Abstract
Climate modeling of an AMOC tilt equivalent to the Heinrich 1 event indicates a characteristic spatial distribution of surface temperature changes, with cooling centered on the North Atlantic and widespread, albeit moderate, warming in the middle and high latitudes of the Southern Hemisphere. Some simulations also suggest a warming of subsurface water masses in the North Atlantic.
Sedimentary records indicate that the Tardiglacial climate reversals, Heinrich 1 and Recent Dryas, are part of a succession of rapid instabilities typical of glacial periods. Several causes have been proposed to explain the Heinrich events characterized by iceberg breakup in the North Atlantic : external forcing, free oscillations of an ice cap, feedback from ice caps in response to oceanic and hydrological disturbances.
In detail, sedimentary records demonstrate the complexity of these abrupt events. For example, the Heinrich event 1 is made up of two successive phases, the dating and origin of which are still the subject of intense research. Mineralogical and geochemical indicators suggest different origins for the icebergs (Laurentian or Fennoscandian ice caps). Some studies also point to a delay in the flow of icebergs in relation to thermal reversal. This possible phase lag implies that the Heinrich 1 event is not the cause of widespread cooling, but a feedback amplifying the climate shift phenomenon.
Comprehensive modeling of the phenomenon requires an interactive three-dimensional representation of the couplings between the ocean, ice caps, ice shelves and pack ice. This representation must be sufficiently detailed to take into account the geothermal flow under the ice cap, the geometry of the contact between ice and bedrock, particularly at the level of the contact with seawater (grounding line), and the isostatic readjustment during deglaciation. The first comprehensive modelling attempts have identified possible mechanisms to explain the different phases observed, although there is as yet no agreement on the importance and exact role of the iceberg break-up phase.
