AOML
NOAA

National Oceanic and Atmospheric Administration

Atlantic Oceanographic and Meteorological Laboratory

Physical Oceanography Division

A Fingerprint for the AMOC: Multidecadal Ocean Temperature Variability in the Tropical North Atlantic

by Chunzai Wang and Liping Zhang

In an article recently accepted for publication by the Journal of Climate, PHOD scientists show that the variation of surface and subsurface ocean temperatures in the tropical North Atlantic (TNA) is important to and linked with the Atlantic meridional overturning circulation (AMOC). Results presented here suggest that the subsurface ocean temperature variation in the TNA can be taken as a fingerprint for the AMOC variability, and it also has an important implication for interpreting hurricane acticity in terms of multidecadal ocean temperature variation in the TNA.

In an article accepted for publication by Journal of Climate, scientists at AOML/PHOD show that the variation of surface and subsurface ocean temperatures in the tropical North Atlantic (TNA) is important to and linked with the Atlantic meridional overturning circulation (AMOC). The Atlantic multidecadal oscillation (AMO) is characterized by the sea surface warming (cooling) of the entire North Atlantic during its warm (cold) phase. Both observations and most of IPCC-AR5 climate models also show that the warm (cold) phase of the AMO is associated with a surface warming (cooling) and a subsurface cooling (warming) in the TNA Ocean. It is further shown that the warm phase of the AMO corresponds to a strengthening of the AMOC and a weakening of the Atlantic subtropical cell (STC), both of which induce an anomalous northward current in the TNA subsurface ocean. Because the mean meridional temperature gradient of the subsurface ocean is positive due to the temperature dome around 9oN, the advection by the anomalous northward current cools the TNA subsurface ocean during the warm phase of the AMO. The opposite is true during the cold phase of the AMO. It is concluded that the anticorrelated ocean temperature variation in the TNA associated with the AMO is caused by the meridional current variation induced by variability of the AMOC and STC, but the AMOC plays a more important role than the STC. The paper suggests that the subsurface ocean temperature variation in the TNA can be taken as a fingerprint for AMOC variability, and it also has an important implication for interpreting hurricane activity in terms of the multidecadal ocean temperature variation in the TNA.


Figure. Schematic diagram showing the variations of the Atlantic meridional overturning circulation, subtropical cell, ocean temperature and surface wind with the Atlantic multidecadal oscillation on multidecadal timescales.

Wang, C., and L. Zhang, 2013. Multidecadal ocean temperature and salinity variability in the tropical North Atlantic: Linking with the AMO, AMOC and subtropical cell. J. Climate, in press.