A Case Study for Open Data Collaboration

Recognizing that freely accessible ocean observatory data has the potential to democratize interdisciplinary science for early career researchers, Levine et al. (2020) set out to demonstrate this capability using the Ocean Observatories Initiative.  Publicly available data from the OOI Pioneer Array moorings were used, and members of the OOI Early Career Scientist Community of Practice (OOI-ECS) collaborated in the study.

A case study was constructed to evaluate the impact of strong surface forcing events on surface and subsurface oceanographic conditions over the New England Shelf.  Data from meteorological sensors on the Pioneer surface moorings, along with data from interdisciplinary sensors on the Pioneer profiler moorings, were used.  Strong surface forcing was defined by anomalously low sea level pressure – less than three times the standard deviation of data from May 2015 – August 2018.  Twenty-eight events were identified in the full record.  Eight events in 2018 were selected for further analysis, and two of those were reported in the study (Figure 24).

[media-caption path="https://oceanobservatories.org/wp-content/uploads/2021/07/CGSN-Highlight.png" link="#"]Figure 24. Two surface forcing events (16 and 27 November) identified from the time series of surface forcing at the Pioneer Central surface mooring.  Vertical lines indicate the peak of the anomalous low-pressure events (gray), as well as times 48 h before (red) and after (blue).  (A) sea level pressure, (B) wind speed, (C) air temperature, (D) latent (solid) and sensible (dashed) heat fluxes, (E) sea surface temperature, and (F) surface current speed and direction. [/media-caption]

The impact of surface forcing on subsurface conditions was evaluated using profile data near local noon on the day of the event, as well as 48 hr before and after (Figure 24). Subsurface data revealed a shallow (40-60 m) salinity intrusion prior to the 16 November event, which dissipated during the event, presumably by vertical mixing and concurrent with increases in dissolved oxygen and decreases in colored dissolved organic matter (CDOM). At the onset of the 27 November event, nearly constant temperature, salinity, dissolved oxygen and CDOM to depths of 60 m were seen, suggesting strong vertical mixing.  Data from multiple moorings allowed the investigators to determine that the response to the first event was spatially variable, with indications of slope water of Gulf Stream origin impinging on the shelf. The response to the second event was more spatially-uniform, and was influenced by the advection of colder, fresher and more oxygenated water from the north.

The authors note that the case study shows the potential to address various interdisciplinary oceanographic processes, including across- and along- shelf dynamics, biochemical interactions, and air-sea interactions resulting from strong storms. They also note that long-term coastal datasets with multidisciplinary observations are relatively few, so that the Pioneer Array data allows hypothesis-driven research into topics such as the climatology of the shelfbreak region, seasonal variability of Gulf Stream meanders and warm-core rings, the influence of extreme events on shelf biogeochemical response, and the influence of a warming climate on shelf exchange.

In the context of the OOI-ECS, the authors note that the study was successfully completed using open-source data across institutional and geographic boundaries, within a resource-limited environment.  Interpretation of results required multiple subject matter experts in different disciplines, and the OOI-ECS was seen as well-suited to “team science” using an integrative, collaborative and interdisciplinary approach.

 

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Levine, RM, KE Fogaren, JE Rudzin, CJ Russoniello, DC Soule, and JM Whitaker (2020) Open Data, Collaborative Working Platforms, and Interdisciplinary Collaboration: Building an Early Career Scientist Community of Practice to Leverage Ocean Observatories Initiative Data to Address Critical Questions in Marine Science. Front. Mar. Sci. 7:593512. doi: 10.3389/fmars.2020.593512.

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Easing Sharing of Glider Data

The OOI’s Coastal and Global Array teams regularly use Teledyne-Webb Slocum Gliders to collect ocean observations within and around the array moorings. The gliders fly up and down the water column from the surface down to a maximum depth of 1000 meters, collecting data such as dissolved oxygen concentrations, temperature, salinity, and other physical parameters to measure ocean conditions.

OOI shares its glider data with the Integrated Ocean Observing System (IOOS) Glider Data Assembly Center (DAC). IOOS serves as a national repository for glider data sets, serving as a centralized location for wide distribution and use. It allows researchers to access and analyze glider data sets using common tools regardless of the glider type or organization that deployed the glider.

