Ocean Carbon & Biogeochemistry
Studying marine ecosystems and biogeochemical cycles in the face of environmental change
  • Home
  • About OCB
    • About Us
    • Scientific Breadth
      • Biological Pump
      • Changing Marine Ecosystems
      • Changing Ocean Chemistry
      • Estuarine and Coastal Carbon Fluxes
      • Ocean Carbon Uptake and Storage
      • Ocean Observatories
    • Code of Conduct
    • Get Involved
    • Project Office
    • Scientific Steering Committee
    • OCB committees
      • Ocean Time-series
      • US Biogeochemical-Argo
      • Ocean-Atmosphere Interaction
  • Activities
    • Summer Workshop
    • OCB Webinars
    • Guidelines for OCB Workshops & Activities
    • Topical Workshops
      • CMIP6 Models Workshop
      • Coastal BGS Obs with Fisheries
      • C-saw extreme events workshop
      • Expansion of BGC-Argo and Profiling Floats
      • Fish, fisheries and carbon
      • Future BioGeoSCAPES program
      • GO-BCG Scoping Workshop
      • Lateral Carbon Flux in Tidal Wetlands
      • Leaky Deltas Workshop – Spring 2025
      • Marine CDR Workshop
      • Ocean Nucleic Acids ‘Omics
      • Pathways Connecting Climate Changes to the Deep Ocean
    • Small Group Activities
      • Aquatic Continuum OCB-NACP Focus Group
      • Arctic-COLORS Data Synthesis
      • BECS Benthic Ecosystem and Carbon Synthesis WG
      • Carbon Isotopes in the Ocean Workshop
      • CMIP6 WG
      • Filling the gaps air–sea carbon fluxes WG
      • Fish Carbon WG
      • Meta-eukomics WG
      • mCDR
      • Metaproteomic Intercomparison
      • Mixotrophs & Mixotrophy WG
      • N-Fixation WG
      • Ocean Carbonate System Intercomparison Forum
      • Ocean Carbon Uptake WG
      • OOI BGC sensor WG
      • Operational Phytoplankton Observations WG
      • Phytoplankton Taxonomy WG
    • Other Workshops
    • Science Planning
      • Coastal CARbon Synthesis (CCARS)
      • North Atlantic-Arctic
    • Ocean Acidification PI Meetings
    • Training Activities
      • PACE Hackweek 2025
      • PACE Hackweek 2024
      • PACE Training Activity 2022
  • 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
      • Guidelines for OCB Workshops & Activities
    • Travel Support
  • Publications
    • OCB Workshop Reports
    • Science Planning and Policy
    • Newsletter Archive
  • Science Highlights
  • News

Archive for New OCB Research – Page 21

Efficient carbon drawdown allows for a high future carbon uptake in the North Atlantic

Posted by mmaheigan 
· Wednesday, November 7th, 2018 

As one of the major carbon sinks in the global ocean, the North Atlantic is a key player in mediating and ameliorating the ongoing global warming. Current projections of the North Atlantic carbon sink in a high-CO2 future vary greatly among models, with some showing that a slowdown in carbon uptake has already begun and others predicting that this slowdown will not occur until nearly 2100. To ensure the credibility of future projections as needed for finding adequate mitigation strategies, it is important to address and reduce this uncertainty.

Percentage of anthropogenically altered carbon stored in the deep North Atlantic (left panel) and North Atlantic uptake of anthropogenically altered carbon (right panel) as simulated by 11 different Earth System Models for a high CO2-future. Black x and line in left panel mark the observational estimate and its uncertainties, while blue and red shading reflect model spread, including models that simulate deep ocean storage within (blue) and outside (red) these observational uncertainties.

A new study in the Journal of Climate identified some of the mechanisms behind this ambiguity by analyzing the output of 11 Earth System Models for a high-CO2 future. The authors show that discrepancies among models largely originate around high-latitude gateways from the surface to the deep ocean. Through biological production, deep convection and subsequent transport via the deep western boundary current, these gateways remove carbon from the upper ocean. When enough carbon is removed to maintain a lower oceanic pCO2 relative to atmospheric pCO2, the ocean continues to take up carbon. The study reveals that the fraction of anthropogenic carbon that is stored below 1000 m depth is not only an indicator of current carbon removal from the upper ocean but also a predictor of future ocean carbon uptake. When models that lie outside the range of observational uncertainties in deep carbon storage (red shading, left panel of figure) were excluded, revised projections showed higher North Atlantic carbon uptake in the future with lower associated uncertainties (blue shading, right panel of figure). This result highlights the need to depart from the concept of more or less randomly chosen models when reporting on future projections and their uncertainties. Results that are more reliable and hence of better use for mitigation strategies can be gained by focusing solely on models that simulate key mechanisms within observational uncertainties.

