scholarly journals Relations between Northward Ocean and Atmosphere Energy Transports in a Coupled Climate Model

2008 ◽  
Vol 21 (3) ◽  
pp. 561-575 ◽  
Author(s):  
Michael Vellinga ◽  
Peili Wu
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Energy Transport ◽  
Climate Model ◽  
Atmospheric Transport ◽  
Circulation Model ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Transport ◽  
Poleward Heat Transport ◽  
Low Latitudes

Abstract The Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) is used to analyze the relation between northward energy transports in the ocean and atmosphere at centennial time scales. In a transient water-hosing experiment, where suppressing the Atlantic meridional overturning circulation (MOC) causes a reduction in northward ocean heat transport of up to 0.75 PW (i.e., 75%), the atmosphere compensates by increasing its northward transport of moist static energy. This compensation is very efficient at low latitudes and near complete at the equator throughout the experiment, but is incomplete farther north across the northern midlatitude storm tracks. The change in atmosphere energy transport enables the model to find a new global-mean radiative equilibrium after 240 yr. In a perturbed physics ensemble of HadCM3 it was found that time-averaged meridional energy transports in ocean and atmosphere can act opposingly. Where model formulation causes an unbalanced mean climate state, for example, an excessive top-of-the-atmosphere radiative surplus at low latitudes, the atmosphere increases its poleward energy transport to disperse this excess. MOC and ocean poleward heat transport tend to be reduced in such model versions, and this offsets the increased poleward atmospheric transport of the low-latitude energy surplus. Model versions that are close to net radiative equilibrium also have ocean heat transport and MOC close to observed values.

scholarly journals The Importance of Ocean Dynamical Feedback for Understanding the Impact of Mid–High-Latitude Warming on Tropical Precipitation Change

2018 ◽  
Vol 31 (6) ◽  
pp. 2417-2434 ◽  
Author(s):  
Masakazu Yoshimori ◽  
Ayako Abe-Ouchi ◽  
Hiroaki Tatebe ◽  
Toru Nozawa ◽  
Akira Oka
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Precipitation Change ◽  
Meridional Overturning Circulation ◽  
Climate Projections ◽  
Ocean Heat Transport ◽  
Tropical Precipitation ◽  
The Impact

It has been shown that asymmetric warming between the Northern and Southern Hemisphere extratropics induces a meridional displacement of tropical precipitation. This shift is believed to be due to the extra energy transported from the differentially heated hemisphere through changes in the Hadley circulation. Generally, the column-integrated energy flux in the mean meridional overturning circulation follows the direction of the upper, relatively dry branch, and tropical precipitation tends to be intensified in the hemisphere with greater warming. This framework was originally applied to simulations that did not include ocean dynamical feedback, but was recently extended to take the ocean heat transport change into account. In the current study, an atmosphere–ocean general circulation model applied with a regional nudging technique is used to investigate the impact of extratropical warming on tropical precipitation change under realistic future climate projections. It is shown that warming at latitudes poleward of 40° causes the northward displacement of tropical precipitation from October to January. Warming at latitudes poleward of 60° alone has a much smaller effect. This change in the tropical precipitation is largely explained by the atmospheric moisture transport caused by changes in the atmospheric circulation. The larger change in ocean heat transport near the equator, relative to the atmosphere, is consistent with the extended energy framework. The current study provides a complementary dynamical framework that highlights the importance of midlatitude atmospheric eddies and equatorial ocean upwelling, where the atmospheric eddy feedback modifies the Hadley circulation resulting in the northward migration of precipitation and the ocean dynamical feedback damps the northward migration from the equator.

