Seasonal changes in POC export flux in the Chukchi Sea and implications for water column-benthic coupling in Arctic shelves

2005 ◽  
Vol 52 (24-26) ◽  
pp. 3427-3451 ◽  
Author(s):  
S.B. Moran ◽  
R.P. Kelly ◽  
K. Hagstrom ◽  
J.N. Smith ◽  
J.M. Grebmeier ◽  
...  
Keyword(s):  
Water Column ◽  
Seasonal Changes ◽  
Chukchi Sea ◽  
Export Flux ◽  
Poc Export ◽  
Poc Export Flux ◽  
Benthic Coupling

scholarly journals Why productive upwelling areas are often sources rather than sinks of CO<sub>2</sub>? – a comparative study on eddy upwellings in the South China Sea

2013 ◽  
Vol 10 (8) ◽  
pp. 13399-13426
Author(s):  
N. Jiao ◽  
Y. Zhang ◽  
K. Zhou ◽  
Q. Li ◽  
M. Dai ◽  
...  
Keyword(s):  
Organic Carbon ◽  
South China Sea ◽  
South China ◽  
Biological Activities ◽  
Critical Role ◽  
Microbial Activities ◽  
Export Flux ◽  
China Sea ◽  
Poc Export ◽  
Poc Export Flux

Abstract. Marine upwelling regions are known to be productive in carbon fixation and thus thought to be sinks of CO2, whereas many upwelling areas in the ocean are actually sources rather than sinks of CO2. To address this paradox, multiple biogeochemical parameters were investigated at two cyclonic-eddy-induced upwelling sites CE1 and CE2 in the western South China Sea. The results showed that upwelling can exert significant influences on biological activities in the euphotic zone and can either increase or decrease particulate organic carbon (POC) export flux depending on upwelling conditions such as the magnitude, timing, and duration of nutrient input and consequent microbial activities. At CE2 the increase of phytoplankton biomass caused by the upwelled nutrients resulted in increase of POC export flux compared to non-eddy reference sites, while at CE1 the microbial respiration of organic carbon stimulated by the upwelled nutrients significantly contributed to the attenuation of POC export flux, aggravating outgassing of CO2. These results suggest that on top of upwelled dissolved inorganic carbon release, microbial activities stimulated by upwelled nutrients and phytoplankton labile organic carbon can play a critical role for a marine upwelling area to be a source rather than a sink of CO2. Meanwhile, we point out that even though an upwelling region is outgassing, carbon sequestration still takes place through the POC-based biological pump as well as the refractory dissolved organic carbon (RDOC)-based microbial carbon pump.

scholarly journals Revisiting the CO<sub>2</sub> "source" problem in upwelling areas – a comparative study on eddy upwellings in the South China Sea

2014 ◽  
Vol 11 (9) ◽  
pp. 2465-2475 ◽  
Author(s):  
N. Jiao ◽  
Y. Zhang ◽  
K. Zhou ◽  
Q. Li ◽  
M. Dai ◽  
...  
Keyword(s):  
Organic Carbon ◽  
South China Sea ◽  
South China ◽  
Biological Activities ◽  
Critical Role ◽  
Microbial Activities ◽  
Export Flux ◽  
China Sea ◽  
Poc Export ◽  
Poc Export Flux

Abstract. The causes for a productive upwelling region to be a source of CO2 are usually referred to the excess CO2 supplied via upwelling of high dissolved inorganic carbon (DIC) from deep water. Furthermore, we hypothesize that microbial activity plays a significant role on top of that. To test this hypothesis, multiple biogeochemical parameters were investigated at two cyclonic-eddy-induced upwelling sites, CE1 and CE2, in the western South China Sea. The data showed that upwelling can exert significant influences on biological activities in the euphotic zone and can also impact on particulate organic carbon (POC) export flux depending on upwelling conditions, such as the magnitude, timing, and duration of nutrient input and consequent microbial activities. At CE2, the increase of phytoplankton biomass caused by the upwelled nutrients resulted in increase of POC export flux compared to non-eddy reference sites, while at CE1 the microbial respiration of organic carbon stimulated by the upwelled nutrients significantly contributed to the attenuation of POC export flux. These results suggest that on top of upwelled DIC, microbial activities stimulated by upwelled nutrients and labile organic carbon produced by phytoplankton can play a critical role for an upwelling area to be outgassing or uptaking CO2. We point out that even though an upwelling region is outgassing CO2, carbon sequestration still takes place through the POC-based biological pump as well as the refractory dissolved organic carbon (RDOC)-based microbial carbon pump.

