Lenn Yueng-Djern

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Last Name
Lenn
First Name
Yueng-Djern
ORCID
0000-0001-6031-523X

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Eddies and the distribution of eddy kinetic energy in the Arctic Ocean

2022-04-27 , von Appen, Wilken-Jon , Baumann, Till M. , Janout, Markus A. , Koldunov, Nikolay , Lenn, Yueng-Djern , Pickart, Robert S. , Scott, Robert B. , Wang, Qiang

Mesoscale eddies are important to many aspects of the dynamics of the Arctic Ocean. Among others, they maintain the halocline and interact with the Atlantic Water circumpolar boundary current through lateral eddy fluxes and shelf-basin exchanges. Mesoscale eddies are also important for transporting biological material and for modifying sea ice distribution. Here, we review what is known about eddies and their impacts in the Arctic Ocean in the context of rapid climate change. Eddy kinetic energy (EKE) is a proxy for mesoscale variability in the ocean due to eddies. We present the first quantification of EKE from moored observations across the entire Arctic Ocean and compare those results to output from an eddy resolving numerical model. We show that EKE is largest in the northern Nordic Seas/Fram Strait and it is also elevated along the shelf break of the Arctic Circumpolar Boundary Current, especially in the Beaufort Sea. In the central basins, EKE is 100–1,000 times lower. Generally, EKE is stronger when sea ice concentration is low versus times of dense ice cover. As sea ice declines, we anticipate that areas in the Arctic Ocean where conditions typical of the North Atlantic and North Pacific prevail will increase. We conclude that the future Arctic Ocean will feature more energetic mesoscale variability.

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On the future of Argo: A global, full-depth, multi-disciplinary array

2019-08-02 , Roemmich, Dean , Alford, Matthew H. , Claustre, Hervé , Johnson, Kenneth S. , King, Brian , Moum, James N. , Oke, Peter , Owens, W. Brechner , Pouliquen, Sylvie , Purkey, Sarah G. , Scanderbeg, Megan , Suga, Koushirou , Wijffels, Susan E. , Zilberman, Nathalie , Bakker, Dorothee , Baringer, Molly O. , Belbeoch, Mathieu , Bittig, Henry C. , Boss, Emmanuel S. , Calil, Paulo H. R. , Carse, Fiona , Carval, Thierry , Chai, Fei , Conchubhair, Diarmuid Ó. , d’Ortenzio, Fabrizio , Dall'Olmo, Giorgio , Desbruyeres, Damien , Fennel, Katja , Fer, Ilker , Ferrari, Raffaele , Forget, Gael , Freeland, Howard , Fujiki, Tetsuichi , Gehlen, Marion , Geenan, Blair , Hallberg, Robert , Hibiya, Toshiyuki , Hosoda, Shigeki , Jayne, Steven R. , Jochum, Markus , Johnson, Gregory C. , Kang, KiRyong , Kolodziejczyk, Nicolas , Körtzinger, Arne , Le Traon, Pierre-Yves , Lenn, Yueng-Djern , Maze, Guillaume , Mork, Kjell Arne , Morris, Tamaryn , Nagai, Takeyoshi , Nash, Jonathan D. , Naveira Garabato, Alberto C. , Olsen, Are , Pattabhi Rama Rao, Eluri , Prakash, Satya , Riser, Stephen C. , Schmechtig, Catherine , Schmid, Claudia , Shroyer, Emily L. , Sterl, Andreas , Sutton, Philip J. H. , Talley, Lynne D. , Tanhua, Toste , Thierry, Virginie , Thomalla, Sandy J. , Toole, John M. , Troisi, Ariel , Trull, Thomas W. , Turton, Jon , Velez-Belchi, Pedro , Walczowski, Waldemar , Wang, Haili , Wanninkhof, Rik , Waterhouse, Amy F. , Waterman, Stephanie N. , Watson, Andrew J. , Wilson, Cara , Wong, Annie P. S. , Xu, Jianping , Yasuda, Ichiro

The Argo Program has been implemented and sustained for almost two decades, as a global array of about 4000 profiling floats. Argo provides continuous observations of ocean temperature and salinity versus pressure, from the sea surface to 2000 dbar. The successful installation of the Argo array and its innovative data management system arose opportunistically from the combination of great scientific need and technological innovation. Through the data system, Argo provides fundamental physical observations with broad societally-valuable applications, built on the cost-efficient and robust technologies of autonomous profiling floats. Following recent advances in platform and sensor technologies, even greater opportunity exists now than 20 years ago to (i) improve Argo’s global coverage and value beyond the original design, (ii) extend Argo to span the full ocean depth, (iii) add biogeochemical sensors for improved understanding of oceanic cycles of carbon, nutrients, and ecosystems, and (iv) consider experimental sensors that might be included in the future, for example to document the spatial and temporal patterns of ocean mixing. For Core Argo and each of these enhancements, the past, present, and future progression along a path from experimental deployments to regional pilot arrays to global implementation is described. The objective is to create a fully global, top-to-bottom, dynamically complete, and multidisciplinary Argo Program that will integrate seamlessly with satellite and with other in situ elements of the Global Ocean Observing System (Legler et al., 2015). The integrated system will deliver operational reanalysis and forecasting capability, and assessment of the state and variability of the climate system with respect to physical, biogeochemical, and ecosystems parameters. It will enable basic research of unprecedented breadth and magnitude, and a wealth of ocean-education and outreach opportunities.

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A warm jet in a cold ocean

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.