Ocean Carbon & Biogeochemistry
Studying marine ecosystems and biogeochemical cycles in the face of environmental change
  • Home
  • About OCB
    • About Us
    • Get Involved
    • Project Office
    • Code of Conduct
    • Scientific Steering Committee
    • OCB committees
      • Ocean Time-series
      • US Biogeochemical-Argo
      • Ocean-Atmosphere Interaction
    • Scientific Breadth
      • Biological Pump
      • Changing Marine Ecosystems
      • Changing Ocean Chemistry
      • Estuarine and Coastal Carbon Fluxes
      • Ocean Carbon Uptake and Storage
      • Ocean Observatories
  • Activities
    • OCB Webinar Series
    • Summer Workshops
    • Scoping Workshops
      • Ecological Forecasting – North American Coastlines
      • Expansion of BGC-Argo and Profiling Floats
      • Future BioGeoSCAPES program
      • Ocean-Atmosphere Interactions
      • Oceanic Methane & Nitrous Oxide
    • Other Workshops
      • GO-BCG Scoping Workshop
    • Science Planning
      • Coastal CARbon Synthesis (CCARS)
      • North Atlantic-Arctic
    • Ocean Acidification PI Meetings
    • Training Activities
      • PACE Training Activity
  • Small Group Activities
    • Aquatic Continuum OCB-NACP Focus Group
    • Arctic-COLORS Data Synthesis
    • Carbon Isotopes in the Ocean Workshop
    • CMIP6 WG
      • CMIP6 Models Workshop
    • C-saw extreme events workshop
    • Filling the gaps air–sea carbon fluxes WG
    • Fish Carbon WG
      • Fish Carbon WG Workshop
      • Fish carbon workshop summary
    • Lateral Carbon Flux in Tidal Wetlands
    • Metaproteomic Intercomparison
    • Mixotrophs & Mixotrophy WG
    • N-Fixation WG
    • Ocean Carbonate System Intercomparison Forum
    • Ocean Carbon Uptake WG
    • Ocean Nucleic Acids ‘Omics
    • OOI BGC sensor WG
    • Phytoplankton Taxonomy WG
    • Problem solving in marine carbon dioxide removal (mCDR)
      • Marine CDR Workshop
  • Science Support
    • Data management and archival
    • Early Career
    • Funding Sources
    • Jobs & Postdocs
    • Meeting List
    • OCB topical websites
      • Ocean Fertilization
      • Trace gases
      • US IIOE-2
    • Outreach & Education
    • Promoting your science
    • Student Opportunities
    • OCB Activity Proposal Solicitations
    • Travel Support
  • Publications
    • Ocean Carbon Exchange
    • Newsletter Archive
    • Science Planning and Policy
    • OCB Workshop Reports
  • OCB Science Highlights
  • News

Archive for oxygen

Introducing the Coastal Ocean Data Analysis Product in North America (CODAP-NA)

Posted by mmaheigan 
· Friday, October 22nd, 2021 

Coastal ecosystems are hotspots for commercial and recreational fisheries, and aquaculture industries that are susceptible to change or economic loss due to ocean acidification. These coastal ecosystems support about 90% of the global fisheries yield and 80% of the known marine fish species, and sustain ecosystem services worth $27.7 Trillion globally (a number larger than the U.S. economy). Despite the importance of these areas and economies, internally-consistent data products for water column carbonate and nutrient chemistry data in the coastal ocean—vital to understand and predict changes in these systems—currently do not exist. A recent study published in Earth Syst. Sci. Data compiled and quality controlled discrete sampling-based data—inorganic carbon, oxygen, and nutrient chemistry, and hydrographic parameters collected from the entire North American ocean margins—to create a data product called the Coastal Ocean Data Analysis Product for North America (CODAP-NA) to fill the gap. This effort will promote future OA research, modeling, and data synthesis in critically important coastal regions to help advance the OA adaptation, mitigation, and planning efforts by North American coastal communities; and provides a foothold for future synthesis efforts in the coastal environment.

Figure caption. Sampling stations of the CODAP-NA data product.

