scholarly journals Particle-associated dissolved elemental fluxes: revising the stochiometry of mixed layer export

2005 ◽  
Vol 2 (2) ◽  
pp. 275-302 ◽  
Author(s):  
A. N. Antia
Keyword(s):  
Mixed Layer ◽  
Euphotic Zone ◽  
Sediment Traps ◽  
Total Flux ◽  
Carbon Export ◽  
Redfield Ratio ◽  
Dissolved Carbon ◽  
Carbon And Nitrogen ◽  
The North ◽  
Winter Mixed Layer

Abstract. Sinking particles carry substantial loads of dissolved elements in their interstitial spaces that contribute to the vertical transport of elements out of the euphotic zone. Elemental fluxes as traditionally measured by sediment traps underestimate total export when this particle-associated dissolved flux is not considered. The errors introduced are variable and alter both the absolute levels of flux as well as the stochiometry of export. Using samples from sediment traps in the North Atlantic and measuring excess dissolved carbon, nitrogen, phosphorus, silica and calcium in the supernatant of the collection cups, it is possible to quantitatively assess the total flux in the sample. At the base of the winter mixed layer, up to 90±6% of phosphorus fluxes are found as excess phosphate whereas for carbon and nitrogen dissolved concentrations account for between 30% and 47% of total fluxes respectively. Particle-associated dissolved silica fluxes are a mean of 61% of total flux. Little (<10%) of calcium fluxes are in dissolved form. The proportion of dissolved to total flux decreases with trap deployment depth. Calculations of the C:N:P ratios for particles only are well above the Redfield Ratio of 106:16:1 (Redfield et al., 1964), although the mid-water dissolved N:P and N:Si values as well as the C:N:P ratios of remineralisation along isopycnals conform to the Redfield Ratio at this site. Accounting for dissolved fluxes of all these elements brings the estimates in agreement with the Redfield Ratio and with other geochemical estimates of the stochiometry of winter mixed layer export. A factor of 3 to 4 higher ratios of organic: inorganic carbon export also implies that the net atmospheric CO2 sequestration by the biological pump is about 50% higher at this site when the particle-associated dissolved elemental fluxes are considered.

scholarly journals Solubilization of particles in sediment traps: revising the stoichiometry of mixed layer export

2005 ◽  
Vol 2 (2) ◽  
pp. 189-204 ◽  
Author(s):  
A. N. Antia
Keyword(s):  
Mixed Layer ◽  
Surrounding Medium ◽  
Sediment Traps ◽  
Carbon Export ◽  
Dissolved Carbon ◽  
Carbon And Nitrogen ◽  
The North ◽  
Vertical Fluxes ◽  
Winter Mixed Layer ◽  
Redfield Ratios

Abstract. Sinking particles, once caught in sediment trap jars, release dissolved elements into the surrounding medium through leaching from their pore fluids, chemical dissolution and the activity of free exoenzymes. This results in an increase in dissolved elements in the trap jar supernatant. Elemental fluxes as traditionally measured by sediment traps underestimate total export when this particle-associated dissolved flux is not considered. The errors introduced are variable and alter both the absolute levels of flux as well as the stoichiometry of export. These errors have been quantified and corrections applied for samples from sediment traps in the North Atlantic based on measurements of excess dissolved carbon, nitrogen, phosphorus, silica and calcium in the supernatant of the collection cups. At the base of the winter mixed layer, on average 90±6% of phosphorus fluxes are found as excess phosphate whereas for carbon and nitrogen dissolved concentrations account for 30 (±8)% and 47(±11)% of total fluxes respectively. Excess dissolved silica is on average 61 (±17)% of total biogenic silica flux. Little (<10%) of calcium is solubilized. The proportion of dissolved to total flux decreases with trap deployment depth. Calculations of the C:N:P ratios for particles only are well above the Redfield ratios of 106:16:1 (Redfield et al., 1963), although the mid-water dissolved N:P and N:Si values as well as the C:N:P ratios of remineralisation along isopycnals conform to the Redfield ratios at this site. Accounting for dissolved fluxes of all these elements brings the stoichiometry of export in agreement with the Redfield Ratio and with other geochemical estimates of winter mixed layer export. A factor of 3 to 4 higher ratios of organic: inorganic carbon export also implies that the net atmospheric CO2 sequestration by the biological pump is about 50% higher at this site when the dissolved elemental fluxes are considered. Solubilization is thus a process that should be accounted for in protocols used to measure vertical fluxes with sediment traps.

scholarly journals The North Pacific Climatology of Winter Mixed Layer and Mode Waters

