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Simulations of hydrographic properties in the northwestern North Atlantic Ocean in coupled climate models

Simulations of hydrographic properties in the northwestern North Atlantic Ocean in coupled climate models
Simulations of hydrographic properties in the northwestern North Atlantic Ocean in coupled climate models
The performance of coupled climate models (CCMs) in simulating the hydrographic structure and variability of the northwestern North Atlantic Ocean, in particular the Labrador and Irminger Seas, has been assessed. This area plays an important role in the meridional overturning circulation. Hydrographic properties of the preindustrial run of eight CCMs used in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) are compared with observations from the World Ocean Circulation Experiment Repeat section 7 (WOCE AR7). The mean and standard deviation of 20 yr of simulated data are compared in three layers, representing the surface waters, intermediate waters, and deep waters. Two models simulate an extremely cold, fresh surface layer with model biases down to ?1.7 psu and ?4.0°C, much larger than the observed ranges of variability. The intermediate and deep layers are generally too warm and saline, with biases up to 0.7 psu and 2.8°C. An analysis of the maximum mixed layer depth shows that the low surface salinity is related to a convective regime restricted to the upper 500 dbar. Thus, intermediate water formed by convection is partly replaced by warmer water from the south. Model biases seem to be caused by the coupling to the atmospheric component of the CCM. Model drift during long spinup periods allows the initially small biases in water mass characteristics to become significant. Biases that develop in the control run are carried over to the twentieth-century runs, which are initialized from the control runs.
coupled models, north atlantic ocean, climate models
0894-8755
1767-1786
de Jong, M.F.
71f6fc2c-21c9-484a-bf2e-4f2761a4b673
Drijfhout, S.S.
a5c76079-179b-490c-93fe-fc0391aacf13
Hazeleger, W.
0bd826a1-4713-43ab-aace-3ea59d2fc37e
van Aken, H.M.
2666f480-9f72-47ec-bbd9-794bce05d7c2
Severijns, C.A.
2a80ef9d-9281-4ac7-87b7-c4419bb5d5be
de Jong, M.F.
71f6fc2c-21c9-484a-bf2e-4f2761a4b673
Drijfhout, S.S.
a5c76079-179b-490c-93fe-fc0391aacf13
Hazeleger, W.
0bd826a1-4713-43ab-aace-3ea59d2fc37e
van Aken, H.M.
2666f480-9f72-47ec-bbd9-794bce05d7c2
Severijns, C.A.
2a80ef9d-9281-4ac7-87b7-c4419bb5d5be

de Jong, M.F., Drijfhout, S.S., Hazeleger, W., van Aken, H.M. and Severijns, C.A. (2009) Simulations of hydrographic properties in the northwestern North Atlantic Ocean in coupled climate models. Journal of Climate, 22 (7), 1767-1786. (doi:10.1175/2008JCLI2448.1).

Record type: Article

Abstract

The performance of coupled climate models (CCMs) in simulating the hydrographic structure and variability of the northwestern North Atlantic Ocean, in particular the Labrador and Irminger Seas, has been assessed. This area plays an important role in the meridional overturning circulation. Hydrographic properties of the preindustrial run of eight CCMs used in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) are compared with observations from the World Ocean Circulation Experiment Repeat section 7 (WOCE AR7). The mean and standard deviation of 20 yr of simulated data are compared in three layers, representing the surface waters, intermediate waters, and deep waters. Two models simulate an extremely cold, fresh surface layer with model biases down to ?1.7 psu and ?4.0°C, much larger than the observed ranges of variability. The intermediate and deep layers are generally too warm and saline, with biases up to 0.7 psu and 2.8°C. An analysis of the maximum mixed layer depth shows that the low surface salinity is related to a convective regime restricted to the upper 500 dbar. Thus, intermediate water formed by convection is partly replaced by warmer water from the south. Model biases seem to be caused by the coupling to the atmospheric component of the CCM. Model drift during long spinup periods allows the initially small biases in water mass characteristics to become significant. Biases that develop in the control run are carried over to the twentieth-century runs, which are initialized from the control runs.

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More information

Published date: April 2009
Keywords: coupled models, north atlantic ocean, climate models
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 348364
URI: http://eprints.soton.ac.uk/id/eprint/348364
ISSN: 0894-8755
PURE UUID: f2363a5e-1295-45ad-95c5-fd8f01655e67

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Date deposited: 12 Feb 2013 13:16
Last modified: 08 Jan 2022 12:02

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Contributors

Author: M.F. de Jong
Author: S.S. Drijfhout
Author: W. Hazeleger
Author: H.M. van Aken
Author: C.A. Severijns

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