 

Authors:
Li-Qing Jiang (University of Maryland; NOAA NCEI)
Richard A. Feely (NOAA PMEL)
Rik Wanninkhof (NOAA AOML)
Dana Greeley (NOAA PMEL)
Leticia Barbero (University of Miami; NOAA AOML)
Simone Alin (NOAA PMEL)
Brendan R. Carter (University of Washington; NOAA PMEL)
Denis Pierrot (NOAA AOML)
Charles Featherstone (NOAA AOML)
James Hooper (University of Miami; NOAA AOML)
Chris Melrose (NOAA NEFSC)
Natalie Monacci (University of Alaska Fairbanks)
Jonathan Sharp (University of Washington; NOAA PMEL)
Shawn Shellito (University of New Hampshire)
Yuan-Yuan Xu (University of Miami; NOAA AOML)
Alex Kozyr (University of Maryland; NOAA NCEI)
Robert H. Byrne (University of South Florida)
Wei-Jun Cai (University of Delaware)
Jessica Cross (NOAA PMEL)
Gregory C. Johnson (NOAA PMEL)
Burke Hales (Oregon State University)
Chris Langdon (University of Miami)
Jeremy Mathis (Georgetown University)
Joe Salisbury (University of New Hampshire)
David W. Townsend (University of Maine)

Using BGC-Argo to obtain depth-resolved net primary production

Posted by mmaheigan 
· Friday, July 23rd, 2021 

Net primary production (NPP)—the organic carbon produced by the phytoplankton minus the organic carbon respired by phytoplankton themselves—serves as a major energy source of the marine ecosystem. Traditional methods for measuring NPP rely on ship-based discrete sampling and bottle incubations (e.g., 14C incubation), which introduce potential artifacts and limit the spatial and temporal data coverage of the global ocean. The global distribution of NPP has been estimated using satellite observations, but the satellite remote sensing approach cannot provide direct information at depth.

Figure 1. Panel A. Trajectories of 5 BGC-Argo and 1 SOS-Argo with the initial float deployment locations denoted by filled symbols. The dash-line at 47° N divided the research area into the northern (temperate) and southern (subtropical) regions. Stars indicate ship stations where 14C NPP values were measured during NAAMES cruises and compared with NPP from nearby Argo floats. Panels B and C. Monthly climatologies of net primary production (NPP, mmol m-3 d-1) profiles in the northern and southern regions of the research area, derived from BGC-Argo measurements using the PPM model. The shadings indicate one standard deviation. The red dotted line indicates mixed layer depth (MLD, m), and the yellow dashed line shows euphotic depth (Z1%, m).

To fill this niche, a recent study in Journal of Geophysical Research: Biogeosciences, applied bio-optical measurements from Argo profiling floats to study the year-round depth-resolved NPP of the western North Atlantic Ocean (39° N to 54° N). The authors calculated NPP with two bio-optical models (Carbon-based Productivity Model, CbPM; and Photoacclimation Productivity Model, PPM). A comparison with NPP profiles from 14C incubation measurements showed advantages and limitations of both models. CbPM reproduced the magnitude of NPP in most cases, but had artifacts in the summer (a large NPP peak in the subsurface) due to the subsurface chlorophyll maximum caused by photoacclimation. PPM avoided the artifacts in the summer from photoacclimation, but the magnitude of PPM-derived NPP was smaller than the 14C result. Latitudinally varying NPP were observed, including higher winter NPP/lower summer NPP in the south, timing differences in NPP seasonal phenology, and different NPP depth distribution patterns in the summer months. With a 6-month record of concurrent oxygen and bio-optical measurements from two Argo floats, the authors also demonstrated the ability of Argo profiling floats to obtain estimates of the net community production (NCP) to NPP ratio (f-ratio), ranging from 0.3 in July to -1.0 in December 2016.

This work highlights the utility of float bio-optical profiles in comparison to traditional measurements and indicates that environmental conditions (e.g. light availability, nutrient supply) are major factors controlling the seasonality and spatial (horizontal and vertical) distributions of NPP in the western North Atlantic Ocean.

