scholarly journals Large increase in dissolved inorganic carbon flux from the Mississippi River to Gulf of Mexico due to climatic and anthropogenic changes over the 21st century

2015 ◽  
Vol 120 (4) ◽  
pp. 724-736 ◽  
Author(s):  
Wei Ren ◽  
Hanqin Tian ◽  
Bo Tao ◽  
Jia Yang ◽  
Shufen Pan ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
21St Century ◽  
Mississippi River ◽  
Carbon Flux ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Anthropogenic Changes

scholarly journals Texas A&M University Radiocarbon Dates IV

Radiocarbon ◽  
1978 ◽  
Vol 20 (3) ◽  
pp. 455-460 ◽  
Author(s):  
R A Parker ◽  
W M Sackett
Keyword(s):  
Water Column ◽  
Mississippi River ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
River Delta ◽  
Cariaco Basin ◽  
Mississippi River Delta ◽  
Radiocarbon Dates ◽  
Carbonate Carbon ◽  
Total Dissolved Inorganic Carbon

Organic and carbonate carbon in sediments deposited in the Cariaco Basin and on the Mississippi River Delta and the total dissolved inorganic carbon in four water column profiles comprise the samples in this list. Except as noted below the samples were processed using the benzene synthesis and other procedures described by Mathews, et al (1972).

scholarly journals Robotic observations of high wintertime carbon export in California coastal waters

2016 ◽  
Vol 13 (10) ◽  
pp. 3109-3129 ◽  
Author(s):  
James K. B. Bishop ◽  
Michael B. Fong ◽  
Todd J. Wood
Keyword(s):  
Surface Waters ◽  
Coastal Waters ◽  
Carbon Flux ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
High Surface ◽  
Carbon Export ◽  
Santa Barbara ◽  
San Pedro ◽  
Mesopelagic Zone

Abstract. Biologically mediated particulate organic and inorganic carbon (POC and PIC) export from surface waters is the principal determinant of the vertical oceanic distribution of pH and dissolved inorganic carbon and thus sets the conditions for air–sea exchange of CO2; exported organic matter also provides the energy fueling communities in the mesopelagic zone. However, observations are temporally and spatially sparse. Here we report the first hourly-resolved optically quantified POC and PIC sedimentation rate time series from an autonomous Lagrangian Carbon Flux Explorer (CFE), which monitored particle flux using an imaging optical sedimentation recorder (OSR) at depths below 140 m in the Santa Cruz Basin, CA, in May 2012, and in January and March 2013. Highest POC vertical flux ( ∼  100–240 mmol C m−2 d−1) occurred in January, when most settling material was millimeter- to centimeter-sized aggregates but when surface biomass was low; fluxes were  ∼  18 and  ∼  6 mmol C m−2 d−1, respectively, in March and May, under high surface biomass conditions. An unexpected discovery was that January 2013 fluxes measured by CFE were 20 times higher than that measured by simultaneously deployed surface-tethered OSR; multiple lines of evidence indicate strong undersampling of aggregates larger than 1 mm in the latter case. Furthermore, the January 2013 CFE fluxes were about 10 times higher than observed during multiyear sediment trap observations in the nearby Santa Barbara and San Pedro basins. The strength of carbon export in biologically dynamic California coastal waters is likely underestimated by at least a factor of 3 and at times by a factor of 20.

scholarly journals Transect Along 24°n Latitude of 14C in Dissolved Inorganic Carbon in the Subtropical North Atlantic Ocean

Radiocarbon ◽  
1996 ◽  
Vol 38 (3) ◽  
pp. 407-414 ◽  
Author(s):  
Jeffrey P. Severinghaus ◽  
Wallace S. Broecker ◽  
Tsung-Hung Peng ◽  
Georges Bonani
Keyword(s):  
Atlantic Ocean ◽  
Gulf Of Mexico ◽  
North Atlantic ◽  
Inorganic Carbon ◽  
North Atlantic Ocean ◽  
Dissolved Inorganic Carbon ◽  
Powerful Constraint ◽  
Upper Ocean Mixing ◽  
Main Thermocline ◽  
East West

