Danielson Seth

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Danielson

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Seth

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0000-0002-9191-4363

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Mean and seasonal circulation of the eastern Chukchi Sea from moored timeseries in 2013-2014

(American Geophysical Union, 2021-04-30) Tian, Fei ; Pickart, Robert S. ; Lin, Peigen ; Pacini, Astrid ; Moore, G. W. K. ; Stabeno, Phyllis J. ; Weingartner, Thomas J. ; Itoh, Motoyo ; Kikuchi, Takashi ; Dobbins, Elizabeth ; Bell, Shaun ; Woodgate, Rebecca ; Danielson, Seth L. ; Wang, Zhaomin

From late-summer 2013 to late-summer 2014, a total of 20 moorings were maintained on the eastern Chukchi Sea shelf as part of five independent field programs. This provided the opportunity to analyze an extensive set of timeseries to obtain a broad view of the mean and seasonally varying hydrography and circulation over the course of the year. Year-long mean bottom temperatures reflected the presence of the strong coastal circulation pathway, while mean bottom salinities were influenced by polynya/lead activity along the coast. The timing of the warm water appearance in spring/summer is linked to advection along the various flow pathways. The timing of the cold water appearance in fall/winter was not reflective of advection nor related to the time of freeze-up. Near the latitude of Barrow Canyon, the cold water was accompanied by freshening. A one-dimensional mixed-layer model demonstrates that wind mixing, due to synoptic storms, overturns the water column resulting in the appearance of the cold water. The loitering pack ice in the region, together with warm southerly winds, melted ice and provided an intermittent source of fresh water that was mixed to depth according to the model. Farther north, the ambient stratification prohibits wind-driven overturning, hence the cold water arrives from the south. The circulation during the warm and cold months of the year is different in both strength and pattern. Our study highlights the multitude of factors involved in setting the seasonal cycle of hydrography and circulation on the Chukchi shelf.
Monitoring Alaskan Arctic shelf ecosystems through collaborative observation networks

(Oceanography Society, 2022-04-28) Danielson, Seth L. ; Grebmeier, Jacqueline M. ; Iken, Katrin ; Berchok, Catherine L. ; Britt, Lyle ; Dunton, Kenneth ; Eisner, Lisa B. ; Farley, Edward V. ; Fujiwara, Amane ; Hauser, Donna D.W. ; Itoh, Motoyo ; Kikuchi, Takashi ; Kotwicki, Stan ; Kuletz, Kathy J. ; Mordy, Calvin W. ; Nishino, Shigeto ; Peralta-Ferriz, Cecilia ; Pickart, Robert S. ; Stabeno, Phyllis J. ; Stafford, Kathleen M. ; Whiting, Alex V. ; Woodgate, Rebecca

Ongoing scientific programs that monitor marine environmental and ecological systems and changes comprise an informal but collaborative, information-rich, and spatially extensive network for the Alaskan Arctic continental shelves. Such programs reflect contributions and priorities of regional, national, and international funding agencies, as well as private donors and communities. These science programs are operated by a variety of local, regional, state, and national agencies, and academic, Tribal, for-profit, and nongovernmental nonprofit entities. Efforts include research ship and autonomous vehicle surveys, year-long mooring deployments, and observations from coastal communities. Inter-program coordination allows cost-effective leveraging of field logistics and collected data into value-added information that fosters new insights unattainable by any single program operating alone. Coordination occurs at many levels, from discussions at marine mammal co-management meetings and interagency meetings to scientific symposia and data workshops. Together, the efforts represented by this collection of loosely linked long-term monitoring programs enable a biologically focused scientific foundation for understanding ecosystem responses to warming water temperatures and declining Arctic sea ice. Here, we introduce a variety of currently active monitoring efforts in the Alaskan Arctic marine realm that exemplify the above attributes.
Zooplankton catch data from Tucker trawls from CGOA LTOP cruises from the Coastal Gulf of Alaska, Northeast Pacific, 2001-2003 (NEP project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-01-16) Cokelet, Edward D. ; Coyle, Kenneth O ; Danielson, Seth L. ; Farley, Edward V. ; Moss, Jamal Hasan

Zooplankton catch data from Tucker trawls from CGOA LTOP cruises from the Coastal Gulf of Alaska, Northeast Pacific, 2001-2003. 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/3010
AK-LTOP CalVET Net Tow counts and biomass collected from multiple cruises from the Northeast Pacific, 1997-2001 (NEP project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-01-16) Danielson, Seth L. ; Coyle, Kenneth O

AK-LTOP CalVET Net Tow counts and biomass collected from multiple cruises from the Northeast Pacific, 1997-2001. 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/3009
Zooplankton counts for bongo net hauls in the Gulf of Alaska from F/V Great Pacific GP0401-01, GP0401-02 from October to November 2004 (NEP project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-01-16) Cokelet, Edward D. ; Coyle, Kenneth O ; Danielson, Seth L. ; Farley, Edward V.

