Dynamics and variability of transports in the Nordic Seas overflows
The dense overflows across the Greenland Scotland Ridge are an important contribution to the deep branch of the Atlantic Meridional Overturning Circulation. The dynamics of the overflows has been extensively studied in the last 50 years, and revealed the importance of hydraulic control mechanisms and downstream entrainment for the formation of the later North Atlantic Deep Water. Climate-variability related interannual transport changes, however, have not been observed before long-term measurements by moored instruments set off in the 1990s. Time series of the last decade indicate, that the overflows may react both on dense water reservoir height changes, and NAO-related wind stress changes. Here, the observations of the Denmark Strait and Faroe Bank Channel overflow dynamics and transport are reviewed. Together with the less-well observed smaller overflows between Iceland and Scotland, the total dense water export from the Nordic Seas and its interannual variability is quantified.