The distribution of bomb-produced 14C in the ocean provides a powerful constraint for circulation models of upper ocean mixing. We report 14C measurements from an east-west section of the main thermocline at 24°N latitude in the subtropical North Atlantic Ocean in summer 1992, and one profile from the Gulf of Mexico in 1993. Observed gradients reflect the transient invasion of bomb 14C into the thermocline via mixing along isopycnals from the poleward outcrop, with progressively more sluggish mixing at greater depths. A slight deepening of the profile is observed over the 20-yr period since the GEOSECS survey at one location where the comparison is possible.

scholarly journals Robotic observations of high wintertime carbon export in California coastal waters

2016 ◽  
Author(s):  
J. K. B. Bishop ◽  
M. B. Fong ◽  
T. J. Wood
Keyword(s):  
Surface Waters ◽  
Coastal Waters ◽  
Carbon Flux ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
High Surface ◽  
Sediment Traps ◽  
Carbon Export ◽  
Mesopelagic Zone ◽  
Under Sampling

Abstract. Biologically mediated particulate organic and inorganic carbon (POC and PIC) export from surface waters is the principal determinant of the vertical oceanic distribution of pH and dissolved inorganic carbon and thus sets the conditions for air sea exchange of CO2; exported organic matter also provides the energy fuelling communities in the mesopelagic zone. However, observations are temporally and spatially sparse. Here we report first hourly-resolved optically-quantified POC and PIC sedimentation rate time series from autonomous Lagrangian Carbon Flux Explorers (CFEs), which monitor particle flux using imaging at depths below 140 m in the Santa Cruz Basin, CA in May 2012, and in January and March 2013. Highest POC vertical flux (~100–240 mmol C m−2 d−1) occurred in January, when most settling material was mm to cm-sized aggregates, but when surface biomass was low; fluxes were ~18 and 6 mmol C m−2 d−1, respectively in March and May, under high surface biomass conditions. An unexpected discovery was that January 2013 fluxes measured by CFE were 20 times higher than simultaneously deployed surface-tethered sediment traps and which multiple lines of evidence indicate strong under sampling of aggregates larger than 1 mm. Furthermore, the Jan 2013 CFE fluxes were about 10 times higher compared to highest previous nearby multi year sediment trap observations. The strength of carbon export in biologically dynamic California coastal waters is likely underestimated by a factor of between 3 and 20.

scholarly journals Early Diagenesis in the Hypoxic and Acidified Zone of the Northern Gulf of Mexico: Is Organic Matter Recycling in Sediments Disconnected From the Water Column?

2021 ◽  
Vol 8 ◽  
Author(s):  
Christophe Rabouille ◽  
Bruno Lansard ◽  
Shannon M. Owings ◽  
Nancy N. Rabalais ◽  
Bruno Bombled ◽  
...  
Keyword(s):  
Organic Matter ◽  
Gulf Of Mexico ◽  
Continental Shelf ◽  
Mississippi River ◽  
Dissolved Inorganic Carbon ◽  
Low Oxygen ◽  
Northern Gulf Of Mexico ◽  
Bottom Waters ◽  
Seasonal Hypoxia ◽  
Organic Matter Recycling

Hypoxia and associated acidification are growing concerns for ecosystems and biogeochemical cycles in the coastal zone. The northern Gulf of Mexico (nGoM) has experienced large seasonal hypoxia for decades linked to the eutrophication of the continental shelf fueled by the Mississippi River nutrient discharge. Sediments play a key role in maintaining hypoxic and acidified bottom waters, but this role is still not completely understood. In the summer 2017, when the surface area of the hypoxic zone in the nGoM was the largest ever recorded, we investigated four stations on the continental shelf differentially influenced by river inputs of the Mississippi-Atchafalaya River System and seasonal hypoxia. We investigated diagenetic processes under normoxic, hypoxic, and nearly anoxic bottom waters by coupling amperometric, potentiometric, and voltammetric microprofiling with high-resolution diffusive equilibrium in thin-films (DET) profiles and porewater analyses. In addition, we used a time-series of bottom-water dissolved oxygen from May to November 2017, which indicated intense O2 consumption in bottom waters related to organic carbon recycling. At the sediment-water interface (SWI), we found that oxygen consumption linked to organic matter recycling was large with diffusive oxygen uptake (DOU) of 8 and 14 mmol m–2 d–1, except when the oxygen concentration was near anoxia (5 mmol m–2 d–1). Except at the station located near the Mississippi river outlet, the downcore pore water sulfate concentration decrease was limited, with little increase in alkalinity, dissolved inorganic carbon (DIC), ammonium, and phosphate suggesting that low oxygen conditions did not promote anoxic diagenesis as anticipated. We attributed the low anoxic diagenesis intensity to a limitation in organic substrate supply, possibly linked to the reduction of bioturbation during the hypoxic spring and summer.

