from Lake Limón in the Peruvian Amazon. We find that concentrations of elements in the Lake Limón sediment cores are likely recording past changes in rainfall variability. We use this elemental variability to generate a new, millennialâ length record of drought for the western Amazon. We show that this region has experienced multiâ year droughts at least twice a century over the last â ¼1,400 years. The frequency and severity of these paleoclimateâ inferred droughts may exceed most climate model and instrumentalâ era drought risk estimates. Our findings illustrate that the future sustainability of the Amazonian forest and its many ecosystem services may require management strategies that consider the likelihood of multiâ year droughts in addition to continued warming.Key PointsWe present results from a highâ resolution paleoclimate record of hydroclimatic variability in western AmazoniaOur paleoclimate record suggests western Amazonia has regularly experienced multiâ year drought over the last millenniumEarth system model simulations may underestimate the background risk of multiâ year western Amazonian droughtPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146272/1/wrcr23386_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146272/2/wrcr23386.pd

A stronger role for long-term moisture change than for CO₂ in determining tropical woody vegetation change

Anthropogenically elevated CO2 (eCO2) concentrations have been suggested to increase woody cover within tropical ecosystems through fertilization. The effect of eCO2 is built into Earth system models, although testing the relationship over long periods remains challenging. Here, we explore the relative importance of six drivers of vegetation change in western Africa over the past ~500,000 years (moisture availability, fire activity, mammalian herbivore density, temperature, temperature seasonality, CO2) by coupling past environmental change data from Lake Bosumtwi (Ghana) with global data. We found that moisture availability and fire activity were the most important factors in determining woody cover, whereas the effect of CO2 was small. Our findings suggest that the role of eCO2 effects on tropical vegetation in predictive models must be reconsidered

Scanning micro-X-ray fluorescence elemental mapping : a new tool for the study of laminated sediment records

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 9 (2008): Q02016, doi:10.1029/2007GC001800.The utility of elemental mapping by scanning X-ray fluorescence (XRF) in the study of annual laminated sedimentary records was investigated on eight annually laminated sediment types. The examples were chosen to illustrate the potential of this approach in environments dominated by terrigenous, biological and chemical deposition. Individual laminae were identifiable in elemental maps of all sediment types and were enhanced through the use of data reduction techniques (e.g., principal components transformation). Laminae were least apparent in clastic dominated systems with no seasonal changes in sediment sources. In biologically dominated systems, element maps provided insights into the composition of the varve subcomponents, related to alternating terrigenous and biologically dominated seasonal periods of deposition. Chemically precipitated structures were more prevalent than expected from visual investigations alone and may provide an underutilized paleoenvironmental signature of changing limnological conditions. Elemental mapping offers a valuable tool for the study of laminated records that complements existing techniques (e.g., SEM, digital image analysis).Funding was provided through NSF Earth System History grants and an NSF Instrumentation grant awarded to J.T.O

Potential climatic transitions with profound impact on Europe

We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding. <br/

Childhood deaths from external causes in Estonia, 2001–2005

<p>Abstract</p> <p>Background</p> <p>In 2000, the overall rate of injury deaths in children aged 0–14 was 28.7 per 100000 in Estonia, which is more than 5 times higher than the corresponding rate in neighbouring Finland. This paper describes childhood injury mortality in Estonia by cause and age groups, and validates registration of these deaths in the Statistical Office of Estonia against the autopsy data.</p> <p>Methods</p> <p>The data on causes of all child deaths in Estonia in 2001–2005 were abstracted from the autopsy protocols at the Estonian Bureau of Forensic Medicine. Average annual mortality rates per 100,000 were calculated. Coverage (proportion of the reported injury deaths from the total number of injury deaths) and accuracy (proportion of correctly classified injury deaths) of the registration of causes of death in Statistical Office of Estonia were assessed by comparing the Statistical Office of Estonia data with the data from Estonian Bureau of Forensic Medicine.</p> <p>Results</p> <p>Average annual mortality from external causes in 0–14 years-old children in Estonia was 19.1 per 100,000. Asphyxia and transport accidents were the major killers followed by poisoning and suicides. Relative contribution of these causes varied greatly between age groups. Intent of death was unknown for more than 10% of injury deaths. Coverage and accuracy of registration of injury deaths by Statistical Office of Estonia were 91.5% and 95.3%, respectively.</p> <p>Conclusion</p> <p>Childhood mortality from injuries in Estonia is among the highest in the EU. The number of injury deaths in Statistical Office of Estonia is slightly underestimated mostly due to misclassification for deaths from diseases. Accuracy of the Statistical Office of Estonia data was high with some underestimation of intentional deaths. Moreover, high proportion of death with unknown intent suggests underestimation of intentional deaths.</p> <p>Reduction of injury deaths should be given a high priority in Estonia. More information on circumstances around death is needed to enable establishing the intent of death.</p

A "critical" climatic evaluation of last interglacial (MIS 5e) records from the Norwegian Sea