 

Authors:
Bo Yang (University of Virginia, UM CIMAS/NOAA AOML)
James Fox (Oregon State University)
Michael J. Behrenfeld (Oregon State University)
Emmanuel S. Boss (University of Maine)
Nils Haëntjens (University of Maine)
Kimberly H. Halsey (Oregon State University)
Steven R. Emerson (University of Washington)
Scott C. Doney (University of Virginia)

Air-sea gas disequilibrium drove deoxygenation of the deep ice-age ocean

Posted by mmaheigan 
· Thursday, March 18th, 2021 

During the Last Glacial Maximum (~20,000 years ago, LGM) sediment data show that the deep ocean had lower dissolved oxygen (O2) concentrations than the preindustrial ocean, despite cooler temperatures of this period increasing O2 solubility in sea water.

Figure 1. a) Whole ocean inventory of the O2 components in the preindustrial control (PIC): total O2 (O2); the preformed components equilibrium O2 (O2 equilibrium), physical disequilibrium O2 (O2 diseq phys) and biologically-mediated disequilibrium (O2 diseq bio); and O2 respired from soft-tissue (O2 soft). b) The difference in whole ocean inventory of O2 components between the LGM and PIC simulations.

In a study published in Nature Geoscience, the authors provide one of the first explanations for glacial deoxygenation. The authors combined a data-constrained model of the preindustrial (PIC) and LGM ocean with a novel decomposition of O2 to assess the processes affecting the oceanic distribution of oxygen. The decomposition allowed for the preformed disequilibrium O2—the amount of oxygen that deviates from its solubility equilibrium value when at the surface—to be tracked, along with other contributions such as the O2 consumed by bacterial respiration of organic matter. In the preindustrial ocean, a third of the subsurface oxygen deficit was a result of disequilibrium rather than oxygen consumed by bacteria. This contradicts previous assumptions (Figure 1a). Nearly 80% of the disequilibrium resulted from upwelling waters, depleted in O2 due to respiration, not fully equilibrating before re-subduction into the ocean interior. This effect was even greater during the LGM (Figure 1b). The authors attributed this largely to the widespread presence of sea ice—which acts as a cap on the surface preventing the water from gaining oxygen from the atmosphere—in the ocean around Antarctica, with a smaller contribution from iron fertilization.

This study provides one of the first mechanistic explanations for LGM deep ocean deoxygenation. As the ocean is currently losing oxygen due to warming, the effect of other processes, including sea ice changes, could prove important for understanding long-term ocean oxygenation changes.

Authors
Ellen Cliff (University of Oxford)
Samar Khatiwala (University of Oxford)
Andreas Schmittner (Oregon State University)

Joint highlight with GEOTRACES International Project Office

Timing matters: Correcting float-based measurements of diurnal oxygen variability

Posted by mmaheigan 
· Friday, November 6th, 2020 

Despite its fundamental importance to the global carbon cycle, climate, and marine ecosystems, oceanic primary production is grossly under-sampled. Autonomous platforms represent an important frontier for expanding measurements of marine primary productivity in time and space, but this requires the establishment of robust, standardized methods to obtain reliable data from these platforms. Using data from profiling floats deployed in the northern Gulf of Mexico, authors of a recent study published in Biogeosciences demonstrated, for the first time, that daily cycles of dissolved oxygen can be observed with Argo-type profiling floats. The floats were instructed to profile continuously, resulting in about one profile every three hours. The floats recorded data both on the ascent (upcast) and the descent (downcast). Adjacent casts showed hysteresis in gradient areas, i.e. a lag in the concentration measurement, due to the slow response time of oxygen sensors.

Figure 1: Example of raw oxygen measurements from a downcast (dark purple line) and an upcast (dark green line) and corrected profiles (lighter purple and green lines) in (a) density and (b) pressure coordinates. (c) Upcasts and downcasts (top 150 m) plotted against each other with raw data (purple) and data corrected according to the new method (red). (d) The root-mean-square difference (RMSD) between the upcast and downcast after correcting casts for a range of time constants (τ), showing an optimal τ value in this case of 76 s (red dot).