OOI serves data to these repositories in two ways.  When the gliders are in the water, data are telemetered, providing near real-time data to these platforms.  Once the gliders are recovered, data are downloaded, metadata provided, and data are resubmitted to the Glider DAC as a permanent record.

The behind-the-scene process transmitting this huge amount of data is quite complex. OOI Data Team members, Collin Dobson of the Coastal and Global Scale Nodes at Woods Hole Oceanographic Institution (WHOI) and Stuart Pearce of the Coastal Endurance Array at Oregon State University (OSU) teamed up to streamline the process and catch up on a backlog of submission of recovered data.

Pearce took the lead in getting the OOI data into the DAC. In 2018, he began writing code for a system to transmit near real-time and recovered data. Once the scripts (processing code) were operational by about mid-2019, Pearce implemented them to streamline the flow of Endurance Array glider data into the DAC. Dobson then adopted the code and applied it to the transmission of glider data from the Pioneer, Station Papa, and Irminger Sea Arrays into the repository.

As it turned out, timing was optimum. “ I finished my code at the same time that the Glider DAC allowed higher resolution recovered datasets to be uploaded,” said Pearce. “So I was able to adjust my code to accommodate the upload of any scientific variable as long as it had a CF compliant standard name to go with it.”  This opened up a whole range of data that could be transmitted in a consistent fashion to the DAC. CF refers to the “Climate and Forecast” metadata conventions that provide community accepted guidance for metadata variables and sets standards for designating time ranges and locations of data collection.  Dobson gave an example of the name convention for density:  Sea_water_density.

“Being CF compliant ensures your data have the required metadata and makes the data so much more usable across the board,” added Dobson.  “If I wanted to include oxygen as a variable, for example, I have to make sure to use the CF standard name for dissolved oxygen and report the results in CF standard units.”

The Endurance Array team was the first group to add any of the non-CTD variables into the Glider DAC. This important step forward was recognized by the glider community, and was announced at a May 2019 workshop at Rutgers with 150 conveyors of glider data in attendance.  One of Pearce’s gliders was used as the example of how and what could be achieved with the new code.

To help expedite the transfer of all gliders into the DAC, Pearce made his code open access. The additional metadata will help advance the work of storm forecasters, researchers, and others interested in improving understanding ocean processes.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Irminger Sea Intermediate Water Formation and Transport

[caption id="attachment_18947" align="aligncenter" width="640"] Figure 19. Planetary potential vorticity (PPV) at (a) OSNAP mooring CF5, within the Irminger Sea boundary current core (b) OSNAP mooring M1, at the edge of the boundary current and (c) OOI flanking mooring (FLMA) and Surface Mooring within the Irminger Sea gyre. From Le Bras et al. (2020).[/caption]

A two-year record from moorings in the Irminger Sea allowed researchers (Le Bras et al., 2020) to investigate both deep convection and transport of water masses associated with the Atlantic overturning circulation.  Using mooring data from the OOI Irminger Sea Array and the Overturning in the Subpolar North Atlantic (OSNAP) array, the authors were able to identify two types of Irminger Sea Intermediate Water (ISIW) formed by deep convection.  Upper ISIW is found near the edge of the Irminger Sea western boundary current, whereas Deep ISIW is formed in the basin interior.  Water masses were diagnosed using temperature-salinity properties and the planetary potential vorticity (PPV). Figure 19 shows PPV for three different locations, in the boundary current, at its edge, and in the Irminger Sea gyre.  Black lines in the figure indicate the isopycnals that bound upper and deep ISIW as defined by the authors, the red contours enclose water with low PPV (indicative of convection) and the green lines indicate the mixed layer depth.

Seasonal pulses of low PPV water in the boundary current occurring below the mixed layer (Figure 19a) suggest subduction from a non-local source offshore.  In contrast, low PPV water in the gyre interior is accompanied by a deep winter mixed layer and appears related to local convection.  Further analysis by the authors indicates that waters formed by convection in the interior gyre are entrained into the boundary current within a few months of formation.  Importantly, it appears that eddy dynamics are responsible for this transport of ventilated water from the interior to the boundary, and that the upper ISIW in the boundary current is a significant component of the Atlantic overturning circulation.

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