Undergraduate students at Rutgers University have used still frames extracted from the HD Video camera (CAMHD) to compile time-lapse videos of the hydrothermal vent, under the direction of the OOI Data Team. There are 7 biological scenes of interest, captured during the pan/zoom routine of each video. The students are helping produce metadata by time-stamping each scene of interest in every video file on the archive. The students then ran code provided by the OOI Data Team to produce time-lapse videos and watch the vent change over time at each of the scenes of interest. More videos and additional post-processing techniques will be added over time, using open-access tools.

Scene 1

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Wilcock et al., 16 December 2016

Axial Seamount was chosen as a key site on the Regional Cabled Observatory because it is the most active volcano on the Juan de Fuca Ridge having erupted in 1998, 2011, and 2015 [1-7] and because it has a long history of observations as the site of the first submarine volcanic observatory “NeMO” [1-2; https://www.pmel.noaa.gov/eoi/nemo/index.html]. Axial is also unique because the structure of microbial communities has been examined for over 2 decades, including prior to and immediately following the eruptions [8-11]. Nearly continuous seafloor deformation measurements began in 1998 using battery-powered bottom pressure recorders (BPR’s), augmented by mobile pressure recorders in 2000 [3,12-14]. In 2014, an array of cabled bottom pressure tilt instruments, developed by Chadwick [13,14], were installed within the caldera providing real-time measurements of seafloor inflation caused by magma injection in the subsurface and extremely rapid deflation events coincident with eruptions and draining of the magma chamber [13,14]. In concert, these measurements, coupled with modeling, provide forecasting of when the next eruption may occur [13,14; https://www.pmel.noaa.gov/eoi/axial_blog.html].

The ability to make such forecasts is rare in both terrestrial and submarine environments, however, they are possible at Axial due to the continuous magma supply from the Cobb hotspot plume [12-14]. The subsurface structure of Axial is the best imaged submarine volcano due to multiple seismic imaging programs. In concert, these field programs have resulted in 3-D tomographic imaging of the magmatic system [15-20], providing unparalleled insights into melt distribution and magma flux, which controls seafloor deformation. Two large magma bodies at 1.1 to 2.6 km beneath the seafloor [15-18] and a newly recognized deep 3-5 km wide conduit located 6 km beneath the seafloor have been imaged [18]. The conduit is interpreted to contain a series of stacked melt lenses (sills) with spacings of 300-450 meters, providing melt transport that activated the eruptions in 1998, 2011, and 2015 [18]. The 22-year monitoring of Axial Seamount by Chadwick and Nooner document co-eruption deflation events in the caldera of 2.5-3.2 meters, followed by variable periods of inflation [14]. Based on the long-term time series, the 2015 eruption was forecast within a 1-year time window, seven months in advance of the eruption [14]. Daily updates are provided by the model, and coupled with real-time seismic measurements [e.g. 21], will allow refinement of when the next eruption will occur.

[blockquote]

[1] Embley Jr., R.W., Chadwick, W.W., Clague, D., and Stakes, D., (1999) The 1998 Eruption of Axial Volcano: multibeam anomalies and seafloor observations. Geophysical Research Letters, 26, 2428– 3425.

[2] Embley, R.W., Baker, E.T., (1999) Interdisciplinary group explores seafloor eruption with remotely operated vehicle. Eos Trans. AGU, 80, 213, 219, 222.

[3] Chadwick, W.W., Jr., Nooner, S.L. Zumberge, M.A.. Embley, R.W., Fox, C.G. (2006) Vertical deformation monitoring at Axial Seamount since its 1998 eruption using deep-sea pressure sensors. Journal of Volcanology and Geothermal Research, 150, 323-327.

[4] Chadwick, W.W., Jr., Paduan, J.B., Clague, D.A., Dreyer, B.M., Merle, S.G. Bobbitt, A.M. Bobbitt, Caress, D.W. Caress, Philip, B.T., Kelley, D.S., and Nooner, S. (2016) Voluminous eruption from a zoned magma body after an increase in supply rate at Axial Seamount. Geophysical Research Letters, 43, 12,063-12,070; https://doi. org/10.1002/2016GL071327.