To correct for these measurement errors, the authors developed a method to determine sensor response time in situ, using an established process for correcting sensor response time errors. This method requires a timestamp associated with each observation. The response time parameter (τ) was determined by correcting consecutive profiles taken in opposite directions using a range of possible values and finding the minimum root-mean-square-difference between them (Figure 1). In light of these findings, future oxygen measurements from Argo floats should be transmitted with time stamps for a calibration period during which up- and downcasts are recorded to facilitate response time correction. The method developed here will contribute to more accurate measurement of dissolved oxygen, thus improving the quality of derived quantities such as primary productivity.

 

Authors
Christopher Gordon (Dalhousie University)
Katja Fennel (Dalhousie University)
Clark Richards (Fisheries and Oceans Canada)
Nick Shay (University of Miami)
Jodi Brewster (University of Miami)

Estuarine sediment resuspension drives non-local impacts on biogeochemistry

Posted by mmaheigan 
· Friday, September 18th, 2020 

Sediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. In a recent paper published in Estuaries and Coasts, the authors quantified the degree to which sediment resuspension and transport affected estuarine biogeochemistry by implementing a coupled hydrodynamic-sediment transport-biogeochemical model of the Chesapeake Bay. By comparing summertime model runs that either included or neglected seabed resuspension, the study revealed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, which subsequently shifted primary production downstream (Figure 1). Resuspension also increased remineralization in the central Bay, which experienced higher organic matter concentrations due to the downstream shift in primary productivity. When combined with estuarine circulation, these resuspension-induced shifts caused oxygen to increase and ammonium to increase throughout the Bay in the bottom portion of the water column. Averaged over the channel, resuspension decreased oxygen by ~25% and increased ammonium by ~50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between wet and dry years. This work highlights the importance of a localized process like sediment resuspension and its capacity to drive biogeochemical variations on larger spatial scales. Documenting the spatiotemporal footprint of these processes is critical for understanding and predicting the response of estuarine and coastal systems to environmental changes, and for informing management efforts.

Figure 1: Schematic of how resuspension affects biogeochemical processes based on HydroBioSed model estimates for Chesapeake Bay.

Authors:
Julia M. Moriarty (University of Colorado Boulder)
Marjorie A. M. Friedrichs (Virginia Institute of Marine Science)
Courtney K. Harris (Virginia Institute of Marine Science)

 

Also see the Geobites piece “Muddy waters lead to decreased oxygen in Chesapeake Bay” on this publication, by Hadley McIntosh Marcek

Turning a spotlight on grazing

Posted by mmaheigan 
· Thursday, July 23rd, 2020 

Microscopic plankton in the surface ocean make planet Earth habitable by generating oxygen and forming the basis of marine food webs, yielding harvestable protein. For over 100 years, oceanographers have tried to ascertain the physical, chemical, and biological processes governing phytoplankton blooms. Zooplankton grazing of phytoplankton is the single largest loss process for primary production, but empirical grazing data are sparse and thus poorly constrained in modeling frameworks, including assessments of global elemental cycles, cross-ecosystem comparisons, and predictive efforts anticipating future ocean ecosystem function. As sunlight decays exponentially with depth, upper-ocean mixing creates dynamic light environments with predictable effects on phytoplankton growth but unknown consequences for grazing.

Figure caption: Rates (d−1) of phytoplankton growth (μ), grazing mortality (g), and biomass accumulation (r) under four mixed layer scenarios simulated using light as a proxy of (a) sustained deep mixing, (b) rapid shoaling, (c) sustained shallow mixing, and (d) rapid mixed layer deepening. Error bars represent one standard deviation of the mean of duplicate experiments. Grazing was measured but not detected in the sustained deep mixing and rapid shoaling conditions, denoted with x.