Bjerknes Compensation and the Decadal Variability of the Energy Transports in a Coupled Climate Model

2006 ◽  
Vol 19 (7) ◽  
pp. 1167-1181 ◽  
Author(s):  
Len Shaffrey ◽  
Rowan Sutton
Keyword(s):  
Atlantic Ocean ◽  
General Circulation ◽  
Energy Transport ◽  
Climate Model ◽  
Decadal Variability ◽  
Circulation Model ◽  
Surface Fluxes ◽  
Meridional Overturning Circulation ◽  
Ocean Energy ◽  
Pole Surface

Abstract In the 1960s, Jacob Bjerknes suggested that if the top-of-the-atmosphere (TOA) fluxes and the oceanic heat storage did not vary too much, then the total energy transport by the climate system would not vary too much either. This implies that any large anomalies of oceanic and atmospheric energy transport should be equal and opposite. This simple scenario has become known as Bjerknes compensation. A long control run of the Third Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) has been investigated. It was found that northern extratropical decadal anomalies of atmospheric and oceanic energy transports are significantly anticorrelated and have similar magnitudes, which is consistent with the predictions of Bjerknes compensation. The degree of compensation in the northern extratropics was found to increase with increasing time scale. Bjerknes compensation did not occur in the Tropics, primarily as large changes in the surface fluxes were associated with large changes in the TOA fluxes. In the ocean, the decadal variability of the energy transport is associated with fluctuations in the meridional overturning circulation in the Atlantic Ocean. A stronger Atlantic Ocean energy transport leads to strong warming of surface temperatures in the Greenland–Iceland–Norwegian (GIN) Seas, which results in a reduced equator-to-pole surface temperature gradient and reduced atmospheric baroclinicity. It is argued that a stronger Atlantic Ocean energy transport leads to a weakened atmospheric transient energy transport.

scholarly journals Global-Scale Energy and Freshwater Balance in Glacial Climate: A Comparison of Three PMIP2 LGM Simulations

2008 ◽  
Vol 21 (19) ◽  
pp. 5008-5033 ◽  
Author(s):  
Shigenori Murakami ◽  
Rumi Ohgaito ◽  
Ayako Abe-Ouchi ◽  
Michel Crucifix ◽  
Bette L. Otto-Bliesner
Keyword(s):  
Water Vapor ◽  
Heat Transport ◽  
General Circulation ◽  
Lower Troposphere ◽  
Circulation Model ◽  
Meridional Overturning Circulation ◽  
Water Vapor Transport ◽  
Second Phase ◽  
Low Latitudes ◽  
Freshwater Balance

Abstract Three coupled atmosphere–ocean general circulation model (AOGCM) simulations of the Last Glacial Maximum (LGM: about 21 000 yr before present), conducted under the protocol of the second phase of the Paleoclimate Modelling Intercomparison Project (PMIP2), have been analyzed from a viewpoint of large-scale energy and freshwater balance. Atmospheric latent heat (LH) transport decreases at most latitudes due to reduced water vapor content in the lower troposphere, and dry static energy (DSE) transport in northern midlatitudes increases and changes the intensity contrast between the Pacific and Atlantic regions due to enhanced stationary waves over the North American ice sheets. In low latitudes, even with an intensified Hadley circulation in the Northern Hemisphere (NH), reduced DSE transport by the mean zonal circulation as well as a reduced equatorward LH transport is observed. The oceanic heat transport at NH midlatitudes increases owing to intensified subpolar gyres, and the Atlantic heat transport at low latitudes increases in all models whether or not meridional overturning circulation (MOC) intensifies. As a result, total poleward energy transport at the LGM increases in NH mid- and low latitudes in all models. Oceanic freshwater transport decreases, compensating for the response of the atmospheric water vapor transport. These responses in the atmosphere and ocean make the northern North Atlantic Ocean cold and relatively fresh, and the Southern Ocean relatively warm and saline. This is a common and robust feature in all models. The resultant ocean densities and ocean MOC response, however, show model dependency.

