The Regional Cabled Array (RCA) operation and management cruise, funded by the National Science Foundation as part of the Ocean Observatories Initiative, will take place July 31- September 1, 2020 onboard the R/V Thomas G. Thompson, operated by the University of Washington. All of the Cabled Array instruments that are being replaced during the cruise will be deactivated on 01 August to avoid calibration mismatches as the in-water instruments are unplugged and new ones plugged in. The newly deployed instruments will be turned back on as soon as possible after each leg of the cruise, with 01 September being the absolute latest that they come back online. Once they have been reactivated, the data will backfill with the appropriate serial numbers and calibration info to repopulate the gap.

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Global carbon dioxide (CO2) concentrations are increasing in the atmosphere, largely due to the use of fossil fuels. The oceans are absorbing about 25-30 percent of the atmospheric CO2, resulting in a shift in seawater acid-base chemistry and a decrease in ocean pH, making seawater more acidic. To help scientists assess this changing ocean chemistry, the Ocean Observatories Initiative (OOI) uses the Sunburst SAMI-CO2 instrument to measure the partial pressure of carbon dioxide (pCO2) from 150-700 microatmospheres (μatm) in the upper 200 meters of the water column.

The distribution of pCO2 in seawater is dependent on gas exchange with the atmosphere at the ocean surface, the breakdown of plant material by microbial processes, and removal by photosynthesis, calcium carbonate formation, and rising temperatures. Increases in pCO2 can also be caused by dissolution of calcium carbonate, which is of particular importance because calcium carbonate minerals are the building blocks for the skeletons and shells of many marine organisms, such as oysters.

Using the SAMI-CO2 instrument, OOI researchers determine the partial pressure of CO2 by equilibrating a pH sensitive indicator solution (Bromothymol Blue) to sampled seawater. Aqueous carbon dioxide in seawater diffuses across a permeable silicone membrane equilibrator within the instrument, which changes the color of the indicator solution from blue to yellow. The equilibrated indicator solution is then pumped through a chamber where light passes through the liquid and into a receptor that uses the wavelength to determine the amount of color change, and thus the amount of CO2 dissolved in the water.

“The OOI system parses the raw data from the instrument, applies a ‘blank’ value to correct for instrument drift, and then delivers calibrated pCO2 data to users on demand,” explained Michael Vardaro, OOI Research Scientist at the University of Washington. “We recently created a fix to apply the correct ’blank’ values to the pCO2 data to improve data accessibility and data quality.”

Blank values (e.g., optical absorbance ratios in the pco2w_b_sami_data_record_cal data stream) are used to calculate the data product “pCO2 Seawater (µatm)” at a specific timestamp. Blank values, however, are recorded intermittently to correct for drift of the electro-optical system, about once a week, which is a longer interval than the instrument sampling rate of one sample per hour.

The recent correction will ensure that any pCO2 data request will use a linearly interpolated value from the closest blanks if no blank value is found within the requested time range. This means that for an hourly pCO2 measurement that falls between weekly blank values the system will calculate the appropriate drift correction to apply based on the surrounding blank values, instead of trying to find a specific blank value that might be outside the date range of the requested data. In addition to improving data quality, this fix prevents the system from returning fill values or empty datasets. Additional restrictions were put on data delivery to prevent interpolation across deployments, which could pull blanks from different instrument serial numbers, potentially creating bad data. These fixes apply to all OOI pCO2 data.  Users who have pCO2 data products generated prior to 4 February 2020 are encouraged to re-request their data to ensure that the correct interpolation code is applied.

Any questions about this data fix, or any other OOI data issues, should be directed to help@oceanobservatories.org.

 

 

 

Images

Top: Alex Andronikides, a VISIONS’17 student from Queens College, New York helps clean a Regional Cabled Observatory Shallow Profiler Mooring science pod that was installed off the Washington-Oregon coast. Credit: M. Elend, University of Washington, V17.

Bottom: Pre-deployment photo of a Sunburst SAMI-CO2 sensor attached to the Oregon Offshore Cabled Shallow Profiler pod, which moves up and down in the water column between 200 meters and near the surface off the coast of Newport, OR. Credit: M. Elend, University of Washington, V19.

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Given the significant importance of understanding and modeling levels of carbon dioxide in our atmosphere (and its potential sources and sinks), Ocean-Atmosphere Exchange and Global Biogeochemistry and Carbon Cycling are two of the OOI’s primary science themes. We address these themes in part through measurements of the air and surface water partial pressure of carbon dioxide (pCO2).  Chris Wingard, the OOI Endurance Array Data Lead, recently completed an in-depth assessment of pCO2 data returned during the first four years of Endurance Array operations. These measurements were made using the Pro-Oceanus CO2-ProTM Atmosphere pCO2 sensor. By measuring the partial pressure of CO2 gas in both the air and surface water, researchers can estimate estimate surface flux of CO2 using data from this instrument. 

