Articles | Volume 21, issue 6
https://doi.org/10.5194/os-21-3397-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-21-3397-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
10 Dec 2025
Research article |
| 10 Dec 2025
| 10 Dec 2025
Microstructure observations and mixing parameterizations along an Atlantic transect in very weak turbulence
NIOZ Royal Netherlands Institute for Sea Research, Den Burg, the Netherlands
Ocean and Earth Science, University of Southampton, Southampton, United Kingdom
Sjoerd Groeskamp
NIOZ Royal Netherlands Institute for Sea Research, Den Burg, the Netherlands
Bieito Fernandez Castro
Ocean and Earth Science, University of Southampton, Southampton, United Kingdom
Hans van Haren
NIOZ Royal Netherlands Institute for Sea Research, Den Burg, the Netherlands
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Hans van Haren
EGUsphere, https://doi.org/10.5194/egusphere-2026-188, https://doi.org/10.5194/egusphere-2026-188, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
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The Mediterranean Sea is known for its limited tidal motions. For example, surface barotropic tidal elevations have an amplitude of 0.1 m in the Northwestern Mediterranean. As is demonstrated in this paper, such small tides are noticeable in temperature records at the 2500-m deep seafloor, but only under near-homogeneous conditions. After correcting for pressure effects, the observed internal-wave temperature signals may thus be corrected for 1.5x10-5-°C amplitude semidiurnal barotropic tides.
Hans van Haren
EGUsphere, https://doi.org/10.5194/egusphere-2026-189, https://doi.org/10.5194/egusphere-2026-189, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
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In this paper, heights of moored oceanographic instrumentation are determined from high-resolution temperature data. Unfortunately pressure-corrected data could not be used from near-homogeneous conditions due to short-term electronic drift. Instead, a satisfactory height determination was found during relatively strong stratification and large turbulence activity. By using turbulence data across a strong temperature gradient, significant height variations were detectable to within ±0.2 m.
Hans van Haren
EGUsphere, https://doi.org/10.5194/egusphere-2026-190, https://doi.org/10.5194/egusphere-2026-190, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
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Turbulence is vital for life, also in 2500-m deep Mediterranean waters. Yearlong observations with about 3000 high-resolution temperature sensors show: About half the time, relatively warm stratified waters are moved from 100’s of meters higher levels to near the seafloor. These internal-wave and eddy-induced motions are three times more turbulent than those induced via general geothermal heating from below, and about ten times more turbulent than those from open-ocean processes.
Hans van Haren
EGUsphere, https://doi.org/10.5194/egusphere-2026-195, https://doi.org/10.5194/egusphere-2026-195, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
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Occasionally, high-resolution temperature sensors moored close to the 2550-m deep Mediterranean seafloor register minute-long flashes of 0.0005–0.001 °C warmer than the environment. A movie shows traveling heat flashes, most likely with internal-wave instabilities in overlying stratified waters. The instabilities seem to release the flashes from a geothermally heated seafloor of which turbulence convection is suppressed by warmer waters from above.
Hans van Haren
EGUsphere, https://doi.org/10.5194/egusphere-2026-193, https://doi.org/10.5194/egusphere-2026-193, 2026
This preprint is open for discussion and under review for Ocean Science (OS).
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3D high-resolution observations are used to investigate whether the interaction between energy-abundant (sub-)mesoscale eddies and internal waves can lead to turbulence generation in the deep Mediterranean. This may prove important for replenishment of nutrients for deep-sea life and circulation. Spectral power-laws demonstrate a dominance of convection-turbulence, which leads to a modification of the model for energy cascade in the deep sea.
Hans van Haren and Henk de Haas
Ocean Sci., 21, 1125–1140, https://doi.org/10.5194/os-21-1125-2025, https://doi.org/10.5194/os-21-1125-2025, 2025
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Turbulent water motions are important for the exchange of momentum, heat, nutrients, and suspended matter in the deep sea. The shape of the marine topography influences most water turbulence via breaking internal waves at critically sloping seafloors. In this paper, the concept of critical slopes is revisited from a global internal wave turbulence viewpoint using seafloor topography and moored temperature sensor data. The potential robustness of the seafloor–internal wave interaction is discussed.