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.

scholarly journals Effects of Tropical Cyclones on Ocean Heat Transport in a High-Resolution Coupled General Circulation Model

2011 ◽  
Vol 24 (16) ◽  
pp. 4368-4384 ◽  
Author(s):  
Enrico Scoccimarro ◽  
Silvio Gualdi ◽  
Alessio Bellucci ◽  
Antonella Sanna ◽  
Pier Giuseppe Fogli ◽  
...  
Keyword(s):  
Twentieth Century ◽  
High Resolution ◽  
Heat Transport ◽  
Tropical Cyclones ◽  
General Circulation Model ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Ocean Heat Transport ◽  
Coupled General Circulation Model

Abstract In this paper the interplay between tropical cyclones (TCs) and the Northern Hemispheric ocean heat transport (OHT) is investigated. In particular, results from a numerical simulation of the twentieth-century and twenty-first-century climates, following the Intergovernmental Panel on Climate Change (IPCC) twentieth-century run (20C3M) and A1B scenario protocols, respectively, have been analyzed. The numerical simulations have been performed using a state-of-the-art global atmosphere–ocean–sea ice coupled general circulation model (CGCM) with relatively high-resolution (T159) in the atmosphere. The CGCM skill in reproducing a realistic TC climatology has been assessed by comparing the model results from the simulation of the twentieth century with available observations. The model simulates tropical cyclone–like vortices with many features similar to the observed TCs. Specifically, the simulated TCs exhibit realistic structure, geographical distribution, and interannual variability, indicating that the model is able to capture the basic mechanisms linking the TC activity with the large-scale circulation. The cooling of the surface ocean observed in correspondence of the TCs is well simulated by the model. TC activity is shown to significantly increase the poleward OHT out of the tropics and decrease the poleward OHT from the deep tropics on short time scales. This effect, investigated by looking at the 100 most intense Northern Hemisphere TCs, is strongly correlated with the TC-induced momentum flux at the ocean surface, where the winds associated with the TCs significantly weaken (strengthen) the trade winds in the 5°–18°N (18°–30°N) latitude belt. However, the induced perturbation does not impact the yearly averaged OHT. The frequency and intensity of the TCs appear to be substantially stationary through the entire 1950–2069 simulated period, as does the effect of the TCs on the OHT.

Poleward Stationary Eddy Heat Transport by the Tibetan Plateau and Equatorward Shift of Westerlies during Northern Winter*

2013 ◽  
Vol 70 (10) ◽  
pp. 3288-3301 ◽  
Author(s):  
Hyo-Seok Park ◽  
Shang-Ping Xie ◽  
Seok-Woo Son
Keyword(s):  
Tibetan Plateau ◽  
Heat Transport ◽  
General Circulation ◽  
Hot Spot ◽  
Circulation Model ◽  
The Tibetan Plateau ◽  
Stationary Waves ◽  
Transient Eddy ◽  
Poleward Heat Transport ◽  
Eddy Heat Transport

Abstract The orographic effect of the Tibetan Plateau on atmospheric poleward heat transport is investigated using an atmospheric general circulation model. The linear interference between the Tibetan Plateau–induced winds and the eddy temperature field associated with the land–sea thermal contrast is a key factor for enhancing the poleward stationary eddy heat transport. Specifically, Tibetan Plateau–induced stationary waves produce northerlies over the cold eastern Eurasian continent, leading to a poleward heat transport. In another hot spot of stationary eddy heat transport over the eastern North Pacific, Tibetan Plateau–induced stationary waves transport relatively warm marine air northward. In an experiment where the Tibetan Plateau is removed, the poleward heat transport is mostly accomplished by transient eddies, similar to the Southern Hemisphere. In the presence of the Tibetan Plateau, the enhanced stationary eddy heat transport is offset by a comparable reduction in transient eddy heat transport. This compensation between stationary and transient eddy heat transport is seen in observed interannual variability. Both the model and observations indicate that an enhanced poleward heat transport by stationary waves weakens transient eddies by decreasing the meridional temperature gradient and the associated westerlies in midlatitudes.