2004 ◽  
Vol 34 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Toshio Suga ◽  
Kazunori Motoki ◽  
Yoshikazu Aoki ◽  
Alison M. Macdonald
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
Mode Waters ◽  
The North ◽  
Winter Mixed Layer ◽  
The North Pacific

scholarly journals Vertically migrating phytoplankton drive seasonal formation of subsurface negative preformed nitrate anomalies in the subtropical North Pacific and North Atlantic

2018 ◽  
Author(s):  
Robert T. Letscher ◽  
Tracy A. Villareal
Keyword(s):  
Organic Matter ◽  
Mixed Layer ◽  
North Atlantic ◽  
North Pacific ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Euphotic Zone ◽  
The North ◽  
Station Aloha ◽  
Biological Nitrogen

Abstract. Summertime drawdown of dissolved inorganic carbon in the absence of measurable nutrients from the mixed layer and subsurface negative preformed nitrate (preNO3) anomalies observed for the ocean's subtropical gyres are two biogeochemical phenomena that have thus far eluded complete description. Many processes are thought to contribute including biological nitrogen fixation, lateral nutrient transport, carbon overconsumption or non-Redfield C : N : P organic matter cycling, heterotrophic nutrient uptake, and the actions of vertically migrating phytoplankton. Here we investigate the seasonal formation rates and potential contributing mechanisms for negative preformed nitrate anomalies (oxygen consumption without stoichiometric nitrate release) in the subsurface and positive preformed nitrate anomalies (oxygen production without stoichiometric nitrate drawdown) in the euphotic zone at the subtropical ocean time series stations ALOHA in the North Pacific and BATS in the North Atlantic. Non-Redfield −O2 : N stoichiometry for dissolved organic matter (DOM) remineralization is found to account for up to ~ 15 mmol N m−2 yr−1 of negative preNO3 anomaly formation at both stations. Residual negative preNO3 anomalies in excess of that which can be accounted for by non-Redfield DOM cycling are found to accumulate at a rate of ~ 32–46 mmol N m−2 yr−1 at station ALOHA and ~ 46–87 mmol N m−2 yr−1 at the BATS station. These negative anomaly formation rates are in approximate balance with positive preNO3 anomaly formation rates from the euphotic zone located immediately above the nutricline in the water column. Cycling of transparent exopolymer particles (TEP) and heterotrophic nitrate uptake can contribute to the formation of these preNO3 anomalies, however a significant fraction, estimated at ~ 50–95 %, is unexplained by the sum of these processes. Vertically migrating phytoplankton possess the necessary nutrient acquisition strategy and biogeochemical signature to quantitatively explain both the residual negative and positive preNO3 anomalies as well as the mixed layer dissolved inorganic carbon drawdown at stations ALOHA and BATS. TEP production by the model Rhizosolenia mat system could provide accelerated vertical transport of TEP as well as link the three processes together. Phytoplankton vertical migrators, although rare and easily overlooked, may play a large role in subtropical ocean nutrient cycling and the biological pump.

scholarly journals Patterns and persistence of hydrologic carbon and nutrient export from collapsing upland permafrost

2015 ◽  
Vol 12 (12) ◽  
pp. 3725-3740 ◽  
Author(s):  
B. W. Abbott ◽  
J. B. Jones ◽  
S. E. Godsey ◽  
J. R. Larouche ◽  
W. B. Bowden
Keyword(s):  
Aquatic Ecosystems ◽  
Inorganic Nitrogen ◽  
The Arctic ◽  
Nutrient Export ◽  
Initial Pulse ◽  
Dissolved Carbon ◽  
Carbon And Nitrogen ◽  
The North ◽  
North Slope Of Alaska ◽  
High Concentrations

Abstract. As high latitudes warm, vast stocks of carbon and nitrogen stored in permafrost will become available for transport to aquatic ecosystems. While there is a growing understanding of the potential effects of permafrost collapse (thermokarst) on aquatic biogeochemical cycles, neither the spatial extent nor temporal duration of these effects is known. To test hypotheses concerning patterns and persistence of elemental export from upland thermokarst, we sampled hydrologic outflow from 83 thermokarst features in various stages of development across the North Slope of Alaska. We hypothesized that an initial pulse of carbon and nutrients would be followed by a period of elemental retention during feature recovery, and that the duration of these stages would depend on feature morphology. Thermokarst caused substantial increases in dissolved organic carbon and other solute concentrations with a particularly large impact on inorganic nitrogen. Magnitude and duration of thermokarst effects on water chemistry differed by feature type and secondarily by landscape age. Most solutes returned to undisturbed concentrations after feature stabilization, but elevated dissolved carbon, inorganic nitrogen, and sulfate concentrations persisted through stabilization for some feature types, suggesting that aquatic disturbance by thermokarst for these solutes is long-lived. Dissolved methane decreased by 90% for most feature types, potentially due to high concentrations of sulfate and inorganic nitrogen. Spatial patterns of carbon and nutrient export from thermokarst suggest that upland thermokarst may be a dominant linkage transferring carbon and nutrients from terrestrial to aquatic ecosystems as the Arctic warms.

