Model-based evidence of deep-ocean heat uptake during surface-temperature hiatus periods

2011 ◽  
Vol 1 (7) ◽  
pp. 360-364 ◽  
Author(s):  
Gerald A. Meehl ◽  
Julie M. Arblaster ◽  
John T. Fasullo ◽  
Aixue Hu ◽  
Kevin E. Trenberth
Keyword(s):  
Surface Temperature ◽  
Deep Ocean ◽  
Ocean Heat Uptake ◽  
Model Based ◽  
Heat Uptake

scholarly journals Transient Climate Response in a Two-Layer Energy-Balance Model. Part II: Representation of the Efficacy of Deep-Ocean Heat Uptake and Validation for CMIP5 AOGCMs

2013 ◽  
Vol 26 (6) ◽  
pp. 1859-1876 ◽  
Author(s):  
O. Geoffroy ◽  
D. Saint-Martin ◽  
G. Bellon ◽  
A. Voldoire ◽  
D. J. L. Olivié ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Energy Balance ◽  
Surface Temperature ◽  
General Circulation ◽  
Deep Ocean ◽  
Energy Balance Model ◽  
Balance Model ◽  
Ocean Heat Uptake ◽  
Transient Climate Response ◽  
Heat Uptake

Abstract In this second part of a series of two articles analyzing the global thermal properties of atmosphere–ocean coupled general circulation models (AOGCMs) within the framework of a two-layer energy-balance model (EBM), the role of the efficacy of deep-ocean heat uptake is investigated. Taking into account such an efficacy factor is shown to amount to representing the effect of deep-ocean heat uptake on the local strength of the radiative feedback in the transient regime. It involves an additional term in the formulation of the radiative imbalance at the top of the atmosphere (TOA), which explains the nonlinearity between radiative imbalance and the mean surface temperature observed in some AOGCMs. An analytical solution of this system is given and this simple linear EBM is calibrated for the set of 16 AOGCMs of phase 5 of the Coupled Model Intercomparison Project (CMIP5) studied in Part I. It is shown that both the net radiative fluxes at TOA and the global surface temperature transient response are well represented by the simple EBM over the available period of simulations. Differences between this two-layer EBM and the previous version without an efficacy factor are analyzed and relationships between parameters are discussed. The simple model calibration applied to AOGCMs constitutes a new method for estimating their respective equilibrium climate sensitivity and adjusted radiative forcing amplitude from short-term step-forcing simulations and more generally a method to compute their global thermal properties.

scholarly journals The magnitudes and timescales of global mean surface temperature feedbacks in climate models

2011 ◽  
Vol 2 (2) ◽  
pp. 213-221 ◽  
Author(s):  
A. Jarvis
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Climate Models ◽  
Systems Approach ◽  
Deep Ocean ◽  
Ocean Heat Uptake ◽  
Positive Feedbacks ◽  
Heat Uptake ◽  
Global Mean Surface Temperature ◽  
Global Mean

Abstract. Because of the fundamental role feedbacks play in determining the response of surface temperature to perturbations in radiative forcing, it is important we understand the dynamic characteristics of these feedbacks. Rather than attribute the aggregate surface temperature feedback to particular physical processes, this paper adopts a linear systems approach to investigate the partitioning with respect to the timescale of the feedbacks regulating global mean surface temperature in climate models. The analysis reveals that there is a dominant net negative feedback realised on an annual timescale and that this is partially attenuated by a spectrum of positive feedbacks with characteristic timescales in the range 10 to 1000 yr. This attenuation was composed of two discrete phases which are attributed to the equilibration of "diffusive – mixed layer" and "circulatory – deep ocean" ocean heat uptake. The diffusive equilibration was associated with time constants on the decadal timescale and accounted for approximately 75 to 80 percent of the overall ocean heat feedback, whilst the circulatory equilibration operated on a centennial timescale and accounted for the remaining 20 to 25 percent of the response. This suggests that the dynamics of the transient ocean heat uptake feedback first discussed by Baker and Roe (2009) tends to be dominated by loss of diffusive heat uptake in climate models, rather than circulatory deep ocean heat equilibration.

scholarly journals Estimating the Effect of Radiative Feedback Uncertainties on Climate Response to Changes in the Concentration of Stratospheric Aerosols

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 654
Author(s):  
Sergei Soldatenko
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Deep Ocean ◽  
Climate System ◽  
Ocean Heat Uptake ◽  
Heat Uptake ◽  
Global Mean Surface Temperature ◽  
Radiative Feedbacks ◽  
Global Mean ◽  
System Inertia

