Implied ocean heat transport in CMIP6 models

2021 ◽  
Author(s):  
Francesca Pearce ◽  
Alejandro Bodas-Salcedo ◽  
Christopher Thomas ◽  
Thomas Allen
Keyword(s):  
Heat Transport ◽  
Energy Budget ◽  
Climate Models ◽  
Surface Fluxes ◽  
Radiative Energy ◽  
Ocean Heat Transport ◽  
Energy Fluxes ◽  
Data Set ◽  
Ocean Heat Uptake ◽  
Energy Convergence

<p>The importance of heat transport in the ocean to maintain energy balance between different regions is well known, with heat typically being transported from the Equator to high latitudes. Ocean heat transport (OHT) can be separated into two different components; a divergent component which contributes directly to the Earths’ energy budget as it is the energy that converges in an ocean basin to balance the release of heat into the atmosphere, and a rotational component which does not affect the energy budget. Climate models show significant uncertainty in projections of ocean heat uptake, both in terms of the magnitude and geographical pattern. Since the oceans’ response under climate changes depends on the patterns of surface energy fluxes, it is important to assess the simulation of surface fluxes as a potential constraint of transient and long-term responses of the Earths’ climate. Assuming that the ocean absorbs all of the excess energy within the Earth system, it is possible to directly relate the net surface flux (NSF) over the ocean to divergent OHT, potentially providing a metric to quantify how well climate models are able to reproduce observed patterns of NSF and OHT. In this work, we present a detailed comparison of different methods used to calculate divergent OHT from the NSF over the ocean using data from various CMIP6 models. The methods investigated include a least-squares solution to a matrix equation in which energy convergence is related to NSF via the Earths’ energy imbalance, and solving a Poisson equation over the ocean surface (see Forget and Ferreira 2020). Comparison to observational estimates of OHT requires that the observational data set includes only sources of divergent heat transport, which is often not the case. Therefore, we intend to produce a data set of radiative energy fluxes that are consistent with both energy and water constraints (see Rodell et al. 2015, L’Ecuyer et al. 2015, Thomas et al. 2020) which can be subject to the same methods of determining OHT, and see how these estimates compare to the results from climate models.</p>

scholarly journals Different mechanisms of Arctic and Antarctic sea ice response to ocean heat transport

2022 ◽  
Author(s):  
Jake Aylmer ◽  
David Ferreira ◽  
Daniel Feltham
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Climate Models ◽  
Heat Fluxes ◽  
Substantial Contribution ◽  
Climate Projections ◽  
Ocean Heat Transport ◽  
Antarctic Sea Ice ◽  
The Impact ◽  
Energy Convergence

AbstractUnderstanding drivers of Arctic and Antarctic sea ice on multidecadal timescales is key to reducing uncertainties in long-term climate projections. Here we investigate the impact of ocean heat transport (OHT) on sea ice, using pre-industrial control simulations of 20 models participating in the latest Coupled Model Intercomparison Project (CMIP6). In all models and in both hemispheres, sea ice extent is negatively correlated with poleward OHT. However, the similarity of the correlations in both hemispheres hides radically different underlying mechanisms. In the northern hemisphere, positive OHT anomalies primarily result in increased ocean heat convergence along the Atlantic sea ice edge, where most of the ice loss occurs. Such strong, localised heat fluxes ($$\sim {}100~\text {W}~\text {m}^{-2}$$ ∼ 100 W m - 2 ) also drive increased atmospheric moist-static energy convergence at higher latitudes, resulting in a pan-Arctic reduction in sea ice thickness. In the southern hemisphere, increased OHT is released relatively uniformly under the Antarctic ice pack, so that associated sea ice loss is driven by basal melt with no direct atmospheric role. These results are qualitatively robust across models and strengthen the case for a substantial contribution of ocean forcing to sea ice uncertainty, and biases relative to observations, in climate models.

scholarly journals Different Mechanisms of Arctic and Antarctic Sea Ice Response to Ocean Heat Transport