 

Authors:
N. Goris (Bjerknes Centre for Climate Research, Norway)
J.F. Tjiputra (Bjerknes Centre for Climate Research, Norway)
A. Olsen (University of Bergen and Bjerknes Centre for Climate Research, Norway)
J. Schwinger (Bjerknes Centre for Climate Research, Norway)
S.K. Lauvset (Bjerknes Centre for Climate Research, Norway)
E. Jeansson (Bjerknes Centre for Climate Research, Norway)

Investigating variability and change in subpolar Southern Ocean pCO2 via time-series and float data

Posted by mmaheigan 
· Tuesday, November 6th, 2018 

The Southern Ocean dominates the mean global ocean sink for anthropogenic carbon, but its sparse sampling relative to other basins limits our capacity to quantify carbon uptake and accompanying seasonal to interannual variability, which is critical to predicting future ocean carbon uptake and storage. Since 2002, underway pCO2 measurements collected as part of the Drake Passage Time-series (DPT) Program have informed our understanding of seasonally varying air-sea pCO2 gradients and by inference, the carbon fluxes in this region. Understanding whether Drake Passage air-sea fluxes are representative of the broader subpolar Southern Ocean was the focus of a recent study in Biogeosciences.

Top left panel: Mean surface ocean seasonal pCO2 cycle estimate for datasets from the Surface Ocean CO2 Atlas (SOCAT) in the subpolar Southern Ocean: black- SOCAT within the Drake Passage (DP) region; green- SOCAT outside the DP region; blue- all SOCAT in Southern Ocean Subpolar Seasonally Stratified (SPSS) biome; red- Self Organizing Map Feed-forward Network (SOM-FFN) product. Shading represents 1 standard error for biome-scale monthly means driven by interannual variability. Bar plot indicates the number of years containing observations in a given month (maximum of 15 years).
Top right panel: Mean surface ocean pCO2 seasonal cycle estimate for black: underway Drake Passage Time-series data for years 2002–2016; purple: DPT for years 2016–2017 to match years covered by the floats; and orange: SOCCOM floats. Seasonal cycles are shown on an 18-month cycle, calculated from a monthly mean time series with the atmospheric correction to year 2017. Shading represents 1 standard error accounting for the spatial and temporal heterogeneity of the sample and the measurement error (2.7 % or ±11 µatm at a pCO2 of 400 µatm for floats; ±2 µatm for DPT data) combined using the square root of the sum of squares.

An analysis of available Southern Ocean pCO2 data from inside vs. outside the Drake Passage showed agreement in the timing and amplitude of seasonal pCO2 variations, suggesting that the seasonality so carefully recorded by DPT is in fact representative of the broader subpolar Southern Ocean. DPT’s high temporal resolution sampling is critical to constraining estimates of the seasonal cycle of surface pCO2 in this region, as wintertime underway pCO2 data remain sparse outside the Drake Passage. Comparisons of the DPT data to an emerging dataset of float-estimated pCO2 from the SOCCOM (Southern Ocean Carbon and Climate Observations and Modeling) project showed that both shipboard and autonomous platforms capture the expected seasonal cycle for the subpolar Southern Ocean, with an austral wintertime peak driven by deep mixing and a summertime low driven by biological uptake. However, the seasonal cycle derived from float-estimated pCO2 has a larger seasonal amplitude compared to the DPT data due to an earlier and much lower observed summertime minimum.

The Drake Passage Time-series illustrates the large variability of surface ocean pCO2 in the Southern Ocean and exemplifies the value of sustained observations for understanding changing ocean carbon uptake in this dynamic region. Coordinated monitoring efforts that combine a robust ship-based observational network with a well-calibrated array of autonomous biogeochemical floats will improve and expand our understanding of the Southern Ocean carbon cycle in the future.