[5] Caress, D. W., Clague, D. A. Paduan, J. B., Martin, J. F., Dreyer, B. M., Chadwick, W.W., Jr., Denny, A., and Kelley, D.S. (2012) Repeat bathymetric surveys at 1-metre resolution of lava flows erupted at Axial Seamount in April 2011. Nature Geoscience, 5(7), 483–488.

[6] Clague, D.A., Dryer, B.M., Paduan, J.B., Martin, J.F., Chadwick, W.W., Caress, D.W., Portner, R.A., Guilderson, T.P., McGann, M.L., Thomas, H., Butterfield, D.A., Embley, R.W. (2013) Geolgoica history of the summit of Axial Seamount, Juan de Fuca Ridge. Geochemistry Geophysics Geosystems, 14 (10), doi: 10.1002/ggge.20240.

[7] Clague, D.A., Paduan, J.B., Caress, D.W., Chadwick, W.W., Jr., Le Saout, M., Dreyer, B.M. and Portner, R.A. (2017) High-resolution AUV mapping and targeted ROV observations of three historic lava flows at Axial Seamount. Oceanography, 30(4), 82–99; https://doi.org/10.5670/oceanog.2017.426

[8] Huber, J.A., Butterfield, D.A., and Baross, J.A. (2003) Bacterial diversity in asubseafloor habitiat following a deep-sea volcanic eruption. FEMS Microbiology Ecology, 43, 393-409.

[9] Opatkiewicz, A.D., Butt4erfield, D.A., and Baross, J.A. (2009) Individual hydrothermal vents at Axial Seamount harbor distinct subseafloor microbial communities. FEMS Microbiology Ecology, 70, 413-424. doi.org/10.1111/j.1574-6941.2009.00747.x.

[10] Meyer, J.L., Akerman, N.H., Proskurowski, G., and Huber, J.A. (2013) Microbial characterization of post-eruption “snowblower” vents at Axial Seamount, Juan de Fuca Ridge. Frontiers in Microbiology, doi.org/10.3389/fmicb.2013.00153.

[11] Spietz, R.L., Butterfield, D.A., Buck, N.J., Larson, B.L., Chadwick, W.W., Jr., Walker, S.L., Kelley, D.S. and Morris, R.M. (2018) Deep-sea volcanic eruptions create unique chemical and biological linkages between the subsurface lithosphere and the oceanic hydrosphere. Oceanography, 31, 128-135; doi.org/10.5670/oceanog.2018.120.

[12] Nooner, S.L., and Chadwick, W.W., Jr., (2009) Volcanic inflation measured in the caldera of Axial Seamount: Implications for magma supply and future eruptions. Geochemistry, Geophysics, Geosystems, 10(2), doi.org/10.1029/2008GC002315.

[13] Nooner, S.L., and Chadwick, W.W. Jr. (2016) Inflation- predictable behavior and co-eruption deformation at Axial Seamount. Science, 354, 1399-1403; https://doi.org/10.1126/ science.aah4666.

[14] Chadwick, W.W., Jr., Nooner, S.L., and Lau, T.K.A. (2019) Forecasting the next eruption at Axial Seamount based on an inflation-predictable pattern of deformation. American Geophysical Union, Fall Meeting 2019, OS51B-1489.

[15] Arnulf, A. F., Harding, A. J., Kent, G. M., Carbotte, S. M., Canales, J. P., and Nedimovic, M. R. (2014) Anatomy of an active submarine volcano. Geology, 42(8), 655–658. https://doi.org/10.1130/G35629.1

[16] Arnulf, A.F., Harding, A.J., Kent, G.M., and Wilcock, W.S.D. (2018) Structure, seismicity and accretionary processes at the hot-spot influenced Axial Seamount on the Juan de Fuca Ridge. Journal of Geophysical Research, 10.1029/2017JB015131.

[17] Carbotte, S. M., Nedimovic, M. R., Canales, J. P., Kent, G. M., Harding, A. J., and Marjanovic, M. (2008) Variable crustal structure along the Juan de Fuca Ridge: Influence of on-axis hot spots and absolute plate motions. Geochemistry, Geophysics, Geosystems, 9, Q08001. doi.org/10.1029/2007GC001922.

