Untangling biogeochemical processes from the impact of ocean circulation: First insight on the Mediterranean dissolved barium dynamics

Based on an unprecedented dissolved barium (D_Ba) data set collected in the Mediterranean Sea during a zonal transect between the Lebanon coast and Gibraltar (M84/3 cruise, April 2011), we decompose the D_Ba distribution to isolate the contribution of biogeochemical processes from the impact of the oceanic circulation. We have built a simple parametric water mass analysis (Parametric Optimum Multiparameter analysis) to reconstruct the contribution of the different Mediterranean water masses to the thermohaline structure. These water mass fractions have then been used to successfully reconstruct the background vertical gradient of D_Ba reflecting the balance between the large-scale oceanic circulation and the biological activity over long time scales. Superimposed on the background field, several D_Ba anomalies have been identified. Positive anomalies are associated with topographic obstacles and may be explained by the dissolution of particulate biogenic barium (P_Ba barite) of material resuspended by the local currents. The derived dissolution rates range from 0.06 to 0.21 μmol m−2 d−1. Negative anomalies are present in the mesopelagic region of the western and eastern basins (except in the easternmost Levantine basin) as well as in the abyssal western basin. This represents the first quantification of the nonconservative component of the D_Ba signal. These mesopelagic anomalies could reflect the subtraction of D_Ba during P_Ba barite formation occurring during organic carbon remineralization. The deep anomalies may potentially reflect the transport of material toward the deep sea during winter deep convection and the subsequent remineralization. The D_Ba subtraction fluxes range from −0.07 to −1.28 μmol m−2 d−1. D_Ba-derived fluxes of P_Ba barite (up to 0.21 μmol m−2 d−1) and organic carbon (13 to 29 mmol C m−2 d−1) are in good agreement with other independent measurements suggesting that D_Ba can help constrain remineralization horizons. This study highlights the importance of quantifying the impact of the large-scale oceanic circulation in order to better understand the biogeochemical cycling of elements and to build reliable geochemical proxies

Stabilization of dense Antarctic water supply to the Atlantic Ocean overturning circulation

The lower limb of the Atlantic overturning circulation is resupplied by the sinking of dense Antarctic Bottom Water (AABW) that forms via intense air–sea–ice interactions next to Antarctica, especially in the Weddell Sea. In the last three decades, AABW has warmed, freshened and declined in volume across the Atlantic Ocean and elsewhere, suggesting an ongoing major reorganization of oceanic overturning. However, the future contributions of AABW to the Atlantic overturning circulation are unclear. Here, using observations of AABW in the Scotia Sea, the most direct pathway from the Weddell Sea to the Atlantic Ocean, we show a recent cessation in the decline of the AABW supply to the Atlantic overturning circulation. The strongest decline was observed in the volume of the densest layers in the AABW throughflow from the early 1990s to 2014; since then, it has stabilized and partially recovered. We link these changes to variability in the densest classes of abyssal waters upstream. Our findings indicate that the previously observed decline in the supply of dense water to the Atlantic Ocean abyss may be stabilizing or reversing and thus call for a reassessment of Antarctic influences on overturning circulation, sea level, planetary-scale heat distribution and global climate

Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs I : Characterizing Benchmarks, Gl570D and HD3651B

Michael Line, et al, 'UNIFORM ATMOSPHERIC RETRIEVAL ANALYSIS OF ULTRACOOL DWARFS. I. CHARACTERIZING BENCHMARKS, Gl 570D AND HD 3651B', The Astrophysical Journal, Vol. 802 (2), July 2015, doi: https://doi.org/10.1088/0004-637X/807/2/183, published by IOP.Interpreting the spectra of brown dwarfs is key to determining the fundamental physical and chemical processes occurring in their atmospheres. Powerful Bayesian atmospheric retrieval tools have recently been applied to both exoplanet and brown dwarf spectra to tease out the thermal structures and molecular abundances to understand those processes. In this manuscript we develop a significantly upgraded retrieval method and apply it to the SpeX spectral library data of two benchmark late T-dwarfs, Gl570D and HD3651B, to establish the validity of our upgraded forward model parameterization and Bayesian estimator. Our retrieved metallicities, gravities, and effective temperature are consistent with the metallicity and presumed ages of the systems. We add the carbon-to-oxygen ratio as a new dimension to benchmark systems and find good agreement between carbon-to-oxygens ratio derived in the brown dwarfs and the host stars. Furthermore, we have for the first time unambiguously determined the presence of ammonia in the low-resolution spectra of these two late T-dwarfs. We also show that the retrieved results are not significantly impacted by the possible presence of clouds, though some quantities are significantly impacted by uncertainties in photometry. This investigation represents a watershed study in establishing the utility of atmospheric retrieval approaches on brown dwarf spectra.Peer reviewedFinal Published versio

