hide
Free keywords:
-
Abstract:
We attribute and describe the governing mechanisms of decadal cold
excursions in the subpolar North Atlantic of similar amplitude and
duration to cold events reconstructed from climate-proxies during the
last millennium detected in an ensemble of three transient and one
unperturbed climate simulation. The cold events are attributed to
internal regional climate variability, with varying external forcing
increasing their magnitude and frequency. The underlying general
mechanism consists of a feedback loop initiated by a weakening of the
North Atlantic subpolar gyre, which induces persistent colder and
fresher surface conditions in the Labrador Sea and, eventually, a deep
convection shutdown. We thus exclude a hemispheric climate
reorganization or a weak ocean overturning circulation as necessary
trigger for such events. An associated northeastward atmospheric cold
advection over the Labrador Sea deteriorates local living conditions on
south Greenland, essential for the sustainability of the Norse
settlements.
