The thermohaline circulation during the Last Glacial Maximum and in the Present-Day climate
The thermohaline circulation (THC) corresponds to the large time- and spatial-scales ocean circulation associated with the transport of heat and salt, and is known to be an important factor controlling the climate variability. The large scales involved in the THC make it difficult to observe, and th...
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ftstockholmuniv:oai:DiVA.org:su-89011 2023-05-15T14:01:57+02:00 The thermohaline circulation during the Last Glacial Maximum and in the Present-Day climate Ballarotta, Maxime 2013 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89011 eng eng Meteorologiska institutionen (MISU) Stockholm : Department of Meteorology, Stockholm University http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89011 urn:isbn:978-91-7447-697-2 info:eu-repo/semantics/openAccess ocean model circulation LGM Oceanography Hydrology and Water Resources Oceanografi hydrologi och vattenresurser Doctoral thesis, comprehensive summary info:eu-repo/semantics/doctoralThesis text 2013 ftstockholmuniv 2023-02-23T21:42:10Z The thermohaline circulation (THC) corresponds to the large time- and spatial-scales ocean circulation associated with the transport of heat and salt, and is known to be an important factor controlling the climate variability. The large scales involved in the THC make it difficult to observe, and therefore the synergy of numerical models and climate proxy reconstructions is particularly relevant to study the characteristics of this circulation in the present and past climates. In this doctoral thesis, the THC during the Last Glacial Maximum (LGM) and the Present-Day (PD) is explored using a state-of-the-art Ocean General Circulation Model in its high- and low-resolution regimes. By comparing the LGM model outputs with the paleo-proxy reconstructions, it is shown that the high-resolution simulation improves the representation of the sea surface tem- peratures in the regions where the current structures appear to be complex, i.e., the western boundary currents (Agulhas, Kuroshio, Gulf Stream) and the Antarctic Circumpolar Current, although statistical comparisons with paleo- proxy reconstructions are not significantly improved on a global scale. The THC involves a superposition of processes acting at widely different spatial and temporal scales, from the geostrophic large-scale and slowly-varying flow to the mesoscale turbulent eddies and at even smaller-scale, the mixing generated by the internal wave field. Not all these processes can be properly resolved in numerical models, and thus need to be parameterized. Analyzing the THC in an eddy-permitting numerical model, it was found that the temporal scales required for diagnosing the Southern Ocean circulation should not exceed 1 month and the spatial scales needed to be taken into account must be smaller than 1°. Important changes in the nature and intensity of the THC were observed between the LGM and PD simulations. An estimation of the turnover times (i.e., the time it takes for the water parcel to make and entire loop on the Conveyor Belt) revealed that the ... Doctoral or Postdoctoral Thesis Antarc* Antarctic Southern Ocean Stockholm University: Publications (DiVA) Antarctic Southern Ocean The Antarctic |
institution |
Open Polar |
collection |
Stockholm University: Publications (DiVA) |
op_collection_id |
ftstockholmuniv |
language |
English |
topic |
ocean model circulation LGM Oceanography Hydrology and Water Resources Oceanografi hydrologi och vattenresurser |
spellingShingle |
ocean model circulation LGM Oceanography Hydrology and Water Resources Oceanografi hydrologi och vattenresurser Ballarotta, Maxime The thermohaline circulation during the Last Glacial Maximum and in the Present-Day climate |
topic_facet |
ocean model circulation LGM Oceanography Hydrology and Water Resources Oceanografi hydrologi och vattenresurser |
description |
The thermohaline circulation (THC) corresponds to the large time- and spatial-scales ocean circulation associated with the transport of heat and salt, and is known to be an important factor controlling the climate variability. The large scales involved in the THC make it difficult to observe, and therefore the synergy of numerical models and climate proxy reconstructions is particularly relevant to study the characteristics of this circulation in the present and past climates. In this doctoral thesis, the THC during the Last Glacial Maximum (LGM) and the Present-Day (PD) is explored using a state-of-the-art Ocean General Circulation Model in its high- and low-resolution regimes. By comparing the LGM model outputs with the paleo-proxy reconstructions, it is shown that the high-resolution simulation improves the representation of the sea surface tem- peratures in the regions where the current structures appear to be complex, i.e., the western boundary currents (Agulhas, Kuroshio, Gulf Stream) and the Antarctic Circumpolar Current, although statistical comparisons with paleo- proxy reconstructions are not significantly improved on a global scale. The THC involves a superposition of processes acting at widely different spatial and temporal scales, from the geostrophic large-scale and slowly-varying flow to the mesoscale turbulent eddies and at even smaller-scale, the mixing generated by the internal wave field. Not all these processes can be properly resolved in numerical models, and thus need to be parameterized. Analyzing the THC in an eddy-permitting numerical model, it was found that the temporal scales required for diagnosing the Southern Ocean circulation should not exceed 1 month and the spatial scales needed to be taken into account must be smaller than 1°. Important changes in the nature and intensity of the THC were observed between the LGM and PD simulations. An estimation of the turnover times (i.e., the time it takes for the water parcel to make and entire loop on the Conveyor Belt) revealed that the ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Ballarotta, Maxime |
author_facet |
Ballarotta, Maxime |
author_sort |
Ballarotta, Maxime |
title |
The thermohaline circulation during the Last Glacial Maximum and in the Present-Day climate |
title_short |
The thermohaline circulation during the Last Glacial Maximum and in the Present-Day climate |
title_full |
The thermohaline circulation during the Last Glacial Maximum and in the Present-Day climate |
title_fullStr |
The thermohaline circulation during the Last Glacial Maximum and in the Present-Day climate |
title_full_unstemmed |
The thermohaline circulation during the Last Glacial Maximum and in the Present-Day climate |
title_sort |
thermohaline circulation during the last glacial maximum and in the present-day climate |
publisher |
Meteorologiska institutionen (MISU) |
publishDate |
2013 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89011 |
geographic |
Antarctic Southern Ocean The Antarctic |
geographic_facet |
Antarctic Southern Ocean The Antarctic |
genre |
Antarc* Antarctic Southern Ocean |
genre_facet |
Antarc* Antarctic Southern Ocean |
op_relation |
http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89011 urn:isbn:978-91-7447-697-2 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766272014713094144 |