Using data from a spring cruise in the North Atlantic, authors of a recent study published in Limnology & Oceanography compared the influences of microzooplankton predation and fluctuations in light availability—representative of a mixing water column—on phytoplankton standing stock. Data from at-sea incubations and light manipulation experiments provide evidence that phytoplankton’s instantaneous and zooplankton’s delayed responses to light fluctuations are key modulators of the balance between phytoplankton growth and grazing rates (Figure 1). These results suggest that light is a potential, remotely retrievable predictor of when and where in the ocean zooplankton grazing may represent an important loss term of phytoplankton production. If broadly verified, this approach could be used to systematically assess sparsely measured grazing across spatial and temporal gradients in representative regions of the ocean. Such data will be essential for enhancing our predictive capacity of ocean food web function, global biogeochemical cycles and the many derived processes, including fisheries production and the flow of carbon through the oceans.

Authors:
Françoise Morison (University of Rhode Island)
Gayantonia Franzè (University of Rhode Island, currently Institute of Marine Research, Norway)
Elizabeth Harvey (University of Georgia, currently University of New Hampshire)
Susanne Menden-Deuer (University of Rhode Island)

 

Modern OMZ copepod dynamics provide analog for future oceans

Posted by mmaheigan 
· Thursday, July 23rd, 2020 

Global warming increases ocean deoxygenation and expands the oxygen minimum zone (OMZ), which has implications for major zooplankton groups like copepods. Reduced oxygen levels may impact individual copepod species abundance, vertical distribution, and life history strategy, which is likely to perturb intricate oceanic food webs and export processes. In a study recently published in Biogeosciences, authors conducted vertically-stratified day and night MOCNESS tows (0-1000 m) during four cruises (2007-2017) in the Eastern Tropical North Pacific, sampling hydrography and copepod distributions in four locations with different water column oxygen profiles and OMZ intensity (i.e. lowest oxygen concentration and its vertical extent in a profile). Each copepod species exhibited a different vertical distribution strategy and physiology associated with oxygen profile variability. The study identified sets of species that (1) changed their vertical distributions and maximum abundance depth associated with the depth and intensity of the OMZ and its oxycline inflection points, (2) shifted their diapause depth, (3) adjusted their diel vertical migration, especially the nighttime upper depth, or (4) expanded or contracted their depth range within the mixed layer and upper part of the thermocline in association with the thickness of the aerobic epipelagic zone (habitat compression concept) (Figure 1). Distribution depths for some species shifted by 10’s to 100’s of meters in different situations, which also had metabolic (and carbon flow) implications because temperature decreased with depth.  This observed present-day variability may provide an important window into how future marine ecosystems will respond to deoxygenation.

Figure caption: Schematic diagram showing how future OMZ expansion may affect zooplankton distributions, based on present-day responses to OMZ variability. The dashed line indicates diel vertical migration (DVM) and highlights the shoaling of the nighttime depth as the aerobic habitat is compressed. The lower oxycline community and the diapause layer for some species, associated with a specific oxygen concentration, may deepen as the OMZ expands.

 

Authors:
Karen F. Wishner (University of Rhode Island)
Brad Seibel (University of South Florida)
Dawn Outram (University of Rhode Island)

The competing impacts of climate change and nutrient reductions on dissolved oxygen in Chesapeake Bay

Posted by mmaheigan 
· Wednesday, June 12th, 2019 

The Chesapeake Bay is a 200-mile-long estuary with both economic and ecological importance to the mid-Atlantic region. Runoff, pollution, and algae blooms resulting in hypoxia have been major issues over the past 50 years, and much work has been done to improve the water quality and health of the Bay. Dissolved oxygen concentrations will be altered in response to climate change, but whether this will counteract the benefits of reduced nutrient loading is an important scientific and management question. Specifically, what are the impacts of climate change on future Chesapeake Bay hypoxia and on progress towards meeting water quality standards associated with the Chesapeake Bay Total Maximum Daily Load (TMDL)?

(Left) Latitudinal along-bay dissolved oxygen (DO) transects for the Base scenario (Base+noCC) and TMDL scenario (TMDL+noCC) without climate change; transects for the absolute and percent changes in DO due to climate change (TMDL+CC). (Right) Cumulative hypoxic volume for six ranges of DO concentrations for each of the study years and each of the scenarios (colored circles).

