Topographic Steering of the Upper Arctic Ocean Circulation by Deep Flows
Dynamically, the Arctic Ocean is characterised by the presence of closed f/H contours, where f is the Coriolis parameter and H the depth. On closed f/H contours, a net integrated surface wind stress can theoretically drive relatively strong near-bottom flows. Nevertheless, the Rossby number of the l...
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Stockholm University Press
2024-11-01
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| Series: | Tellus: Series A, Dynamic Meteorology and Oceanography |
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| Online Access: | https://account.a.tellusjournals.se/index.php/su-j-tadmo/article/view/4072 |
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| author | Johan Nilsson Jan-Adrian H. Kallmyr Pål Erik Isachsen |
| author_facet | Johan Nilsson Jan-Adrian H. Kallmyr Pål Erik Isachsen |
| author_sort | Johan Nilsson |
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| description | Dynamically, the Arctic Ocean is characterised by the presence of closed f/H contours, where f is the Coriolis parameter and H the depth. On closed f/H contours, a net integrated surface wind stress can theoretically drive relatively strong near-bottom flows. Nevertheless, the Rossby number of the large-scale time-mean flow in the Arctic Ocean is estimated to be small, implying that the near-bottom flow should essentially be aligned with the f/H contours. Observations indicate that the time-mean surface flow also tends to follow the f/H contours, which in the Arctic are essentially controlled by H. To examine mechanisms that can organise the Arctic Ocean surface flow along the topography, we use a two-layer large-scale geostrophic model on an f-plane (exploiting that f/H variations are dominated by depth variations). The effect of time-dependent baroclinic eddies is represented as an eddy diffusion of the upper-layer thickness. We study how wind forcing, stratification, eddy diffusivity and bottom friction affect the topographic steering of the time-mean surface flow, introducing relevant non-dimensional parameters. The analyses suggest that the Arctic Ocean is in a regime where strong along-isobath near-bottom flows can align the buoyancy field and, thereby, the surface currents with the topography. We then discuss the model results in relation to satellite-derived surface currents in the Arctic Ocean and briefly consider additional mechanisms that can align surface flows with the topography. |
| format | Article |
| id | doaj-art-12e74af3cfb542e99db100ddef282b5f |
| institution | Kabale University |
| issn | 1600-0870 |
| language | English |
| publishDate | 2024-11-01 |
| publisher | Stockholm University Press |
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| series | Tellus: Series A, Dynamic Meteorology and Oceanography |
| spelling | doaj-art-12e74af3cfb542e99db100ddef282b5f2024-12-20T07:10:36ZengStockholm University PressTellus: Series A, Dynamic Meteorology and Oceanography1600-08702024-11-01761206–226206–22610.16993/tellusa.40724039Topographic Steering of the Upper Arctic Ocean Circulation by Deep FlowsJohan Nilsson0https://orcid.org/0000-0002-9591-124XJan-Adrian H. Kallmyr1https://orcid.org/0000-0002-9372-1821Pål Erik Isachsen2https://orcid.org/0000-0003-1249-3052Department of Meteorology and Bolin Centre for Climate Research, Stockholm University, StockholmDepartment of Meteorology and Bolin Centre for Climate Research, Stockholm University, StockholmDepartment of Geosciences, University of Oslo, Oslo; Norwegian Meteorological Institute, OsloDynamically, the Arctic Ocean is characterised by the presence of closed f/H contours, where f is the Coriolis parameter and H the depth. On closed f/H contours, a net integrated surface wind stress can theoretically drive relatively strong near-bottom flows. Nevertheless, the Rossby number of the large-scale time-mean flow in the Arctic Ocean is estimated to be small, implying that the near-bottom flow should essentially be aligned with the f/H contours. Observations indicate that the time-mean surface flow also tends to follow the f/H contours, which in the Arctic are essentially controlled by H. To examine mechanisms that can organise the Arctic Ocean surface flow along the topography, we use a two-layer large-scale geostrophic model on an f-plane (exploiting that f/H variations are dominated by depth variations). The effect of time-dependent baroclinic eddies is represented as an eddy diffusion of the upper-layer thickness. We study how wind forcing, stratification, eddy diffusivity and bottom friction affect the topographic steering of the time-mean surface flow, introducing relevant non-dimensional parameters. The analyses suggest that the Arctic Ocean is in a regime where strong along-isobath near-bottom flows can align the buoyancy field and, thereby, the surface currents with the topography. We then discuss the model results in relation to satellite-derived surface currents in the Arctic Ocean and briefly consider additional mechanisms that can align surface flows with the topography.https://account.a.tellusjournals.se/index.php/su-j-tadmo/article/view/4072arctic ocean circulationtopographic steeringekman pumpingmesoscale eddies |
| spellingShingle | Johan Nilsson Jan-Adrian H. Kallmyr Pål Erik Isachsen Topographic Steering of the Upper Arctic Ocean Circulation by Deep Flows Tellus: Series A, Dynamic Meteorology and Oceanography arctic ocean circulation topographic steering ekman pumping mesoscale eddies |
| title | Topographic Steering of the Upper Arctic Ocean Circulation by Deep Flows |
| title_full | Topographic Steering of the Upper Arctic Ocean Circulation by Deep Flows |
| title_fullStr | Topographic Steering of the Upper Arctic Ocean Circulation by Deep Flows |
| title_full_unstemmed | Topographic Steering of the Upper Arctic Ocean Circulation by Deep Flows |
| title_short | Topographic Steering of the Upper Arctic Ocean Circulation by Deep Flows |
| title_sort | topographic steering of the upper arctic ocean circulation by deep flows |
| topic | arctic ocean circulation topographic steering ekman pumping mesoscale eddies |
| url | https://account.a.tellusjournals.se/index.php/su-j-tadmo/article/view/4072 |
| work_keys_str_mv | AT johannilsson topographicsteeringoftheupperarcticoceancirculationbydeepflows AT janadrianhkallmyr topographicsteeringoftheupperarcticoceancirculationbydeepflows AT palerikisachsen topographicsteeringoftheupperarcticoceancirculationbydeepflows |