[18] Carbotte, S.M., Arnulf, A., Spiegelman, M., Lee, M., Harding, A., Kent, G., Canales, J.P., and Nedimovic, M., Stacked sills forming a deep melt-mush feeder conduit beneath Axial Seamount. Geology, 48, (7) 693-697. https://doi.org/10.1130/G47223.1.

[19] West, M., Menke, W., and Tolstoy, M. (2003) Focused magma supply at the intersection of the Cobb hotspot and the Juan de Fuca ridge. Geophysical Research Letters, 30(14), 1724. https://doi.org/10.1029/2003GL017104.

[20] West, M., Menke, W., Tolstoy, M., Webb, S., and Sohn, R. (2001). Magma storage beneath Axial volcano on the Juan de Fuca mid-ocean ridge. Nature, 413(6858), 833–836. doi.org/10.1038/35101581.

[21] Wilcock, W.S.D., Tolstoy, M., Waldhauser, F., Garcia, C., Tan, Y.J., Bohnenstiehl, D.R., Caplan-Auerbach, J., Dziak, R., Arnulf, A.F., and Mann, M.E. (2016) Seismic constraints on caldera dynamics from the 2015 Axial Seamount eruption. Science, 354, 1395-399; https:// doi .org/10.1126 /science.aah5563.

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In July, the OOI CGSN operations team completed another “refresh” of the Pioneer glider fleet. The nominal lifetime for OOI coastal gliders (battery limited) is 90 days. The fleet is refreshed by recovery of exhausted gliders and deployment of refurbished gliders with fresh batteries.

The Coastal Pioneer Array is designed to have 6 Coastal Gliders deployed at a time.  Each glider traverses a distinct path within and around the Pioneer Array, sampling an area measuring over 24,000 km2, roughly the size of New Hampshire.

The first three Pioneer Array Coastal Gliders were deployed just over two years ago in May 2014. The map on the right shows a composite of the tracks of all the gliders deployed at Pioneer since those initial deployments.

The impressive results of glider piloting in the complex coastal environment are evidenced by the match between the composite tracks (right) and the planned tracks (left). The tracks that diverge from the plan show the difficulty of maintaining the glider navigation in the face of severe weather and strong currents.

On average, each of the 25 gliders, for which data are shown, were deployed for a duration of 66 days and travelled a distances of approximately 1200 km (750 miles).  The longest deployment was 118 days and the glider travelled a distance of 2,230 km (or 1,400 miles). That is roughly the same as driving halfway across the United States!

Congrats to the Pioneer team on a job well done. This is just the beginning!

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[caption id="attachment_10832" align="alignright" width="276"]Pioneer Array gliders sample along five glider tracks off the coast of New England. The x- and y-axis are latitude and longitude in decimal degrees. Pioneer Array mooring sites are represented by circles. Boundaries of the glider and AUV operating areas are represented by the blue and red dashed lines, respectively. The five glider tracks are represented by the solid color lines: -Eastern Boundary (EB) green -Frontal Zone (FZ) red. Note: two gliders occupy this track -Slope Sea: SS-1 blue; SS-2 cyan -Gulf Stream (GS) gray Pioneer Array gliders sample along five glider tracks off the coast of New England. The x- and y-axis are latitude and longitude in decimal degrees. Pioneer Array mooring sites are represented by circles. Boundaries of the glider and AUV operating areas are represented by the blue and red dashed lines, respectively. The five glider tracks are represented by the solid color lines:
-Eastern Boundary (EB) green
-Frontal Zone (FZ) red. Note: two gliders occupy this track
-Slope Sea: SS-1 blue; SS-2 cyan
-Gulf Stream (GS) gray[/caption]

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[caption id="attachment_10715" align="aligncenter" width="507"]Pioneer-gliders-all Each line represents the path of one glider. Glider symbols are the last location of the glider before recovery, green dots represent deployment locations.[/caption]

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Because of the great diversity of the sensor types deployed by the OOI, it is understood that the familiarity and knowledge of the OOI program scientists and the data team members may not be sufficient to fully investigate and evaluate all types of data being collected. In order to validate the data from these instruments, we reached out to the experts in the field, or as we like to call them “SMEs” (Subject Matter Experts).

