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WP 1.2: Circulation and Water Mass Changes in the subpolar North Atlantic

PIs:
Monika Rhein, Marum-IUP, Universität Bremen, mrhein(at)physik.uni-bremen.de
Birgit Klein, BSH, Hamburg, birgit.klein(at)bsh.de

Team:
Achim Rößler, MARUM-IUP, Universität Bremen
Christian Mertens, MARUM-IUP, Universität Bremen
Reiner Steinfeldt, MARUM-IUP, Universität Bremen
Dagmar Kieke, MARUM-IUP, Universität Bremen
Wolfgang Böke, MARUM-IUP, Universität Bremen
Manuela Köllner, BSH, Hamburg
Holger Klein, BSH, Hamburg
Anja Schneehorst, BSH, Hamburg
acoustic current meter with buoyancy sphere

Fig.1: An Acoustic Doppler current profiler (ADCP) enclosed in its buoyant protective shell surfaces after 12 months deployment in the western boundary current.

In the first RACE funding phase, the scientific analyses were focused on the western subpolar Atlantic and on the NAC inflow into the eastern basin. From the 100 Sv NAC northward transport at 47°N, only 27 Sv cross the Midatalantic Ridge (MAR) and reach the eastern Atlantic. As a consequence, the northward transport of subtropical water across 47°N in the eastern Atlantic might be more important than previously thought. By extending the moored instruments into the eastern basin at the former WOCE section A2 at nominally 48°N, we will be able to continually measure all important AMOC (Atlantic Meridional Overturning Circulation) components in the western and eastern Atlantic in the transition zone between the subtropical and subpolar circulation. The scientific goals are:
  1. To quantify the exchange between the subtropical and the subpolar gyre in the western and the eastern Atlantic and quantify the main AMOC component at 47°N/48°N
  2. To study the potential relation and relevant processes between the variability in the eastern and western Atlantic and in the spatial and temporal variability of the NAC transport across the MAR
  3. To quantify the fluctuations in the deep water formation in the Labrador Sea and respective changes in the circulation in the western and eastern Atlantic
  4. Study the relation between time series of transport and water mass characteristics from the observations in the subpolar North Atlantic and other RACE key regions
The objectives will be tackled by a joint analysis of observations and high resolution models.
velocity section 47°N

Mooring array along 47°N/48°N. White circles: bottom echo sounders (PIES); white squares: current meters and microcats; orange: ADCÜ longranger. Colors show the northward (blue) and southward (red) velocity from LADCO data between 2003 and 2014; contour intervals 5 cm/s.