Archive for floats

Unexpected patterns of carbon export in the Southern Ocean

Posted by mmaheigan 
· Tuesday, July 7th, 2020 

The Southern Ocean is a major player in driving global distributions of heat, carbon dioxide, and nutrients, making it key to ocean chemistry and the earth’s climate system. In the ocean, biological production and export of organic carbon are commonly linked to places with high nutrient availability. A recent paper, published in Global Biogeochemical Cycles, highlighting new observations from robotic profiling floats demonstrates that areas of high carbon export in the Southern Ocean are actually associated with very low concentrations of iron, an important micronutrient for supporting phytoplankton growth. This suggests a decoupling between the production and export of organic carbon in this region.

Figure caption: (A) Meridional pattern of Annual Net Community Production (ANCP) (equivalent to carbon export) (± standard deviation) in the Southern Ocean (blue line with circles and shaded area), carbon export estimates from previous satellite-based analyses (blue dashed line), and silicate to nitrate (Si:NO3) ratio of the surface water (black continuous line). Grey dotted line shows a Si:NO3 = 1 mol mol−1, characteristic of nutrient-replete diatoms. (B) Meridional pattern of Southern Ocean nutrient concentrations, including dissolved iron (Fe) concentration (black line), nitrate (red line), and silicate (blue line). (C) Mean 2014–2015 annual zonally averaged air-sea flux of CO2 computed using neural network interpolation method. STF = Subtropical Front, PF = Antarctic Polar Front, SIF = Seasonal Ice Front.

Using observations of nutrient and oxygen drawdown from a regional network of profiling Biogeochemical-Argo floats deployed as part of the Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM), the authors calculated estimates of Southern Ocean carbon export. A meridional pattern in biological carbon export emerged, showing peak export near the Antarctic Polar Front (PF) associated with minima in surface iron concentrations and dissolved silicate to nitrate ratios. Previous studies have shown that under iron-limiting conditions, diatoms increase their uptake ratio of silicate with respect to other nutrients (e.g., nitrogen), resulting in silicification. Here, the authors hypothesize that iron limitation promotes silicification in Southern Ocean diatoms, as evidenced by the low silicate to nitrate ratio of surface waters around the Antarctic Polar Front. High diatom silicification increases ballasting of particulate organic carbon and hence overall carbon export in this region. The resulting meridional pattern of organic carbon export is similar to that of the air-sea flux of carbon dioxide in the Southern Ocean, underscoring the importance of the biological carbon pump in controlling the spatial pattern of oceanic carbon uptake in this region.

Authors:
Lionel A. Arteaga (Princeton University)
Markus Pahlow (Helmholtz Centre for Ocean Research Kiel, GEOMAR)
Seth M. Bushinsky (University of Hawaii)
Jorge L. Sarmiento (Princeton University)

 

Building ocean biogeochemistry observing capacity, one float at a time: An update on the Biogeochemical-Argo Program

Posted by mmaheigan 
· Thursday, July 5th, 2018 

By Ken Johnson (MBARI)

The Biogeochemical-Argo (BGC-Argo) Program is an international effort to develop a global network of biogeochemical sensors on Argo profiling floats that has emerged from over a decade of community discussion and planning. While there is no formal funding for this global program, it is being implemented via a series of international research projects that harness the unique capabilities provided by BGC profiling floats. The U.S. Ocean Carbon and Biogeochemistry (OCB) Program maintains and supports a U.S. BGC-Argo subcommittee as a focal point for U.S. community input on the implementation of the global biogeochemical float array and associated science program development.

Figure 1. Steve Riser deploying a SOCCOM float from the R/V Palmer

About BGC-Argo Floats
BGC-Argo floats can carry a suite of chemical and bio-optical sensors (Figure 1 – Float Schematic).  They have enough energy to make about 250 to 300 vertical profiles from 2000 m to the surface.  At a cycle time of 10 days, that corresponds to a lifetime near 7 years.  The long endurance allows the floats to resolve seasonal to interannual variations in carbon and nutrient cycling throughout the water column.  These time scales are difficult to study from ships and ocean interior processes are hard to resolve from satellites.  BGC profiling floats extend the capabilities of these traditional observing systems in significant ways.