Wingard developed a protocol based on cross-comparisons of overlapping deployments of this sensor, comparing these with independent shipboard pCO2 measurements (including CTD samples and samples taken underway using flow-thru systems), and externally sourced air and surface water pCO2 measurements (e.g. from the LDEO Underway Database).  This array of sampling techniques served to confirm the quality and scientific applicability of the Endurance Array pCO2 measurements.

He reported the results of this assessment at a poster session at the recent Ocean Sciences 2020 meeting held this past February in San Diego, CA. The protocol is largely applicable to the same suite of measurements made using the Pro-Oceanus sensor on moorings deployed in the OOI Pioneer, Irminger Sea, Southern Ocean, and Argentine Basin Global Arrays. The MATLAB code and data used to download, process, merge, and cross-compare the data used in this assessment are available online for use.

Both the air and surface water measurements and the flux estimates used in this assessment are available through the OOI Data Portal. Endurance Array air and surface water pCO2 measurements are made at four locations distributed across the Oregon and Washington shelf and slope within the northern California Current Marine Ecosystem.

Other sources of Endurance Array-specific data include the most recent 60 days of the Endurance Array’s air and surface water pCO2 data are available on the NANOOS Visualization System (NVS) and the Global Ocean Acidification Observing System Data Portal (GOA-ON).

Figure 1: Surface water () and air pCO2 (, observed and , array average) measurements from 2015-04-01 through 2019-12-31 for the four moorings. The plots also show the distribution of discrete sample (*) and LDEO V2018 (O) data that coincide with each mooring. The data plotted have had human-in-the-loop (HITL) QC flags applied to remove points marked as suspect or failed. Beyond smoothing the data records and the estimation of an array averaged air pCO2 (), no further corrections were applied to the data. Note the high degree of variability during the summer months in the surface water pCO2 measurements for CE02SHSM, which are similar to other observations made on the Oregon Shelf (Evans et al., 2011).

Figure 2: Focused view (upper panel) of the Spring 2017 deployment (#5) of CE02SHSM showing the observed offsets between the surface water pCO2 measurements () and the discrete samples (*) and LDEO V2018 (O). Detailed views in the lower two panels, provide a better picture of the observed offsets during the periods of over-lapping deployments; between deployments 4 and 5 (lower left) and deployments 5 and 6 (lower right). Prior to using the OOI pCO2A data, users are strongly encouraged to conduct such cross-comparisons. The independent measurements obtained by the separate systems, and the close agreement between them, provide measures of confidence in the accuracy and applicability of the data.

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[video width="670" height="384" m4v="/wp-content/uploads/2020/04/OOI-F6.mp4"][/video]

OOI data team members have  developed a new toolbox for downloading data from the Machine-to-Machine (M2M) interface using MATLAB, making data access as easy as 1, 2, 3. The work expands on the existing tools available on OOI. This new toolbox covers data from moorings, gliders, and profilers in the OOI Coastal Arrays and can easily be extended to other research platforms. A video tutorial on how to use this new tool is provided above. (A pdf of the tutorial is provided below).

In three short steps – define the mooring, node, and instrument – users can easily and quickly access relevant OOI data. “This new approach eliminates some steps and makes it easy for anyone to find and access data they are looking for, “said Jonathan Fram, OOI Endurance Array Project Manager at Oregon State University (OSU). “We found this new approach really streamlined data access using the M2M interface and we are certain other OOI data users will find it similarly helpful.”

Developed by OOI OSU team members, Craig Risien and Russ Desiderio, these new tools are part of our ongoing effort to simplify access to OOI data to encourage its broader integration into scientific research and classroom content. A tutorial showing how to use MATLAB to access OOI data can be viewed here.

Other members of the OOI OSU team, Chris Wingard and Ian Black, are testing Python and R tools to explore OOI data, as well. Once the tools have been tested and vetted, they will be available along with other community-generated tools here.

This new tutorial adds to others that have been developed to help users integrate OOI data into their science.

OOI Video Tutorial PDF

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On Thursday, September 27th at 1938 PT, one of two chillers supporting power feed equipment at the Regional Cabled Array Shore Station had a fault which resulted in an automatic protective shutdown of the high voltage power supply and loss of power to both submarine cable lines. Power was restored to the system on Tuesday, October 2, 2018 at 1115 PT. Due to loss of power to the Cabled Array marine infrastructure, data were not collected by the instruments during this outage period.

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On Friday 8 December 2017 at 1:30 PM ET an error occurred that prevented the OOI Cyberinfrastructure (CI) system from loading new live data. On Monday 11 December 2017 the issue was fixed; no data were lost. We are sorry for any inconvenience.

If you have any questions, please contact the HelpDesk.

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