ALBERT

Description: Contemporary climate dynamics of the circum-Caribbean region are characterised by significant precipitation variability on interannual and interdecadal timescales controlled primarily by El Niño Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO). However, our understanding of pre-industrial climate variability in the region is hampered by the sparse geographic distribution of palaeoclimate archives. Here, we present a high-resolution reconstruction of effective precipitation for Barbuda since the mid-16th century, based on biostratigraphic and stable isotope analyses of fossil ostracods and gastropods recovered from lake sediment cores from Freshwater Pond, the only freshwater lake on the island. We interpret episodic fluctuations in shell accumulation in the sediment record to represent changes in the balance between precipitation and evaporation during the ‘Little Ice Age’ (LIA; ~1400–1850 CE) and Industrial (1850–present) periods. Comparisons between indices of reconstructed ENSO and AMO variability, the abundance of the freshwater gastropod Pyrgophorus parvulus and the 18 O records from ostracod calcite suggest that the relative influence of ENSO and AMO on long-term rainfall patterns in Barbuda has changed over the last 400 years. Our findings are in agreement with other high-resolution palaeoclimate studies that suggest that long-term changes in effective precipitation during the LIA were much more variable, temporally and spatially, than previously suggested.

Description: Terrestrial vegetation currently absorbs approximately a third of anthropogenic CO2 emissions, mitigating the rise of atmospheric CO2. However, terrestrial net primary production is highly sensitive to atmospheric CO2 levels and associated climatic changes. In C3 plants, which dominate terrestrial vegetation, net photosynthesis depends on the ratio between photorespiration and gross...

Description: The Lower Cretaceous Goldeneye gas field lies in the Captain turbidite fairway of the Moray Firth and has recently ceased production. Its situation and dimensions have made it an excellent candidate for CO 2 sequestration. The field was extensively modelled for the original development planning when uncertainty was assessed from the perspective of volumetrics and field behaviour. The subsequent need to assess its suitability as a CO 2 store has given the opportunity for a look back at an uncertainty analysis with the benefit of full-field performance, and to perform a new analysis aimed at different issues concerning behaviour during CO 2 injection. Both sets of analyses required coupled static–dynamic modelling runs in which the key static parameter ranges of the field were varied, including depth conversion, internal geometries and aquifer properties. For the field development work the parameter ranges were explored to assess in-place volumes and field behaviour under natural aquifer and depletion drive; for the CO 2 uncertainty work, however, parameter ranges were explored to demonstrate storage capacity and CO 2 containment. The look-back showed that the field volumes indicated by production data landed in the upper part of the original uncertainty range and that there was definitive spare capacity in the field relative to the planned injection volume.

Description: This study presents a new interpretation of the evidence for Holocene lake-level changes from Hawes Water in NW England constrained by detailed stratigraphic data, radiocarbon chronology and palaeo-environmental evidence. Lake levels are seen to decline gradually from the start of the Holocene through to 9960 cal. yr BP, in response to lake infilling and the prevailing dry climatic conditions. Low lake levels then persist until 6000 cal. yr BP, punctuated by two transgressive phases. Rising sea levels during the Holocene high-level sea stand are thought to be responsible for a major rise in lake level at 6000 cal. yr BP driven by changes in the local water-table. The rise in lake level is coincident with a rise in anthropogenic activity across the site, possibly reflecting the migration of coastal Mesolithic communities inland in response to rising sea levels.

Description: Investigation of core and outcrop samples of the Cenomanian Natih-B Member (North Oman) indicates that the different lithofacies present experienced rather different early diagenesis shortly after deposition. Transmitted-light, cathodoluminescence and backscattered scanning-electron microscopy, as well as stable-isotopic, X-ray diffraction and total organic carbon (TOC) analyses were employed to delineate the major controls on the cyclic pattern of early diagenesis and hydrocarbon source potential.The Natih-B intrashelf basinal carbonates are composed of pelagic sediments that exhibit high-frequency cyclicity marked by decimetre-thick lithofacies alternations, mainly between: Lithofacies A compacted, partially bioturbated, skeletal, organic carbon-rich mudstone to wackestone; and Lithofacies B uncompacted, extensively bioturbated, skeletal, sparry-calcite rich wackestone to packstone. Individual units are composed variously of authigenic and biogenic calcite (58.1–97.6%, average 78.5%) and organic carbon (0.3–13.7% TOC, average 3.6%), together with minor quartz, clay, pyrite, dolomite and phosphatic material (fish debris). Lithofacies A contains relatively more organic carbon, clay, pyrite and dolomite than Lithofacies B and constitutes an excellent source rock. Diagenetic textures of Lithofacies A are dominated by compactional deformation of burrow fabrics, faecal pellets and solution seams, in addition to zoned/bright luminescent, non-ferroan sparry and isopachous calcite cement in and around uncompacted foraminifer tests, in an uncemented matrix. In contrast, Lithofacies B does not show any signs of compaction other than microstylolites and is dominated by zoned/dull luminescent, non-ferroan calcite microspar replacement, in addition to pore-filling, predominantly dull-luminescent, non-ferroan, sparry calcite cement. Moreover, Lithofacies B shows evidence of isopachous and meniscus-style cementation, together with geopetal structures and mictritic peloids. Stable-isotopic compositions of both lithofacies were determined from whole-rock samples (δ13C = −0.9 to +0.9‰, average +0.3‰; δ18O = −5.6 to −3.7‰, average −4.8‰) and sparry calcite (both cement and matrix) subsamples (δ13C = −0.6 to +1.2‰, average +0.6‰; δ18O = −5.7 to −3.7‰, average −4.3‰); all results being relative to Vienna Pee Dee Belemnite.These petrographic and isotopic characteristics suggest that the Natih-B abundant calcite cements and replacements were precipitated early, prior to compaction, mainly from ‘normal’ (open, oxic) seawater at slightly elevated depositional temperatures. Some of the slightly negative δ13C values, however, indicate an addition of isotopically light carbon, probably derived from organic-matter oxidation by organisms living in marine pore waters. Based on evidence of extensive seafloor bioturbation and cementation, and their position within the depositional succession, the tops of Lithofacies B (wackestones to packstones) are interpreted as ‘discontinuity surfaces’ that cap shallowing-upward, fifth-order cycles, formed as a function of sediment starvation and increased bottom-current activity during relative sea-level stillstand/turnaround. In contrast, Lithofacies A (mudstones to wackestones) is believed to reflect high organic production coupled with high sedimentation rate and rapid burial. These conditions limited total infaunal colonization and extensive calcite precipitation, and preserved organic matter together with some escape burrows and in-place fauna, suggesting episodic sediment influx when more accommodation was available and seafloor diagenesis was minimized during relative sea-level rises. The relatively higher amounts of pyrite and dolomite in Lithofacies A likely indicate organic-matter degradation by bacterial sulphate reduction in anoxic pore waters during shallow burial.

