Major Reorganization of the North Atlantic Oscillation during early Holocene deglaciation
Abstract
Recent observations show that the Greenland Ice Sheet (GIS) melts. However, the climatic consequences and in particular its effect on the North Atlantic Oscillation (NAO) remains unclear. The Early Holocene is characterized by deglaciation processes, e.g. the remnant Laurentide Ice Sheet (LIS) and its melting and might provide an analogue to the melting of the GIS today. This study integrates new proxy climate data from a NW Moroccan (a key NAO region) speleothem that covers the Early to Late Holocene and results from the state-of-the-art earth-system-model COSMOS to study the variability of the NAO and its forcing mechanisms through the Holocene. Nowadays, the NAO leads to a negative correlation between precipitation in NW Morocco and W Germany. Based on a comparison of the Moroccan and a German proxy record, a positive correlation is observed during the Early Holocene. This correlation shift is examined by climate simulations of the Early (9 ka BP, including LIS and its melting), mid (6 ka BP) and Late Holocene (pre-industrial conditions). The influence of the LIS and its melt water contribution lead to a strong non-linear cooling of surface air temperatures during deglaciation. This synergetic influence of the LIS strengthens the melting effect on ocean circulation during the Early Holocene, which affects the Atlantic Meridional Overturning Circulation and sea-surface temperatures, which in turn may affect sea-level pressure and, eventually, the AO/NAO. Our climate simulations suggest that this reflects a major atmospheric and oceanic reorganization in response to changes in ice-sheet configuration and deglacial melt-water flux. In summary, synergetic effects of deglaciation explain the in-phase rainfall relationship between Morocco and Germany during the Early Holocene that does not account for recent climate conditions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMPP54A..04D
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSESDE: 1616 Climate variability;
- GLOBAL CHANGEDE: 1627 Coupled models of the climate system;
- GLOBAL CHANGEDE: 4904 Atmospheric transport and circulation;
- PALEOCEANOGRAPHY