scholarly journals Bjerknes Compensation in Meridional Heat Transport under Freshwater Forcing and the Role of Climate Feedback

2017 ◽  
Vol 30 (14) ◽  
pp. 5167-5185 ◽  
Author(s):  
Haijun Yang ◽  
Qin Wen ◽  
Jie Yao ◽  
Yuxing Wang
Keyword(s):  
Energy Balance ◽  
Heat Transport ◽  
Meridional Overturning Circulation ◽  
Hadley Cell ◽  
Climate Feedback ◽  
Local Energy ◽  
Surface Temperature Change ◽  
Local Climate ◽  
Freshwater Forcing ◽  
The Tropics

Using a coupled Earth climate model, freshwater forcing experiments are performed to study the Bjerknes compensation (BJC) between meridional atmosphere heat transport (AHT) and meridional ocean heat transport (OHT). Freshwater hosing in the North Atlantic weakens the Atlantic meridional overturning circulation (AMOC) and thus reduces the northward OHT in the Atlantic significantly, leading to a cooling (warming) in the surface layer in the Northern (Southern) Hemisphere. This results in an enhanced Hadley cell and northward AHT. Meanwhile, the OHT in the Indo-Pacific is increased in response to the Hadley cell change, partially offsetting the reduced OHT in the Atlantic. Two compensations occur here: compensation between the AHT and the Atlantic OHT, and that between the Indo-Pacific OHT and the Atlantic OHT. The AHT change undercompensates the OHT change by about 60% in the extratropics, while the former overcompensates the latter by about 30% in the tropics due to the Indo-Pacific change. The BJC can be understood from the viewpoint of large-scale circulation change. However, the intrinsic mechanism of BJC is related to the climate feedback of the Earth system. The authors’ coupled model experiments confirm that the occurrence of BJC is an intrinsic requirement of local energy balance, and local climate feedback determines the extent of BJC, consistent with previous theoretical results. Even during the transient period of climate change, the BJC is well established when the ocean heat storage is slowly varying and its change is much weaker than the net local heat flux change at the ocean surface. The BJC can be deduced from the local climate feedback. Under the freshwater forcing, the overcompensation in the tropics is mainly caused by the positive longwave feedback related to clouds, and the undercompensation in the extratropics is due to the negative longwave feedback related to surface temperature change. Different dominant feedbacks determine different BJC scenarios in different regions, which are in essence constrained by local energy balance.

scholarly journals Climate feedbacks induced by the North Atlantic freshwater forcing in a coupled model of intermediate complexity

2010 ◽  
Vol 25 (1) ◽  
pp. 103-113 ◽  
Author(s):  
Flávio Barbosa Justino ◽  
Jeferson Prietsch Machado
Keyword(s):  
Heat Transport ◽  
North Atlantic ◽  
Thermohaline Circulation ◽  
Coupled Model ◽  
The North ◽  
Poleward Heat Transport ◽  
Freshwater Forcing ◽  
Oceanic Response ◽  
The North Atlantic ◽  
The Tropics

Based on coupled model simulations (ECBilt-Clio), we investigate the atmospheric and oceanic response to sustained freshwater input into the North Atlantic under the glacial maximum background state. The results demonstrate that a weakening of the thermohaline circulation triggered by weaker density flux leads to rapid changes in global sea-ice volume and reduced poleward heat transport in the Northern Hemisphere (NH). In the Southern Hemisphere (SH), however, the oceanic heat transport increases substantially. This in turn leads to strong cooling over the North Atlantic whereas the SH extratropical region warms up. The suppression of the NADW also drastically changes the atmospheric circulation. The associated northward wind anomalies over the North Atlantic increase the warm air advection from the tropics and induce the transport of tropical saltier water to mid-latitudes. This negative atmospheric-oceanic feedback should play an important role to resume the NADW, after the freshwater forcing ends up.

scholarly journals Coupled High-Latitude Climate Feedbacks and Their Impact on Atmospheric Heat Transport

2017 ◽  
Vol 30 (1) ◽  
pp. 189-201 ◽  
Author(s):  
Nicole Feldl ◽  
Simona Bordoni ◽  
Timothy M. Merlis
Keyword(s):  
Heat Transport ◽  
High Latitude ◽  
Surface Albedo ◽  
Hadley Cell ◽  
Lapse Rate ◽  
The Arctic ◽  
Albedo Feedback ◽  
Atmospheric Heat Transport ◽  
The Tropics ◽  
Atmospheric Heat