Authors:
Amanda R. Fay (Lamont Doherty Earth Observatory)
Nicole S. Lovenduski (University of Colorado)
Galen A. McKinley (Lamont Doherty Earth Observatory)
David R. Munro (University of Colorado)
Colm Sweeney (University of Colorado, NOAA Earth System Research Laboratory)
Alison R. Gray (University of Washington)
Peter Landschützer (Max Planck Institute for Meteorology, Germany)
Britton B. Stephens (National Center for Atmospheric Research)
Taro Takahashi (Lamont Doherty Earth Observatory)
Nancy Williams (Oregon State University)

Dramatic Increase in Chlorophyll-a Concentrations in Response to Spring Asian Dust Events in the Western North Pacific

Posted by mmaheigan 
· Tuesday, October 23rd, 2018 

According to Martin’s iron hypothesis, input of aeolian dust into the ocean environment temporarily relieves iron limitation that suppresses primary productivity. Asian dust events that originate in the Taklimakan and Gobi Deserts occur primarily in the spring and represent the second largest global source of dust to the oceans. The western North Pacific, where productivity is co-limited by nitrogen and iron, is located directly downwind of these source regions and is therefore an ideal location for determining the response of open water primary productivity to these dust input events.

Figure 1. Daily aerosol index values (black squares) and chlorophyll-a concentrations (mg m-3, circles) during the spring (a) 2010 (weak dust event), (b) 1998 (strong dust event) in the western North Pacific. Color scale represents difference between mixed layer depth (MLD) and isolume depth (Z0.054) that indicates conditions for typical spring blooms; water column structures of MLD and isolume were identical in the spring of 1998 and 2010. Dramatic increases in chlorophyll-a (pink shading, maximum of 5.3 mg m-3) occurred in spring 1998 with a lag time of ~10 days after the strong dust event (aerosol index >2.5) on approximately April 20 compared to constant chlorophyll-a values (<2 mg m-3) in the spring of 2010.

A recent study in Geophysical Research Letters included an analysis of the spatial dynamics of spring Asian dust events, from the source regions to the western North Pacific, and their impacts on ocean primary productivity from 1998 to 2014 (except for 2002–2004) using long-term satellite observations (daily aerosol index data and chlorophyll-a). Geographical aerosol index distributions revealed three different transport pathways supported by the westerly wind system: 1) Dust moving predominantly over the Siberian continent (>50°N); 2) Dust passing across the northern East/Japan Sea (40°N‒50°N); and 3) Dust moving over the entire East/Japan Sea (35°N‒55°N). The authors observed that strong dust events could increase ocean primary productivity by more than 70% (>2-fold increase in chlorophyll-a concentrations, Figure 1) compared to weak/non-dust conditions. This result suggests that spring Asian dust events, though episodic, may play a significant role in driving the biological pump, thus sequestering atmospheric CO2 in the western North Pacific.

Another recent study reported that anthropogenic nitrogen deposition in the western North Pacific has significantly increased over the last three decades (i.e. relieving nitrogen limitation), whereas this study indicated a recent decreasing trend in the frequency of spring Asian dust events (i.e. enhancing iron limitation). Further investigation is required to fully understand the effects of contrasting behavior of iron (i.e., decreasing trend) and nitrogen (i.e., increasing trend) inputs on the ocean primary productivity in the western North Pacific, paying attention on how the marine ecosystem and biogeochemistry will respond to the changes.

 

Authors:
Joo-Eun Yoon (Incheon National University)
Il-Nam Kim (Incheon National University)
Alison M. Macdonald (Woods Hole Oceanographic Institution)

Shipboard LiDAR: A powerful tool for measuring the distribution and composition of particles in the ocean

Posted by mmaheigan 
· Tuesday, October 23rd, 2018 

Despite major advances in ocean observing capabilities, characterizing the vertical distribution of materials in the ocean with high spatial resolution remains challenging. Light Detection and Ranging (LiDAR), a technique that relies on measurement of the “time-of-flight” of a backscattered laser pulse to determine the range to a scattering object, could potentially fill this critical gap in our sampling capabilities by providing remote estimates of the vertical distribution of optical properties and suspended particles in the ocean.

A recent article in Remote Sensing of Environment details the development of a portable shipboard LiDAR and its capabilities for extending high-frequency measurements of scattering particles into the vertical dimension. The authors deployed the experimental system (shown in Figure 1a) during research cruises off the coast of Virginia and during a passenger ferry crossing of the Gulf of Maine (associated with the Gulf of Maine North Atlantic Time Series program-GNATS). Remote measurements of LiDAR signal attenuation corresponded well with simultaneous in situ measurements of water column optical properties and proxies for the concentration of suspended particles. Interestingly, the researchers also observed that the extent to which the return signal was depolarized (also known as the LiDAR depolarization ratio) may provide information regarding the composition of particles within the scattering volume. This is evidenced by the strong relationship between the depolarization ratio and the backscattering ratio, an indicator of the bulk composition (mineral vs. organic) of the particles within a scattering medium (Figure 1b).

