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  • 1
    Publication Date: 2022-10-10
    Description: 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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Publication Date: 2022-05-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in MacKinnon, J. A., Simmons, H. L., Hargrove, J., Thomson, J., Peacock, T., Alford, M. H., Barton, B., Boury, S., Brenner, S. D., Couto, N., Danielson, S. L., Fine, E. C., Graber, H. C., Guthrie, J., Hopkins, J. E., Jayne, S. R., Jeon, C., Klenz, T., Lee, C. M., Lenn, Y-D., Lucas, A. J., Lund, B., Mahaffey, C., Norman, L., Rainville, L., Smith, M. M., Thomas, L. N., Torres-Valdés, S., & Wood, K. R. A warm jet in a cold ocean. Nature Communications, 12(1), (2021): 2418, https://doi.org/10.1038/s41467-021-22505-5.
    Description: 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.
    Description: Support for this work was provided by the US Office of Naval Research Stratified Ocean Dynamics of the Arctic program (grant numbers N000141512903, N000141612378, N000141612377, N000141612379, N0001416123450, N000141612360, N000141612349, N000141812007, N000141812475, and N000141912514). Additional support for biogeochemistry sampling was provided by UK (NERC) and Germany (BMBF) through the Changing Arctic Ocean Program’s ARISE (NE/P006035/1, NE/P006000/2), PEANUTS (NE/R01275X/1, NE/R012547/2, and BMBF 03F0804) projects and the UK-France PhD program DGA/Dstl. Float deployments and hydrographic data compilations were supported in part by North Pacific Research Board grants A91-99a and A91-00a. The deployment of autonomous ocean profilers was supported by ONR, NOAA Research, and the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement NA15OAR4320063.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2022-06-13
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fine, E., MacKinnon, J., Alford, M., Middleton, L., Taylor, J., Mickett, J., Cole, S., Couto, N., Boyer, A., & Peacock, T. Double diffusion, shear instabilities, and heat impacts of a pacific summer water intrusion in the Beaufort Sea. Journal of Physical Oceanography, 52(2), (2022): 189–203, https://doi.org/10.1175/jpo-d-21-0074.1.
    Description: Pacific Summer Water eddies and intrusions transport heat and salt from boundary regions into the western Arctic basin. Here we examine concurrent effects of lateral stirring and vertical mixing using microstructure data collected within a Pacific Summer Water intrusion with a length scale of ∼20 km. This intrusion was characterized by complex thermohaline structure in which warm Pacific Summer Water interleaved in alternating layers of O(1) m thickness with cooler water, due to lateral stirring and intrusive processes. Along interfaces between warm/salty and cold/freshwater masses, the density ratio was favorable to double-diffusive processes. The rate of dissipation of turbulent kinetic energy (ε) was elevated along the interleaving surfaces, with values up to 3 × 10−8 W kg−1 compared to background ε of less than 10−9 W kg−1. Based on the distribution of ε as a function of density ratio Rρ, we conclude that double-diffusive convection is largely responsible for the elevated ε observed over the survey. The lateral processes that created the layered thermohaline structure resulted in vertical thermohaline gradients susceptible to double-diffusive convection, resulting in upward vertical heat fluxes. Bulk vertical heat fluxes above the intrusion are estimated in the range of 0.2–1 W m−2, with the localized flux above the uppermost warm layer elevated to 2–10 W m−2. Lateral fluxes are much larger, estimated between 1000 and 5000 W m−2, and set an overall decay rate for the intrusion of 1–5 years.
    Description: This work was supported by ONR Grant N00014-16-1-2378 and NSF Grants PLR 14-56705 and PLR-1303791, NSF Graduate Research Fellowship Grant DGE-1650112, as well as by the Postdoctoral Scholar Program at Woods Hole Oceanographic Institution, with funding provided by the Weston Howland Jr. Postdoctoral Scholarship.
    Keywords: Arctic ; Diapycnal mixing ; Diffusion ; Fluxes ; Instability ; Mixing ; Turbulence
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2022-05-26
    Description: © The Author(s), 2021 This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bowman, J. S., Van Mooy, B. A. S., Lowenstein, D. P., Fredricks, H. F., Hansel, C. M., Gast, R., Collins, J. R., Couto, N., & Ducklow, H. W. Whole community metatranscriptomes and lipidomes reveal diverse responses among antarctic phytoplankton to changing ice conditions. Frontiers in Marine Science, 8,(2021): 593566, https://doi.org/10.3389/fmars.2021.593566.
