Heme b distributions through the Atlantic Ocean: in situ identification of iron limited phytoplankton

2020 ◽  
Author(s):  
Evangelia Louropoulou ◽  
Martha Gledhill ◽  
Eric P. Achterberg ◽  
Thomas J. Browning ◽  
David J. Honey ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Large Scale ◽  
North Atlantic Ocean ◽  
Iron Status ◽  
Mean Value ◽  
Particulate Material ◽  
South Atlantic ◽  
Phytoplankton Communities ◽  
The Impact

<p>Heme <em>b</em> is an iron-containing cofactor in hemoproteins that participates in the fundamental processes of photosynthesis and respiration in phytoplankton. Heme <em>b</em> concentrations typically decline in waters with low iron concentrations but due to lack of field data, the distribution of heme <em>b</em> in particulate material in the ocean is poorly constrained. Within the framework of the Helmholtz Research School for Ocean System Science and Technology (HOSST) and the GEOTRACES programme, the authors compiled datasets and conducted multidisciplinary research (e.g. chemical oceanography, microbiology, biogeochemical modelling) in order to test heme <em>b</em> as an indicator of <em>in situ</em> iron-limited phytoplankton. This study was initiated in the North Atlantic Ocean and expanded to the under-sampled South Atlantic Ocean for comparison of the results considering the different phytoplankton populations. Here, we report particulate heme <em>b</em> distributions across the Atlantic Ocean (59.9°N to 34.6°S). Heme <em>b</em> concentrations in surface waters ranged from 0.10 to 33.7 pmol L<sup>-1</sup> (median=1.47 pmol L<sup>-1</sup>, n=974) and were highest in regions with a high biomass. The ratio of heme <em>b</em> to particulate organic carbon (POC) exhibited a mean value of 0.44 μmol heme<em> b</em> mol<sup>-1 </sup>POC. We identified the ratio of 0.10 µmol heme <em>b</em> mol<sup>-1</sup> POC as the cut-off between heme <em>b</em> replete and heme <em>b</em> deficient phytoplankton. By this definition, the ratio heme <em>b</em> relative to POC was consistently below 0.10 μmol mol<sup>-1</sup> in areas characterized by low Fe supply; these were the Subtropical South Atlantic gyre and the seasonally iron limited Irminger Basin. Thus, the ratio heme <em>b</em> relative to POC gave a reliable indication of iron limited phytoplankton communities in situ. Furthermore, the comparison of observed and modelled heme <em>b</em> suggested that heme <em>b</em> could account for between 0.17-9.1% of biogenic iron. This range was comparable to previous culturing observations for species with low heme <em>b</em> content and species growing in low Fe (≤0.50 nmol L<sup>-1</sup>) or nitrate culturing media. Our large scale observations of heme<em> b</em> relative to organic matter suggest the impact of changes in iron supply on phytoplankton iron status.</p>

Detection and characterization of SCVs in the North Atlantic

2020 ◽  
Author(s):  
Ashwita Chouksey ◽  
Xavier Carton ◽  
Jonathan Gula
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Large Scale ◽  
North Atlantic Ocean ◽  
The North ◽  
Place Of Origin ◽  
Different Depths ◽  
The North Atlantic ◽  
Transport And Mixing

<p>In recent years, the oceanographic community has devoted considerable interest to the study of SCVs (Submesoscale Coherent Vortices, i.e. vortices with radii between 2-30 km, below the first internal radius of deformation); indeed, both mesoscale and submesoscale eddies contribute to the transport and mixing of water masses and of tracers (active and passive), affecting the heat transport, the ventilation pathways and thus having an impact on the large scale circulation.</p><p>In different areas of the ocean, SCVs have been detected, via satellite or in-situ measurements, at the surface or at depth. From these data, SCVs were found to be of different shapes and sizes depending on their place of origin and on their location. Here, we will concentrate rather on the SCVs at depth.</p><p>In this study, we use a high resolution simulation of the North Atlantic ocean with the ROMS-CROCO model. In this simulation, we also identify the SCVs at different depths and densities; we analyse their site and mechanism of generation, their drift, the physical processes conducting to this drift and their interactions with the surrounding flows. We also quantify their physical characteristics (radius, thickness, intensity/vorticity, bias in polarity: cyclones versus anticyclones). We provide averages for these characteristics and standard deviations. </p><p>We compare the model results with the observational data, in particular temperature and salinity profiles from Argo floats and velocity data from currentmeter recordings. </p><p>This study is a first step in the understanding of the formation, occurrences and structure of SCVs in the North Atlantic Ocean, of help to improve their in-situ sampling.</p>

scholarly journals Rockhopper penguins and other marine life threatened by driftnet fisheries at Tristan da Cunha

Oryx ◽  
1991 ◽  
Vol 25 (2) ◽  
pp. 76-79 ◽  
Author(s):  
Peter G. Ryan ◽  
John Cooper
Keyword(s):  
Atlantic Ocean ◽  
Large Scale ◽  
Fishing Effort ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
Target Species ◽  
The South ◽  
Tristan Da Cunha ◽  
The Pacific ◽  
The Impact

The oriental driftnet fleet, which is responsible for the large-scale mortality of non-target species in the Pacific Ocean, has extended its range to include the South Atlantic Ocean. Relatively little is known about the areas of operation and impacts of driftnetting in the South Atlantic as yet, but it is emerging that driftnetting is equally devastating to the fauna of this ocean. This paper reviews the impact of the driftnet fishery on non-target species in the central South Atlantic Ocean. Several lines of evidence suggest that fishing effort is focused on Tristan da Cunha, apparently resulting in considerable mortality of rockhopper penguins Eudyptes chrysocome and other marine organisms. Britain should take steps to curb this destructive fishing technique in Tristan waters.