Studies of the hydrobiology of a tropical lake in north-western Queensland. II. Seasonal changes in thermal and dissolved oxygen characteristics

1980 ◽  
Vol 31 (5) ◽  
pp. 589 ◽  
Author(s):  
CM Finlayson ◽  
TP Farrell ◽  
DJ Griffiths
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Environmental Conditions ◽  
Seasonal Changes ◽  
Thermal Stratification ◽  
Oxygen Depletion ◽  
Tropical Lake ◽  
North Western

The stratification characteristics of Lake Moondarra (24�34'S.,139�35'E.), a man-made lake in north- western Queensland, have been studied. Evidence is presented that the lake approximates the warm polymictic type in which no persistent thermal stratification ever develops. During the cooler months, thermal stratification breaks down during the night; in the warmer months, the intense rainstorms prevent the establishment of a persistently stratified water column. The shallowness of the lake relative to its surface areaand the prevailing environmental conditions ensure that extensive periods of oxygen depletion do not develop in the water column. It is concluded that a strong and prolonged period of thermal stratification, with subsequent serious effects of the availability of dissolved oxygen in the deeper layers, would only arise if, in a particular year. there were no significant rainstorms.

scholarly journals The export flux of particulate organic carbon derived from <sup>210</sup>Po∕<sup>210</sup>Pb disequilibria along the North Atlantic GEOTRACES GA01 transect: GEOVIDE cruise

2019 ◽  
Vol 16 (2) ◽  
pp. 309-327 ◽  
Author(s):  
Yi Tang ◽  
Nolwenn Lemaitre ◽  
Maxi Castrillejo ◽  
Montserrat Roca-Martí ◽  
Pere Masqué ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
North Atlantic ◽  
Study Region ◽  
Vertical Advection ◽  
Export Flux ◽  
The North ◽  
Iberian Basin ◽  
Poc Export ◽  
The North Atlantic

Abstract. The disequilibrium between 210Po activity and 210Pb activity in seawater samples was determined along the GEOTRACES GA01 transect in the North Atlantic during the GEOVIDE cruise (May–June 2014). A steady-state model was used to quantify vertical export of particulate 210Po. Vertical advection was incorporated into one version of the model using time-averaged vertical velocity, which had substantial variance. This resulted in large uncertainties for the 210Po export flux in this model, suggesting that those calculations of 210Po export fluxes should be used with great care. Despite the large uncertainties, there is no question that the deficits of 210Po in the Iberian Basin and at the Greenland Shelf have been strongly affected by vertical advection. Using the export flux of 210Po and the particulate organic carbon (POC) to 210Po ratio of total (> 1 µm) particles, we determined the POC export fluxes along the transect. Both the magnitude and efficiency of the estimated POC export flux from the surface ocean varied spatially within our study region. Export fluxes of POC ranged from negligible to 10 mmol C m−2 d−1, with enhanced POC export in the Labrador Sea. The cruise track was characterized by overall low POC export relative to net primary production (export efficiency < 1 %–15 %), but relatively high export efficiencies were seen in the basins where diatoms dominated the phytoplankton community. The particularly low export efficiencies in the Iberian Basin, on the other hand, were explained by the dominance of smaller phytoplankton, such as cyanobacteria or coccolithophores. POC fluxes estimated from the 210Po∕210Pb and 234Th∕238U disequilibria agreed within a factor of 3 along the transect, with higher POC estimates generally derived from 234Th. The differences were attributed to integration timescales and the history of bloom events.

Vertical distribution of pelagial zooplankton in a middle-sized dimictic valley reservoir

Biologia ◽  
2006 ◽  
Vol 61 (2) ◽  
Author(s):  
Martina Hudcovicová ◽  
Marian Vranovsky
Keyword(s):  
Vertical Distribution ◽  
Water Column ◽  
Seasonal Changes ◽  
Thermal Gradient ◽  
Summer Temperature ◽  
Zooplankton Abundance ◽  
Invertebrate Predation ◽  
Chaoborus Flavicans ◽  
Daphnia Cucullata ◽  
The Vertical Distribution