Hans van Haren
Ocean Sci., 21, 555–565, https://doi.org/10.5194/os-21-555-2025, https://doi.org/10.5194/os-21-555-2025, 2025
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Ocean circulations include small-scale processes like transport through sub-mesoscale eddies and turbulence by internal wave breaking. Knowledge is lacking on the interaction between the different processes. In deep, weakly stratified waters, continuous spectral slopes are observed that extend from sub-mesoscales across the internal wave band to the turbulence range. Such correspondence is suggested as being a potential feedback mechanism stabilizing large-scale ocean circulations.
Sjoerd Groeskamp
EGUsphere, https://doi.org/10.5194/egusphere-2025-396, https://doi.org/10.5194/egusphere-2025-396, 2025
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It is possible to close the sea level rise budget, but we can’t estimate the underlying processes, such as ocean mixing or how sunlight penetrates into the deep ocean. This study estimates the size of these processes and how well we know them. It turns out we don’t know them very well, or how they will change in the future. This should worry us and we need to do more ocean observations to improve our understanding how these processes will change and impact future sea level rise.
Zhibo Shao, Yangchun Xu, Hua Wang, Weicheng Luo, Lice Wang, Yuhong Huang, Nona Sheila R. Agawin, Ayaz Ahmed, Mar Benavides, Mikkel Bentzon-Tilia, Ilana Berman-Frank, Hugo Berthelot, Isabelle C. Biegala, Mariana B. Bif, Antonio Bode, Sophie Bonnet, Deborah A. Bronk, Mark V. Brown, Lisa Campbell, Douglas G. Capone, Edward J. Carpenter, Nicolas Cassar, Bonnie X. Chang, Dreux Chappell, Yuh-ling Lee Chen, Matthew J. Church, Francisco M. Cornejo-Castillo, Amália Maria Sacilotto Detoni, Scott C. Doney, Cecile Dupouy, Marta Estrada, Camila Fernandez, Bieito Fernández-Castro, Debany Fonseca-Batista, Rachel A. Foster, Ken Furuya, Nicole Garcia, Kanji Goto, Jesús Gago, Mary R. Gradoville, M. Robert Hamersley, Britt A. Henke, Cora Hörstmann, Amal Jayakumar, Zhibing Jiang, Shuh-Ji Kao, David M. Karl, Leila R. Kittu, Angela N. Knapp, Sanjeev Kumar, Julie LaRoche, Hongbin Liu, Jiaxing Liu, Caroline Lory, Carolin R. Löscher, Emilio Marañón, Lauren F. Messer, Matthew M. Mills, Wiebke Mohr, Pia H. Moisander, Claire Mahaffey, Robert Moore, Beatriz Mouriño-Carballido, Margaret R. Mulholland, Shin-ichiro Nakaoka, Joseph A. Needoba, Eric J. Raes, Eyal Rahav, Teodoro Ramírez-Cárdenas, Christian Furbo Reeder, Lasse Riemann, Virginie Riou, Julie C. Robidart, Vedula V. S. S. Sarma, Takuya Sato, Himanshu Saxena, Corday Selden, Justin R. Seymour, Dalin Shi, Takuhei Shiozaki, Arvind Singh, Rachel E. Sipler, Jun Sun, Koji Suzuki, Kazutaka Takahashi, Yehui Tan, Weiyi Tang, Jean-Éric Tremblay, Kendra Turk-Kubo, Zuozhu Wen, Angelicque E. White, Samuel T. Wilson, Takashi Yoshida, Jonathan P. Zehr, Run Zhang, Yao Zhang, and Ya-Wei Luo
Earth Syst. Sci. Data, 15, 3673–3709, https://doi.org/10.5194/essd-15-3673-2023, https://doi.org/10.5194/essd-15-3673-2023, 2023
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N2 fixation by marine diazotrophs is an important bioavailable N source to the global ocean. This updated global oceanic diazotroph database increases the number of in situ measurements of N2 fixation rates, diazotrophic cell abundances, and nifH gene copy abundances by 184 %, 86 %, and 809 %, respectively. Using the updated database, the global marine N2 fixation rate is estimated at 223 ± 30 Tg N yr−1, which triplicates that using the original database.