2021 ◽  
Author(s):  
Jake Robert Aylmer ◽  
David Ferreira ◽  
Daniel Feltham
Keyword(s):  
Sea Ice ◽  
Heat Transport ◽  
Climate Models ◽  
Heat Fluxes ◽  
Substantial Contribution ◽  
Climate Projections ◽  
Ocean Heat Transport ◽  
Antarctic Sea Ice ◽  
The Impact ◽  
Energy Convergence

Abstract Understanding drivers of Arctic and Antarctic sea ice on multidecadal timescales is key to reducing uncertainties in long-term climate projections. Here we investigate the impact of Ocean Heat Transport (OHT) on sea ice, using pre-industrial control simulations of 20 models participating in the latest Coupled Model Intercomparison Project (CMIP6). In all models and in both hemispheres, sea ice extent is negatively correlated with poleward OHT. However, the similarity of the correlations in both hemispheres hides radically different underlying mechanisms. In the northern hemisphere, positive OHT anomalies primarily result in increased ocean heat convergence along the Atlantic sea ice edge, where most of the ice loss occurs. Such strong, localised heat fluxes (~100 W m − 2 ) also drive increased atmospheric moist-static energy convergence at higher latitudes, resulting in a pan-Arctic reduction in sea ice thickness. In the southern hemisphere, increased OHT is released relatively uniformly under the Antarctic ice pack, so that associated sea ice loss is driven by basal melt with no direct atmospheric role. These results are qualitatively robust across models and strengthen the case for a substantial contribution of ocean forcing to sea ice uncertainty, and biases relative to observations, in climate models.

scholarly journals Southern Ocean Heat Uptake, Redistribution, and Storage in a Warming Climate: The Role of Meridional Overturning Circulation

2018 ◽  
Vol 31 (12) ◽  
pp. 4727-4743 ◽  
Author(s):  
Wei Liu ◽  
Jian Lu ◽  
Shang-Ping Xie ◽  
Alexey Fedorov
Keyword(s):  
Southern Ocean ◽  
Heat Transport ◽  
Climate Models ◽  
Climate Model ◽  
Meridional Overturning Circulation ◽  
The Other ◽  
Anthropogenic Heat ◽  
Overturning Circulation ◽  
Ocean Heat Uptake ◽  
Meridional Overturning

Climate models show that most of the anthropogenic heat resulting from increased atmospheric CO2 enters the Southern Ocean near 60°S and is stored around 45°S. This heat is transported to the ocean interior by the meridional overturning circulation (MOC) with wind changes playing an important role in the process. To isolate and quantify the latter effect, we apply an overriding technique to a climate model and decompose the total ocean response to CO2 increase into two major components: one due to wind changes and the other due to direct CO2 effect. We find that the poleward-intensified zonal surface winds tend to shift and strengthen the ocean Deacon cell and hence the residual MOC, leading to anomalous divergence of ocean meridional heat transport around 60°S coupled to a surface heat flux increase. In contrast, at 45°S we see anomalous convergence of ocean heat transport and heat loss at the surface. As a result, the wind-induced ocean heat storage (OHS) peaks at 46°S at a rate of 0.07 ZJ yr−1 (° lat)−1 (1 ZJ = 1021 J), contributing 20% to the total OHS maximum. The direct CO2 effect, on the other hand, very slightly alters the residual MOC but primarily warms the ocean. It induces a small but nonnegligible change in eddy heat transport and causes OHS to peak at 42°S at a rate of 0.30 ZJ yr−1 (° lat)−1, accounting for 80% of the OHS maximum. We also find that the eddy-induced MOC weakens, primarily caused by a buoyancy flux change as a result of the direct CO2 effect, and does not compensate the intensified Deacon cell.

