The hydrography of the Mozambique Channel from six years of continuous temperature, salinity, and velocity observations
Temperature, salinity and velocity data are presented, along with the estimated volume transport, from seven full-length deep sea moorings placed across the narrowest part of the Mozambique Channel, southwest Indian Ocean, during the period November 2003 to December 2009. The dominant water mass in...
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ftunivutrecht:oai:dspace.library.uu.nl:1874/275970 2023-05-15T13:47:13+02:00 The hydrography of the Mozambique Channel from six years of continuous temperature, salinity, and velocity observations Ullgren, J.E. Aken, H.M. van Ridderinkhof, H. Ruijter, W.P.M. de 2012 image/pdf http://dspace.library.uu.nl/handle/1874/275970 en eng 0967-0637 http://dspace.library.uu.nl/handle/1874/275970 info:eu-repo/semantics/ClosedAccess Aardwetenschappen Natuur- en sterrenkunde Mozambique Channel Indian ocean Mesoscale eddies Interannual variability Time series Long-term observations Article 2012 ftunivutrecht 2021-07-01T21:25:51Z Temperature, salinity and velocity data are presented, along with the estimated volume transport, from seven full-length deep sea moorings placed across the narrowest part of the Mozambique Channel, southwest Indian Ocean, during the period November 2003 to December 2009. The dominant water mass in the upper layer is Sub-Tropical Surface Water (STSW) which overlies South Indian Central Water (SICW), and is normally capped by fresher Tropical Surface Water (TSW). Upper ocean salinity increased through 2005 as a result of saline STSW taking up a relatively larger part of the upper layer, at the expense of TSW. Upper waters are on average warmer and lighter in the central Channel than on the sides. Throughout the upper 1.5 km of the water column there is large hydrographic variability, short-term as well as interannual, and in particular at frequencies (four to seven cycles per year) associated with the southward passage of anticyclonic Mozambique Channel eddies. The eddies have a strong T–S signal, in the upper and central waters as well as on the intermediate level, as the eddies usually carry saline Red Sea Water (RSW) in their core. While the interannual frequency band displays an east–west gradient with higher temperature variance on the western side, the eddy frequency band shows highest variance in the centre of the Channel, where the eddy band contains about 40% of the total isopycnal hydrographic variability. Throughout the >6 years of measurements, the frequency and characteristics of eddies vary between periods, both in terms of strength and vertical structure of eddy T–S signals. These changes contribute to the interannual variability of water mass properties: an increase in central water salinity to a maximum in late 2007 coincided with a period of unusually frequent eddies with strong salinity signals. The warmest and most saline deep water is found within the northward flowing Mozambique Undercurrent, on the western side of the Channel. The Undercurrent has two cores: an intermediate one mainly containing diluted Antarctic Intermediate Water (AAIW), and a deep one consisting of North Atlantic Deep Water (NADW). In the intermediate core, T–S properties are strongly correlated with current velocity, probably because of the strong salinity gradient at the interface between Red Sea Water (RSW) and AAIW. In the deep core, velocity and hydrographic time series do not correlate on a daily basis, but they do at longer time scales. Article in Journal/Newspaper Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic Utrecht University Repository Antarctic Indian |
institution |
Open Polar |
collection |
Utrecht University Repository |
op_collection_id |
ftunivutrecht |
language |
English |
topic |
Aardwetenschappen Natuur- en sterrenkunde Mozambique Channel Indian ocean Mesoscale eddies Interannual variability Time series Long-term observations |
spellingShingle |
Aardwetenschappen Natuur- en sterrenkunde Mozambique Channel Indian ocean Mesoscale eddies Interannual variability Time series Long-term observations Ullgren, J.E. Aken, H.M. van Ridderinkhof, H. Ruijter, W.P.M. de The hydrography of the Mozambique Channel from six years of continuous temperature, salinity, and velocity observations |
topic_facet |
Aardwetenschappen Natuur- en sterrenkunde Mozambique Channel Indian ocean Mesoscale eddies Interannual variability Time series Long-term observations |
description |
Temperature, salinity and velocity data are presented, along with the estimated volume transport, from seven full-length deep sea moorings placed across the narrowest part of the Mozambique Channel, southwest Indian Ocean, during the period November 2003 to December 2009. The dominant water mass in the upper layer is Sub-Tropical Surface Water (STSW) which overlies South Indian Central Water (SICW), and is normally capped by fresher Tropical Surface Water (TSW). Upper ocean salinity increased through 2005 as a result of saline STSW taking up a relatively larger part of the upper layer, at the expense of TSW. Upper waters are on average warmer and lighter in the central Channel than on the sides. Throughout the upper 1.5 km of the water column there is large hydrographic variability, short-term as well as interannual, and in particular at frequencies (four to seven cycles per year) associated with the southward passage of anticyclonic Mozambique Channel eddies. The eddies have a strong T–S signal, in the upper and central waters as well as on the intermediate level, as the eddies usually carry saline Red Sea Water (RSW) in their core. While the interannual frequency band displays an east–west gradient with higher temperature variance on the western side, the eddy frequency band shows highest variance in the centre of the Channel, where the eddy band contains about 40% of the total isopycnal hydrographic variability. Throughout the >6 years of measurements, the frequency and characteristics of eddies vary between periods, both in terms of strength and vertical structure of eddy T–S signals. These changes contribute to the interannual variability of water mass properties: an increase in central water salinity to a maximum in late 2007 coincided with a period of unusually frequent eddies with strong salinity signals. The warmest and most saline deep water is found within the northward flowing Mozambique Undercurrent, on the western side of the Channel. The Undercurrent has two cores: an intermediate one mainly containing diluted Antarctic Intermediate Water (AAIW), and a deep one consisting of North Atlantic Deep Water (NADW). In the intermediate core, T–S properties are strongly correlated with current velocity, probably because of the strong salinity gradient at the interface between Red Sea Water (RSW) and AAIW. In the deep core, velocity and hydrographic time series do not correlate on a daily basis, but they do at longer time scales. |
format |
Article in Journal/Newspaper |
author |
Ullgren, J.E. Aken, H.M. van Ridderinkhof, H. Ruijter, W.P.M. de |
author_facet |
Ullgren, J.E. Aken, H.M. van Ridderinkhof, H. Ruijter, W.P.M. de |
author_sort |
Ullgren, J.E. |
title |
The hydrography of the Mozambique Channel from six years of continuous temperature, salinity, and velocity observations |
title_short |
The hydrography of the Mozambique Channel from six years of continuous temperature, salinity, and velocity observations |
title_full |
The hydrography of the Mozambique Channel from six years of continuous temperature, salinity, and velocity observations |
title_fullStr |
The hydrography of the Mozambique Channel from six years of continuous temperature, salinity, and velocity observations |
title_full_unstemmed |
The hydrography of the Mozambique Channel from six years of continuous temperature, salinity, and velocity observations |
title_sort |
hydrography of the mozambique channel from six years of continuous temperature, salinity, and velocity observations |
publishDate |
2012 |
url |
http://dspace.library.uu.nl/handle/1874/275970 |
geographic |
Antarctic Indian |
geographic_facet |
Antarctic Indian |
genre |
Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic |
genre_facet |
Antarc* Antarctic NADW North Atlantic Deep Water North Atlantic |
op_relation |
0967-0637 http://dspace.library.uu.nl/handle/1874/275970 |
op_rights |
info:eu-repo/semantics/ClosedAccess |
_version_ |
1766246787476094976 |