A recent study in Biogeosciences quantified the competing impacts of climate change and nutrient reductions on Chesapeake Bay hypoxia. The authors used a 3-D modeling system along with projected mid-21st century changes in temperature, freshwater flow, and sea level, assuming fully achieved goals of TMDL nutrient reductions. Of these three climate change factors, increased temperature most strongly impacts future hypoxia, primarily due to decreased solubility year-round and increased respiration and remineralization in the spring. Sea level rise is expected to exhibit a small positive impact resulting from increased estuarine circulation and reduced residence time. Increased river flow is anticipated to exert a small negative impact due to increased nutrient loading.

These results demonstrate that climate change may limit the effectiveness of future management actions aimed at reducing nutrient inputs to the Chesapeake Bay. However, the positive impacts of mandated nutrient reductions still outweigh the negative impacts of climate change. Given that climate impacts are expected to intensify with time and large uncertainties remain among different climate projections, it is critical to continue examining how the Bay may evolve in the future by assessing the sensitivity of oxygen concentrations to different climate change scenarios.

 

Authors:
Isaac D. Irby (VIMS, William & Mary)
Marjorie A. M. Friedrichs (VIMS, William & Mary)
Fei Da (VIMS, William & Mary)
Kyle E. Hinson (VIMS, William & Mary)

Impacts of atmospheric nitrogen deposition and coastal nitrogen fluxes on oxygen concentrations in Chesapeake Bay

Posted by mmaheigan 
· Tuesday, April 30th, 2019 

How do atmospheric and oceanic nutrients impact oxygen concentrations in the Chesapeake Bay? Generally, researchers focus on how terrestrial nutrients impact hypoxia. The relative importance of river, atmosphere, and ocean inputs have not been quantified, largely because estimates of nitrogen fluxes from the atmosphere and ocean are limited.

A recent study in Journal of Geophysical Research: Oceans quantified the relative impacts of atmospheric and oceanic nitrogen inputs on dissolved oxygen (DO) in the Chesapeake Bay. The authors combined a 3-D biogeochemical model and estimates of atmospheric deposition from the Community Multiscale Air Quality model and interpolations of nitrogen concentrations along the continental shelf from the Ocean Acidification Data Stewardship Project. Atmospheric nitrogen deposition and coastal nitrogen fluxes most impact Chesapeake Bay DO concentrations during the summer when surface waters are depleted in nitrogen. Overall, atmospheric nitrogen deposition has about the same gram-for-gram impact on Chesapeake Bay DO as riverine loading. Although all three nutrient sources vary spatially and temporally, in the central bay, where summer hypoxia is most prevalent, coastal nitrogen fluxes and atmospheric nitrogen fluxes have roughly the same impact on bottom oxygen as a ~10% change in riverine nitrogen loading (Figure 1).

Figure caption: (Left) Four-year (2002–2005) average increase in DO in the summer by removing the atmospheric nitrogen deposition (AtmN), reducing the riverine loading (ΔRiverN) by ~10% (roughly equivalent to turning off the atmospheric deposition), and removing the nitrogen fluxes from the continental shelf (CoastalN). (Right) Relative impacts of the three nitrogen modification scenarios on summertime bottom DO.

These results indicate that two often-neglected sources of nitrogen—direct atmospheric deposition and fluxes of nitrogen from the continental shelf—substantially impact Chesapeake Bay DO, especially in the summer. Future study is needed to investigate the long-term trend of these relative impacts by continued coordination between modeling and observational work, such as applying higher-resolution atmospheric deposition products and integrating more in situ data along the model ocean boundary when they are available. These efforts will improve our understanding of the impacts of different nutrient sources on biogeochemical cycles in coastal water bodies.

 

Authors:
Fei Da (VIMS, College of William & Mary)
Marjorie A. M. Friedrichs (VIMS, College of William & Mary)
Pierre St-Laurent (VIMS, College of William & Mary)

Autonomous measurement of N-loss in the Eastern Tropical North Pacific ODZ: An Invitation for Collaboration

Posted by mmaheigan 
· Thursday, January 10th, 2019 

By Mark A. Altabet (SMAST/U. Mass. Dartmouth), Craig McNeil, and Eric D’Asaro (both at APL / U. Washington)

