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.

scholarly journals Climate Determinism Revisited: Multiple Equilibria in a Complex Climate Model

2011 ◽  
Vol 24 (4) ◽  
pp. 992-1012 ◽  
Author(s):  
David Ferreira ◽  
John Marshall ◽  
Brian Rose
Keyword(s):  
Energy Balance ◽  
Sea Ice ◽  
Heat Transport ◽  
Ocean Circulation ◽  
General Circulation ◽  
Multiple Equilibria ◽  
Climate Model ◽  
Hydrological Cycle ◽  
Ocean Heat Transport ◽  
Ice Cap

Abstract Multiple equilibria in a coupled ocean–atmosphere–sea ice general circulation model (GCM) of an aquaplanet with many degrees of freedom are studied. Three different stable states are found for exactly the same set of parameters and external forcings: a cold state in which a polar sea ice cap extends into the midlatitudes; a warm state, which is ice free; and a completely sea ice–covered “snowball” state. Although low-order energy balance models of the climate are known to exhibit intransitivity (i.e., more than one climate state for a given set of governing equations), the results reported here are the first to demonstrate that this is a property of a complex coupled climate model with a consistent set of equations representing the 3D dynamics of the ocean and atmosphere. The coupled model notably includes atmospheric synoptic systems, large-scale circulation of the ocean, a fully active hydrological cycle, sea ice, and a seasonal cycle. There are no flux adjustments, with the system being solely forced by incoming solar radiation at the top of the atmosphere. It is demonstrated that the multiple equilibria owe their existence to the presence of meridional structure in ocean heat transport: namely, a large heat transport out of the tropics and a relatively weak high-latitude transport. The associated large midlatitude convergence of ocean heat transport leads to a preferred latitude at which the sea ice edge can rest. The mechanism operates in two very different ocean circulation regimes, suggesting that the stabilization of the large ice cap could be a robust feature of the climate system. Finally, the role of ocean heat convergence in permitting multiple equilibria is further explored in simpler models: an atmospheric GCM coupled to a slab mixed layer ocean and an energy balance model.

Consistent Differences in Climate Feedbacks between Atmosphere–Ocean GCMs and Atmospheric GCMs with Slab-Ocean Models*

2013 ◽  
Vol 26 (12) ◽  
pp. 4264-4281 ◽  
Author(s):  
Karen M. Shell
Keyword(s):  
Water Vapor ◽  
General Circulation ◽  
Ocean Dynamics ◽  
Lapse Rate ◽  
Climate Feedbacks ◽  
Temperature Changes ◽  
Model Type ◽  
Global Average ◽  
Ocean Models ◽  
Slab Ocean

Abstract Climate sensitivity is generally studied using two types of models. Atmosphere–ocean general circulation models (AOGCMs) include interactive ocean dynamics and detailed heat uptake. Atmospheric GCMs (AGCMs) with slab ocean models (SOMs) cannot fully simulate the ocean’s response to and influence on climate. However, AGCMs are computationally cheaper and thus are often used to quantify and understand climate feedbacks and sensitivity. Here, physical climate feedbacks are compared between AOGCMs and SOM-AGCMs from the Coupled Model Intercomparison Project phase 3 (CMIP3) using the radiative kernel technique. Both the global-average (positive) water vapor and (negative) lapse-rate feedbacks are consistently stronger in AOGCMs. Water vapor feedback differences result from an essentially constant relative humidity and peak in the tropics, where temperature changes are larger for AOGCMs. Differences in lapse-rate feedbacks extend to midlatitudes and correspond to a larger ratio of tropical- to global-average temperature changes. Global-average surface albedo feedbacks are similar between models types because of a near cancellation of Arctic and Antarctic differences. In AOGCMs, the northern high latitudes warm faster than the southern latitudes, resulting in interhemispheric differences in albedo, water vapor, and lapse-rate feedbacks lacking in the SOM-AGCMs. Meridional heat transport changes also depend on the model type, although there is a large intermodel spread. However, there are no consistent global or zonal differences in cloud feedbacks. Effects of the forcing scenario [Special Report on Emissions Scenarios A1B (SRESa1b) or the 1% CO2 increase per year to doubling (1%to2x) experiments] on feedbacks are model dependent and generally of lesser importance than the model type. Care should be taken when using SOM-AGCMs to understand AOGCM feedback behavior.

