A Reexamination of the polar Halocline Catastrophe and Implications for Coupled Ocean-Atmosphere Modeling

Zhang, Sheng; Greatbatch, Richard John; Lin, Charles A.

doi:10.1175/1520-0485(1993)023<0287:arotph>2.0.co;2

Cited by 109 publications

(106 citation statements)

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“…Near the southern sinking region at 557 S, where albedo remains almost constant, this can only be achieved when the atmospheric temperature increases, thus increasing the long-wave radiation and at the same time reducing the surface heat flux. This last result confirms the findings of Zhang et al (1993) that the anomalous surface heat fluxes are fundamentally different between mixed boundary conditions and their atmospheric model. Here an increase in atmospheric temperature of 0.33 K accompanies the rise in local SST by 0.97 K. Taking the zonal mean and the mean over the 107 meridional extent of computational box of the atmospheric model we find even smaller airsea differences and an anomalous surface heat flux of only 0.2 W m P2 .…”

Section: Resultssupporting

confidence: 89%

“…An atmosphere without anomalous transports of its own makes the coupled system less sensitive compared to mixed boundary conditions. This result is similar to findings by Zhang et al (1993) and Mikolajewicz and Maier-Reimer (1994). Zhang et al (1993) couple a zero heat capacity model without anomalous horizontal transports to an ocean GCM.…”

Section: Discussionsupporting

confidence: 89%

“…Also the surface fresh water, flux is kept fixed. A similar system has been considered by Zhang et al (1993) who used Schopf's (1983) atmospheric model. Because the atmospheric temperature can react to changes in SST, this configuration contains both the oceanic salt and heat transport feedbacks.…”

Section: Methodsmentioning

confidence: 99%

“…Relatively minor perturbations in the fresh water flux can lead to dramatic changes in poleward heat and salt transport, or even a breakdown of the oceanic thermohaline circulation (termed "polar halocline catastrophe" by Bryan 1986). Recent model studies (Zhang et al 1993;Rahmstorf 1995;Rahmstorf and Willebrand 1995;Lohmann et al 1996) suggest that the sensitivity under these mixed boundary conditions is overestimated. Also, recent and paleo-oceanographic evidence shows that the sensitivity of the climate system is much smaller.…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity of the thermohaline circulation in coupled oceanic GCM - atmospheric EBM experiments

Lohmann

Gerdes

Chen³

1996

Climate Dynamics

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Abstract. We analyze the sensitivity of the oceanic thermohaline circulation (THC) regarding perturbations in fresh water flux for a range of coupled oceanic general circulation -atmospheric energy balance models. The energy balance model (EBM) predicts surface air temperature and fresh water flux and contains the feedbacks due to meridional transports of sensible and latent heat. In the coupled system we examine a negative perturbation in run-off into the southern ocean and analyze the role of changed atmospheric heat transports and fresh water flux. With mixed boundary conditions (fixed air temperature and fixed surface fresh water fluxes) the response is characterized by a completely different oceanic heat transport than in the reference case. On the other hand, the surface heat flux remains roughly constant when the air temperature can adjust in a model where no anomalous atmospheric transports are allowed. This gives an artificially stable system with nearly unchanged oceanic heat transport. However, if meridional heat transports in the atmosphere are included, the sensitivity of the system lies between the two extreme cases. We find that changes in fresh water flux are unimportant for the THC in the coupled system.

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Section: Resultssupporting

confidence: 89%

Section: Discussionsupporting

confidence: 89%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sensitivity of the thermohaline circulation in coupled oceanic GCM - atmospheric EBM experiments

Lohmann

Gerdes

Chen³

1996

Climate Dynamics

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“…There is clearly an increase in stability as the value of τ T increases (in good agreement with the results of Zhang et al, 1993). However, in contrast with the conclusions of Tziperman et al (1994), there is no general increase in stability with τ S .…”

Section: Resultssupporting

confidence: 85%

The stability of a zonally averaged thermohaline circulation model

Schmidt¹,

Mysak²

1996

Tellus A

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A combination of analytical and numerical techniques are used to efficiently determine the qualitative and quantitative behaviour of a one-basin zonally averaged thermohaline circulation ocean model under various forcing regimes and over a large region of parameter space. In contrast to earlier studies which use time stepping to find the steady solutions, the steady state equations are first solved directly to obtain the multiple equilibria under identical mixed boundary conditions. This approach is based on the differentiability of the governing equations and especially the convection scheme. A linear stability analysis is then performed, in which the normal modes and corresponding eigenvalues are found for the various equilibrium states. Resonant periodic solutions superimposed on these states are predicted for various types of forcing.The results are used to gain insight into the solutions obtained by Mysak, Stocker and Huang in a previous numerical study in which the eddy diffusivities were varied in a randomly forced one-basin zonally averaged model. It is shown that the twocell symmetric circulation is generally unstable to anti-symmetric perturbations in the temperature or salinity (as expected), and that both one-cell (inter-hemispheric) circulation patterns are generally stable. Resonant stable oscillations with century scale periods are predicted with structures that compare favorably with those found in the previous study. In cases with large horizontal diffusivities, the two-cell pattern is also stable, which parallels cases in the previous study where large vacillations were seen between the three stable steady states. Further, in cases with large horizontal and large vertical diffusivities, no one-cell pattern can be realised and the only asymptotic behaviour found is the two-cell pattern.An experiment is also performed to examine the effect of varying the restoring time constants in the relaxation boundary conditions used at the surface for both salinity and temperature.2

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The impact of sea surface temperature bias on equatorial Atlantic interannual variability in partially coupled model experiments

Ding

Greatbatch

Latif

et al. 2015

Geophysical Research Letters

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We examine the impact of sea surface temperature (SST) bias on interannual variability during boreal summer over the equatorial Atlantic using two suites of partially coupled model (PCM) experiments with and without surface heat flux correction. In the experiments, surface wind stress anomalies are specified from observations while the thermodynamic coupling between the atmospheric and oceanic components is still active as in the fully coupled model. The results show that the PCM can capture around 50% of the observed variability associated with the Atlantic Niño from 1958 to 2013, but only when the bias is substantially reduced using heat flux correction, with no skill otherwise. We further show that ocean dynamics explain a large part of the SST variability in the eastern equatorial Atlantic in both observations (50–60%) and the PCM experiments (50–70%) with heat flux correction, implying that the seasonal predictability potential may be higher than currently thought.

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A Reexamination of the polar Halocline Catastrophe and Implications for Coupled Ocean-Atmosphere Modeling

Cited by 109 publications

References 0 publications

Sensitivity of the thermohaline circulation in coupled oceanic GCM - atmospheric EBM experiments

Sensitivity of the thermohaline circulation in coupled oceanic GCM - atmospheric EBM experiments

The stability of a zonally averaged thermohaline circulation model

The impact of sea surface temperature bias on equatorial Atlantic interannual variability in partially coupled model experiments

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