Sound is omnipresent in the ocean. Human-induced noise has the potential to affect marine life.
After the global recession in 2008, the ocean became quieter as shipping declined. Off the coast of Southern California, for example, scientists at Scripps Institution of Oceanography found that noise amplitudes measured from 2007-2010 were lowered by 70 percent with a reduction in one ship contributing about 10 percent.
A similar quieting of the ocean can be expected as global ship traffic continues its decline in response to the corona virus pandemic. This quieter ocean offers scientists ways to expand their ongoing research on ocean sound and its impact on marine life.[media type="image" path="https://oceanobservatories.org/wp-content/uploads/2020/04/Finhval_1.jpg" link="#" alt="Fin Whale"][/media]
“It takes time to document real change in the ocean, but University of Washington oceanographers have reported that over the past decade, fin whales have been communicating more softly in the Pacific,“ said Deborah Kelley, professor of oceanography at the University of Washington and director of the OOI’s Regional Cabled Array (RCA) component. “A quieter ocean allows us to hear more clearly life and other natural processes within the ocean.”
Years of listening to whales
John Ryan, a biological oceanographer at the Monterey Bay Aquarium Research Institute (MBARI), has been “listening in” on whales and other marine creatures since 2015 using a hydrophone on the Monterey Accelerated Research System (MARS), a cabled observatory, which was in part established as a test bed for the OOI Regional Cabled Array. Ryan and colleagues studied the occurrence of humpback whale (Megaptera novaeangliae) song in the northeast Pacific using three years of continuous recordings off the coast of central California.[media type="image" path="https://oceanobservatories.org/wp-content/uploads/2020/04/Humpback_Whale_underwater_shot.jpg" link="#" alt="Humpback Whale"][/media]
“We’ve been listening almost continuously since July 28, 2015, using a broadband, digital, omnidirectional hydrophone connected to MARS. Listening continuously for that long at such a high sample rate is not easy; only by being connected to the cable is this possible,” explained Ryan.
The researchers were able to discern whale songs from the busy ocean soundscape in Monterey Bay National Marine Sanctuary, which is a feeding and migratory habitat for humpback whales. The humpbacks’ song was detectable for nine months of the year (September–May) and peaked during the winter months of November through January. The study revealed strong relationships between year-to-year changes in the levels of song occurrence and ecosystem conditions that influence foraging ecology. The lowest song occurrence coincided with anomalous warm ocean temperatures, low abundances of krill – a primary food resource for humpback whales, and an extremely toxic harmful algal bloom that affected whales and other marine mammals in the region. Song occurrence increased with increasingly favorable foraging conditions in subsequent years.
Because the hydrophone is on the cabled observatory, its operation can be adjusted to achieve new goals. For example, the sampling rate of the hydrophone was doubled during an experiment that successfully detected very high frequency echolocation clicks of dwarf sperm whales (with Karlina Merkens, National Oceanic and Atmospheric Administration). “And that’s a beautiful aspect of being on the cable,” added Ryan. “Not only do we know that it is working, we catch any network glitches pretty quickly so we don’t lose data, and we can do real-time experiments like these.”
William Wilcock of the University of Washington and his students have compiled a decade worth of data on fin whales in the northern Pacific. Fin whales call at about 20 HZ, which is too low of a frequency for humans to hear, but perfect for seismometers to record. The researchers aggregated ten years of data from both temporary recorders and now permanent RCA hydrophones and seismic sensors and looked at the frequency of the calls and calling intervals. The researchers found both have changed over time.
The fin whales call seasonally and the frequency of the calls has gone down with time.[audio mp3="https://oceanobservatories.org/wp-content/uploads/2020/04/Fin_whale_10x.mp3"][/audio]
Calls peak in late fall, early winter in relation to mating season. Gradually through the season the frequency decreases. At the start of the next season, the call frequency jumps up again, but not quite to where it was the year before. Over ten years, the frequency has gone down about 2 HZ, and scientists are puzzled as to why this is occurring. It is unlikely to be due to increasing ship noise, because this lower sound frequency is getting closer to the range of the noise level of container ship propellers, about 6-10 HZ.
In some settings, ship noise is known to affect whale behavior and the permanent network of hydrophones operated by the OOI and Ocean Networks Canada will provide an opportunity to study whether whales are avoiding the shipping lanes to Asia.
Volcanoes also rumble in the deep
Whale sounds are but one of many acoustic signals being recorded and monitored using hydrophones and broadband seismometers. The OOI’s RCA off the Oregon Coast includes 900 kilometers (~560 miles) of submarine fiber-optic cables that provide unprecedented power, bandwidth, and communication to seafloor instrumentation and profiler moorings that span water depths of 2900 m to 5 m beneath the ocean surface. Using a suite of instruments connected to the cable, which continuously stream data in real time, scientists are listening in on the sounds of submarine volcanism, which accounts for more than 80 percent of all volcanism on Earth.