Zooplankton counts for bongo net hauls in the Gulf of Alaska from F/V Great Pacific GP0401-01, GP0401-02 from October to November 2004. 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/3012
The St. Lawrence polynya and the Bering shelf circulation : new observations and a model comparison

(American Geophysical Union, 2006-09-19) Danielson, Seth L. ; Aagaard, Knut ; Weingartner, Thomas J. ; Martin, S. ; Winsor, Peter ; Gawarkiewicz, Glen G. ; Quadfasel, Detlef R.

Using 14 year-long instrumented moorings deployed south of St. Lawrence Island, along with oceanographic drifters, we investigate the circulation over the central Bering shelf and the role of polynyas in forming and disseminating saline waters over the shelf. We focus also on evaluating the Gawarkiewicz and Chapman [1995] model of eddy production within coastal polynyas. Principal results include: 1) The northern central shelf near-surface waters exhibit westward flow carrying low-salinity waters from the Alaskan coast in fall and early winter, with consequences for water mass formation and biological production. 2) Within the St. Lawrence polynya, the freshening effect of winter advection is about half as large as the salting effect of surface brine flux resulting from freezing. 3) Brine production over the Bering shelf occurs primarily offshore, rather than within coastal polynyas, even though ice production per unit area is much larger within the polynyas. 4) We find little evidence for the geostrophic flow adjustment predicted by recent polynya models. 5) In contrast to the theoretical prediction that dense water from the polynya is carried offshore by eddies, we find negligible cross-shelf eddy density fluxes within and surrounding the polynya and very low levels of eddy energy that decreased from fall to winter, even though dense water accumulated within the polynya and large cross-shore density gradients developed. 6) It is possible that dense polynya water was advected downstream of our array before appreciable eddy fluxes materialized.
Evidence for massive and recurrent toxic blooms of Alexandrium catenella in the Alaskan Arctic

(National Academy of Sciences, 2021-10-04) Anderson, Donald M. ; Fachon, Evangeline ; Pickart, Robert S. ; Lin, Peigen ; Fischer, Alexis D. ; Richlen, Mindy L. ; Uva, Victoria ; Brosnahan, Michael L. ; McRaven, Leah T. ; Bahr, Frank B. ; Lefebvre, Kathi A. ; Grebmeier, Jacqueline M. ; Danielson, Seth L. ; Lyu, Yihua ; Fukai, Yuri

Among the organisms that spread into and flourish in Arctic waters with rising temperatures and sea ice loss are toxic algae, a group of harmful algal bloom species that produce potent biotoxins. Alexandrium catenella, a cyst-forming dinoflagellate that causes paralytic shellfish poisoning worldwide, has been a significant threat to human health in southeastern Alaska for centuries. It is known to be transported into Arctic regions in waters transiting northward through the Bering Strait, yet there is little recognition of this organism as a human health concern north of the Strait. Here, we describe an exceptionally large A. catenella benthic cyst bed and hydrographic conditions across the Chukchi Sea that support germination and development of recurrent, locally originating and self-seeding blooms. Two prominent cyst accumulation zones result from deposition promoted by weak circulation. Cyst concentrations are among the highest reported globally for this species, and the cyst bed is at least 6× larger in area than any other. These extraordinary accumulations are attributed to repeated inputs from advected southern blooms and to localized cyst formation and deposition. Over the past two decades, warming has likely increased the magnitude of the germination flux twofold and advanced the timing of cell inoculation into the euphotic zone by 20 d. Conditions are also now favorable for bloom development in surface waters. The region is poised to support annually recurrent A. catenella blooms that are massive in scale, posing a significant and worrisome threat to public and ecosystem health in Alaskan Arctic communities where economies are subsistence based.
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
Metadata for tucker trawls and bongo net hauls from F/V Great Pacific and R/V Miller Freeman multiple cruises in the Coastal Gulf of Alaska, NE Pacific, 2001-2004 (NEP project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-01-16) Cokelet, Edward D. ; Coyle, Kenneth O ; Danielson, Seth L. ; Farley, Edward V. ; Moss, Jamal Hasan

Metadata for tucker trawls and bongo net hauls from F/V Great Pacific and R/V Miller Freeman multiple cruises in the Coastal Gulf of Alaska, NE Pacific, 2001-2004. 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/3013
A warm jet in a cold ocean

