Paris, EU-THOR, Nov25-26, 2009

Response of the North Atlantic Circulation to the realistic and

anomalous wind stress

Yongqi Gao , Helge Drange, Mats Bentsen and Jan Even Nilsen

Nansen-Zhu International Research Centre, IAP/CAS, ChinaNansen Environmental and Remote Sensing Center, Norway

Bjerknes Centre for Climate Research, Norway

Paris, EU-THOR, Nov25-26, 2009

Micom

Miami Isopycnic Coordinate Ocean Model (Bleck et al., 1992)

Mixed layer+Isopycnic layers belowGlobal domain with sea ice module

Paris, EU-THOR, Nov25-26, 2009

Experimental Design

Spin-up time 180 yrs;W0, 1948-2004, three cycles;

W1/2, 1948-2004, three cycles;

W1, 1948-2004, three cycles;

W2, 1948-2004, three cycles;

Gao et al., updating, 2009

Paris, EU-THOR, Nov25-26, 2009

AMOC and Normalized AMOC

W2

W1

W1/2

W0

Paris, EU-THOR, Nov25-26, 2009

Simulated and Data-estimated Meridional Heat Transport

Obs (red line):Trenberth and Caron (2001)

W2

W1/2

W0

W1

Paris, EU-THOR, Nov25-26, 2009

Simulated Maximum Mixed Layer Depth

W0 W1/2

W1W2

Paris, EU-THOR, Nov25-26, 2009

Simulated Isopycnal Volume Transport at 24oN

W0 W1/2

W1W2

Paris, EU-THOR, Nov25-26, 2009

Paris, EU-THOR, Nov25-26, 2009

Simulated Isopycnal Volume Transport at Section ABD

W0 W1/2

W1W2

Paris, EU-THOR, Nov25-26, 2009

Mean Volume Transport at Northern Atlantic

W0 W1/2

W1W2

Paris, EU-THOR, Nov25-26, 2009

Mean Dense Water Volume Transport at Northern Atlantic

W0 W1/2

W1W2

Paris, EU-THOR, Nov25-26, 2009

Dense Water Formation Rate in the Irminger Sea basin And Normalized AMOC in W1 (red) and W0 (blue)

Paris, EU-THOR, Nov25-26, 2009

Paris, EU-THOR, Nov25-26, 2009

Simulated Dense Water Volume Transport through Sections

W0 W1/2

W1W2

24oN

AB

Paris, EU-THOR, Nov25-26, 2009

Subpolar Gyre Index

Obs (blue line): Hatun et al. 2005

W0

W2

W1/2

Paris, EU-THOR, Nov25-26, 2009

Summing up

AMOC is sensitive to the strength of the wind stress Wind stress is responsible for the short-term

variabilities in the simulated AMOC Long-term increasing trend in the simulated AMOC is

mainly governed by the thermohaline forcing Realistic wind stress can lift the AMOC in the

subtropical North Atlantic by 7.3 Sv Subpolar Gyre Index can be used as an potential

indicator of the AMOC