The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations
Warm Atlantic-origin waters are modified in the Lofoten Basin in the Nordic Seas on their way toward the Arctic. An energetic eddy field redistributes these waters in the basin. Retained for extended periods, the warm waters result in large surface heat losses to the atmosphere and an impact on fish...
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ftcopernicus:oai:publications.copernicus.org:osd90332 2023-05-15T15:17:05+02:00 The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations Dugstad, Johannes S. Isachsen, Pål Erik Fer, Ilker 2020-10-30 application/pdf https://doi.org/10.5194/os-2020-103 https://os.copernicus.org/preprints/os-2020-103/ eng eng doi:10.5194/os-2020-103 https://os.copernicus.org/preprints/os-2020-103/ eISSN: 1812-0792 Text 2020 ftcopernicus https://doi.org/10.5194/os-2020-103 2020-11-02T17:22:13Z Warm Atlantic-origin waters are modified in the Lofoten Basin in the Nordic Seas on their way toward the Arctic. An energetic eddy field redistributes these waters in the basin. Retained for extended periods, the warm waters result in large surface heat losses to the atmosphere and an impact on fisheries and regional climate. Here, we describe the eddy field in the Lofoten Basin by analysing Lagrangian simulations forced by a high-resolution numerical model. We obtain trajectories of particles seeded at three levels: near the surface, at 200 m and 500 m depth, using 2D and 3D velocity fields. About 200,000 particle trajectories are analyzed from each level and each simulation. Using multivariate wavelet ridge analysis, we identify coherent cyclonic and anticyclonic vortices in the trajectories and describe their characteristics. We then compare the evolution of water properties inside cyclones and anticyclones as well as in the ambient flow outside vortices. As measured from Lagrangian particles, anticyclones have longer lifetimes than cyclones (16–24 days compared to 13–19 days), larger radius (20–22 km compared to 17–19 km) and a more circular shape (ellipse linearity of 0.45–0.50 compared to 0.51–0.57). The angular frequencies for cyclones and anticyclones have similar magnitudes (absolute values of about 0.05 f ). The anticyclones are characterized by warm temperature anomalies whereas cyclones are colder than the background state. Along their path, water parcels in anticyclones cool at a rate of 0.02–0.04 °C/day while those in cyclones warm at a rate of 0.01–0.02 °C/day. Water parcels experience a net downward motion in anticyclones and upward motion in cyclones, often found to be related to changes in temperature and density. The along-path changes of temperature, density and depth are smaller for particles in the ambient flow. An analysis of the net temperature and vorticity fluxes into the Lofoten Basin shows that while vortices contribute significantly to the heat and vorticity budgets, they only cover a small fraction of the domain area (about 6 %). The ambient flow, including filaments and other non-coherent variability undetected by the ridge analysis, hence plays a major role in closing the budgets of the basin. Text Arctic Lofoten Nordic Seas Copernicus Publications: E-Journals Arctic Lofoten Lofoten Basin ENVELOPE(4.000,4.000,70.000,70.000) |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Warm Atlantic-origin waters are modified in the Lofoten Basin in the Nordic Seas on their way toward the Arctic. An energetic eddy field redistributes these waters in the basin. Retained for extended periods, the warm waters result in large surface heat losses to the atmosphere and an impact on fisheries and regional climate. Here, we describe the eddy field in the Lofoten Basin by analysing Lagrangian simulations forced by a high-resolution numerical model. We obtain trajectories of particles seeded at three levels: near the surface, at 200 m and 500 m depth, using 2D and 3D velocity fields. About 200,000 particle trajectories are analyzed from each level and each simulation. Using multivariate wavelet ridge analysis, we identify coherent cyclonic and anticyclonic vortices in the trajectories and describe their characteristics. We then compare the evolution of water properties inside cyclones and anticyclones as well as in the ambient flow outside vortices. As measured from Lagrangian particles, anticyclones have longer lifetimes than cyclones (16–24 days compared to 13–19 days), larger radius (20–22 km compared to 17–19 km) and a more circular shape (ellipse linearity of 0.45–0.50 compared to 0.51–0.57). The angular frequencies for cyclones and anticyclones have similar magnitudes (absolute values of about 0.05 f ). The anticyclones are characterized by warm temperature anomalies whereas cyclones are colder than the background state. Along their path, water parcels in anticyclones cool at a rate of 0.02–0.04 °C/day while those in cyclones warm at a rate of 0.01–0.02 °C/day. Water parcels experience a net downward motion in anticyclones and upward motion in cyclones, often found to be related to changes in temperature and density. The along-path changes of temperature, density and depth are smaller for particles in the ambient flow. An analysis of the net temperature and vorticity fluxes into the Lofoten Basin shows that while vortices contribute significantly to the heat and vorticity budgets, they only cover a small fraction of the domain area (about 6 %). The ambient flow, including filaments and other non-coherent variability undetected by the ridge analysis, hence plays a major role in closing the budgets of the basin. |
format |
Text |
author |
Dugstad, Johannes S. Isachsen, Pål Erik Fer, Ilker |
spellingShingle |
Dugstad, Johannes S. Isachsen, Pål Erik Fer, Ilker The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations |
author_facet |
Dugstad, Johannes S. Isachsen, Pål Erik Fer, Ilker |
author_sort |
Dugstad, Johannes S. |
title |
The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations |
title_short |
The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations |
title_full |
The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations |
title_fullStr |
The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations |
title_full_unstemmed |
The mesoscale eddy field in the Lofoten Basin from high-resolution Lagrangian simulations |
title_sort |
mesoscale eddy field in the lofoten basin from high-resolution lagrangian simulations |
publishDate |
2020 |
url |
https://doi.org/10.5194/os-2020-103 https://os.copernicus.org/preprints/os-2020-103/ |
long_lat |
ENVELOPE(4.000,4.000,70.000,70.000) |
geographic |
Arctic Lofoten Lofoten Basin |
geographic_facet |
Arctic Lofoten Lofoten Basin |
genre |
Arctic Lofoten Nordic Seas |
genre_facet |
Arctic Lofoten Nordic Seas |
op_source |
eISSN: 1812-0792 |
op_relation |
doi:10.5194/os-2020-103 https://os.copernicus.org/preprints/os-2020-103/ |
op_doi |
https://doi.org/10.5194/os-2020-103 |
_version_ |
1766347365488263168 |