Latitudinal structure of the meridional overturning circulation variability on interannual to decadal time scales in the North Atlantic Ocean

Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 33(9), (2020): 3845-3862, doi:10.1175/JCLI-D-19-0215.1.The latitudinal structure of the Atlantic meridional overturning circulation (AMOC) variability in the North Atlantic is investigated using numerical results from three ocean circulation simulations over the past four to five decades. We show that AMOC variability south of the Labrador Sea (53°N) to 25°N can be decomposed into a latitudinally coherent component and a gyre-opposing component. The latitudinally coherent component contains both decadal and interannual variabilities. The coherent decadal AMOC variability originates in the subpolar region and is reflected by the zonal density gradient in that basin. It is further shown to be linked to persistent North Atlantic Oscillation (NAO) conditions in all three models. The interannual AMOC variability contained in the latitudinally coherent component is shown to be driven by westerlies in the transition region between the subpolar and the subtropical gyre (40°–50°N), through significant responses in Ekman transport. Finally, the gyre-opposing component principally varies on interannual time scales and responds to local wind variability related to the annual NAO. The contribution of these components to the total AMOC variability is latitude-dependent: 1) in the subpolar region, all models show that the latitudinally coherent component dominates AMOC variability on interannual to decadal time scales, with little contribution from the gyre-opposing component, and 2) in the subtropical region, the gyre-opposing component explains a majority of the interannual AMOC variability in two models, while in the other model, the contributions from the coherent and the gyre-opposing components are comparable. These results provide a quantitative decomposition of AMOC variability across latitudes and shed light on the linkage between different AMOC variability components and atmospheric forcing mechanisms.The authors gratefully acknowledge support from the Physical Oceanography Program of the U.S. National Science Foundation (Awards OCE-1756143 and OCE-1537136) and the Climate Program Office of the National Oceanic and Atmospheric Administration (Award NA15OAR4310088). Gratitude is extended to Claus Böning and Arne Biastoch who shared ORCA025 output. S. Zou thanks F. Li, M. Buckley, and L. Li for helpful discussions. We also thank three anonymous reviewers for helpful suggestions

Redrawing the Iceland−Scotland overflow water pathways in the North Atlantic

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Zou, S., Bower, A., Furey, H., Susan Lozier, M., & Xu, X. Redrawing the Iceland−Scotland overflow water pathways in the North Atlantic. Nature Communications, 11(1), (2020): 890, doi:10.1038/s41467-020-15513-4.Iceland-Scotland Overflow Water (ISOW) is a primary deep water mass exported from the Norwegian Sea into the North Atlantic as part of the global Meridional Overturning Circulation. ISOW has historically been depicted as flowing counter-clockwise in a deep boundary current around the subpolar North Atlantic, but this single-boundary-following pathway is being challenged by new Lagrangian observations and model simulations. We show here that ISOW leaves the boundary and spreads into the interior towards the central Labrador and Irminger basins after flowing through the Charlie-Gibbs Fracture Zone. We also describe a newly observed southward pathway of ISOW along the western flank of the Mid-Atlantic Ridge. The partitioning of these pathways is shown to be influenced by deep-reaching eddies and meanders of the North Atlantic Current. Our results, in tandem with previous studies, call for a revision in the historical depiction of ISOW pathways throughout the North Atlantic.S.Z., A.B. and H.F. gratefully acknowledge the support from the Physical Oceanography Program of the U.S. National Science Foundation (grant number OCE-17-56361). S.Z. and M.S.L. also acknowledge support from NSF-OCE-17-56143. X.X. acknowledges support from NSF award 1537136. Gratitude is also extended to C. Böning and A. Biastoch for sharing FLAME output and trajectory calculation code

