The global meridional circulation, the transformation of surface waters into deep waters in limited areas and the presumed broad upwelling of deep waters throughout much of the rest of the ocean, is extremely sensitive to climate changes. The deepest waters originate principally in the Weddell Sea and in the Nordic Sea, in both cases as dense water overflows. The Nordic Seas overflow is replaced by warm water flowing north, principally between Shetland, the Faroes and Iceland, a flow of exceptional importance for the mild climate enjoyed by central and northern Europe.
It is proposed to establish a program to monitor the exchange of waters between the North Atlantic and the Nordic Seas across the Shetland- Faroe-Iceland ridge. The Scotland-Faroe-Iceland ridge is the natural chokepoint for monitoring the strength of the MOC.
A ferry, the Norrona, operated out of the Faroes, maintains year-round weekly service to Iceland and to northern Denmark. The ferry also stops in the Shetland and in Norway. Thus the vessel traverses all north-flowing warm water between Iceland and Scotland weekly. We propose to equip the vessel with an acoustic Doppler current profiler (ADCP) to measure currents as it operates between these ports.
Repeat sampling of currents allows for accurate estimates of transport, and hence allow to discern trends in transport. The high-resolution horizontal sampling allows detailed studies of the spatial and dynamical properties of the currents crossing the ridge.
This program is designed to address growing societal concerns in the US and Europe about the stability of warm water transport to high latitudes. Displays of the data gathering system will be maintained onboard for public view and education.