More than 300 miles off the Oregon coast in 1500 meters of water, 20+ cabled seafloor instruments are located at the summit of Axial Seamount, the most active volcano on the Juan de Fuca Ridge, including hydrophones and seismometers, which can also record sounds in the ocean.
“Scientists were able to hear(as acoustic noises traveling through the crust) >8000 earthquakes that marked the start of the Axial eruption in 2015. Coincident with this seismic crisis bottom pressure tilt instruments showed that the seafloor fell about 2.4 meters (~8 feet).[video width="670" height="384" m4v="https://oceanobservatories.org/wp-content/uploads/2020/04/Axial-seamount-audio-.m4v"][/video]
It was a remarkable collaborative event with scientists from across the country witnessing the eruption unfold live,” added Kelley. Such real-time documenting of an eruption in process was possible because of how Axial is wired. It is the only place in the oceans where numerous processes taking place prior to, during, and following a submarine eruption are captured live through data streaming 24/7. William Wilcock, University of Washington, and Scott Nooner, University of North Carolina, Wilmington, and colleagues reported these findings in Science, 2016.
Data collected from the hydrophones at the seamount’s base supported another discovery about Axial, indicating that it explosively erupted in 2015. Hydrophones recorded long-duration diffusive signals traveling through the ocean water consistent with explosion of gas-rich lavas, similar to Hawaiian style fissure eruptions. Follow-on cruises documented ash on some RCA instruments, again indicating the likelihood of explosive events during the 2015 eruption.
“Having the opportunity to listen in while a submarine volcano is active offers a really interesting window into things,” said Jackie Caplan-Auerbach, associate dean at Western Washington University and lead author of a G-cubed article that reported the possible eruptive findings. “While we cannot say with utter certainty that there were explosions at Axial, there’s a lot of evidence that supports this. We know from having listened to other eruptions that this was the same type of sound. It’s distinct, like the hissing sound of a garden hose on at top speed. We also found these really fine particulates, which could only have resulted from an eruption, had collected on one of the instruments at the site.”[audio wav="https://oceanobservatories.org/wp-content/uploads/2020/04/axial_explosive.wav"][/audio]
Added Caplan-Auerbach, “My favorite part of having OOI is it offers an ability for pure discovery. Its real time nature makes it possible to observe and see what happens. And sometimes the planet just hands you a gift that you didn’t expect. Not always being hypothesis driven is a very valuable aspect of science that I hope does not get lost. I’m very appreciative of projects like this that open our eyes into signals that we didn’t know were there.”
More opportunities to expand knowledge about sound and the sea are on the horizon. The US. Navy has funded Shima Abadi, University of Washington, Bothell, for a comprehensive study of sounds recorded by the OOI hydrophones. Stay tuned!
Image credits: Top fin whale: Wikipedia, Aqqa Rosing-Asvid – Visit Greenland. Second from top: humpback whale: Public domain, National Oceanic and Atmospheric Administration.
“Just like lightning,” in one-minute presentations, 15 scientists shared amazing ways they are using OOI data in scientific investigations and in the classroom. This round of lightning talks capped the Ocean Observatories Initiative Facility Board’s (OOIFB) Town Hall at the 2020 Ocean Sciences Meeting on 20 February, demonstrating the multiple and creative ways OOI data are being used to answer key science questions in a changing environment.
The presentations ranged from how students are using real-life and real-time OOI data to advance their understanding of scientific principles to how researchers are using OOI data to identify the presence of marine life by sound to how modelers are making OOI data more accessible and useable.
“We were simply thrilled by the depth, breadth, and range of applications of OOI data shown during this lightning round,” Kendra Daly, chair of the OOIFB. “We were pleased so many presenters were willing to accept the challenge. This enthusiastic response clearly shows that OOI data are being used to help answer important science questions.”
Brief summaries of the talks are presented below.
Isabela Le Bras, Scripps Institution of Oceanography, reported on a recent article in Geophysical Research Letters, where she and her colleagues describe how they used data from the Irminger Sea Array moorings (2014–2016) to identify two water masses formed by convection and showing that they have different rates of export in the western boundary current. Upper Irminger Sea Intermediate Water appears to form near the boundary current and is exported rapidly within three months of its formation. Deep Irminger Sea Intermediate Water forms in the basin interior and is exported on longer time scales. The subduction of these waters into the boundary current is consistent with an eddy transport mechanism. The eddy transport process is more effective for the waters cooled near the boundary current, implying that cooling near boundary currents may be more important for the climate than has been appreciated to date.
