scholarly journals Dissolution of cobalt and zinc from natural and anthropogenic dusts in seawater

2010 ◽  
Vol 7 (6) ◽  
pp. 1927-1936 ◽  
Author(s):  
C.-E. Thuróczy ◽  
M. Boye ◽  
R. Losno
Keyword(s):  
Mixed Layer ◽  
Flow Reactor ◽  
Anthropogenic Sources ◽  
Anthropogenic Aerosol ◽  
Surface Ocean ◽  
Anthropogenic Inputs ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Voltammetric Methods

Abstract. Atmospheric dust inputs to the surface ocean are a major source of trace metals likely to be bio-available for phytoplankton after their dissolution in seawater. Among them, cobalt (Co) and zinc (Zn) are essential for phytoplankton growth and for the distribution of the major groups such as coccolithophorids, cyanobacteria and diatoms. The solubility in seawater of Co and Zn present in natural and anthropogenic dusts was studied using an open-flow reactor with and without light irradiation. Those dusts can be transported in the atmosphere by the wind before being deposited to the surface ocean. The analyses of cobalt and zinc were conducted using voltammetric methods and the global elemental composition of dust was determined by ICP-AES. This study highlighted the role of the dust origin in revealing the solubility characteristics. Much higher dust solubility was found for zinc as compared to cobalt; cobalt in anthropogenic particles was much more soluble (0.78%) in seawater after 2 h of dissolution than Co in natural particles (0.14%). Zinc showed opposite solubility, higher in natural particles (16%) than in anthropogenic particles (5.2%). A natural dust event to the surface ocean could account for up to 5% of the cobalt inventory and up to 50% of the Zn inventory in the mixed layer in the Pacific Ocean whereas the cobalt and zinc inventories in the mixed layer of the Atlantic Ocean might already include the effects of natural dust inputs and the subsequent metal dissolution. Anthropogenic sources to the surface ocean could be as important as the natural sources, but a better estimate of the flux of anthropogenic aerosol to the surface ocean is needed to further estimate the anthropogenic inputs. Variations in natural and anthropogenic inputs may induce large shifts in the Co/Zn ratio in the surface ocean; hence it could impact the phytoplankton community structure.

scholarly journals Surface ocean iron fertilization: The role of airborne volcanic ash from subduction zone and hot spot volcanoes and related iron fluxes into the Pacific Ocean

2011 ◽  
Vol 25 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Nazlı Olgun ◽  
Svend Duggen ◽  
Peter Leslie Croot ◽  
Pierre Delmelle ◽  
Heiner Dietze ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Subduction Zone ◽  
Volcanic Ash ◽  
Hot Spot ◽  
Surface Ocean ◽  
Iron Fertilization ◽  
The Pacific ◽  
The Pacific Ocean

scholarly journals Lewis fry Richardson Medal Lecture – How many modes are neededto predict climate bifurcations?: Lessons from an experiment

2021 ◽  
Author(s):  
Bérengère Dubrulle ◽  
François Daviaud ◽  
Davide Faranda ◽  
Louis Marié ◽  
Brice Saint-Michel
Keyword(s):  
Degrees Of Freedom ◽  
Climate Models ◽  
Environmental Policies ◽  
Climate Projections ◽  
Finite Resolution ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Lewis Fry Richardson ◽  
Do So

Abstract. According to everyone’s experience, predicting the weather reliably over more than 8 days seems an impossible taskfor our best weather agencies. At the same time, politicians and citizens are asking scientists for climate projections severaldecades into the future to guide economic and environmental policies, especially regarding the maximum admissible emissions of CO2. To what extent is this request scientifically admissible? In this lecture we will investigate this question, focusing on the topic of predictions of transitions between metastable statesof the atmospheric or oceanic circulations. Two relevant exemples are the switching between zonal and blocked atmosphericcirculation at midlatitudes and the alternance of El Niño and La Niña phases in the Pacific ocean. The main issue is whetherpresent climate models, that necessarily have a finite resolution and a smaller number of degrees of freedom than the actualterrestrial system, are able to reproduce such spontaneous or forced transitions. To do so, we will draw an analogy betweenclimate observations and results obtained in our group on a laboratory-scale, turbulent, von Kármán flow, in which spontaneoustransitions between different states of the circulation take place. We will detail the analogy, and investigate the nature of thetransitions, the number of degrees of freedom that characterizes the latter and discuss the effect of reducing the number ofdegrees of freedom in such systems. We will also discuss the role of fluctuations and their origin, and stress the importance ofdescribing very small scales to capture fluctuations of correct intensity and scale.

scholarly journals Proteorhodopsins dominate the expression of phototrophic mechanisms in seasonal and dynamic marine picoplankton communities