Figure 2. Images of Navis and APEX floats used in the SOCCOM program. These floats carry oxygen, nitrate, pH, and bio-optical (chlorophyll fluorescence and backscatter) sensors.

All of the data from profiling floats operating as part of the Argo program must be available in real-time with no restrictions on access.  The Argo Global Data Assembly centers in France and the USA both provide complete listings of all BGC profiles (argo_bio-profile_index.txt) and access to the data.  Extensive documentation of the data processing protocols is available from the Argo Data Management Team.  Individual research programs, such as SOCCOM (see below), may also provide direct data access to the observed data along with value added products such as best estimates of pCO2 derived from pH sensor data.

Regional Deployments
In 2018, it is projected that 127 profiling floats with biogeochemical sensors are will be deployed, including ~40 floats by U.S. projects. Most of the U.S. deployments (30+) will be carried out by the Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project (Figure 2 – Float Deployment). These floats will carry oxygen, nitrate, pH, chlorophyll fluorescence, and backscatter sensors. As part of the NOAA Tropical Pacific Observing System (TPOS) program, Steve Riser’s group (Univ. Washington) will deploy 3 BGC-Argo floats per year in the equatorial Pacific over the next 4 years. These floats will be equipped with oxygen, pH, bio-optical sensors and Passive Acoustic Listener (PAL) sensors, which provide wind speed estimates at 15-minute intervals while the floats are parked at 1000 m.  Wind speed is derived from the noise spectrum of breaking waves. Steve Emerson (Univ. Washington), with NSF support, is also deploying floats equipped with oxygen, nitrate and pH sensors in the equatorial Pacific. With funding from NSF, Andrea Fassbender (MBARI) will deploy two floats at Ocean Station Papa in the northeast Pacific in collaboration with the EXPORTS program. These floats will also carry oxygen, nitrate, pH, and bio-optical sensors.

Nearly 90 BGC floats will be deployed in 2018 by other nations in multiple ocean basins.  Much of this effort will focus on the North Pacific and North Atlantic.  The sensor load on these floats is somewhat variable. Some will be deployed with only oxygen sensors or bio-optical sensors for chlorophyll fluorescence and particle abundance. Others will carry the full suite of six sensors (oxygen, nitrate, pH, chlorophyll fluorescence, backscatter, and irradiance) that are outlined in the BGC-Argo Implementation Plan (BGC-Argo, 2016). These floats will contribute to the existing array of 305 biogeochemical floats (Figure 3 BGC Argo Map).

Community Activities
In response to the tremendous interest in the scientific community in the capabilities of profiling floats, OCB is sponsoring a Biogeochemical Float Workshop at the University of Washington in Seattle from July 9-13, 2018 to begin the process of transferring this expertise to the broader oceanographic community, bringing together potential users of this technology to discuss biogeochemical profiling float technology, sensors, and data management and begin the process of the intelligent design of future scientific experiments. The workshop will provide participating scientists direct access to the facilities of the Float Laboratory operated by Riser. This workshop builds on a previous OCB workshop Observing Biogeochemical Cycles at Global Scales with Profiling Floats and Gliders (Johnson et al., 2009). BGC-Argo will also have a prominent presence at the 6th Argo Science Workshop (October 22-24, 2018, Tokyo, Japan) and OceanObs19 (September 16-20, 2019, Honolulu, HI).

Figure 3. May 2018 map of the location of BGC-Argo floats that have reported in the previous month and sensor types on these floats. From jcommops.org.

BGC-Argo Publications
Several resources now highlight the capabilities of profiling floats to accomplish scientific observing goals. A web-based bibliography of biogeochemical float papers hosted on the Biogeochemical-Argo website currently includes >100 publications and continues to grow. A special issue of Journal of Geophysical Research: Oceans focused on the SOCCOM program is in progress with 11 papers now available and a dozen more forthcoming. These papers include summaries of the technical capabilities of floats and the biogeochemical sensors, comparisons of float bio-optical data with satellite remote sensing observations, seasonal and interannual assessments of air-sea oxygen flux, under-ice biogeochemistry, carbon export, comparisons of pCO2 estimated from floats with pH vs. time-series data, and net community production. The connection of float observations with numerical models is a special focus of the program and this is highlighted in several papers, including a description of the Biogeochemical Southern Ocean State Estimate (SOSE), which is a data assimilating BGC model. Results from Observing System Simulation Experiments (OSSEs) used to assess the number of floats needed for large-scale observations are also reported. The BGC-Argo steering committee is developing a community white paper for the OceanObs19 conference in September 2019. BGC-Argo also develops and distributes a community newsletter.