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.

scholarly journals Ocean Heat Transport, Sea Ice, and Multiple Climate States: Insights from Energy Balance Models

2009 ◽  
Vol 66 (9) ◽  
pp. 2828-2843 ◽  
Author(s):  
Brian E. J. Rose ◽  
John Marshall
Keyword(s):  
Energy Balance ◽  
Sea Ice ◽  
Heat Transport ◽  
Wind Stress ◽  
Ocean Heat Transport ◽  
Meridional Transport ◽  
Meridional Heat Transport ◽  
Ocean Gyres ◽  
Ice Edge ◽  
Energy Balance Models

Abstract Several extensions of energy balance models (EBMs) are explored in which (i) sea ice acts to insulate the atmosphere from the ocean and (ii) ocean heat transport is allowed to have some meridional structure controlled by the wind, with minima at which the ice edge can rest. These new models support multiple stable ice edges not found in the classical EBM and a hysteresis loop capable of generating abrupt warming as the ice edge “jumps” from mid- to high latitudes. The new equilibria are demonstrated in two classes of model, in which the wind stress is either specified externally or generated interactively. Wind stress is computed by introducing a dynamical constraint into the EBM to represent the simultaneous meridional transport of energy and angular momentum in the atmosphere. This wind stress is used to drive ocean gyres, with associated structure in their meridional heat transport, so that the atmosphere and ocean are coupled together both thermally and mechanically.

scholarly journals Explorations of Atmosphere–Ocean–Ice Climates on an Aquaplanet and Their Meridional Energy Transports

2009 ◽  
Vol 66 (6) ◽  
pp. 1593-1611 ◽  
Author(s):  
Daniel Enderton ◽  
John Marshall
Keyword(s):  
Solar Radiation ◽  
Heat Transport ◽  
Ocean Circulation ◽  
Total Heat ◽  
Radiation Budget ◽  
Detailed Calculation ◽  
Test Bed ◽  
Polar Ice ◽  
Meridional Heat Transport ◽  
Ice Caps

Abstract The degree to which total meridional heat transport is sensitive to the details of its atmospheric and oceanic components is explored. A coupled atmosphere, ocean, and sea ice model of an aquaplanet is employed to simulate very different climates—some with polar ice caps, some without—even though they are driven by the same incoming solar flux. Differences arise due to varying geometrical constraints on ocean circulation influencing its ability to transport heat meridionally. Without complex land configurations, the results prove easier to diagnose and compare to theory and simple models and, hence, provide a useful test bed for ideas about heat transport and its partition within the climate system. In particular, the results are discussed in the context of a 1978 study by Stone, who argued that for a planet with Earth’s astronomical parameters and rotation rate, the total meridional heat transport would be independent of the detailed dynamical processes responsible for that transport and depend primarily on the distribution of incoming solar radiation and the mean planetary albedo. The authors find that in warm climates in which there is no ice, Stone’s result is a useful guide. In cold climates with significant polar ice caps, however, meridional gradients in albedo significantly affect the absorption of solar radiation and need to be included in any detailed calculation or discussion of total heat transport. Since the meridional extent of polar ice caps is sensitive to details of atmospheric and oceanic circulation, these cannot be ignored. Finally, what has been learned is applied to a study of the total heat transport estimated from the Earth Radiation Budget Experiment (ERBE) data.

scholarly journals The Effect of Cloud Cover on the Meridional Heat Transport: Lessons from Variable Rotation Experiments

2017 ◽  
Vol 30 (18) ◽  
pp. 7465-7479 ◽  
Author(s):  
Xiaojuan Liu ◽  
David S. Battisti ◽  
Gerard H. Roe
Keyword(s):  
Heat Transport ◽  
Rotation Rate ◽  
Longwave Radiation ◽  
Eddy Diffusivity ◽  
Hadley Cell ◽  
Shortwave Radiation ◽  
Strong Increase ◽  
Meridional Heat Transport ◽  
Mixing Length Theory ◽  
Fast Rotating

Abstract The question “What determines the meridional heat transport (MHT)?” is explored by performing a series of rotation-rate experiments with an aquaplanet GCM coupled to a slab ocean. The change of meridional heat transport with rotation rate falls into two regimes: in a “slow rotating” regime (rotation rate < 1/2 modern rotation) MHT decreases with increasing rotation rate, whereas in a “fast rotating” regime (rotation rate ≥ 1/2 modern rotation) MHT is nearly invariant. The two-regime feature of MHT is primarily related to the reduction in tropical clouds and increase in tropical temperature that are associated with the narrowing and weakening of the Hadley cell with increasing rotation rate. In the slow-rotating regime, the Hadley cell contracts and weakens as rotation rate is increased; the resulting warming causes a local increase in outgoing longwave radiation (OLR), which consequently decreases MHT. In the fast-rotating regime, the Hadley cell continues to contract as rotation rate is increased, resulting in a decrease in tropical and subtropical clouds that increases the local absorbed shortwave radiation (ASR) by an amount that almost exactly compensates the local increases in OLR. In the fast-rotating regime, the model heat transport is approximately diffusive, with an effective eddy diffusivity that is consistent with eddy mixing-length theory. The effective eddy diffusivity decreases with increasing rotation rate. However, this decrease is nearly offset by a strong increase in the meridional gradient of moist static energy and hence results in a near-constancy of MHT. The results herein extend previous work on the MHT by highlighting that the spatial patterns of clouds and the factors that influence them are leading controls on MHT.