AbstractOur observations indicate the vertical distribution of zooplankton and its seasonal changes in Dubník II reservoir (Slovakia) are determined mainly by the thermal regime of the reservoir, by transparency, and by fish and invertebrate predation. During periods of circulation, zooplankton vertical distribution in the whole water column was more homogeneous, whilst during summer temperature stratification zooplankton concentrated in the epilimnion — rotifers in higher layers than crustaceans. During summer stagnation a steep thermal gradient occurred at the boundary of the epi-and hypolimnion and low temperature and low dissolved oxygen in hypolimnion offered a refuge for Chaoborus flavicans larvae against fish, enabling coexistence of vertebrate and invertebrate predation. This evidence supports our previous findings concerning dominance of rotifers in zooplankton and representation of crustaceans by small-bodied species in the study reservoir. Steep thermal gradient and the presence of Chaoborus larvae caused very low zooplankton abundance in the lower part of the water column and a reduction of cladocerans refuges against fish to layers of thermocline or closely under thermocline where Daphnia cucullata and Daphnia parvula were found. Our previous assumptions about the high density of zooplanktivorous fish in Dubník II reservoir are supported by the fact that these small cladocerans are represented by smaller individuals in the upper layers and bigger individuals in deeper layers.

scholarly journals Insignificant enhancement of export flux in the highly productive Subtropical Front, east of New Zealand: a high resolution study of particle export fluxes based on <sup>234</sup>Th:<sup>238</sup>U disequilibria

2011 ◽  
Vol 8 (5) ◽  
pp. 9535-9576
Author(s):  
K. Zhou ◽  
S. D. Nodder ◽  
M. Dai ◽  
J. A. Hall
Keyword(s):  
New Zealand ◽  
Salinity Gradient ◽  
Salinity Range ◽  
Water Type ◽  
Export Flux ◽  
Low Salinity ◽  
Iron Fertilization ◽  
Natural Iron ◽  
Poc Export ◽  
Particle Export

Abstract. We evaluated the downward Particulate Organic Carbon (POC) export fluxes in the Subtropical Frontal zone (STF) of the Southern Ocean. The site is characterized by enhanced primary productivity which has been suggested to be stimulated through so-called natural iron fertilization processes at its northern boundary where iron-depleted subantarctic water (SAW) mixes with oligotrophic, iron-replete subtropical water (STW). We adopted the small-volume 234Th method to achieve highest spatial sampling resolution as possible based on a cruise to the STF to the east New Zealand in austral late autumn-early winter, May–June 2008. The inventories of fluorescence, particulate 234Th and POC observed in the upper 100 m were all elevated in the mid-salinity part of the water type (34.5<S<34.8), compared with low (S<34.5) and high (S>34.8) salinity waters. However, Steady-State 234Th fluxes were similar cross all of the salinity gradient being 1484 in the mid-salinity, and 1761 and 1304 dpm m−2 d−1 in the high and low salinity zones respectively. Bottle POC/Th ratios at the depth of 100 m were used to convert the Th fluxes into POC export flux. The POC flux was again not enhanced in the mid-salinity range where the primary production was highest, being 7.4 mmol C m−2 d−1 as compared to 9.9 mmol C m−2 d−1 in high salinity waters, and 5.9 mmol C m−2 d−1 in low salinity waters. This study implied that natural iron fertilization does not necessarily lead to the enhancement of POC export in STF regions.

scholarly journals Chemical fate and settling of mineral dust in surface seawater after atmospheric deposition observed from dust seeding experiments in large mesocosms

2014 ◽  
Vol 11 (19) ◽  
pp. 5581-5594 ◽  
Author(s):  
K. Desboeufs ◽  
N. Leblond ◽  
T. Wagener ◽  
E. Bon Nguyen ◽  
C. Guieu
Keyword(s):  
Water Column ◽  
Elemental Composition ◽  
Chemical Elements ◽  
Sediment Traps ◽  
Dust Particles ◽  
Dust Deposition ◽  
Chl A ◽  
Poc Export ◽  
Nw Mediterranean ◽  
Good Productivity