Oxygen deficient zones (ODZs) constitute a small fraction of total oceanic volume yet play an important role in regulating global ocean carbon and nitrogen cycles. They are critical for regulating the ocean’s nitrogen budget, as loss of biologically available nitrogen to N2 gas (N-loss) within ODZs is estimated to be 30 to 50% of the global total. However, temporal and spatial variability in N-loss rates have been undersampled by ship-based process studies leaving substantial uncertainty in overall rates. While local and short-term regulation of N-loss by O2 and organic matter availability is well documented, little is known about the larger scale temporal/spatial variability in N-loss that may result from physical forcings such as remote ventilation, seasonal variability in vertical exchange with the near-surface layer, and mesoscale eddies. Understanding the impact of larger scale physical forcings on N-loss as mediated through O2 and organic flux is needed to fully understand the causes and consequences of any future ODZ expansion. To achieve this, we need sustained observations by a distributed array capable of detecting synoptic variability.

To address these issues, a new NSF-funded project will carry out a multiyear, autonomous float-based observational program to answer the following questions:

  • How does biogenic N2 production in ODZs vary over weekly to annual time scales and space scales of 10s to 1000s km?
  • What are the major scales of variability and their associated oceanographic phenomena and how do they relate to control by organic matter flux and O2 concentration?
  • How does this variability influence regionally integrated N-loss?

Figure 1. The ETNP ODZ roughly defined by O2 <1.5 μmol/kg (orange, World Ocean Atlas 2013). Our new NSF-funded project will sample across these patterns of spatial and temporal variability for 2 years with 10 subsurface ODZ floats (red/blue) each measuring profiles of T, S, O2 (50 nmol/kg LOD) and N2 (0.1 μmol/kg precision), and the in situ rate of N2 change. Four Argo floats with O2 sensors and BioOptical floats provided by collaborators will supplement this array. Bright bar symbols are the planned deployment positions; dimmed bar symbols suggest possible displacements after 2 years. Ship-based measurements (yellow stars) along the deployment cruise track (magenta) will be used for float sensor calibration and identification of ETNP source water properties. The 2-year track of our prototype GasFloat is also shown (black line).

This project will exploit our ability to make in situ, ultra-high precision measurement of N2 concentration (~0.1 umol/kg) and use commercially available O2 sensors to measure O2 in the 10s of nM range. Our study area is the Eastern Tropical North Pacific (ETNP), the largest ODZ and the region of our successful pilot deployments (Figure 1). Over a multi-year period, our study will determine in situ nM-level O2 and biogenic N2 on float profiles distributed throughout the ETNP and encompassing geographic gradients in O2 and surface productivity. For the first time, our study will also determine in situ N-loss rates from changes in N2 concentration during one- to two-week Lagrangian float deployments drifting along a constant density surface (Figure 2). A pilot two-year float (‘GasFloat, Figure 1) deployment in the ETNP has documented our ability to do so. Critically, our float-based approach more closely matches the frequency and distribution of observations to the expected variability in biogenic N2 production, as compared to prior work. This study will also dramatically increase the data density in this region by acquiring >500 profiles/drifts for N2 and >1000 profiles for nM O2.

Figure 2. (a) Schematic of float system to be deployed (b) Example of float mission including 2-week isopycnal drift.

We anticipate float deployment in summer 2020 via a UNOLS vessel. Investigators interested in collaborative participation through contribution of autonomous instrumentation and/or making shipboard measurements are encouraged to contact the lead PI Mark Altabet at maltabet@umassd.edu.  Similarly, students interested in graduate research opportunities through this project should contact the lead PI.