scholarly journals A conceptual model of oceanic heat transport in the Snowball Earth scenario

2016 ◽  
Author(s):  
D. Comeau ◽  
D. A. Kurtze ◽  
J. M. Restrepo
Keyword(s):  
Heat Transport ◽  
Ocean Circulation ◽  
General Circulation ◽  
Heat Budget ◽  
Global Climate ◽  
General Circulation Models ◽  
Complex Model ◽  
Snowball Earth ◽  
Radiative Balance ◽  
Oceanic Heat Transport

Abstract. Geologic evidence suggests that the Earth may have been completely covered in ice in the distant past, a state known as Snowball Earth. This is still the subject of controversy, and has been the focus of modeling work from low dimensional models up to state of the art general circulation models. In our present global climate, the ocean plays a large role in redistributing heat from the equatorial regions to high latitudes, and as an important part of the global heat budget, its role in the initiation a Snowball Earth, and the subsequent climate, is of great interest. To better understand the role of oceanic heat transport in the initiation of Snowball Earth, and the resulting global ice covered climate state, the goal of this inquiry is two-fold: we wish to propose the least complex model that can capture the Snowball scenario as well as the present day climate with partial ice cover, and we want to determine the relative importance of oceanic heat transport. To do this, we develop a simple model, incorporating thermohaline dynamics from traditional box ocean models, a radiative balance from energy balance models, as well as the more contemporary "sea glacier" model to account for viscous flow effects of extremely thick sea ice. The resulting model, consisting of dynamic ocean and ice components, is able to reproduce both Snowball Earth as well as present day conditions through reasonable changes in forcing parameters. We find that including or neglecting oceanic heat transport may lead to vastly different global climate states, and also that the parameterization of under ice heat transfer in the ice/ocean coupling, plays a key role in the resulting global climate state, demonstrating the regulatory effect of dynamic ocean heat transport. Furthermore we find that the ocean circulation direction exhibits bistability in the Snowball Earth regime.

scholarly journals Early Eocene vigorous ocean overturning and its contribution to a warm Southern Ocean

2020 ◽  
Vol 16 (4) ◽  
pp. 1263-1283 ◽  
Author(s):  
Yurui Zhang ◽  
Thierry Huck ◽  
Camille Lique ◽  
Yannick Donnadieu ◽  
Jean-Baptiste Ladant ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Heat Transport ◽  
Southern Hemisphere ◽  
Ocean Circulation ◽  
Deep Convection ◽  
Feedback Mechanism ◽  
Atmospheric Co2 ◽  
Early Eocene ◽  
Meridional Heat Transport ◽  
Overturning Circulation

Abstract. The early Eocene (∼55 Ma) was the warmest period of the Cenozoic and was most likely characterized by extremely high atmospheric CO2 concentrations. Here, we analyze simulations of the early Eocene performed with the IPSL-CM5A2 Earth system model, set up with paleogeographic reconstructions of this period from the DeepMIP project and with different levels of atmospheric CO2. When compared with proxy-based reconstructions, the simulations reasonably capture both the reconstructed amplitude and pattern of early Eocene sea surface temperature. A comparison with simulations of modern conditions allows us to explore the changes in ocean circulation and the resulting ocean meridional heat transport. At a CO2 level of 840 ppm, the early Eocene simulation is characterized by a strong abyssal overturning circulation in the Southern Hemisphere (40 Sv at 60∘ S), fed by deepwater formation in the three sectors of the Southern Ocean. Deep convection in the Southern Ocean is favored by the closed Drake and Tasmanian passages, which provide western boundaries for the buildup of strong subpolar gyres in the Weddell and Ross seas, in the middle of which convection develops. The strong overturning circulation, associated with subpolar gyres, sustains the poleward advection of saline subtropical water to the convective regions in the Southern Ocean, thereby maintaining deepwater formation. This salt–advection feedback mechanism is akin to that responsible for the present-day North Atlantic overturning circulation. The strong abyssal overturning circulation in the 55 Ma simulations primarily results in an enhanced poleward ocean heat transport by 0.3–0.7 PW in the Southern Hemisphere compared to modern conditions, reaching 1.7 PW southward at 20∘ S, and contributes to keeping the Southern Ocean and Antarctica warm in the Eocene. Simulations with different atmospheric CO2 levels show that ocean circulation and heat transport are relatively insensitive to CO2 doubling.