Figure 1. a) LiDAR system deployed to look through a chock at the bow of the M/V Nova Star. b) Relationship between the LiDAR linear depolarization ratio (ρ) and coincident measurements of the particulate backscattering ratio (bbp/bp). The black line represents a least-squares exponential fit to the data.

As LiDAR technology becomes increasingly rugged, compact, and inexpensive, the regular deployment of oceanographic LiDAR on a variety of sampling platforms will become an increasingly practical method for characterizing the vertical and horizontal distribution of particles in the ocean. This has the potential to greatly improve our ability to investigate the role of particles in physical and biogeochemical oceanographic processes, especially when sampling constraints limit observations to the surface ocean.

 

Authors:
Brian L. Collister (Old Dominion University)
Richard C. Zimmerman (Old Dominion University)
Charles I. Sukenik (Old Dominion University
Victoria J. Hill (Old Dominion University)
William M. Balch (Bigelow Laboratory for Ocean Sciences)

When marine-terminating glaciers ‘pump’ the ocean

Posted by mmaheigan 
· Wednesday, October 10th, 2018 

How will increasing meltwater from Greenland affect the biogeochemistry of the ocean? Release of meltwater into the ocean has physical and biogeochemical effects on the local water column. With respect to nutrient availability, meltwater supplies the bioessential nutrients iron and silicic acid but is deficient in nitrate and phosphate. However, despite very low meltwater nitrate and phosphate concentrations, pronounced summertime phytoplankton blooms are observed in many, though not all, of Greenland’s large fjord systems. These unusual summertime blooms are associated with meltwater from marine-terminating glaciers. So if the meltwater itself is not supplying nitrate and phosphate that these blooms require, what is the source of the nutrients that support these blooms?

An illustration of how changing the depth of a glacier affects downstream productivity

A recent study published in Nature Communications shows that when meltwater is released below sea level under large marine-terminating glaciers, it rises rapidly towards the surface in buoyant discharge plumes. As these plumes rise, they entrain large quantities of deep, nutrient-rich seawater. This vertical transport, or ‘pumping’, of these nutrients to the surface sustains unusually high summertime productivity in Greenland’s fjords. Conversely, when meltwater is released at the ocean surface, primary production is reduced because the meltwater itself lacks the nitrate and phosphate required to fuel phytoplankton blooms. Consequently, the inland retreat of Greenland’s large marine-terminating glaciers is ultimately bad news for summertime marine phytoplankton communities. As the depth of the marine-terminating glaciers shoals, their associated nutrient ‘pumps’ collapse, which will likely have negative effects on primary production and associated inshore fisheries.

 

Authors:
M.J. Hopwood (GEOMAR)
D. Carroll (Jet Propulsion Laboratory)
T.J. Browning (GEOMAR)
L. Meire (Royal Netherlands Institute for Sea Research and Greenland Climate Research Centre)
J. Mortensen (Greenland Climate Research Centre)
S. Krisch (GEOMAR)
E.P. Achterberg (GEOMAR)

Primary productivity à la mode

Posted by mmaheigan 
· Wednesday, October 10th, 2018 

The presence of large-scale Ekman downwelling is the textbook explanation for low nutrient concentrations, and hence low productivity, in subtropical gyres. However, recent research has suggested that mesoscale eddies oppose and substantially reduce this downwelling, a process known as eddy cancellation (Doddridge et al, 2016). Eddy cancellation represents a substantial alteration to the widely accepted notion of large-scale Ekman downwelling in subtropical gyres, and motivates our study of the processes that determine nutrient concentration within subtropical gyres.

Figure 1: Sensitivity experiments for mode water thickness (hmode) with two values of residual Ekman pumping. a) With no residual Ekman pumping, phosphate concentration responds strongly to mode water thickness. b) When Ekman pumping is strong, phosphate concentration does not depend on mode water thickness. The dashed lines represent transects of climatological phosphate concentration in the euphotic zone of the North Atlantic subtropical gyre (Garcia et al., 2013).

