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  • Articles  (4)
  • Winter water  (2)
  • Arctic Ocean  (1)
  • Boundary currents  (1)
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  • Articles  (4)
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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 118 (2015): 53-72, doi:10.1016/j.dsr2.2015.06.006.
    Description: The flow of nutrient-rich winter water (WW) through the Chukchi Sea plays an important and previously uncharacterized role in sustaining summer phytoplankton blooms. Using hydrographic and biogeochemical data collected as part of the ICESCAPE program (June-July 2010-11), we examined phytoplankton bloom dynamics in relation to the distribution and circulation of WW (defined as water with potential temperature ≤ -1.6°C) across the Chukchi shelf. Characterized by high concentrations of nitrate (mean: 12.3 ± 5.13 μmol L-1) that typically limits primary production in this region, WW was correlated with extremely high phytoplankton biomass, with mean chlorophyll a concentrations that were three-fold higher in WW (8.64 ± 9.75 μg L-1) than in adjacent warmer water (2.79 ± 5.58 μg L-1). Maximum chlorophyll a concentrations (~30 μg L-1) were typically positioned at the interface between nutrient-rich WW and shallower, warmer water with more light availability. Comparing satellite-based calculations of open water duration to phytoplankton biomass, nutrient concentrations, and oxygen saturation revealed widespread evidence of under-ice blooms prior to our sampling, with biogeochemical properties indicating that blooms had already terminated in many places where WW was no longer present. Our results suggest that summer phytoplankton blooms are sustained for a longer duration along the pathways of nutrient-rich WW and that biological hotspots in this region (e.g. the mouth of Barrow Canyon) are largely driven by the flow and confluence of these extremely productive pathways of WW that flow across the Chukchi shelf.
    Description: This material is based upon work supported by the National Aeronautic and Space Administration (NASA) under Grant No. NNX10AF42G and the National Science Foundation Graduate Research Fellowship under Grant No. DGE-0645962 to K.E. Lowry.
    Keywords: Phytoplankton ; Winter water ; Under-ice blooms ; Biological hotspots ; Chukchi Sea
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 2
    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 102 (2015): 43-54, doi:10.1016/j.dsr.2015.04.004.
    Description: Over the past few decades, sea ice retreat during summer has been enhanced in the Pacific sector of the Arctic basin, likely due in part to increasing summertime heat flux of Pacific-origin water from the Bering Strait. Barrow Canyon, in the northeast Chukchi Sea, is a major conduit through which the Pacific-origin water enters the Arctic basin. This paper presents results from 6 repeat high-resolution shipboard hydrographic/velocity sections occupied across Barrow Canyon in summer 2010. The different Pacific water masses feeding the canyon – Alaskan coastal water (ACW), summer Bering Sea water (BSW), and Pacific winter water (PWW) – all displayed significant intra-seasonal variability. Net volume transports through the canyon were between 0.96 and 1.70 Sv poleward, consisting of 0.41–0.98 Sv of warm Pacific water (ACW and BSW) and 0.28–0.65 Sv of PWW. The poleward heat flux also varied strongly, ranging from 8.56 TW to 24.56 TW, mainly due to the change in temperature of the warm Pacific water. Using supplemental mooring data from the core of the warm water, along with wind data from the Pt. Barrow weather station, we derive and assess a proxy for estimating heat flux in the canyon for the summer time period, which is when most of the heat passes northward towards the basin. The average heat flux for 2010 was estimated to be 3.34 TW, which is as large as the previous record maximum in 2007. This amount of heat could melt 315,000 km2 of 1-meter thick ice, which likely contributed to significant summer sea ice retreat in the Pacific sector of the Arctic Ocean.
    Description: MI, TK, YF, KO and DS were supported by Green Network of Excellence Program (GRENE Program), Arctic Climate Change Research Project ‘Rapid Change of the Arctic Climate System and its Global Influences’ by Ministry of Education, Culture, Sports, Science and Technology Japan. RP was supported by grant ARC-1203906 from the US National Science Foundation. CA was supported by grant ARC-1023331 from the US National Science Foundation and by the Cooperative Institute for the North Atlantic Region (NOAA Cooperative AgreementNA09OAR4320129) with funds provided by the US National Oceanographic and Atmospheric Administration through an Interagency Agreement between the US Bureau of Ocean and Energy Management and the National Marine Mammal Laboratory. SV was supported by the Department of Fisheries and Oceans Canada. MI and TK were supported by the Japan Agency for Marine-Earth Science and Technology. MI, TK, YF and KO were supported by Grant no. 2014-23 from Joint Research Program of the Institute of Low Temperature Science, Hokkaido University. YF and KO were supported by grants-in-aid 20221001 for scientific research from the Ministry of Education, Culture, Sports, Science and Technology of Japan. JTM was supported by grant PLR-1041102 from the US National Science Foundation.
