Science Highlights
A Marine Heat Wave Identified on the New England Shelf
From 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 MoreTime Series Allows Investigation of Wind Forcing and Physical and Bio-Optical Variability
From 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 MoreAnomalous Shallow Strong Currents Off the Oregon Margin
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 MoreFirst Continuous Temperature Measurements Spanning >2600 m water depth
Deep temperature modulations at Axial Base
From 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 MoreNew Estimate of Boundary Current Transport
From 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 MoreStrong Variability in Irminger Sea Winter Heat Loss Measured
From Josey et al., 18 December 2018
A recent paper by Josey et al. [1] 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 [2], [3], but the amount of heat lost is poorly known because winter measurements are difficult to obtain in the harsh environment [1].
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 [4], [5]. Josey et al. [1] 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][1] 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
[2] 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
[3] 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
[4] 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
[5] 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.
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Unique Offshore Transport of Shelf Water by Subduction Identified
From 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 MoreHypoxic Conditions Over the Oregon Shelf Respond to Wind Forcing on Time Scales of Days
From Barth et al., 9 February 2018
In recent years, hypoxic and even anoxic events have regularly occurred off Washington and Oregon as they have in upwelling regions worldwide [1, 2]. The OOI Endurance Array’s location, platforms and sensors were designed to address major OOI Science Themes with a particular focus on Hypoxia on Continental Shelves and Shelf/Slope Exchange [3]. Since its first full deployment in April 2015, the Endurance Array has maintained oxygen sensors at 6 fixed locations near the surface and near the bottom over the Washington and Oregon shelf and slope. Similar oxygen sensors are found on Endurance Array profilers and gliders and across other OOI arrays.
OOI marine operators, systems engineers and data team members have worked together to continually improve the quality of the OOI dissolved oxygen data products. We have worked with the vendor to improve their calibration of sensors; have compared data to physical samples [4]; and have implemented a UV-based biofouling mitigation [5].
Science Highlight: OOI Endurance Array data [6] describe low-oxygen events off central Oregon. Data from July 2017 illustrate variability on time scales of days as the wind-driven upwelling circulation advects low oxygen waters back and forth across the shelf. (Figure 1).
During this time, near-bottom oxygen levels at the OOI Oregon Inshore Surface mooring were often below the hypoxia threshold. When winds blow to the south, the near-bottom temperature decreases due to coastal upwelling, with a slight lag relative to the wind. During these events, near-bottom oxygen usually decreases (e.g., 23-25 July). Conversely, during low or northward winds the near-bottom temperature and oxygen increase rapidly. These changes are consistent with the upwelling circulation drawing near-bottom cold water low in dissolved oxygen toward the coast during upwelling and pushing warm water containing more oxygen down and away from the coast near the bottom during downwelling. The dissolved oxygen does not follow the winds or temperature as clearly as temperature follows the wind because there are the additional biological processes of photosynthesis and microbial decay that raise or lower dissolved oxygen levels, respectively.
Since this report [6], researchers continue to use OOI data to characterize hypoxia in summer 2018. There is also increasing interest in, and use of, OOI data by mission-oriented agencies such as the Oregon Department of Fish and Wildlife.
[blockquote][1] Grantham, B. A., Chan, F., Nielsen, K.J., Fox, D.S., Barth, J.A., Huyer, A., Lubchenco, A., Menge, B.A. (2004). Upwelling-driven nearshore hypoxia signals ecosystem and oceanographic changes in the northeast Pacific. Nature, 429, 749-754. DOI: 10.1038/nature02605.
[2] Chan, F., Barth, J.A., Lubchenco, J., Kirincich, A., Weeks, H., Peterson, W.T., Menge, B.A. (2008). Novel emergence of anoxia in the California Current System. Science, 319, 920, DOI: 10.1126/science.1149016
[3] ORION Executive Steering Committee (2007). Ocean Observatories Initiative Scientific Objectives and Network Design: A Closer Look. Joint Oceanographic Institutions, Inc. Washington, DC.
[4] Holm, C., R.T. Rohrer, E.P. Dever, and J.P. Fram (2018) Quality Assessment of Moored Near Surface Instrument Time Series on the OOI Endurance Array, Abstract IS14A-2541 presented at 2018 Ocean Sciences Meeting, Portland, OR, 12-16 Feb.
[5] Wingard, C.E., R.A. Desiderio, J.P. Fram, and E.P. Dever (2018) Time Series Measurements of Inherent and Apparent Optical Properties from the OOI Endurance Array, Abstract IS14A-2543 presented at 2018 Ocean Sciences Meeting, Portland, OR, 12-16 Feb.
[6] Barth, J. A., J. Fram, E. P. Dever, C. Risien, C. Wingard, R. W. Collier, and T. D. Kearney, 2018. Warm blobs, low-oxygen events and an eclipse: The Ocean Observatories Initiative Endurance Array captures them all, Oceanography 31(1): 90-97, https://doi.org/10.5670/oceanog.2018.114.
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Glider Observations Provide Insight into Spatial Patterns in Satellite Bio-Optical Measurements
From Henderikx et al., 9 February 2018
Hendrikx Freitas et al., 2018 compare satellite and Endurance Array glider estimates of chromophoric dissolved organic matter (CDOM) to characterize seasonal patterns and latitudinal and cross-shore gradients in particle concentrations between the Washington and Oregon shelves. While the Oregon and Washington shelves are both highly productive regions of the northern California Current Ecosystem, there are significant differences in the physical processes, with the central Washington shelf generally subject to weaker upwelling and a stronger Columbia River influence. The difference in physical forcing is reflected in satellite estimates of chlorophyll, which show higher concentrations off the Washington coast.
The conclusions from satellites contrast with in situ observations from gliders. Despite the differences in physical forcing, Henderikx et al., 2018 find OOI glider fluorescence based measurements of chlorophyll to be similar in magnitude across the Oregon and Washington shelves. Their research suggests that latitudinal differences in CDOM may be a partial explanation for perceived trends in satellite-derived chlorophyll. The OOI gliders gather simultaneous chlorophyll and CDOM fluorescence from an integrated three-channel sensor. While the glider observations indicate similar levels of chlorophyll fluorescence, they also show an increased presence of suspended sediments and CDOM off WA. The OOI observations, although temporally limited, indicate potential contamination of satellite retrievals of chlorophyll due to CDOM and suspended materials in the water column, particularly off the WA shelf, that should caution further attribution of satellite chlorophyll signals to differences in production.
Read MoreAxial Seamount: First Volcano Where a Submarine Eruption May Be Predicted
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), https://doi.org/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. https://doi.org/10.1111/j.1574-6941.2009.0074.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://science.sciencemag.org/content/354/6318/1399
[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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