scholarly journals Dissolved carbon biogeochemistry and export in mangrove-dominated rivers of the Florida Everglades

2017 ◽  
Vol 14 (9) ◽  
pp. 2543-2559 ◽  
Author(s):  
David T. Ho ◽  
Sara Ferrón ◽  
Victor C. Engel ◽  
William T. Anderson ◽  
Peter K. Swart ◽  
...  
Keyword(s):  
Carbon Flux ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Co2 Exchange ◽  
Coastal Ocean ◽  
Florida Everglades ◽  
Mangrove Forests ◽  
Dissolved Carbon ◽  
Doc Export ◽  
Source Sink

Abstract. The Shark and Harney rivers, located on the southwest coast of Florida, USA, originate in the freshwater, karstic marshes of the Everglades and flow through the largest contiguous mangrove forest in North America. In November 2010 and 2011, dissolved carbon source–sink dynamics was examined in these rivers during SF6 tracer release experiments. Approximately 80 % of the total dissolved carbon flux out of the Shark and Harney rivers during these experiments was in the form of inorganic carbon, either via air–water CO2 exchange or longitudinal flux of dissolved inorganic carbon (DIC) to the coastal ocean. Between 42 and 48 % of the total mangrove-derived DIC flux into the rivers was emitted to the atmosphere, with the remaining being discharged to the coastal ocean. Dissolved organic carbon (DOC) represented ca. 10 % of the total mangrove-derived dissolved carbon flux from the forests to the rivers. The sum of mangrove-derived DIC and DOC export from the forest to these rivers was estimated to be at least 18.9 to 24.5 mmol m−2 d−1, a rate lower than other independent estimates from Shark River and from other mangrove forests. Results from these experiments also suggest that in Shark and Harney rivers, mangrove contribution to the estuarine flux of dissolved carbon to the ocean is less than 10 %.

scholarly journals Dissolved Carbon Transport and Processing in North America’s Largest Swamp River Entering the Northern Gulf of Mexico

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1395
Author(s):  
Emily M. DelDuco ◽  
Y. Jun Xu
Keyword(s):  
Gulf Of Mexico ◽  
Carbon Cycling ◽  
Mississippi River ◽  
Dissolved Inorganic Carbon ◽  
Isotope Composition ◽  
River System ◽  
Floodplain Wetland ◽  
Co2 Partial Pressure ◽  
River Waters ◽  
Dissolved Carbon

Transport and transformation of riverine dissolved carbon is an important component of global carbon cycling. The Atchafalaya River (AR) flows 189 kilometers through the largest bottomland swamp in North America and discharges ~25% of the flow of the Mississippi River into the Gulf of Mexico annually, providing a unique opportunity to study the floodplain/wetland impacts on dissolved carbon. The aim of this study is to determine how dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the AR change spatially and seasonally, and to elucidate which processes control the carbon cycling in this intricate swamp-river system. From May 2015 to May 2016, we conducted monthly river sampling from the river’s inflow to its outflow, analyzing samples for concentrations and δ13C stable isotope composition of DOC and DIC. We found that DIC concentrations in the AR were three times higher than the DOC concentrations on average, and showed more pronounced downstream changes than the DOC. During the study period, the river discharged a total of 5.35 Tg DIC and a total of 2.34 Tg DOC into the Gulf of Mexico. Based on the mass inflow–outflow balance, approximately 0.53 Tg (~10%) of the total DIC exported was produced within the floodplain/wetland system, while 0.24 Tg (~10%) of the DOC entering the basin was removed. The AR’s water was consistently oversaturated with CO2 partial pressure (pCO2) above the atmospheric pCO2 (with pCO2 varying from 551 µatm to 6922 µatm), indicating a large source of DIC from river waters to the atmosphere as well as to the coastal margins. Largest changes in carbon constituents occurred during periods of greatest inundation of the swamp-river basin and corresponded with shifts in isotopic composition. This effect was particularly pronounced during the initial flood stages, supporting the hypothesis that subtropical floodplains can act as effective enhancers of the biogeochemical cycling of dissolved carbon.

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