2018 ◽  
Author(s):  
Ella T Sieradzki ◽  
Jed A Fuhrman ◽  
Sara Rivero-Calle ◽  
Laura Gómez-Consarnau
Keyword(s):  
Marker Gene ◽  
Single Copy ◽  
Oxygenic Photosynthesis ◽  
Sampling Location ◽  
Pr Genes ◽  
Surface Ocean ◽  
San Pedro ◽  
Accessory Function ◽  
The Pacific ◽  
The Pacific Ocean

The most abundant and ubiquitous microbes in the surface ocean use light as an energy source, capturing it via complex chlorophyll-based photosystems or simple retinal-based rhodopsins. Studies in various ocean regimes compared the abundance of these mechanisms, but few investigated their expression. Here we present the first full seasonal study of abundance and expression of light-harvesting mechanisms (proteorhodopsin, PR; aerobic anoxygenic photosynthesis, AAnP; and oxygenic photosynthesis, PSI) from deep-sequenced metagenomes and metatranscriptomes of marine picoplankton (< 1 µm) at three coastal stations of the San Pedro Channel in the Pacific Ocean. We show that, regardless of season or sampling location, the most common phototrophic mechanism in metagenomes of this dynamic region was PR (present in 65-104% of the genomes as estimated by single-copy recA), followed by PSI (5-104%) and AAnP (5-32%). Furthermore, the normalized expression (RNA to DNA ratio) of PR genes was higher than that of oxygenic photosynthesis (average±standard deviation 26.2±8.4 vs. 11±9.7), and the expression of the AAnP marker gene was significantly lower than both mechanisms (0.013±0.02). We demonstrate that rhodopsin expression was dominated by the SAR11-cluster year-round, followed by other Alphaproteobacteria, unknown-environmental clusters and Gammaproteobacteria. This highly dynamic system further allowed us to identify a trend for PR spectral tuning, in which blue-absorbing PR genes dominate in areas with low chlorophyll-aconcentrations (< 0.25 µg/L). This suggests that PR phototrophy is not an accessory function but instead a central mechanism that can regulate photoheterotrophic population dynamics.

scholarly journals Observed Interhemispheric Meridional Heat Transports and the Role of the Indonesian Throughflow in the Pacific Ocean

2019 ◽  
Vol 32 (24) ◽  
pp. 8523-8536 ◽  
Author(s):  
Kevin E. Trenberth ◽  
Yongxin Zhang
Keyword(s):  
El Niño ◽  
El Nino ◽  
Heat Content ◽  
Indonesian Throughflow ◽  
Annual Cycles ◽  
Surface Energy Flux ◽  
The Pacific ◽  
Tasman Sea ◽  
The Pacific Ocean

Abstract The net surface energy flux is computed as a residual of the energy budget using top-of-atmosphere radiation combined with the divergence of the column-integrated atmospheric energy transports, and then used with the vertically integrated ocean heat content tendencies to compute the ocean meridional heat transports (MHTs). The mean annual cycles and 12-month running mean MHTs as a function of latitude are presented for 2000–16. Effects of the Indonesian Throughflow (ITF), associated with a net volume flow around Australia accompanied by a heat transport, are fully included. Because the ITF-related flow necessitates a return current northward in the Tasman Sea that relaxes during El Niño, the reduced ITF during El Niño may contribute to warming in the south Tasman Sea by allowing the East Australian Current to push farther south even as it gains volume from the tropical waters not flowing through the ITF. Although evident in 2015/16, when a major marine heat wave occurred, these effects can be overwhelmed by changes in the atmospheric circulation. Large interannual MHT variability in the Pacific is 4 times that of the Atlantic. Strong relationships reveal influences from the southern subtropics on ENSO for this period. At the equator, northward ocean MHT arises mainly in the Atlantic (0.75 PW), offset by the Pacific (−0.33 PW) and Indian Oceans (−0.20 PW) while the atmosphere transports energy southward (−0.35 PW). The net equatorial MHT southward (−0.18 PW) is enhanced by −0.1 PW that contributes to the greater warming of the southern (vs northern) oceans.

scholarly journals Proteorhodopsins dominate the expression of phototrophic mechanisms in seasonal and dynamic marine picoplankton communities

2018 ◽  
Author(s):  
Ella T Sieradzki ◽  
Jed A Fuhrman ◽  
Sara Rivero-Calle ◽  
Laura Gómez-Consarnau
Keyword(s):  
Marker Gene ◽  
Single Copy ◽  
Oxygenic Photosynthesis ◽  
Sampling Location ◽  
Pr Genes ◽  
Surface Ocean ◽  
San Pedro ◽  
Accessory Function ◽  
The Pacific ◽  
The Pacific Ocean

