FN Archimer Export Format
PT J
TI On the mechanism of centennial thermohaline oscillations
BT 
AF SEVELLEC, Florian
   HUCK, Thierry
   JELLOUL MAHDI, Ben
AS 1:;2:;3:;
FF 1:;2:;3:;
TC 0
UR https://archimer.ifremer.fr/doc/2006/publication-6335.pdf
LA English
DT Article
AB Centennial oscillations of the ocean thermohaline circulation are studied in a 2-D latitude-depth model under mixed boundary conditions (i.e. restoring surface temperature and prescribed freshwater flux). The oscillations are revealed through linear stability analysis of a steady state obtained in a single hemisphere configuration. A density variance budget is performed and helps determine the physical processes sustaining these oscillations: the restoring surface temperature appears as a source of density variance - this is a consequence of positively-correlated temperature and salinity anomalies. A minimal model, the Howard-Malkus loop oscillator, enables us to understand physically the oscillatory and growth mechanisms. The centennial oscillation is connected to the advection of salinity anomaly around the loop; it is also related to the salinity feedback on the overturning which reinforces anomalies through a change of residence time in the freshwater flux regions. Analytical solutions of this loop model show that these centennial oscillations exist in a specific parameter regime in terms of the freshwater flux amplitude F0: oscillations are damped if F0 is too weak, but if F0 is too large, the instability grows exponentially without oscillating-the latter regime is known as the positive salinity feedback. The robustness of these oscillations is then analyzed in more realistic bihemispheric configurations, some including a highly idealized Antarctic Circumpolar Current: oscillations are then always damped. These results are rationalized with the loop model, and compared to the oscillations found in general circulation models.
PY 2006
PD MAY
SO Journal of Marine Research
PU Yale University
VL 64
IS 3
BP 355
EP 392
DI 10.1357/002224006778189608
ID 6335
ER

EF