MODELING THE SOUTH ATLANTIC OCEAN FROM MEDIUM TO HIGH RESOLUTION

2014 ◽  
Vol 31 (2) ◽  
Author(s):  
Mariela Gabioux ◽  
Vladimir Santos da Costa ◽  
Joao Marcos Azevedo Correia de Souza ◽  
Bruna Faria de Oliveira ◽  
Afonso De Moraes Paiva
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Large Scale ◽  
South Atlantic ◽  
Surface Relaxation ◽  
The South ◽  
Small Surface ◽  
Basic Model ◽  
Basic Set ◽  
Set Up

Results of the basic model configuration of the REMO project, a Brazilian approach towards operational oceanography, are discussed. This configuration consists basically of a high-resolution eddy-resolving, 1/12 degree model for the Metarea V, nested in a medium-resolution eddy-permitting, 1/4 degree model of the Atlantic Ocean. These simulations performed with HYCOM model, aim for: a) creating a basic set-up for implementation of assimilation techniques leading to ocean prediction; b) the development of hydrodynamics bases for environmental studies; c) providing boundary conditions for regional domains with increased resolution. The 1/4 degree simulation was able to simulate realistic equatorial and south Atlantic large scale circulation, both the wind-driven and the thermohaline components. The high resolution simulation was able to generate mesoscale and represent well the variability pattern within the Metarea V domain. The BC mean transport values were well represented in the southwestern region (between Vitória-Trinidade sea mount and 29S), in contrast to higher latitudes (higher than 30S) where it was slightly underestimated. Important issues for the simulation of the South Atlantic with high resolution are discussed, like the ideal place for boundaries, improvements in the bathymetric representation and the control of bias SST, by the introducing of a small surface relaxation. In order to make a preliminary assessment of the model behavior when submitted to data assimilation, the Cooper & Haines (1996) method was used to extrapolate SSH anomalies fields to deeper layers every 7 days, with encouraging results.

scholarly journals Metal contents of phytoplankton and labile particulate material in the North Atlantic Ocean

2015 ◽  
Vol 137 ◽  
pp. 261-283 ◽  
Author(s):  
Benjamin S. Twining ◽  
Sara Rauschenberg ◽  
Peter L. Morton ◽  
Stefan Vogt
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Particulate Material ◽  
The North ◽  
Metal Contents ◽  
The North Atlantic

Study on Deformation and Damage of Rock Mass Subject to High In Situ Stress by Using a Elastoplastic Damage Model and Considering the Impact of Weak Planes

2013 ◽  
Vol 838-841 ◽  
pp. 705-709
Author(s):  
Yun Hao Yang ◽  
Ren Kun Wang
Keyword(s):  
Rock Mass ◽  
Large Scale ◽  
Damage Model ◽  
Back Analysis ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
High In Situ Stress ◽  
Underground Caverns ◽  
The Impact

Large scale underground caverns are under construction in high in-situ stress field at Houziyan hydropower station. To investigate deformation and damage of surrounding rock mass, a elastoplastic orthotropic damage model capable of describing induced orthotropic damage and post-peak behavior of hard rock is used, together with a effective approach accounting for the presence of weak planes. Then a displacement based back analysis was conducted by using the measured deformation data from extensometers. The computed displacements are in good agreement with the measured ones at most of measurement points, which confirm the validities of constitutive model and numerical simulation model. The result of simulation shows that damage of surrounding rock mass is mainly dominated by the high in-situ stress rather than the weak planes and heavy damage occur at the cavern shoulders and side walls.

The impact of mesoscale eddies on the phytoplankton community in the South Atlantic Ocean: HPLC-CHEMTAX approach

2019 ◽  
Vol 144 ◽  
pp. 154-165 ◽  
Author(s):  
Andréa da Consolação de Oliveira Carvalho ◽  
Carlos Rafael B. Mendes ◽  
Rodrigo Kerr ◽  
José Luiz Lima de Azevedo ◽  
Felippe Galdino ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Phytoplankton Community ◽  
Mesoscale Eddies ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
The South ◽  
The Impact

Long-term ventilation changes of Subpolar Mode Waters in the North Atlantic Ocean and its impact on the oxygen distribution

2021 ◽  
Author(s):  
Ilaria Stendardo ◽  
Bruno Buongiorno Nardelli ◽  
Sara Durante
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Horizontal Resolution ◽  
Late Winter ◽  
Mode Water ◽  
Mode Waters ◽  
The North ◽  
The North Atlantic ◽  
The Impact