    Description: The transition from winter to spring represents a major shift in the basal energy source for the Antarctic marine ecosystem from lipids and other sources of stored energy to sunlight. Because sea ice imposes a strong control on the transmission of sunlight into the water column during the polar spring, we hypothesized that the timing of the sea ice retreat influences the timing of the transition from stored energy to photosynthesis. To test the influence of sea ice on water column microbial energy utilization we took advantage of unique sea ice conditions in Arthur Harbor, an embayment near Palmer Station on the western Antarctic Peninsula, during the 2015 spring–summer seasonal transition. Over a 5-week period we sampled water from below land-fast sea ice, in the marginal ice zone at nearby Palmer Station B, and conducted an ice removal experiment with incubations of water collected below the land-fast ice. Whole-community metatranscriptomes were paired with lipidomics to better understand how lipid production and utilization was influenced by light conditions. We identified several different phytoplankton taxa that responded similarly to light by the number of genes up-regulated, and in the transcriptional complexity of this response. We applied a principal components analysis to these data to reduce their dimensionality, revealing that each of these taxa exhibited a strikingly different pattern of gene up-regulation. By correlating the changes in lipid concentration to the first principal component of log fold-change for each taxa we could make predictions about which taxa were associated with different changes in the community lipidome. We found that genes coding for the catabolism of triacylglycerol storage lipids were expressed early on in phytoplankton associated with a Fragilariopsis kerguelensis reference transcriptome. Phytoplankton associated with a Corethron pennatum reference transcriptome occupied an adjacent niche, responding favorably to higher light conditions than F. kerguelensis. Other diatom and dinoflagellate taxa had distinct transcriptional profiles and correlations to lipids, suggesting diverse ecological strategies during the polar winter–spring transition.
    Description: JB was supported by NSF-OPP 1641019, NSF-OPP 1846837, and the Simons Foundation Early Career Marine Microbial Investigator program. BV, DL and JC were supported by NSF (OPP-1543328 and OCE-1756254). CH was supported by NSF OCE-1355720. The Palmer LTER project is support by NSF-OPP 1440435. A small-scale Community Sequencing Project (CSP) award from the DOE Joint Genome Institute supported part of the sequencing effort.
    Keywords: Antarctica ; phytoplankton ; lipids ; metatranscriptomics ; Palmer LTER project
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Publication Date: 2024-02-07
    Description: We contend that ocean turbulent fluxes should be included in the list of Essential Ocean Variables (EOVs) created by the Global Ocean Observing System. This list aims to identify variables that are essential to observe to inform policy and maintain a healthy and resilient ocean. Diapycnal turbulent fluxes quantify the rates of exchange of tracers (such as temperature, salinity, density or nutrients, all of which are already EOVs) across a density layer. Measuring them is necessary to close the tracer concentration budgets of these quantities. Measuring turbulent fluxes of buoyancy (Jb), heat (Jq), salinity (JS) or any other tracer requires either synchronous microscale (a few centimeters) measurements of both the vector velocity and the scalar (e.g., temperature) to produce time series of the highly correlated perturbations of the two variables, or microscale measurements of turbulent dissipation rates of kinetic energy (ϵ) and of thermal/salinity/tracer variance (χ), from which fluxes can be derived. Unlike isopycnal turbulent fluxes, which are dominated by the mesoscale (tens of kilometers), microscale diapycnal fluxes cannot be derived as the product of existing EOVs, but rather require observations at the appropriate scales. The instrumentation, standardization of measurement practices, and data coordination of turbulence observations have advanced greatly in the past decade and are becoming increasingly robust. With more routine measurements, we can begin to unravel the relationships between physical mixing processes and ecosystem health. In addition to laying out the scientific relevance of the turbulent diapycnal fluxes, this review also compiles the current developments steering the community toward such routine measurements, strengthening the case for registering the turbulent diapycnal fluxes as an pilot Essential Ocean Variable.
    Type: Article , PeerReviewed
    Format: text
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