Northern High-Latitude Heat Budget Decomposition and Transient Warming

2013 ◽  
Vol 26 (2) ◽  
pp. 609-621 ◽  
Author(s):  
Maria A. A. Rugenstein ◽  
Michael Winton ◽  
Ronald J. Stouffer ◽  
Stephen M. Griffies ◽  
Robert Hallberg
Keyword(s):  
Heat Transport ◽  
High Latitude ◽  
Climate Models ◽  
Heat Budget ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
Ocean Heat Uptake ◽  
Control Climate ◽  
Wide Range ◽  
Heat Uptake

Abstract Climate models simulate a wide range of climate changes at high northern latitudes in response to increased CO2. They also have substantial disagreement on projected changes of the Atlantic meridional overturning circulation (AMOC). Here, two pairs of closely related climate models are used, with each containing members with large and small AMOC declines to explore the influence of AMOC decline on the high-latitude response to increased CO2. The models with larger AMOC decline have less high-latitude warming and sea ice decline than their small AMOC decline counterpart. By examining differences in the perturbation heat budget of the 40°–90°N region, it is shown that AMOC decline diminishes the warming by weakening poleward ocean heat transport and increasing the ocean heat uptake. The cooling impact of this AMOC-forced surface heat flux perturbation difference is enhanced by shortwave feedback and diminished by longwave feedback and atmospheric heat transport differences. The magnitude of the AMOC decline within model pairs is positively related to the magnitudes of control climate AMOC and Labrador and Nordic Seas convection. Because the 40°–90°N region accounts for up to 40% of the simulated global ocean heat uptake over 100 yr, the process described here influences the global heat uptake efficiency.

scholarly journals Mid-pliocene Atlantic Meridional Overturning Circulation not unlike modern

2013 ◽  
Vol 9 (4) ◽  
pp. 1495-1504 ◽  
Author(s):  
Z.-S. Zhang ◽  
K. H. Nisancioglu ◽  
M. A. Chandler ◽  
A. M. Haywood ◽  
B. L. Otto-Bliesner ◽  
...  
Keyword(s):  
Heat Transport ◽  
Climate Models ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Transport ◽  
Overturning Circulation ◽  
Consistent Change ◽  
Intercomparison Project ◽  
Meridional Overturning ◽  
Consistent Increase

Abstract. In the Pliocene Model Intercomparison Project (PlioMIP), eight state-of-the-art coupled climate models have simulated the mid-Pliocene warm period (mPWP, 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), northward ocean heat transport and ocean stratification simulated with these models. None of the models participating in PlioMIP simulates a strong mid-Pliocene AMOC as suggested by earlier proxy studies. Rather, there is no consistent increase in AMOC maximum among the PlioMIP models. The only consistent change in AMOC is a shoaling of the overturning cell in the Atlantic, and a reduced influence of North Atlantic Deep Water (NADW) at depth in the basin. Furthermore, the simulated mid-Pliocene Atlantic northward heat transport is similar to the pre-industrial. These simulations demonstrate that the reconstructed high-latitude mid-Pliocene warming can not be explained as a direct response to an intensification of AMOC and concomitant increase in northward ocean heat transport by the Atlantic.

scholarly journals Mid-pliocene Atlantic meridional overturning circulation not unlike modern?

2013 ◽  
Vol 9 (2) ◽  
pp. 1297-1319 ◽  
Author(s):  
Z.-S. Zhang ◽  
K. H. Nisancioglu ◽  
M. A. Chandler ◽  
A. M. Haywood ◽  
B. L. Otto-Bliesner ◽  
...  
Keyword(s):  
Heat Transport ◽  
Climate Models ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Transport ◽  
Overturning Circulation ◽  
Consistent Change ◽  
Intercomparison Project ◽  
Meridional Overturning ◽  
Consistent Increase

Abstract. In the Pliocene Model Intercomparison Project (PlioMIP), eight state-of-the-art coupled climate models have simulated the mid-Pliocene warm period (mPWP, 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), northward ocean heat transport and ocean stratification simulated with these models. None of the models participating in the PlioMIP simulates a strong mid-Pliocene AMOC as suggested by earlier proxy studies. Rather, there is no consistent increase in AMOC maximum among the PlioMIP models. The only consistent change in AMOC is a shoaling of the overturning cell in the Atlantic, and a reduced influence of North Atlantic Deep Water (NADW) at depth in the basin. Furthermore, the simulated mid-Pliocene Atlantic northward heat transport is similar to the pre-industrial. These simulations demonstrate that the reconstructed high latitude mid-Pliocene warming can not be explained as a direct response to an intensification of AMOC and concomitant increase in northward ocean heat transport by the Atlantic.

