Janout
Markus A.
Janout
Markus A.
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ArticleEddies and the distribution of eddy kinetic energy in the Arctic Ocean(Oceanography Society, 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, QiangMesoscale 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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ArticleVariability and redistribution of heat in the Atlantic Water boundary current north of Svalbard(John Wiley & Sons, 2018-09-12) Renner, Angelika H. H. ; Sundfjord, Arild ; Janout, Markus A. ; Ingvaldsen, Randi B. ; Beszczynska-Möller, Agnieszka ; Pickart, Robert S. ; Pérez-Hernández, M. DoloresWe quantify Atlantic Water heat loss north of Svalbard using year‐long hydrographic and current records from three moorings deployed across the Svalbard Branch of the Atlantic Water boundary current in 2012–2013. The boundary current loses annually on average 16 W m−2 during the eastward propagation along the upper continental slope. The largest vertical fluxes of >100 W m−2 occur episodically in autumn and early winter. Episodes of sea ice imported from the north in November 2012 and February 2013 coincided with large ocean‐to‐ice heat fluxes, which effectively melted the ice and sustained open water conditions in the middle of the Arctic winter. Between March and early July 2013, a persistent ice cover‐modulated air‐sea fluxes. Melting sea ice at the start of the winter initiates a cold, up to 100‐m‐deep halocline separating the ice cover from the warm Atlantic Water. Semidiurnal tides dominate the energy over the upper part of the slope. The vertical tidal structure depends on stratification and varies seasonally, with the potential to contribute to vertical fluxes with shear‐driven mixing. Further processes impacting the heat budget include lateral heat loss due to mesoscale eddies, and modest and negligible contributions of Ekman pumping and shelf break upwelling, respectively. The continental slope north of Svalbard is a key example regarding the role of ocean heat for the sea ice cover. Our study underlines the complexity of the ocean's heat budget that is sensitive to the balance between oceanic heat advection, vertical fluxes, air‐sea interaction, and the sea ice cover.
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ArticleOverview of the MOSAiC expedition: physical oceanography(University of California Press, 2022-02-07) Rabe, Benjamin ; Heuzé, Céline ; Regnery, Julia ; Aksenov, Yevgeny ; Allerholt, Jacob ; Athanase, Marylou ; Bai, Youcheng ; Basque, Chris R. ; Bauch, Dorothea ; Baumann, Till M. ; Chen, Dake ; Cole, Sylvia T. ; Craw, Lisa ; Davies, Andrew ; Damm, Ellen ; Dethloff, Klaus ; Divine, Dmitry V. ; Doglioni, Francesca ; Ebert, Falk ; Fang, Ying-Chih ; Fer, Ilker ; Fong, Allison A. ; Gradinger, Rolf ; Granskog, Mats A. ; Graupner, Rainer ; Haas, Christian ; He, Hailun ; Hoppmann, Mario ; Janout, Markus A. ; Kadko, David ; Kanzow, Torsten C. ; Karam, Salar ; Kawaguchi, Yusuke ; Koenig, Zoe ; Kong, Bin ; Krishfield, Richard A. ; Krumpen, Thomas ; Kuhlmey, David ; Kuznetsov, Ivan ; Lan, Musheng ; Laukert, Georgi ; Lei, Ruibo ; Li, Tao ; Torres-Valdes, Sinhue ; Lin, Lina ; Lin, Long ; Liu, Hailong ; Liu, Na ; Loose, Brice ; Ma, Xiaobing ; McKay, Rosalie ; Mallet, Maria ; Mallett, Robbie ; Maslowski, Wieslaw ; Mertens, Christian ; Mohrholz, Volker ; Muilwijk, Morven ; Nicolaus, Marcel ; O’Brien, Jeffrey K. ; Perovich, Donald K. ; Ren, Jian ; Rex, Markus ; Ribeiro, Natalia ; Rinke, Annette ; Schaffer, Janin ; Schuffenhauer, Ingo ; Schulz, Kirstin ; Shupe, Matthew ; Shaw, William J. ; Sokolov, Vladimir T. ; Sommerfeld, Anja ; Spreen, Gunnar ; Stanton, Timothy P. ; Stephens, Mark ; Su, Jie ; Sukhikh, Natalia ; Sundfjord, Arild ; Thomisch, Karolin ; Tippenhauer, Sandra ; Toole, John M. ; Vredenborg, Myriel ; Walter, Maren ; Wang, Hangzhou ; Wang, Lei ; Wang, Yuntao ; Wendisch, Manfred ; Zhao, Jinping ; Zhou, Meng ; Zhu, JialiangArctic Ocean properties and processes are highly relevant to the regional and global coupled climate system, yet still scarcely observed, especially in winter. Team OCEAN conducted a full year of physical oceanography observations as part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), a drift with the Arctic sea ice from October 2019 to September 2020. An international team designed and implemented the program to characterize the Arctic Ocean system in unprecedented detail, from the seafloor to the air-sea ice-ocean interface, from sub-mesoscales to pan-Arctic. The oceanographic measurements were coordinated with the other teams to explore the ocean physics and linkages to the climate and ecosystem. This paper introduces the major components of the physical oceanography program and complements the other team overviews of the MOSAiC observational program. Team OCEAN’s sampling strategy was designed around hydrographic ship-, ice- and autonomous platform-based measurements to improve the understanding of regional circulation and mixing processes. Measurements were carried out both routinely, with a regular schedule, and in response to