Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea

Concentrations of oxygen (O<sub>2</sub>) and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes. The mixed layer depth (<i>z</i><sub>mix</sub>) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that <i>z</i><sub>mix</sub> defined using oxygen may be different than <i>z</i><sub>mix</sub> defined using temperature or density. Here, we propose to define an O<sub>2</sub>-based mixed layer depth, <i>z</i><sub>mix</sub>(O<sub>2</sub>), as the depth where the relative difference between the O<sub>2</sub> concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by analysis of O<sub>2</sub> profiles from the Bellingshausen Sea (west of the Antarctic Peninsula) and corroborated by visual inspection. Comparisons of <i>z</i><sub>mix</sub>(O<sub>2</sub>) with <i>z</i><sub>mix</sub> based on potential temperature differences, i.e., <i>z</i><sub>mix</sub>(0.2 °C) and <i>z</i><sub>mix</sub>(0.5 °C), and potential density differences, i.e., <i>z</i><sub>mix</sub>(0.03 kg m<sup>−3</sup>) and <i>z</i><sub>mix</sub>(0.125 kg m<sup>−3</sup>), showed that <i>z</i><sub>mix</sub>(O<sub>2</sub>) closely follows <i>z</i><sub>mix</sub>(0.03 kg m<sup>−3</sup>). Further comparisons with published <i>z</i><sub>mix</sub> climatologies and <i>z</i><sub>mix</sub> derived from World Ocean Atlas 2005 data were also performed. To establish <i>z</i><sub>mix</sub> for use with biological production estimates in the absence of O<sub>2</sub> profiles, we suggest using <i>z</i><sub>mix</sub>(0.03 kg m<sup>−3</sup>), which is also the basis for the climatology by de Boyer Montégut et al. (2004)

Dissolved methane in the sills region of the Gulf of California

An unusual combination of features makes the Midriff Islands region of the northern Gulf of California (NGC) a strong atmospheric methane source. Oceanographic isolation by a series of sills and islands along with upward transport of nutrient-rich water enhanced by tidal currents, upwelling, and overflows results in high productivity. The resulting high phytoplankton biomass likely stimulates biogeochemical cycling that, in turn, may stimulate biological methane production in the water column and sediments. Additionally, venting of abiogenic methane-rich hydrothermal fluids in this tectonically active area and seepage of biogenic or thermogenic methane gas from the sediments may also be important sources. We found elevated methane concentrations throughout our study area, the highest within the Ballenas Channel, which was supersaturated with respect to atmospheric methane at all depths. Our vertical methane profiles show that elevated dissolved methane concentrations in the NGC are mainly associated with Gulf of California Water (GCW). Data from 22 stations suggest southward advection of methane via the methane-rich GCW, and lower methane concentrations south of the sills area. Our observations of supersaturated methane concentrations at all stations and all depths in the Ballenas Channel suggest that it is a strong source of methane to the atmosphere and to other parts of the NGC. In particular, station 7 at 50, 20, and 0 m depths had methane (CH4) concentrations of 49.1, 48.3, and 43.5 nM, respectively, corresponding to saturation values of 2090%, 2050%, and 1850%, respectively. Our calculated NGC fluxes ranged from 3.4 to 103.4 µmol CH4 m–2 d–1. The average methane flux calculated for our entire study area was 21.1 µmol CH4 m–2 d–1. These values are higher than those measured at many other high productivity sites worldwide including upwelling sites, and suggest input of methane via hydrothermal fluids or seepage from the sediments. Key words: dissolved methane, gas chromatography, potential methane sources and origin.