scholarly journals PlioMIP2 simulations using the MIROC4m climate model

2020 ◽  
Author(s):  
Wing-Le Chan ◽  
Ayako Abe-Ouchi
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
Second Phase ◽  
Climate Modelling ◽  
Model Intercomparison ◽  
Model Data

Abstract. The second phase of the Pliocene Model Intercomparison Project (PlioMIP2) has attracted many climate modelling groups in its continuing efforts to better understand the climate of the mid-Piacenzian warm period (mPWP) when atmospheric CO2 was last closest to present day levels. Like the first phase, PlioMIP1, it is an internationally coordinated initiative that allows for a systematic comparison of various models in a similar manner to PMIP. Model intercomparison and model-data comparison now focus specifically on the interglacial at marine isotope stage KM5c (3.205 Ma) and experimental design is not only based on new boundary conditions but includes various sensitivity experiments. In this study, we present results from long-term model integrations using the MIROC4m atmosphere-ocean coupled general circulation model, developed at the institutes CCSR/NIES/FRCGC in Japan. The core experiment, with CO2 levels set to 400 ppm, shows a warming of 3.1 °C compared to the Pre-Industrial, with two-thirds of the warming being contributed by the increase in CO2. Although this level of warming is less than that in the equivalent PlioMIP1 experiment, there is a slightly better agreement with proxy sea surface temperature (SST) data at PRISM3 locations, especially in the northern North Atlantic where there were large model-data discrepancies in PlioMIP1. Similar changes in precipitation and sea ice are seen and the Arctic remains ice-free in the summer. However, unlike PlioMIP1, the Atlantic Meridional Overturning Circulation (AMOC) is now stronger than that of the Pre-Industrial, even though increasing CO2 tends to weaken it. This stronger AMOC is a consequence of a closed Bering Strait in the PlioMIP2 paleogeography. Also, when present day boundary conditions are replaced by those of the Pliocene, the dependency of the AMOC strength on CO2 is significantly weakened. Sensitivity tests show that lower values of CO2 give a global SST which is overall more consistent with the PRISM3 SST field presented in PlioMIP1. Inclusion of dynamical vegetation and the effects of all realistic orbital configurations should be considered in future experiments using MIROC4m for the mPWP.

A multimodel investigation of atmospheric mechanisms for driving Arctic amplification in warmer climates

2021 ◽  
pp. 1-55
Author(s):  
Deepashree Dutta ◽  
Steven C. Sherwood ◽  
Katrin J. Meissner ◽  
Alex Sen Gupta ◽  
Daniel J. Lunt ◽  
...  
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Energy Transport ◽  
Longwave Radiation ◽  
General Circulation Models ◽  
The Arctic ◽  
Arctic Warming ◽  
Surface Warming ◽  
Poleward Heat Transport ◽  
Warm Climates

AbstractWhen simulating past warm climates, such as the early Cretaceous and Paleogene periods, general circulation models (GCMs) underestimate the magnitude of warming in the Arctic. Additionally, model intercomparisons show a large spread in the magnitude of Arctic warming for these warmer-than-modern climates. Several mechanisms have been proposed to explain these disagreements, including the unrealistic representation of polar clouds or underestimated poleward heat transport in the models. This study provides an intercomparison of Arctic cloud and atmospheric heat transport (AHT) responses to strong imposed polar-amplified surface ocean warming across four atmosphere-only GCMs. All models simulate an increase in high clouds throughout the year; the resulting reduction in longwave radiation loss to space acts to support the imposed Arctic warming. The response of low and mid-level clouds varies considerably across the models, with models responding differently to surface warming and sea ice removal. The AHT is consistently weaker in the imposed warming experiments due to a large reduction in dry static energy transport that offsets a smaller increase in latent heat transport, thereby opposing the imposed surface warming. Our idealised polar amplification experiments require very large increases in implied ocean heat transport (OHT) to maintain steady state. Increased CO2 or tropical temperatures that likely characterised past warm climates, reduces the need for such large OHT increases.