Johan van der Molen, Sjoerd Groeskamp, and Leo R. M. Maas
Ocean Sci., 18, 1805–1816, https://doi.org/10.5194/os-18-1805-2022, https://doi.org/10.5194/os-18-1805-2022, 2022
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We studied the long-term mean flow through the Marsdiep tidal inlet in the Dutch Wadden Sea. We found that this flow, which is important for sediment, salt and nutrient balances, is reversing from net outflow to inflow. We hypothesise changes in tides in the North Sea caused this, due to increased stratification in response to global warming. Hence, we expect permanent inflow conditions within 1 decade, with potential effects on the sediment balance and the ecosystem of this World Heritage Site.
Pascal Perolo, Bieito Fernández Castro, Nicolas Escoffier, Thibault Lambert, Damien Bouffard, and Marie-Elodie Perga
Earth Syst. Dynam., 12, 1169–1189, https://doi.org/10.5194/esd-12-1169-2021, https://doi.org/10.5194/esd-12-1169-2021, 2021
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Wind blowing over the ocean creates waves that, by increasing the level of turbulence, promote gas exchange at the air–water interface. In this study, for the first time, we measured enhanced gas exchanges by wind-induced waves at the surface of a large lake. We adapted an ocean-based model to account for the effect of surface waves on gas exchange in lakes. We finally show that intense wind events with surface waves contribute disproportionately to the annual CO2 gas flux in a large lake.
Daniel Lee, Amandine Schaeffer, and Sjoerd Groeskamp
Ocean Sci., 17, 1341–1351, https://doi.org/10.5194/os-17-1341-2021, https://doi.org/10.5194/os-17-1341-2021, 2021
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The bluebottle (Physalia physalis), or Portuguese man o' war, is well known for the painful stings caused by its tentacles. Its drifting dynamics have not been widely explored, with previous studies using simple assumptions to calculate its drift. Considering similarities with a sailboat, we present a new theoretical model for the drifting speed and course of the bluebottle in different wind and ocean conditions, providing new insights into the parameterization of its complex drifting dynamics.
Nadia Burgoa, Francisco Machín, Ángel Rodríguez-Santana, Ángeles Marrero-Díaz, Xosé Antón Álvarez-Salgado, Bieito Fernández-Castro, María Dolores Gelado-Caballero, and Javier Arístegui
Ocean Sci., 17, 769–788, https://doi.org/10.5194/os-17-769-2021, https://doi.org/10.5194/os-17-769-2021, 2021
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The circulation patterns in the confluence of the North Atlantic subtropical and tropical gyres delimited by the Cape Verde Front were examined during a field cruise in summer 2017. The collected hydrographic data, O2 and inorganic nutrients along the perimeter of a closed box embracing the Cape Verde Frontal Zone allowed for the independent estimation of the transport of these properties.
Hans van Haren, Corina P. D. Brussaard, Loes J. A. Gerringa, Mathijs H. van Manen, Rob Middag, and Ruud Groenewegen
Ocean Sci., 17, 301–318, https://doi.org/10.5194/os-17-301-2021, https://doi.org/10.5194/os-17-301-2021, 2021
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Changes in ocean temperature may affect vertical density stratification, which may hamper turbulent exchange and thus nutrient availability for phytoplankton growth. To quantify varying physical conditions, we sampled the upper 500 m along 17 ± 5° W between [30, 63]° N in summer. South to north, temperature decreased with stratification while turbulence and nutrient fluxes remained constant, likely due to internal waves breaking and little affected by the physical process of global warming.
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Short summary
This study compares both microstructure shear and thermistor data, and finds very weak dissipations rates down to O(10−12) W kg−1. The direct microstructure observations are compared to a finescale parameterization and Thorpe sorting method, for which we find good comparison. Insights into the relative roles between isoneutral and dianeutral mixing are obtained by using the triple decomposition framework.
This study compares both microstructure shear and thermistor data, and finds very weak...
