The Role of the Ocean in the Seasonal Cycle of the Hadley Circulation

2006 ◽  
Vol 63 (12) ◽  
pp. 3351-3365 ◽  
Author(s):  
Amy C. Clement
Keyword(s):  
Heat Transport ◽  
Seasonal Cycle ◽  
Climate Model ◽  
Hadley Circulation ◽  
Ocean Heat Transport ◽  
Complete Understanding ◽  
Atmospheric Processes ◽  
Summer Hemisphere ◽  
Hadley Cells

The influence of ocean heat transport on the seasonal cycle of the Hadley circulation is investigated using idealized experiments with a climate model. It is found that ocean heat transport plays a fundamental role in setting the structure and intensity of the seasonal Hadley cells. The ocean’s influence can be understood primarily via annual mean considerations. By cooling the equatorial regions and warming the subtropics in a year-round sense, the ocean heat transport allows for regions of SST maxima to occur off the equator in the summer hemisphere. This leads to large meridional excursions of convection over the ocean and a seasonal Hadley circulation that is strongly asymmetric about the equator. The broadening of the latitudinal extent of the SST maximum and the convecting regions by the ocean heat transport also weakens the annual mean Hadley circulation in a manner that is consistent with simpler models. The results are discussed in the context of prior studies of the controls on the strength and structure of the Hadley circulation. It is suggested that a complete understanding of the seasonal Hadley circulation must include both oceanic and atmospheric processes and their interactions.

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 Exploring the Climatic Response to Wide Variations in Ocean Heat Transport on an Aquaplanet

2018 ◽  
Vol 31 (16) ◽  
pp. 6299-6318 ◽  
Author(s):  
M. Cameron Rencurrel ◽  
Brian E. J. Rose
Keyword(s):  
Heat Transport ◽  
Climate Model ◽  
Hadley Circulation ◽  
Balance Model ◽  
Ocean Heat Transport ◽  
Climatic Impact ◽  
Ocean Heat Uptake ◽  
Boundary Layer Clouds ◽  
Radiative Processes ◽  
The Tropics

The climatic impact of ocean heat transport (OHT) is studied in a series of idealized aquaplanet climate model experiments. OHT is prescribed through a simple geometrical formula spanning a wide variety of amplitudes and meridional extents. Calculations with a comprehensive GCM are compared against a simple diffusive energy balance model (EBM). The GCM response differs from the EBM in several important ways that illustrate linkages between atmospheric dynamics and radiative processes. Increased OHT produces global mean warming at a rate of 2 K PW−1 OHT across 30° and a strong reduction in meridional temperature gradient. The tropics remain nearly isothermal despite locally large imposed ocean heat uptake. The warmer climate features reduced equatorial convection, moister subtropics, reduced cloudiness, and partial but incomplete compensation in atmospheric heat transport. Many of these effects are linked to a weakened Hadley circulation. Both the warming pattern and hydrological changes differ strongly from those driven by CO2. Similar results are found at 0° and 23.45° obliquity. It is argued that clouds, rather than clear-sky radiative processes, are principally responsible for the global warming and tropical thermostat effects. Cloud changes produce warming in all cases, but the degree of warming depends strongly on the meridional extent of OHT. The strongest warming occurs in response to mid- to high-latitude OHT convergence, which produces widespread loss of boundary layer clouds. Temperature responses to increased OHT are quantitatively reproduced in the EBM by imposing GCM-derived cloud radiative effects as additional forcing.

The role of ocean heat transport from the Atlantic into the Arctic Ocean on sea ice variability

2021 ◽  
Author(s):  
David Schroeder ◽  
Danny Feltham
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Barents Sea ◽  
System Model ◽  
The Arctic ◽  
Earth System ◽  
Ocean Heat Transport ◽  
Sea Ice Extent ◽  
Atmospheric Processes

<p>The decrease of Arctic sea ice affects the future climate in the Arctic and beyond. Therefore, it is important to understand the drivers of sea ice variability and trend. Previous model studies found that the summer sea ice is mainly driven by atmospheric processes (incoming radiation and albedo feedback) and the winter sea ice extent by ocean processes (ocean heat transport from Atlantic into Arctic Ocean, e.g. applying Community Earth System Model large ensemble simulation). In our study, we analyse a historical simulation with the UK Earth System Model (UKESM1) performed for CMIP6 from 1850 to 2014 and ocean – sea ice simulations forced by atmospheric reanalysis data with the same ocean model NEMOv3.6 and sea ice model CICEv5.1. The UKESM simulation confirms previous findings showing that the ocean heat transport between Norway and Svalbard (Barents Sea Opening; BSO) is strongly correlated with the winter (and annual) sea ice extent in the Barents Sea and the whole Arctic. However, there is no correlation in the atmospheric-forced simulations suggesting that the interaction between atmosphere and ocean is crucial. We will present sensitivity simulations showing the impact of atmospheric forcing data on the BSO heat flux and analyse the role of atmospheric processes (large scale circulation, cloud formation) on winter sea ice conditions.</p>