For this task, the OOI team asked the SMEs to take a segment of raw data from a specific instrument, and to apply their knowledge and processing tools together with the requisite calibration, sampling, and metadata to produce a calibrated, engineering units version of the data and assess its validity. Assessing validity means answering whether or not the instrument is working properly and yielding data that is realistic. It also means examining whether or not the sampling protocol implemented for the deployment is appropriate to achieve the scientific goals of deploying that instrument.

One of the instruments examined was the WET Labs AC-S Spectrophotometer deployed on the Endurance Array Washington Offshore Surface Mooring on the west coast. Our SME for this instrument was Emmanuel Boss (University of Maine), an expert in the use of optical instrumentation to study the properties of material suspended in seawater.

With the data team’s help, Dr. Boss verified 1.5 months of data (April-May 2015) at this site with successful results. He was able to process and plot the data using the raw data and vendor calibration files from the AC-S, salinity and temperature from a collocated CTD data to correct absorption and attenuation median spectra and scattering, and data from a collocated fluorometer to cross-check the chlorophyll and POC results.

Consistency between the sensors suggests that they did not foul during the deployment. Not only did his results show that accurate data was being produced by all the sensors in question, but the AC-S (an extremely sensitive instrument normally deployed for very short periods of time) did not drift noticeably during the deployment period, a notable achievement.

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[caption id="attachment_10536" align="alignnone" width="500"]POC derived from AC-S (blue, 380 x cp650) and from the WETLabs fluorometer backscattering coefficient (red, 100 x 380 x bb). POC derived from AC-S (blue, 380 x cp650) and from the WETLabs fluorometer backscattering coefficient (red, 100 x 380 x bb).[/caption]
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[caption id="attachment_10535" align="alignleft" width="500"]Chlorophyll based on AC-S (blue) and on a collocated WETLabs fluorometer (red, calibration x 0.5). Chlorophyll based on AC-S (blue) and on a collocated WETLabs fluorometer (red, calibration x 0.5).[/caption]
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Dr. Boss stated “The fact that we can do this closure exercise gives me confidence that we should be able to see when fouling or drift become an issue.” He did caution that this analysis represented a very small data set at one location at a specific time, under limited ambient temperature and trophic conditions. “While very encouraging, much more work will need to be done to establish how representative it is,” he noted.

The data team is working on using these results to compare with the processed data being delivered by the OOI software, and are continuing to pursue similar efforts for additional instruments with the help of our other volunteer SMEs. We look forward to being able to tell similar success stories for other OOI instruments.

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[media-caption type="image" path="https://eos.org/wp-content/uploads/2016/06/ooi-inshore-surface-mooring-deployed-800x600.jpg" alt="An Ocean Observatories Initiative (OOI) inshore surface mooring is deployed in June 2015 off the coast of Newport, Oreg., from Oregon State University's (OSU) R/V Pacific Storm. In the background, a team on OSU's R/V Elakha is deploying an OOI underwater glider. Photo Credit: Andy Cripe, Corvallis Gazette-Times" link="#"]
An Ocean Observatories Initiative (OOI) inshore surface mooring is deployed in June 2015 off the coast of Newport, Oreg., from Oregon State University’s (OSU) R/V Pacific Storm. In the background, a team on OSU’s R/V Elakha is deploying an OOI underwater glider. Photo Credit: Andy Cripe, Corvallis Gazette-Times
[/media-caption]

(From EOS, 97) By Robinson W. Fulweiler, Glen Gawakiewicz, and Kristen A. Davis

The coastal ocean provides critical services that yield both ecological and economic benefits. Its dynamic nature, however, makes it a most challenging environment to study. Recently, a better understanding of the coupled physical, chemical, geological, and biological processes that characterize the coastal ocean became more attainable.

Ocean Observatories Initiative systems were fully commissioned as of the end of 2015.