The response of atmospheric heat transport to anthropogenic warming is determined by the anomalous meridional energy gradient. Feedback analysis offers a characterization of that gradient and hence reveals how uncertainty in physical processes may translate into uncertainty in the circulation response. However, individual feedbacks do not act in isolation. Anomalies associated with one feedback may be compensated by another, as is the case for the positive water vapor and negative lapse rate feedbacks in the tropics. Here a set of idealized experiments are performed in an aquaplanet model to evaluate the coupling between the surface albedo feedback and other feedbacks, including the impact on atmospheric heat transport. In the tropics, the dynamical response manifests as changes in the intensity and structure of the overturning Hadley circulation. Only half of the range of Hadley cell weakening exhibited in these experiments is found to be attributable to imposed, systematic variations in the surface albedo feedback. Changes in extratropical clouds that accompany the albedo changes explain the remaining spread. The feedback-driven circulation changes are compensated by eddy energy flux changes, which reduce the overall spread among experiments. These findings have implications for the efficiency with which the climate system, including tropical circulation and the hydrological cycle, adjusts to high-latitude feedbacks over climate states that range from perennial or seasonal ice to ice-free conditions in the Arctic.

The Response of Large-Scale Circulation to Obliquity-Induced Changes in Meridional Heating Gradients

2014 ◽  
Vol 27 (14) ◽  
pp. 5504-5516 ◽  
Author(s):  
Damianos F. Mantsis ◽  
Benjamin R. Lintner ◽  
Anthony J. Broccoli ◽  
Michael P. Erb ◽  
Amy C. Clement ◽  
...  
Keyword(s):  
Heat Transport ◽  
Large Scale ◽  
Climate Model ◽  
Hadley Circulation ◽  
Heat Fluxes ◽  
Meridional Overturning Circulation ◽  
Hadley Cell ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Summer Hemisphere ◽  
Insolation Change

Abstract The inter- and intrahemispheric climate responses to a change in obliquity are investigated using the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1. (GFDL CM2.1). Reduced obliquity causes a weakening of the seasonal insolation contrast between the summer and winter hemispheres and a strengthening of the meridional insolation gradient within the summer hemisphere. The interhemispheric insolation change is associated with weakening of the cross-equatorial Hadley circulation and reduced heat transport from the summer hemisphere to the winter hemisphere, in both the ocean and atmosphere. In contrast, the intrahemispheric insolation change is associated with increased midlatitude summer eddy activity as seen by the increased atmospheric heat transport at those latitudes. Analysis of the zonal mean atmospheric meridional overturning circulation on isentropic surfaces confirms the increase of the midlatitude eddy circulation, which is driven by changes of sensible and latent heat fluxes, as well as changes in the stratification or distribution of entropy. It is suggested that the strengthening of this circulation is associated with an equatorward shift of the ascending branch of the winter Hadley cell.

scholarly journals A Generalized Energy Balance Climate Model with Parameterized Dynamics and Diabatic Heating

2005 ◽  
Vol 18 (11) ◽  
pp. 1753-1772 ◽  
Author(s):  
Karen M. Shell ◽  
Richard C. J. Somerville
Keyword(s):  
Energy Balance ◽  
Heat Transport ◽  
Ocean Circulation ◽  
Heat Budget ◽  
Hadley Cell ◽  
Lapse Rate ◽  
Meridional Heat Transport ◽  
Temperature Changes ◽  
Global Average ◽  
Average Temperature

Abstract Energy balance models have proven useful in understanding mechanisms and feedbacks in the climate system. An original global energy balance model is presented here. The model is solved numerically for equilibrium climate states defined by zonal average temperature as a function of latitude for both a surface and an atmospheric layer. The effects of radiative, latent, and sensible heating are parameterized. The model includes a variable lapse rate and parameterizations of the major dynamical mechanisms responsible for meridional heat transport: the Hadley cell, midlatitude baroclinic eddies, and ocean circulation. The model reproduces both the mean variation of temperature with latitude and the global average heat budget within the uncertainty of observations. The utility of the model is demonstrated through examination of various climate feedbacks. One important feedback is the effect of the lapse rate on climate. When the planet warms as a result of an increase in the solar constant, the lapse rate acts as a negative feedback, effectively enhancing the longwave emission efficiency of the atmosphere. The lapse rate is also responsible for an increase in global average temperature when the meridional heat transport effectiveness is increased. The water vapor feedback enhances temperature changes, while the latent and sensible heating feedback reduces surface temperature changes.

