TY - JOUR
T1 - Solar modulation of North Atlantic central Water formation at multidecadal timescales during the late Holocene
AU - Morley, Audrey
AU - Schulz, Michael
AU - Rosenthal, Yair
AU - Mulitza, Stefan
AU - Paul, André
AU - Rühlemann, Carsten
N1 - Funding Information:
We thank M. Segl for stable isotope analyses and at the University of Bremen. We would also like to thank T. Babila and the trace metal geochemistry lab crew at IMCS, Rutgers University as well as Helge Meggers, Nikesh Narayan at the University of Bremen for advice and analytical support, the editor and an anonymous reviewer for thoughtful discussions and comments. The research was funded by the Deutsche Forschungsgemeinschaft INTERDYNAMIC DFG‐Schwerpunktprogramm 1266 to AB, AP, SM, CR and MS.
PY - 2011/8/1
Y1 - 2011/8/1
N2 - Understanding natural climate variability in the North Atlantic region is essential not only to assess the sensitivity of atmosphere-ocean climate signal exchange and propagation, but also to help distinguish between natural and anthropogenic climate change. The North Atlantic Oscillation is one of the controlling modes in recent variability of atmosphere-ocean linkages and ice/freshwater fluxes between the Polar and North Atlantic Ocean. Through these processes the NAO influences water mass formation and the strength of the Atlantic Meridional Overturning circulation and thereby variability in ocean heat transport. However, the impact of the NAO as well as other forcing mechanisms on multidecadal timescales such as total solar irradiance on Eastern North Atlantic Central Water production, central water circulation, and climate signal propagation from high to low latitudes in the eastern subpolar and subtropical basins remains uncertain. Here we use a 1200yr long benthic foraminiferal Mg/Ca based temperature and oxygen isotope record from a ~900m deep sediment core off northwest Africa to show that atmosphere-ocean interactions in the eastern subpolar gyre are transferred at central water depth into the eastern boundary of the subtropical gyre. Further we link the variability of the NAO (over the past 165yrs) and solar irradiance (Late Holocene) and their control on subpolar mode water formation to the multidecadal variability observed at mid-depth in the eastern subtropical gyre. Our results show that eastern North Atlantic central waters cooled by up to ~0.8±0.7°C and densities decreased by σθ=0.3±0.2 during positive NAO years and during minima in solar irradiance during the Late Holocene. The presented records demonstrate the sensitivity of central water formation to enhanced atmospheric forcing and ice/freshwater fluxes into the eastern subpolar gyre and the importance of central water circulation for cross-gyre climate signal propagation during the Late Holocene.
AB - Understanding natural climate variability in the North Atlantic region is essential not only to assess the sensitivity of atmosphere-ocean climate signal exchange and propagation, but also to help distinguish between natural and anthropogenic climate change. The North Atlantic Oscillation is one of the controlling modes in recent variability of atmosphere-ocean linkages and ice/freshwater fluxes between the Polar and North Atlantic Ocean. Through these processes the NAO influences water mass formation and the strength of the Atlantic Meridional Overturning circulation and thereby variability in ocean heat transport. However, the impact of the NAO as well as other forcing mechanisms on multidecadal timescales such as total solar irradiance on Eastern North Atlantic Central Water production, central water circulation, and climate signal propagation from high to low latitudes in the eastern subpolar and subtropical basins remains uncertain. Here we use a 1200yr long benthic foraminiferal Mg/Ca based temperature and oxygen isotope record from a ~900m deep sediment core off northwest Africa to show that atmosphere-ocean interactions in the eastern subpolar gyre are transferred at central water depth into the eastern boundary of the subtropical gyre. Further we link the variability of the NAO (over the past 165yrs) and solar irradiance (Late Holocene) and their control on subpolar mode water formation to the multidecadal variability observed at mid-depth in the eastern subtropical gyre. Our results show that eastern North Atlantic central waters cooled by up to ~0.8±0.7°C and densities decreased by σθ=0.3±0.2 during positive NAO years and during minima in solar irradiance during the Late Holocene. The presented records demonstrate the sensitivity of central water formation to enhanced atmospheric forcing and ice/freshwater fluxes into the eastern subpolar gyre and the importance of central water circulation for cross-gyre climate signal propagation during the Late Holocene.
KW - Benthic Mg/Ca paleothermometry
KW - Climate signal transfer
KW - Late Holocene
KW - NAO
KW - North Atlantic central water formation
KW - Solar minima - LIA
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U2 - 10.1016/j.epsl.2011.05.043
DO - 10.1016/j.epsl.2011.05.043
M3 - Article
AN - SCOPUS:79960053028
SN - 0012-821X
VL - 308
SP - 161
EP - 171
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
IS - 1-2
ER -