2008: Timely detection of changes in the meridional overturning circulation at 26°N in the Atlantic
It is investigated how changes in the North Atlantic meridional overturning circulation (MOC) might be reliably detected within a few decades, using the observations provided by the RAPID-MOC 26°N array. Previously, detectability of MOC changes had been investigated with a univariate MOC time series...
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ftciteseerx:oai:CiteSeerX.psu:10.1.1.460.3398 2023-05-15T17:36:15+02:00 2008: Timely detection of changes in the meridional overturning circulation at 26°N in the Atlantic Johanna Baehr Helmuth Haak Steven Alderson Stuart A. Cunningham Johann H. Jungclaus Jochem Marotzke The Pennsylvania State University CiteSeerX Archives application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.460.3398 http://pubman.mpdl.mpg.de/pubman/item/escidoc:994276:4/component/escidoc:1626191/2007JCLI1686.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.460.3398 http://pubman.mpdl.mpg.de/pubman/item/escidoc:994276:4/component/escidoc:1626191/2007JCLI1686.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://pubman.mpdl.mpg.de/pubman/item/escidoc:994276:4/component/escidoc:1626191/2007JCLI1686.pdf text ftciteseerx 2016-01-08T06:32:24Z It is investigated how changes in the North Atlantic meridional overturning circulation (MOC) might be reliably detected within a few decades, using the observations provided by the RAPID-MOC 26°N array. Previously, detectability of MOC changes had been investigated with a univariate MOC time series exhib-iting strong internal variability, which would prohibit the detection of MOC changes within a few decades. Here, a modification of K. Hasselmann’s fingerprint technique is used: (simulated) observations are pro-jected onto a time-independent spatial pattern of natural variability to derive a time-dependent detection variable. The fixed spatial pattern of natural variability is derived by regressing the zonal density gradient along 26°N against the strength of the MOC at 26°N within the coupled ECHAM5/Max Planck Institute Ocean Model’s (MPI-OM) control climate simulation. This pattern is confirmed against the observed anomalies found between the 1957 and the 2004 hydrographic occupations of the section. Onto this fixed spatial pattern of natural variability, both the existing hydrographic observations and simulated observa-tions mimicking the RAPID-MOC 26°N array in three realizations of the Intergovernmental Panel on Climate Change (IPCC) scenario A1B are projected. For a random observation error of 0.01 kg m3, and only using zonal density gradients between 1700- and 3100-m depth, statistically significant detection occurs with 95 % reliability after about 30 yr, in the model and climate change scenario analyzed here. Compared to using a single MOC time series as the detection variable, continuous observations of zonal density gradients reduce the detection time by 50%. For the five hydrographic occupations of the 26°N transect, none of the analyzed depth ranges shows a significant trend between 1957 and 2004, implying that there was no MOC trend over the past 50 yr. 1. Text North Atlantic Unknown |
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description |
It is investigated how changes in the North Atlantic meridional overturning circulation (MOC) might be reliably detected within a few decades, using the observations provided by the RAPID-MOC 26°N array. Previously, detectability of MOC changes had been investigated with a univariate MOC time series exhib-iting strong internal variability, which would prohibit the detection of MOC changes within a few decades. Here, a modification of K. Hasselmann’s fingerprint technique is used: (simulated) observations are pro-jected onto a time-independent spatial pattern of natural variability to derive a time-dependent detection variable. The fixed spatial pattern of natural variability is derived by regressing the zonal density gradient along 26°N against the strength of the MOC at 26°N within the coupled ECHAM5/Max Planck Institute Ocean Model’s (MPI-OM) control climate simulation. This pattern is confirmed against the observed anomalies found between the 1957 and the 2004 hydrographic occupations of the section. Onto this fixed spatial pattern of natural variability, both the existing hydrographic observations and simulated observa-tions mimicking the RAPID-MOC 26°N array in three realizations of the Intergovernmental Panel on Climate Change (IPCC) scenario A1B are projected. For a random observation error of 0.01 kg m3, and only using zonal density gradients between 1700- and 3100-m depth, statistically significant detection occurs with 95 % reliability after about 30 yr, in the model and climate change scenario analyzed here. Compared to using a single MOC time series as the detection variable, continuous observations of zonal density gradients reduce the detection time by 50%. For the five hydrographic occupations of the 26°N transect, none of the analyzed depth ranges shows a significant trend between 1957 and 2004, implying that there was no MOC trend over the past 50 yr. 1. |
author2 |
The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
Johanna Baehr Helmuth Haak Steven Alderson Stuart A. Cunningham Johann H. Jungclaus Jochem Marotzke |
spellingShingle |
Johanna Baehr Helmuth Haak Steven Alderson Stuart A. Cunningham Johann H. Jungclaus Jochem Marotzke 2008: Timely detection of changes in the meridional overturning circulation at 26°N in the Atlantic |
author_facet |
Johanna Baehr Helmuth Haak Steven Alderson Stuart A. Cunningham Johann H. Jungclaus Jochem Marotzke |
author_sort |
Johanna Baehr |
title |
2008: Timely detection of changes in the meridional overturning circulation at 26°N in the Atlantic |
title_short |
2008: Timely detection of changes in the meridional overturning circulation at 26°N in the Atlantic |
title_full |
2008: Timely detection of changes in the meridional overturning circulation at 26°N in the Atlantic |
title_fullStr |
2008: Timely detection of changes in the meridional overturning circulation at 26°N in the Atlantic |
title_full_unstemmed |
2008: Timely detection of changes in the meridional overturning circulation at 26°N in the Atlantic |
title_sort |
2008: timely detection of changes in the meridional overturning circulation at 26°n in the atlantic |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.460.3398 http://pubman.mpdl.mpg.de/pubman/item/escidoc:994276:4/component/escidoc:1626191/2007JCLI1686.pdf |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
http://pubman.mpdl.mpg.de/pubman/item/escidoc:994276:4/component/escidoc:1626191/2007JCLI1686.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.460.3398 http://pubman.mpdl.mpg.de/pubman/item/escidoc:994276:4/component/escidoc:1626191/2007JCLI1686.pdf |
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Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
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