Holocene Oscillations in Temperature and Salinity of the Subpolar North Atlantic: Underlying Mechanisms and Their Link to North Pacific Climate (Invited)
Abstract
The North Atlantic region has been subject to millennial scale fluctuations in climate throughout the Holocene, including periods associated with southward advances of sea-ice and reduced deep ocean flow strength. Historical records suggest these changes caused socio-economic changes in human civilisations in the circum-North Atlantic region. However the underlying mechanism(s) behind these changes remains uncertain. Paired Mg/Ca-δ18O records from two depth-zoned planktic foraminifera have been used to reconstruct the temperature and salinity of the North Atlantic surface waters that feed the deep convection sites of the Nordic Seas - the Atlantic Inflow [Thornalley, Elderfield & McCave, Nature, 2009]. Large amplitude millennial scale (~1500 year) changes in the temperature and salinity of the Atlantic Inflow are likely driven by changes in the strength of the subpolar gyre, consistent with modern decadal scale mechanisms. Changes in the strength of the North Atlantic subpolar gyre are likely caused by early Holocene deglacial melt water input and changes in atmospheric circulation (meridional versus zonal flow over the North Atlantic), both of which alter the freshwater balance of the subpolar gyre. Implied weakening of the North Atlantic subpolar gyre occurs during periods of previously reported global rapid climate change. Furthermore, Greenland ice core records and emerging North Pacific climate records also document atmospheric circulation changes during these intervals, and it appears that switching between different modes of circulation, combined with modulation by ocean circulation, has likely driven widespread Holocene climate oscillations. Yet the role that an external trigger such as solar output variability played in these changes remains unclear.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMPP12C..08T
- Keywords:
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- 4901 PALEOCEANOGRAPHY / Abrupt/rapid climate change;
- 4936 PALEOCEANOGRAPHY / Interglacial;
- 4954 PALEOCEANOGRAPHY / Sea surface temperature