Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations
Open water in sea ice, such as leads and polynyas, plays a crucial role in determining the formation of deep- and bottom-water, as well as their long-term global properties and circulation. Ocean general circulation models (GCMs) designed for studies of the long-term thermohaline circulation have ty...
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fttexasamuniv:oai:repository.tamu.edu:1969.1/5746 2023-05-15T14:04:56+02:00 Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations Stoessel, Achim Chang, Ping Giese, Benjamin Wilheit, Thomas 2007-09-17T19:31:06Z http://hdl.handle.net/1969.1/5746 en_US eng Texas A&M University http://hdl.handle.net/1969.1/5746 enhancing sea ice ocean GCM Book Thesis 2007 fttexasamuniv 2014-03-30T08:53:37Z Open water in sea ice, such as leads and polynyas, plays a crucial role in determining the formation of deep- and bottom-water, as well as their long-term global properties and circulation. Ocean general circulation models (GCMs) designed for studies of the long-term thermohaline circulation have typically coarse resolution, making it inevitable to parameterize subgrid-scale features such as leads and convective plumes. In this study, a hierarchy of higher-resolution sea-ice models is developed to reduce uncertainties due to coarse resolution, while keeping the ocean component at coarse resolution to maintain the efficiency of the GCM to study the long-term deep-ocean properties and circulation. The higher-resolved sea-ice component is restricted to the Southern Ocean. Compared with the coarse sea-ice model, the intermediate, higher-resolution version yields more detailed coastal polynyas, a realistically sharp ice edge, and an overall enhanced lead fraction. The latter gives enhanced rates of Antarctic Bottom Water formation through enhanced near-boundary convection. Sensitivity experiments revealed coastal katabatic winds accounted for in the higher resolution version, are the main reason for producing such an effect. For a more realistic coastline, satellite passive-microwave data for fine-grid land/ice-shelf ?????? seaice/ ocean boundary were used. With a further enhancement of the resolution of the Southern Ocean??????s sea-ice component, a grid spacing of 22 km is reached. This is about the size of the pixel resolution of satellite-passive microwave data from which ice concentration is retrieved. This product is used in this study to validate the sea-ice component of the global ocean GCM. The overall performance of the high-resolution sea-ice component is encouraging, particularly the representation of the crucial coastal polynyas. Enhancing the resolution of the convection parameterization reduces spurious coarse-grid polynyas. Constraining the upper-ocean temperature and modifying the plume velocity removes unrealistic small-scale convection within the ice pack. The observed highfrequency variability along the ice edge is to some extent captured by exposing the ice pack to upper-ocean currents that mimic tidal variability. While these measures improve several characteristics of the Southern Ocean sea-ice pack, they deteriorate the global deepocean properties and circulation, calling for further refinements and tuning to arrive at presently observed conditions. Book Antarc* Antarctic ice pack Ice Shelf Sea ice Southern Ocean Texas A&M University Digital Repository Antarctic Southern Ocean |
institution |
Open Polar |
collection |
Texas A&M University Digital Repository |
op_collection_id |
fttexasamuniv |
language |
English |
topic |
enhancing sea ice ocean GCM |
spellingShingle |
enhancing sea ice ocean GCM Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations |
topic_facet |
enhancing sea ice ocean GCM |
description |
Open water in sea ice, such as leads and polynyas, plays a crucial role in determining the formation of deep- and bottom-water, as well as their long-term global properties and circulation. Ocean general circulation models (GCMs) designed for studies of the long-term thermohaline circulation have typically coarse resolution, making it inevitable to parameterize subgrid-scale features such as leads and convective plumes. In this study, a hierarchy of higher-resolution sea-ice models is developed to reduce uncertainties due to coarse resolution, while keeping the ocean component at coarse resolution to maintain the efficiency of the GCM to study the long-term deep-ocean properties and circulation. The higher-resolved sea-ice component is restricted to the Southern Ocean. Compared with the coarse sea-ice model, the intermediate, higher-resolution version yields more detailed coastal polynyas, a realistically sharp ice edge, and an overall enhanced lead fraction. The latter gives enhanced rates of Antarctic Bottom Water formation through enhanced near-boundary convection. Sensitivity experiments revealed coastal katabatic winds accounted for in the higher resolution version, are the main reason for producing such an effect. For a more realistic coastline, satellite passive-microwave data for fine-grid land/ice-shelf ?????? seaice/ ocean boundary were used. With a further enhancement of the resolution of the Southern Ocean??????s sea-ice component, a grid spacing of 22 km is reached. This is about the size of the pixel resolution of satellite-passive microwave data from which ice concentration is retrieved. This product is used in this study to validate the sea-ice component of the global ocean GCM. The overall performance of the high-resolution sea-ice component is encouraging, particularly the representation of the crucial coastal polynyas. Enhancing the resolution of the convection parameterization reduces spurious coarse-grid polynyas. Constraining the upper-ocean temperature and modifying the plume velocity removes unrealistic small-scale convection within the ice pack. The observed highfrequency variability along the ice edge is to some extent captured by exposing the ice pack to upper-ocean currents that mimic tidal variability. While these measures improve several characteristics of the Southern Ocean sea-ice pack, they deteriorate the global deepocean properties and circulation, calling for further refinements and tuning to arrive at presently observed conditions. |
author2 |
Stoessel, Achim Chang, Ping Giese, Benjamin Wilheit, Thomas |
format |
Book |
title |
Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations |
title_short |
Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations |
title_full |
Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations |
title_fullStr |
Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations |
title_full_unstemmed |
Enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations |
title_sort |
enhancing the resolution of sea ice in long-term global ocean general circulation model (gcm) integrations |
publisher |
Texas A&M University |
publishDate |
2007 |
url |
http://hdl.handle.net/1969.1/5746 |
geographic |
Antarctic Southern Ocean |
geographic_facet |
Antarctic Southern Ocean |
genre |
Antarc* Antarctic ice pack Ice Shelf Sea ice Southern Ocean |
genre_facet |
Antarc* Antarctic ice pack Ice Shelf Sea ice Southern Ocean |
op_relation |
http://hdl.handle.net/1969.1/5746 |
_version_ |
1766276397424181248 |