Temporal variability of inferred surface energy fluxes derived from the ERA5 energy budget

2020 ◽  
Author(s):  
Johannes Mayer ◽  
Michael Mayer ◽  
Leopold Haimberger
Keyword(s):  
Surface Energy ◽  
Energy Budget ◽  
Temporal Variability ◽  
Heat Content ◽  
Global Ocean ◽  
High Temporal Resolution ◽  
Energy Fluxes ◽  
Ocean Heat Uptake ◽  
Surface Energy Fluxes ◽  
Global Mean

<p>We use the new Copernicus ERA5 reanalysis dataset to evaluate the global atmospheric energy budget using a consistent diagnostic framework and  improved numerical methods. A main outcome of this work are mass consistent divergences of moist static plus kinetic energy fluxes. These divergences are combined with top-of-the-atmosphere fluxes based on satellite observations and reconstructions back to 1985 to obtain net surface energy fluxes (F<sub>S</sub>) with unprecedented accuracy. The global mean of these F<sub>S</sub> fields is unbiased by construction. Hence, this product is well-suited for climate studies and model evaluations.  Here, the temporal variability and stability of inferred F<sub>S</sub>, the land-ocean energy transport and the corresponding water cycle are presented and compared with previous evaluations, which used ERA-Interim. </p><p>The inferred F<sub>S</sub> fields exhibit a much smaller noise level, and sampling errors are drastically reduced due to the high temporal resolution (hourly) of the ERA5 dataset. Energy budget residuals over land are on the order of 17.0 Wm<sup>-2</sup>, which represents a 63 % reduction compared to ERA-Interim. We also present time series of F<sub>S</sub> averaged over the global ocean. Its global mean is 2.0 Wm<sup>-2</sup>, which is in much better agreement with ocean heat uptake than widely used satellite-derived surface flux products. Moreover, it exhibits reasonable temporal stability at least from 2000 onwards. We compare the annual cycles of F<sub>S</sub> over the ocean and ocean heat content variations derived from ocean reanalysis products and find good agreement. Overall, our results demonstrate clear improvements over earlier evaluations, but more work is needed to optimally use the available data and further reduce uncertainties.</p>

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.

scholarly journals Evidence for atmosphere-ocean meridional energy transport compensation in the past decades

2020 ◽  
Author(s):  
Wilco Hazeleger ◽  
Yang Liu ◽  
Jisk Attema
Keyword(s):  
Heat Transport ◽  
Time Scales ◽  
Climate Models ◽  
Energy Transport ◽  
Climate Modelling ◽  
Ocean Heat Transport ◽  
Ocean Reanalysis ◽  
Modelling Studies ◽  
Almost All ◽  
Atmospheric Heat

<p><span lang="EN-US">We present evidence of compensation between the atmosphere and ocean's meridional energy transport variations, also known as Bjerknes compensation. Motivated by previous studies with mostly numerical climate models, we analyze compensation using a range of atmosphere and ocean reanalysis datasets. We show that Bjerknes compensation is present at almost all latitudes from 40 degrees North to 70 degrees North in the Northern Hemisphere from interannual to decadal time scales. In contrast to results from some numerical climate models, which attribute the compensation to variations of eddy energy transports in the atmosphere in response to changes of ocean heat transport and sea ice at multi-decadal time scales, we find a response of the zonal mean of poleward energy transport to ocean heat transport variability that leads to compensation. This is apparent in a meridional shift of the Ferrel Cell at midlatitudes at decadal time scales in winter. This shift in the cell itself is driven by changes in the eddy momentum flux and related baroclinicity. The oceanic response to atmospheric heat transport variations associated by the shift is primarily wind driven. In summer, there is hardly compensation and the proposed mechanism is not at work. Interestingly, these results are robust among all reanalysis datasets and can provide a benchmark for climate modelling studies.</span></p>

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