Stockwell Dean A.

No Thumbnail Available
Last Name
Stockwell
First Name
Dean A.
ORCID

Filters

2019 - 2019 3 2020 - 2024 3
4 2
6
Reset filters

Settings

Search Results

Now showing 1 - 6 of 6
  • Article
    Water mass evolution and circulation of the northeastern Chukchi Sea in summer: Implications for nutrient distributions
    (American Geophysical Union, 2019-06-07) Lin, Peigen ; Pickart, Robert S. ; McRaven, Leah T. ; Arrigo, Kevin R. ; Bahr, Frank ; Lowry, Kate E. ; Stockwell, Dean A. ; Mordy, Calvin W.
    Synoptic and historical shipboard data, spanning the period 1981–2017, are used to investigate the seasonal evolution of water masses on the northeastern Chukchi shelf and quantify the circulation patterns and their impact on nutrient distributions. We find that Alaskan coastal water extends to Barrow Canyon along the coastal pathway, with peak presence in September, while the Pacific Winter Water (WW) continually drains off the shelf through the summer. The depth‐averaged circulation under light winds is characterized by a strong Alaskan Coastal Current (ACC) and northward flow through Central Channel. A portion of the Central Channel flow recirculates anticyclonically to join the ACC, while the remainder progresses northeastward to Hanna Shoal where it bifurcates around both sides of the shoal. All of the branches converge southeast of the shoal and eventually join the ACC. The wind‐forced response has two regimes: In the coastal region the circulation depends on wind direction, while on the interior shelf the circulation is sensitive to wind stress curl. In the most common wind‐forced state—northeasterly winds and anticyclonic wind stress curl—the ACC reverses, the Central Channel flow penetrates farther north, and there is mass exchange between the interior and coastal regions. In September and October, the region southeast of Hanna Shoal is characterized by elevated amounts of WW, a shallower pycnocline, and higher concentrations of nitrate. Sustained late‐season phytoplankton growth spurred by this pooling of nutrients could result in enhanced vertical export of carbon to the seafloor, contributing to the maintenance of benthic hotspots in this region.
  • Article
    Three-dimensional structure of a cold-core Arctic eddy interacting with the Chukchi slope current
    (American Geophysical Union, 2019-11-11) Scott, Ryan M. ; Pickart, Robert S. ; Lin, Peigen ; Münchow, Andreas ; Li, Min ; Stockwell, Dean A. ; Brearley, J. Alexander
    A rapid, high‐resolution shipboard survey, using a combination of lowered and expendable hydrographic measurements and vessel‐mounted acoustic Doppler current profiler data, provided a unique three‐dimensional view of an Arctic anti‐cyclonic cold‐core eddy. The eddy was situated 50‐km seaward of the Chukchi Sea shelfbreak over the 1,000 m isobath, embedded in the offshore side of the Chukchi slope current. The eddy core, centered near 150‐m depth, consisted of newly ventilated Pacific winter water which was high in nitrate and dissolved oxygen. Its fluorescence signal was due to phaeopigments rather than chlorophyll, indicating that photosynthesis was no longer active, consistent with an eddy age on the order of months. Subtracting out the slope current signal demonstrated that the eddy velocity field was symmetrical with a peak azimuthal speed of order 10 cm s−1. Its Rossby number was ~0.4, consistent with the fact that the measured cyclogeostrophic velocity was dominated by the geostrophic component. Different scenarios are discussed regarding how the eddy became embedded in the slope current, and what the associated ramifications are with respect to eddy spin‐down and ventilation of the Canada Basin halocline.
  • Dataset
    Cruise Event Logs from 15 vessels for 116 U.S. GLOBEC cruises from 1997-2004 in the Northeast Pacific and Gulf of Alaska areas (NEP program)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2021-06-08) Barth, Jack ; Boldt, Jennifer L. ; Brodeur, Richard D ; Cokelet, Edward D. ; Cowles, Timothy ; Danielson, Seth L. ; Emmett, Robert L ; Farley, Edward V. ; Fleischbein, Jane ; Haldorson, Lewis J ; Hopcroft, Russell R. ; Huyer, Adriana ; Janout, Markus A. ; Kachel, Nancy ; Kondzela, Chris ; Moss, Jamal Hasan ; Musgrave, Dave ; Napp, Jeffrey ; Noskov, Jackie Popp ; Peterson, William T. ; Piccolo, Jack ; Royer, Thomas C. ; Smith, Robert ; Stockwell, Dean A. ; Strom, Suzanne ; Thornton, Sarah ; Tynan, Cynthia ; Weingartner, Thomas J. ; Coyle, Kenneth O ; Keister, Julie E. ; Sherr, Evelyn
    Cruise Event Logs from 15 vessels for 116 U.S. GLOBEC cruises from 1997-2004 in the Northeast Pacific and Gulf of Alaska areas For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/2341
  • Article
    Spatiotemporal transitions in Pseudo-nitzschia species assemblages and domoic acid along the Alaska coast