ADELIE - Antarctic Drifter Experiment: Links to Isobaths and Ecosystems

The goal of the ADELIE research project is to map, for the first time, the near surface currents around the tip of the Antarctic Peninsula and to determine the role of these currents in the retention or dispersion of krill. Specifically, we will test the hypothesis that pathways to the west near the continent link current systems on the western and eastern sides of the the Peninsula. The influence of bathymetry controlling the splitting and steering of these frontal jets will also be studied. Data for the ADELIE project was collected during cruise JR158. We seek to resolve two important features of the current system around the margin of Antarctica, the Antarctic Slope Front and the Antarctic Coastal Current (see schematic in Figure 1). These currents both flow westward around the continent and are important for the transport of krill, for preconditioning the shelf waters, for the formation of Antarctic Bottom Water, and for supplying waters beneath ice shelves thus melting the underside of the ice shelf. The Antarctic Slope Front defines the boundary between cold, fresh waters filling the Antarctic continental shelf, and the warmer, more saline waters further offshore and is identified by a strong horizontal gradient in temperature and salinity. The Antarctic Coastal Current is a fast, shallow flow over the continental shelf often associated with the front of the ice shelf. The Coastal Current and the Slope Front may merge where the shelf is narrow, but over broad regions of the continental shelf the flows split into two distinct systems. The study area for JR158 is from the tip of the Antarctic Peninsula across the continental shelf and slope to the east and into the deep Weddell Sea (Figure 2). A CTD and Lowered ADCP section were conducted along this transect moving from east to west. This transect was selected to complement the western end of the WOCE SR4 time series, repeated annually by Eberhard Fahrbach and colleagues at the Alfred Wegener Institut (AWI) during the 1990’s. Due to the complexity of the topography in this region, Eulerian measurements at one site are not necessarily representative of the current system a short distance away. Therefore we also deployed surface drifters and Lagrangian floats as a means of tracking the currents. While surface drifters have been successfully released near the Antarctic continent during previous cruises, these drifters provide the first Lagrangian measurements of the current system on the eastern side of the Antarctic Peninsula. New instruments were also tested during JR158 including a microstructure profiler and a dissolved gas mass spectrometer. The microstructure profiler, which is used to resolve smallscale diapycnal mixing, will be used extensively during a mixing study near Kerguelen Island in 2008. The mass spectrometer measures dissolved oxygen/argon ratios that allow estimates of net community production over larger spatial scale with high temporal resolution

ADELIE - Antarctic Drifter Experiment: Links to Isobaths and Ecosystems

The goal of the ADELIE research project is to map, for the first time, the near surface currents around the tip of the Antarctic Peninsula and to determine the role of these currents in the retention or dispersion of krill. Specifically, we will test the hypothesis that pathways to the west near the continent link current systems on the western and eastern sides of the the Peninsula. The influence of bathymetry controlling the splitting and steering of these frontal jets will also be studied. Data for the ADELIE project was collected during cruise JR158. We seek to resolve two important features of the current system around the margin of Antarctica, the Antarctic Slope Front and the Antarctic Coastal Current (see schematic in Figure 1). These currents both flow westward around the continent and are important for the transport of krill, for preconditioning the shelf waters, for the formation of Antarctic Bottom Water, and for supplying waters beneath ice shelves thus melting the underside of the ice shelf. The Antarctic Slope Front defines the boundary between cold, fresh waters filling the Antarctic continental shelf, and the warmer, more saline waters further offshore and is identified by a strong horizontal gradient in temperature and salinity. The Antarctic Coastal Current is a fast, shallow flow over the continental shelf often associated with the front of the ice shelf. The Coastal Current and the Slope Front may merge where the shelf is narrow, but over broad regions of the continental shelf the flows split into two distinct systems. The study area for JR158 is from the tip of the Antarctic Peninsula across the continental shelf and slope to the east and into the deep Weddell Sea (Figure 2). A CTD and Lowered ADCP section were conducted along this transect moving from east to west. This transect was selected to complement the western end of the WOCE SR4 time series, repeated annually by Eberhard Fahrbach and colleagues at the Alfred Wegener Institut (AWI) during the 1990’s. Due to the complexity of the topography in this region, Eulerian measurements at one site are not necessarily representative of the current system a short distance away. Therefore we also deployed surface drifters and Lagrangian floats as a means of tracking the currents. While surface drifters have been successfully released near the Antarctic continent during previous cruises, these drifters provide the first Lagrangian measurements of the current system on the eastern side of the Antarctic Peninsula. New instruments were also tested during JR158 including a microstructure profiler and a dissolved gas mass spectrometer. The microstructure profiler, which is used to resolve smallscale diapycnal mixing, will be used extensively during a mixing study near Kerguelen Island in 2008. The mass spectrometer measures dissolved oxygen/argon ratios that allow estimates of net community production over larger spatial scale with high temporal resolution

