scholarly journals Modulation of Monsoon Circulations by Cross-Equatorial Ocean Heat Transport

2019 ◽  
Vol 32 (12) ◽  
pp. 3471-3485 ◽  
Author(s):  
Nicholas J. Lutsko ◽  
John Marshall ◽  
Brian Green
Keyword(s):  
Heat Transport ◽  
Vertical Wind Shear ◽  
Atmospheric Model ◽  
Mean Value ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Transport ◽  
Meridional Overturning ◽  
Static Energy ◽  
Monsoon Winds

Abstract Motivated by observations of southward ocean heat transport (OHT) in the northern Indian Ocean during summer, the role of the ocean in modulating monsoon circulations is explored by coupling an atmospheric model to a slab ocean with an interactive representation of OHT and an idealized subtropical continent. Southward OHT by the cross-equatorial cells is caused by Ekman flow driven by southwesterly monsoon winds in the summer months, cooling sea surface temperatures (SSTs) south of the continent. This increases the reversed meridional surface gradient of moist static energy, shifting the precipitation maximum over the land and strengthening the monsoonal circulation, in the sense of enhancing the vertical wind shear. However, the atmosphere’s cross-equatorial meridional overturning circulation is also weakened by the presence of southward OHT, as the atmosphere is required to transport less energy across the equator. The sensitivity of these effects to varying the strength of the OHT, fixing the OHT at its annual-mean value, and to removing the land is explored. Comparisons with more realistic models suggest that the idealized model used in this study produces a reasonable representation of the effect of OHT on SSTs equatorward of subtropical continents, and hence can be used to study the role of OHT in shaping monsoon circulations on Earth.

scholarly journals On the Relationship between Decadal Buoyancy Anomalies and Variability of the Atlantic Meridional Overturning Circulation

2012 ◽  
Vol 25 (23) ◽  
pp. 8009-8030 ◽  
Author(s):  
Martha W. Buckley ◽  
David Ferreira ◽  
Jean-Michel Campin ◽  
John Marshall ◽  
Ross Tulloch
Keyword(s):  
Climate Variability ◽  
Heat Transport ◽  
Time Scales ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Western Boundary ◽  
Subpolar Gyre ◽  
Ocean Heat Transport ◽  
Meridional Overturning

Abstract Owing to the role of the Atlantic meridional overturning circulation (AMOC) in ocean heat transport, AMOC variability is thought to play a role in climate variability on a wide range of time scales. This paper focuses on the potential role of the AMOC in climate variability on decadal time scales. Coupled and ocean-only general circulation models run in idealized geometries are utilized to study the relationships between decadal AMOC and buoyancy variability and determine whether the AMOC plays an active role in setting sea surface temperature on decadal time scales. Decadal AMOC variability is related to changes in the buoyancy field along the western boundary according to the thermal wind relation. Buoyancy anomalies originate in the upper ocean of the subpolar gyre and travel westward as baroclinic Rossby waves. When the buoyancy anomalies strike the western boundary, they are advected southward by the deep western boundary current, leading to latitudinally coherent AMOC variability. The AMOC is observed to respond passively to decadal buoyancy anomalies: although variability of the AMOC leads to meridional ocean heat transport anomalies, these transports are not responsible for creating the buoyancy anomalies in the subpolar gyre that drive AMOC variability.

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.

Ocean Heat Transport’s Response to Future Climate Projections

2021 ◽  
Author(s):  
Jennifer Mecking ◽  
Sybren Drijfhout
Keyword(s):  
Heat Transport ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Future Climate ◽  
Pacific Basin ◽  
Climate Projections ◽  
Ocean Heat Transport ◽  
Atlantic Basin ◽  
Meridional Overturning ◽  
Future Climate Projections

<p>This study investigates the response of the meridional Ocean Heat Transports (OHT) to future climate projections in both CMIP5 and CMIP6 models.  Globally the OHT transport is declining/becoming more southward across all latitudes in the Northern Hemisphere, while at latitudes south of 10°S the OHT is icreasing/becoming more northward.  These changes in OHT are much stronger in CMIP6 models relative to CMIP5, especially for the rcp2.6/ssp126 scenario relative to the rcp85/ssp585 scenario.   Throughout the entire Atlantic basin the northward heat transport is reduced and can be tied to the velocity driven overturning (Atlantic Meridional Overturning Circulation (AMOC)) contribution to the OHT.  While the temperature driven changes in the Atlantic basin dampen the changes in the OHT.  In the Indo-Pacific basin the OHT transport north of the equator does not change much since the temperature and velocity driven changes balance each other.   However, south of the equator the increase in northward heat transport is caused by the overturning velocity driven changes and again dampened by temperature driven changes.  These changes in the Indo-Pacific basin can be tied to changes in wind driven subtropical overturning cells.</p>

scholarly journals Impact of a 30% reduction in Atlantic meridional overturning during 2009–2010

Ocean Science ◽  
2014 ◽  
Vol 10 (4) ◽  
pp. 683-691 ◽  
Author(s):  
H. L. Bryden ◽  
B. A. King ◽  
G. D. McCarthy ◽  
E. L. McDonagh
Keyword(s):  
Heat Transport ◽  
Meridional Overturning Circulation ◽  
Radiation Budget ◽  
Upper Ocean ◽  
Ocean Heat Transport ◽  
The North ◽  
Hurricane Season ◽  
Meridional Overturning ◽  
North And South ◽  
Earth’S Radiation Budget

