A monitoring design for the Atlantic meridional overturning circulation

Joël Hirschi, Johanna Baehr, Jochem Marotzke, John StarkSchool of Earth and Ocean Science, Southampton Oceanography Centre

University of Southampton

MOC in OCCAM (1/4º) and FLAME (1/3º)

Voltage induced in cable proportional to total mass transport

Calibration with Hydrographic sections

Mass transport through the Florida Strait

Ekman transport

Zonal densitydifferences(thermal wind)

zonal wind stress

Ekman transport

Mass transport east of the Florida Strait

Ekman contribution

Mass transport east of the Florida Strait

Thermal wind contributionVertical profiles of density

wind stress

Mass transport east of the Florida Strait

Thermal wind contributionVertical profiles of density

Velocities obtained between adjacent profiles

Total MOC at 26oN

Florida Straittransport

Thermal wind

Total MOC at 26oN

Florida Straittransport

Thermal windEkman

Total MOC at 26oN

Florida Straittransport

Thermal windEkman

Spatially constant correction for the velocity field to ensure the mass balance

OCCAM

FLAME

Placementof densityprofiles

Estimate MOC

MOC at 26oN: maximum transports

OCCAM

FLAME

VerticalMOC structure

MOC at 26oN: vertical structure

Estimate MOC

MOC at 26oN: northward heat transport (NHT)

Estimated NHT Model NHT

OCCAM

FLAME

MOC at 26oN: long-term trend (2-year running mean)

MOC

300 reconstructions with added noise

average of reconstructions

Internal tides: rapid vertical displacement of isopycnals

Conclusions and discussion

Bottom velocities:underestimation of external mode

z

v0 vbReliability of devices

Limitations of thermal wind balance (frictional effects)Bottom pressurerecorder