Revisiting the variation of the climate feedback parameter

2021 ◽  
Author(s):  
Diego Jiménez-de-la-Cuesta
Keyword(s):  
Energy Balance ◽  
Explicit Expression ◽  
Climate Feedback ◽  
Additional Contribution ◽  
Earth System ◽  
Surface Temperature Change ◽  
Feedback Parameter ◽  
The Earth ◽  
Ocean Atmosphere ◽  
Spatio Temporal

<p>Observations and models indicate a varying radiative response of the Earth system to CO<sub>2</sub> forcing. This variation introduces large uncertainties in the climate sensitivity estimates to increasing atmospheric CO<sub>2</sub> concentration. This variation is represented as an additional feedback mechanism in energy-balance models, which depends on more than only the surface temperature change. Models and observations also indicate that a spatio-temporal pattern in the surface warming controls this additional contribution to the radiative response. However, several authors picture this effect as a feedback change in the atmosphere, reducing the role of the ocean's enthalpy-uptake variations. I use a widely-known linearised conceptual energy-balance model and its analytical solutions to find an explicit expression of the radiative response and its temporal evolution. This explicit expression provides another timescale in the Earth system, as the ocean-atmosphere coupling modulates the radiative response. Thus, to understand the variation of the climate feedback parameter, we need not only to know its relation to the spatio-temporal warming pattern but an improved picture of the ocean-atmosphere coupling that generates the pattern.</p>

scholarly journals Coupled Ocean–Atmosphere Response to Idealized Freshwater Forcing over the Western Tropical Pacific

2010 ◽  
Vol 23 (7) ◽  
pp. 1945-1954 ◽  
Author(s):  
Lixin Wu ◽  
Yan Sun ◽  
Jiaxu Zhang ◽  
Liping Zhang ◽  
Shoshiro Minobe
Keyword(s):  
Climate Model ◽  
Tropical Pacific ◽  
Meridional Overturning Circulation ◽  
Bjerknes Feedback ◽  
Atmospheric Teleconnection ◽  
Western Tropical Pacific ◽  
Freshwater Forcing ◽  
The Pacific ◽  
Ocean Atmosphere ◽  
The Tropics

Abstract The coupled ocean–atmosphere responses to idealized freshwater forcing in the western tropical Pacific are studied using a fully coupled climate model. The model explicitly demonstrates that freshwater forcing in the western tropical Pacific can lead to a basinwide response with the pattern resembling the Pacific decadal oscillation. In the tropics, a negative (positive) freshwater forcing over the western tropical Pacific decreases (increases) sea surface height locally, and sets up a positive (negative) zonal pressure gradient anomaly, which accelerates (decelerates) the meridional overturning circulation and equatorial surface westward flow. This leads to an intensification (reduction) of meridional heat divergence and vertical cold advection, and thus a development of La Niña (El Niño)–like responses in the tropics. The tropical responses are further substantiated by the positive Bjerknes feedback, and subsequently force significant changes in the extratropical North Pacific through atmospheric teleconnection. The local freshwater response also reinforces the imposed forcing, forming a positive feedback loop. Applications to Pacific climate changes are discussed.

scholarly journals Spatial Patterns of Modeled Climate Feedback and Contributions to Temperature Response and Polar Amplification

2011 ◽  
Vol 24 (14) ◽  
pp. 3575-3592 ◽  
Author(s):  
Julia A. Crook ◽  
Piers M. Forster ◽  
Nicola Stuber
Keyword(s):  
Heat Transport ◽  
Spatial Patterns ◽  
Temperature Response ◽  
Equilibrium Temperature ◽  
Lapse Rate ◽  
Climate Feedback ◽  
Local Climate ◽  
Polar Amplification ◽  
Forcing Mechanisms ◽  
High Level

Abstract Spatial patterns of local climate feedback and equilibrium partial temperature responses are produced from eight general circulation models with slab oceans forced by doubling carbon dioxide (CO2). The analysis is extended to other forcing mechanisms with the Met Office Hadley Centre slab ocean climate model version 3 (HadSM3). In agreement with previous studies, the greatest intermodel differences are in the tropical cloud feedbacks. However, the greatest intermodel spread in the equilibrium temperature response comes from the water vapor plus lapse rate feedback, not clouds, disagreeing with a previous study. Although the surface albedo feedback contributes most in the annual mean to the greater warming of high latitudes, compared to the tropics (polar amplification), its effect is significantly ameliorated by shortwave cloud feedback. In different seasons the relative importance of the contributions varies considerably, with longwave cloudy-sky feedback and horizontal heat transport plus ocean heat release playing a major role during winter and autumn when polar amplification is greatest. The greatest intermodel spread in annual mean polar amplification is due to variations in horizontal heat transport and shortwave cloud feedback. Spatial patterns of local climate feedback for HadSM3 forced with 2 × CO2, +2% solar, low-level scattering aerosol and high-level absorbing aerosol are more similar than those for different models forced with 2 × CO2. However, the equilibrium temperature response to high-level absorbing aerosol shows considerably enhanced polar amplification compared to the other forcing mechanisms, largely due to differences in horizontal heat transport and water vapor plus lapse rate feedback, with the forcing itself acting to reduce amplification. Such variations in high-latitude response between models and forcing mechanisms make it difficult to infer specific causes of recent Arctic temperature change.