The most abundant and ubiquitous microbes in the surface ocean use light as an energy source, capturing it via complex chlorophyll-based photosystems or simple retinal-based rhodopsins. Studies in various ocean regimes compared the abundance of these mechanisms, but few investigated their expression. Here we present the first full seasonal study of abundance and expression of light-harvesting mechanisms (proteorhodopsin, PR; aerobic anoxygenic photosynthesis, AAnP; and oxygenic photosynthesis, PSI) from deepsequenced metagenomes and metatranscriptomes of marine picoplankton (< 1 μm) at three coastal stations of the San Pedro Channel in the Pacific Ocean. We show that, regardless of season or sampling location, the most common phototrophic mechanism in metagenomes of this dynamic region was PR (present in 65-104% of the genomes as estimated by single-copy recA), followed by PSI (5-104%) and AAnP (5-32%). Furthermore, the normalized expression (RNA to DNA ratio) of PR genes was higher than that of oxygenic photosynthesis (average±standard deviation 26.2±8.4 vs. 11±9.7), and the expression of the AAnP marker gene was significantly lower than both mechanisms (0.013±0.02). We demonstrate that PR expression was dominated by the SAR11-cluster year-round, followed by other Alphaproteobacteria, unknown-environmental clusters and Gammaproteobacteria. This highly dynamic system further allowed us to identify a trend for PR spectral tuning, in which blue-absorbing PR genes dominate in areas with low chlorophyll-a concentrations (< 0.25 μgL-1). This suggests that PR phototrophy is not an accessory function but instead a central mechanism that can regulate photoheterotrophic population dynamics.

Evolution of the ocean monsoon regions over the past 250 million years

2021 ◽  
Author(s):  
Jing Han ◽  
Yongyun Hu ◽  
Yonggang Liu
Keyword(s):  
Pacific Ocean ◽  
Mixed Layer ◽  
Ocean Basin ◽  
Subtropical High ◽  
Monsoon Region ◽  
Ocean Mixed Layer ◽  
The Past ◽  
The Pacific ◽  
Monsoon Area ◽  
The Pacific Ocean

&lt;p&gt;A set of deep-time climate simulations each 10Ma years from 250Ma to PI are conducted by using the NCAR-CESM1.2, for understanding the evolution of the ocean monsoon regions driven by tectonic dynamics over the past 250 million years and exploring its variation mechanisms. In recent years, scientists have proposed the concept of a global monsoon system, which includes not only typical monsoon regions (such as the African monsoon region and South Asian monsoon region), but also the atypical Northwest Pacific Ocean monsoon region. Research on the ocean monsoon is very limited, especially in the field of paleoclimate. The results in this paper show that the horizontal gradients of the thickness of the ocean mixed layer may be more important for the formation of the ocean monsoon than land-sea thermal contrast, which is confirmed by the aquaplanet simulations with various gradients of the ocean mixed-layer thickness. Near the Pacific monsoon region in the northern hemisphere, the thickness of the ocean mixed layer has obvious meridional and zonal gradients, which will correspond to the meridional and zonal thermal contrasts. In addition, there are obvious seasonal reversals in the gradients of the ocean mixed-layer thickness in summer and winter, and the corresponding longitudinal and zonal thermal contrast produce seasonal reversals. Over the past 250 million years, the thickness of the ocean mixed layer on the east side of the Pacific Ocean Basin in the Northern Hemisphere has deepened, and the corresponding ocean monsoon area on the east side of the Pacific Ocean has decreased. The changes in the thickness of the ocean mixed layer are closely related to the changes in the surface wind field. Examining the changes in the atmospheric circulations, we find that the Pacific subtropical high strengthens and extends from east to the west bank of the ocean basin, where the atmospheric low-level anticyclonic circulation causes the ocean surface layer to converge and sink and thus causes the ocean mixed layer to deepen. The changes in the Pacific subtropical high are related to changes in the continental monsoon region. Since the 170Ma, the Pangea supercontinent splits up, causing the supercontinent's inland water vapor to increase, the land monsoon area to increase, and the ocean monsoon area to decrease. According to the &quot;monsoon-desert mechanism&quot; of Rodwell and Hoskins, we can understand the relationship between the strengthening of land monsoon condensation heating and the formation of subtropical high over the western ocean.&lt;/p&gt;

Bordering on Crisis

2021 ◽  
pp. 269-289
Author(s):  
Brian Wilson ◽  
Nora Johnson
Keyword(s):  
United Nations ◽  
Crisis Management ◽  
Security Council ◽  
Crisis Response ◽  
United Nations Security Council ◽  
The Pacific ◽  
Terrorist Organization ◽  
Scant Attention ◽  
The Pacific Ocean

