North Atlantic Gyre

Low air temperatures at high latitudes cause substantial sea-air heat flux, driving a density increase and convection in the water column.

Open ocean convection occurs in deep plumes and is particularly strong in winter when the sea-air temperature difference is largest.

This grouping of water-masses then moves geostrophically southward along the East flank of Reykjanes Ridge, through the Charlie Gibbs Fracture Zone and then northward to join DSOW.

[4][5] ISOW is produced in proportion to the density gradient across the Iceland-Scotland Ridge and as such is sensitive to LSW production which affects the downstream density[6][7] More indirectly, increased LSW production is associated with a strengthened SPG and hypothesized to be anti-correlated with ISOW[8][9][10] This interplay confounds any simple extension of a reduction in individual overflow waters to a reduction in AMOC.

LSW production is understood to have been minimal prior to the 8.2 ka event,[11] with the SPG thought to have existed before in a weakened, non-convective state.

[18] Stramma and Siedler (1988) determined that the gyre expands and contracts with a seasonal variance; however, the magnitude of volume transport does not seem to change significantly.

Yet during winter convective mixing, nutrients penetrate the euphotic zone, causing a short-lived phytoplankton bloom in the spring.

The changes in oceanic biology and vertical mixing between winter and summer in the North Atlantic Gyre seasonally alter the total amount of carbon dioxide in the seawater.

Interannual trends have established that carbon dioxide concentrations within this gyre are increasing at a similar rate to that occurring in the atmosphere.

[20] Measured samples of aerosols, marine particles, and water in the gyre from 1990–92 include examining lead isotope ratios.

Certain isotopes are hallmarks of pollution essentially from Europe and the near Middle East by trade winds; other contamination was primarily caused by American emissions.