Since 2017, Clare Reimers and Kristen Fogaren, Oregon State University, have been working to assess seasonal variability in benthic oxygen consumption and the contribution of benthic respiration to the development of hypoxic conditions in the northern California Current, using time series data from the OOI Endurance Array. Reimers and Fogaren measured benthic oxygen consumption rates using in situ eddy covariation techniques and ex situ core incubations, during a series of ten cruises that allowed sampling near the Endurance Oregon Shelf and Inshore stations, in all seasons. During these cruises, the researchers used real-time data provided by the Endurance Array to optimize the settings for their eddy covariance deployments. They are now examining property-relationships in discrete bottom water samples collected during the cruises and using data from OOI assets to help separate influences of mixing and biochemical processes in the water column and sediments. The researchers are also synthesizing benthic flux measurements and placing these rates in the context of cross-shelf glider measurements and benthic node time series.
Adrienne Silver, University of Massachusetts Dartmouth provided details about how she is using Pioneer Array data to learn more about the influence of warm core rings on Shelf break circulation. Results from a 40-year Warm Core Ring census show a regime shift in warm core ring formation at 2000, with the number of rings doubling from an average of 18 rings per year (during 1980-1999) to 33 rings per year (during 2000-2019). This regime shift creates a large increase in the amount of warm salty water being transported northward toward the shelf from the Gulf Stream. The preferred pathway of these rings, or the Ring Corridor seem to indicate their proximity to the shelf break and the Pioneer array during their lifetime. The goal of Silver’s project is to understand how these warm core rings affect the shelf break exchange while traveling along the shelf. A large focus of the study will be on the salinity intrusion events which might be sourced from these warm core rings.
Liz Ferguson, CEO and founder of Ocean Science Analytics, is using data from OOI’s Coastal Endurance and Regional Cabled Arrays to determine the variables that are most useful for assessing the ecosystem of this region and obtaining baseline information on marine mammal acoustic presence for use in monitoring. Using long term physical and biological data provided by these arrays, Ferguson is assessing long-standing shifts in the ecology of this coastal and offshore environment by associating physical oceanographic variables with the vocal presence of marine mammals using the broadband hydrophone data. Temporal changes in the occurrence of marine mammal species such as killer whales, sperm whales and dolphins can be used as an indicator of ecosystem shifts over time. She is analyzing passive acoustic data provided by the OOI arrays to determine the presence of vocally active marine mammal species, identify their spatial and temporal use of these sites, and combining this information with the physical oceanographic variables to assess the ecological characteristics associated with marine mammal occurrence.
Sam Urmy of the Monterey Bay Aquarium Research Institute (MBARI) also is using OOI acoustical data in his research. Using an upward-looking echosounder and a high-frequency hydrophone at MBARI’s Monterey Accelerated Research System, Urmy showed how small animals in the epipelagic and mesopelagic altered their behavior in response to predators. These responses included abrupt dives during bouts of foraging by dolphins, changes in depth to avoid predatory fish schools, and dramatic alterations to daily vertical migratory behavior. Continual observations of the mesopelagic with active and passive acoustics are revealing several dynamic predator-prey interactions in an ecosystem that is typically thought of as relatively slow and static.
Veronica Tamsitt of the University of New South Wales used the OOI’s Southern Ocean mooring and the Southern Ocean Flux Site (SOFS, in the Southeast Indian) to study the Sub Antarctic Mode water (SAMW) formation. Tamsitt’s and her colleagues findings were reported in the Journal of Climate in March 2020. Using data from the two mooring locations, the researchers were able to compare and contrast characteristics and variability of air-sea heat fluxes, mixed-layer depths, and SAMW formation. The researchers found that inter mixed-layer depth anomalies tended to be intermittent at the two moorings, where anomalously deep mixed layers were associated with anomalous advection of cold air from the south, and conversely shallow mixed layers correspond to warm air from the north. Both the winter heat flux and mixed-layer depth anomalies, however, showed a complex spatial pattern, with both positive and negative anomalies in both the Indian and Pacific basins that Tasmitt and colleagues relate to the leading modes of climate variability in the Southern Ocean.
Editor’s note: The Southern Ocean Array was decommissioned in January 2020. Its data, however, are still available for use by researchers, students, and the public.
Bringing OOI data into the classroom
Sage Lichtenwalner, Department of Marine and Coastal Sciences at Rutgers, The State University of New Jersey reported on the progress of the Ocean Data Labs Project. This project is a Rutgers-led effort to build a “Community of Practice” to tap into the firehose of OOI ocean data to support undergraduate education. To date, the project has hosted four “development” workshops that introduced participants to the OOI, conducted data processing with Python notebooks, and shared effective teaching strategies, in addition to a series of introductory workshops and webinars. As part of the development workshops, 56 university, college, and community college faculty designed 19 new “Data Explorations,” featuring web-based interactive “widgets” that allow students to interact with pre-selected data from the OOI. The project also sponsors a series of webinars, a fellowship program, and is compiling a library of resources (including coding notebooks, datasets, and case studies in teaching) to help the community.