scholarly journals Sensitivity of Pliocene climate simulations in MRI-CGCM2.3 to respective boundary conditions

2016 ◽  
Vol 12 (8) ◽  
pp. 1619-1634 ◽  
Author(s):  
Youichi Kamae ◽  
Kohei Yoshida ◽  
Hiroaki Ueda
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Model Comparison ◽  
Climate Model ◽  
Phase 1 ◽  
Regional Climate ◽  
Circulation Model ◽  
Poleward Heat Transport ◽  
Climate Simulations ◽  
Intercomparison Project

Abstract. Accumulations of global proxy data are essential steps for improving reliability of climate model simulations for the Pliocene warming climate. In the Pliocene Model Intercomparison Project phase 2 (PlioMIP2), a part project of the Paleoclimate Modelling Intercomparison Project phase 4, boundary forcing data have been updated from the PlioMIP phase 1 due to recent advances in understanding of oceanic, terrestrial and cryospheric aspects of the Pliocene palaeoenvironment. In this study, sensitivities of Pliocene climate simulations to the newly archived boundary conditions are evaluated by a set of simulations using an atmosphere–ocean coupled general circulation model, MRI-CGCM2.3. The simulated Pliocene climate is warmer than pre-industrial conditions for 2.4 °C in global mean, corresponding to 0.6 °C warmer than the PlioMIP1 simulation by the identical climate model. Revised orography, lakes, and shrunk ice sheets compared with the PlioMIP1 lead to local and remote influences including snow and sea ice albedo feedback, and poleward heat transport due to the atmosphere and ocean that result in additional warming over middle and high latitudes. The amplified higher-latitude warming is supported qualitatively by the proxy evidences, but is still underestimated quantitatively. Physical processes responsible for the global and regional climate changes should be further addressed in future studies under systematic intermodel and data–model comparison frameworks.

scholarly journals Response of the Hadley Circulation to Climate Change in an Aquaplanet GCM Coupled to a Simple Representation of Ocean Heat Transport

2011 ◽  
Vol 68 (4) ◽  
pp. 769-783 ◽  
Author(s):  
Xavier J. Levine ◽  
Tapio Schneider
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Climate Models ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Dynamical Regime ◽  
Ocean Heat Transport ◽  
Simple Representation ◽  
Wide Range ◽  
Momentum Fluxes

Abstract It is unclear how the width and strength of the Hadley circulation are controlled and how they respond to climate changes. Simulations of global warming scenarios with comprehensive climate models suggest the Hadley circulation may widen and weaken as the climate warms. But these changes are not quantitatively consistent among models, and how they come about is not understood. Here, a wide range of climates is simulated with an idealized moist general circulation model (GCM) coupled to a simple representation of ocean heat transport, in order to place past and possible future changes in the Hadley circulation into a broader context and to investigate the mechanisms responsible for them. By comparison of simulations with and without ocean heat transport, it is shown that it is essential to take low-latitude ocean heat transport and its coupling to wind stress into account to obtain Hadley circulations in a dynamical regime resembling Earth’s, particularly in climates resembling present-day Earth’s and colder. As the optical thickness of an idealized longwave absorber in the simulations is increased and the climate warms, the Hadley circulation strengthens in colder climates and weakens in warmer climates; it has maximum strength in a climate close to present-day Earth’s. In climates resembling present-day Earth’s and colder, the Hadley circulation strength is largely controlled by the divergence of angular momentum fluxes associated with eddies of midlatitude origin; the latter scale with the mean available potential energy in midlatitudes. The importance of these eddy momentum fluxes for the Hadley circulation strength gradually diminishes as the climate warms. The Hadley circulation generally widens as the climate warms, but at a modest rate that depends sensitively on how it is determined.

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