Sediment cores from the Norwegian Sea were studied to evaluate interglacial climate conditions of the marine isotope stage 5e (MIS 5e). Using planktic forminiferal assemblages as the core method, a detailed picture of the evolution of surface water conditions was derived. According to our age model, a step-like deglaciation of the Saalian ice sheets is noted between ca. 135 and 124.5 Kya, but the deglaciation shows little response with regard to surface ocean warming. From then on, the rapidly increasing abundance of subpolar forminifers, concomitant with decreasing iceberg indicators, provides evidence for the development of interglacial conditions sensu stricto (5e-ss), a period that lasted for about 9 Ky. As interpreted from the foraminiferal records, and supported by the other proxies, this interval of 5e-ss was in two parts: showing an early warm phase, but with a fresher, i.e., lower salinity, water mass, and a subsequent cooling phase that lasted until ca. 118.5 Kya. After this time, the climatic optimum with the most intense advection of Atlantic surface water masses occurred until ca. 116 Kya. A rapid transition with two notable climatic perturbations is observed subsequently during the glacial inception. Overall, the peak warmth of the last interglacial period occurred relatively late after deglaciation, and at no time did it reach the high warmth level of the early Holocene. This finding must be considered when using the last interglacial situation as an analogue model for enhanced meridional transfer of ocean heat to the Arctic, with the prospect of a future warmer climate

Global and local sea level during the Last Interglacial: A probabilistic assessment

The Last Interglacial (LIG) stage, with polar temperatures likely 3-5 C warmer than today, serves as a partial analogue for low-end future warming scenarios. Based upon a small set of local sea level indicators, the Intergovernmental Panel on Climate Change (IPCC) inferred that LIG global sea level (GSL) was about 4-6 m higher than today. However, because local sea levels differ from GSL, accurately reconstructing past GSL requires an integrated analysis of globally distributed data sets. Here we compile an extensive database of sea level indicators and apply a novel statistical approach that couples Gaussian process regression of sea level to Markov Chain Monte Carlo modeling of geochronological errors. Our analysis strongly supports the hypothesis that LIG GSL was higher than today, probably peaking at 6-9 m. Our results highlight the sea level hazard associated with even relatively low levels of sustained global warming.Comment: Preprint version of what has since been published in Natur

Long-term land-cover/use change in a traditional farming landscape in Romania inferred from pollen data, historical maps and satellite images

Traditional farming landscapes in the temperate zone that have persisted for millennia can be exceptionally species-rich and are therefore key conservation targets. In contrast to Europe’s West, Eastern Europe harbours widespread traditional farming landscapes, but drastic socio-economic and political changes in the twentieth century are likely to have impacted these landscapes profoundly. We reconstructed long-term land-use/cover and biodiversity changes over the last 150 years in a traditional farming landscape of outstanding species diversity in Transylvania. We used the Regional Estimates of Vegetation Abundance from Large Sites model applied to a pollen record from the Transylvanian Plain and a suite of historical and satellite-based maps. We documented widespread changes in the extent and location of grassland and cropland, a loss of wood pastures as well as a gradual increase in forest extent. Land management in the socialist period (1947–1989) led to grassland expansion, but grassland diversity decreased due to intensive production. Land-use intensity has declined since the collapse of socialism in 1989, resulting in widespread cropland abandonment and conversion to grassland. However, these trends may be temporary due to both ongoing woody encroachment as well as grassland management intensification in productive areas. Remarkably, only 8% of all grasslands existed throughout the entire time period (1860–2010), highlighting the importance of land-use history when identifying target areas for conservation, given that old-growth grasslands are most valuable in terms of biodiversity. Combining datasets from different disciplines can yield important additional insights into dynamic landscape and biodiversity changes, informing conservation actions to maintain these species-rich landscapes in the longer term

Surface Energy Budgets of Arctic Tundra During Growing Season

This study analyzed summer observations of diurnal and seasonal surface energy budgets across several monitoring sites within the Arctic tundra underlain by permafrost. In these areas, latent and sensible heat fluxes have comparable magnitudes, and ground heat flux enters the subsurface during short summer intervals of the growing period, leading to seasonal thaw. The maximum entropy production (MEP) model was tested as an input and parameter parsimonious model of surface heat fluxes for the simulation of energy budgets of these permafrost‐underlain environments. Using net radiation, surface temperature, and a single parameter characterizing the thermal inertia of the heat exchanging surface, the MEP model estimates latent, sensible, and ground heat fluxes that agree closely with observations at five sites for which detailed flux data are available. The MEP potential evapotranspiration model reproduces estimates of the Penman‐Monteith potential evapotranspiration model that requires at least five input meteorological variables (net radiation, ground heat flux, air temperature, air humidity, and wind speed) and empirical parameters of surface resistance. The potential and challenges of MEP model application in sparsely monitored areas of the Arctic are discussed, highlighting the need for accurate measurements and constraints of ground heat flux.Plain Language SummaryGrowing season latent and sensible heat fluxes are nearly equal over the Arctic permafrost tundra regions. Persistent ground heat flux into the subsurface layer leads to seasonal thaw of the top permafrost layer. The maximum energy production model accurately estimates the latent, sensible, and ground heat flux of the surface energy budget of the Arctic permafrost regions.Key PointThe MEP model is parsimonious and well suited to modeling surface energy budget in data‐sparse permafrost environmentsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150560/1/jgrd55584.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150560/2/jgrd55584_am.pd