Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing
It is well known that glacial periods were punctuated by abrupt climate changes, with large impacts on air temperature, precipitation, and ocean circulation across the globe. However, the long-held idea that freshwater forcing, caused by massive iceberg discharges, was the driving force behind these...
Published in: | Climate of the Past |
---|---|
Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2016
|
Subjects: | |
Online Access: | https://doi.org/10.5194/cp-12-1663-2016 https://noa.gwlb.de/receive/cop_mods_00011654 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00011611/cp-12-1663-2016.pdf https://cp.copernicus.org/articles/12/1663/2016/cp-12-1663-2016.pdf |
id |
ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00011654 |
---|---|
record_format |
openpolar |
spelling |
ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00011654 2023-05-15T17:32:32+02:00 Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing Brown, Nicolas Galbraith, Eric D. 2016-08 electronic https://doi.org/10.5194/cp-12-1663-2016 https://noa.gwlb.de/receive/cop_mods_00011654 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00011611/cp-12-1663-2016.pdf https://cp.copernicus.org/articles/12/1663/2016/cp-12-1663-2016.pdf eng eng Copernicus Publications Climate of the Past -- http://www.copernicus.org/EGU/cp/cp/published_papers.html -- http://www.bibliothek.uni-regensburg.de/ezeit/?2217985 -- 1814-9332 https://doi.org/10.5194/cp-12-1663-2016 https://noa.gwlb.de/receive/cop_mods_00011654 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00011611/cp-12-1663-2016.pdf https://cp.copernicus.org/articles/12/1663/2016/cp-12-1663-2016.pdf uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 2016 ftnonlinearchiv https://doi.org/10.5194/cp-12-1663-2016 2022-02-08T22:56:25Z It is well known that glacial periods were punctuated by abrupt climate changes, with large impacts on air temperature, precipitation, and ocean circulation across the globe. However, the long-held idea that freshwater forcing, caused by massive iceberg discharges, was the driving force behind these changes has been questioned in recent years. This throws into doubt the abundant literature on modelling abrupt climate change through “hosing” experiments, whereby the Atlantic Meridional Overturning Circulation (AMOC) is interrupted by an injection of freshwater to the North Atlantic: if some, or all, abrupt climate change was not driven by freshwater input, could its character have been very different than the typical hosed experiments? Here, we describe spontaneous, unhosed oscillations in AMOC strength that occur in a global coupled ocean–atmosphere model when integrated under a particular background climate state. We compare these unhosed oscillations to hosed oscillations under a range of background climate states in order to examine how the global imprint of AMOC variations depends on whether or not they result from external freshwater input. Our comparison includes surface air temperature, precipitation, dissolved oxygen concentrations in the intermediate-depth ocean, and marine export production. The results show that the background climate state has a significant impact on the character of the freshwater-forced AMOC interruptions in this model, with particularly marked variations in tropical precipitation and in the North Pacific circulation. Despite these differences, the first-order patterns of response to AMOC interruptions are quite consistent among all simulations, implying that the ocean–sea ice–atmosphere dynamics associated with an AMOC weakening dominate the global response, regardless of whether or not freshwater input is the cause. Nonetheless, freshwater addition leads to a more complete shutdown of the AMOC than occurs in the unhosed oscillations, with amplified global impacts, evocative of Heinrich stadials. In addition, freshwater inputs can directly impact the strength of other polar haloclines, particularly that of the Southern Ocean, to which freshwater can be transported relatively quickly after injection in the North Atlantic. Article in Journal/Newspaper North Atlantic Sea ice Southern Ocean Niedersächsisches Online-Archiv NOA Pacific Southern Ocean Climate of the Past 12 8 1663 1679 |
institution |
Open Polar |
collection |
Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Brown, Nicolas Galbraith, Eric D. Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing |
topic_facet |
article Verlagsveröffentlichung |
description |
It is well known that glacial periods were punctuated by abrupt climate changes, with large impacts on air temperature, precipitation, and ocean circulation across the globe. However, the long-held idea that freshwater forcing, caused by massive iceberg discharges, was the driving force behind these changes has been questioned in recent years. This throws into doubt the abundant literature on modelling abrupt climate change through “hosing” experiments, whereby the Atlantic Meridional Overturning Circulation (AMOC) is interrupted by an injection of freshwater to the North Atlantic: if some, or all, abrupt climate change was not driven by freshwater input, could its character have been very different than the typical hosed experiments? Here, we describe spontaneous, unhosed oscillations in AMOC strength that occur in a global coupled ocean–atmosphere model when integrated under a particular background climate state. We compare these unhosed oscillations to hosed oscillations under a range of background climate states in order to examine how the global imprint of AMOC variations depends on whether or not they result from external freshwater input. Our comparison includes surface air temperature, precipitation, dissolved oxygen concentrations in the intermediate-depth ocean, and marine export production. The results show that the background climate state has a significant impact on the character of the freshwater-forced AMOC interruptions in this model, with particularly marked variations in tropical precipitation and in the North Pacific circulation. Despite these differences, the first-order patterns of response to AMOC interruptions are quite consistent among all simulations, implying that the ocean–sea ice–atmosphere dynamics associated with an AMOC weakening dominate the global response, regardless of whether or not freshwater input is the cause. Nonetheless, freshwater addition leads to a more complete shutdown of the AMOC than occurs in the unhosed oscillations, with amplified global impacts, evocative of Heinrich stadials. In addition, freshwater inputs can directly impact the strength of other polar haloclines, particularly that of the Southern Ocean, to which freshwater can be transported relatively quickly after injection in the North Atlantic. |
format |
Article in Journal/Newspaper |
author |
Brown, Nicolas Galbraith, Eric D. |
author_facet |
Brown, Nicolas Galbraith, Eric D. |
author_sort |
Brown, Nicolas |
title |
Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing |
title_short |
Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing |
title_full |
Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing |
title_fullStr |
Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing |
title_full_unstemmed |
Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing |
title_sort |
hosed vs. unhosed: interruptions of the atlantic meridional overturning circulation in a global coupled model, with and without freshwater forcing |
publisher |
Copernicus Publications |
publishDate |
2016 |
url |
https://doi.org/10.5194/cp-12-1663-2016 https://noa.gwlb.de/receive/cop_mods_00011654 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00011611/cp-12-1663-2016.pdf https://cp.copernicus.org/articles/12/1663/2016/cp-12-1663-2016.pdf |
geographic |
Pacific Southern Ocean |
geographic_facet |
Pacific Southern Ocean |
genre |
North Atlantic Sea ice Southern Ocean |
genre_facet |
North Atlantic Sea ice Southern Ocean |
op_relation |
Climate of the Past -- http://www.copernicus.org/EGU/cp/cp/published_papers.html -- http://www.bibliothek.uni-regensburg.de/ezeit/?2217985 -- 1814-9332 https://doi.org/10.5194/cp-12-1663-2016 https://noa.gwlb.de/receive/cop_mods_00011654 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00011611/cp-12-1663-2016.pdf https://cp.copernicus.org/articles/12/1663/2016/cp-12-1663-2016.pdf |
op_rights |
uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/cp-12-1663-2016 |
container_title |
Climate of the Past |
container_volume |
12 |
container_issue |
8 |
container_start_page |
1663 |
op_container_end_page |
1679 |
_version_ |
1766130710747283456 |