ALBERT

Description: Author(s): B. R. Marks, P. A. DeYoung, J. K. Smith, T. Baumann, J. Brown, N. Frank, J. Hinnefeld, M. Hoffman, M. D. Jones, Z. Kohley, A. N. Kuchera, B. Luther, A. Spyrou, S. Stephenson, C. Sullivan, M. Thoennessen, N. Viscariello, and S. J. Williams The neutron-unbound nucleus Be 13 was populated with a nucleon exchange reaction from a 71 MeV/u secondary B 13 beam. The decay-energy spectrum was reconstructed using invariant mass spectroscopy based on Be 12 fragments in coincidence with neutrons. The data could be described with an s -wave resonance… [Phys. Rev. C 92, 054320] Published Mon Nov 23, 2015

Description: ABSTRACT This study considers long-term precipitation and temperature variability across the Caribbean using two gridded data sets (CRU TS 3.21 and GPCCv5). We look at trends across four different regions (Northern, Eastern, Southern and Western), for three different seasons (May to July, August to October and November to April) and for three different periods (1901–2012, 1951–2012 and 1979–2012). There are no century-long trends in precipitation in either data set, although all regions (with the exception of the Northern Caribbean) show decade-long periods of wetter or drier conditions. The most significant of these is for the Southern Caribbean region which was wetter than the 1961–1990 average from 1940 to 1956 and then drier from 1957 to 1965. Temperature in contrast shows statistically significant warming everywhere for the periods 1901–2012, 1951–2012 and for over half the area during 1979–2012. Data availability is a limiting issue over much of the region and we also discuss the reliability of the series we use in the context of what is known to be available in the CRU TS 3.21 data set. More station data have been collected but have either not been fully digitized yet or not made freely available both within and beyond the region.

Description: Do not rely on the widely accepted rule that vicinal, sp 3 -positioned protons in cyclopentene moieties should always have more positive 3 J NMR coupling constants for the cis than for the trans arrangement: Unrecognized exceptions might misguide one to wrong stereochemical assignments and thence to erroneous mechanistic conclusions. We show here that two structurally innocent-looking 2,3-dibromo-1,1-dimethylindanes violate the rule by means of their values of 3 J (cis) = 6.1 Hz and 3 J (trans) = 8.4 Hz. The stereoselective formation of the trans diastereomer from 1,1-dimethylindene was improved with the tribromide anion (Br 3 − ) as the brominating agent in place of elemental bromine; the ensuing, regiospecific HBr elimination afforded 3-bromo-1,1-dimethylindene. The addition of elemental bromine to the latter compound, followed by thermal HBr elimination, furnished 2,3-dibromo-1,1-dimethylindene, whose Br/Li interchange reaction, precipitation, and subsequent protolysis yielded only 2-bromo-1,1-dimethylindene. Beilstein J. Org. Chem. 2016, 12, 1178–1184. doi:10.3762/bjoc.12.113

Description: This study assesses the skill of four statistical models in hindcasting North Atlantic annual tropical cyclone (TC) frequency over 1950–2008 with the aim of projecting future activity. Three of the models are motivated by operational statistical forecast schemes and are premised on standard hurricane predictors including sea surface temperatures (SSTs) and near-surface zonal winds. The fourth model uses an SST-gradient index previously proposed for Caribbean seasonal rainfall prediction. The statistical models, created from backward regression, explain 24-48% of the observed variability in 1950-2008 annual TC frequency. The future state of the predictors are extracted from the ECHAM5, HadCM3, MRI CGCM2.3.2a and MIROC3.2 GCM simulations under the Coupled Model Intercomparison Project Phase 3 (CMIP3). Models utilizing SST and near-surface wind predictors suggest significant increases in mean annual frequency by 2-8 TCs by 2070-2090, compared to a single surface wind predictor model, indicating that positive trends in SSTs under global warming have a larger relative influence on projections than changes in the variability of the surface winds. Wind-only models exhibit declines in TC frequency while the SST-gradient model yields little change relative to the present-day mean. Backward regression reapplied against the 1990-2008 period, analogous to future warmer oceanic and atmospheric state relative to the earlier years in the record, retains only the CLLJ-type predictors, explaining up to 82% of TC frequency variability and suggesting a more dominant role for the CLLJ in a warmer climate. Projections using the new models show either a more conservative increase or a stronger decrease in frequency, consistent with a stronger CLLJ.

Description: The Journal of Organic Chemistry DOI: 10.1021/acs.joc.8b01971

Description: ABSTRACT The Statistical Downscaling Model (SDSM) is used to investigate future projections of daily minimum and maximum temperature extremes for 45 stations and rainfall extremes for 39 stations across the Caribbean and neighbouring regions. Models show good skill in reproducing the monthly climatology of the mean daily temperatures and the frequencies of warm days, warm nights, cool days and cool nights between 1961 and 2001. Models for rainfall exhibit lower skill but generally capture the monthly climatology of mean daily rainfall and the spatial distribution of the mean annual maximum number of consecutive dry days (CDD) and mean annual count of days with daily rainfall above 10 mm (R10). Future projections suggest an increase (decrease) in warm (cool) days and nights by 2071–2099 under the A2 and B2 scenarios relative to 1961–1990. An increase in CDD is suggested for most stations except some eastern Caribbean stations and Bahamas. Decreases in RX1 (monthly maximum 1-day precipitation), R10 and R95p (annual total rainfall above the 95th percentile) are also suggested for some northern Caribbean locations and Belize under the A2 scenario, compared to a mixture of increases and decreases for the eastern Caribbean. Atmospheric predictors used in SDSM correlate well with known oceanic and atmospheric drivers of Caribbean climate, e.g. the Atlantic Multidecadal Oscillation (AMO) on a seasonal timescale. Atlantic sea surface temperatures and the Caribbean low level jet appear to have significant influence on Caribbean temperature and rainfall extremes. Initiatives have explored future Caribbean rainfall and temperature extremes. These relied on outputs from global and regional climate models and a weather generator. Here, the Statistical Downscaling Model (SDSM), a hybrid of regression and stochastic weather generator approaches is used. Results suggest more frequent warm events and variable responses in extreme rainfall by 2071–2099 under A2 and B2 scenarios. Atmospheric predictors in SDSM correlate well with known oceanic and atmospheric drivers of Caribbean climate, e.g. Atlantic Multidecadal Oscillation (AMO) on seasonal timescales.

