2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response
Observed multidecadal trends in extratropical atmospheric flow, such as the positive trend in the North Atlantic Oscillation (NAO) index, may be attributable to a number of causes. This study addresses the question of whether the atmospheric trends may be caused by observed trends in oceanic boundar...
Main Authors: | , , |
---|---|
Other Authors: | |
Format: | Text |
Language: | English |
Subjects: | |
Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.383.9247 http://www.cgd.ucar.edu/cas/cdeser/Docs/magnusdottir.natlsstice_part1.jclim04.pdf |
id |
ftciteseerx:oai:CiteSeerX.psu:10.1.1.383.9247 |
---|---|
record_format |
openpolar |
spelling |
ftciteseerx:oai:CiteSeerX.psu:10.1.1.383.9247 2023-05-15T17:28:52+02:00 2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response Gudrun Magnusdottir Clara Deser R. Saravanan The Pennsylvania State University CiteSeerX Archives application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.383.9247 http://www.cgd.ucar.edu/cas/cdeser/Docs/magnusdottir.natlsstice_part1.jclim04.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.383.9247 http://www.cgd.ucar.edu/cas/cdeser/Docs/magnusdottir.natlsstice_part1.jclim04.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://www.cgd.ucar.edu/cas/cdeser/Docs/magnusdottir.natlsstice_part1.jclim04.pdf text ftciteseerx 2016-09-18T00:29:06Z Observed multidecadal trends in extratropical atmospheric flow, such as the positive trend in the North Atlantic Oscillation (NAO) index, may be attributable to a number of causes. This study addresses the question of whether the atmospheric trends may be caused by observed trends in oceanic boundary forcing. Experiments were carried out using the NCAR atmospheric general circulation model with specified sea surface temperature (SST) and sea ice anomalies confined to the North Atlantic sector. The spatial pattern of the anomalous forcing was chosen to be realistic in that it corresponds to the recent 40-yr trend in SST and sea ice, but the anomaly amplitude was exaggerated in order to make the response statistically more robust. The wintertime response to both types of forcing resembles the NAO to first order. Even for an exaggerated amplitude, the atmospheric response to the SST anomaly is quite weak compared to the observed positive trend in the NAO, but has the same sign, indicative of a weak positive feedback. The anomalies in sea ice extent are more efficient than SST anomalies at exciting an atmospheric response comparable in amplitude to the observed NAO trend. However, this atmospheric response has the opposite sign to the observed trend, indicative of a significant negative feedback associated with the sea ice forcing. Additional experiments using SST anomalies with opposite sign to the observed trend indicate that there are significant nonlinearities associated with the atmospheric response. The transient eddy response to the observed SST trend is consistent with the positive NAO response, with the North Atlantic storm track amplifying downstream and developing a more pronounced meridional tilt. In contrast, the storm track response to the observed sea ice trend corresponds to a weaker, southward-shifted, more zonal storm track, which is consistent with the negative NAO response. 1. Text North Atlantic North Atlantic oscillation Sea ice Unknown |
institution |
Open Polar |
collection |
Unknown |
op_collection_id |
ftciteseerx |
language |
English |
description |
Observed multidecadal trends in extratropical atmospheric flow, such as the positive trend in the North Atlantic Oscillation (NAO) index, may be attributable to a number of causes. This study addresses the question of whether the atmospheric trends may be caused by observed trends in oceanic boundary forcing. Experiments were carried out using the NCAR atmospheric general circulation model with specified sea surface temperature (SST) and sea ice anomalies confined to the North Atlantic sector. The spatial pattern of the anomalous forcing was chosen to be realistic in that it corresponds to the recent 40-yr trend in SST and sea ice, but the anomaly amplitude was exaggerated in order to make the response statistically more robust. The wintertime response to both types of forcing resembles the NAO to first order. Even for an exaggerated amplitude, the atmospheric response to the SST anomaly is quite weak compared to the observed positive trend in the NAO, but has the same sign, indicative of a weak positive feedback. The anomalies in sea ice extent are more efficient than SST anomalies at exciting an atmospheric response comparable in amplitude to the observed NAO trend. However, this atmospheric response has the opposite sign to the observed trend, indicative of a significant negative feedback associated with the sea ice forcing. Additional experiments using SST anomalies with opposite sign to the observed trend indicate that there are significant nonlinearities associated with the atmospheric response. The transient eddy response to the observed SST trend is consistent with the positive NAO response, with the North Atlantic storm track amplifying downstream and developing a more pronounced meridional tilt. In contrast, the storm track response to the observed sea ice trend corresponds to a weaker, southward-shifted, more zonal storm track, which is consistent with the negative NAO response. 1. |
author2 |
The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
Gudrun Magnusdottir Clara Deser R. Saravanan |
spellingShingle |
Gudrun Magnusdottir Clara Deser R. Saravanan 2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response |
author_facet |
Gudrun Magnusdottir Clara Deser R. Saravanan |
author_sort |
Gudrun Magnusdottir |
title |
2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response |
title_short |
2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response |
title_full |
2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response |
title_fullStr |
2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response |
title_full_unstemmed |
2004: The effects of North Atlantic SST and sea-ice anomalies on the winter circulation in CCM3. Part II: Direct and indirect components of the response |
title_sort |
2004: the effects of north atlantic sst and sea-ice anomalies on the winter circulation in ccm3. part ii: direct and indirect components of the response |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.383.9247 http://www.cgd.ucar.edu/cas/cdeser/Docs/magnusdottir.natlsstice_part1.jclim04.pdf |
genre |
North Atlantic North Atlantic oscillation Sea ice |
genre_facet |
North Atlantic North Atlantic oscillation Sea ice |
op_source |
http://www.cgd.ucar.edu/cas/cdeser/Docs/magnusdottir.natlsstice_part1.jclim04.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.383.9247 http://www.cgd.ucar.edu/cas/cdeser/Docs/magnusdottir.natlsstice_part1.jclim04.pdf |
op_rights |
Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
_version_ |
1766122003717160960 |