Surface waters in high latitudes are closely coupled to the deep ocean through the thermohaline circulation. During the process of convection, atmospheric constituents are introduced into the newly formed deep water. Some of these constituents, CFCs and bomb tritium, are referred to as transient tracers, because of their time varying concentrations in the atmosphere. Transient tracer concentrations, gradients and inventories have proven to be a powerful tool. They tell us which waters have been in contact with the atmosphere in the past few decades, and give information on ocean circulation and its variability on time scales of months to decades. The time scale information is needed to understand and assess the ocean's role in decadal time scale climate, and its capacity to take up anthropogenic constituents from the atmosphere.