Global Annual Mean Atmospheric Histories, Growth Rates and Seawater Solubility Estimations of the Halogenated Compounds HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116

Abstract

Abstract. We present consistent annual mean atmospheric histories and growth rates for the mainly anthropogenic halogenated compounds HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116, all potentially useful oceanic transient tracers (tracers of water transport within the ocean), for the Northern and Southern Hemisphere with the aim of providing input histories for these compounds. Where available we utilize observations of the halogenated compounds made by the Advanced Global Atmospheric Gases Experiment (AGAGE), National Oceanic and Atmospheric Administration (NOAA) and University of East Anglia (UEA). Prior to the direct observational record we estimated the atmospheric history concentrations from other sources such as archived air measurements, firn air measurements and published model calculations. The results show that the atmospheric mole fractions for each species have been increasing since they were initially produced. Recently, their atmospheric growth rates are decreasing for HCFCs (HCFC-22, HCFC-141b and HCFC-142b), increasing for HFCs (HFC-134a, HFC-125, HFC-23), and stable with small fluctuation for PFCs (PFC-14 and PFC-116). The atmospheric histories (source functions) and natural background values show that HCFCs (HCFC-22, HCFC-141b and HCFC-142b) and HFCs (HFC-134a, HFC-125 and HFC-23) have the potential to be oceanic transient tracers for the next few decades only because of the recently imposed bans on production. When the atmospheric histories of the compounds are not monotonically changing, the equilibrium atmospheric concentrations (and ultimately the age associated with that concentration) calculated from their concentration in the ocean are not unique, reducing the potential as transient tracer. Moreover, HFCs have potential to be oceanic transient tracers for a longer period in the future than HCFCs as the growth rates of HFCs are increasing and those of HCFCs are decreasing in the background atmosphere. PFC-14 and PFC-116, however, have the potential to be the tracers for longer period in the future thanks to their extremely long lifetimes, steady atmospheric growth rates and no explicit ban. In this work, we also derive solubility functions for HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116 in seawater to facilitate the use as oceanic transient tracers. These functions are based on the Clark-Glew-Weiss (CGW) water solubility functions fit and salting-out coefficients estimated by the poly-parameter linear free energy relationships (pp-LFERs). Here we also provide three methods of seawater solubility estimation for more compounds.