On the North Atlantic Ocean Heat Content Change between 1955–70 and 1980–95

Abstract

The upper-ocean heat content of the North Atlantic has undergone significant changes over the last 50 years but the underlying physical mechanisms are not yet well understood. In the present study, the authors examine the North Atlantic ocean heat content change in the upper 700 m between the 1955-70 and 1980-95 periods. Consistent with previous studies, the large-scale pattern consists of warming of the tropics and subtropics and cooling of the subpolar ocean. However, this study finds that the most significant heat content change in the North Atlantic during these two time periods is the warming of the Gulf Stream region. Numerical experiments strongly suggest that this warming in the Gulf Stream region is largely driven by changes of the large-scale wind forcing. Furthermore, the increased ocean heat content in the Gulf Stream region appears to feedback on to the atmosphere, resulting in warmer surface air temperature and enhanced precipitation there.

Northern North Atlantic sea surface height and ocean heat content variability

“…[11] A similar pattern to OHC EOF2 is also seen by Zhai and Sheldon [2012] with simple difference maps for 0 to 700 m Atlantic OHC between 1955-1970 and 1980-1995. They associate these with wind stress variability, and its impact on the Sverdrup transport and lateral heat advection in the Gulf Stream/North Atlantic Current system, similar to the conclusions of H€ akkinen and Rhines [2009] and H€ akkinen et al [2011a]. Their (1 resolution) numerical model study shows increases in Gulf Stream transport and subpolar gyre transport during the above time interval (a period of increasing NAO index), with only localized effects of air/sea heat flux variability.…”

“…A similar pattern to OHC EOF2 is also seen by Zhai and Sheldon [] with simple difference maps for 0 to 700 m Atlantic OHC between 1955–1970 and 1980–1995. They associate these with wind stress variability, and its impact on the Sverdrup transport and lateral heat advection in the Gulf Stream/North Atlantic Current system, similar to the conclusions of Häkkinen and Rhines [] and Häkkinen et al .…”

Intensified impact of tropical Atlantic SST on the western North Pacific summer climate under a weakened Atlantic thermohaline circulation

“…The fluctuation of AMO can arise through the variation of Atlantic thermohaline circulation (THC; e.g., Delworth and Mann 2000;Curry et al 2003;Zhai and Sheldon 2012), although there is also evidence that changes in natural (e.g. volcanic) or anthropogenic (aerosols) external forcing can exert an important influence (e.g., Ottera et al 2010;Booth et al 2012;Zhang et al 2013).…”

Heaving modes in the world oceans

“…Thus, the simple ocean model used in our study may be able to catch the major part of the consequence induced by wind stress anomaly. The impact of thermohaline forcing anomaly on the thermohaline circulation was studied by many investigators, e.g., Johnson and Marshall (2002a, b), Zhai and Sheldon (2012), Zhai et al (2013); however, this is not our focus in this study.…”