Using the two-box energy balance model (EBM), we explore the climate system response to radiative forcing generated by variations in the concentrations of stratospheric aerosols and estimate the effect of uncertainties in radiative feedbacks on changes in global mean surface temperature anomaly used as an indicator of the response of the climate system to external radiative perturbations. Radiative forcing generated by stratospheric sulfate aerosols from the second-largest volcanic eruption in the 20th century, the Mount Pinatubo eruption in June 1991, was chosen for this research. The global mean surface temperature response to a specified change in radiative forcing is estimated as a convolution of the derived impulse response function corresponding to EBM with a function that describes the temporal change in radiative forcing. The influence of radiative feedback uncertainties on changes in the global mean surface temperature is estimated using several “versions” of the EBM. The parameters for different “versions” were identified by applying a specific procedure for calibrating the two-box EBM parameters using the results of climate change simulations conducted with coupled atmosphere–ocean general circulation models from the Coupled Model Intercomparison Project phase 5 (CMIP5). Changes in the global mean surface temperature caused by stratospheric aerosol forcing are found to be highly sensitive not only to radiative feedbacks but also to climate system inertia defined by the effective heat capacity of the atmosphere–land–ocean mixed layer system, as well as to deep-ocean heat uptake. The results obtained have direct implications for a better understanding of how uncertainties in climate feedbacks, climate system inertia and deep-ocean heat uptake affect climate change modelling.

Sensitivity of the Ocean’s Climate to Diapycnal Diffusivity in an EMIC. Part II: Global Warming Scenario

2005 ◽  
Vol 18 (13) ◽  
pp. 2482-2496 ◽  
Author(s):  
Fabio Dalan ◽  
Peter H. Stone ◽  
Andrei P. Sokolov
Keyword(s):  
Global Warming ◽  
Thermohaline Circulation ◽  
Deep Ocean ◽  
Diffusive Flux ◽  
Ocean Heat Uptake ◽  
Advective Flux ◽  
Warming Scenario ◽  
Heat Uptake ◽  
Global Warming Scenario ◽  
Diapycnal Diffusivity

Abstract The sensitivity of the ocean’s climate to the diapycnal diffusivity in the ocean is studied for a global warming scenario in which CO2 increases by 1% yr−1 for 75 yr. The thermohaline circulation slows down for about 100 yr and recovers afterward, for any value of the diapycnal diffusivity. The rates of slowdown and of recovery, as well as the percentage recovery of the circulation at the end of 1000-yr integrations, are variable, but a direct relation with the diapycnal diffusivity cannot be found. At year 70 (when CO2 has doubled) an increase of the diapycnal diffusivity from 0.1 to 1.0 cm2 s−1 leads to a decrease in surface air temperature of about 0.4 K and an increase in sea level rise of about 4 cm. The steric height gradient is divided into thermal component and haline component. It appears that, in the first 60 yr of simulated global warming, temperature variations dominate the salinity ones in weakly diffusive models, whereas the opposite occurs in strongly diffusive models. The analysis of the vertical heat balance reveals that deep-ocean heat uptake is due to reduced upward isopycnal diffusive flux and parameterized-eddy advective flux. Surface warming, induced by enhanced CO2 in the atmosphere, leads to a reduction of the isopycnal slope, which translates into a reduction of the above fluxes. The amount of reduction is directly related to the magnitude of the isopycnal diffusive flux and parameterized-eddy advective flux at equilibrium. These latter fluxes depend on the thickness of the thermocline at equilibrium and hence on the diapycnal diffusion. Thus, the increase of deep-ocean heat uptake with diapycnal diffusivity is an indirect effect that the latter parameter has on the isopycnal diffusion and parameterized-eddy advection.

Deep-ocean heat uptake and equilibrium climate response

2012 ◽  
Vol 40 (5-6) ◽  
pp. 1071-1086 ◽  
Author(s):  
Chao Li ◽  
Jin-Song von Storch ◽  
Jochem Marotzke
Keyword(s):  
Deep Ocean ◽  
Climate Response ◽  
Ocean Heat Uptake ◽  
Heat Uptake ◽  
Equilibrium Climate Response

scholarly journals The Deep-Ocean Heat Uptake in Transient Climate Change

2003 ◽  
Vol 16 (9) ◽  
pp. 1352-1363 ◽  
Author(s):  
Boyin Huang ◽  
Peter H. Stone ◽  
Andrei P. Sokolov ◽  
Igor V. Kamenkovich
Keyword(s):  
Heat Flux ◽  
Global Warming ◽  
Surface Heat Flux ◽  
Coupled Model ◽  
Deep Ocean ◽  
Surface Heat ◽  
Ocean Heat Uptake ◽  
Warming Scenario ◽  
Heat Uptake ◽  
Global Warming Scenario