Abstract. The Atlantic meridional overturning circulation comprises warm upper waters flowing northward, becoming colder and denser until they form deep water in the Labrador and Nordic Seas that then returns southward through the North and South Atlantic. The ocean heat transport associated with this circulation is 1.3 PW, accounting for 25% of the maximum combined atmosphere–ocean heat transport necessary to balance the Earth's radiation budget. We have been monitoring the circulation at 25° N since 2004. A 30% slowdown in the circulation for 14 months during 2009–2010 reduced northward ocean heat transport across 25° N by 0.4 PW and resulted in colder upper ocean waters north of 25° N and warmer waters south of 25° N. The spatial pattern of upper ocean temperature anomalies helped push the wintertime circulation 2010–2011 into record-low negative NAO (North Atlantic Oscillation) conditions with accompanying severe winter conditions over northwestern Europe. The warmer temperatures south of 25° N contributed to the high intensity hurricane season in summer 2010.

scholarly journals Mid-Pliocene Atlantic Meridional Overturning Circulation simulated in PlioMIP2

2020 ◽  
Author(s):  
Zhongshi Zhang ◽  
Xiangyu Li ◽  
Chuncheng Guo ◽  
Odd Helge Otterå ◽  
Kerim H. Nisancioglu ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Heat Transport ◽  
North Atlantic ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Transport ◽  
Surface Warming ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic

Abstract. In the Pliocene Model Intercomparison Project phase 2 (PlioMIP2), coupled climate models have been used to simulate an interglacial climate during the mid-Piacenzian warm period (mPWP, 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), poleward ocean heat transport and sea surface warming in the Atlantic simulated with these models. In PlioMIP2, all models simulate an intensified mid-Pliocene AMOC. However, there is no consistent response in the simulated Atlantic ocean heat transport, or the depth of the Atlantic overturning cell. The models show a large spread in the simulated AMOC maximum, the Atlantic ocean heat transport, as well as the surface warming in the North Atlantic. Although a few models simulate a surface warming of ~ 8–12 ° in the North Atlantic, similar to the reconstruction from Pliocene Research, Interpretation and Synoptic Mapping (PRISM), most models underestimate this warming. The large model-spread and model-data discrepancies in the PlioMIP2 ensemble does not support the hypothesis that an intensification of the AMOC, together with an increase in northward ocean heat transport, is the dominant forcing for the mid-Pliocene warm climate.

scholarly journals Mid-Pliocene Atlantic Meridional Overturning Circulation simulated in PlioMIP2

2021 ◽  
Vol 17 (1) ◽  
pp. 529-543
Author(s):  
Zhongshi Zhang ◽  
Xiangyu Li ◽  
Chuncheng Guo ◽  
Odd Helge Otterå ◽  
Kerim H. Nisancioglu ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Heat Transport ◽  
North Atlantic ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Transport ◽  
Surface Warming ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic

Abstract. In the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2), coupled climate models have been used to simulate an interglacial climate during the mid-Piacenzian warm period (mPWP; 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), poleward ocean heat transport and sea surface warming in the Atlantic simulated with these models. In PlioMIP2, all models simulate an intensified mid-Pliocene AMOC. However, there is no consistent response in the simulated Atlantic ocean heat transport nor in the depth of the Atlantic overturning cell. The models show a large spread in the simulated AMOC maximum, the Atlantic ocean heat transport and the surface warming in the North Atlantic. Although a few models simulate a surface warming of ∼ 8–12 ∘C in the North Atlantic, similar to the reconstruction from Pliocene Research, Interpretation and Synoptic Mapping (PRISM) version 4, most models appear to underestimate this warming. The large model spread and model–data discrepancies in the PlioMIP2 ensemble do not support the hypothesis that an intensification of the AMOC, together with an increase in northward ocean heat transport, is the dominant mechanism for the mid-Pliocene warm climate over the North Atlantic.

scholarly journals Impact of a 30% reduction in Atlantic meridional overturning during 2009–2010

2014 ◽  
Vol 11 (2) ◽  
pp. 789-810 ◽  
Author(s):  
H. L. Bryden ◽  
B. A. King ◽  
G. D. McCarthy ◽  
E. L. McDonagh
Keyword(s):  
Heat Transport ◽  
Meridional Overturning Circulation ◽  
Radiation Budget ◽  
Upper Ocean ◽  
Ocean Heat Transport ◽  
The North ◽  
Hurricane Season ◽  
Meridional Overturning ◽  
North And South ◽  
Earth’S Radiation Budget

Abstract. The Atlantic meridional overturning circulation comprises warm upper waters flowing northward, becoming colder and denser until they form deep water in the Labrador and Nordic Seas that then returns southward through the North and South Atlantic. The ocean heat transport associated with this circulation is 1.3 PW, accounting for 25% of the maximum combined atmosphere–ocean heat transport necessary to balance the earth's radiation budget. We have been monitoring the circulation at 25° N since 2004. A 30% slowdown in the circulation for 15 months during 2009–2010 reduced northward ocean heat transport across 25° N by 0.4 PW and resulted in colder upper ocean waters north of 25° N and warmer waters south of 25° N. The spatial pattern of upper ocean temperature anomalies helped push the wintertime circulation 2010–2011 into record-low negative NAO conditions with accompanying severe winter conditions over northwestern Europe. The warmer temperatures south of 25° N contributed to the high intensity hurricane season in Summer 2010.

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
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