Past climate and the role of ocean heat transport: Model simulations for the Cretaceous

1993 ◽  
Vol 8 (6) ◽  
pp. 785-798 ◽  
Author(s):  
Eric J. Barron ◽  
William H. Peterson ◽  
David Pollard ◽  
Starley Thompson
Keyword(s):  
Heat Transport ◽  
Transport Model ◽  
Ocean Heat Transport ◽  
Past Climate ◽  
Model Simulations

scholarly journals Oceanic Overturning and Heat Transport: The Role of Background Diffusivity

2019 ◽  
Vol 32 (3) ◽  
pp. 701-716 ◽  
Author(s):  
Magnus Hieronymus ◽  
Jonas Nycander ◽  
Johan Nilsson ◽  
Kristofer Döös ◽  
Robert Hallberg
Keyword(s):  
Heat Transport ◽  
Large Scale ◽  
Energy Transport ◽  
Climate Model ◽  
Potential Temperature ◽  
Meridional Heat Transport ◽  
Sea Ice Extent ◽  
Antarctic Sea Ice ◽  
Meridional Overturning

The role of oceanic background diapycnal diffusion for the equilibrium climate state is investigated in the global coupled climate model CM2G. Special emphasis is put on the oceanic meridional overturning and heat transport. Six runs with the model, differing only by their value of the background diffusivity, are run to steady state and the statistically steady integrations are compared. The diffusivity changes have large-scale impacts on many aspects of the climate system. Two examples are the volume-mean potential temperature, which increases by 3.6°C between the least and most diffusive runs, and the Antarctic sea ice extent, which decreases rapidly as the diffusivity increases. The overturning scaling with diffusivity is found to agree rather well with classical theoretical results for the upper but not for the lower cell. An alternative empirical scaling with the mixing energy is found to give good results for both cells. The oceanic meridional heat transport increases strongly with the diffusivity, an increase that can only partly be explained by increases in the meridional overturning. The increasing poleward oceanic heat transport is accompanied by a decrease in its atmospheric counterpart, which keeps the increase in the planetary energy transport small compared to that in the ocean.

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 Recent Changes in the Annual Mean Regional Hadley Circulation and Their Impacts on South America

2015 ◽  
Vol 2015 ◽  
pp. 1-22 ◽  
Author(s):  
Ana Carolina Vasques Freitas ◽  
Tércio Ambrizzi
Keyword(s):  
South America ◽  
Climate Model ◽  
Regional Climate ◽  
Model Performance ◽  
Hadley Circulation ◽  
Sea Surface ◽  
Westerly Winds ◽  
Positive Correlations ◽  
Poleward Expansion

This work employs the regional climate model RegCM4 and observational datasets to investigate the impacts of changes in the intensity and poleward edge of regional HC over South America (HCSA) on the patterns of wind, geopotential height, precipitation, and temperature during the period 1996–2011. Significant trends of HCSA intensification and poleward expansion are found during the period analyzed. To evaluate the effects of these changes over SA, two composites, representing the intensification and poleward expansion cases, are examined separately. Significant correlations are seen between the temperature, zonal wind, and the HCSA intensity over the northern, central, and southern regions of SA and South Atlantic. Results show that, in both composites, regions with anomalous easterly (westerly) winds coming from (towards) the Atlantic Ocean have negative (positive) correlations with the HCSA intensity and poleward edge. The model performance varies regionally and the southern SA region exhibits better agreement with the observations. The role of the sea surface temperatures in driving the changes in the HCSA is examined. Notable similarity is found in the results for the two cases analyzed, which could indicate that, in most cases, the changes in the intensity and poleward edge of the HCSA are occurring simultaneously.

scholarly journals Influence of tropical cyclones on sea surface temperature seasonal cycle and ocean heat transport

2012 ◽  
Vol 41 (7-8) ◽  
pp. 2019-2038 ◽  
Author(s):  
Emmanuel M. Vincent ◽  
Gurvan Madec ◽  
Matthieu Lengaigne ◽  
Jérôme Vialard ◽  
Ariane Koch-Larrouy
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Heat Transport ◽  
Tropical Cyclones ◽  
Seasonal Cycle ◽  
Sea Surface ◽  
Ocean Heat Transport

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.

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