Reduced North Atlantic Central Water formation in response to early Holocene ice?sheet melting

Central waters of the North Atlantic are fundamental for ventilation of the upper ocean and are also linked to the strength of the Atlantic Meridional Overturning Circulation (AMOC). Here, we show based on benthic foraminiferal Mg/Ca ratios, that during times of enhanced melting from the Laurentide...

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Bibliographic Details
Published in:Geophysical Research Letters
Main Authors: Bamberg, Audrey, Rosenthal, Y, Paul, A, Heslop, David, Mulitza, Stefan, Rühlemann, Carsten, Schulz, Michael
Format: Article in Journal/Newspaper
Language:unknown
Published: American Geophysical Union
Subjects:
Keywords: Atlantic meridional overturning circulations
Data sets
Freshwater fluxes
Greenland Ice Sheet
Holocenes
Laurentide ice sheets
North Atlantic
Northern Hemispheres
Possible futures
Subpolar gyres
Upper ocean
Water convection
Water formation
Glac
Greenland
Ice Sheet
Online Access:http://hdl.handle.net/1885/28041
https://doi.org/10.1029/2010GL043878
https://openresearch-repository.anu.edu.au/bitstream/1885/28041/5/Bamberg_Rosenthal_Paul_Heslop_et_al_2010.pdf.jpg
https://openresearch-repository.anu.edu.au/bitstream/1885/28041/7/01_Bamberg_Reduced_North_Atlantic_Central_2010.pdf.jpg
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Summary:Central waters of the North Atlantic are fundamental for ventilation of the upper ocean and are also linked to the strength of the Atlantic Meridional Overturning Circulation (AMOC). Here, we show based on benthic foraminiferal Mg/Ca ratios, that during times of enhanced melting from the Laurentide Ice Sheet (LIS) between 9.0-8.5 thousand years before present (ka) the production of central waters weakened the upper AMOC resulting in a cooling over the Northern Hemisphere. Centered at 8.54 0.2 ka and 8.24 0.1 ka our dataset records two ∼150-year cooling events in response to the drainage of Lake Agassiz/Ojibway, indicating early slow-down of the upper AMOC in response to the initial freshwater flux into the subpolar gyre (SPG) followed by a more severe weakening of both the upper and lower branches of the AMOC at 8.2 ka. These results highlight the sensitivity of regional North Atlantic climate change to the strength of central-water overturning and exemplify the impact of both gradual and abrupt freshwater fluxes on eastern SPG surface water convection. In light of the possible future increase in Greenland Ice Sheet melting due to global warming these findings may help us to better constrain and possibly predict future North Atlantic climate change.

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