Abstract The deep-ocean heat uptake (DOHU) in transient climate changes is studied using an ocean general circulation model (OGCM) and its adjoint. The model configuration consists of idealized Pacific and Atlantic basins. The model is forced with the anomalies of surface heat and freshwater fluxes from a global warming scenario with a coupled model using the same ocean configuration. In the global warming scenario, CO2 concentration increases 1% yr−1. The heat uptake calculated from the coupled model and from the adjoint are virtually identical, showing that the heat uptake by the OGCM is a linear process. After 70 yr the ocean heat uptake is almost evenly distributed within the layers above 200 m, between 200 and 700 m, and below 700 m (about 20 × 1022 J in each). The effect of anomalous surface freshwater flux on the DOHU is negligible. Analysis of the Coupled Model Intercomparison Project (CMIP-2) data for the same global warming scenario shows that qualitatively similar results apply to coupled atmosphere–ocean GCMs. The penetration of surface heat flux to the deep ocean in the OGCM occurs mainly in the North Atlantic and the Southern Ocean, since both the sensitivity of DOHU to the surface heat flux and the magnitude of anomalous surface heat flux are large in these two regions. The DOHU relies on the reduction of convection and Gent–McWilliams–Redi mixing in the North Atlantic, and the reduction of Gent–McWilliams–Redi mixing in the Southern Ocean.

On the suitability of two-layer energy-balance models for representing deep ocean heat uptake

2020 ◽  
Author(s):  
Peter Shatwell ◽  
Arnaud Czaja ◽  
David Ferreira
Keyword(s):  
Heat Exchange ◽  
Energy Balance ◽  
Mixed Layer ◽  
Deep Ocean ◽  
Heat Energy ◽  
Ocean Heat Uptake ◽  
Heat Uptake ◽  
Vertical Heat ◽  
Energy Balance Models ◽  
Small Basin

<p>Over 90% of the excess heat energy due to global warming is taken up by the oceans. Because of this, ocean heat uptake and planetary heat uptake can be considered equivalent. This heat energy is readily taken up by the oceanic mixed-layer on decadal timescales and subsequently transferred to the thermocline and deep ocean below on longer, centennial timescales by different ventilation mechanisms. The ventilation rate is affected by many things including the mixed-layer depth, the strength of the overturning, and mode-water formation. In current two-layer energy-balance models (EBMs), all ventilation mechanisms are reduced and parameterised by a simple linear vertical heat-exchange term that depends on the temperature difference between the upper and lower layers (representing the mixed-layer and deep ocean, respectively). </p><p>Two-layer EBMs have been used successfully to reproduce the global mean surface temperature responses for CMIP5 models in abrupt CO<sub>2</sub>-quadrupling experiments. Little attention has been paid to the EBM-predicted deep ocean response, however. We perform an abrupt CO<sub>2</sub>-doubling experiment using an idealised aquaplanet model with a simple geometry that splits the ocean into small, large, and southern ocean basins. By fitting a two-layer EBM regionally to each basin's deep temperature response, we find that it provides a good fit only for the small basin. We suggest this is due to the small basin exhibiting a deep overturning circulation — not seen in the other model basins — which connects the ocean surface to its interior; only this ventilation mechanism can be successfully parameterised by a linear vertical heat-exchange. By considering the wind-driven circulation theory of Rhines and Young, we suggest a new parameterisation for the two-layer EBM deep ocean heat uptake that may be more suitable for basins without deep overturning.</p>

Combining Modern and Paleoceanographic Perspectives on Ocean Heat Uptake

2021 ◽  
Vol 13 (1) ◽  
pp. 255-281
Author(s):  
Geoffrey Gebbie
Keyword(s):  
Heat Content ◽  
Deep Ocean ◽  
First Century ◽  
Ocean Heat Uptake ◽  
Heat Uptake ◽  
Wide Perspective ◽  
The Common ◽  
Common Era ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Monitoring Earth's energy imbalance requires monitoring changes in the heat content of the ocean. Recent observational estimates indicate that ocean heat uptake is accelerating in the twenty-first century. Examination of estimates of ocean heat uptake over the industrial era, the Common Era of the last 2,000 years, and the period since the Last Glacial Maximum, 20,000 years ago, permits a wide perspective on modern-day warming rates. In addition, this longer-term focus illustrates how the dynamics of the deep ocean and the cryosphere were active in the past and are still active today. The large climatic shifts that started with the melting of the great ice sheets have involved significant ocean heat uptake that was sustained over centuries and millennia, and modern-ocean heat content changes are small by comparison.

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