WOCE AIMS: Analysis of Tracer Ages and Estimate of Isopycnal Mixing

University Of Miami, Coral Gables FL

Investigators

Abstract

0136973 Fine The goal of this project to estimate the uncertainties for individual tracer ages, and to associate differences in the magnitude of these uncertainties with known circulation phenomena. The focus is on thermocline and intermediate water masses, using World Ocean Circulation Experiment (WOCE) chlorofluorocarbon and tritium/helium-3 data that have recently become available. Tracer ages are a measure of the ocean's ability to transport atmospheric constituents into the interior. Isopycnal mixing rates will be calculated for regions of the subtropical gyres where isopycnal mixing can significantly alter tracer ages. Errors in tracer ages arise from analytical, source function, and other factors. Here a differentiation will be made between errors in tracer ages and distributions. The effect of errors on tracer age distributions is small compared with effects of oceanic processes. Depending on the extent and pathways of mixing, a tracer can exhibit a broad distribution of ages within a given water mass. Mixing, therefore, compromises the ability to interpret tracer ages; i.e., the elapsed time since a water parcel was in contact with the atmosphere. Mixing histories will be assessed by analyzing distributions of tracer ages with an accepted theoretical framework. Isopycnal mixing rates and Peclet numbers will be calculated for sub-regions of the subtropical gyres. These values will be compared to tracer age distributions and non-linear mixing terms. The work will be extended using a high resolution numerical model of the North Atlantic with an assumed stationary circulation. This will permit analysis of simulated CFC and ideal ages, their distributions, comparison with observations, and assessment of ventilation and mixing in the model. Results from the proposed multiple tracer approach will contribute toward quantifying the rate at which the ocean takes up atmospheric gases, for example, CO2.