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1. Introduction Is the ocean circulation thermally or mechanically forced? Already a century ago, Sandström (1908) concluded from his laboratory experiments that the heating and cooling at the ocean surface by itself would not be able to excite a circulation in the interior of the ocean. His arguments were elaborated by Jeffreys (1925) and Defant (1961) , who concluded that the circulation must be mechanically forced. Nevertheless, for a long time, a widespread view among oceanographers
1. Introduction Is the ocean circulation thermally or mechanically forced? Already a century ago, Sandström (1908) concluded from his laboratory experiments that the heating and cooling at the ocean surface by itself would not be able to excite a circulation in the interior of the ocean. His arguments were elaborated by Jeffreys (1925) and Defant (1961) , who concluded that the circulation must be mechanically forced. Nevertheless, for a long time, a widespread view among oceanographers
1. Introduction The global ocean overturning circulation is a key element of Earth’s climate system and the ocean biogeochemical cycles through its transport of heat, carbon, and nutrients both across latitudes and from one ocean basin to another through the Southern Ocean. Most idealized models and theories of the overturning circulation focus on the zonally averaged transports and ignore the zonal transports. Here we extend those models to capture the zonal interbasin exchanges through the
1. Introduction The global ocean overturning circulation is a key element of Earth’s climate system and the ocean biogeochemical cycles through its transport of heat, carbon, and nutrients both across latitudes and from one ocean basin to another through the Southern Ocean. Most idealized models and theories of the overturning circulation focus on the zonally averaged transports and ignore the zonal transports. Here we extend those models to capture the zonal interbasin exchanges through the
relative roles of mean ocean circulation and ocean circulation change in the uptake and storage of heat in the Southern Ocean remain controversial. For example, using an ocean-only model forced with a spatially uniform surface flux, Marshall et al. (2015) and Armour et al. (2016) found that the climatological meridional overturning circulation of the Southern Ocean controls the response patterns of ocean heat uptake and storage, while the changes in ocean circulation play a secondary role. Several
relative roles of mean ocean circulation and ocean circulation change in the uptake and storage of heat in the Southern Ocean remain controversial. For example, using an ocean-only model forced with a spatially uniform surface flux, Marshall et al. (2015) and Armour et al. (2016) found that the climatological meridional overturning circulation of the Southern Ocean controls the response patterns of ocean heat uptake and storage, while the changes in ocean circulation play a secondary role. Several
1. Introduction The oceanic thermohaline circulation and the global atmospheric circulation are generally analyzed as two separate systems although they influence each other through the surface of the ocean. In the present work both are represented in thermodynamic coordinates and linked to each other. We analyze and visualize how the ocean and atmosphere are closely acting together as a number of overturning cells, expressing the mixing of air and water masses. To do so we use two recently
1. Introduction The oceanic thermohaline circulation and the global atmospheric circulation are generally analyzed as two separate systems although they influence each other through the surface of the ocean. In the present work both are represented in thermodynamic coordinates and linked to each other. We analyze and visualize how the ocean and atmosphere are closely acting together as a number of overturning cells, expressing the mixing of air and water masses. To do so we use two recently
1. Introduction This paper tries to make progress in the problem of understanding the deep stratification and associated overturning circulation in the ocean. In addition to being a fundamental aspect of the Earth’s ocean the deep structure is of direct importance to the climate system; however, compared to some other aspects of the large-scale ocean circulation, it has been inadequately studied and is rather poorly understood. Here, we present a simple theoretical model (or theory, for short
1. Introduction This paper tries to make progress in the problem of understanding the deep stratification and associated overturning circulation in the ocean. In addition to being a fundamental aspect of the Earth’s ocean the deep structure is of direct importance to the climate system; however, compared to some other aspects of the large-scale ocean circulation, it has been inadequately studied and is rather poorly understood. Here, we present a simple theoretical model (or theory, for short