Last January, the Ocean Observatories Initiative (OOI), a program of the National Science Foundation (NSF), held a workshop in Washington, D. C., to acquaint potential users with the capabilities offered by the OOI systems, which were fully commissioned as of the end of 2015. A future workshop is planned for this fall on the West Coast.

OOI maintains two coastal ocean arrays: the Pioneer Array in the northwest Atlantic and the Endurance Array in the northeast Pacific. Each has a series of fixed moorings spanning the continental shelf, as well as mobile assets—underwater gliders and propeller-driven autonomous underwater vehicles.

Together, these observatories are capable of resolving coastal ocean processes across a range of temporal and spatial scales. Such data are critical for understanding nutrient and carbon cycling, controls on the abundance of marine organisms, and the effects of long-term warming and extreme weather events.

At the workshop, Jack Barth (Oregon State University) and Glen Gawarkiewicz (Woods Hole Oceanographic Institution) presented preliminary results of recent studies and data collection efforts, stressing the rapid, ongoing changes in coastal ocean temperatures in the U.S. West and East Coast shelf and slope systems. Other participants discussed connections between physics and water column nutrients, the temporal variability of key shelf currents, and the role of OOI data in assessing biodiversity.

A key outcome of the workshop was the introduction of the OOI data portal, where participants acquired firsthand experience in data querying, plotting, and downloading of OOI data. Additionally, participants had numerous opportunities to provide feedback to the OOI Cyber Infrastructure Team.

Anyone can sign up for an account to gain access to OOI data. These data are now available for plotting on the OOI data portal, and select data streams are also available. These sites will be updated with additional data and downloading formats as they become available.

OOI has entered a new phase of community engagement where scientists and educators are encouraged to use the data, provide feedback on data access ease and quality, and, in the process, expand our understanding of coastal oceans.

NSF program managers from all relevant disciplines expressed their support for the arrays. Additionally, we learned the details of how to submit proposals related to OOI data, and all the proposal submission information is available on the OOI website. Workshop participants also learned about the OOI education portal, which can bring cutting-edge ocean data and ocean science concepts to classrooms and informal science education sites.
The message from NSF was clear—OOI has entered a new phase of community engagement where scientists and educators are encouraged to use these data, provide feedback on data access ease and quality, and, in the process, expand our understanding of coastal oceans. A new era is approaching in which integrated ocean observatories will help stimulate innovative science and educational partnerships at the same time they enhance our ability to understand the changes occurring in our coastal oceans.

Jack Barth and Chris Edwards contributed to the writing of this summary. We thank NSF for sponsoring this workshop and the University-National Oceanographic Laboratory System for organizing the event, with a special thanks to Larry Atkinson and Annette DeSilva for their efforts. We also thank the workshop participants and the OOI Cyber Infrastructure Team for their continued work.

—Robinson W. Fulweiler, Department of Earth and Environment and Department of Biology, Boston University, Boston, Mass.; email: rwf@bu.edu; Glen Gawakiewicz, Woods Hole Oceanographic Institution, Woods Hole, Mass.; and Kristen A. Davis, Department of Civil and Environmental Engineering, University of California, Irvine

Citation: Fulweiler, R. W., G. Gawakiewicz, and K. A. Davis (2016), Ocean Observatories Initiative expands coastal ocean research, Eos, 97, doi:10.1029/2016EO054187. Published on 20 June 2016.

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Ocean robots installed off the coast of Massachusetts have helped scientists understand a previously unknown process by which warm Gulf Stream water and colder waters of the continental shelf exchange. The process occurs when offshore waters, originating in the tropics, intrude onto the Mid-Atlantic Bight shelf and meet the waters originating in regions near the Arctic. This process can greatly affect shelf circulation, biogeochemistry and fisheries.

In 2006, scientists using satellite imagery observed an elongated body of warm water from a Gulf Stream warm-core ring intruding along the shelf edge, extending hundreds of miles from Massachusetts towards Cape Hatteras, NC.