Observed deep cyclonic eddies around Southern Greenland

Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(10), (2021): 3235–3252, https://doi.org/10.1175/JPO-D-20-0288.1.Recent mooring measurements from the Overturning in the Subpolar North Atlantic Program have revealed abundant cyclonic eddies at both sides of Cape Farewell, the southern tip of Greenland. In this study, we present further observational evidence, from both Eulerian and Lagrangian perspectives, of deep cyclonic eddies with intense rotation (ζ/f > 1) around southern Greenland and into the Labrador Sea. Most of the observed cyclones exhibit strongest rotation below the surface at 700–1000 dbar, where maximum azimuthal velocities are ~30 cm s−1 at radii of ~10 km, with rotational periods of 2–3 days. The cyclonic rotation can extend to the deep overflow water layer (below 1800 dbar), albeit with weaker azimuthal velocities (~10 cm s−1) and longer rotational periods of about one week. Within the middepth rotation cores, the cyclones are in near solid-body rotation and have the potential to trap and transport water. The first high-resolution hydrographic transect across such a cyclone indicates that it is characterized by a local (both vertically and horizontally) potential vorticity maximum in its middepth core and cold, fresh anomalies in the deep overflow water layer, suggesting its source as the Denmark Strait outflow. Additionally, the propagation and evolution of the cyclonic eddies are illustrated with deep Lagrangian floats, including their detachments from the boundary currents to the basin interior. Taken together, the combined Eulerian and Lagrangian observations have provided new insights on the boundary current variability and boundary–interior exchange over a geographically large scale near southern Greenland, calling for further investigations on the (sub)mesoscale dynamics in the region.OOI mooring data are based upon work supported by the National Science Foundation under Cooperative Agreement 1743430. S. Zou, A. Bower, and H. Furey gratefully acknowledge the support from the Physical Oceanography Program of the U.S. National Science Foundation Grant OCE-1756361. R.S. Pickart acknowledges support from National Science Foundation Grants OCE-1259618 and OCE-1756361. N. P. Holliday and L. Houpert were supported by NERC programs U.K. OSNAP (NE/K010875) and U.K. OSNAP-Decade (NE/T00858X/1)

Observed deep cyclonic eddies around Southern Greenland

Recent mooring measurements from the Overturning in the Subpolar North Atlantic Program have revealed abundant cyclonic eddies at both sides of Cape Farewell, the southern tip of Greenland. In this study, we present further observational evidence, from both Eulerian and Lagrangian perspectives, of deep cyclonic eddies with intense rotation (ζ/f > 1) around southern Greenland and into the Labrador Sea. Most of the observed cyclones exhibit strongest rotation below the surface at 700–1000 dbar, where maximum azimuthal velocities are ~30 cm s−1 at radii of ~10 km, with rotational periods of 2–3 days. The cyclonic rotation can extend to the deep overflow water layer (below 1800 dbar), albeit with weaker azimuthal velocities (~10 cm s−1) and longer rotational periods of about one week. Within the middepth rotation cores, the cyclones are in near solid-body rotation and have the potential to trap and transport water. The first high-resolution hydrographic transect across such a cyclone indicates that it is characterized by a local (both vertically and horizontally) potential vorticity maximum in its middepth core and cold, fresh anomalies in the deep overflow water layer, suggesting its source as the Denmark Strait outflow. Additionally, the propagation and evolution of the cyclonic eddies are illustrated with deep Lagrangian floats, including their detachments from the boundary currents to the basin interior. Taken together, the combined Eulerian and Lagrangian observations have provided new insights on the boundary current variability and boundary–interior exchange over a geographically large scale near southern Greenland, calling for further investigations on the (sub)mesoscale dynamics in the region

Implications for Cation Selectivity and Evolution by a Novel Cation Diffusion Facilitator Family Member From the Moderate Halophile Planococcus dechangensis

In the cation diffusion facilitator (CDF) family, the transported substrates are confined to divalent metal ions, such as Zn2+, Fe2+, and Mn2+. However, this study identifies a novel CDF member designated MceT from the moderate halophile Planococcus dechangensis. MceT functions as a Na+(Li+, K+)/H+ antiporter, together with its capability of facilitated Zn2+ diffusion into cells, which have not been reported in any identified CDF transporters as yet. MceT is proposed to represent a novel CDF group, Na-CDF, which shares significantly distant phylogenetic relationship with three known CDF groups including Mn-CDF, Fe/Zn-CDF, and Zn-CDF. Variation of key function-related residues to “Y44-S48-Q150” in two structural motifs explains a significant discrimination in cation selectivity between Na-CDF group and three major known CDF groups. Functional analysis via site-directed mutagenesis confirms that MceT employs Q150, S158, and D184 for the function of MceT as a Na+(Li+, K+)/H+ antiporter, and retains D41, D154, and D184 for its facilitated Zn2+ diffusion into cells. These presented findings imply that MceT has evolved from its native CDF family function to a Na+/H+ antiporter in an evolutionary strategy of the substitution of key conserved residues to “Q150-S158-D184” motif. More importantly, the discovery of MceT contributes to a typical transporter model of CDF family with the unique structural motifs, which will be utilized to explore the cation-selective mechanisms of secondary transporters

Associations between plasma metal mixture exposure and risk of hypertension: A cross-sectional study among adults in Shenzhen, China