Cheryl Greengrove, University of Washington Tacoma, summarized an article in the March issue of Oceanography that she and colleagues from across the United States wrote detailing ways to integrate OOI data into the undergraduate curriculum. The wealth of freely-accessible data provided by OOI platforms, many of which can be viewed in real or near-real time, provides an opportunity to bring these authentic data into undergraduate classrooms. The TOS article highlights existing educational resources derived from OOI data that are ready for other educators to incorporate into their own classrooms, as well as presents opportunities for new resources to be developed by the community. Examples of undergraduate introductory oceanography OOI data-based lessons using existing interactive online data widgets with curated OOI data on primary productivity, salinity, and tectonics and seamounts are presented, as well as ways to use OOI data to engage students in undergraduate research. The authors provide a synthesis of existing tools and resources as a practical how-to guide to support new resource development and invite other educators to develop and implement new educational resources based on OOI data.
Matthew Iacchei, Hawaiʻi Pacific University, presented how he has been integrating OOI data explorations to supplement his upper division oceanography lecture and labs with real data from around the world. Last semester, he had students explore patterns of dissolved oxygen and impacts of anoxia at the coastal endurance array in Oregon and compare that data to dissolved oxygen data the students collected in Kāneʻohe Bay, Hawaiʻi. This semester, students are working through two exercises with OOI data as part of their primary productivity lab (perfect, as it is now online!). Students will compare vertical profiles from Hawaiʻi with seasonal variations across the world, and will compare latitudinal drivers of primary production using data from a time-series from the Southern Ocean Array.
Strengthening OOI data usability
Wu-Jung Lee, a senior oceanographer at the Applied Physics Laboratory, University of Washington, is using data collected by the OOI to develop new methodologies for analyzing long-term ocean sonar time series. In a project funded by the National Science Foundation, she and her colleagues show that unsupervised matrix decomposition techniques are effective in discovering dominant patterns from large volumes of data, which can be used to describe changes in the sonar observation. Their preliminary analysis also show that the summaries provided by these methods facilitate direct comparison and interpretation with other ocean environmental parameters concurrently recorded by the OOI. A parallel effort that spun out of this project is an open-source software package echopype, which was created to enable interoperable and scalable processing of biological information from ocean sonar data.
As part of the Rutgers Ocean Modeling Group, in conjunction with University of California Santa Cruz, John Wilkin and Elias Hunter are delivering a high-resolution data assimilative ocean model analysis of the environs of the Pioneer Coastal Array, including a systematic evaluation of the information content of different elements of the observing network. The project uses the Regional Ocean Modeling System with 4-Dimensional Variational data assimilation. To produce a comprehensive multi-year (2014-2018) analysis required them to assimilate all available Pioneer CTD data, with quality checks, in a rolling sequence of data assimilation analysis intervals. They used three days of data in each analysis, which required queries to with a time range constraint and relevant platform (i.e. glider, profiler, fixed sensor), migrating all Pioneer CTD data (wire following profilers, gliders, fixed sensors, plus ADCP velocity) to an ERDDAP server. The simple graphing capabilities in ERDDAP allow quick browsing of the data to trace quality control or availability issues, and ERDDAP provides a robust back-end to other web services to create more sophisticated graphical views, or time series analysis. Using the ERDDAP Slide Sorter tool, they operate a quick look Control Panel to monitor the data availability and quality.
Mitchell Scott and colleagues Aaron Marburg and Bhuvan Malladihalli Shashidhara at the University of Washington, are studying how to segment macrofauna from the background environment using OOI data from the Regional Cabled Axial Seamount Array. Their long-term goal is to use an automated approach to study species variation over time, and against other environmental factors. Their initial step focuses specifically on scale worms, which are very camouflaged, making them difficult to detect. To address this, the researchers initially used a deep learning model, called U-Net, to detect and localize the scale worm locations within an image. To address the high rate of false positives using this model, they added an additional classifier (a VGG-16 model) to verify the presence of scaleworms. This combined, applied approach proved feasible for scale worm detection and localization. Yet because the environment of the Axial Seamount is so dynamic due to the growth and decay of chimneys at the site and resulting changes in bacteria and macrofauna present, they found the performance of the model decreased over time.
Weifeng (Gordon) Zhang of Woods Hole Oceanographic Institution has been using Pioneer Array data to understand the physical processes occurring at the Mid-Atlantic Bight shelf break, including the intrusion of Gulf Stream warm-core ring water onto the shelf and the ring-induced subduction of the biologically productive shelf water into the slope sea. His findings were reported in a Geophysical Research Letters paper where data from the Pioneer Array moorings and gliders demonstrated the anomalous intrusion of the warm and salty ring water onto the shelf and revealed the subsurface structure of the intrusion. Zhang also shared findings reported in the Journal of Geophysical Research: Oceans where data from the Pioneer Array showed a distinct pattern of relatively cold and fresh shelf water going underneath the intruding ring water. These results show the subduction of the shelf water into the slope sea and a pathway of shelf water exiting the shelf. In both instances, Zhang and his colleagues used computer modeling to study the dynamics of these water masses. These two studies together suggest that shelf break processes are complex and require more studies in the region.