“A lot of people were surprised by this,” said Weifeng ‘Gordon’ Zhang, associate scientist at Woods Hole Oceanographic Institution (WHOI), and lead author of the study published today in Geophysical Research Letters. “Normally, the Gulf Stream water, which is very warm and buoyant, doesn’t come in direct contact with the water on the continental shelf, which is much colder. There is a cascade of potential implications that need further study.”

Until now, scientists had been unable to study the phenomenon because satellites can only sense the ocean surface, and no data about the structure of the intrusion water below the surface were available. However, in April 2014, water column data in this area became available from preliminary deployments from the National Science Foundation-funded Ocean Observatories Initiative (OOI). Specifically, autonomous vehicles called “gliders” that collect data along a pre-defined path in the ocean, were deployed at the OOI Pioneer Array site south of Cape Cod. Zhang and his colleagues used preliminary glider data, collected from April through June 2014 and publicly available on the OOI website, to generate the first profile of the complex, layered masses of water at this vital point in the ocean.

“The edge of the continental shelf is a key location where dense, nutrient rich water ‘upwells’ to the surface, stimulating growth at the base of the food web,” said co-author Glen Gawarkiewicz, a senior scientist at WHOI. “This water is normally sandwiched between colder, fresher water on the shelf and warmer Gulf Stream waters offshore. Understanding changes in this region has important societal and economic implications.”

Satellite imagery shows five similar-looking intrusion events have occurred between 2007-2014 in the winter and spring seasons. Zhang and Gawarkiewicz have dubbed the events “Pinocchio’s Nose Intrusions” (PNI) because the warm water intrudes onto the shelf and continues to “grow” for hundreds of miles, moving in the opposite direction from the northeastward movement of the Gulf Stream.

Until this new research was conducted, one proposed explanation was that the warm waters were swept up in the shelf break jet, a current that moves toward the southwest direction along the shelf edge. Zhang calls this “the deception or lie” of the Pinocchio’s Nose Intrusion. “If the intrusion was caused by the shelfbreak jet,” said Zhang, “this feature would most likely be a very thin, superficial feature on the surface.” In contrast, thanks to the data collected by the OOI Pioneer Array gliders before and after the PNI formed, the scientists determined these intrusions are nearly 100 meters deep, extending almost to the seafloor.

Rotating warm core rings form in the deep ocean and eventually pinch off from the Gulf Stream, heading in a northwest direction onto the shallower continental slope. The outer limbs of the rings hit the slope first, and are squeezed by the rising sea floor. Once reaching the shelf, they follow the shelf edge extending to the southwest forming the long nose shape. Eventually, the extension stops, and thin filaments coming out of the north side of the nose penetrate further onto the shelf.

The OOI Pioneer Array data also allowed scientists to understand the complexities of what is driving the density of the various water masses at this unique location. Under normal conditions, the density in the region is controlled by the salinity. The shelf water is fresher than offshore water and therefore more buoyant than saltier offshore water. However, during a PNI event, the shelf water is less buoyant than the offshore water because of a huge temperature difference–approximately 25-30 degrees Fahrenheit–between the shelf waters and the intrusion waters.

“Because the Gulf Stream water is so outrageously warm, density now is controlled by the temperature, and the intrusion water is more buoyant, despite being saltier,” said Zhang.

The changes in temperature, density and circulation all have major implications for the fisheries in the area.

“I showed the glider data to a group of commercial fisherman back in April, in Rhode Island, and they were very surprised,” said Gawarkiewicz. “They couldn’t believe the temperature can change by that much, that quickly.”

The scientists believe the PNI process might assist in the transport of young fish, like American eel, across the shelfbreak barrier and onto the shelf, where they can swim toward coastal estuaries. For American eels, this is an important step of their reproductive migration journey and crucial for their survival. The baby eels have to make it from the spawning ground in the tropics to their estuarine and freshwater habitats on the US northeast coast in the first year of their life. The direct intrusion of the Gulf Stream water onto the shelf can help them reach their destination without being swept away, and may increase their survival rate. But for other species, the intrusion might bring in the low nutrient Gulf Stream surface water and suppress the upwelling of cold, dense, nutrient-rich water, and thereby reduce biological productivity in a region that is otherwise known for its fertile fishing grounds.

