Oceans meridional

Processes not resolved in MPI-MCTM that also might serve as explanations for discrepancies between model results and observations are degradation of DDT in the ocean and degradation of DDT in the particle-bound state in air. Furthermore, the neglection of sea-ice had been shown to increase the northern hemisphere meridional DDT gradient [Guglielmo (2008)]. 

The latitudinal heat gradient in the atmosphere and ocean remains relatively constant over time despite the short-term and spatial variations in insolation. This steady state is maintained by the net transport of heat from low to high latitudes where it is radiated back into space. Atmospheric currents (winds) are responsible for about half of this meridional net transport of heat. The rest is accomplished by water movement in the... 

In the open ocean, surfece water salinities exhibit meridional gradients largely controlled by the local balance between water loss through evaporation and water gain through... 

The meridional variations in evaporation and precipitation rates that control surface salinity in the open ocean are shown in Figure 4.9. These variations are caused... 

In the open ocean, the major advective water motion is associated with the surfece-water geostrophic currents and meridional overturning circulation. These flow paths are shown in Figures 4.4b and 4.6. Advection is much fester than molecular diffusion and turbulence. This enables water masses to retain their original temperatures and salinities as they are advected away from their sites of formation. Slow turbulent mixing with adjacent water masses eventually alters this temperatme and salinity signal beyond... 

North Atlantic to 500 m in the North Pacific. This reflects an increasing addition of CO2 to deep waters as meridional overturning circulation moves them from the Atlantic to the Indian and then to the Pacific Ocean. Thus, as a water mass ages, it becomes more corrosive to calcium carbonate. Since aragonite is more soluble than calcite, its saturation horizon lies at shallower depths, rising from 3000 m in the North Atlantic to 200 m in the North Pacific. 

The initial decrease in ocean uptake rate will eventually be reversed once enough time has passed (millennia) for meridional overturning circulation to recycle the subsurface waters. This will serve to inject CO2 below the mixed layer. Once the surface waters have been sufficiently acidified and are transported into the deep sea, they will eventually start dissolving sedimentary calcium carbonate. The resupply of alkalinity via this route will provide sufficient enhancement to ocean carbon uptake capacity to... 

This is a matter of considerable controversy given the current lack of consensus on the importance of winds and tidally driven internal waves in driving meridional overturning circulation. Nevertheless, evidence for changes in circulation have been construed from a freshening of low-latitude surfece seawater in the Atlantic Ocean and a slowdown in NADW formation between 1998 and 2004. 

Cyclical phenomena, such as ENSO events, the North Atlantic Oscillation, the North Pacific Oscillation, and a phenomenon in the Southern Ocean called the Southern Annular Mode, have important impacts on the solubility pump. This was illustrated for the ENSO events in Figure 25.5b. These oscillations are all sensitive to global climate change. In the case of the Southern Ocean, the impact of climate change on circulation is complicated by the zonation associated with the polar and subpolar frontal boundaries (Figure 10.10). As a result, some parts of the Southern Ocean are expected to respond differently than others to changes in increases and meridional overturning circulation rates. 

Injection of compressed CO2 into the deep ocean has already been tested. The goal of this approach is to emplace the CO2 into waters with low temperatures, ensuring the formation of relatively immobile gas hydrates. This strategy has the potential to sequester thousands of gigatonnes of carbon, but likely environmental impacts include (1) a change in the pH in the seawater near the emplaced gas hydrates, (2) benthic kills, (3) other ecosystem impacts, and (4) release back to the atmosphere as an eventual consequence of meridional overturning circulation. 

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