Hilary Palevsky of Boston College presented results from an ongoing project funded by the National Science Foundation’s Chemical Oceanography program, using biogeochemical data from the OOI Irminger Sea Array. Analysis of dissolved oxygen data on OOI Irminger Sea gliders and moorings from 2014-2016 showed the importance of biogeochemical data collected over the full seasonal cycle and throughout the entire water column, due to the influence of subsurface respiration and deep winter convection on biological carbon sequestration. The OOI Irminger Sea array is the first source of such full-depth year-round data in the subpolar North Atlantic. To quantitatively evaluate the annual rate of carbon sequestration by the biological pump and the role of deep winter convection, Palevsky and colleague David Nicholson of the Woods Hole Oceanographic Institution collaborated with OOI to improve the calibration of oxygen data at the Irminger Sea array by modifying the configuration of glider oxygen sensors to enable calibration in air each time the glider surfaces, which improves the accuracy and utility of the data collected both from gliders and from moorings. Palevsky presented preliminary results demonstrating successful glider air calibration at the Irminger array in 2018-2019 as well as work by student Lucy Wanzer, Wellesley College, demonstrating the importance of well-calibrated oxygen time series data to determine interannual variability in rates of subsurface respiration and deep winter ventilation in the Irminger Sea.
Remarkable changes in seafloor topography and biological communities, quantification of methane flux, and connections from the seafloor to upper water column methanotrophy.
Marcon and Bohrmann, 13 December 2019
Southern Hydrate Ridge (SHR) is one of the most active and dynamic methane seep sites known. Repeat investigations during Regional Cabled Array (RCA) cruises show that it is highly dynamic, delineated by exceptional changes in seafloor morphology, venting intensity and temporal variability, and by the distribution and density of associated biological communities (Fig. 1) [1-6]: here, AI is being utilized to quantify the areal extent of seeps and classification of organisms [4,7]. Since first imaged in 2010, the summit of SHR has changed remarkably with areas of smooth, gentle hummocks transformed into extensive, highly rugged and steep-sided collapsed pits from which jets and explosions of bubbles occur (Figs. 1c-h). Equally dynamic are changes in the locations and thicknesses of microbial mats that mark more diffuse seepage of methane from the seafloor. Surprisingly, chemical results from continuous measurements from RCA flow meters show an annual net transport of fluid downward into the sediment resulting in the development of new transport models for these seep environments . At the focused RCA experimental site “Einsteins’ Grotto” and at a site to the north, hydrate is exposed at the seafloor within the collapsed pits (Fig. 1d).
Because of OOI, SHR is one of only three places (the others being Ocean Networks Canada Barkley Canyon and Clayoquot Slope sites) in the oceans where time series investigations of methane release are conducted at hour to year time periods utilizing ship and RCA PI cabled multibeam sonars, cameras and an upward-looking ADCP [2, 5-6, 9-11]. Results from a 3-year investigation of SHR show that the locations of seep activity and bubble release remained unchanged, however, the magnitude of gas release was highly variable on hourly time scales (Fig. 1a) . Bubble plumes rise up to ~480 above the seafloor and in several cases exceed the upper limit of hydrate stability by ∼190 m. Here, shallow subsurface waters, where methane disassociates, is marked by high density regions of lantern fish, consistent with increased biological activity associated with the microbial oxidation of the released methane (Fig. 1a) .
As a key cabled site on the RCA, SHR has attracted numerous national and international investigators including a several year program funded by the German Federal Ministry of Education and Research to quantify methane flux from the highly active Southern Hydrate Ridge RCA site (G. Bohrmann and Y. Marcon, MARUM, University of Bremen, Germany; “Sonar monitoring of natural release of methane greenhouse gas from the seafloor – A contribution to the understanding of global change.”). In 2018, it was mapped at submeter resolution and the entire site photo mosaicked as part of a Schmidt-funded program (B. Thornton, University of South Hampton). Cabled infrastructure now installed as part of the MARUM project includes an overview multibeam sonar that completes a 360° scan every 2 hrs and spans a distance of 700 m, imaging all sites of bubble plume emissions at SHR (Fig. 1b) [5-6; 10-11]. Other infrastructure includes a multibeam, very high-resolution sonar that quantifies bubble emissions from Einstein’s Grotto, a 4k video and digital still camera that takes 3 images each hour of the explosive hydrate-bearing site – Einsteins’ Grotto (Fig. 1h), and a CTD to examine the impacts of ocean warming and release of methane into the hydrosphere. Automated plume imaging is now utilized for time-series hourly imaging by the RCA digital still camera [5-6]. The images, available through the OOI Data Portal, document remarkable changes of the collapse pit over time and in associated biology.[blockquote]
 Kelley, D.S. (2016) Real-time multidisciplinary monitoring of a highly dynamic methane seep: The OOI Cabled Array at Southern Hydrate Ridge. Gordon Conference Natural Hydrate Systems. Interfacial science advances towards understanding and monitoring gas hydrate systems. Galveston, February 28 – March 4, 2016.