A recent paper published in the Journal of Geophysical Research: Oceans and featured in an MIT News article describes an idealized model for nutrient concentration in subtropical gyres that can account for this reduction in Ekman pumping. The model predicts that surface productivity is sensitive to the thickness of the underlying subtropical mode water layer, provided that the residual Ekman pumping is small (Figure 1). Comparison of this prediction with observations from the Bermuda Atlantic Time series Study (BATS) shows that surface productivity increases as the thickness of the underlying mode water increases (Figure 2), as predicted by the idealized model in the absence of substantial Ekman pumping.

Figure 2: Annually averaged primary productivity and mode water thickness from the BATS dataset. The linear fit between mode water thickness and primary productivity is statistically significant (p ≈ 0.027) and explains 19.5% of the variance in primary productivity.

The observed relationship between productivity and mode water thickness at BATS is consistent with a small residual Ekman pumping, indicating highly effective eddy cancellation in the subtropical North Atlantic. Previous research (Palter et al., 2005) has suggested that as the subtropical mode water layer thickens, it blocks nutrient entrainment from below, resulting in lower productivity in the euphotic zone. However, this study suggests that a thicker subtropical mode water layer actually increases the surface nutrient concentrations by promoting more effective recycling of nutrients within the gyre. With a thicker mode water layer, more of the nutrients in the particulate flux are remineralized before they pass through the thermocline and become isolated from the surface ocean. This means that a thicker mode water layer leads to higher nutrient concentrations and supports primary productivity in subtropical gyres. This represents a fundamental change in our understanding of how nutrients are supplied to the surface waters of subtropical gyres.

Authors:
Edward Doddridge (Department of Earth, Atmospheric and Planetary Sciences, MIT)
David Marshall (Atmospheric, Oceanic & Planetary Physics, University of Oxford)

See the Eos spotlight on this research

Improved method to identify and reduce uncertainties in marine carbon cycle predictions

Posted by mmaheigan 
· Wednesday, September 26th, 2018 

Improved method to identify and reduce uncertainties in marine carbon cycle predictions

How well do contemporary Earth System Models (ESMs) represent the dynamics of the modern day ocean? Often we question the fidelity of biological and chemical processes represented in these ESMs. The fact is representations of biogeochemical processes in models are plagued with some degree of uncertainties; therefore, identifying and reducing such deficiencies could advance ESM development and improve model predictions.

An overview of several models with respect to each of the variables, using absolute (left) and relative (right) scores to determine the degree of uncertainty in relation to referenced datasets.

 

A recent publication in Atmosphere described the ongoing efforts to develop the International Ocean Model Benchmarking (IOMB) package to evaluate ESM skill sets in simulating marine biogeochemical variables and processes. Model performances were scored based on how well they captured the distribution and variability contained in high-quality observational datasets. The authors highlighted systematic model–data benchmarking as a technique to identify ocean model deficiencies, which could provide a pathway to improving representations of sub-grid-scale parameterizations. They have scaled the absolute score from zero to unity, where the red color tends toward zero to quantify weaknesses in the skill set of a particular model in capturing values from the observational datasets. On the other side of the spectrum, the green color signifies considerable temporal and spatial overlap between the predicted and the observational values. The authors also present the standard score to show the relative scores within two standard deviations from the model mean. The benchmarking package was employed in the published study to assess marine biogeochemical process representations, with a focus on surface ocean concentrations and sea–air fluxes of dimethylsulfide (DMS). The production and emission of natural aerosols remain one of the major limitations in estimating global radiative forcing. Appropriate representation of aerosols in the marine boundary layer (MBL) is essential to reduce uncertainty and provide reliable information on offsets to global warming. Results show that model–data biases increased as DMS enters the MBL, with models over-predicting sea surface concentrations in the productive region of the eastern tropical Pacific by almost a factor of two and the sea–air fluxes by a factor of three. The associated uncertainties with oceanic carbon cycle processes may be additive or antagonistic; in any case, a constructive effort to disentangle the subtleties begins with an objective benchmarking effort, which is focused specifically on marine biogeochemical processes. The tool in development will ensure we satisfy some of the Model Intercomparison Project (MIP) benchmarking needs for the sixth phase of Coupled Model Intercomparison Project (CMIP6).

 

Authors:
Oluwaseun Ogunro (ORNL)
Scott Elliott (LANL)
Oliver Wingenter (New Mexico Tech)
Clara Deal (University of Alaska)
Weiwei Fu (UC Irvine)
Nathan Collier (ORNL)
Forrest M. Hoffman (ORNL)

Physics shed new light on microbial filter-feeding

Posted by mmaheigan 
· Wednesday, September 26th, 2018 

Microbial filter-feeders actively filter water for bacteria-sized prey, but hydrodynamic theory predicts that their filtration rate should be one order of magnitude lower than what they realize.   What is missing in our knowledge and modeling of these key components of aquatic food webs?