storms or opening leads. Here we present along-drift time series of hydrographic properties, allowing insights into the seasonal and regional evolution of the water column from winter in the Laptev Sea to early summer in Fram Strait: freshening of the surface, deepening of the mixed layer, increase in temperature and salinity of the Atlantic Water. We also highlight the presence of Canada Basin deep water intrusions and a surface meltwater layer in leads. MOSAiC most likely was the most comprehensive program ever conducted over the ice-covered Arctic Ocean. While data analysis and interpretation are ongoing, the acquired datasets will support a wide range of physical oceanography and multi-disciplinary research. They will provide a significant foundation for assessing and advancing modeling capabilities in the Arctic Ocean.
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ArticleNutrient and silicon isotope dynamics in the Laptev Sea and implications for nutrient availability in the Transpolar Drift(American Geophysical Union, 2022-09-07) Laukert, Georgi ; Grasse, Patricia ; Novikhin, A. ; Povazhnyi, V. ; Doering, Kristin ; Hölemann, Jens ; Janout, Markus ; Bauch, Dorothea ; Kassens, Heidemarie ; Frank, MartinRealistic prediction of the near‐future response of Arctic Ocean primary productivity to ongoing warming and sea ice loss requires a mechanistic understanding of the processes controlling nutrient bioavailability. To evaluate continental nutrient inputs, biological utilization, and the influence of mixing and winter processes in the Laptev Sea, the major source region of the Transpolar Drift (TPD), we compare observed with preformed concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP), silicic acid (DSi), and silicon isotope compositions of DSi (δ30SiDSi) obtained for two summers (2013 and 2014) and one winter (2012). In summer, preformed nutrient concentrations persisted in the surface layer of the southeastern Laptev Sea, while diatom‐dominated utilization caused intense northward drawdown and a pronounced shift in δ30SiDSi from +0.91 to +3.82‰. The modeled Si isotope fractionation suggests that DSi in the northern Laptev Sea originated from the Lena River and was supplied during the spring freshet, while riverine DSi in the southeastern Laptev Sea was continuously supplied during the summer. Primary productivity fueled by river‐borne nutrients was enhanced by admixture of DIN‐ and DIP‐rich Atlantic‐sourced waters to the surface, either by convective mixing during the previous winter or by occasional storm‐induced stratification breakdowns in late summer. Substantial enrichments of DSi (+240%) and DIP (+90%) beneath the Lena River plume were caused by sea ice‐driven redistribution and remineralization. Predicted weaker stratification on the outer Laptev Shelf will enhance DSi utilization and removal through greater vertical DIN supply, which will limit DSi export and reduce diatom‐dominated primary productivity in the TPD.
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ArticleFRIS revisited in 2018: on the circulation and water masses at the Filchner and Ronne Ice Shelves in the Southern Weddell Sea(American Geophysical Union, 2021-05-18) Janout, Markus A. ; Hellmer, Hartmut H. ; Hattermann, Tore ; Huhn, Oliver ; Sultenfuß, Jurgen ; Østerhus, Svein ; Stulic, Lukrecia ; Ryan, Svenja ; Schröder, Michael ; Kanzow, TorstenThe Filchner-Ronne Ice Shelf (FRIS) is characterized by moderate basal melt rates due to the near-freezing waters that dominate the wide southern Weddell Sea continental shelf. We revisited the region in austral summer 2018 with detailed hydrographic and noble gas surveys along FRIS. The FRIS front was characterized by High Salinity Shelf Water (HSSW) in Ronne Depression, Ice Shelf Water (ISW) on its eastern flank, and an inflow of modified Warm Deep Water (mWDW) entering through Central Trough. Filchner Trough was dominated by Ronne HSSW-sourced ISW, likely forced by a recently intensified circulation beneath FRIS due to enhanced sea ice production in the Ronne polynya since 2015. Glacial meltwater fractions and tracer-based water mass dating indicate two separate ISW outflow cores, one hugging the Berkner slope after a two-year travel time, and the other located in the central Filchner Trough following a ∼six year-long transit through the FRIS cavity. Historical measurements indicate the presence of two distinct modes, in which water masses in Filchner Trough were dominated by either Ronne HSSW-derived ISW (Ronne-mode) or more locally derived Berkner-HSSW (Berkner-mode). While the dominance of these modes has alternated on interannual time scales, ocean densities in Filchner Trough have remained remarkably stable since the first surveys in 1980. Indeed, geostrophic velocities indicated outflowing ISW-cores along the trough's western flank and onto Berkner Bank, which suggests that Ronne-ISW preconditions Berkner-HSSW production. The negligible density difference between Berkner- and Ronne-mode waters indicates that each contributes cold dense shelf waters to protect FRIS against inflowing mWDW.