 Philip. B.T., Denny, A.R., Solomon, E.A., and Kelley, D.S. (2016) Time-series measurements of bubble plume variability and water column distribution above Southern Hydrate Ridge. Geochemistry, Geophysics, Geosystems, 17 (3) 10.1002/2016GC006250.
 Bigham, K., Kelley, D.S., Solomon, E.A., and Delaney, J.R. (2017) Extreme Morphologic and Venting Changes in Methane Seeps at Southern Hydrate Ridge, Cascadia Margin. American Geophysical Union, Fall Meeting 2017, OS53B-1199.
 Bigham, K., Kelley, D.S., Marburg, A., and Delaney, J.R. (2017) Further Interpretation of the Relationship between Faunal Community and Seafloor Geology at Southern Hydrate Ridge, Cascadia Margin: Exploring Machine Learning, American Geophysical Union, Fall Meeting 2017, U21B-09.
 Bohrmann, G., and Marcon, Y., (2019) Long-term monitoring of gas emissions at Southern Hydrate Ridge. American Geophysical Union, Fall Meeting 2019. OS51A-04.
 Marcon, Y., and Bohrmann, G. (2019) Long-term monitoring of gas emissions at Southern Hydrate Ridge. American Geophysical Fall Meeting 2019, OS51A-04.
 Marburg, A., and Bigham, K., (2016) Deep learning for benthic fauna identification, Oceans 16 MTS/IEEE Monterey, 10.1109/OCEANS.2016.7761146.
 Whorley, T.L., Solomon, E.A., Kowalski, L., and Centurion, R., (2019) Persistent downward flow of seawater beneath Beggiatoa mat communities at Hydrate Ridge – mechanisms and biogeochemical implications. American Geophysical Union, Fall Meeting 2019, OS43B-1706.
 Philip. B.T., Kelley, D.S., Solomon, E.A., and Delaney, J.R. (2016) Monitoring methane emissions at Southern Hydrate Ridge using an OOI Cabled Array Acoustic Doppler Current Profiler. OCEANS 2016 MTS/IEEE Monterey, 10.1109/OCEANS.2016.7761469
 Marcon, Y., Sahling, H., von Wahl, T., Spiesecke, U, Vittori, V., Leymann, T., and Bohrmann, G., (2018) M³: Towards Long-Term Acoustic Monitoring of Gas Emissions using Underwater Cabled Observatory Technology. Ocean Sciences Meeting, doi.org/10.1002/essoar.b8ca5006b4256b34.3745ac673d8f4f8a.1.
 Marcon, Y., Kopiske, E., Leymann, T., Spiesecke, U., Vittori, V., von Wahl, T., Wintersteller, P., Waldmann, C., and Bohrmann, G., (2019) A rotary sonar for long-term acoustic monitoring of deep-sea gas emissions. OCEANS19 – Marseille, IEEE. 10.1109/OCEANSE.2019.8867218.
[/blockquote] Read More
Gawarkiewicz et al., 22 November 2019
Marine heat waves are warm anomalies persisting for days to months and on spatial scales from 1-1000 km (Hobday et al., 2016). These heat waves disturb the marine environment and may have significant feedbacks on the atmosphere. Recent studies suggest that the New England continental shelf is increasingly impacted by Warm Core Rings (WCR) initiating from the Gulf Stream. Gawarkiewicz et al 2019 describe a strong marine heatwave in early 2017 that was apparently initiated by a WCR intrusion onto the shelf.
The first indication of the 2017 heatwave was from a Rhode Island fisherman who noticed unusual species (typically found in Gulf Stream waters) in his catch from the New England shelf. This indicated unusually warm waters on the shelf, and researchers began to investigate the regional extent. A number of different data sources, including OOI Pioneer Array assets, were necessary to track the anomalies along the length of the Middle Atlantic Bight (MAB).
Temperature anomalies measuring up to 6 C and salinity anomalies exceeding 1 PSU were found. The duration of the heatwave was approximately 4 months, initiating near Nantucket Shoals in Jan 2017, traversing the entire MAB, and dissipating offshore of Cape Hatteras in April. The advective path of the heatwave extended roughly 850 km.
Comparison with historical records from 1940 to 1996 showed that the 2017 heatwave was an unprecedented event in terms of temperature and salinity anomalies. The heat wave had significant impacts, including shoreward shift of the shelfbreak front, lowered chlorophyll concentrations, and the presence of warm water fish in New England coastal waters.Read More
Dever et al., 29 September 2019
The full scope of OOI Endurance Array surface moorings has been deployed since April 2015. The moorings are deployed off Grays Harbor, Washington and Newport, Oregon at inner shelf, shelf and slope depths. They include surface meteorology, physical oceanographic, chemical and biological sensors. During the summer of 2019, EA staff reviewed mooring data since inception. In September 2019, we presented a poster of these data at the annual Eastern Pacific Ocean Conference (EPOC). The objectives of the poster were to show the time series data and discuss their availability and quality issues with research community members. To stimulate discussion, we reported on seasonal variability in wind forcing, water temperature, and chl-a fluorescence. We described the mooring measurements and how to access the data.