BackgroundMetal exposure affects human health. Current studies mainly focus on the individual health effect of metal exposure on hypertension (HTN), and the results remain controversial. Moreover, the studies assessing overall effect of metal mixtures on hypertension risk are limited.MethodsA cross-sectional study was conducted by recruiting 1,546 Chinese adults who attended routine medical check-ups at the Eighth Affiliated Hospital of Sun Yat-sen University, Shenzhen. The plasma levels of 13 metals were measured using inductively coupled plasma mass spectrometry. Multivariate logistic regression model, restricted cubic spline (RCS) model and the Bayesian Kernel Machine Regression (BKMR) model were applied to explore the single and combined effect of metals on the risk of HTN.ResultsA total of 642 (41.5%) participants were diagnosed with HTN. In the logistic regression model, the adjusted odds ratios (ORs) were 0.71 (0.52, 0.97) for cobalt, 1.40 (1.04, 1.89) for calcium, 0.66 (0.48, 0.90), and 0.60 (0.43, 0.83) for aluminum in the second and third quartile, respectively. The RCS analysis showed a V-shaped or an inverse V-shaped dose-response relationship between metals (aluminum or calcium, respectively) and the risk of HTN (P for non-linearity was 0.017 or 0.009, respectively). However, no combined effect was found between metal mixture and the risk of hypertension.ConclusionsPlasma levels of cobalt, aluminum and calcium were found to be associated with the risk of HTN. Further studies are needed to confirm our findings and their potential mechanisms with prospective studies and experimental study designs

KUS121, a VCP modulator, has an ameliorating effect on acute and chronic heart failure without calcium loading via maintenance of intracellular ATP levels

KUS121は新規の心不全治療薬となる --Ca2+負荷なしに血行動態を改善--. 京都大学プレスリリース. 2023-12-15.[Aims] As heart failure (HF) progresses, ATP levels in myocardial cells decrease, and myocardial contractility also decreases. Inotropic drugs improve myocardial contractility but increase ATP consumption, leading to poor prognosis. Kyoto University Substance 121 (KUS121) is known to selectively inhibit the ATPase activity of valosin-containing protein, maintain cellular ATP levels, and manifest cytoprotective effects in several pathological conditions. The aim of this study is to determine the therapeutic effect of KUS121 on HF models. [Methods and results] Cultured cell, mouse, and canine models of HF were used to examine the therapeutic effects of KUS121. The mechanism of action of KUS121 was also examined. Administration of KUS121 to a transverse aortic constriction (TAC)-induced mouse model of HF rapidly improved the left ventricular ejection fraction and improved the creatine phosphate/ATP ratio. In a canine model of high frequency-paced HF, administration of KUS121 also improved left ventricular contractility and decreased left ventricular end-diastolic pressure without increasing the heart rate. Long-term administration of KUS121 to a TAC-induced mouse model of HF suppressed cardiac hypertrophy and fibrosis. In H9C2 cells, KUS121 reduced ER stress. Finally, in experiments using primary cultured cardiomyocytes, KUS121 improved contractility and diastolic capacity without changing peak Ca²⁺ levels or contraction time. These effects were not accompanied by an increase in cyclic adenosine monophosphate or phosphorylation of phospholamban and ryanodine receptors. [Conclusions] KUS121 ameliorated HF by a mechanism totally different from that of conventional catecholamines. We propose that KUS121 is a promising new option for the treatment of HF

Moored observations of the Iceland-Scotland Overflow plume along the eastern flank of the Reykjanes Ridge

Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(8), (2021): e2021JC017524, https://doi.org/10.1029/2021JC017524.Since 2014, an array of current meters deployed in the Iceland Basin as part of the Overturning in the Subpolar North Atlantic Program has provided new measurements of the southward flow of Iceland-Scotland Overflow Water (ISOW) along the eastern flank of the Reykjanes Ridge. The location of the array, near 58–59°N, captures the ISOW plume at the farthest downstream location in the Iceland Basin before significant amounts of ISOW can flow into the Irminger Basin through deep fractures in the Reykjanes Ridge. The net transport of the ISOW plume at this location—approximately 5.3 Sv based on the first 4 years of observations—is significantly larger than previous values obtained farther north in the Iceland Basin, suggesting that either previous measurements did not fully capture the plume transport or that additional entrainment into the ISOW plume occurs as it approaches the southern tip of the Reykjanes Ridge. A detailed water mass analysis of the plume from continuous temperature/salinity observations shows that about 50% of the plume transport (2.6 Sv) is derived from dense waters flowing over the Nordic Sea sills into the Iceland Basin, while the remainder is made up of nearly equal parts of entrained Atlantic thermocline water and modified Labrador Sea Water. The overall results from this study suggest that the ISOW plume approximately doubles its transport through entrainment, similar to that of the Denmark Strait overflow plume in the Irminger Sea that forms the other major overflow source of North Atlantic Deep Water.Financial support for this research was provided by the U.S. National Science Foundation under grants OCE-1259398 and OCE-1756231. S. Zou acknowledges support by the U.S. National Science Foundation under grant OCE-1756361.2022-02-1