Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4
Most CMIP5 (Coupled Model Intercomparison Project Phase 5) models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross seas. To identify the mechanisms triggering Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean mo...
Published in: | Geoscientific Model Development |
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Copernicus Publications
2015
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00015103 2023-05-15T13:41:02+02:00 Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4 Heuzé, C. Ridley, J. K. Calvert, D. Stevens, D. P. Heywood, K. J. 2015-10 electronic https://doi.org/10.5194/gmd-8-3119-2015 https://noa.gwlb.de/receive/cop_mods_00015103 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00015058/gmd-8-3119-2015.pdf https://gmd.copernicus.org/articles/8/3119/2015/gmd-8-3119-2015.pdf eng eng Copernicus Publications Geoscientific Model Development -- http://www.bibliothek.uni-regensburg.de/ezeit/?2456725 -- http://www.geosci-model-dev.net/ -- 1991-9603 https://doi.org/10.5194/gmd-8-3119-2015 https://noa.gwlb.de/receive/cop_mods_00015103 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00015058/gmd-8-3119-2015.pdf https://gmd.copernicus.org/articles/8/3119/2015/gmd-8-3119-2015.pdf uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 2015 ftnonlinearchiv https://doi.org/10.5194/gmd-8-3119-2015 2022-02-08T22:54:45Z Most CMIP5 (Coupled Model Intercomparison Project Phase 5) models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross seas. To identify the mechanisms triggering Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean model NEMO3.4 forced by prescribed atmospheric fluxes. We vary the vertical velocity scale of the Langmuir turbulence, the fraction of turbulent kinetic energy transferred below the mixed layer, and the background diffusivity and run short simulations from 1980. All experiments exhibit deep convection in the Riiser-Larsen Sea in 1987; the origin is a positive sea ice anomaly in 1985, causing a shallow anomaly in mixed layer depth, hence anomalously warm surface waters and subsequent polynya opening. Modifying the vertical mixing impacts both the climatological state and the associated surface anomalies. The experiments with enhanced mixing exhibit colder surface waters and reduced deep convection. The experiments with decreased mixing give warmer surface waters, open larger polynyas causing more saline surface waters and have deep convection across the Weddell Sea until the simulations end. Extended experiments reveal an increase in the Drake Passage transport of 4 Sv each year deep convection occurs, leading to an unrealistically large transport at the end of the simulation. North Atlantic deep convection is not significantly affected by the changes in mixing parameters. As new climate model overflow parameterisations are developed to form Antarctic Bottom Water more realistically, we argue that models would benefit from stopping Southern Ocean deep convection, for example by increasing their vertical mixing. Article in Journal/Newspaper Antarc* Antarctic Drake Passage North Atlantic Riiser-Larsen Sea Sea ice Southern Ocean Weddell Sea Niedersächsisches Online-Archiv NOA Antarctic Drake Passage Langmuir ENVELOPE(-67.150,-67.150,-66.967,-66.967) Riiser-Larsen ENVELOPE(50.667,50.667,-66.783,-66.783) Riiser-Larsen Sea ENVELOPE(24.000,24.000,-68.000,-68.000) Southern Ocean Weddell Weddell Sea Geoscientific Model Development 8 10 3119 3130 |
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Niedersächsisches Online-Archiv NOA |
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ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Heuzé, C. Ridley, J. K. Calvert, D. Stevens, D. P. Heywood, K. J. Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4 |
topic_facet |
article Verlagsveröffentlichung |
description |
Most CMIP5 (Coupled Model Intercomparison Project Phase 5) models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross seas. To identify the mechanisms triggering Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean model NEMO3.4 forced by prescribed atmospheric fluxes. We vary the vertical velocity scale of the Langmuir turbulence, the fraction of turbulent kinetic energy transferred below the mixed layer, and the background diffusivity and run short simulations from 1980. All experiments exhibit deep convection in the Riiser-Larsen Sea in 1987; the origin is a positive sea ice anomaly in 1985, causing a shallow anomaly in mixed layer depth, hence anomalously warm surface waters and subsequent polynya opening. Modifying the vertical mixing impacts both the climatological state and the associated surface anomalies. The experiments with enhanced mixing exhibit colder surface waters and reduced deep convection. The experiments with decreased mixing give warmer surface waters, open larger polynyas causing more saline surface waters and have deep convection across the Weddell Sea until the simulations end. Extended experiments reveal an increase in the Drake Passage transport of 4 Sv each year deep convection occurs, leading to an unrealistically large transport at the end of the simulation. North Atlantic deep convection is not significantly affected by the changes in mixing parameters. As new climate model overflow parameterisations are developed to form Antarctic Bottom Water more realistically, we argue that models would benefit from stopping Southern Ocean deep convection, for example by increasing their vertical mixing. |
format |
Article in Journal/Newspaper |
author |
Heuzé, C. Ridley, J. K. Calvert, D. Stevens, D. P. Heywood, K. J. |
author_facet |
Heuzé, C. Ridley, J. K. Calvert, D. Stevens, D. P. Heywood, K. J. |
author_sort |
Heuzé, C. |
title |
Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4 |
title_short |
Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4 |
title_full |
Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4 |
title_fullStr |
Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4 |
title_full_unstemmed |
Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO3.4 |
title_sort |
increasing vertical mixing to reduce southern ocean deep convection in nemo3.4 |
publisher |
Copernicus Publications |
publishDate |
2015 |
url |
https://doi.org/10.5194/gmd-8-3119-2015 https://noa.gwlb.de/receive/cop_mods_00015103 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00015058/gmd-8-3119-2015.pdf https://gmd.copernicus.org/articles/8/3119/2015/gmd-8-3119-2015.pdf |
long_lat |
ENVELOPE(-67.150,-67.150,-66.967,-66.967) ENVELOPE(50.667,50.667,-66.783,-66.783) ENVELOPE(24.000,24.000,-68.000,-68.000) |
geographic |
Antarctic Drake Passage Langmuir Riiser-Larsen Riiser-Larsen Sea Southern Ocean Weddell Weddell Sea |
geographic_facet |
Antarctic Drake Passage Langmuir Riiser-Larsen Riiser-Larsen Sea Southern Ocean Weddell Weddell Sea |
genre |
Antarc* Antarctic Drake Passage North Atlantic Riiser-Larsen Sea Sea ice Southern Ocean Weddell Sea |
genre_facet |
Antarc* Antarctic Drake Passage North Atlantic Riiser-Larsen Sea Sea ice Southern Ocean Weddell Sea |
op_relation |
Geoscientific Model Development -- http://www.bibliothek.uni-regensburg.de/ezeit/?2456725 -- http://www.geosci-model-dev.net/ -- 1991-9603 https://doi.org/10.5194/gmd-8-3119-2015 https://noa.gwlb.de/receive/cop_mods_00015103 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00015058/gmd-8-3119-2015.pdf https://gmd.copernicus.org/articles/8/3119/2015/gmd-8-3119-2015.pdf |
op_rights |
uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/gmd-8-3119-2015 |
container_title |
Geoscientific Model Development |
container_volume |
8 |
container_issue |
10 |
container_start_page |
3119 |
op_container_end_page |
3130 |
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1766145029262278656 |