“I just find it extraordinary that the Pioneer Array gliders were out for a month, and we have already identified a new shelf break exchange process,” said Gawarkiewicz. “It just goes to show how much more we have to learn in the shelf-wide ecosystem.”

“I am very proud of our WHOI scientists, Weifeng Zhang and Glen Gawarkiewicz,” said Representative William Keating (D-MA). “Their discovery serves as a reminder of the critical need for continued and more frequent ocean observation, as well as the interconnectedness of the health of our oceans and the health of our marine ecosystems. WHOI has long been an international leader in oceanography, with groundbreaking research unveiling countless discoveries that have changed the field. This breakthrough is no different. As we continue to study and understand the magnitude and impacts of the changes of ocean temperatures and circulation, WHOI’s research and resources will be invaluable.”

###

The research was funded by the National Science Foundation.

The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit http://www.whoi.edu.

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Ocean robots installed off the coast of Massachusetts have helped scientists understand a previously unknown process by which warm Gulf Stream water and colder waters of the continental shelf exchange.

[media-caption type="image" path="/wp-content/uploads/2015/11/100180_web.jpg" alt="Satellite imagery shows the exchange of warm core ring water (red) with the colder continental shelf waters (blue)." link="#"]Satellite imagery shows the exchange of warm core ring water (red) with the colder continental shelf waters (blue). Satellite imagery, however, could not help scientists determine the underlying process for the warm water intrusion; instead they used data from ocean robots or “gliders” recently installed off the coast of Massachusetts. The scientists have dubbed the events “Pinocchio’s Nose Intrusions” (PNI) because the warm intruding water continues to ‘grow’ for hundreds of miles, moving in the opposite direction from the northward movement of the Gulf Stream. (Illustration by Jack Cook, Woods Hole Oceanographic Institution)[/media-caption]

(From Eurekalert.org) — The process occurs when offshore waters, originating in the tropics, intrude onto the Mid-Atlantic Bight shelf and meet the waters originating in regions near the Arctic. This process can greatly affect shelf circulation, biogeochemistry and fisheries.

In 2006, scientists using satellite imagery observed an elongated body of warm water from a Gulf Stream warm-core ring intruding along the shelf edge, extending hundreds of miles from Massachusetts towards Cape Hatteras, NC.

“A lot of people were surprised by this,” said Weifeng ‘Gordon’ Zhang, associate scientist at Woods Hole Oceanographic Institution (WHOI), and lead author of the study published today in Geophysical Research Letters. “Normally, the Gulf Stream water, which is very warm and buoyant, doesn’t come in direct contact with the water on the continental shelf, which is much colder. There is a cascade of potential implications that need further study.”

Until now, scientists had been unable to study the phenomenon because satellites can only sense the ocean surface, and no data about the structure of the intrusion water below the surface were available. However, in April 2014, water column data in this area became available from preliminary deployments from the National Science Foundation-funded Ocean Observatories Initiative (OOI). Specifically, autonomous vehicles called “gliders” that collect data along a pre-defined path in the ocean, were deployed at the OOI Pioneer Array site south of Cape Cod. Zhang and his colleagues used preliminary glider data, collected from April through June 2014 and publicly available on the OOI website, to generate the first profile of the complex, layered masses of water at this vital point in the ocean.

“The edge of the continental shelf is a key location where dense, nutrient rich water ‘upwells’ to the surface, stimulating growth at the base of the food web,” said co-author Glen Gawarkiewicz, a senior scientist at WHOI. “This water is normally sandwiched between colder, fresher water on the shelf and warmer Gulf Stream waters offshore. Understanding changes in this region has important societal and economic implications.”

Satellite imagery shows five similar-looking intrusion events have occurred between 2007-2014 in the winter and spring seasons. Zhang and Gawarkiewicz have dubbed the events “Pinocchio’s Nose Intrusions” (PNI) because the warm water intrudes onto the shelf and continues to “grow” for hundreds of miles, moving in the opposite direction from the northeastward movement of the Gulf Stream.

Read the full article here: http://www.eurekalert.org/pub_releases/2015-09/whoi-gsr092915.php

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