Albiglutide and cardiovascular outcomes in patients with type 2 diabetes and cardiovascular disease (Harmony Outcomes): a double-blind, randomised placebo-controlled trial

Background: Glucagon-like peptide 1 receptor agonists differ in chemical structure, duration of action, and in their effects on clinical outcomes. The cardiovascular effects of once-weekly albiglutide in type 2 diabetes are unknown. We aimed to determine the safety and efficacy of albiglutide in preventing cardiovascular death, myocardial infarction, or stroke. Methods: We did a double-blind, randomised, placebo-controlled trial in 610 sites across 28 countries. We randomly assigned patients aged 40 years and older with type 2 diabetes and cardiovascular disease (at a 1:1 ratio) to groups that either received a subcutaneous injection of albiglutide (30–50 mg, based on glycaemic response and tolerability) or of a matched volume of placebo once a week, in addition to their standard care. Investigators used an interactive voice or web response system to obtain treatment assignment, and patients and all study investigators were masked to their treatment allocation. We hypothesised that albiglutide would be non-inferior to placebo for the primary outcome of the first occurrence of cardiovascular death, myocardial infarction, or stroke, which was assessed in the intention-to-treat population. If non-inferiority was confirmed by an upper limit of the 95% CI for a hazard ratio of less than 1·30, closed testing for superiority was prespecified. This study is registered with ClinicalTrials.gov, number NCT02465515. Findings: Patients were screened between July 1, 2015, and Nov 24, 2016. 10 793 patients were screened and 9463 participants were enrolled and randomly assigned to groups: 4731 patients were assigned to receive albiglutide and 4732 patients to receive placebo. On Nov 8, 2017, it was determined that 611 primary endpoints and a median follow-up of at least 1·5 years had accrued, and participants returned for a final visit and discontinuation from study treatment; the last patient visit was on March 12, 2018. These 9463 patients, the intention-to-treat population, were evaluated for a median duration of 1·6 years and were assessed for the primary outcome. The primary composite outcome occurred in 338 (7%) of 4731 patients at an incidence rate of 4·6 events per 100 person-years in the albiglutide group and in 428 (9%) of 4732 patients at an incidence rate of 5·9 events per 100 person-years in the placebo group (hazard ratio 0·78, 95% CI 0·68–0·90), which indicated that albiglutide was superior to placebo (p<0·0001 for non-inferiority; p=0·0006 for superiority). The incidence of acute pancreatitis (ten patients in the albiglutide group and seven patients in the placebo group), pancreatic cancer (six patients in the albiglutide group and five patients in the placebo group), medullary thyroid carcinoma (zero patients in both groups), and other serious adverse events did not differ between the two groups. There were three (<1%) deaths in the placebo group that were assessed by investigators, who were masked to study drug assignment, to be treatment-related and two (<1%) deaths in the albiglutide group. Interpretation: In patients with type 2 diabetes and cardiovascular disease, albiglutide was superior to placebo with respect to major adverse cardiovascular events. Evidence-based glucagon-like peptide 1 receptor agonists should therefore be considered as part of a comprehensive strategy to reduce the risk of cardiovascular events in patients with type 2 diabetes. Funding: GlaxoSmithKline

Canagliflozin and renal outcomes in type 2 diabetes and nephropathy

BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to <90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], >300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P<0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe