Effects of reduced vertical mixing under sea ice on Atlantic meridional overturning circulation (AMOC) in a global ice-ocean model

2015 ◽  
Vol 50 (2) ◽  
pp. 155-161 ◽  
Author(s):  
Sang Yeob Kim ◽  
Ho Jin Lee ◽  
Jae-Hun Park ◽  
Young Ho Kim
Keyword(s):  
Sea Ice ◽  
Vertical Mixing ◽  
Atlantic Meridional Overturning Circulation ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
Meridional Overturning

scholarly journals Changes in extreme regional sea surface height due to an abrupt weakening of the Atlantic meridional overturning circulation

Ocean Science ◽  
2014 ◽  
Vol 10 (6) ◽  
pp. 881-891 ◽  
Author(s):  
S.-E. Brunnabend ◽  
H. A. Dijkstra ◽  
M. A. Kliphuis ◽  
B. van Werkhoven ◽  
H. E. Bal ◽  
...  
Keyword(s):  
North Atlantic ◽  
Atlantic Meridional Overturning Circulation ◽  
Sea Surface Height ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Sea Level Changes ◽  
Overturning Circulation ◽  
The North ◽  
Meridional Overturning

Abstract. As an extreme scenario of dynamical sea level changes, regional sea surface height (SSH) changes that occur in the North Atlantic due to an abrupt weakening of the Atlantic meridional overturning circulation (AMOC) are simulated. Two versions of the same ocean-only model are used to study the effect of ocean model resolution on these SSH changes: a high-resolution (HR) strongly eddying version and a low-resolution (LR) version in which the effect of eddies is parameterised. The weakening of the AMOC is induced in both model versions by applying strong freshwater perturbations around Greenland. A rapid decrease of the AMOC in the HR version induces much shorter return times of several specific regional and coastal extremes in North Atlantic SSH than in the LR version. This effect is caused by a change in main eddy pathways associated with a change in separation latitude of the Gulf Stream.

scholarly journals Impacts of three types of solar geoengineering on the North Atlantic Meridional Overturning Circulation

2021 ◽  
Author(s):  
Mengdie Xie ◽  
John C. Moore ◽  
Liyun Zhao ◽  
Michael Wolovick ◽  
Helene Muri
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Atlantic Meridional Overturning Circulation ◽  
Arctic Sea Ice ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
The North ◽  
Solar Geoengineering ◽  
Meridional Overturning ◽  
The North Atlantic

Abstract. Climate models simulate lower rates of North Atlantic heat transport under greenhouse gas climates than at present due to a reduction in the strength of the North Atlantic meridional overturning circulation (AMOC). Solar geoengineering whereby surface temperatures are cooled by reduction of incoming shortwave radiation may be expected to ameliorate this effect. We investigate this using six Earth System Models running scenarios from GeoMIP (Geoengineering model intercomparison project) in the cases of: i) reduction in the solar constant, mimicking dimming of the sun; ii) sulfate aerosol injection into the lower equatorial stratosphere; and iii) brightening of the ocean regions mimicking enhancing tropospheric cloud amounts. We find that despite across model differences, AMOC decreases are attributable to reduced air-ocean temperature differences, and reduced September Arctic sea ice extent, with no significant impact from changing surface winds or precipitation-evaporation. Reversing the surface freshening of the North Atlantic overturning regions caused by decreased summer sea ice sea helps to promote AMOC. Comparing the geoengineering types after normalizing them for the differences in top of atmosphere radiative forcing, we find that solar dimming is more effective than either marine cloud brightening or stratospheric aerosol injection.

Effect of Atlantic Meridional Overturning Circulation on Tropical Atlantic Variability: A Regional Coupled Model Study

2011 ◽  
Vol 24 (13) ◽  
pp. 3323-3343 ◽  
Author(s):  
Caihong Wen ◽  
Ping Chang ◽  
Ramalingam Saravanan
Keyword(s):  
Atlantic Meridional Overturning Circulation ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
System Response ◽  
Tropical Atlantic ◽  
Gulf Of Guinea ◽  
Overturning Circulation ◽  
Atmospheric Processes ◽  
Tropical Atlantic Variability ◽  
Meridional Overturning

Abstract A simplified coupled ocean–atmosphere model, where an atmospheric general circulation model (AGCM) is fully coupled to a 2½-layer reduced-gravity ocean model (RGO) over the tropical Atlantic basin, is presented in the context of studying the role of the Atlantic meridional overturning circulation (AMOC) in tropical Atlantic variability (TAV). In the ocean model, the strength of the AMOC is controlled by specifying mass transport at open boundaries. The fidelity of the reduced-physics model in capturing major features of tropical Atlantic variability, as well as its response to the AMOC changes, is demonstrated in a series of model experiments. The results of the experiments reveal the relative importance of oceanic processes and atmospheric processes in AMOC-induced tropical Atlantic variability–change. It is found that the oceanic processes are a primary factor contributing to the warming at and south of the equator and the precipitation increase over the Gulf of Guinea, while atmospheric processes are responsible for the surface cooling of the tropical North Atlantic and southward displacement of ITCZ. A systematic investigation of the coupled system response to changes in AMOC strength indicates that the SST over the cold-tongue region responds nonlinearly to AMOC changes. The sensitivity of the SST response increases rapidly when AMOC strength decreases below a threshold value. Such nonlinear behavior is also found in precipitation response over the Gulf of Guinea. These results suggest that complex and competing atmosphere–ocean processes are involved in TAV response to AMOC changes and the nature of the response can vary from one region to another. This complexity should be taken into consideration in Atlantic abrupt climate studies.

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