The Oregon and Washington shelves are part of the northern California Current Marine Ecosystem. They exhibit characteristic responses to spring and summer upwelling winds and winter storms. In the above figure, we show representative time series of near surface measurements at the Oregon shelf mooring since its start in April 2015 through the present. As part of the poster, we also presented similar data from the other OOI surface moorings and calculated lagged correlations between wind, temperature, and chlorophyll, and commented on the observed variability.
We also pointed viewers to example Matlab and Python scripts to download and plot the OOI data presented in the poster via the Machine to Machine (M2M) interface on the OOI Data Portal.Read More
Blow down of the 200-meter Shallow Profiler Mooring Platform 2019
K. Roseburg and W. Ruef, Regional Cabled Array and P. MacCready, University of Washington, 20 August 2019
In June and August, 2019, the Slope Base Shallow Profiler Mooring was impacted by two substantial “blow down” events: these were the first observances of blow downs since the moorings were installed in 2014. The largest of these events, which occurred near the end of July and which lasted over two weeks, resulted in a deepening of the 12 ft across, 7,000 lb. platform nearly 50 m and migration of the platform ~ 150 m to the west. Results from pressure, ADCP, temperature and oxygen data pulled from CI using M2M, indicate that as the currents strengthened, the float was depressed into ~ 0.25-0.50°C cooler water with slightly decreased oxygen concentrations. An evaluation of the eddy kinetic energy calculated from the ADCP data, does not support eddy-driven water mass transport. The lower oxygen concentrations could reflect lower amounts of photosynthesis as the platforms are pushed deeper into the water column. We do not know of other documented blow down events such as these in the PNW.Read More
Deep temperature modulations at Axial Base
Interactive Oceans Data Portal, 21 July 2019
Axial Base is the only site in the world’s oceans where continuous full water column measurements are being made, spanning >2600 m to ~ 5 m beneath the oceans’ surface (a & b). The Axial Base Deep Profiler (DP) Mooring has been operational for >17 months, completing two profiles a day from ~2650 m to 127 m (b). Since August 2019, DP vehicle measurements overlap with those made by instruments on the Shallow Profiler Mooring, which conducts nine profiles a day (a): since 2015, the three Shallow Profiler science pods have conducted >40,000 profiles. The high-resolution temperature measurements delineate fine scale structure both in shallow waters and below 1000 m water depth (c&d) marked by regular vertical striations . These perturbations may result from the vertical advection of the temperature field by passing semidiurnal internal tides (D. Luther, pers. com). Some modulations may be wind-driven inertial waves. Examination of dissolved oxygen concentrations during this same time period are not consistent with drawdown caused vehicle movement. Additional analyses are required, however, to unequivocally determine the processes responsible for these perturbations. A Jupyter notebook on the UW interactiveoceans data portal is now developed to analyze MODIS satellite data (chlorophyll) with measurements being made by instruments on the Shallow Profiler mooring (interactive oceans.washington.edu).Read More
Hopkins et al., 23 April 2019
Hopkins et al., 2019 use data from the OOI Irminger Sea flanking moorings to create the longest continuous record to date of Deep Western Boundary Current (DWBC) volume transport in the region. This study, part of the Overturning in the Subpolar North Atlantic Program (OSNAP), used data from two OOI flanking moorings, along with three U.S. OSNAP moorings, and five U.K. OSNAP moorings to determine the 22-month mean DWBC volume transport, and its spatial structure off Greenland (Figure above).
Determining DWBC properties is critical to understanding the transport of heat, salt, nutrients, and carbon by the Atlantic Meridional Overturning Circulation (AMOC), part of a system of currents that form the global thermohaline circulation. The combined OSNAP/OOI mooring array deployed at 60°N in the Irminger Sea during 2014 – 2015 provides the longest continuous record of DWBC volume transport at this latitude. This enables not only the most reliable estimate available of the mean transport, but the ability to investigate temporal variability.