Next Page »

Filter by Keyword

abundance acidification africa air-sea interactions air-sea interface algae alkalinity allometry ammonium AMOC anoxia anoxic Antarctic anthropogenic carbon aquaculture aragonite saturation arctic arsenic Atlantic Atlantic modeling atmospheric carbon atmospheric CO2 atmospheric nitrogen deposition authigenic carbonates autonomous platforms bacteria BATS benthic bgc argo bio-go-ship bio-optical bioavailability biogeochemical cycles biogeochemical models biogeochemistry Biological Essential Ocean Variables biological pump biological uptake biophysics bloom blooms blue carbon bottom water boundary layer buffer capacity C14 CaCO3 calcification calcite carbon-climate feedback carbon-sulfur coupling carbon budget carbon cycle carbon dioxide carbon sequestration carbon storage Caribbean CCA CCS changi changing marine ecosystems changing marine environments changing ocean chemistry chemical oceanographic data chemoautotroph chesapeake bay chl a chlorophyll circulation climate change CO2 CO2YS coastal darkening coastal ocean cobalt Coccolithophores community composition conservation cooling effect copepod coral reefs CTD currents cyclone data data management data product Data standards DCM decadal trends decomposers decomposition deep convection deep ocean deep sea coral deoxygenation depth diagenesis diatoms DIC diel migration dimethylsulfide dinoflagellate discrete measurements dissolved inorganic carbon dissolved organic carbon DOC DOM domoic acid dust DVM earth system models ecology ecosystem state eddy Education Ekman transport emissions ENSO enzyme equatorial regions error ESM estuarine and coastal carbon fluxes estuary euphotic zone eutrophication evolution export EXPORTS extreme events extreme weather events faecal pellets filter feeders filtration rates fire fish Fish carbon fisheries floats fluid dynamics fluorescence food webs forams freshening freshwater frontal zone fronts functional role future oceans geochemistry geoengineering geologic time GEOTRACES glaciers gliders global carbon budget global ocean global warming go-ship grazing greenhouse gas Greenland groundwater Gulf of Maine Gulf of Mexico Gulf Stream gyre harmful algal bloom high latitude human food human impact hurricane hydrothermal hypoxia ice age ice cores ice cover industrial onset inverse circulation iron iron fertilization isotopes jellies katabatic winds kelvin waves krill kuroshio land-ocean continuum larvaceans lateral transport LGM lidar ligands light light attenuation lipids mangroves marine carbon cycle marine heatwave marine snowfall marshes Mediterranean meltwater mesopelagic mesoscale metagenome metals methane methods microbes microlayer microorganisms microscale microzooplankton midwater mixed layer mixed layers mixotrophy modeling mode water molecular diffusion MPT multi-decade n2o NAAMES NASA NCP net community production new technology Niskin bottle nitrate nitrogen nitrogen fixation nitrous oxide north atlantic north pacific nutricline nutrient budget nutrient cycling nutrient limitation nutrients OA ocean-atmosphere ocean acidification ocean acidification data ocean carbon uptake and storage ocean color ocean observatories ODZ oligotrophic omics OMZ open ocean optics organic particles overturning circulation oxygen pacific paleoceanography particle flux pCO2 PDO peat pelagic PETM pH phenology phosphorus photosynthesis physical processes physiology phytoplankton PIC plankton POC polar regions pollutants predation prediction primary productivity Prochlorococcus proteins pteropods pycnocline radioisotopes remineralization remote sensing repeat hydrography residence time resource management respiration resuspension rivers rocky shore Rossby waves Ross Sea ROV salinity salt marsh satell satellite scale seafloor seagrass sea ice sea level rise seasonal patterns sea spray seaweed sediments sensors shelf system shells ship-based observations shorelines silicate sinking particles size SOCCOM soil carbon southern ocean south pacific spatial covariations speciation SST stoichiometry subduction submesoscale subpolar subtropical sulfate surf surface surface ocean Synechococcus teleconnections temperate temperature temporal covariations thermocline thermohaline thorium tidal time-series time of emergence top predators total alkalinity trace elements trace metals trait-based transfer efficiency transient features trophic transfer tropical turbulence twilight zone upper ocean upper water column upwelling US CLIVAR validation velocity gradient ventilation vertical flux vertical migration vertical transport volcano warming water clarity water quality western boundary currents wetlands winter mixing zooplankton

Copyright © 2022 - OCB Project Office, Woods Hole Oceanographic Institution, 266 Woods Hole Rd, MS #25, Woods Hole, MA 02543 USA Phone: 508-289-2838  •  Fax: 508-457-2193  •  Email: ocb_news@us-ocb.org

link to nsflink to noaalink to WHOI

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.