LabexMER lecture
Axe 2
Lundi 26 janvier
11 h - AMPHI A
Strong sensitivity of Southern Ocean carbon uptake and nutrient
cycling to wind stirring
Keith RODGERS
Atmospheric and Oceanic sciences, Université de Princeton, USA.
An ocean biogeochemistry model (NEMO-PISCES) is used to test the hypothesis
that surface winds play an important role in determining the rate of exchange of
CO2 between the atmosphere and the ocean through wind stirring over the
Southern Ocean.
This is considered through the application of an ad hoc parameterization of wind
stirring. It is found that wind stirring leads to reduced uptake of CO2 by the
Southern Ocean over the period 2000-2006, with a relative reduction with wind
stirring on the order of 0.9 PgC/yr over the region south of 45S. This impacts not
only the mean carbon uptake, but also the phasing of the seasonal cycle of carbon
and other ocean biogeochemical tracers. Enhanced wind stirring delays the
seasonal onset of stratification, and thishas large impacts on both entrainment
and the biological pump. It is also found that there is a strong reduction of order
25-30% in the concentration of NO3 exported in Subantarctic Mode Water
(SAMW) to wind stirring. Preliminary Lagrangian analysis will be presented of
the pathways of injection of NO3 into the low-latitude thermocline from the
Southern Ocean, illustrating the importance of both Subtropical and Subantarctic
Mode waters for the injection process.