scholarly journals A Theory for Bjerknes Compensation: The Role of Climate Feedback

2015 ◽  
Vol 29 (1) ◽  
pp. 191-208 ◽  
Author(s):  
Zhengyu Liu ◽  
Haijun Yang ◽  
Chengfei He ◽  
Yingying Zhao
Keyword(s):  
Temperature Gradient ◽  
Spatial Variation ◽  
Heat Transport ◽  
Positive Feedback ◽  
Climate Model ◽  
Temperature Response ◽  
Global Scale ◽  
Climate Feedback ◽  
Balance Model ◽  
Local Climate

Abstract The response of the atmospheric energy (heat) transport (AHT) to a perturbation oceanic heat transport (OHT) is studied theoretically in a zonal mean energy balance model, with the focus on the effect of climate feedback, especially its spatial variation, on Bjerknes compensation (BJC). It is found that the BJC depends critically on climate feedback. For a stable climate, in which negative climate feedback is dominant, the AHT always compensates the OHT in the opposite direction. Furthermore, if local climate feedback is negative everywhere, the AHT will be weaker than the OHT (undercompensation) because of the damping on the surface oceanic heating through the top-of-atmosphere energy loss. One novel finding is that the compensation magnitude depends on the spatial scale of the forcing and is bounded between a minimum at the global scale and a maximum (of perfect compensation) at small scales. Most interestingly, the BJC is affected significantly by the spatial variation of the feedback, particularly a local positive climate feedback. As such, a regional positive feedback can lead to a compensating AHT greater than the perturbation OHT (overcompensation). This occurs because the positive feedback enhances the local temperature response, the anomalous temperature gradient, and, in turn, the AHT. Finally, the poleward latent heat transport leads to a temperature response with a polar amplification accompanied by a polar steepening of temperature gradient but does not change the BJC significantly. Potential applications of this BJC theory to more complex climate model studies are also discussed.

scholarly journals Estimations of climate sensitivity based on top-of-atmosphere radiation imbalance

2010 ◽  
Vol 10 (4) ◽  
pp. 1923-1930 ◽  
Author(s):  
B. Lin ◽  
L. Chambers ◽  
B. Wielicki ◽  
Y. Hu ◽  
P. Minnis ◽  
...  
Keyword(s):  
Energy Balance ◽  
Heat Transport ◽  
Climate Sensitivity ◽  
Deep Ocean ◽  
Climate Feedback ◽  
Ocean Heat Transport ◽  
Middle Range ◽  
Condition Problem ◽  
System Memory ◽  
Feedback Coefficient

Abstract. Large climate feedback uncertainties limit the accuracy in predicting the response of the Earth's climate to the increase of CO2 concentration within the atmosphere. This study explores a potential to reduce uncertainties in climate sensitivity estimations using energy balance analysis, especially top-of-atmosphere (TOA) radiation imbalance. The time-scales studied generally cover from decade to century, that is, middle-range climate sensitivity is considered, which is directly related to the climate issue caused by atmospheric CO2 change. The significant difference between current analysis and previous energy balance models is that the current study targets at the boundary condition problem instead of solving the initial condition problem. Additionally, climate system memory and deep ocean heat transport are considered. The climate feedbacks are obtained based on the constraints of the TOA radiation imbalance and surface temperature measurements of the present climate. In this study, the TOA imbalance value of 0.85 W/m2 is used. Note that this imbalance value has large uncertainties. Based on this value, a positive climate feedback with a feedback coefficient ranging from −1.3 to −1.0 W/m2/K is found. The range of feedback coefficient is determined by climate system memory. The longer the memory, the stronger the positive feedback. The estimated time constant of the climate is large (70~120 years) mainly owing to the deep ocean heat transport, implying that the system may be not in an equilibrium state under the external forcing during the industrial era. For the doubled-CO2 climate (or 3.7 W/m2 forcing), the estimated global warming would be 3.1 K if the current estimate of 0.85 W/m2 TOA net radiative heating could be confirmed. With accurate long-term measurements of TOA radiation, the analysis method suggested by this study provides a great potential in the estimations of middle-range climate sensitivity.

Experimental estimation of the local energy balance of the potential-confining electrons in tandem-mirror plasmas

2006 ◽  
Vol 77 (10) ◽  
pp. 10F302
Author(s):  
T. Numakura ◽  
T. Cho ◽  
J. Kohagura ◽  
M. Hirata ◽  
R. Minami ◽  
...  
Keyword(s):  
Energy Balance ◽  
Local Energy ◽  
Tandem Mirror ◽  
Experimental Estimation
Sign in / Sign up

Export Citation Format

Share Document