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Internally generated decadal cold events in the northern North Atlantic and their possible implications for the demise of the Norse settlements in Greenland
Author(s) -
MorenoChamarro Eduardo,
Zanchettin Davide,
Lohmann Katja,
Jungclaus Johann H.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl062741
Subject(s) - ocean gyre , climatology , north atlantic deep water , north atlantic oscillation , oceanography , thermohaline circulation , geology , demise , forcing (mathematics) , atlantic multidecadal oscillation , advection , climate change , gulf stream , subtropics , political science , law , physics , fishery , biology , thermodynamics
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.