sinking water masses through the overturning circulation. As a result, the formation of deep water plays an important role in setting the ocean heat content and heat transport. In addition, during the transformation of surface water into dense sinking water, heat is released into the atmosphere, warming the surface climate at high latitudes (e.g., Winton 2003 ; Frierson et al. 2013 ). Changes in circulation, including the convection, are an important factor in the projection of transient warming
sinking water masses through the overturning circulation. As a result, the formation of deep water plays an important role in setting the ocean heat content and heat transport. In addition, during the transformation of surface water into dense sinking water, heat is released into the atmosphere, warming the surface climate at high latitudes (e.g., Winton 2003 ; Frierson et al. 2013 ). Changes in circulation, including the convection, are an important factor in the projection of transient warming
hydrographic sections, Sato and Rossby (1995) estimated that the decrease in the baroclinic transport was 6 Sv for the same period of time, and they found that their best sample pentads were within 4 Sv of each other. Curry and McCartney (2001) gave observational evidence that the interannual-to-interdecadal variability of the intensity of the North Atlantic gyre circulation largely reflected the integral response of the ocean to the NAO forcing in the subtropical and subpolar gyres, but the
hydrographic sections, Sato and Rossby (1995) estimated that the decrease in the baroclinic transport was 6 Sv for the same period of time, and they found that their best sample pentads were within 4 Sv of each other. Curry and McCartney (2001) gave observational evidence that the interannual-to-interdecadal variability of the intensity of the North Atlantic gyre circulation largely reflected the integral response of the ocean to the NAO forcing in the subtropical and subpolar gyres, but the
1. Introduction The large-scale global ocean circulation is driven by winds, tidal forces, and density mixing induced to a large extent by the breaking of internal gravity waves. In addition to the omnipresent internal wave field, geostrophically balanced energetic mesoscale eddies are present in the ocean and they mix properties along rather than across isopycnals [see, e.g., McDougall et al. (2017) for a recent discussion of this issue]. The eddy-induced isopycnal mixing becomes most
1. Introduction The large-scale global ocean circulation is driven by winds, tidal forces, and density mixing induced to a large extent by the breaking of internal gravity waves. In addition to the omnipresent internal wave field, geostrophically balanced energetic mesoscale eddies are present in the ocean and they mix properties along rather than across isopycnals [see, e.g., McDougall et al. (2017) for a recent discussion of this issue]. The eddy-induced isopycnal mixing becomes most
1. Introduction The World Ocean thermohaline circulation is frequently idealized as a conveyor belt transporting heat and freshwater from the Indo–Pacific to the Atlantic ( Broecker 1987 ). This interocean exchange of heat and freshwater, closely associated with the formation of North Atlantic Deep Water (NADW), is of key importance for the climatic and hydrographic differences between the North Atlantic and the North Pacific. It should be noted, however, that the freshwater transport into the
1. Introduction The World Ocean thermohaline circulation is frequently idealized as a conveyor belt transporting heat and freshwater from the Indo–Pacific to the Atlantic ( Broecker 1987 ). This interocean exchange of heat and freshwater, closely associated with the formation of North Atlantic Deep Water (NADW), is of key importance for the climatic and hydrographic differences between the North Atlantic and the North Pacific. It should be noted, however, that the freshwater transport into the
1. Introduction Present Arctic Ocean near-surface circulation is commonly characterized as being in an anticyclonic phase ( Hofmann et al. 2015 ; McPhee et al. 2009 ; Proshutinsky et al. 2015 , 2009 ). This idea is largely based on in situ observations in the Canada Basin that are biased toward measuring the intensity of the anticyclonic Beaufort Gyre and on a regional index of Arctic Ocean circulation, the Arctic Ocean Oscillation index (AOOI). The AOOI is the sea surface height gradient
1. Introduction Present Arctic Ocean near-surface circulation is commonly characterized as being in an anticyclonic phase ( Hofmann et al. 2015 ; McPhee et al. 2009 ; Proshutinsky et al. 2015 , 2009 ). This idea is largely based on in situ observations in the Canada Basin that are biased toward measuring the intensity of the anticyclonic Beaufort Gyre and on a regional index of Arctic Ocean circulation, the Arctic Ocean Oscillation index (AOOI). The AOOI is the sea surface height gradient