In a recent study published in PNAS, Nielsen et al. (2017) used a combination of microscopy observations, particle tracking, and analytical and computational fluid dynamics (CFD) to shed light on the physics of microbial filter-feeding. They found that analytical and computational fluid dynamic estimates agree that the observed filtration rate cannot be realized given the known morphology and flagellum kinematics. The estimates consistently fall one order of magnitude short of observed filtration rates. This led the authors to suggest that their study organism, the choanoflagellate Diaphanoeca grandis, has a so-called ‘flagellar vane’, a sheet-like extension of the flagellum seen in some members of the choanoflagellate sister group, the marine sponges. This structure would fundamentally change the physics of the filtration process, and the authors found that both the analytical and the computational estimates match observed filtration rates when such a structure is included.

Left: Choanoflagellate model morphology showing the protoplast (cell) in orange, the filter comprised of microvilli (black), the lorica and chimney (red) and the flagellum with vane (blue). Right: Experimentally observed near-cell flow field vs. flow field modelled using computational fluid dynamics including a flagellar vane. The filter cross-section is here shown in green. The modelled flow field provides a good match with the observed flow field. Without a flagellar vane, the model flow field is at least an order of magnitude weaker. This leads to the suggestion that a flagellar vane is needed to account for the observed flow field and clearance rate.

 

The new insights allow the authors to generalize about the trade-offs involved in microbial filtering, which is important to our understanding of the microbial loop in planktonic food webs. The results are of even wider interest since choanoflagellates are believed to be the evolutionary ancestors of all multicellular animals, many of which include cells that are fundamentally identical to choanoflagellates (e.g., the simple cuboidal epithelium cells of kidneys). Thus, microscale filtering not only happens in every single drop of seawater, it also happens inside most animals.

Learn more here.

Authors:
Lasse Tor Nielsen (National Institute of Aquatic Resources and Centre for Ocean Life, Technical University of Denmark)
Seyed Saeed Asadzadeh (Department of Mechanical Engineering, Technical University of Denmark)
Julia Dölger (Department of Physics and Centre for Ocean Life, Technical University of Denmark)
Jens H. Walther (Department of Mechanical Engineering, Technical University of Denmark, Denmark and Swiss Federal Institute of Technology Zürich, ETH Zentrum)
Thomas Kiørboe (National Institute of Aquatic Resources and Centre for Ocean Life, Technical University of Denmark)
Anders Andersen (Department of Physics and Centre for Ocean Life, Technical University of Denmark)

When it comes to carbon export, the mesoscale matters

Posted by hbenway 
· Tuesday, September 11th, 2018 

Figure 1. Difference in annual mean carbon export (ΔPOC flux) between a high resolution (0.1º, Hi-res) and standard resolution (1º, Analog) global climate model simulation using the CESM model. Highlighted regions show areas where vertical (purple boxes) and horizontal (red boxes) changes in nutrient transport drive increases or decreases in export, respectively.

Most Earth System models (ESMs) that are used to study global climate and the carbon cycle do not resolve the most energetic scales in the ocean, the mesoscale (10-100 km), encompassing eddies, coastal jets, and other dynamic features strongly affecting nutrient delivery, productivity, and carbon export. This prompts the question: What are we missing in climate models by not resolving the mesoscale?

Authors of a recent study published in Global Biogeochemical Cycles conducted a comparative analysis of the importance of mesoscale features in biological production and associated carbon export using standard resolution (1°) and mesoscale-resolving (0.1°) ESM simulations. The mesoscale-resolving ESM yielded only a ~2% reduction in globally integrated export production relative to the standard resolution ESM. However, a closer look at the local processes driving export in different basins revealed much larger, compensating differences (Fig. 1). For example, in regions where biological production is driven by natural iron fertilization from shelf sediment sources (Fig. 2), improved representation of coastal jets in the higher-resolution ESM reduces the cross-shelf iron delivery that fuels production (red boxes in Fig. 1). Resolving mesoscale turbulence further reduces the spatial extent of blooms and associated export, yielding a more patchy distribution than in the coarse resolution models. Together, these processes lead to a reduction in export in the Argentine Basin, one of the most productive regions on the planet, of locally up to 50%. In contrast, resolving the mesoscale results in enhanced export production in the Subantarctic (purple box in Fig. 1), where the mesoscale model resolves deeper, narrower mixed layer depths that support stronger nutrient entrainment, in turn enhancing local productivity and export.

