Comparing observed and modelled components of the Atlantic Meridional Overturning Circulation at 26°N
Comparing observed and modelled components of the Atlantic Meridional Overturning Circulation at 26°N
The Coupled Model Intercomparison Project (CMIP) allows assessment of the representation of the Atlantic Meridional Overturning Circulation (AMOC) in climate models. While CMIP Phase 6 models display a large spread in AMOC strength by a factor of three, the multi-model mean strength agrees reasonably well with observed estimates from RAPID1, but this does not hold for its various components. In CMIP6 the present-day AMOC is characterised by a lack of lower North Atlantic Deep Water (lNADW), due to the small-scale of Greenland-Iceland-Scotland Ridge overflow and too much mixing. This is compensated by increased recirculation in the subtropical gyre and more Antarctic Bottom Water (AABW). Deep-water circulation is dominated by a distinct deep western boundary current (DWBC) with minor interior recirculation compared to observations. The future decline in the AMOC to 2100 of 7Sv under a SSP5-8.5 scenario is associated with decreased northward western boundary current transport in combination with reduced southward flow of upper North Atlantic Deep Water (uNADW). In CMIP6, wind stress curl decreases with time by 14% so that the wind-driven thermocline recirculation in the subtropical gyre is reduced by 4 Sv (17%) by 2100. The reduction in western boundary current transport of 11Sv is more than the decrease in the wind-driven gyre transport suggesting a decrease over time in the component of the Gulf Stream originating in the South Atlantic.
ocean circulation, Atlantic Meridional Overturning Circulation (AMOC), Climate model projections
Bryden, Harry
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Drijfhout, Sybren
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Hazeleger, Wilco
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Mecking, Jennifer
9b090069-5061-4340-b736-9690894ce203
Bryden, Harry
7f823946-34e8-48a3-8bd4-a72d2d749184
Drijfhout, Sybren
a5c76079-179b-490c-93fe-fc0391aacf13
Hazeleger, Wilco
21d5b030-1127-424f-b22b-0a470dcb5b32
Mecking, Jennifer
9b090069-5061-4340-b736-9690894ce203
Bryden, Harry, Drijfhout, Sybren, Hazeleger, Wilco and Mecking, Jennifer
(2024)
Comparing observed and modelled components of the Atlantic Meridional Overturning Circulation at 26°N.
Ocean Science.
(In Press)
Abstract
The Coupled Model Intercomparison Project (CMIP) allows assessment of the representation of the Atlantic Meridional Overturning Circulation (AMOC) in climate models. While CMIP Phase 6 models display a large spread in AMOC strength by a factor of three, the multi-model mean strength agrees reasonably well with observed estimates from RAPID1, but this does not hold for its various components. In CMIP6 the present-day AMOC is characterised by a lack of lower North Atlantic Deep Water (lNADW), due to the small-scale of Greenland-Iceland-Scotland Ridge overflow and too much mixing. This is compensated by increased recirculation in the subtropical gyre and more Antarctic Bottom Water (AABW). Deep-water circulation is dominated by a distinct deep western boundary current (DWBC) with minor interior recirculation compared to observations. The future decline in the AMOC to 2100 of 7Sv under a SSP5-8.5 scenario is associated with decreased northward western boundary current transport in combination with reduced southward flow of upper North Atlantic Deep Water (uNADW). In CMIP6, wind stress curl decreases with time by 14% so that the wind-driven thermocline recirculation in the subtropical gyre is reduced by 4 Sv (17%) by 2100. The reduction in western boundary current transport of 11Sv is more than the decrease in the wind-driven gyre transport suggesting a decrease over time in the component of the Gulf Stream originating in the South Atlantic.
Text
finalBBDHM2Feb
- Accepted Manuscript
More information
Submitted date: November 2023
Accepted/In Press date: 29 February 2024
Keywords:
ocean circulation, Atlantic Meridional Overturning Circulation (AMOC), Climate model projections
Identifiers
Local EPrints ID: 484880
URI: http://eprints.soton.ac.uk/id/eprint/484880
ISSN: 1812-0792
PURE UUID: 56d208fb-09fc-4dd2-b239-504d4821851c
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Date deposited: 23 Nov 2023 18:18
Last modified: 10 Apr 2024 04:02
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Contributors
Author:
Wilco Hazeleger
Author:
Jennifer Mecking
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