Surface buoyancy control of millennial-scale variations of the Atlantic meridional ocean circulation
Dansgaard-Oeschger (DO) events are a pervasive feature of glacial climates. It is widely accepted that the associated changes in climate, which are most pronounced in the North Atlantic region, are caused by abrupt changes in the strength and/or latitude reach of the Atlantic meridional overturning...
Main Authors: | , , , |
---|---|
Format: | Text |
Language: | English |
Published: |
2024
|
Subjects: | |
Online Access: | https://doi.org/10.5194/egusphere-2024-819 https://egusphere.copernicus.org/preprints/2024/egusphere-2024-819/ |
id |
ftcopernicus:oai:publications.copernicus.org:egusphere118896 |
---|---|
record_format |
openpolar |
spelling |
ftcopernicus:oai:publications.copernicus.org:egusphere118896 2024-06-23T07:54:50+00:00 Surface buoyancy control of millennial-scale variations of the Atlantic meridional ocean circulation Willeit, Matteo Ganopolski, Andrey Edwards, Neil R. Rahmstorf, Stefan 2024-03-25 application/pdf https://doi.org/10.5194/egusphere-2024-819 https://egusphere.copernicus.org/preprints/2024/egusphere-2024-819/ eng eng doi:10.5194/egusphere-2024-819 https://egusphere.copernicus.org/preprints/2024/egusphere-2024-819/ eISSN: Text 2024 ftcopernicus https://doi.org/10.5194/egusphere-2024-819 2024-06-13T01:23:00Z Dansgaard-Oeschger (DO) events are a pervasive feature of glacial climates. It is widely accepted that the associated changes in climate, which are most pronounced in the North Atlantic region, are caused by abrupt changes in the strength and/or latitude reach of the Atlantic meridional overturning circulation (AMOC), possibly originating from spontaneous transitions in the ocean-sea-ice-atmosphere system. Here we use an Earth System Model that produces DO-like events to show that the climate conditions under which millennial-scale AMOC variations occur are controlled by the surface ocean buoyancy flux. In particular, we find that the present day-like convection pattern with deep water formation in the Labrador and Nordic Seas becomes unstable when the buoyancy flux integrated over the northern North Atlantic turns from negative to positive. It is in the proximity of this point that the model produces transitions between different convection patterns associated with strong and weak AMOC states. The buoyancy flux depends on the surface freshwater and heat fluxes and on sea surface temperature through the temperature dependence of the thermal expansion coefficient of seawater. We find that larger ice sheets tend to stabilize convection by decreasing the net freshwater flux while CO 2 -induced cooling decreases buoyancy loss and destabilizes convection. These results help to explain the conditions under which DO events appear, and are a step towards an improved understanding of the mechanisms of abrupt climate changes. Text Nordic Seas North Atlantic Sea ice Copernicus Publications: E-Journals |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Dansgaard-Oeschger (DO) events are a pervasive feature of glacial climates. It is widely accepted that the associated changes in climate, which are most pronounced in the North Atlantic region, are caused by abrupt changes in the strength and/or latitude reach of the Atlantic meridional overturning circulation (AMOC), possibly originating from spontaneous transitions in the ocean-sea-ice-atmosphere system. Here we use an Earth System Model that produces DO-like events to show that the climate conditions under which millennial-scale AMOC variations occur are controlled by the surface ocean buoyancy flux. In particular, we find that the present day-like convection pattern with deep water formation in the Labrador and Nordic Seas becomes unstable when the buoyancy flux integrated over the northern North Atlantic turns from negative to positive. It is in the proximity of this point that the model produces transitions between different convection patterns associated with strong and weak AMOC states. The buoyancy flux depends on the surface freshwater and heat fluxes and on sea surface temperature through the temperature dependence of the thermal expansion coefficient of seawater. We find that larger ice sheets tend to stabilize convection by decreasing the net freshwater flux while CO 2 -induced cooling decreases buoyancy loss and destabilizes convection. These results help to explain the conditions under which DO events appear, and are a step towards an improved understanding of the mechanisms of abrupt climate changes. |
format |
Text |
author |
Willeit, Matteo Ganopolski, Andrey Edwards, Neil R. Rahmstorf, Stefan |
spellingShingle |
Willeit, Matteo Ganopolski, Andrey Edwards, Neil R. Rahmstorf, Stefan Surface buoyancy control of millennial-scale variations of the Atlantic meridional ocean circulation |
author_facet |
Willeit, Matteo Ganopolski, Andrey Edwards, Neil R. Rahmstorf, Stefan |
author_sort |
Willeit, Matteo |
title |
Surface buoyancy control of millennial-scale variations of the Atlantic meridional ocean circulation |
title_short |
Surface buoyancy control of millennial-scale variations of the Atlantic meridional ocean circulation |
title_full |
Surface buoyancy control of millennial-scale variations of the Atlantic meridional ocean circulation |
title_fullStr |
Surface buoyancy control of millennial-scale variations of the Atlantic meridional ocean circulation |
title_full_unstemmed |
Surface buoyancy control of millennial-scale variations of the Atlantic meridional ocean circulation |
title_sort |
surface buoyancy control of millennial-scale variations of the atlantic meridional ocean circulation |
publishDate |
2024 |
url |
https://doi.org/10.5194/egusphere-2024-819 https://egusphere.copernicus.org/preprints/2024/egusphere-2024-819/ |
genre |
Nordic Seas North Atlantic Sea ice |
genre_facet |
Nordic Seas North Atlantic Sea ice |
op_source |
eISSN: |
op_relation |
doi:10.5194/egusphere-2024-819 https://egusphere.copernicus.org/preprints/2024/egusphere-2024-819/ |
op_doi |
https://doi.org/10.5194/egusphere-2024-819 |
_version_ |
1802647110159433728 |