Basic science232. Certolizumab pegol prevents pro-inflammatory alterations in endothelial cell function

Background: Cardiovascular disease is a major comorbidity of rheumatoid arthritis (RA) and a leading cause of death. Chronic systemic inflammation involving tumour necrosis factor alpha (TNF) could contribute to endothelial activation and atherogenesis. A number of anti-TNF therapies are in current use for the treatment of RA, including certolizumab pegol (CZP), (Cimzia ®; UCB, Belgium). Anti-TNF therapy has been associated with reduced clinical cardiovascular disease risk and ameliorated vascular function in RA patients. However, the specific effects of TNF inhibitors on endothelial cell function are largely unknown. Our aim was to investigate the mechanisms underpinning CZP effects on TNF-activated human endothelial cells. Methods: Human aortic endothelial cells (HAoECs) were cultured in vitro and exposed to a) TNF alone, b) TNF plus CZP, or c) neither agent. Microarray analysis was used to examine the transcriptional profile of cells treated for 6 hrs and quantitative polymerase chain reaction (qPCR) analysed gene expression at 1, 3, 6 and 24 hrs. NF-κB localization and IκB degradation were investigated using immunocytochemistry, high content analysis and western blotting. Flow cytometry was conducted to detect microparticle release from HAoECs. Results: Transcriptional profiling revealed that while TNF alone had strong effects on endothelial gene expression, TNF and CZP in combination produced a global gene expression pattern similar to untreated control. The two most highly up-regulated genes in response to TNF treatment were adhesion molecules E-selectin and VCAM-1 (q 0.2 compared to control; p > 0.05 compared to TNF alone). The NF-κB pathway was confirmed as a downstream target of TNF-induced HAoEC activation, via nuclear translocation of NF-κB and degradation of IκB, effects which were abolished by treatment with CZP. In addition, flow cytometry detected an increased production of endothelial microparticles in TNF-activated HAoECs, which was prevented by treatment with CZP. Conclusions: We have found at a cellular level that a clinically available TNF inhibitor, CZP reduces the expression of adhesion molecule expression, and prevents TNF-induced activation of the NF-κB pathway. Furthermore, CZP prevents the production of microparticles by activated endothelial cells. This could be central to the prevention of inflammatory environments underlying these conditions and measurement of microparticles has potential as a novel prognostic marker for future cardiovascular events in this patient group. Disclosure statement: Y.A. received a research grant from UCB. I.B. received a research grant from UCB. S.H. received a research grant from UCB. All other authors have declared no conflicts of interes

Synchronous intensification and warming of Antarctic Bottom Water outflow from the Weddell Gyre

Antarctic Bottom Water (AABW), the densest water in the global overturning circulation, has warmed in recent decades, most notably in the Atlantic. Time series recorded within the boundary currents immediately upstream and downstream of the most significant outflow of AABW from the Weddell Sea indicate that raised outflow temperatures are synchronous with stronger boundary current flows. These changes occur rapidly in response to changes in wind forcing, suggesting that barotropic dynamics and the response of the bottom Ekman layer are significant. The observed synchronicity indicates that the previously-detected weakening of the export of the colder forms of AABW from the Weddell Sea need not be associated with a reduction in the total flux of AABW exported via this route. These points need careful consideration when attributing the observed AABW warming in the Atlantic, and when determining its contribution to global heat budgets and sea level rise

Dense bottom layers in the Scotia Sea, Southern Ocean: Creation, lifespan, and destruction

The lower limb of the Atlantic overturning circulation is renewed by dense waters from the Southern Ocean, a substantial portion of which flow through the Scotia Sea. We report dense bottom layers here, with gradients in temperature and salinity comparable to those seen near the surface of the Southern Ocean. These are overlain by layers with much weaker stratification, and are caused by episodic overflows of dense waters across the South Scotia Ridge, and topographic trapping within deep trenches. One such layer was found to be at least 3–4 years older than the water immediately above. The estimated vertical diffusivity to which this layer was subject is substantially less than the strong basin-average deep mixing reported previously. We conjecture that (a) vertical mixing in the Scotia Sea is strongly spatially inhomogeneous, and (b) the flushing of these layers, like their formation, is related to overflow events, and hence also strongly episodic