(Nature Research, 2021-04-23) MacKinnon, Jennifer A. ; Simmons, Harper L. ; Hargrove, John ; Thomson, Jim ; Peacock, Thomas ; Alford, Matthew H. ; Barton, Benjamin I. ; Boury, Samuel ; Brenner, Samuel D. ; Couto, Nicole ; Danielson, Seth L. ; Fine, Elizabeth C. ; Graber, Hans C. ; Guthrie, John D. ; Hopkins, Joanne E. ; Jayne, Steven R. ; Jeon, Chanhyung ; Klenz, Thilo ; Lee, Craig M. ; Lenn, Yueng-Djern ; Lucas, Andrew J. ; Lund, Björn ; Mahaffey, Claire ; Norman, Louisa ; Rainville, Luc ; Smith, Madison M. ; Thomas, Leif N. ; Torres-Valdes, Sinhue ; Wood, Kevin R.

Unprecedented quantities of heat are entering the Pacific sector of the Arctic Ocean through Bering Strait, particularly during summer months. Though some heat is lost to the atmosphere during autumn cooling, a significant fraction of the incoming warm, salty water subducts (dives beneath) below a cooler fresher layer of near-surface water, subsequently extending hundreds of kilometers into the Beaufort Gyre. Upward turbulent mixing of these sub-surface pockets of heat is likely accelerating sea ice melt in the region. This Pacific-origin water brings both heat and unique biogeochemical properties, contributing to a changing Arctic ecosystem. However, our ability to understand or forecast the role of this incoming water mass has been hampered by lack of understanding of the physical processes controlling subduction and evolution of this this warm water. Crucially, the processes seen here occur at small horizontal scales not resolved by regional forecast models or climate simulations; new parameterizations must be developed that accurately represent the physics. Here we present novel high resolution observations showing the detailed process of subduction and initial evolution of warm Pacific-origin water in the southern Beaufort Gyre.
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
The Pacific water flow branches in the eastern Chukchi Sea

(Elsevier, 2023-11-10) Pickart, Robert S. ; Lin, Peigen ; Bahr, Frank B. ; McRaven, Leah T. ; Huang, Jie ; Pacini, Astrid ; Arrigo, Kevin Robert ; Ashjian, Carin J. ; Berchok, Catherine L. ; Baumgartner, Mark F. ; Cho, Kyoungho ; Cooper, Lee W. ; Danielson, Seth L. ; Dasher, Doug H. ; Fuiwara, Amane ; Gann, Jeanette C. ; Grebmeier, Jacqueline M. ; He, Jiangfeng ; Hirawake, Toru ; Itoh, Motoyo ; Juranek, Laurie ; Kikuchi, Takashi ; Moore, G. W. Kent ; Napp, Jeffrey M. ; John Nelson, R. ; Nishino, Shigeto ; Statscewich, Hank ; Stabeno, Phyllis J. ; Stafford, Kathleen M. ; Ueno, Hiromichi ; Vagle, Svein ; Weingartner, Thomas J. ; Williams, Bill ; Zimmermann, Sarah L.

The flow of Pacific-origin water across the Chukchi Sea shelf impacts the regional ecosystem in profound ways, yet the two current branches on the eastern shelf that carry the water from Bering Strait to Barrow Canyon – the Alaskan Coastal Current (ACC) and Central Channel (CC) Branch – have not been clearly distinguished or quantified. In this study we use an extensive collection of repeat hydrographic sections occupied at three locations on the Chukchi shelf, together with data from a climatology of shipboard velocity data, to accomplish this. The data were collected predominantly between 2010 and 2020 during the warm months of the year as part of the Distributed Biological Observatory and Arctic Observing Network. The mean sections show that mass is balanced for both currents at the three locations: Bering Strait, Point Hope, and Barrow Canyon. The overall mean ACC transport is 0.34 ± 0.04 Sv, and that of the CC Branch is 0.86 ± 0.11 Sv. The dominant hydrographic variability at Bering Strait is seasonal, but this becomes less evident to the north. At Barrow Canyon, the dominant hydrographic signal is associated with year-to-year variations in sea-ice melt. Farther south there is pronounced mesoscale variability: an empirical orthogonal function analysis at Bering Strait and Point Hope reveals a distinct ACC mode and CC Branch mode in hydrography and baroclinic transport, where the former is wind-driven. Finally, the northward evolution in properties of the two currents is investigated. The poleward increase in salinity of the ACC can be explained by lateral mixing alone, but solar heating together with wind mixing play a large role in the temperature evolution. This same atmospheric forcing also impacts the northward evolution of the CC Branch.

Danielson Seth

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