TRR 181 Seminar "Transit Time Distributions and ventilation pathways in the South Atlantic of an eddying ocean model" by Manita Chouksey (Universität Hamburg)

The TRR 181 seminar is held by Manita Chouksey (Universität Hamburg) on July 8, 11am.

Transit Time Distributions and ventilation pathways in the South Atlantic of an eddying ocean model

Abstract:

Transit Time Distributions (TTDs) for the Antarctic Intermediate Water (AAIW) in the South Atlantic are estimated from an eddying ocean model using interannually varying surface forcing. The TTDs are inferred both from Lagrangian particle backtracking and the modelled concentrations of the anthropogenic tracer CFC-11, under the assumption that the TTDs can be described with an inverse Gaussian function.

A bimodal distribution is obtained for the Lagrangian TTDs, and four major subduction regions are identified: near the Agulhas retroflection, south of New Zealand, west of Drake Passage, and east of Brazil in the Argentine basin, where the latter contributes with the largest mean age and the region west of Drake Passage with the smallest. The inverse Gaussian is a reasonable representation for the TTDs for the AAIW in the east-Atlantic basin, while the fit for regions west of the mid-Atlantic is relatively poor and overestimates the probability density distributions for transit times<15 years.
Mean ages inferred from the model's CFC-11 concentrations are mostly larger than the Lagrangian mean ages (up to 12 years) in the eastern Atlantic, while the tracer-based TTDs are mostly smaller than the Lagrangian TTDs in the western Atlantic. Both methods yield mean ages smaller in the western than in the eastern Atlantic and an aging of AAIW from the 1990's to the 2000's consistent with reduced flow velocities.