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 events were triggered by massive iceberg surges into the North Atlantic McManus et al., 2004 Weaker AMOC Heinrich I: The Atlantic Meridional Overturning Circulation What triggered Heinrich event I? Did the AMOC shut down? What were the global impacts? Ice-rafted detritus

SSS LOVECLIM SST LOVECLIM SST CCSM2 SSS CCSM2 North Pacific salinity response to AMOC shutdown Closed Bering Strait

DJF SST, SLP, precipitation anomalies DJF Aleutian Low Response to tropical Atlantic SST Okumura et al., J. Climate (2008) 6 hPa CAM2

Effects on North Pacific Convection: LOVECLIM 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 ? 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 ? AMOC on AMOC off

Connection between Bering Sea and North Pacific Kamchatka Strait 3000m Deep water formation

Surface Salinity changes SSSA, and current anomaly During Heinrich event Density-driven salinity transport: Stommel

Governing factors for Pacific Salinity Kiefer, Science 2010

Sea surface temperature changes: the PMOC – a backup generator during deglaciation SSTA, and current anomaly During Heinrich event Density driven heat transport

PMOC, ventilation DWBC Surface m PMOC+ O 2  14 C

PMOC evidence: compilation of radiocarbon data

Schematics

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) Summary