    Keywords: Polar oceanography ; Arctic Ocean ; Chukchi Sea ; Heat fluxes ; Volume transports ; Water properties
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 105 (2014): 17-29, doi:10.1016/j.dsr2.2014.03.017.
    Description: In the summer of 2011, an oceanographic survey carried out by the Impacts of Climate on EcoSystems and Chemistry of the Arctic Pacific Environment (ICESCAPE) program revealed the presence of a massive phytoplankton bloom under the ice near the shelfbreak in the central Chukchi Sea. For most of the month preceding the measurements there were relatively strong easterly winds, providing upwelling favorable conditions along the shelfbreak. Analysis of similar hydrographic data from summer 2002, in which there were no persistent easterly winds, found no evidence of upwelling near the shelfbreak. A two-dimensional ocean circulation model is used to show that sufficiently strong winds can result not only in upwelling of high nutrient water from offshore onto the shelf, but it can also transport the water out of the bottom boundary layer into the surface Ekman layer at the shelf edge. The extent of upwelling is determined by the degree of overlap between the surface Ekman layer and the bottom boundary layer on the outer shelf. Once in the Ekman layer, this high nutrient water is further transported to the surface through mechanical mixing driven by the surface stress. Two model tracers, a nutrient tracer and a chlorophyll tracer, reveal distributions very similar to that observed in the data. These results suggest that the biomass maximum near the shelfbreak during the massive bloom in summer 2011 resulted from an enhanced supply of nutrients upwelled from the halocline seaward of the shelf. The decade long trend in summertime surface winds suggest that easterly winds in this region are increasing in strength and that such bloom events will become more common.
    Description: This study was supported by the National Science Foundation under Grant OCE-0959381 (MAS), and by the Ocean Biology and Biogeochemistry Program and the Cryosphere Science Program of the National Aeronautic and Space Administration under Award NNX10AF42G (RSP;KRA). GWKM was supported by the Natural Sciences and Engineering Research Council of Canada. ETB was supported by the U. S. Navy.
    Keywords: Upwelling ; Boundary currents ; Shelf-basin interaction ; Phytoplankton blooms
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 4
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research-Oceans 124 (2019): 7153– 7177, doi: 10.1029/2019JC015261.
    Description: Data from a late spring survey of the northeast Chukchi Sea are used to investigate various aspects of newly ventilated winter water (NVWW). More than 96% of the water sampled on the shelf was NVWW, the saltiest (densest) of which tended to be in the main flow pathways on the shelf. Nearly all of the hydrographic profiles on the shelf displayed a two‐layer structure, with a surface mixed layer and bottom boundary layer separated by a weak density interface (on the order of 0.02 kg/m3). Using a polynya model to drive a one‐dimensional mixing model, it was demonstrated that, on average, the profiles would become completely homogenized within 14–25 hr when subjected to the March and April heat fluxes. A subset of the profiles would become homogenized when subjected to the May heat fluxes. Since the study domain contained numerous leads within the pack ice—many of them refreezing—and since some of the measured profiles were vertically uniform in density, this suggests that NVWW is formed throughout the Chukchi shelf via convection within small openings in the ice. This is consistent with the result that the salinity signals of the NVWW along the central shelf pathway cannot be explained solely by advection from Bering Strait or via modification within large polynyas. The local convection would be expected to stir nutrients into the water column from the sediments, which explains the high nitrate concentrations observed throughout the shelf. This provides a favorable initial condition for phytoplankton growth on the Chukchi shelf.
    Description: The authors are indebted to Commanding Officer John Reeves, Executive Officer Gregory Stanclik, Operations Officer Jacob Cass, and the entire crew of the USCGC Healy for their hard work and dedication in making the SUBICE cruise a success. We also acknowledge Scott Hiller for his assistance with Healy's meteorological data. We thank an anonymous reviewer for helpful input that improved the paper. Funding for A. P., R. P., C. N., and F. B. was provided by the National Science Foundation (NSF) under grant PLR‐1303617. K. M. was funded by the Natural Sciences and Engineering Research Council of Canada. K. V. acknowledges the Bergen Research Foundation under Grant BFS2016REK01. K. A. was supported by the NSF grant PLR‐1304563. The CTD and shipboard ADCP data are available from https://www.rvdata.us/search/cruise/HLY1401, and the nutrient data can be accessed from https://arcticdata.io/catalog/view/doi:10.18739/A2RG3Z and http://ocean.stanford.edu/subice/. The shipboard meteorological data reside at http://ocean.stanford.edu/subice/.
    Description: 2020-04-14
    Keywords: Brine rejection ; Chukchi Sea ; Convection ; Winter water
    Repository Name: Woods Hole Open Access Server
    Type: Article
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