Several key points are made by the authors. First, the average volume transport of deep water was 10.8 ± 4.9 Sv (mean ± 1 std) to the south. Of the total transport, North East Atlantic Deep Water accounted for about 6.5 Sv while about 4.1 Sv was associated with the Denmark Strait Overflow. Second, the long record allows the first systematic investigation of DWBC variability. The observed transport shows a shift from high to low frequency fluctuations with increasing distance from the East Greenland coast. High‐frequency fluctuations (2–8 days) dominate close to the continental slope, likely associated with topographic Rossby waves and/or cyclonic eddies. In deeper water, transport variance at 55 days dominates. Finally, the results indicate a modest (1.8 Sv) increase in total transport since 2005–2006, but this difference can be accounted for by a range of methodological and data limitation biases. This is of interest because although AMOC variability related to climate change is expected to be reflected in DWBC transport and properties, conclusive observational evidence of transport change has been elusive.Read More
Josey et al., 18 December 2018
A recent paper by Josey et al.  use data from the OOI Irminger Sea surface mooring to present the ﬁrst characterization of multi-winter surface heat exchange at a high latitude North Atlantic site based on in-situ measurements. Heat loss in the North Atlantic is a primary determinant of how much deep water is formed in a given winter, which ultimately influences the strength of the Atlantic circulation. The Irminger Sea is a key deep convection site , , but the amount of heat lost is poorly known because winter measurements are difﬁcult to obtain in the harsh environment .
Data from the first four deployments of the Irmginer surface mooring provided early winter observations in three consecutive years – 2014, 2015 and 2016. Strong variations on times scales of days to weeks are apparent in the air-sea flux components. These combine to create net heat losses exceeding 400 W/m^2 on at least one occasion each winter (Fig. 1 d).
The integrated effects of the anomalously strong heat loss events in 2014–2015 result in cumulative net heat loss significantly greater than following years (Fig. 1 e,f) This is primarily due to variations in frequency of intense short timescale (1–3 days) forcing (Fig. 1g) that would be difficult to detect without the mooring observations.
Interpreting the observations in the context of a high-resolution atmospheric model (European Centre for Medium Range Weather Forecasts Reanalysis 5) shows that the main source of multi-winter variability is changes in the frequency of Greenland tip jets that can result in hourly mean heat loss exceeding 800 W/m2 (Fig. 1g). The tip-jet events result from the mountainous Greenland terrain, which focuses winds into narrow, very strong jets over the ocean , . Josey et al.  suggest how changing atmospheric circulation may influence the number of events and hence the ocean heat loss.
Improved understanding of Irminger Sea winter heat loss is likely to be critical to reliable projections of future changes in both the North Atlantic overturning circulation and climate variability.[blockquote]
 Josey, S.A., M.F. de Jong, M. Oltmanns, G.K. Moore and R.A. Weller, 2019. Extreme variability in Irminger Sea winter heat loss revealed by ocean observatories initiative mooring and the ERA5 reanalysis, Geophys. Res. Lett., 46. https://doi.org/10.1029/ 2018GL080956
 de Jong, M.F. and L. de Steur, 2016. Strong winter cooling over the Irminger Sea in winter 2014–2015, Geophys. Res. Lett., 43, 106–107. https://doi.org/10.1002/2016GL069596
 de Jong, M.F., M. Oltmanns, J. Karstensen, and L. de Steur, 2018. Deep convection in the Irminger Sea observed with a dense mooring array. Oceanography, 31(1), 50–59. https://doi.org/10.5670/oceanog.2018.109
 Doyle, J.D. and M.A. Shapiro, M. A., 1999. Flow response to large-scale topography: The Greenland tip jet. Tellus A: Dynamic Meteorol. and Oceanog., 51(5), 728–748. https://doi.org/10.3402/tellusa.v51i5.14471
 Moore, G. W. K., & Renfrew, I. A. (2005). Tip jets and barrier winds: A QuickSCAT climatology of high wind speed events around Greenland, J. Climate, 18(18), 3713-3725, https://doi.org/10.1175/JCLI3455.1.
[/blockquote] Read More
Zhang and Partida, 15 October 2018
The shelf break front is a persistent feature in the Middle Atlantic Bight, with the foot of the front found near the 100 m isobath. Warm core rings pinched off from the Gulf Stream are found over the continental slope, and have significant impacts on the frontal system when they impinge on the shelf. Zhang and Partida, 2018 use data from OOI Pioneer Array moorings and gliders to document a unique shelf/slope interaction related to the presence of a warm core ring.
Satellite SST imagery shows a well-formed ring impinging on the shelf south of New England during June 2014. Observations from the Pioneer Offshore and Central Offshore moorings are able to identify relatively cold, fresh shelf water that migrates downward with time during the period that ring water is at the surface. Relatively high dissolved oxygen concentration indicates that the shelf water was recently exposed to the surface. This suggests that shelf water filaments are being subducted at the edge of the ring. A cross-shelf section from the Pioneer EB glider (Figure above) clearly shows the cold, fresh shelf water beneath warm, salty ring water. The shelf water is seen well offshore of 100 m where the frontal boundary would be expected in the absence of interaction with the ring.
Computer simulations reproduce the observed phenomenon and reveal the underlying mechanism. The onshore movement of the warm-core ring sharpens the interface between the ring and shelf waters. The subducted flow results from circulation trying to relax the sharpening interface and serves to transport sub mesoscale filaments of shelf water offshore. This offshore flow of subducted shelf water may be a significant exchange mechanism, but has not been well studied. It does not have a surface signature and cannot be seen by satellites.Read More