Vertical Redistribution of Oceanic Heat Content
Xinfeng Liang*, Carl Wunsch, Patrick Heimbach and Gael Forget
* Corresponding author address: Xinfeng Liang, Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139. E-mail:
xliang@mit.edu
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02139Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139.
Journal of Climate
Vol. preprint: Issue. 2015:
DOI: 10.1175/JCLI-D-14-00550.1
Estimated values of recent oceanic heat uptake are of order of a few tenths of a W/m2, and are a very small residual of air-sea exchanges with annual average regional magnitudes of hundreds of W/m2. Using a dynamically consistent state estimate, the redistribution of heat within the ocean is calculated over a 20-year period. The 20-year mean vertical heat flux shows strong variations in both the lateral and vertical directions, consistent with the ocean being a dynamically active and spatially complex heat exchanger. Between mixing and advection, the two processes determining the vertical heat transport in the deep ocean, advection plays a more important role in setting the spatial patterns of vertical heat exchange and its temporal variations.
The global integral of vertical heat flux shows an upward heat transport in the deep ocean, suggesting a cooling trend in the deep ocean. These results support an inference that the near-surface thermal properties of the ocean are a consequence, at least in part, of internal redistributions of heat, some of which must reflect water that has undergone long trajectories since last exposure to the atmosphere. The small residual heat exchange with the atmosphere today is unlikely to represent the interaction with an ocean that was in thermal equilibrium at the start of global warming. An analogy is drawn with carbon-14 “reservoir ages” which range over hundreds to a thousand years.