Decadal variability of the global ocean carbon sink

This talk focuses on the variations of the ocean CO2 sink during the past
three decades using global surface ocean maps of the partial pressure of
CO2 reconstructed from observations contained in the Surface Ocean CO2
Atlas Version 2. To create these maps for the period from 1982 through
2011, the neural network-based data-interpolation method of  Landschützer
et al. [2014] is employed. The air-sea flux is then estimated from the
difference in partial pressure of CO2 between the ocean and the
atmosphere as well as a bulk paramtrization of the kinematik gas
transfer. The results suggest strong decadal variations in the global
ocean carbon sink, driven by the CO2 partial pressure difference between
atmosphere and ocean, with a minimum uptake of -0.8+-0.5 PgC/yr in 2000,
and a substantial strengthening towards more than -2.0+-0.5 PgC/yr in
2010, around a long-term increase that corresponds roughly to that
expected from the rise in atmospheric CO2. The observed
stagnation/reduction of the oceanic CO2 sink in the 1990s and the
subsequent strengthening of the global CO2 uptake is further reproduced
by a set of complementary mapping methods participating in the SOCOM
project [Rödenbeck et al. 2015]. These decadal variations originate
mostly from the extratropical oceans ­ including a recent strengthening
of the Southern Ocean carbon sink - while the tropical regions contribute
primarily to interannual variations.These decadal variations lead to a
considerably smaller cumulative anthropogenic CO2 uptake of the ocean
over the 1982 through 2011.