Figure 2. An iron-driven plankton bloom structured by mesoscale features in the South Atlantic. Left is simulated dissolved iron (Fe), the limiting nutrient for this region, and right is iron in all phytoplankton classes, a proxy for biomass (phytoFe, shown in log10 scale), on January 11, the height of the bloom. Plankton blooms in the Subantarctic Atlantic are fueled by horizontal iron transport off coastal and island shelves and vertical injection from seamounts, whereas farther south in the Southern Ocean, winter vertical mixing is the primary driver of iron delivery. Mesoscale circulation, largely an unstructured mix of interacting jets and vortices, strongly affects the location and timing of carbon production and export. Click here for an animation.

In regions with very short productivity seasons like the North Pacific and Subantarctic, internally generated mesoscale variability (captured in the higher resolution ESM) yields significant interannual variation in local carbon export. In these regions, a few eddies, filaments or more amorphous mesoscale features can structure the entire production and export pattern for the short bloom season. These findings document the importance of resolving mesoscale features in ESMs to more accurately quantify carbon export, and the different roles mesoscale variability can play in different oceanographic settings.

Determining how to best sample these mesoscale turbulence-dominated blooms and scale up these measurements to regional and longer time means, is an outstanding joint challenge for modelers and observationalists. A key piece is obtaining the high temporal and spatial resolution data sets needed for validating modeled carbon export in bloom regions strongly impacted by mesoscale dynamics, which represent a large portion of the global carbon export.

Authors
Cheryl Harrison (NCAR, University of Colorado Boulder)
Matthew Long (NCAR)
Nicole Lovenduski (University of Colorado Boulder)
J. Keith Moore (University of California Irvine)

Elusive protists transport large quantities of silica into the ocean interior

Posted by hbenway 
· Friday, September 7th, 2018 

Phaeodaria are single-celled eukaryotes (a.k.a. protists) belonging to the supergroup Rhizaria. Like diatoms, phaeodarians build up skeletons made of opaline silica, but unlike their emblematic relatives, phaeodarians have been largely ignored in the marine silica cycle.

The contribution of phaeodarians to total biogenic silica (bSiO2) export is markedly enhanced at low total bSiO2 export (analysis did not include data from 2014 due to abnormally depleted phaeodarian population).

In a recent study published in Global Biogeochemical Cycles (also see related Research Spotlight in AGU Eos), authors used a combination of extensive sediment trap deployments and in situ imagery during four cruises of the California Current Ecosystem Long-Term Ecological Research (CCE-LTER) Program off the coast of California to quantify biogenic silica export mediated by giant phaeodarians (>600 µm). These data revealed that giant phaeodarians possess among the highest recorded cellular silica content (up to 43 µg Si cell-1). In addition, measurements of vertical fluxes suggest that these organisms can play a surprisingly large role in silica export (ranging from 10-80% of total silica export) in more oligotrophic waters. Also, because they are most abundant in waters below the euphotic zone, phaeodarians contribute to increased biogenic silica flux in the mesopelagic, in contrast with typically observed decreases in carbon flux with depth. Given their significant contribution to silica export, phaeodarians should be considered in global budgets and models of ocean silica cycles, especially in oligotrophic waters.

Authors
Tristan Biard (Scripps Institution of Oceanography)
Jeffrey W. Krause (University of Southern Alabama)
Michael R. Stukel (Florida State University)
Mark D. Ohman (Scripps Institution of Oceanography)

« Previous Page
Next Page »