Description: Commonly considered strategies for reducing the environmental impact of light-duty transportation include using alternative fuels and improving vehicle fuel economy. We evaluate the air quality-related human health impacts of 10 such options, including the use of liquid biofuels, diesel, and compressed natural gas (CNG) in internal combustion engines; the use...

Description: The Lower Cretaceous Goldeneye gas field lies in the Captain turbidite fairway of the Moray Firth and has recently ceased production. Its situation and dimensions have made it an excellent candidate for CO 2 sequestration. The field was extensively modelled for the original development planning when uncertainty was assessed from the perspective of volumetrics and field behaviour. The subsequent need to assess its suitability as a CO 2 store has given the opportunity for a look back at an uncertainty analysis with the benefit of full-field performance, and to perform a new analysis aimed at different issues concerning behaviour during CO 2 injection. Both sets of analyses required coupled static–dynamic modelling runs in which the key static parameter ranges of the field were varied, including depth conversion, internal geometries and aquifer properties. For the field development work the parameter ranges were explored to assess in-place volumes and field behaviour under natural aquifer and depletion drive; for the CO 2 uncertainty work, however, parameter ranges were explored to demonstrate storage capacity and CO 2 containment. The look-back showed that the field volumes indicated by production data landed in the upper part of the original uncertainty range and that there was definitive spare capacity in the field relative to the planned injection volume.

Description: The effects of the past century's increase in atmospheric CO 2 concentration ([CO 2 ]) have been recorded in the stable carbon isotope composition ( 13 C) of the annual growth rings of trees. The isotope record frequently shows increases in photosynthetic CO 2 uptake relative to stomatal conductance, which estimates the CO 2 concentration gradient across the stomata ( c a – c i ). This variable, which is one control over the net photosynthetic rate, has been suggested as a homeostatic gas-exchange set point that is easy to estimate from 13 C and [CO 2 ]. However, in high-latitude conifer forests, the literature is mixed; some studies show increases in ( c a – c i ) and others show homeostasis. Here we present leaf and tree-ring 13 C data from a controlled experiment that tested factorial combinations of elevated [CO 2 ] (365 and 700 mol mol –1 ) and fertilization on mature Norway spruce ( Picea abies (L.) Karst.) trees in northern Sweden. We found first that the leaf carbon pool was contaminated by the current photosynthate in the older leaf cohorts. This is the reverse of the common observation that older photosynthate reserves can be used to produce new tissue; here the older tissue contains recent photosynthate. We found that the tree-ring data lack such contamination and in any case they better integrate over the canopy and the growing season than do leaves. In the second and third years of treatment, elevated [CO 2 ] alone increased ( c a – c i ) by 38%; when combined with fertilization, it increased ( c a – c i ) by 60%. The results of this study support the idea that annual rings provide a clearer isotopic signal than do foliage age-classes. The tree-ring data show that inferred ( c a – c i ) depends not only on [CO 2 ], but also on mineral-nutrient status. The differences in ( c a – c i ) are sufficiently large to account for the treatment-induced increase in wood-volume production in these stands.

Description: Oron (1) argues that our study (2) uses “inappropriate” methods and is framed in a way that leads “readers toward misguided conclusions.” Both of these arguments are misplaced and seem more focused on some media coverage of our article than on our article itself. Oron’s (1) specific critiques do not...

Description: Despite growing recognition of the negative externalities associated with reactive nitrogen (N), the damage costs of N to air, water, and climate remain largely unquantified. We propose a comprehensive approach for estimating the social cost of nitrogen (SCN), defined as the present value of the monetary damages caused by an incremental increase in N. This framework advances N accounting by considering how each form of N causes damages at specific locations as it cascades through the environment. We apply the approach to an empirical example that estimates the SCN for N applied as fertilizer. We track impacts of N through its transformation into atmospheric and aquatic pools and estimate the distribution of associated costs to affected populations. Our results confirm that there is no uniform SCN. Instead, changes in N management will result in different N-related costs depending on where N moves and the location, vulnerability, and preferences of populations affected by N. For example, we found that the SCN per kilogram of N fertilizer applied in Minnesota ranges over several orders of magnitude, from less than $0.001/kg N to greater than $10/kg N, illustrating the importance of considering the site, the form of N, and end points of interest rather than assuming a uniform cost for damages. Our approach for estimating the SCN demonstrates the potential of integrated biophysical and economic models to illuminate the costs and benefits of N and inform more strategic and efficient N management.