Description: 〈span〉〈div〉Abstract〈/div〉Elevated topography is evident across the continental margins of the Atlantic. The Cumberland Peninsula, Baffin Island, formed as the result of rifting along the Labrador-Baffin margins in the late Mesozoic and is dominated by low relief high elevation topography. Apatite fission track (AFT) analysis of the landscape previously concluded that the area has experienced a differential protracted cooling regime since the Devonian; however, defined periods of cooling and the direct causes of exhumation were unresolved. This work combines the original AFT data with 98 apatite new (U-Th)/He ages from 16 samples and applies the newly developed ‘broken crystals’ technique to provide a greater number of thermal constraints for thermal history modelling to better constrain the topographic evolution. The spatial distribution of AFT and AHe ages implies exhumation has been significant toward the SE (Labrador) coastline, while results of thermal modelling outline three notable periods of cooling in the pre-rift (460 Ma – 200 Ma), from syn-rift to present (120 Ma – 0 Ma) and within post-rift (30 Ma – 0 Ma) stages. Pre-rift cooling is interpreted as the result of exhumation of Laurentia, syn-rift cooling as the result of rift flank uplift to the SE and differential erosion of landscape, while the final post-rift period is likely an artefact of the modelling process. These results suggest the source of the Cumberland Peninsula's modern-day elevated topography is uplift during rifting in the Cretaceous and the isostatic compensation following continuous Mesozoic and Cenozoic differential erosion. This work highlights the how interaction of rift tectonics and isostasy can be the principal source for modern elevated continental margins, while also providing insight into the pre-rift exhumational history of central Laurentia.〈strong〉Supplementary material:〈/strong〉〈a href="https://doi.org/10.6084/m9.figshare.c.4528409"〉https://doi.org/10.6084/m9.figshare.c.4528409〈/a〉〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Elevated topography is evident across the continental margins of the Atlantic. The Cumberland Peninsula, Baffin Island, formed as the result of rifting along the Labrador–Baffin margins in the late Mesozoic and is dominated by low-relief high-elevation topography. Apatite fission-track (AFT) analysis of the landscape previously concluded that the area has experienced a differential protracted cooling regime since the Devonian; however, defined periods of cooling and the direct causes of exhumation were unresolved. This work combines the original AFT data with 98 apatite new (U–Th)/He (AHe) ages from 16 samples and applies the newly developed ‘broken crystals’ technique to provide a greater number of thermal constraints for thermal history modelling to better constrain the topographic evolution. The spatial distribution of AFT and AHe ages implies that exhumation has been significant toward the SE (Labrador) coastline, and results of thermal modelling outline three notable periods of cooling: in the pre-rift stage (460–200 Ma), from synrift stage to present (120–0 Ma) and within the post-rift stage (30–0 Ma). Pre-rift cooling is interpreted as the result of exhumation of Laurentia and synrift cooling as the result of rift-flank uplift to the SE and differential erosion of landscape, whereas the final post-rift period is probably an artefact of the modelling process. These results suggest that the source of the Cumberland Peninsula's modern-day elevated topography is uplift during rifting in the Cretaceous and the isostatic compensation following continuous Mesozoic and Cenozoic differential erosion. This work highlights how interaction of rift tectonics and isostasy can be the principal source for modern elevated continental margins, and also provides insight into the pre-rift exhumational history of central Laurentia.〈strong〉Supplementary material:〈/strong〉 Thermal histories are available at: 〈a href="https://doi.org/10.6084/m9.figshare.c.4528409"〉https://doi.org/10.6084/m9.figshare.c.4528409〈/a〉〈/span〉

Description: The Columbia Climate Center, in partnership with World Wildlife Fund, Woods Hole Research Center, and Arctic 21, held a workshop titled A 5 C Arctic in a 2 C World on July 20 and 21, 2016. The workshop was co-sponsored by the International Arctic Research Center (University of Alaska Fairbanks), the Arctic Institute of North America (Canada), the MEOPAR Network (Marine Environmental Observation, Prediction, and Response), and the Future Ocean Excellence Cluster. The goal of the workshop was to advance thinking on the science and policy implications of the temperature change in the context of the 1.5 to 2 C warming expected for the globe, as dis- cussed during the 21st session of the Conference of the Parties of the United Nations Framework Convention on Climate Change at Paris in 2015. For the Arctic, such an increase means an antic- ipated increase of roughly 3.5 to 5 C. An international group of 41 experts shared perspectives on the regional and global impacts of an up to +5 C Arctic, examined the feasibility of actively lowering Arctic temperatures, and considered realistic timescales associated with such interventions. The group also discussed the science and the political and governance actions required for alternative Arctic futures.