Abstract. We report here the elemental composition of sinking particles in sediment traps and in the water column following four artificial dust seeding experiments (each representing a flux of 10 g m−2). Dry or wet dust deposition were simulated during two large mesocosms field campaigns that took place in the coastal water of Corsica (NW Mediterranean Sea) representative of oligotrophic conditions. The dust additions were carried out with fresh or artificially aged dust (i.e., enriched in nitrate and sulfate by mimicking cloud processing) for various biogeochemical conditions, enabling us to test the effect of these parameters on the chemical composition and settling of dust after deposition. The rates and mechanisms of total mass, particulate organic carbon (POC) and chemical elements (Al, Ba, Ca, Co, Cu, Fe, K, Li, Mg, Mn, Mo, N, Nd, P, S, Sr and Ti) transfer from the mesocosm surface to the sediment traps installed at the base of the mesocosms after dust deposition show that (1) 15% of the initial dust mass was dissolved in the water column in the first 24 h after seeding. Except for Ca, S and N, the elemental composition of dust particles was constant during their settling, showing the relevance of using interelemental ratios, such as Ti/Al as proxy of lithogenic fluxes. (2) Whatever the type of seeding (using fresh dust to simulate dry deposition or artificially aged dust to simulate wet deposition), the particulate phase both in the water column and in the sediment traps was dominated by dust particles. (3) Due to the high Ba content in dust, Ba/Al cannot be used as productivity proxy in the case of high dust input in the sediment traps. Instead, our data suggests that the ratio Co/Al could be a good productivity proxy in this case. (4) After 7 days, between 30 and 68% of added dust was still in suspension in the mesocosms. This difference in the dust settling was directly associated with a difference in POC export, since POC fluxes were highly correlated to dust lithogenic fluxes signifying a ballast effect of dust. The highest fraction of remaining dust in suspension in the mesocosm at the end of the experiment was found inversely correlated to Chl a increase. This suggests that the fertilizing effect of dust on autotrophs organisms, the ballast effect, and POC fluxes are strongly correlated. (5) Our data emphasize a typical mass ratio Lithogenic/POC fluxes around 30 which could be used as reference to estimate the POC export triggered by wet dust deposition event.

A perfect bowl-like submesoscale vortex from seismic reflection transect in the Chukchi Sea, Arctic Ocean

2021 ◽  
Author(s):  
Shun Yang ◽  
Haibin Song ◽  
Kun Zhang
Keyword(s):  
Arctic Ocean ◽  
Water Column ◽  
Chukchi Sea ◽  
The Arctic ◽  
Global Ocean ◽  
Physical Oceanography ◽  
Depth Range ◽  
Seismic Line ◽  
The Arctic Ocean ◽  
The Right

&lt;p&gt;The eddies are ubiquitous in the ocean and play an important role in the transportation and redistribution of heat, salt, carbon, nutrients and other materials in the global ocean, thus can regulate global climate and affect the distribution of marine organism. Compared with mesoscale eddies, submesoscale vortices (SVs) have smaller spatial and temporal scales, which impose higher requirements on observation and simulation. The oceanic SVs have a strong vertical velocity, which provides an important supply of nutrients in the upper ocean.&lt;/p&gt;&lt;p&gt;Many researchers have studied the SVs in the Arctic Ocean by physical oceanography methods (e.g., &lt;em&gt;in-situ &lt;/em&gt;measurements and satellite observations). Here, we found a perfect bowl-like SV using a new method named seismic oceanography (SO). SO can use multichannel seismic (MCS) reflection data to produce surprisingly detailed images of water column. Compared with the traditional physical oceanography methods, SO has the advantages of high acquisition efficiency, high lateral resolution (~10 m) and full depth imaging of seawater.&lt;/p&gt;&lt;p&gt;We used MCS data to image the water column in the in autumn Northeast Chukchi Sea, and captured a perfect bowl-like structure with a depth range of ~200-620m. The structure is almost bilaterally symmetric and has dip angles of 4.8&amp;#176; and 5.5&amp;#176; on the left and on the right, respectively. And it has a horizontal scale of about 12 km at the top and 4.5 km at the bottom, and both the top and bottom of it are near horizontal. The reflections are almost blank in its interior, but are intense and very narrow (~30 m thick) at the lateral boundaries. This indicated that the interior water is homogeneous and quite different from that around it. Fortunately, there is an XBT station near the seismic line and collected almost simultaneously (only one day apart) with the seismic line. The XBT station shows obvious high temperature anomaly over 2&amp;#176;C at the depth of 210-700 m. Therefore, we concluded the structure is a subsurface warm SV, i.e. anticyclonic warm eddy, and may be a submesoscale coherent vortex (SCV). The anomalies from the surrounding water masses indicate that the SV was created at the edge of the Arctic Ocean and then advected here.&lt;/p&gt;&lt;p&gt;In addition, we used Rossby number (Ro) and Okubo-Weiss (OW) parameter calculated from daily-averaged re-analysis hydrographic data (~3.5 km of grid spacing at 75&amp;#176;N ) from Copernicus Marine Environment Monitoring Service (CMEMS) to analyze the SV. Result shows that the values of the Ro and OW parameter in the area of the SV are both negative. This also suggests that this SV is an anticyclone. This submesoscale anticyclonic vortex may be generated from the friction effect between the warm inflow from the North Pacific and the right wall of Barrow Canyon after passing through the Bering Strait, and then transported to the Northeast of Chukchi Sea by the Beaufort Gyre.&lt;/p&gt;

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