Atlantic Ocean circulation

The ocean conveyor belt is one of the major elements of today s ocean circulation system (Broecker, 1997). A key feature is that it delivers an enormous amount of heat to the North Atlantic and this has profound implications for past, present, and probably future climates. 

Oceanic circulation. The process of ocean circulation described earlier yields an ocean circulation pattern that results in progressively older deep water as the water passes, in sequence from the Atlantic, Indian, to the Pacific Ocean. Surface water returns relatively quickly to the place of origin for the deep water. 

Haug, G. H. and Tiedemann, R. (1998). Effect of the formation of the Isthmus of Panama on Atlantic Ocean thermohaline circulation. Nature, 393, 673-676. 

Evaporite deposition is a much more episodic process and thus difficult to quantify. Because seawater is significantly undersaturated with respect to common evaporitic minerals, like gypsum and halite, evaporites are only formed when restricted circulation develops in an ocean basin in which evaporation exceeds precipitation. A geologically recent example is the Mediterranean Sea of 5-6 Myr ago. At this time excess evaporation exceeded the supply of ocean water through shallow inlet(s) from the Atlantic Ocean. As salinity increased, first CaS04, then NaCl precipitated. Over time, salt deposits 2-3 km thick formed. This thickness represents about 40 desiccations of the entire... 

The D-O events are far too rapid to be caused by insolation changes, and they most likely result from changes in ocean circulation. Their prominence and clarity in the Greenland cores relative to the Antarctic ones is due to the proximity of Greenland to the sites of deep-water formation in the North Atlantic and the tremendous amount of heat being delivered to them by the Gulf Stream (Broecker and Denton, 1989). 

The use of ( Paxs/ Thxs) to assess past circulation rates only works well where the residence time of deep waters is low and advection therefore dominates over the removal of Pa by particle scavenging (Yu et al. 2001a). The Atlantic Ocean fits these... 

Distributions of DOC in the deep ocean. The x-axis is viewed in the context of the deep-ocean circulation, with formation in the North Atlantic, circulation around the Southern Ocean, and flow northward into the Indian and Pacific oceans. Source-. From Mansell, D. A. (2002) Biogeochemistry of Marine Dissoived Organic Matter, Academic Press, pp. 685-715. 

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. 

Delaygue et al. (2000) have modeled the present day 0 distribution in the Atlantic and Pacific Ocean and its relationship with salinity (see Fig. 3.19). A good agreement is found between observed and simulated 5 0-values using an oceanic circulation model. As shown in Fig. 3.19 the Atlantic Ocean is enriched by more than 0.5%c relative to the Pacific Ocean, but both ocean basins show the same general patterns with high 0-values in the subtropics and lower values at high latitudes. 

Similar changes are seen in other terrestrial and marine geological records from the North Atlantic region, but not from the Antarctic. Circulation changes in the North Atlantic Ocean are conjectured to be the driving force for the climate changes. 

Boyle E.A. and Keigwin L.D. (1985) Comparison of Atlantic nd Pacific paleochemical records for the last 25,000 years Changes i deep ocean circulation and chemical inventories. Earth and Planet. Sci. at. 76, 135-150. 

The austral wintertime upper-level circulation (Fig. 2.1b) over South America is characterized by weak winds over the tropics, while the subtropical westerly jet is stronger and located more equatorward than in summer, in agreement with the descending branch of the Hadley-type circulation over that area. At lower levels, a northward-displaced near-equatorial low-pressure trough and SST maximum characterize the circulation (Fig. 2. Id). A northward cross-equatorial flow turning clockwise is found over the tropical eastern Pacific and Atlantic Oceans (Fig. 2.1b). 

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