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.

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

2015 ◽  
Vol 12 (13) ◽  
pp. 11019-11059
Author(s):  
R. Steinfeldt ◽  
J. Sültenfuß ◽  
M. Dengler ◽  
T. Fischer ◽  
M. Rhein
Keyword(s):  
Mixed Layer ◽  
Coastal Upwelling ◽  
Ekman Transport ◽  
Helium Isotope ◽  
Net Community Production ◽  
Mean Values ◽  
Direct Observations ◽  
Vertical Diffusivity ◽  
Order Of Magnitude ◽  
Oceanic Upwelling

Abstract. Oceanic upwelling velocities are too small to be measured directly. The surface disequilibrium of the 3He/4He ratio provides an indirect method to infer vertical velocities at the base of the mixed layer. Samples of helium isotopes were taken from two coastal upwelling regions, off Peru on cruise M91, and off Mauritania on 3 cruises. The helium-3 flux into the mixed layer also depends on the diapycnal mixing. Direct observations of the vertical diffusivity have been performed on all 4 cruises and are also used in this study. The resulting upwelling velocities in the coastal regions vary between 1.1 × 10−5 and 2.8 × 10−5 m s−1 for all cruises. Vertical velocities off the equator can also be inferred from the divergence of the wind driven Ekman transport. In the coastal regimes, the agreement between wind and helium derived upwelling is fairly good at least for the mean values. Further offshore, the helium derived upwelling still reaches 1 × 10−5 m s−1, whereas the wind driven upwelling from Ekman suction is smaller by at least one order of magnitude. One reason for this difference might be eddy induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium derived vertical velocities and the measured vertical diffusivities. The advective part of these fluxes makes up at least 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 g C m2 d−1 off Peru and 1.6–1.9 g C m2 d−1 off Mauritania.

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.

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

<p>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 "monsoon-desert mechanism" 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.</p>

scholarly journals Effects of the Pacific Diapycnal Mixing and Wind Stress on the Global and Pacific Meridional Overturning Circulation*

2005 ◽  
Vol 35 (10) ◽  
pp. 1876-1890 ◽  
Author(s):  
Ryo Furue ◽  
Masahiro Endoh
Keyword(s):  
Wind Stress ◽  
North Atlantic ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Overturning Circulation ◽  
The North ◽  
Vertical Diffusivity ◽  
The Pacific ◽  
Meridional Overturning ◽  
The Pacific Ocean

Abstract Numerical experiments are conducted using an idealized basin to investigate roles of the deep vertical diffusivity and wind stress of the Pacific Ocean in the global and Pacific meridional overturning circulation. The Pacific middepth diffusivity is found to be enhancing the global meridional overturning circulation; when this part of diffusivity is reduced to the background value, not only is the layered circulation of the Pacific greatly weakened, but also the production of the North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) is significantly reduced. The deeper part of the Pacific diffusivity is found to be enhancing the production of the AABW in the model. When the wind stress is turned off in the Pacific, the deep meridional overturning circulation of the Pacific is reduced and the production of the NADW and AABW is also significantly reduced. This is likely due to the reduction of the wind-enhanced upwelling in the subpolar and equatorial regions. These results suggest the importance of the diapycnal diffusion and sea surface conditions in the Pacific not only to the circulation within the Pacific but also to the global meridional overturning circulation.

scholarly journals Mechanisms of stabilization of modern climate

2019 ◽  
Vol 62 (6) ◽  
pp. 750-755
Author(s):  
S. A. Lysenko ◽  
V. F. Loginov ◽  
S. L. Oshepkov
Keyword(s):  
Water Vapor ◽  
Surface Wind ◽  
Ground Surface ◽  
Total Content ◽  
Radiative Heating ◽  
Tropical Region ◽  
Radiation Balance ◽  
The Pacific ◽  
Order Of Magnitude ◽  
The Pacific Ocean

This article investigates the causes and mechanism of change in the climatic pause from 1998 to 2014. In particular, based on the satellite data and the meteorological reanalysis we found a relationship between the temperature of the tropical region of the Pacific Ocean, the speed of the surface wind, and the total content of water vapor in the atmosphere. We also showed that the climatic pause can be explained by a decrease in the water vapor content in the atmosphere and evaluated how this decrease affected the radiation balance of the ground surface. The observed dynamics of water vapor is shown to lead to a decrease in the incoming part of the radiation balance of the ground surface by an amount, which is more than one order of magnitude larger than that caused by the increase in anthropogenic carbon dioxide. It was demonstrated that a decrease in the cloud cover optical thickness could also lead to the stabilization of the global temperature by means of radiative heating of the underlying surface. 

scholarly journals Radiological consequences and lessons of the Chernobyl NPP and «Fukushima-1» NPP radiation accidents

2021 ◽  
Vol 14 (1) ◽  
pp. 6-16
Author(s):  
G. G. Onischenko ◽  
A. Yu. Popova ◽  
I. K. Romanovich
Keyword(s):  
Russian Federation ◽  
Large Scale ◽  
Exposure Period ◽  
The Pacific ◽  
Emergency Workers ◽  
Chernobyl Npp ◽  
Order Of Magnitude ◽  
Radiation Induced ◽  
The Pacific Ocean ◽  
Former Ussr

35 years have passed since the Chernobyl NPP accident, 10 years – since the «Fukushima-1» NPP accident. At the present time extensive activities on the remediation of the consequences of two major large-scale radiation disasters are performed in the Belorussia, Russian Federation, Ukraine, and Japan. Releases of radiologically significant radionuclides after the Chernobyl NPP accident correspond to 14 exaBecquerel – higher up to an order of magnitude compared to 3 emergence power units of the «Fukushima-1» NPP. The significantly lower release rate and deposition of 80% of the radionuclides released into the atmosphere on the surface of the Pacific Ocean lead to lower up to several orders of magnitude radioactive contamination of the Japanese territory compared to the territories of the former USSR and neighboring countries after the Chernobyl NPP accident. Collective dose to the public due to the Chernobyl NPP accident is higher up to several orders of magnitude compared to the dose to the Japanese population after the «Fukushima-1» accident. No statistically reliable long-term medical consequences are expected for all groups of the Japanese public, additionally exposed due to «Fukushima-1» accident. 134 emergency workers have developed acute radiation sickness due to the Chernobyl NPP accident. Emergency workers with doses higher than 150 mSv had increased radiation-induced morbidity with leukemia and solid cancers. Among the individuals, that were kids or adolescents in the exposure period after the Chernobyl NPP accident and residing on the territories of Belorussia, Ukraine and four most radioactively contaminated regions of the Russian Federation, morbidity with thyroid cancer is increase by a factor of 10 compared to the pre-accidental levels. The following lessons of the Chernobyl NPP and «Fukushima-1» NPP can be derived: faults in the NPP design and lack of response after the recognition of the faults; lack of timely full-scale prophylactic with iodine; unjustified resettlement of the residents of the radioactively contaminated territories several years after the accident.

On the Pacific Ocean regime shift

2001 ◽  
Vol 28 (19) ◽  
pp. 3721-3724
Author(s):  
Cathy Stephens
Keyword(s):  
Pacific Ocean ◽  
Regime Shift ◽  
The Pacific ◽  
The Pacific Ocean
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