Major salinity-induced reorganizations of the
global conveyor belt circulation 17,500-15,000
years ago.
Axel Timmermann, Yusuke Okazaki, Laurie Menviel,
Naomi Harada, Ayako Abe-Ouchi
Laurie Menviel, Anne Mouchet
Heinrich I: The Atlantic Meridional Overturning Circulation
Heinrich events were triggered by massive iceberg surges into the North Atlantic
Ice-rafted
detritus
What triggered Heinrich event I?
Did the AMOC shut down?
What were the global impacts?
Weaker AMOC
McManus et al., 2004
North Pacific salinity response to AMOC shutdown
Closed Bering Strait
SSS CCSM2
SSS LOVECLIM
SST CCSM2
SST LOVECLIM
Aleutian Low Response to tropical Atlantic SST
CAM2
DJF
6 hPa
DJF SST, SLP, precipitation anomalies
Okumura et al., J. Climate (2008)
Effects on North Pacific Convection: LOVECLIM
AMOC on
AMOC off
Due to the cold and saline conditions in the North Pacific during the shutdown
phase of the AMOC, deep convection occurs in wintertime in the Bering Sea
and the Gulf of Alaska.
Can the deepwater formed north of Aleutian escape into North Pacific ?
Connection between Bering Sea and North Pacific
Deep water
formation
Kamchatka Strait
3000m
Surface Salinity changes
Density-driven salinity
transport: Stommel
SSSA, and current anomaly
During Heinrich event
Governing factors for Pacific Salinity
Kiefer, Science 2010
Sea surface temperature changes: the PMOC – a backup
generator during deglaciation
Density driven heat
transport
SSTA, and current anomaly
During Heinrich event
PMOC, ventilation
d14C
PMOC+ O2
DWBC
Surface
d14C
2000-3000m
PMOC evidence: compilation of radiocarbon data
Schematics
Summary
• Compelling Model and data evidence for
PDWF during Heinrich I
• Salinity increase in NPAC due to changes
in freshwater export, reduction of
monsoons and Stommel feedback
• PMOC has a global effect on climate and
stabilizes the AMOC off state (maybe
relevant for other paleo-climate eras)