Mechanisms of decadal variability in the Labrador Sea and the wider North Atlantic in a high-resolution climate model

Ortega, Pablo; Robson, Jon; Sutton, Rowan; Andrews, Martin B.

doi:10.1007/s00382-016-3467-y

Cited by 46 publications

(46 citation statements)

References 96 publications

(153 reference statements)

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“…Therefore, NCAR and GFDL-MOM025 appear to reveal the physics of the MOC upper limb, whereby a change in the subtropical overturning would impact the intensity of LSW formation via changes in heat transport to the subpolar gyre. Such a scenario is consistent with recent modeling studies (e.g., Robson et al 2012;Ortega et al 2017). In contrast, it appears that GISS and GFDL-MOM are revealing the physics of the MOC lower limb, whereby a change in LSW volume leads to a downstream MOC change.…”

Section: A Lsw Volumesupporting

confidence: 90%

Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

Lozier

Danabasoglu

et al. 2019

Journal of Climate

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While it has generally been understood that the production of Labrador Sea Water (LSW) impacts the Atlantic meridional overturning circulation (MOC), this relationship has not been explored extensively or validated against observations. To explore this relationship, a suite of global ocean–sea ice models forced by the same interannually varying atmospheric dataset, varying in resolution from non-eddy-permitting to eddy-permitting (1°–1/4°), is analyzed to investigate the local and downstream relationships between LSW formation and the MOC on interannual to decadal time scales. While all models display a strong relationship between changes in the LSW volume and the MOC in the Labrador Sea, this relationship degrades considerably downstream of the Labrador Sea. In particular, there is no consistent pattern among the models in the North Atlantic subtropical basin over interannual to decadal time scales. Furthermore, the strong response of the MOC in the Labrador Sea to LSW volume changes in that basin may be biased by the overproduction of LSW in many models compared to observations. This analysis shows that changes in LSW volume in the Labrador Sea cannot be clearly and consistently linked to a coherent MOC response across latitudes over interannual to decadal time scales in ocean hindcast simulations of the last half century. Similarly, no coherent relationships are identified between the MOC and the Labrador Sea mixed layer depth or the density of newly formed LSW across latitudes or across models over interannual to decadal time scales.

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Section: A Lsw Volumesupporting

confidence: 90%

Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

Lozier

Danabasoglu

et al. 2019

Journal of Climate

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“…In Figure , middle column shows time series of the Labrador Sea MLD. The Labrador Sea has been shown to be an important region for forming deep water and influencing the AMOC in this model (Ortega et al, ).…”

Section: Resultsmentioning

confidence: 98%

Hysteresis and Resilience of the AMOC in an Eddy‐Permitting GCM

Jackson

Wood

2018

Geophysical Research Letters

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We show a quasi‐irreversible shutdown (hysteresis) of the Atlantic meridional overturning circulation (AMOC) in an unfluxadjusted global climate model with an eddy‐permitting ocean. This global climate model is a prototype of one submitted to the sixth Coupled Model Intercomparison Project and is the most comprehensive model to show this behavior. The AMOC has a resilience timescale for a given hosing: If the hosing exceeds the critical hosing for collapse for only a limited time, the AMOC recovers when the hosing is stopped. Beyond the critical time, when the hosing stops the AMOC stays in a weak state with no recovery within 200 years. We show that simple, observable metrics such as AMOC strength and mixed layer depth can indicate whether this critical resilience time has passed and that the mechanism controlling the presence of recovery is a positive advective feedback.

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“…We use 120 years of monthly mean data from a preindustrial control experiment of the HadGEM3-GC2 model (GC2 for short), which was analyzed in Ortega et al (2017). GC2 is a coupled atmosphere-ocean-sea ice configuration of the UK Met Office climate model (Williams et al, 2015).…”

Section: Model Datamentioning

confidence: 99%

How Robust Are the Surface Temperature Fingerprints of the Atlantic Overturning Meridional Circulation on Monthly Time Scales?

Alexander‐Turner

Ortega

Robson

2018

Geophysical Research Letters

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It has been suggested that changes in the Atlantic Meridional Overturning Circulation (AMOC) can drive sea surface temperature (SST) on monthly time scales (Duchez et al., 2016, https://doi.org/10.1007/s00382-015-2918-1). However, with only 11 years of continuous observations, the validity of this result over longer, or different, time periods is uncertain. In this study, we use a 120 yearlong control simulation from a high‐resolution climate model to test the robustness of the AMOC fingerprints. The model reproduces the observed AMOC seasonal cycle and its variability, and the observed 5‐month lagged AMOC‐SST fingerprints derived from 11 years of data. However, the AMOC‐SST fingerprints are very sensitive to the particular time period considered. In particular, both the Florida current and the upper mid‐ocean transport produce highly inconsistent fingerprints when using time periods shorter than 30 years. Therefore, several decades of RAPID observations will be necessary to determine the real impact of the AMOC on SSTs at monthly time scales.

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Mechanisms of decadal variability in the Labrador Sea and the wider North Atlantic in a high-resolution climate model

Abstract: trends in Labrador Sea densities are followed by important atmospheric impacts. In particular, a positive winter NAO response appears to follow the negative Labrador Sea density trends, and provides a phase reversal mechanism.

Cited by 46 publications

References 96 publications

Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

Hysteresis and Resilience of the AMOC in an Eddy‐Permitting GCM

How Robust Are the Surface Temperature Fingerprints of the Atlantic Overturning Meridional Circulation on Monthly Time Scales?

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