2015a: CMIP5 climate change global deep waters

C. Heuzé, K.J. Heywood, D.P. Stevens and J.K. Ridley (2015), “Changes in global ocean bottom properties and volume transports in CMIP5 models under climate change scenarios“, Journal of Climate, vol 28, pp 2917-2944, doi:10.1175/JCLI-D-14-00381.1

Assessment of global bottom water property changes (2081:2100 – 1986:2005) for 25 CMIP5 models.
We found that in the Southern Hemisphere, warming/decrease in density first reaches the bottom of the ocean thanks to open ocean deep convection, and is then advected equatorwards by AABW transports.
In turn, the decrease in density causes a weakening of the AABW transport into each basin.
In the North Atlantic, less NADW is being formed because of a strong decrease in deep convection, allowing intrusions of AABW up to the Labrador Sea.
Bottom property changes contribute significantly to steric sea level rise, but bottom water formation and transport need to be better resolved in models to reduce the spread in sea level rise projection.

From Fig A2: Annual mean for 2006–2100, in RCP8.5 (red) and the preindustrial control (black), of the bottom potential temperature in the Atlantic between 80 and 60S in three models.

The appendix presents a comparison for three models between their drift and the climate change signal. It proves that the climate change values discussed in the paper are significant, but also that removing the models’ drift is necessary.

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