Rapid and slow communication of overturning changes over the North Atlantic
Abstract
Changes in buoyancy forcing at high latitudes induce changes in overturning, which are communicated over a basin through wave propagation and advection along the western boundary; see Johnson and Marshall (2002) for an idealised study. This communication process is explored here using an isopycnic model (MICOM) integrated over realistic topography and driven by annual mean wind stress and buoyancy forcing. A transient model tracer is released in Labrador Sea in order to monitor the deep advection after the climatological mean state has been reached. A twin experiment is conducted during the last 10 years of integration with either unchanged or increased buoyancy forcing. An increased dense water formation in the high latitudes leads to a pressure signal rapidly propagating along the western slope with a timescale of several weeks. There is a subsequent intermediate response along the western boundary involving local advective changes induced by the wave propagation, occurring on timescales of months to a few years. Eventually, there is a slower far-field, advective response as marked by the arrival of a transient tracer from the source region with a timescale of typically several years. These different mechanisms by which overturning changes are communicated need to be taken into account in the design of the emerging monitoring programmes for the North Atlantic.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....9987R