Filter by Keyword

abundance acidification additionality advection africa air-sea air-sea interactions algae alkalinity allometry ammonium AMO AMOC anoxic Antarctic Antarctica anthro impacts anthropogenic carbon anthropogenic impacts appendicularia aquaculture aquatic continuum aragonite saturation arctic Argo argon arsenic artificial seawater AT Atlantic atmospheric CO2 atmospheric nitrogen deposition authigenic carbonates autonomous platforms AUVs bacteria bathypelagic BATS BCG Argo benthic bgc argo bio-go-ship bio-optical bioavailability biogeochemical cycles biogeochemical models biogeochemistry Biological Essential Ocean Variables biological pump biophysics bloom blue carbon bottom water boundary layer buffer capacity C14 CaCO3 calcification calcite carbon carbon-climate feedback carbon-sulfur coupling carbonate carbonate system carbon budget carbon cycle carbon dioxide carbon export carbon fluxes carbon sequestration carbon storage Caribbean CCA CCS changing marine chemistry changing marine ecosystems changing marine environments changing ocean chemistry chemical oceanographic data chemical speciation chemoautotroph chesapeake bay chl a chlorophyll circulation clouds CO2 CO3 coastal and estuarine coastal darkening coastal ocean cobalt Coccolithophores commercial community composition competition conservation cooling effect copepod copepods coral reefs CTD currents cyclone daily cycles data data access data assimilation database data management data product Data standards DCM dead zone decadal trends decomposers decomposition deep convection deep ocean deep sea coral denitrification deoxygenation depth diatoms DIC diel migration diffusion dimethylsulfide dinoflagellate dinoflagellates discrete measurements distribution DOC DOM domoic acid DOP dust DVM ecology economics ecosystem management ecosystems eddy Education EEZ Ekman transport emissions ENSO enzyme equatorial current equatorial regions ESM estuarine and coastal carbon fluxes estuary euphotic zone eutrophication evolution export export fluxes export production extreme events faecal pellets fecal pellets filter feeders filtration rates fire fish Fish carbon fisheries fishing floats fluid dynamics fluorescence food webs forage fish forams freshening freshwater frontal zone functional role future oceans gelatinous zooplankton geochemistry geoengineering geologic time GEOTRACES glaciers gliders global carbon budget global ocean global warming go-ship grazing greenhouse gas greenhouse gases Greenland ground truthing groundwater Gulf of Maine Gulf of Mexico Gulf Stream gyre harmful algal bloom high latitude human food human impact human well-being hurricane hydrogen hydrothermal hypoxia ice age ice cores ice cover industrial onset inland waters in situ inverse circulation ions iron iron fertilization iron limitation isotopes jellies katabatic winds kelvin waves krill kuroshio lab vs field land-ocean continuum larvaceans lateral transport LGM lidar ligands light light attenuation lipids low nutrient machine learning mangroves marine carbon cycle marine heatwave marine particles marine snowfall marshes mCDR mechanisms Mediterranean meltwater mesopelagic mesoscale mesoscale processes metagenome metals methane methods microbes microlayer microorganisms microplankton microscale microzooplankton midwater mitigation mixed layer mixed layers mixing mixotrophs mixotrophy model modeling model validation mode water molecular diffusion MPT MRV multi-decade n2o NAAMES NCP nearshore net community production net primary productivity new ocean state new technology Niskin bottle nitrate nitrogen nitrogen cycle nitrogen fixation nitrous oxide north atlantic north pacific North Sea NPP nuclear war nutricline nutrient budget nutrient cycles nutrient cycling nutrient limitation nutrients OA observations ocean-atmosphere ocean acidification ocean acidification data ocean alkalinity enhancement ocean carbon storage and uptake ocean carbon uptake and storage ocean color ocean modeling ocean observatories ocean warming ODZ oligotrophic omics OMZ open ocean optics organic particles oscillation outwelling overturning circulation oxygen pacific paleoceanography PAR parameter optimization parasite particle flux particles partnerships pCO2 PDO peat pelagic PETM pH phenology phosphate phosphorus photosynthesis physical processes physiology phytoplankton PIC piezophilic piezotolerant plankton POC polar polar regions policy pollutants precipitation predation predator-prey prediction pressure primary productivity Prochlorococcus productivity prokaryotes 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 satellite scale seafloor seagrass sea ice sea level rise seasonal seasonality seasonal patterns seasonal trends sea spray seawater collection seaweed secchi sediments sensors sequestration shelf ocean shelf system shells ship-based observations shorelines siderophore silica silicate silicon cycle sinking sinking particles size SOCCOM soil carbon southern ocean south pacific spatial covariations speciation SST state estimation stoichiometry subduction submesoscale subpolar subtropical sulfate surf surface surface ocean Synechococcus technology teleconnections temperate temperature temporal covariations thermocline thermodynamics thermohaline thorium tidal time-series time of emergence titration top predators total alkalinity trace elements trace metals trait-based transfer efficiency transient features trawling Tris trophic transfer tropical turbulence twilight zone upper ocean upper water column upwelling US CLIVAR validation velocity gradient ventilation vertical flux vertical migration vertical transport warming water clarity water mass water quality waves weathering western boundary currents wetlands winter mixing zooplankton

Copyright © 2025 - 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.