<p>In the subpolar North Atlantic Ocean, Subpolar Mode Waters (SPMWs) are formed during late winter convection following the cyclonic circulation of the subpolar gyre. SPMWs participate in the upper flow of the Atlantic overturning circulation (AMOC) and provide much of the water that is eventually transformed into several components of the North Atlantic deep water (NADW), the cold, deep part of the AMOC. In a warming climate, an increase in upper ocean stratification is expected to lead to a reduced ventilation and a loss of oxygen. Thus, understanding how mode waters are affected by ventilation changes will help us to better understand the variability in the AMOC. In particular, we would like to address how the volume occupied by SPMWs has varied over the last decades due to ventilation changes, and what are the aspects driving the subpolar mode water formation, their interannual variations as well as the impact of the variability in the mixing and subduction and vertical dynamics on ocean deoxygenation. For this purpose, we use two observation-based 3D products from Copernicus Marine Service (CMEMS), the ARMOR3D and the OMEGA3D datasets. The first consists of 3D temperature and salinity fields, from the surface to 1500 m depth, available weekly over a regular grid at 1/4° horizontal resolution from 1993 to present. The second consists of observation-based quasi-geostrophic vertical and horizontal ocean currents with the same temporal and spatial resolution as ARMOR3D.</p>

scholarly journals Investigating the impact of Lake Agassiz drainage routes on the 8.2 ka cold event with a climate model

2009 ◽  
Vol 5 (3) ◽  
pp. 471-480 ◽  
Author(s):  
Y.-X. Li ◽  
H. Renssen ◽  
A. P. Wiersma ◽  
T. E. Törnqvist
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Climate Model ◽  
North Atlantic Ocean ◽  
Sensitivity Study ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Cold Event ◽  
The North ◽  
The Impact

Abstract. The 8.2 ka event is the most prominent abrupt climate change in the Holocene and is often believed to result from catastrophic drainage of proglacial lakes Agassiz and Ojibway (LAO) that routed through the Hudson Bay and the Labrador Sea into the North Atlantic Ocean, and perturbed Atlantic meridional overturning circulation (MOC). One key assumption of this triggering mechanism is that the LAO freshwater drainage was dispersed over the Labrador Sea. Recent data, however, show no evidence of lowered δ18O values, indicative of low salinity, from the open Labrador Sea around 8.2 ka. Instead, negative δ18O anomalies are found close to the east coast of North America, extending as far south as Cape Hatteras, North Carolina, suggesting that the freshwater drainage may have been confined to a long stretch of continental shelf before fully mixing with North Atlantic Ocean water. Here we conduct a sensitivity study that examines the effects of a southerly drainage route on the 8.2 ka event with the ECBilt-CLIO-VECODE model. Hosing experiments of four routing scenarios, where freshwater was introduced to the Labrador Sea in the northerly route and to three different locations along the southerly route, were performed to investigate the routing effects on model responses. The modeling results show that a southerly drainage route is possible but generally yields reduced climatic consequences in comparison to those of a northerly route. This finding implies that more freshwater would be required for a southerly route than for a northerly route to produce the same climate anomaly. The implicated large amount of LAO drainage for a southerly routing scenario is in line with a recent geophysical modelling study of gravitational effects on sea-level change associated with the 8.2 ka event, which suggests that the volume of drainage might be larger than previously estimated.

scholarly journals What Is the Impact of Additional Tropical Observations on a Modern Data Assimilation System?

2019 ◽  
Vol 147 (7) ◽  
pp. 2433-2449
Author(s):  
Laura C. Slivinski ◽  
Gilbert P. Compo ◽  
Jeffrey S. Whitaker ◽  
Prashant D. Sardeshmukh ◽  
Jih-Wang A. Wang ◽  
...  
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Mean Square ◽  
Observational Network ◽  
In Situ Observations ◽  
The Mean ◽  
The Impact ◽  
Assimilation System

Abstract Given the network of satellite and aircraft observations around the globe, do additional in situ observations impact analyses within a global forecast system? Despite the dense observational network at many levels in the tropical troposphere, assimilating additional sounding observations taken in the eastern tropical Pacific Ocean during the 2016 El Niño Rapid Response (ENRR) locally improves wind, temperature, and humidity 6-h forecasts using a modern assimilation system. Fields from a 50-km reanalysis that assimilates all available observations, including those taken during the ENRR, are compared with those from an otherwise-identical reanalysis that denies all ENRR observations. These observations reveal a bias in the 200-hPa divergence of the assimilating model during a strong El Niño. While the existing observational network partially corrects this bias, the ENRR observations provide a stronger mean correction in the analysis. Significant improvements in the mean-square fit of the first-guess fields to the assimilated ENRR observations demonstrate that they are valuable within the existing network. The effects of the ENRR observations are pronounced in levels of the troposphere that are sparsely observed, particularly 500–800 hPa. Assimilating ENRR observations has mixed effects on the mean-square difference with nearby non-ENRR observations. Using a similar system but with a higher-resolution forecast model yields comparable results to the lower-resolution system. These findings imply a limited improvement in large-scale forecast variability from additional in situ observations, but significant improvements in local 6-h forecasts.

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