For more information, visit the BGC-Argo website or reach out to the U.S. BGC-Argo Subcommittee.

 

 

 

 

Filter by Keyword

acidification air-sea interactions allometry AMOC anoxic Antarctic anthropogenic anthropogenic carbon aragonite saturation aragonite saturation state arctic argo Argo float arsenic Atlantic Atlantic modeling atmospheric CO2 atmospheric nitrogen deposition authigenic carbonates autonomous observing autonomous platforms bacteria BATS bcg-argo bioavailability biogeochemical cycles biogeochemical models biological pump biological uptake biophysics bloom blooms blue carbon bottom water boundary layer CaCO3 calcification calcite carbon-climate feedback carbon-sulfur coupling carbon cycle carbon dioxide carbon sequestration Caribbean CCS changing marine ecosystems changing ocean chemistry chemoautotroph chl a chlorophyll circulation climate change CO2 coastal ocean cobalt Coccolithophores community composition conservation cooling effect copepod coral reefs currents DCM decomposers decomposition deep convection deep ocean deep sea coral depth diagenesis diatoms DIC DIC vertical flux dimethylsulfide dissolved organic carbon dissolve inorganic carbon DOC domoic acid dust earth system models eddy Education Ekman transport emissions ENSO enzyme equatorial regions estuarine and coastal carbon fluxes estuary evolution EXPORTS extreme weather events faecal pellets filter feeders filtration rates fish Fish carbon fisheries floats fluid dynamics fluorescence food web food webs forams freshening frontal zone future oceans geochemistry geoengineering GEOTRACES glaciers gliders global carbon budget global ocean global warming go-ship greenhouse gas Greenland groundwater Gulf of Maine Gulf of Mexico Gulf Stream gyre harmful algal bloom high latitude human impact hydrothermal hypoxia ice age ice ages ice cores ice cover industrial onset iron iron fertilization isotopes jellies katabatic winds kelvin waves krill kuroshio land-ocean continuum larvaceans lateral transport lidar ligands mangroves marine food webs marine snowfall marshes meltwater mesopelagic mesoscale metagenome metals methane microbes microlayer microorganisms microscale microzooplankton midwater mixed layer mixotrophy modeling models mode water mode water formation molecular diffusion MPT multi-decade NASA net community production new technology nitrate nitrogen nitrogen fixation nitrous oxide north atlantic north pacific nutricline nutrient budget nutrient cycling nutrient flux nutrient limitation nutrients OA ocean-atmosphere ocean acidification ocean carbon uptake & storage ocean carbon uptake and storage ocean color ocean observatories ocean observing ODZ oligotrophic omics OMZ open ocean optics organic alkalinity organic particles overturning circulation oxygen pacific pacific ocean paleoceanography particle flux particulate organic carbon pCO2 PDO peat pelagic pH phenology phosphorus photosynthesis physical processes physics physiology phytoplankton plankton POC polar regions polar systems pollutants prediction primary production primary productivity productivity proteins pteropods radioisotopes remineralization remote sensing residence time resource management respiration river rivers Rossby waves Ross Sea ROV salinity salt marsh salt marshes satellite satellites scale seafloor seagrass sea ice sea level rise seasonal patterns seaweed sediment carbon sediments sensors shelf system ship-based observations silicate sinking particles size SOCCOM soil carbon sources and sinks southern ocean south pacific speciation species oscillations subduction submesoscale subpolar subtropical subtropical gyres subtropical mode water surface ocean surface water teleconnections temperate temperature thermohaline thorium tidal time-series time of emergence top predators total alkalinity trace element 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 mixing vertical transport vertical transport/flux volcano western boundary currents wetlands winter mixing zooplankton

Copyright © 2020 - 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.