    (Public Library of Science, 2023-03-22) Hubbard, Katherine A. ; Villac, Maria Célia ; Chadwick, Christina ; DeSmidt, Alexandra A. ; Flewelling, Leanne ; Granholm, April ; Joseph, Molly ; Wood, Taylor ; Fachon, Evangeline ; Brosnahan, Michael L. ; Richlen, Mindy ; Pathare, Mrunmayee ; Stockwell, Dean ; Lin, Peigen ; Bouchard, Josée N. ; Pickart, Robert ; Anderson, Donald M.
    The toxic diatom genus Pseudo-nitzschia is distributed from equatorial to polar regions and is comprised of >57 species, some capable of producing the neurotoxin domoic acid (DA). In the Pacific Arctic Region spanning the Bering, Chukchi, and Beaufort seas, DA is recognized as an emerging human and ecosystem health threat, yet little is known about the composition and distribution of Pseudo-nitzschia species in these waters. This investigation characterized Pseudo-nitzschia assemblages in samples collected in 2018 during summer (August) and fall (October-November) surveys as part of the Distributed Biological Observatory and Arctic Observing Network, encompassing a broad geographic range (57.8° to 73.0°N, -138.9° to -169.9°W) and spanning temperature (-1.79 to 11.7°C) and salinity (22.9 to 32.9) gradients associated with distinct water masses. Species were identified using a genus-specific Automated Ribosomal Intergenic Spacer Analysis (ARISA). Seventeen amplicons were observed; seven corresponded to temperate, sub-polar, or polar Pseudo-nitzschia species based on parallel sequencing efforts (P. arctica, P. delicatissima, P. granii, P. obtusa, P. pungens, and two genotypes of P. seriata), and one represented Fragilariopsis oceanica. During summer, particulate DA (pDA; 4.0 to 130.0 ng L-1) was observed in the Bering Strait and Chukchi Sea where P. obtusa was prevalent. In fall, pDA (3.3 to 111.8 ng L-1) occurred along the Beaufort Sea shelf coincident with one P. seriata genotype, and south of the Bering Strait in association with the other P. seriata genotype. Taxa were correlated with latitude, longitude, temperature, salinity, pDA, and/or chlorophyll a, and each had a distinct distribution pattern. The observation of DA in association with different species, seasons, geographic regions, and water masses underscores the significant risk of Amnesic Shellfish Poisoning (ASP) and DA-poisoning in Alaska waters.
  • Dataset
    Cruise Event Logs from 15 vessels for 116 U.S. GLOBEC cruises from 1997-2004 in the Northeast Pacific and Gulf of Alaska areas (NEP program)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-02-22) Barth, Jack ; Boldt, Jennifer L ; Brodeur, Richard D ; Cokelet, Edward D. ; Cowles, Timothy ; Danielson, Seth L. ; Emmett, Robert L ; Farley, Edward V. ; Fleischbein, Jane ; Haldorson, Lewis J ; Hopcroft, Russell R. ; Huyer, Adriana ; Janout, Markus A. ; Kachel, Nancy ; Kondzela, Chris ; Moss, Jamal Hasan ; Musgrave, Dave ; Napp, Jeffrey ; Noskov, Jackie Popp ; Peterson, William T. ; Piccolo, Jack ; Royer, Thomas C. ; Smith, Robert ; Stockwell, Dean A. ; Strom, Suzanne ; Thornton, Sarah ; Tynan, Cynthia ; Weingartner, Thomas J. ; Coyle, Kenneth O ; Keister, Julie E. ; Sherr, Evelyn
    Cruise Event Logs from 15 vessels for 116 U.S. GLOBEC cruises from 1997-2004 in the Northeast Pacific and Gulf of Alaska areas For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/2341
  • Article
    Tracking a large-scale and highly toxic Arctic algal bloom: Rapid detection and risk communication
    (Association for the Sciences of Limnology and Oceanography (ASLO), 2024-07-10) Fachon, Evangeline ; Pickart, Robert S. ; Sheffield, Gay ; Pate, Emma ; Pathare, Mrunmayee ; Brosnahan, Michael L. ; Muhlbach, Eric ; Horn, Kali ; Spada, Nathaniel N. ; Rajagopalan, Anushka ; Lin, Peigen ; McRaven, Leah T. ; Lago, Loreley S. ; Huang, Jie ; Bahr, Frank B. ; Stockwell, Dean A. ; Hubbard, Katherine A. ; Farrugia, Thomas J. ; Lefebvre, Kathi A. ; Anderson, Donald M.
    In recent years, blooms of the neurotoxic dinoflagellate Alexandrium catenella have been documented in Pacific Arctic waters, and the paralytic shellfish toxins (PSTs) that this species produces have been detected throughout the food web. These observations have raised significant concerns about the role that harmful algal blooms (HABs) will play in a rapidly changing Arctic. During a research cruise in summer 2022, a massive bloom of A. catenella was detected in real time as it was advected through the Bering Strait region. The bloom was exceptional in both spatial scale and density, extending > 600 km latitudinally, reaching concentrations > 174,000 cells L−1, and producing high-potency PST congeners. Throughout the event, coastal stakeholders in the region were engaged and a multi-faceted community response was mobilized. This unprecedented bloom highlighted the urgent need for response capabilities to ensure safe utilization of critical marine resources in a region that has little experience with HABs.