A vessel plying the Pacific Ocean with approximately 500 migrants, some of whom might have deadly contagions, along with members of a terrorist organization, is emblematic of contemporary multiagency crisis response challenges: vague reports, agencies with overlapping authorities, balancing competing legal considerations, and an urgency to act. While crisis management isn’t new, the strategic response landscape now includes formal collaborative frameworks. A key element of interagency alignment involves lawyers who are increasingly being called upon to advise in crisis situations. More than a dozen states, multilateral instruments, and United Nations Security Council resolutions formally acknowledge the benefits of collaboration to address threats, yet the elements and competencies, as well as inclusion, of crisis lawyering receive scant attention. This chapter examines the role of an attorney in an inter-agency crisis management and includes “Rules for Crisis Lawyering in a Multiagency Environment.”

scholarly journals Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium

2015 ◽  
Vol 12 (24) ◽  
pp. 7519-7533 ◽  
Author(s):  
R. Steinfeldt ◽  
J. Sültenfuß ◽  
M. Dengler ◽  
T. Fischer ◽  
M. Rhein
Keyword(s):  
Mixed Layer ◽  
Coastal Upwelling ◽  
Regional Distribution ◽  
Ekman Transport ◽  
Helium Isotope ◽  
Net Community Production ◽  
Vertical Diffusivity ◽  
The Pacific ◽  
Order Of Magnitude ◽  
The Pacific Ocean

Abstract. Upwelling is an important process, bringing gases and nutrients into the ocean mixed layer. The upwelling velocities, however, are too small to be measured directly. Here we use the surface disequilibrium of the 3He / 4He ratio measured in two coastal upwelling regions off Peru in the Pacific ocean and off Mauritania in the Atlantic ocean to calculate the regional distribution of vertical velocities. To also account for the fluxes by diapycnal mixing, microstructure-based observations of the vertical diffusivity have been performed on all four cruises analysed in this study. The upwelling velocities in the coastal regions vary between 1.1 ± 0.3 × 10−5 and 2.8 ± 1.5 × 10−5 m s−1 for all cruises. Vertical velocities are also inferred from the divergence of the wind-driven Ekman transport. In the coastal regimes, both methods agree within the error range. Further offshore, the helium-derived vertical velocity still reaches 1 × 10−5 m s−1, whereas the wind-driven upwelling from Ekman suction is smaller by up to 1 order of magnitude. One reason for this difference is ascribed to eddy-induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium-derived vertical velocities and the vertical diffusivities. The advective part of these fluxes makes up at about 50 % of the total. The nutrient flux into the mixed layer in the coastal upwelling regimes is equivalent to a net community production (NCP) of 1.3 ± 0.3 g C m2 d−1 off Peru and 1.6–2.1 ± 0.5 g C m2 d−1 off Mauritania.

Near-N Oscillations and Deep-Cycle Turbulence in an Upper-Equatorial Undercurrent Model

2012 ◽  
Vol 42 (12) ◽  
pp. 2169-2184 ◽  
Author(s):  
Hieu T. Pham ◽  
Sutanu Sarkar ◽  
Kraig B. Winters
Keyword(s):  
Mixed Layer ◽  
Turbulent Mixing ◽  
Three Dimensional ◽  
Surface Mixed Layer ◽  
Local Velocity ◽  
Equatorial Undercurrent ◽  
Frequency Matching ◽  
The Pacific ◽  
Horseshoe Vortices

Abstract Direct numerical simulation (DNS) is used to investigate the role of shear instabilities in turbulent mixing in a model of the upper Equatorial Undercurrent (EUC). The background flow consists of a westward-moving surface mixed layer above a stably stratified EUC flowing to the east. An important characteristic of the eastward current is that the gradient Richardson number Rig is larger than ¼. Nevertheless, the overall flow is unstable and DNS is used to investigate the generation of intermittent bursts of turbulent motions within the EUC region where Rig &gt; ¼. In this model, an asymmetric Holmboe instability emerges at the base of the mixed layer, moves at the speed of the local velocity, and ejects wisps of fluid from the EUC upward. At the crests of the Holmboe waves, secondary Kelvin–Helmholtz instabilities develop, leading to three-dimensional turbulent motions. Vortices formed by the Kelvin–Helmholtz instability are occasionally ejected downward and stretched by the EUC into a horseshoe configuration creating intermittent bursts of turbulence at depth. Vertically coherent oscillations, with wavelength and frequency matching those of the Holmboe waves, propagate horizontally in the EUC where the turbulent mixing by the horseshoe vortices occurs. The oscillations are able to transport momentum and energy from the mixed layer downward into the EUC. They do not overturn the isopycnals, however, and, though correlated in space and time with the turbulent bursts, are not directly responsible for their generation. These wavelike features and intermittent turbulent bursts are qualitatively similar to the near-N oscillations and the deep-cycle turbulence observed at the upper flank of the Pacific Equatorial Undercurrent.

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