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ArticleExceptionally warm and prolonged flow of warm deep water toward the Filchner-Ronne Ice Shelf in 2017(Wiley, 2020-06-09) Ryan, Svenja ; Hellmer, Hartmut H. ; Janout, Markus A. ; Darelius, Elin ; Vignes, Lucie ; Schröder, MichaelThe Filchner‐Ronne Ice Shelf, fringing the southern Weddell Sea, is Antarctica's second largest ice shelf. At present, basal melt rates are low due to active dense water formation; however, model projections suggest a drastic increase in the future due to enhanced inflow of open‐ocean warm water. Mooring observations from 2014 to 2016 along the eastern flank of the Filchner Trough (76°S) revealed a distinct seasonal cycle with inflow if Warm Deep Water during summer and autumn. Here we present extended time series showing an exceptionally warm and long inflow in 2017, with maximum temperatures exceeding 0.5°C. Warm temperatures persisted throughout winter, associated with a fresh anomaly, which lead to a change in stratification over the shelf, favoring an earlier inflow in the following summer. We suggest that the fresh anomaly developed upstream after anomalous summer sea ice melting and contributed to a shoaling of the shelf break thermocline.
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DatasetCruise 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, EvelynCruise 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
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DatasetCruise 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, EvelynCruise 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
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ArticleReviews and syntheses: a framework to observe, understand and project ecosystem response to environmental change in the East Antarctic Southern Ocean(European Geosciences Union, 2022-11-23) Gutt, Julian ; Arndt, Stefanie ; Barnes, David Keith Alan ; Bornemann, Horst ; Brey, Thomas ; Eisen, Olaf ; Institute, Hauke ; Griffiths, Huw ; Institute, Christian ; Hain, Stefan ; Hattermann, Tore ; Held, Christoph ; Hoppema, Mario ; Isla, Enrique ; Janout, Markus ; Le Bohec, Céline ; Link, Heike ; Mark, Felix Christopher ; Moreau, Sebastien ; Trimborn, Scarlett ; Van Opzeeland, Ilse ; Pörtner, Hans-Otto ; Schaafsma, Fokje ; Teschke, Katharina ; Tippenhauer, Sana ; Van De Putte, Anton ; Wege, Mia ; Zitterbart, Daniel ; Piepenburg, DieterSystematic long-term studies on ecosystem dynamics are largely lacking from the East Antarctic Southern Ocean, although it is well recognized that they are indispensable to identify the ecological impacts and risks of environmental change. Here, we present a framework for establishing a long-term cross-disciplinary study on decadal timescales. We argue that the eastern Weddell Sea and the adjacent sea to the east, off Dronning Maud Land, is a particularly well suited area for such a study, since it is based on findings from previous expeditions to this region. Moreover, since climate and environmental change have so far been comparatively muted in this area, as in the eastern Antarctic in general, a systematic long-term study of its environmental and ecological state can provide a baseline of the current situation, which will be important for an assessment of future changes from their very onset, with consistent and comparable time series data underpinning and testing models and their projections. By establishing an Integrated East Antarctic Marine Research (IEAMaR) observatory, long-term changes in ocean dynamics, geochemistry, biodiversity, and ecosystem functions and services will be systematically explored and mapped through regular autonomous and ship-based synoptic surveys. An associated long-term ecological research (LTER) programme, including experimental and modelling work, will allow for studying climate-driven ecosystem changes and interactions with impacts arising from other anthropogenic activities. This integrative approach will provide a level of long-term data availability and ecosystem understanding that are imperative to determine, understand, and project the consequences of climate change and support a sound science-informed management of future conservation efforts in the Southern Ocean.