What Determines Meridional Heat Transport in Climate Models?

2012 ◽  
Vol 25 (11) ◽  
pp. 3832-3850 ◽  
Author(s):  
Aaron Donohoe ◽  
David S. Battisti
Keyword(s):  
Solar Radiation ◽  
Heat Transport ◽  
Outgoing Longwave Radiation ◽  
Climate Models ◽  
Longwave Radiation ◽  
Incident Radiation ◽  
Meridional Heat Transport ◽  
Surface Reflection ◽  
Global Average ◽  
Planetary Albedo

The annual mean maximum meridional heat transport (MHTMAX) differs by approximately 20% among coupled climate models. The value of MHTMAX can be expressed as the difference between the equator-to-pole contrast in absorbed solar radiation (ASR*) and outgoing longwave radiation (OLR*). As an example, in the Northern Hemisphere observations, the extratropics (defined as the region with a net radiative deficit) receive an 8.2-PW deficit of net solar radiation (ASR*) relative to the global average that is balanced by a 2.4-PW deficit of outgoing longwave radiation (OLR*) and 5.8 PW of energy import via the atmospheric and oceanic circulation (MHTMAX). The intermodel spread of MHTMAX in the Coupled Model Intercomparison Project Phase 3 (CMIP3) simulations of the preindustrial climate is primarily (R2 = 0.72) due to differences in ASR* while model differences in OLR* are uncorrelated with the MHTMAX spread. The net solar radiation (ASR*) is partitioned into contributions from (i) the equator-to-pole contrast in incident radiation acting on the global average albedo and (ii) the equator-to-pole contrast of planetary albedo, which is further subdivided into components due to atmospheric and surface reflection. In the observations, 62% of ASR* is due to the meridional distribution of incident radiation, 33% is due to atmospheric reflection, and 5% is due to surface reflection. The intermodel spread in ASR* is due to model differences in the equator-to-pole gradient in planetary albedo, which are primarily a consequence of atmospheric reflection differences (92% of the spread), and is uncorrelated with differences in surface reflection. As a consequence, the spread in MHTMAX in climate models is primarily due to the spread in cloud reflection properties.

scholarly journals Tropical Precipitation and Cross-Equatorial Ocean Heat Transport during the Mid-Holocene

2017 ◽  
Vol 30 (10) ◽  
pp. 3529-3547 ◽  
Author(s):  
Xiaojuan Liu ◽  
David S. Battisti ◽  
Aaron Donohoe
Keyword(s):  
Heat Transport ◽  
Northern Hemisphere ◽  
Ocean Circulation ◽  
Climate Models ◽  
Energy Transport ◽  
Hadley Cell ◽  
Upper Ocean ◽  
Ocean Heat Transport ◽  
Tropical Precipitation ◽  
Coupled Climate Models

Abstract Summertime insolation intensified in the Northern Hemisphere during the mid-Holocene, resulting in enhanced monsoonal precipitation. In this study, the authors examine the changes in the annual-mean tropical precipitation as well as changes in atmospheric circulation and upper-ocean circulation in the mid-Holocene compared to the preindustrial climate, as simulated by 12 coupled climate models from PMIP3. In addition to the predominant zonally asymmetric changes in tropical precipitation, there is a small northward shift in the location of intense zonal-mean precipitation (mean ITCZ) in the mid-Holocene in the majority (9 out of 12) of the coupled climate models. In contrast, the shift is southward in simulations using an atmospheric model coupled to a slab ocean. The northward mean ITCZ shift in the coupled simulations is due to enhanced northward ocean heat transport across the equator [OHT(EQ)], which demands a compensating southward atmospheric energy transport across the equator, accomplished by shifting the Hadley cell and hence the mean ITCZ northward. The increased northward OHT(EQ) is primarily accomplished by changes in the upper-ocean gyre circulation in the tropical Pacific acting on the zonally asymmetric climatological temperature distribution. The gyre intensification results from the intensification of the monsoonal winds in the Northern Hemisphere and the weakening of the winds in the Southern Hemisphere, both of which are forced directly by the insolation changes.

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