scholarly journals C : N : P stoichiometry at the Bermuda Atlantic Time-series Study station in the North Atlantic Ocean

2015 ◽  
Vol 12 (12) ◽  
pp. 9275-9305
Author(s):  
A. Singh ◽  
S. E. Baer ◽  
U. Riebesell ◽  
A. C. Martiny ◽  
M. W. Lomas
Keyword(s):  
Time Series ◽  
Organic Matter ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Euphotic Zone ◽  
Redfield Ratio ◽  
The North ◽  
Elemental Stoichiometry ◽  
Series Study

Abstract. Nitrogen (N) and phosphorus (P) availability determine the strength of the ocean's carbon (C) uptake, and variation in the N : P ratio in inorganic nutrients is key to phytoplankton growth. A similarity between C : N : P ratios in the plankton biomass and deep-water nutrients was observed by Alfred C. Redfield around 80 years ago and suggested that biological processes in the surface ocean controlled deep ocean chemistry. Recent studies have emphasized the role of inorganic N : P ratios in governing biogeochemical processes, particularly the C : N : P ratio in suspended particulate organic matter (POM), with somewhat less attention given to exported POM and dissolved organic matter (DOM). Herein, we extend the discussion on ecosystem C : N : P stoichiometry but also examine temporal variation of stoichiometric relationships. We have analysed elemental stoichiometry in the suspended POM and total (POM + DOM) organic matter (TOM) pools in the upper 100 m, and in the exported POM and sub-euphotic zone (100–500 m) inorganic nutrient pools from the monthly data collected at the Bermuda Atlantic Time-series Study (BATS) site located in the western part of the North Atlantic Ocean. C : N : P ratios in the TOM pool were more than twice that in the POM pool. Observed C : N ratios in suspended POM were approximately equal to the canonical Redfield Ratio (C : N : P = 106 : 16 : 1), while N : P and C : P ratios in the same pool were more than twice the Redfield Ratio. Average N : P ratios in the subsurface inorganic nutrient pool were ~ 26 : 1, squarely between the suspended POM ratio and the Redfield ratio. We have further linked variation in elemental stoichiometry with that of phytoplankton cell abundance observed at the BATS site. Findings from this study suggest that the variation elemental ratios with depth in the euphotic zone was mainly due to different growth rates of cyanobacterial cells. These time-series data have also allowed us to examine the potential role of climate variability on C : N : P stoichiometry. This study strengthens our understanding of elemental stoichiometry in different organic matter pools and should improve biogeochemical models by constraining the range of non-Redfield stoichiometry.

scholarly journals Impact of Remote Reemergence of the Subtropical Mode Water on Winter SST Variation in the Central North Pacific

2007 ◽  
Vol 20 (2) ◽  
pp. 173-186 ◽  
Author(s):  
Shusaku Sugimoto ◽  
Kimio Hanawa
Keyword(s):  
Mixed Layer ◽  
North Pacific ◽  
Heat Content ◽  
Aleutian Low ◽  
Mode Water ◽  
The North ◽  
Winter Mixed Layer ◽  
The North Pacific ◽  
Low Activity ◽  
Central North Pacific

Abstract Using long-term datasets of sea surface temperature (SST), core-layer temperature (CLT) of the North Pacific subtropical mode water (NPSTMW), and the North Pacific index, an impact of remote reemergence of NPSTMW on winter SST variation in the central North Pacific is quantitatively investigated. A running correlation analysis between CLT and winter SST in the remote reemergence area clearly shows that an occurrence of remote reemergence of NPSTMW strongly depends on the specific time period: occurrence period and nonoccurrence period. It is found that background conditions, such as formation rate of NPSTMW, winter mixed layer depth, ocean heat content, and buoyancy flux, play a crucial role in the period-dependent remote reemergence. In the occurrence (nonoccurrence) periods, since a large positive (negative) upper-ocean heat content anomaly is located around the central North Pacific, a deeper (shallower) winter mixed layer is formed in both the formation area and the reemergence area of NPSTMW. Therefore, a large (small) amount of NPSTMW is formed, and consequently the advective part of NPSTMW is preserved (dissipated) from (because of) a vigorous mixing due to salt-finger-type convection. In addition, larger (less) oceanic buoyancy loss contributes to an occurrence of reemergence. These are favorable (unfavorable) conditions for persistence of thermal anomalies and occurrence of reemergence in the central North Pacific. Using a multiple regression analysis, it is shown that remote reemergence gives a significant impact to an equivalent degree to the surface thermal forcing related with the Aleutian low activity on winter SST variation during the occurrence periods, while there is no significant contribution to SST variation during the nonoccurrence periods. It is also shown that the period-dependent reemergence closely connects with the Aleutian low activity with a lag of 6 to 8 yr, that is, the spinup/spindown of the subtropical gyre.

scholarly journals Global Ocean Particulate Organic Carbon Flux Merged with Satellite Parameters

2016 ◽  
Author(s):  
Colleen B. Mouw ◽  
Audrey Barnett ◽  
Galen A. McKinley ◽  
Lucas Gloege ◽  
Darren Pilcher
Keyword(s):  
Time Series ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Net Primary Production ◽  
Mixed Layer Depth ◽  
Deep Ocean ◽  
Euphotic Zone ◽  
Sediment Traps ◽  
Global Ocean ◽  
Carbon Export

Abstract. Particulate organic carbon (POC) flux estimated from POC concentration observations from sediment traps and 234Th are compiled across the global ocean. The compilation includes six time series locations: CARIACO, K2, OSP, BATS, OFP and HOT. Efficiency of the biological pump of carbon to the deep ocean depends largely on biologically mediated export of carbon from the surface ocean and its remineralization with depth, thus biologically related parameters able to be estimated from satellite observations were merged at the POC observation sites. Satellite parameters include: net primary production, percent microplankton, sea surface temperature, photosynthetically active radiation, diffuse attenuation coefficient at 490 nm, euphotic zone depth, as well as, climatological mixed layer depth. 85 % of the observations across the globe are concentrated in the Northern Hemisphere with 44 % of the data record overlapping the satellite record. Time series sites accounted for 36 % of the data. 71 % of the data is measured at ≥ 500 m with the most common deployment depths between 1000 and 1500 m. This dataset is valuable for investigations of CO2 drawdown, carbon export, remineralization, and sequestration. The compiled data can be freely accessed at doi:10.1594/PANGAEA.855600.

scholarly journals Twenty-One Years of Phytoplankton Bloom Phenology in the Barents, Norwegian, and North Seas

2021 ◽  
Vol 8 ◽  
Author(s):  
Edson Silva ◽  
François Counillon ◽  
Julien Brajard ◽  
Anton Korosov ◽  
Lasse H. Pettersson ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Barents Sea ◽  
Phytoplankton Bloom ◽  
Mixed Layer Depth ◽  
Euphotic Zone ◽  
Norwegian Sea ◽  
The North ◽  
Suspended Particulate ◽  
The North Sea ◽  
Satellite Chlorophyll

Phytoplankton blooms provide biomass to the marine trophic web, contribute to the carbon removal from the atmosphere and can be deadly when associated with harmful species. This points to the need to understand the phenology of the blooms in the Barents, Norwegian, and North seas. We use satellite chlorophyll-a from 2000 to 2020 to assess robust climatological and the interannual trends of spring and summer blooms onset, peak day, duration and intensity. Further, we also correlate the interannual variability of the blooms with mixed layer depth (MLD), sea surface temperature (SST), wind speed and suspended particulate matter (SPM) retrieved from models and remote sensing. The climatological spring blooms start on March 10th and end on June 19th. The climatological summer blooms begin on July 13th and end on September 17th. In the Barents Sea, years of shallower mixed layer (ML) driven by both calm waters and higher freshwaters input keeps the phytoplankton in the euphotic zone, causing the spring bloom to start earlier and reach higher biomass but end sooner due to the lack of nutrients upwelling from the deep. In the Norwegian Sea, a correlation between SST and the spring blooms is found. Here, warmer waters are correlated to earlier and stronger blooms in most regions but with later and weaker blooms in the eastern Norwegian Sea. In the North Sea, years of shallower ML reduces the phytoplankton sinking below the euphotic zone and limits the SPM increase from the bed shear stress, creating an ideal environment of stratified and clear waters to develop stronger spring blooms. Last, the summer blooms onset, peak day and duration have been rapidly delaying at a rate of 1.25-day year–1, but with inconclusive causes based on the parameters assessed in this study.

Sign in / Sign up

Export Citation Format

Share Document